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  • Springer  (98)
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  • 1
    Electronic Resource
    Electronic Resource
    Interfacing geometric model data with rapid prototyping systems (1999)
    Springer
    Journal of intelligent manufacturing 10 (1999), S. 323-329 
    Details
    ISSN: 1572-8145
    Keywords: Computer-aided design ; rapid prototyping ; modeling ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The direct slicing of CAD models created in CADDS V to generate geometric data for rapid prototyping using fused feposition modeling technique (FDM) is presented in this paper. The report file from an explicit model is accessed for obtaining model data. Algorithms have been developed for determining the volumes of model material as well as support materials. New algorithms have been developed for filling the sheet solid. A simulation module has been developed to verify whether the filling is correctly done. Example of a model is manufactured using this approach is also presented in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008968428593
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  • 2
    Electronic Resource
    Electronic Resource
    Intelligent scheduling and control of rail-guided vehicles and load/unload operations in a flexible manufacturing system (1999)
    Springer
    Journal of intelligent manufacturing 10 (1999), S. 405-421 
    Details
    ISSN: 1572-8145
    Keywords: Flexible manufacturing systems control ; intelligent manufacturing ; neural networks ; simulation ; material handling systems ; automated guided vehicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a framework of intelligent manufacturing scheduling and control with specific applications to operations of rail-guided vehicle systems (RGVS). A RGVS control architecture is discussed with a focus on a simulated experiment in operations of the load/unload area of a real industrial flexible manufacturing system (FMS). In the operation stage of a material handling system (MHS), all shop floor data are subject to change as time goes. These data can be collected using a data acquisition device and stored in a dynamic database. The RGVS simulator used in this experimental study is designed to incorporate some possible situations representing existing material handling scenarios in order to evaluate alternative control policies. At the development stage of the controller, all possible combinations of most commonly encountered scenarios such as RGV failures, production schedule changes, machine breakdowns, and rush orders are to be simulated and corresponding results collected. The data are then structured into training data pairs to properly train an artificial neural network. The neural network, trained by using input/output data sets obtained from a number of simulation runs, will then provide control strategy recommendations. At the application stage, whenever an abnormal scenario occurs, a pre-processor will be activated to pre-screen and prepare an input vector for the trained neural network. If such an abnormal scenario falls outside the existing domain of data sets employed to train the neural network, as judged by the MHS supervisory controller, an off-line training module will be activated to eventually update the neural network. The recommended control strategies will be transmitted to the MHS control for real-time execution. If there is no further abnormal event detected, the dynamic data base (DDB) module simply continues to monitor the MHS activities. The proposed MHS control system combines the features of example based neural network technology and simulation modeling for true intelligent, on-line, pseudo real-time control. Not only will the system assure that feasible material handling control actions be taken, but also it will implement better control decisions through continuous learning from experiences captured as the operation time of the MHS accumulates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008919013557
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  • 3
    Electronic Resource
    Electronic Resource
    A neural network approach to characterize pattern parameters in process control charts (1999)
    Springer
    Journal of intelligent manufacturing 10 (1999), S. 449-462 
    Details
    ISSN: 1572-8145
    Keywords: Control chart ; pattern recognition ; neural network ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Abnormal patterns on manufacturing process control charts can reveal potential quality problems due to assignable causes at an early stage, helping to prevent defects and improve quality performance. In recent years, neural networks have been applied to the pattern recognition task for control charts. The emphasis has been on pattern detection and identification rather than more detailed pattern parameter information, such as shift magnitude, trend slope, etc., which is vital for effective assignable cause analysis. Moreover, the identification of concurrent patterns (where two or more patterns exist together) which are commonly encountered in practical manufacturing processes has not been reported. This paper proposes a neural network-based approach to recognize typical abnormal patterns and in addition to accurately identify key parameters of the specific patterns involved. Both single and concurrent patterns can be characterized using this approach. A sequential pattern analysis (SPA) design was adopted to tackle complexity and prevent interference between pattern categories. The performance of the model has been evaluated using a simulation approach, and numerical and graphical results are presented which demonstrate that the approach performs effectively in control chart pattern recognition and accurately identifies the key parameters of the recognized pattern(s) in both single and concurrent pattern circumstances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008975131304
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  • 4
    Electronic Resource
    Electronic Resource
    Application of the artificial memory approach to multicriteria scheduling problems (1993)
    Springer
    Journal of intelligent manufacturing 4 (1993), S. 151-161 
    Details
    ISSN: 1572-8145
    Keywords: artificial memory ; simulation ; data analysis ; job-shop scheduling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper is devoted to the development of a knowledge-based system (KBS) called ‘Artificial Memory’, The goal of this KBS is to ‘solve’ multicriteria job-shop scheduling problems. Since job-shop scheduling problems are NP-hard, it is extremely difficult to obtain optimal solutions for industrial problems. Thus, a host of heuristic algorithms, most of which are based on priority rules, have been proposed in the literature. The efficiency of these algorithms strongly depends on the criteria to be optimized as well as the values of the parameters associated with the particular instance of the scheduling problem. The basic hypothesis of the artificial memory approach is a continuity assumption: we assume that identical decisions applied to similar instances lead to similar values of the criteria. This assumption is fundamental to validate this knowledge-based system. For each criterion, the artificial memory contains a synthesis of the performances of different algorithms upon sets of ‘similar’ instances. These performances are acquired using simulation. When the artificial memory is employed, the characteristic values of a new instance are computed and examined by the artificial memory system. The performances of the different algorithms for the considered criterion are estimated for the new instance and an appropriate algorithm is chosen accordingly. In order to build this KBS and to estimate the performances of algorithms upon a new instance, we use a mathematical approach. Some difficulties arose in the development of this KBS and had to be overcome: the corresponding proposed solutions are developed. The paper also presents a number of numerical experimental applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00123908
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  • 5
    Electronic Resource
    Electronic Resource
    Chemiluminescence in evaluating the thermal oxidative stability of acrylonitrile-butadiene-styrene (ABS) copolymers. II. ABS/polycarbonate (PC) blends (1993)
    Springer
    Journal of polymers and the environment 1 (1993), S. 275-279 
    Details
    ISSN: 1572-8900
    Keywords: Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene (ABS) ; ABS/polycarbonate blend
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The thermal oxidative stability of various ABS/PC compounds was studied by means of the chemiluminescence technique. Similarly to pure ABS, Irganox 1076 and Irganox MD 1024 perform as moderate antioxidants in ABS/PC and (ABS/PC + lubricant) blends. Neither Tinuvin 144, Irgaphos 168, nor their mixture affects the durability of the ABS/PC blend. At the same time, (Irgaphos 168 + Tinuvin 144) in combination with Irganoxes was found to provide a noticeable enhancement in durability to the (ABS/PC + lubricant) system. Titanium dioxide pigments by themselves have only a slight influence on the oxidative stability of the ABS/PC blend. Durability of the (ABS/PC + pigment) and (ABS/PC + lubricant) systems was found to be the same and the overall protective effect of Irganox 1076 was similar in both the (ABS/PC + lubricant) and the (ABS/PC + lubricant + pigment) systems. Certain modifiers significantly improve the durability of the ABS/PC compounds, although their function may differ in the systems with and without pigments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01458294
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  • 6
    Electronic Resource
    Electronic Resource
    Chemiluminescence in evaluating the thermal oxidative stability of acrylonitrile-butadiene-styrene (ABS) copolymers. 1. Influence of stabilizers and lubricants (1993)
    Springer
    Journal of polymers and the environment 1 (1993), S. 107-110 
    Details
    ISSN: 1572-8900
    Keywords: Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene (ABS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of lubricants, UV stabilizers, antioxidants, and metal deactivators on the resistance of ABS to thermal oxidation was studied by means of the chemiluminescence technique. Neither of the additives seems to affect significantly the induction period of oxidation. At the same time, the influence of various additives on the oxidation rate constant is remarkably different: the introduction of lubricants and UV stabilizers increases its value, while antioxidants and metal deactivators have the opposite effect. For the particular systems studied durability is decreased in samples containing the lubricant and UV stabilizers and increased in samples stabilized with the antioxidant and metal deactivator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01418203
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  • 7
    Electronic Resource
    Electronic Resource
    Developing manufacturing control software: A survey and critique (1993)
    Springer
    International journal of flexible manufacturing systems 5 (1993), S. 53-88 
    Details
    ISSN: 1572-9370
    Keywords: manufacturing control software ; software methodologies ; planning ; scheduling ; monitoring ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The complexity and diversity of manufacturing software and the need to adapt this software to the frequent changes in the production requirements necessitate the use of a systematic approach to developing this software. The software life-cycle model (Royce, 1970) that consists of specifying the requirements of a software system, designing, implementing, testing, and evolving this software can be followed when developing large portions of manufacturing software. However, the presence of hardware devices in these systems and the high costs of acquiring and operating hardware devices further complicate the manufacturing software development process and require that the functionality of this software be extended to incorporate simulation and prototyping. This paper reviews recent methods for planning, scheduling, simulating, and monitoring the operation of manufacturing systems. A synopsis of the approaches to designing and implementing the real-time control software of these systems is presented. It is concluded that current methodologies support, in a very restricted sense, these planning, scheduling, and monitoring activities, and that enhanced performance can be achieved via an integrated approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01328739
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  • 8
    Electronic Resource
    Electronic Resource
    Experimental investigation of an FMS due-date scheduling problem: Evaluation of machine and AGV scheduling rules (1993)
    Springer
    International journal of flexible manufacturing systems 5 (1993), S. 301-323 
    Details
    ISSN: 1572-9370
    Keywords: flexible manufacturing systems ; automated guided vehicles ; scheduling ; dispatching ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Although extensive research has been conducted to solve design and operational problems of automated manufacturing systems, many of the problems still remain unsolved. This article investigates the scheduling problems of flexible manufacturing systems (FMSs). Specifically, the relative performances of machine and automated guided vehicle (AGV) scheduling rules are analyzed against various due-date criteria. First, the relevant literature is briefly reviewed, and then the rules are tested under different experimental conditions by using a simulation model of an FMS. The sensitivity to AGV workload, buffer capacity, and processing-time distribution is also investigated to assess the robustness of the scheduling rules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01325033
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  • 9
    Electronic Resource
    Electronic Resource
    The Effects of Scheduling Rules and Routing Flexibility on the Performance of a Random Flexible Manufacturing System (1999)
    Springer
    International journal of flexible manufacturing systems 11 (1999), S. 271-289 
    Details
    ISSN: 1572-9370
    Keywords: random flexible manufacturing systems ; scheduling ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The increased use of flexible manufacturing systems to efficiently provide customers with diversified products has created a significant set of operational challenges for managers. Many issues concerning procedures and policies for the day-to-day operation of these systems still are unresolved. Previous studies in this area have concentrated on various problems by isolating or simplifying the systems under study. The primary objective of this study is to extend previous research by examining the effects of scheduling rules and routing flexibility on the performance of a constrained, random flexible manufacturing system (FMS). Other experimental factors considered are shop load, shop configuration, and system breakdowns. Within the bounds of this experiment, the results indicate that, in the presence of total routing flexibility, the effects of shop load, system breakdowns, and scheduling rules are significantly dampened. In particular, when total routing flexibility exists, the choice of scheduling rules is not critical. We also show that the behavior of scheduling rules in a more constrained FMS environment (i.e., where system breakdowns occur and material handling capability is limited) is consistent with the findings of previous research conducted under less constrained environments. Finally, results indicate that the shop configuration factor has little or no impact on a system's flow-time performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008165212489
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  • 10
    Electronic Resource
    Electronic Resource
    Friendship Networks Through Time: An Actor-Oriented Dynamic Statistical Network Model (1999)
    Springer
    Computational & mathematical organization theory 5 (1999), S. 167-192 
    Details
    ISSN: 1572-9346
    Keywords: rational choice ; friendship ; Markov processes ; random utility models ; simulation ; empirical test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We propose a class of actor-oriented statistical models for closed social networks in general, and friendship networks in particular. The models are random utility models developed within a rational choice framework. Based on social psychological and sociological theories about friendship, mathematical functions capturing expected utility of individual actors with respect to friendship are constructed. Expected utility also contains a random (unexplained) component. We assume that, given their restrictions and contact opportunities, individuals evaluate their utility functions and behave such that they maximize the expected amount of utility. The behavior under consideration is the expression of like and dislike (choice of friends). Theoretical mechanisms that are modelled are, e.g., the principle of diminishing returns, the tendency towards reciprocated choices, and the preference for friendship relations with similar others. Constraints imposed on individuals are, e.g., the structure of the existing network, and the distribution of personal characteristics over the respondents. The models are illustrated by means of a data-set collected among university freshmen at 7 points in time during 1994 and 1995.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009683123448
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  • 11
    Electronic Resource
    Electronic Resource
    A Simulation Study of an Object-Oriented Integration Testbed for Process Planning and Production Scheduling (1999)
    Springer
    International journal of flexible manufacturing systems 11 (1999), S. 19-35 
    Details
    ISSN: 1572-9370
    Keywords: integration ; process planning ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Many studies on integration of process planning and production scheduling have been carried out during the last decade. While various integration approaches and algorithms have been proposed, the implementation of these approaches is still a difficult issue. To achieve successful implementation, it is important to examine and evaluate integration approaches or algorithms beforehand. Based on an object-oriented integration testbed, a simulation study that compares different integration algorithms is presented in this paper. Separated planning method and integrated planning methods are examined. Also, situations of both fixed and variable processing times are simulated, and useful results have been observed. The successful simulation with the object-oriented integration testbed eventually will be extended to include other new planning algorithms for examining their effectiveness and implementation feasibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008040622456
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  • 12
    Electronic Resource
    Electronic Resource
    Infinitesimal perturbation analysis for queueing networks with general service time distributions (1999)
    Springer
    Queueing systems 31 (1999), S. 43-58 
    Details
    ISSN: 1572-9443
    Keywords: perturbation analysis ; sample path analysis ; queueing theory ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We study infinitesimal perturbation analysis (IPA) for queueing networks with general service time distributions. By “general” we mean that the distributions may have discrete components. We show that in the presence of service time distributions with discrete components commuting condition (CC) is no longer sufficient for unbiasedness of IPA. To overcome this difficulty, we introduce the notion of separability of real‐valued random variables, and show that separability of service times together with (CC) establishes unbiasedness of IPA for queueing systems with general service time distributions. It turns out that the piecewise analyticity of service times is a sufficient condition for separability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019193711052
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  • 13
    Electronic Resource
    Electronic Resource
    Smoothed perturbation analysis for queues with finite buffers (1993)
    Springer
    Queueing systems 14 (1993), S. 57-78 
    Details
    ISSN: 1572-9443
    Keywords: Perturbation analysis ; sample path analysis ; finite buffer queues ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Applying the technique of smoothed perturbation analysis (SPA) to theGI/G/1/K queue, we derive gradient estimators for two performance measures: the mean steady-state system time of a served customer and the probability that an arriving customer is rejected. Unbiasedness of the estimators follows from results of a previous general framework on SPA estimators. However, in that framework, the estimators often require the simulation of numerous additional sample subpaths, possibly making the technique practically infeasible in applications. We exploit some of the special structure of theGI/G/1/K queue to come up with an estimator which requires at most the simulation of a single additional sample subpath. By establishing certain regenerative properties, we provide a strong consistency proof for the estimator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01153526
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  • 14
    Electronic Resource
    Electronic Resource
    Multivariate Geometric Stable Laws (1999)
    Springer
    Journal of computational analysis and applications 1 (1999), S. 349-385 
    Details
    ISSN: 1572-9206
    Keywords: Estimation ; geometric compound ; heavy-tail modeling ; Linnik distribution ; Mittag–Leffler law ; mixture ; multivariate Laplace distribution ; random summation ; simulation ; subordination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The paper discusses recent advances in the theory of multivariate geometric stable (GS) distributions. The results presented include characterizations, mixture representations, properties, simulation, and estimation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022692806500
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  • 15
    Electronic Resource
    Electronic Resource
    Estimation variances for estimators of product densities and pair correlation functions of planar point processes (1993)
    Springer
    Annals of the Institute of Statistical Mathematics 45 (1993), S. 211-221 
    Details
    ISSN: 1572-9052
    Keywords: Approximation ; estimation variance ; pair correlation function ; Poisson process ; product density ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Approximations of the estimation variances of kernel estimators of the pair correlation function and the product density of a planar Poisson process are given. Furthermore, a heuristic approximation of the estimation variance of an estimator of the pair correlation function of a “general” planar point process is suggested. All formulae have been tested by simulation experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00775808
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  • 16
    Electronic Resource
    Electronic Resource
    The Cross-Entropy Method for Combinatorial and Continuous Optimization (1999)
    Springer
    Methodology and computing in applied probability 1 (1999), S. 127-190 
    Details
    ISSN: 1387-5841
    Keywords: combinatorial optimization ; global optimization ; importance sampling ; markov chain monte carlo ; simulated annealing ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We present a new and fast method, called the cross-entropy method, for finding the optimal solution of combinatorial and continuous nonconvex optimization problems with convex bounded domains. To find the optimal solution we solve a sequence of simple auxiliary smooth optimization problems based on Kullback-Leibler cross-entropy, importance sampling, Markov chain and Boltzmann distribution. We use importance sampling as an important ingredient for adaptive adjustment of the temperature in the Boltzmann distribution and use Kullback-Leibler cross-entropy to find the optimal solution. In fact, we use the mode of a unimodal importance sampling distribution, like the mode of beta distribution, as an estimate of the optimal solution for continuous optimization and Markov chains approach for combinatorial optimization. In the later case we show almost surely convergence of our algorithm to the optimal solution. Supporting numerical results for both continuous and combinatorial optimization problems are given as well. Our empirical studies suggest that the cross-entropy method has polynomial in the size of the problem running time complexity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010091220143
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  • 17
    Electronic Resource
    Electronic Resource
    Buffer management based on return on consumption in a multi-query environment (1993)
    Springer
    The VLDB journal 2 (1993), S. 1-37 
    Details
    ISSN: 0949-877X
    Keywords: Buffer management ; query optimization ; simulated annealing ; join methods ; queueing model ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In a multi-query environment, the marginal utilities of allocating additional buffer to the various queries can be vastly different. The conventional approach examines each query in isolation to determine the optimal access plan and the corresponding locality set. This can lead to performance that is far from optimal. As each query can have different access plans with dissimilar locality sets and sensitivities to memory requirement, we employ the concepts of memory consumption and return on consumption (ROC) as the basis for memory allocations. Memory consumption of a query is its space-time product, while ROC is a measure of the effectiveness of response-time reduction through additional memory consumption. A global optimization strategy using simulated annealing is developed, which minimizes the average response over all queries under the constraint that the total memory consumption rate has to be less than the buffer size. It selects the optimal join method and memory allocation for all query types simultaneously. By analyzing the way the optimal strategy makes memory allocations, a heuristic threshold strategy is then proposed. The threshold strategy is based on the concept of ROC. As the memory consumption rate by all queries is limited by the buffer size, the strategy tries to allocate the memory so as to make sure that a certain level of ROC is achieved. A simulation model is developed to demonstrate that the heuristic strategy yields performance that is very close to the optimal strategy and is far superior to the conventional allocation strategy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01231797
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  • 18
    Electronic Resource
    Electronic Resource
    Intelligent control system simulation of an agricultural robot (1993)
    Springer
    Journal of intelligent and robotic systems 8 (1993), S. 267-284 
    Details
    ISSN: 1573-0409
    Keywords: Intelligent control ; simulation ; agriculture ; robotics ; melon harvesting ; intelligent systems ; planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An intelligent control system for an agricultural robot which performs in an uncertain and unstructured environment was modelled as distributed, autonomous computing modules that communicate through globally accessible blackboard structures. The control architecture was implemented for a robotic harvester of melons. A CAD workstation was used to plan, model, simulate and evaluate the robot and gripper motions using 3-D, real-time animation. The intelligent control structure was verified by simulating the dynamic data flow scenarios of melon harvesting. Control algorithms were evaluated on measured melon locations. Picking time was reduced by 49% by applying the traveling salesman algorithm to define the picking sequence. Picking speeds can be increased by a continuous mode of operation. However, this decreases harvest efficiency. Therefore, an algorithm was developed to attain 100% harvest efficiency by varying the vehicle's forward speed. By comparing different motion control algorithms through animated visual simulation, the best was selected and thereby the performance improved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01257998
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  • 19
    Electronic Resource
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    Coordination and Control of Multi-fingered Robot Hands with Rolling and Sliding Contacts (1999)
    Springer
    Journal of intelligent and robotic systems 24 (1999), S. 125-149 
    Details
    ISSN: 1573-0409
    Keywords: planning ; control ; multi-fingered robot hand ; optimization ; internal force ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper, the problem of controlling multi-fingered robot hands with rolling and sliding contacts is addressed. Several issues are explored. These issues involve the kinematic analysis and modeling, the dynamic analysis and control, and the coordination of a multi-fingered robot hand system. Based on a hand-object system in which the contacts are allowed to both roll and slide, a kinematic model is derived and analyzed. Also, the dynamic model of the hand-object system with relative motion contacts is studied. A control law is proposed to guarantee the asymptotic tracking of the object trajectory together with the desired rolling and/or sliding motions along the surface of the object. A planning approach is then introduced to minimize the contact forces so that the desired motion of the object and the relative motions between the fingers and the object can be achieved. Simulation results which support the theoretical development are presented.
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    URL: http://dx.doi.org/10.1023/A:1008097528538
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  • 20
    Electronic Resource
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    Excimer ArF/XeF lasers providing high-power stimulated radiation in Ar/Xe and F lines (1977)
    Springer
    Applied physics 14 (1977), S. 231-233 
    Details
    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Lasing in atomic lines of noble gases and fluorine, prior to excimer radiation, was observed in an electric discharge ArF/XeF excimer laser. Some Ar/Xe lines end at metastable levels, which are very important for the formation of ArF/XeF excimer molecules. Five new lasing lines of atomic fluorine have been obtained. Consideration is given to the use of lasing in atomic and molecular lines, that occurs in one burst, in investigations of the excitation kinetics of excimer states under the conditions of a high-pressure electric discharge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00883096
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    Properties and current-voltage characteristics of discharges in waveguide gas lasers (1977)
    Springer
    Applied physics 14 (1977), S. 277-282 
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    ISSN: 1432-0630
    Keywords: 42.55 ; 52
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The paper deals with the properties andI-V characteristics of discharges in narrow capillaries used, for example, for He−Ne waveguide lasers. It has been observed that discharges in He−Ne waveguide lasers are unstable because of the strongly falling characteristic. A theory is presented which assumes that at low currents wall charges restrict the positive column to a narrow plasma channel and are the main reason for the observed falling characteristic. A numerical evaluation for helium gives results which agree well with experimental data.
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    URL: http://dx.doi.org/10.1007/BF00882732
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    Continuous laser oscillation in diatomic molecular sodium (1977)
    Springer
    Applied physics 13 (1977), S. 97-99 
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    ISSN: 1432-0630
    Keywords: 42.55 ; 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract First cw laser oscillation with thresholds below 1 mW was observed for various B1Пu → X1 ∑ g + transitions of diatomic molecular sodium excited by different argon laser lines in the range of 454–488 nm. For pump powers of 0.5 W output powers up to 3 mW and single-pass gain up to 0.1 cm−1 were obtained. Some properties of the heat pipe laser system are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890727
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    Optically pumped FIR-laser with variable Fabry-Perot output coupler (1977)
    Springer
    Applied physics 13 (1977), S. 383-385 
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    ISSN: 1432-0630
    Keywords: 42.55 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An optically pumped FIR laser was operated with a copper mesh Fabr-Perot output coupler. With this device a Gaussian output beam was obtained andthe degree of coupling could be varied continuously, thus allowing optimum coupling. From the measured properties of the wire mesches grains of two FIR laser lines are calculated and the saturation intensities estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00882614
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    A magnetic tuning system for dye lasers (1977)
    Springer
    Applied physics 14 (1977), S. 25-28 
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    ISSN: 1432-0630
    Keywords: 42.55 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A new device for magnetically displacing the output mirror of a laser resonator and synchronously tilting an etalon in order to obtain single-mode tuning of a dye laser over a tuning range of at least 10 GHz is described. Comparatively large displacements with good linearity of a coil mounted on a membrane and placed inside the strong magnetic field of a ring magnet are obtained for currents in the order of several hundred milliamperes. Together with etalon flats of appropriate thickness and reflection mounted in the resonator of the laser a versatile instrument for application in intra and extra cavity spectroscopy has been developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00882629
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    Measurements of some reaction rates of importance in KrF lasers (1977)
    Springer
    Applied physics 14 (1977), S. 393-398 
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    ISSN: 1432-0630
    Keywords: 34 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A flowing afterglow method has been used to study a number of reactions of importance in KrF lasers using NF3 as the fluorine donor. Total rate constants are reported for Kr*(3 P 2)+NF3 and Kr++NF3. The thermal energy attachment coefficient has been measured for NF3 and the cross section for the electron excitation process Kr*(3 P 2) +e→Kr*(3 P 1)+e has been estimated. The relevance of these results to discharge pumped KrF lasers is discussed.
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    URL: http://dx.doi.org/10.1007/BF00883445
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  • 26
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    Argon laser with wall stabilized transverse discharge (1977)
    Springer
    Applied physics 14 (1977), S. 193-197 
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    ISSN: 1432-0630
    Keywords: 42.55 ; 52
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Planar and cylindrical discharges for argon lasers are compared by plasmatheoretical calculations. The maximum laser output power available in the two arrangements is computed in dependence of various parameters neglecting saturation mechanisms. A transverse discharge arrangement confining the positive column by two parallel walls is described and experimental laser threshold values for the current and pressure are reported.
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    URL: http://dx.doi.org/10.1007/BF00883089
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    Modulation behavior of semiconductor injection lasers (1977)
    Springer
    Applied physics 14 (1977), S. 255-268 
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    ISSN: 1432-0630
    Keywords: 42.80 ; 42.55 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract GaAs double heterostructure semiconductor injection lasers which now exhibit more than 25000 h cw room temperature lifetime are of great interest for future use as directly modulated transmitters for high bit-rate fiber optical communications. The effects limiting this application are modulation distortions, spectral width and additional spectral broadening in the case of modulation and spontaneous fluctuations of the output power. The dynamic and spectral behavior of injection lasers, the methods of high bit-rate modulation and the improvement of the high bit-rate modulation capability by coupling two lasers are discussed.
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    URL: http://dx.doi.org/10.1007/BF00882730
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    A simple and reliable short-pulse dye laser (1977)
    Springer
    Applied physics 13 (1977), S. 109-110 
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    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A simple technique is described that allows the generation of a short pulses (1 ns) from dye lasers pumped by a much longer (7 ns) N2-laser pulse. Dye-laser pulses, either with a narrow bandwidth or a short duration, can thus be obtained with the same N2-laser pump.
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    URL: http://dx.doi.org/10.1007/BF00890731
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  • 29
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    Tunable laser via F 2 + and F 2 − colour centers in the spectral region 0.88–1.25 μm (1977)
    Springer
    Applied physics 14 (1977), S. 121-122 
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    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Frequency-tunable generation by means of F 2 + and F 2 − colour centers in a LiF crystal is reported. Colour centers were created by illuminating LiF crystals with electrons of 3 meV energy at the electron current density of 1 μA/cm2. The pumping source was a ruby laser with a peak power of 20 MW, a pulse duration of 20 ns, and a repetition rate of 1 Hz. The frequency tuning is obtained in the range of 0.88–1.25 μm. Discussed are the ways of pumping of colour centers and the possibility of lasing in the spectral region of 0.85 to 2 μm in the type of colour centers under investigation.
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    URL: http://dx.doi.org/10.1007/BF00882641
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    Excimer gas-discharge tunable ArF laser (1977)
    Springer
    Applied physics 13 (1977), S. 107-108 
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    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Intense laser oscillation has been observed from ArF molecules at 1933 Å. Excitation of the gas mixture NF3:Ar:He=1:55:630 at total pressures above 2.1 atm was produced by a transverse electric discharge. The range of fine tuning was from 1927 Å to 1936 Å. An output energy of 0.8 mJ was measured from a laser pulse 15 ns in duration.
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    Reaction kinetics of excimer lasers using NF3 (1977)
    Springer
    Applied physics 13 (1977), S. 1-3 
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    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Disappearance of NF3 and appearance of NF2 and N2F2 in an excimer laser is followed quantitatively with a mass spectrometer. A model for the kinetics is presented.
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    URL: http://dx.doi.org/10.1007/BF00890711
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    Performance of NdLa pentaphosphate laser pumped by nanosecond pulses (1977)
    Springer
    Applied physics 13 (1977), S. 55-58 
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    ISSN: 1432-0630
    Keywords: 42.55 ; 78.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract NdxLa1−xP5O14 (0.25≦x≦1) single crystals, placed within a confocal optical resonator, were pumped with ruby laser fundamental and second-harmonic nanosecond pulses. In both cases laser oscillations at 1.05 μm exceeding in duration many times the pumping pulse were obtained.
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    URL: http://dx.doi.org/10.1007/BF00890721
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    Nonlinear absorption spectroscopy of the ethane molecule (1977)
    Springer
    Applied physics 14 (1977), S. 343-350 
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    ISSN: 1432-0630
    Keywords: 33 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By means of nonlinear absorption spectroscopy data necessary for the interpretation of molecular spectra can be obtained in such spectral regions, where conventional spectroscopic methods yield only a quasi-continuous absorption curve. Using a Zeeman-tuned He−Ne laser at the wavelength of 3.39μm we have measured significant differences in the intensity and temperature behaviour for several ethane absorption lines, the analysis of which made possible a preliminary qualitative assignment of these lines.
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    A high-power single-mode cw dye ring laser (1977)
    Springer
    Applied physics 14 (1977), S. 377-380 
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    ISSN: 1432-0630
    Keywords: 42.55 ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Due to spatial hole burning, standing-wave dye lasers require a large amount of selectivity inside the cavity for single-mode operation. The output power of these lasers is limited by losses caused by the frequency selecting elements. In a travelling-wave laser, on the other hand, spatial hole burning does not exist, thereby eliminating the need for high selectivity. A travelling-wave cw dye laser was realized by unidirectional operation of a ring laser, yielding single mode output powers of 1.2 W at 595 nm and of 55 mW in the UV-region with intracavity frequency doubling.
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    URL: http://dx.doi.org/10.1007/BF00883442
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    Effect of laser dye deterioration on performance (1977)
    Springer
    Applied physics 14 (1977), S. 199-203 
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    ISSN: 1432-0630
    Keywords: 42.55 ; 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Loss of gain in a dye medium as a result of decomposition by pump photons is considered in terms of disappearance of dye molecules and the appearance of a new, single chemical product having absorption in the fluorescence band. The cases of small signal gain and saturated gain are applied to a single pass through a transversely excited amplifier. Loss of output, defined as “quantum yield of laser deterioration”,Q L , is related to the true quantum yield of molecular destruction of the dye,Q M , and other known parameters. For the experimentally common, saturated gain condition, the smallestQ L can be isQ M , which requires a photochemically bleachable dye with high gain, preferably at high concentration, in a long cavity, operating at high injection and pumping fluxes. Reversing these conditions, the highest valueQ L can be, compared withQ M , is unrestricted.
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    Engineering Aspects of Preparation of Nanocrystalline Particles in Microemulsions (1999)
    Springer
    Journal of nanoparticle research 1 (1999), S. 267-276 
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    ISSN: 1572-896X
    Keywords: nanoparticles ; microemulsions ; reaction engineering ; formation model ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Engineering aspects of the preparation of palladium nanoparticles in non-ionic w/o-microemulsions are examined. In order to achieve reproducible synthesis conditions a semi-batch reactor with a standardized design is used. Influences of the stirring rate and of different ways of concentration control on the product properties are observed. For reproducible synthesis it is important to establish appropriate and defined preparation conditions. Monodisperse palladium particles of around 5 nm size are obtained by adding the microemulsion containing the palladium salt at a constant feed rate to the precharged microemulsion containing the reducing agent. A quantitative kinetic model is proposed to describe particle formation in microemulsions. Unknown parameters of the model have been estimated by independent examinations or can be achieved by fitting to the experimental data.
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    URL: http://dx.doi.org/10.1023/A:1010068903324
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    Oxidation of Styrene in a Silent Discharge Plasma (1999)
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    Plasma chemistry and plasma processing 19 (1999), S. 131-151 
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    ISSN: 1572-8986
    Keywords: Styrene ; oxidation ; silent discharge ; plasma ; dielectric barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A silent discharge plasma reactor has been developed to study the oxidation of styrene vapor in argon/oxygen mixtures. A number of analytical techniques were employed to determine the destruction efficiency and to characterize the intermediate products. The destruction efficiency was measured as a function of initial styrene concentration, temperature, and energy density of the plasma. The formation of solid products was observed in most experiments. At low temperature (100°C), the solid deposit was polymeric in nature, while at high temperature (300°C) the solid appeared to be amorphous carbon. A combination of high temperature and high energy density resulted in high destruction efficiency and minimal production of solid films. The destruction efficiency vs. energy density is shown to be more complex than a simple model predicting exponential behavior. Several reasons for the discrepancy are suggested. The “e-folding” energy density for the destruction of styrene is compared to literature values for other organic compounds, measured using similar types of plasma reactors.
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    URL: http://dx.doi.org/10.1023/A:1021812201545
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    Oxidation of Dilute Benzene in an Alumina Hybrid Plasma Reactor at Atmospheric Pressure (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 383-394 
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    ISSN: 1572-8986
    Keywords: Nonthermal plasma ; benzene ; Al2O3 ; BaTiO3 ; oxidation ; absorption ; atmospheric pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The combination of plasma discharge and adsorption was examined for oxidation of dilute benzene in air in a plasma reactor packed with a mixture of BaTiO 3 pellets and porous Al 2 O 3 pellets (i.e., an alumina hybrid reactor). The oxidative decomposition of benzene was enhanced by the benzene concentrating on the Al 2 O 3 pellets. Furthermore, there was a higher selectivity to CO 2 in the products from the hybrid than from a plasma reactor packed with BaTiO 3 pellets alone. The presence of the Al 2 O 3 pellets suppressed the formation of N 2 O.
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    URL: http://dx.doi.org/10.1023/A:1021820403362
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    Oxidation and Reduction Processes During NO x Removal with Corona-Induced Nonthermal Plasma (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 421-443 
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    ISSN: 1572-8986
    Keywords: Streamer corona ; NO x removal ; nonthermal plasma ; oxidation ; reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In this paper, the NO-to-NO 2 conversion in various gaseous mixtures is experimentally investigated. Streamer coronas are produced with a dc-superimposed high-frequency ac power supply (10–60 kHz). According to NO x removal experiments in N 2 +NO x and N 2 +O 2 +NO x gaseous mixtures, it is supposed that the reverse reaction NO 2 +O→NO+O 2 may not only limit NO 2 production in N 2 +NO x mixtures, but also increase the energy cost for NO removal. Oxygen could significantly suppress reduction reactions and enhance oxidation processes. The reduction reactions, such as N+NO→N 2 +O, induce negligible NO removal provided the O 2 concentration is larger than 3.6%. With adding H 2 O into the reactor, the produced NO 2 per unit removed NO can be significantly reduced due to NO 2 oxidation. NH 3 injection could also significantly decrease the produced NO 2 via NH and NH 2 - related reduction reactions. Almost 100% of NO 2 can be removed in gaseous mixtures of N 2 +O 2 +H 2 O+NO 2 with negligible NO production.
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    URL: http://dx.doi.org/10.1023/A:1021824504271
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    Comparisons Between Numerical Model and Experiments for a Direct Current Plasma Flow (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 487-504 
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    ISSN: 1572-8986
    Keywords: Hydrogen plasma ; arcjets ; simulation ; LBI method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The governing equations describing a flowing stream of a hydrogen plasma encountered in applications, such as diamond deposition, and in devices, such as arcjet thrusters, are solved numerically using the linearized implicit (LBI) Method of Briley and McDonald. The results of simulations under the assumption that the plasma can be described by a single temperature are compared with detailed experimental measurements of flow characteristics and species concentrations in a 1 kW arcjet. These comparisons show that by formulating the problem in terms of known experimental operating conditions, such as mass flow rate, power, and current levels, it is possible to predict many of the characteristics of the flowing plasma. As expected, predictions from this one-temperature model show that some deviations from the experimental results occur near the exit plane of the channel, where unequal electron and heavy particle temperatures are encountered because of lower pressures.
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    Characterization of Layered Cylindrical Structures Using Axially Symmetric Waves (1999)
    Springer
    Journal of nondestructive evaluation 18 (1999), S. 117-126 
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    ISSN: 1573-4862
    Keywords: Nondestructive evaluation ; layered cylindrical structures ; cylindrical waves ; simulation ; inverse problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract For the characterization of the unknown material properties of a layered cylindrical structure, axially symmetric wave signals transmitted and reflected by the structure have been used. Since only a single wave mode propagates in the structure, the measurement and analysis of the transmitted and reflected signals can be simplified significantly. The evaluation of the material properties of the layers can be achieved with great accuracy. In this paper, we first derive the transmission and reflection coefficients for the layered cylindrical structure sonified axisymmetrically by an incident cylindrical wave. We then relate the spectra of the transmitted and reflected wave signals to the transmission and reflection coefficients as ratio functions. The time-domain signals transmitted and reflected by the structure can then be reconstructed from a routine application of the Fourier integrals. A three-layered aluminum/epoxy/aluminum tube is used to illustrate the application of the expressions for both the forward and inverse problems. The results show that the technique developed in this study can be used very effectively for the characterization of layered cylindrical structures.
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    URL: http://dx.doi.org/10.1023/A:1022638103852
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    The diffusional growth of a scale with variable composition, diffusivity, and molar volume (1977)
    Springer
    Oxidation of metals 11 (1977), S. 57-62 
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    ISSN: 1573-4889
    Keywords: oxidation ; scale growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Equations are presented to modify the classical theoretical expressions for the parabolic rate constant for the case in which the scale has a large composition range and a large variation in molar volume. The modifications appear as simple averages, together with a factor f.Evaluation of f for some hypothetical cases shows that it is near unity unless the composition gradient has an extreme deviation from linearity.
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    Thickness of the oxide layers formed during the oxidation of iron (1977)
    Springer
    Oxidation of metals 11 (1977), S. 193-198 
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    ISSN: 1573-4889
    Keywords: oxidation ; scaling ; wustite ; magnetite ; iron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The theory of the growth of two oxide layers by Yurek et al. has been applied to the oxidation of iron at 1100° C. The theoretical parabolic rate constants for the simultaneous growth of the two oxide layers were calculated from radioactive tracer diffusion coefficients for wustite and magnetite. Good agreement was found between the theoretical and experimental values of the ratio of scale thicknesses.
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    The oxidation and hot corrosion behavior of tungsten-fiber reinforced composites (1975)
    Springer
    Oxidation of metals 9 (1975), S. 45-67 
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    ISSN: 1573-4889
    Keywords: oxidation ; hot corrosion ; nickel alloys ; composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation and hot corrosion behavior of a tungsten-fiber, reinforced Ni~ 20Cr alloy has been examined under the following exposure conditions: (a) pure oxygen at 1 atm pressure; (b) sulfidation in H2–10 %H2S; (c) presulfidation in H2–10 %H2S followed by oxidation in oxygen; and (d) oxidation in 1 atm oxygen after precoating with approximately 1 mg/cm2 of Na2SO4. Rapid oxidation of the tungsten fibers causes considerable distortion of the matrix and catastrophic degradation of the matrix follows. Inter diffusion between the matrix and the fibers is also important. During sulfidation, only the matrix forms sulfides, the fibers remaining unaffected. Consequently, presulfidation, although having a dramatic effect on the oxidation of the matrix does not have a damaging effect on the fibres. Equally, the presence of sodium sulfate is not critical, although severe oxidation of the exposed tungsten fibers is still observed.
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    The high-temperature oxidation of Ni-20%Cr alloys containing various oxide dispersions (1975)
    Springer
    Oxidation of metals 9 (1975), S. 275-305 
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    ISSN: 1573-4889
    Keywords: oxidation ; Ni-Cr alloys ; rare-earth oxide dispersion ; dispersion-strengthened alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of Ni-20%Cr alloys containing approximately 3 vol.% Y2O3, ThO2, and A12O3 as dispersed particles has been examined in the temperature range 900 to 1200° C in slowly flowing oxygen at 100 Torr. The results show that the oxidation behavior of the Y2O3-, ThO2-, Al2O3-, and Ce02-containing alloys is very similar and that some anomalies in the behavior of the ThO2-containing alloy might be explained by the slower rate of chromium diffusion in this coarse-grained alloy. Two Al2O3-containing alloys were studied. One with a relatively coarse dispersoid size behaved in a manner analogous to a dispersion-free Ni-30% Cr alloy at 1100°C. The other alloy contained a dispersion of fine Al2O3 particles and behaved exactly like the Y2O3-containing alloy at 1000 and 1100°C, but at 1200° C oxidized at a faster rate. It has been shown that the adherent scales on dispersion-containing alloys have a stabilized fine grain size, whereas the nonadherent scales on dispersion-free alloys undergo grain growth.
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    URL: http://dx.doi.org/10.1007/BF00613277
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    Study of the oxidation kinetics of vanadium carbide (1975)
    Springer
    Oxidation of metals 9 (1975), S. 415-425 
    Details
    ISSN: 1573-4889
    Keywords: vanadium carbide ; vanadium oxycarbide ; oxidation ; parabolic rate law ; cubic rate law ; chemisorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of an oxycarbide of vanadium, VO0.6C0.7, and of a vanadium carbide, VC0.98, was studied athermally up to temperatures of 800° C and isothermally between 400 and 580° C at oxygen pressures ranging from 10−2 to 1 atm. The oxycarbide followed the parabolic rate law below 450° C with V2O5 forming as the only reaction product. The activation energy was 49 kcal/mole. VC0.98 did not form an oxide in this temperature range, but rather dissolved oxygen, the activation energy being 26.6 kcal/mole. No oxygen pressure dependence on the kinetics was found for either sample in this temperature range. Both samples followed the cubic rate law during oxidation in the range of 500–580° C during which V2O5 formed. There was a P1/3 dependence and the activation energy was the same for both materials, 51 kcal/mole. The cubic rate law and the positive pressure dependency (rather than an anticipated negative dependency) were attributed to an electric field associated with oxygen ions chemisorbed on a thin layer of V2O5.
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    URL: http://dx.doi.org/10.1007/BF00611690
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    Effect of oxide grain structure on the high-temperature oxidation of Cr (1975)
    Springer
    Oxidation of metals 9 (1975), S. 459-472 
    Details
    ISSN: 1573-4889
    Keywords: Cr ; oxidation ; kinetics ; Cr2O3 grain size ; short-circuit diffusion ; surface ; preparation ; Fe-Cr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cr was oxidized in 1 aim O2 at 980, 1090, and 1200°C. ElectropolishedCr and some orientations of etched Cr oxidize rapidly and develop compressive stress in the growing Cr2O3; other orientations oxidize slowly, apparently free of stress. SEM examination of fracture sections shows that the thick oxide is polycrystalline whereas the thin oxide on etched Cr is monocrystalline. It is deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries. The consequent formation of oxide within the body of the polycrystalline layer generates compressive stress and leads to wrinkling by plastic deformation. The activation energy for oxidation of Cr by cation lattice transport is 58 kcal/mole. Polycrystalline Cr2O3 forms on Fe-26Cr alloy, whether electropolished or etched; oxidation is accordingly rapid and accompanied by compressive stress.
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    URL: http://dx.doi.org/10.1007/BF00611694
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    Behavior of oxide films on high-temperature alloys in carbonaceous gas atmospheres (1977)
    Springer
    Oxidation of metals 11 (1977), S. 23-56 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; carburization ; carbonaceous gases ; superalloys ; stainless steels ; film formation ; structure of oxide scales ; preoxidation ; metal dusting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Formation and deterioration of oxide films on several contemporary high-temperature alloys was studied in various carbonaceous gas atmospheres. Scanning electron microscopy and metallographic examination were applied to films on Fe-Cr-Ni and Ni-Cr-Al type alloy compositions exposed in CH 4/H2 and CO/CO2 atmospheres at temperatures up to 900° C and pressures up to 900 psi (6.2 × 106 N/m2). The effects of various preoxidation treatments were evaluated. Reduction of certain oxide phases is observed to promote catalytic gas decomposition. Al2O3 components in the films are observed to be stable under the reducing conditions experienced. Carbon uptake by various alloys is found to be quite sensitive to surface finish, with an observed increase in penetration with surface roughness.
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    URL: http://dx.doi.org/10.1007/BF00611601
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    Oxidation of tantalum in oxygen-nitrogen and oxygen-inert gas mixtures (1977)
    Springer
    Oxidation of metals 11 (1977), S. 225-239 
    Details
    ISSN: 1573-4889
    Keywords: tantalum ; oxidation ; high temperature ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of tantalum in oxygen-nitrogen and oxygen-inert gas mixtures at925°C has been studied. The oxygen pressure was close to 0.5 atm in all experiments, and partial pressures of the second component of from 0 to 180 Torr were employed. Spherical specimens were used to provide quantitatively significant kinetic data. A model has been proposed which suggests that the oxygen pressure at the reaction interface close to the metal surface is lower than the external pressure because of the finite permeability of the porous outer oxide layer, and that the inert gas effectively reduces the permeability. The model gives good quantitative agreement with the experimental results.
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    URL: http://dx.doi.org/10.1007/BF00606059
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    Further aspects of the oxidation of binary two-phase alloys (1993)
    Springer
    Oxidation of metals 39 (1993), S. 197-209 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; binary alloys ; two-phase alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The corrosion behavior of binary, two-phase alloys is considered in which the matrix contains mostly the less-noble metal that forms a fast-growing oxide, while the second phase is rich in a component that forms a more stable but slowly-growing oxide. It is assumed that the second phase exists as a dispersion of isolated, rod-like particles. It is further assumed that both phases form external films with no internal oxidation. It is shown that the oxidation behavior of this type of alloy depends on both the oxidation time and the size of the second-phase particles. In particular, for short oxidation times and large second-phase particles the matrix will oxidize faster than the dispersed phase, so that the dispersed particles will be only partly corroded or even incorporated into the matrix-oxide scale as unoxidized islands, forming an irregular alloy-scale interface. On the contrary, for long times and small particle sizes the two phases will tend to oxidize at approximately the same rate, leading to the formation of regular alloy-scale interfaces. The time for the transition between the two corrosion regimes depends not only on the ratio between the rate constants for the growth of the two oxides but also on the size of the dispersed-phase particles, smaller sizes producing shorter transition times. Eventually, under favorable conditions the formation of the fast-growing oxide may even stop, leading to the formation of a protective layer of the most-stable oxide.
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    URL: http://dx.doi.org/10.1007/BF00665611
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    The oxidation and decarburizing of Fe-C alloys in air and the influence of relative humidity (1975)
    Springer
    Oxidation of metals 9 (1975), S. 69-97 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; decarburization ; Fe-C alloys ; effect of humidity ; effect of microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Isothermal oxidation treatments were carried out on an Fe-C alloy (0.4 % C): (a) in almost dry air around A1, and also with an Fe-C alloy (0.5% C) and IRSID pure iron; (b) in dry air ( $${\text{P}}_{H_2 O} \simeq 10^{ - 5} $$ nm Hg); (c) in almost dry air(1–2% water vapor) at 700° C; and (d) in moist air (31% water vapor). Theresults are as follows: The rate of oxidation at a temperature below A1depends chiefly on alloy structure, i.e., on thermal history of the sample.The water vapor content of the air strongly influences the scale adherenceas well as the rate of oxidation of the Fe-C alloys below A1, but has virtuallyno effect on the rate of oxidation of pure iron. Under the same conditions, avery light decarburization of metal occurs in air, whereas no decarburizationoccurred in air with 13% water vapor.
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    URL: http://dx.doi.org/10.1007/BF00613495
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    The oxidation behavior of an aligned Co-TaC eutectic alloy (1975)
    Springer
    Oxidation of metals 9 (1975), S. 225-257 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; eutectic alloys ; refractory metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of the directionally aligned eutectic alloy, TaC-Co50B, has been examined between 600 and 1155°C. Parabolic oxidation behavior, isotropic in nature, is found to 800°C. Above 800°C, the oxidation behavior is no longer either parabolic or isotropic. The interaction between the Co matrix alloy and the TaC fibers adjacent to the oxidizing interface is reported as a function of temperature in oxidation.
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    URL: http://dx.doi.org/10.1007/BF00613275
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    Role of kinetic effects on metal partition at the alloy-scale interface during the oxidation of alloys (1975)
    Springer
    Oxidation of metals 9 (1975), S. 215-223 
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    ISSN: 1573-4889
    Keywords: cation diffusion ; oxidation ; metal partition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An alternative mass balance at the alloy-scale interface is proposed for the Wagner theory of binary alloy oxidation. A simple relation between the bulk composition of the alloy and the scale composition at the alloy-scale interface, ξ′, is derived in terms of the transport properties of the scale and the limit of application of the relation defined. There is good agreement between calculated and measured values of ξ′.
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    URL: http://dx.doi.org/10.1007/BF00613274
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    The high-temperature oxidation resistance of Co-Al alloys (1975)
    Springer
    Oxidation of metals 9 (1975), S. 427-440 
    Details
    ISSN: 1573-4889
    Keywords: cobalt ; cobalt-aluminum alloys ; oxidation ; thermal cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Most Ni and Co-base alloys used for high-temperature service rely on the production of a compact, stable Cr2O3 scale for their oxidation resistance. However, as operating temperatures have risen above 900–950° C, the loss of Cr2O3 as the volatile CrO3 has led to an inadequate life span of these alloys, particularly in rapidly flowing, turbulent gas streams. As a result of this, it has been necessary to examine the possibility of using Al2O3 as the protective scale. Al2O3 has a lower growth rate than Cr2O3, it is nonvolatile, and, unlike Cr-containing systems, it is less likely to form compound oxides such as spinels. In this study, the amount of Al which must be present in the Co-Al system to form a continuous layer of Al2O3 in the temperature range 800–1000° C has been determined. The quantity was found to rise from about 7–10 wt. % at 800° C to 10–13 wt. % at 900° C and 13 wt. % at 1000° C. Notice has also been taken of the abilities of the alumina-forming alloys to re-form a protective oxide in the event of spalling, blistering, or any other disruptions of the scale, and some “cyclic-oxidation” checks have been conducted on the Co13Al alloy at 900 and 1000° C.
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    URL: http://dx.doi.org/10.1007/BF00611691
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    The effect of ΔT (oxidizing temperature minus cooling temperature) on oxide spallation (1977)
    Springer
    Oxidation of metals 11 (1977), S. 91-106 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; cyclic ; spallation ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several alloys (one iron base and five nickel base) were cyclically oxidized in a series of tests in which the higher temperature (1100 or 1200° C) of the cycle was fixed at a level to allow ample oxidation in reasonable time and the lower temperature was variable to allow cycle temperature differences (ΔT s ) of up to 1400°C. The alloys oxidized included those which formed simple oxides such as Al2O3 or Cr2O3, as well as those which formed complex scales. Cooling rates were relatively low to minimize thermal shock effects. Each cycle consisted of 1 hr at the higher temperature and 1/2 hr at the lower temperature. Samples were tested up to 370 cycles. The extent of attack was determined by specific weight change which was continuously monitored. For all nickel alloys, as ΔT increased the extent of spallation increased. This effect was attributed to thermal expansion mismatches between the oxide and the nickel substrate. The FeCrAl alloy was not sensitive to ΔTand resisted spalling at ΔT levels to 1400°C. FeCrAl, and the Al2O3 scale which forms on it, have thermal expansion coefficients which are substantially more alike than any of the other oxide-metal combinations tested.
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    URL: http://dx.doi.org/10.1007/BF00612137
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    Adherence behavior of oxide grown in air and synthetic exhaust gas on Fe-Cr-Al alloys containing strong sulfide-forming elements: Ca, Mg, Y, Ce, La, Ti, and Zr (1993)
    Springer
    Oxidation of metals 40 (1993), S. 555-583 
    Details
    ISSN: 1573-4889
    Keywords: Fe-Cr-Al ; oxidation ; air ; exhaust gas ; aluminum oxide ; oxide adherence ; reactive elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This work evaluated the adherence of oxide grown in air and synthetic exhaust gas on Fe-20Cr-5Al alloys containing strong sulfide-forming elements: Ca, Mg, Y, Ce, La, Ti, and Zr. Results support the theory that reactive elements provide good oxide adherence on alumina-forming materials primarily by tying up sulfur as stable Sulfides; however, other influences on adherence were found. Highly volatile elements, such as Ca and Mg, lose their sulfur-controlling ability by diffusing out of the matrix and into the growing oxide scale. Zirconium results in the growth of an extensive network of oxide pegs into the substrate which improves adherence. Titanium segregates to the alumina scale and acts as a sink for S in the matrix. In synthetic exhaust gas (N2+CO2+H2O), local oxide spalling was observed and was shown to be caused by H2O in the atmosphere. The added benefits of Ti and Zr, i.e., forming oxide pegs and sinks for S, improve adherence in this environment.
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    URL: http://dx.doi.org/10.1007/BF00666391
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    Oxidation behavior of monolithic TiN and TiN dispersed in ceramic matrices (1993)
    Springer
    Oxidation of metals 39 (1993), S. 69-91 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; titanium nitride ; ceramic-matrix composites ; rutile ; oxide layers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The mechanism and kinetics of high-temperature (up to 1500°C) oxidation of pressureless-sintered TiN and hot-pressed silicon nitride-TiN, alumina-TiN, aluminum nitride-TiN, and AlON-TiN ceramic composites were studied in air under isothermal and nonisothermal conditions. Analysis of the oxidation products revealed the formation of rutile in the temperature range from 600 to 1000°C. An interaction of TiO2 with the matrix and/or its oxidation products was observed at higher temperatures. The oxidation of TiN-containing composites shows different behavior depending on the temperature. The presence of fine isolated inclusions of TiN (〈30 mass %) in the silicon-nitride matrix does not change the mass gain during oxidation or increases it only slightly, as compared with a TiN-free material. For materials containing a continuous skeleton of TiN (〉30 mass %) a noticeable increase of the oxidation rate was observed.
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    Effects of mode-I stresses on the oxidation and failure mechanisms of Ni-20Cr and Ni-15Cr-8Fe alloys in sulfur dioxide (1993)
    Springer
    Oxidation of metals 39 (1993), S. 155-165 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; sulfidation ; nickel alloys ; stresses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Two alloys, Ni-20Cr and Ni-15Cr-8Fe, as wire specimens, were exposed to sulfur dioxide between 325 and 800°C, with applied external stresses (mode I). Their mechanical properties have been investigated, and the variation of their radius has been precised by conductivity measurements. For the Ni-20Cr alloy, below 550°C, the failure process combines cracking and corrosion: Cr2S3 crystals formed at the tip of the cracks facilitate their propagation. Above 550°C, no barrier effect is observed, and intergranular corrosion takes place. For the Ni-15Cr-8Fe alloy, mode-I stresses bolster intergranular corrosion.
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    High temperature corrosion of Ni-20Cr and Ni-15Cr-8Fe alloys in sulfur dioxide (1993)
    Springer
    Oxidation of metals 39 (1993), S. 211-220 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; sulfidation ; nickel alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Two nickel-base alloys, Ni-20Cr and Ni-15Cr-8Fe, in the form of wire specimens, have been exposed to 100 mbar of sulfur dioxide between 550 and 850°C. For Ni-20Cr, an outer Cr2O3 layer formed only at the beginning of the reaction, but very quickly Ni3S2 grew preferentially at the exterior by outward diffusion of nickel. The reaction rate is regulated by an external interfacial process. A barrier effect was noted near 645°C associated with the formation of NiCr2O4; a new acceleration takes place above 680°C. The external growth of Ni3S2 is attributed to the low radius of curvature of the samples. For Ni-15Cr-8Fe, the reaction mechanism is rather similar, except that no barrier effect occurred. A protective Cr2O3 layer formed above 800°C in both cases.
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    The isothermal-oxidation behavior of several nickel-base single-crystal superalloys with and without coatings (1993)
    Springer
    Oxidation of metals 39 (1993), S. 231-261 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; single-crystal superalloys ; coating ; reactive-element effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several commercial single-crystal superalloys (CMSX-2, CMSX-3, CMSX-4, CMSX-6, SRR 99) and some laboratory versions of one of them (CMSX-4) with various Y-additions were investigated concerning their oxidation resistance in air at temperatures between 800 and 1200°C. The investigations also included two materials (CMSX-6, SRR 99) with an RT-22 coating. Weight change was recorded for times of up to 1000 hr (in some cases up to 1600 hr). Oxidized coatings and substrates were characterized by metallography, SEM, and microprobe analysis. Most of the alloys showed good oxidation resistance up to 1000°C, while there was complete spalling during cooling after oxidation at 1150°C and 1200°C for the uncoated and Y-free alloys. Coated alloys were superior, however the best behavior was shown by a laboratory version of CMSX-4 containing between 10 and 60 ppm Y. Interdiffusion at 1000°C is tolerable for the coated alloys, but there was extremely rapid degradation of the coating by interdiffusion at 1200°C.
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    The oxidation and resistance of tantalum-nitride thin films (1993)
    Springer
    Oxidation of metals 40 (1993), S. 5-20 
    Details
    ISSN: 1573-4889
    Keywords: sheet resistance ; resistivity ; oxidation ; tantalum nitride ; thin films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of reactively-sputtered, tantalum—nitride thin films has been studied between 473 and 773 K in air. Films with thicknesses that correspond to sheet resistances of 43, 75, and 150 Ω/□ were evaluated in this study. X-ray diffraction revealed that the films and the oxidation products were amorphous. The oxidation products were characterized with AES and XPS. The oxidation process was monitored by measuring the change in sheet resistance with time. Sheet resistance measurements were performed with a four-point probe. The oxidation kinetics can be represented by the equation ΔR/R n =k′t. ΔR/R is sheet resistance change in %, t is time, and k′ is the rate constant. The oxidation kinetics, for the thickest film, were parabolic above about 598 K, and approximately quartic below this temperature. The 75 Ω/□ films deviated from parabolic kinetics below 603 K, and approached approximate cubic kinetics at 498 K. However, the data were forced to fit parabolic kinetics with good correlation. For the thinnest film, no deviation from parabolic kinetics was observed. The rate constants obeyed the Arrhenius relation. An activation energy of 147 kJ/mole (1.52eV) was calculated, for the thickest film, during parabolic kinetics. This value is approximately equal to the activation energy obtained during quartic kinetics. A model that explains the deviation from parabolic to quartic oxidation kinetics at lower temperatures is presented. In this model, the change in resistance as a function of time was due to simultaneous change in film resistivity, as a result of oxygen dissolution into the film, and oxide-scale growth. The temperature at which this deviation occurs should be a function of film thickness.
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    Application of a counter-current gaseous diffusion model to the oxidation of hafnium carbide at 1200 to 1530°C (1993)
    Springer
    Oxidation of metals 40 (1993), S. 109-118 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; gaseous diffusion ; hafnium carbide ; hafnia ; porosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A counter-current gaseous diffusion model is presented to describe the oxidation of hafnium carbide between 1200 and 1530°C. The model separates the porous hafnia scale into two gas diffusion regions separated by a flame front, where O 2 and CO react to form CO 2.In the outer region, O 2 and CO 2 counter-diffuse; in the inner region, CO 2 and CO counter-diffuse. The concentration gradients of each gaseous specie in the pores of the hafnia are determined and the rate of oxidation is calculated. A porosity of 2% and a pore radius of 0.01 μm are representative of the values observed in hafnia during the early stages of HfC oxidation. These values lead to predictions of parabolic rate constants that are close to those measured by thermogravimetric analysis. In addition, the predicted and measured parabolic rate constants are shown to have the same dependence upon temperature and oxygen partial pressure.
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    On the mechanism of the oxidation of NiCrAl-base alloys in air and air containing sulphur dioxide (1993)
    Springer
    Oxidation of metals 40 (1993), S. 275-294 
    Details
    ISSN: 1573-4889
    Keywords: single crystal ; superalloy ; oxidation ; microstructure ; grain size ; cast and forged alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Oxidation studies have been carried out on NiCrAl-base alloys in air and air containing 1% sulphur dioxide at 1000°C. The alloys used were in the cast, forged and single-crystalline form. There was considerable difference in the oxidation behavior of the as-cast alloy and that of forged alloy, when the environment contained sulphur dioxide. In the absence of the latter, the behavior of the two alloys was not very different. The oxidation behavior of the single crystals was also very similar to that of the cast and forged alloys, when the atmosphere was oxidizing. A few single-crystalline alloys, however, underwent catastrophic oxidation when about 1% sulphur dioxide gas was present, in a manner similar to that of the cast alloy. Oxidation tests at 1000°C as well as detailed scale analysis indicated that the different microstructure, especially large difference in grain size was probably the main reason for the large difference in their oxidation behavior.
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    Initial oxidation of Cr at 300–730 K in H2 18O/H2 16O/16O2 gas mixtures studiedin situ with18O/SIMS and XPS (1993)
    Springer
    Oxidation of metals 40 (1993), S. 421-432 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; chromium ; water ; oxygen ; SIMS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The initial oxidation of pure, polycrystalline-chromium metal with gas mixtures of oxygen-labeled water, H2 18O, and oxygen,16O2, at temperatures 300–730 K has been studied in situ with secondary ion mass spectrometry, SIMS. The fraction of O in secondary ion species: CrO+, Cr2O+, CrOH+, Cr2OH+, CrOH2 +, and Cr2OH2 + originating from water and oxygen was found. The reaction of water and oxygen in the oxygen/water gas mixture with Cr is then revealed. The dissociation of water in its reaction with Cr in such a gas mixture was analyzed. Oxide growth on cleaned Cr surfaces during the reaction with H2O, O2 and H2O/O2 gas was also studied in situ with X-ray photoelectron spectroscopy, XPS. A correlation between a chemical shift in XPS and the OH content in the oxide is discussed.
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    Kinetics of the oxidation of ilmenite (1975)
    Springer
    Oxidation of metals 9 (1975), S. 99-116 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; kinetics ; ilmenite ; rutile ; pseudobrookite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of ilmenite (FeTiO3) in air and dry oxygen was investigated over the temperature interval 600 to 970°C. Dense platelets of ilmenite crystals as well as powder samples of ilmenite were oxidized. The weight data were recorded employing a thermobalance. The oxidation kinetics of ilmenite platelets were parabolic except for the initial stages during which logarithmic kinetics were observed. For powder samples the logarithmic rate law was followed primarily. The logarithmic rate law was attributed to free penetration of oxygen through cracks and short-circuit paths. The activation energies associated with the logarithmic rate law were nearly one-half of those obtained from parabolic oxidation. The growth morphology of the products of oxidation of ilmenite was observed with a scanning electron microscope. The effect of growth morphology on the kinetics is discussed, and a probable reaction mechanism is suggested for the oxidation of ilmenite.
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    URL: http://dx.doi.org/10.1007/BF00613496
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    The oxidation behavior of dilute Ni-V alloys at 1200°C (1977)
    Springer
    Oxidation of metals 11 (1977), S. 109-125 
    Details
    ISSN: 1573-4889
    Keywords: nickel-vanadium ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of nickel and dilute Ni-V alloys has been studied in flowing oxygen at 1 atm pressure, using various kinetic and electron-optical techniques. The oxidation rate rises progressively as the alloy vanadium content is increased from 0 to 0.8% and then to 1.7%. However, further additions to 4.2% cause only a slight further increase. These increases in oxidation rate are largely controlled by the extent of doping of the NiO, particularly for the two more dilute alloys, although internal oxidation, spinel blocking effects in the oxide, and dissociation of the NiO affect the weight gains to some extent, particularly for the case of the Ni-4.2% V alloy.
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    URL: http://dx.doi.org/10.1007/BF00606398
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    The isothermal oxidation of Co-Cr alloys in 760 Torr oxygen at 1000°C (1977)
    Springer
    Oxidation of metals 11 (1977), S. 163-191 
    Details
    ISSN: 1573-4889
    Keywords: cobalt-chromium ; oxidation ; oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The isothermal oxidation of Co-Cr alloys containing 0–30% Cr in 760 Torr oxygen at 1000° C has been studied kinetically and by appropriate physical techniques. Chromium additions to cobalt increase the parabolic oxidation rate to an almost constant level from 2 to 15% Cr, while further additions to 20–30% Cr decrease the rate. All the alloys produce a virtually pure CoO layer outside a layer containing Co-Cr spinel particles in a Cr3+ -doped CoO matrix. The variation of oxidation rate with alloy chromium content is explained in terms of the complex interplay of doping, blocking of cation transport by voids and spinel particles and short circuiting by transport of dissociative oxygen across these voids and other processes, internal oxidation making a negligible direct contribution to weight gain. Complete spinel layers are never quite developed under the conditions studied, although formation of spinel does slow the oxidation rate. The improved protection eventually obtained at higher chromium levels is produced by the tendency to form a Cr2O3 healing layer.
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    URL: http://dx.doi.org/10.1007/BF00606542
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    Volatilization of oxides during oxidation of some superalloys at 1200°C (1977)
    Springer
    Oxidation of metals 11 (1977), S. 289-305 
    Details
    ISSN: 1573-4889
    Keywords: superalloys ; oxidation ; oxides ; volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Volatilization of oxides during cyclic oxidation of commercial Nichrome, Inconel 750, René 41, Stellite 6B, and GE-1541 was studied at 1200°C in static air. Quantitative analysis of oxide vapor deposits revealed that oxides of tungsten, molybdenum, niobium, manganese, and chromium volatilized preferentially from the oxide scales. Aluminum and silicon were not detected in vapor deposits. For all the alloys except GE-1541 chromium was found to be the main metallic element in the oxide scales.
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    URL: http://dx.doi.org/10.1007/BF00608013
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    Influence of superficial coating of CeO2 on the oxidation behavior of AISI 304 stainless steel (1993)
    Springer
    Oxidation of metals 39 (1993), S. 221-229 
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    ISSN: 1573-4889
    Keywords: non-isothermal ; oxidation ; 304 stainless steel ; superficial coating ; cerium oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of a superficially-applied, cerium-oxide coating on the non-isothermal oxidation behavior of AISI 304 stainless steel in dry air has been investigated. The heating rate employed was 3 K/min up to a final temperature of 1423 K. The reactive oxide coating not only reduced the reaction rate but also facilitated scale adhesion to the alloy substrate. Post-oxidation analyses of the alloy/scale combination using optical microscopy, SEM, EDAX, and XRD provide evidence for a changeover in the mechanism of oxide growth from the scale/gas interface to the alloy/scale interface for the coated steel.
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    URL: http://dx.doi.org/10.1007/BF00665613
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    Mechanical stresses developed in austenitic Fe-Cr-Ni alloys by oxidation in a CO2 atmosphere (1975)
    Springer
    Oxidation of metals 9 (1975), S. 259-274 
    Details
    ISSN: 1573-4889
    Keywords: stress ; oxidation ; austenitic steel ; CO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The stresses developed during oxidation of Fe-Cr-Ni alloys in a CO 2 atmosphere at 600 and 700°C have been estimated by measuring the deflection of thin foil specimens oxidized on one side only. One side of the specimen was protected from oxidation by an Al-Au film which was oxidized prior to the deflection experiment. The character and magnitude of the stresses measured are explained by electron microscope and x-ray measurements. During the initial stage of oxidation, high stresses are formed due to epitaxial growth of the oxide. These stresses are high enough to plastically deform the alloy. As oxidation proceeds, the stress decreases and eventually reaches a “steady-state” value. During this stage, the alteration in composition and molecular volume of the oxide, the formation of carbides, and the growth of whiskers determine the stresses.
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    URL: http://dx.doi.org/10.1007/BF00613276
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    The effect of small amounts of silicon on the oxidation of high-purity Co-25 wt. % Cr at elevated temperatures (1975)
    Springer
    Oxidation of metals 9 (1975), S. 409-413 
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    ISSN: 1573-4889
    Keywords: cobalt ; cobalt-chromium alloys ; silicon ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Some investigators have reported that Co-25 wt.% Cr oxidizes slowly at temperatures in the range 1000–1200°C forming a protective Cr2O3 scale; and this is the normal behavior of cobalt-base superalloys. Others have reported very rapid oxidation, forming a two-layer scale: an outer CoO layer and an inner mixture of Cr2O3 and CoCr2O4 particles in a CoO matrix. This investigation shows that the principal reason for this behavior is the purity of the material; it appears that the rapid mode of oxidation is the intrinsic behavior for high purity material. The most probable impurity to produce the slower mode is silicon, and it is shown that as little as 0.05 wt. % Si is sufficient to change the mode of oxidation provided sufficient oxygen is also present in the alloy: it seems probable therefore that a fine dispersion of SiO2 is responsible.
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    URL: http://dx.doi.org/10.1007/BF00611689
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    Universal Correlation of Nitrogen 1s and Oxygen 1s Photoelectron Binding Energies with Chemical Composition in Nitrogen-Containing Plasma Polymers (1999)
    Springer
    Plasmas and polymers 4 (1999), S. 283-307 
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    ISSN: 1572-8978
    Keywords: Plasma polymers ; oxidation ; XPS ; photoelectron binding energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The incorporation of oxygen into nitrogen-containing plasma deposited polymers was studied by X-ray Photoelectron Spectroscopy (XPS). As the oxygen content of the plasma polymer increased, the binding energy of the N 1s photoelectrons increased. Conversely, the binding energy of the O 1s photoelectrons was inversely proportional to the nitrogen content of the plasma polymer. The data from a large number of samples all obeyed the same “universal” correlations of photoelectron binding energy versus chemical composition. The data were described by the same curve regardless of whether the oxygen was incorporated rapidly into the thin film during plasma deposition or whether the oxygen was added slowly during spontaneous oxidation of the film in air. This implies that the same thermodynamic principles of radical reactions governed the addition of oxygen to the plasma polymer. The shift in the O 1s and N 1s photoelectron binding energies as a function of chemical composition was used to monitor the proximity of nitrogen and oxygen. By contrasting the experimental data with a simple binomial model which described the random addition of oxygen to a lattice containing carbon and nitrogen, we were able to show that oxygen was preferentially added near nitrogen-containing groups in plasma polymers.
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    URL: http://dx.doi.org/10.1023/A:1021831527895
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    On the Tradeoff Between Computational Simplicity and Asymptotic Properties in Multivariate Probit (1999)
    Springer
    Computational economics 13 (1999), S. 93-101 
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    ISSN: 1572-9974
    Keywords: efficiency ; multivariate probit ; quasi maximum likelihood ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Economics
    Notes: Abstract This paper discusses the most efficient estimator among Quasi Maximum Likelihood Estimators using at most two levels of numerical integration, for the multivariate probit model. Simulations show that this estimator is more efficient but not more costly than the second-best alternative. However, its added efficiency depends on the correlation structure.
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    URL: http://dx.doi.org/10.1023/A:1008649923740
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    File evaluation in auxiliary storage (1975)
    Springer
    International journal of parallel programming 4 (1975), S. 197-204 
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    ISSN: 1573-7640
    Keywords: Information retrieval ; hierarchial storage ; throughput time ; storage management ; linear objective function ; exogenous variables ; simulation ; evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper investigates, in detail, the evaluation of files in auxiliary storage. We are seeking an evaluation procedure whereby those files most critical to throughput time minimization are exposed. Such a procedure can then be used by a storage management routine to move data so that throughput time is improved. The linear objective function defined here considers parameters not only for the file under evaluation but also for the jobs that reference the file and the overall system needs. Exogenous variables in the evaluation function make it an attractive tool for managers. This particular evaluation function is incorporated in the Dynamic File Management model and significant time savings have been realized under simulation.
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    URL: http://dx.doi.org/10.1007/BF01007758
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    Alignment Properties in Ordinal Comparison of Discrete Event Dynamic Systems (1999)
    Springer
    Discrete event dynamic systems 9 (1999), S. 261-284 
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    ISSN: 1573-7594
    Keywords: discrete event dynamic systems ; simulation ; communications ; performance analysis ; alignment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In the design and optimization of discrete event dynamic systems, it is often necessary to order alternative designs based on their relative performance, i.e., to rank them from best to worst. In this paper, alignment of observed performance orders with true orders is considered and properties of the alignment are investigated. Spearman's rank correlation coefficient is a measure of agreement between the observed performance orders and the true ones. It is shown that Spearman's coefficient converges exponentially in the simulation time or observation time, which gives a strong evidence of the efficiency of order comparison for discrete event dynamic systems. In the context of simulation, the effect of simulation dependence on the alignment is also discussed. It is found that neither independent simulation nor the scheme of common random numbers (CRN), a popular scheme for variance reduction, can yield dominant performance. Finally, numerical examples based on a networking optimization problem are provided to illustrate the convergence of Spearman's coefficient. In these examples, the standard clock (SC) simulation technique provides much faster convergence than either independent simulations or CRN simulations. Both the SC and CRN methods use the same random number sequence to drive many events in parallel; however, under SC the events driving the parallel experiments are all identical, whereas under CRN they may be different.
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    URL: http://dx.doi.org/10.1023/A:1008301531221
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    Repeatability of Real World Training Experiments: A Case Study (1999)
    Springer
    Autonomous robots 6 (1999), S. 281-292 
    Details
    ISSN: 1573-7527
    Keywords: mobile robotics ; reinforcement learning ; artificial neural networks ; simulation ; real world
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We present a case study of reinforcement learning on a real robot that learns how to back up a trailer and discuss the lessons learned about the importance of proper experimental procedure and design. We identify areas of particular concern to the experimental robotics community at large. In particular, we address concerns pertinent to robotics simulation research, implementing learning algorithms on real robotic hardware, and the difficulties involved with transferring research between the two.
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    URL: http://dx.doi.org/10.1023/A:1008984312527
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    Thinking in Levels: A Dynamic Systems Approach to Making Sense of the World (1999)
    Springer
    Journal of science education and technology 8 (1999), S. 3-19 
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    ISSN: 1573-1839
    Keywords: levels ; complexity ; simulation ; modeling ; science education ; mathematics education ; dynamic systems ; systems thinking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract The concept of emergent "levels" (i.e., levels that arise from interactions of objects at lower levels) is fundamental to scientific theory. In this paper, we argue for an expanded role for this concept of levels in science education. We show confusion of levels (and "slippage" between levels) as the source of many of people's deep misunderstandings about patterns and phenomena in the world. These misunderstandings are evidenced not only in students' difficulties in the formal study of science but also in their misconceptions about experiences in their everyday lives. The StarLogo modeling language is designed as a medium for students to build models of multi-leveled phenomena and through these constructions explore the concept of levels. We describe several case studies of students working in StarLogo. The cases illustrate students' difficulties with the concept of levels, and how they can begin to develop richer understandings.
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    URL: http://dx.doi.org/10.1023/A:1009421303064
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    General system theory: Toward a conceptual framework for science and technology education for all (1993)
    Springer
    Journal of science education and technology 2 (1993), S. 447-459 
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    ISSN: 1573-1839
    Keywords: Science education for all ; general system theory ; system thinking ; learning technology ; complexity ; simulation ; real world
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract In this paper we suggest using general system theory (GST) as a unifying theoretical framework for “science and technology education for all.” Five reasons are articulated: the multidisciplinary nature of systems theory, the ability to engage complexity, the capacity to describe system dynamics and change, the ability to represent the relationship between the micro-level and macro-level of analysis, and the ability to bring together the natural and human worlds. The historical origins of system ideas are described, and the major concepts of system theory are mapped; including the mathematical, technological, and philosophical constructs. The various efforts to implement system thinking in educational contexts are reviewed, and three kinds of learning environments are defined: expert presentation, simulation, and real-world. A broad research agenda for exploring and drawing-out the educational implications of system thinking and learning is outlined. The study of both real-world and simulated learning environments is advocated.
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    URL: http://dx.doi.org/10.1007/BF00694427
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    Some consequences of applying lognormal theory to pseudolognormal distributions (1975)
    Springer
    Mathematical geology 7 (1975), S. 117-128 
    Details
    ISSN: 1573-8868
    Keywords: data processing ; lognormal theory ; sampling ; simulation ; statistics ; transformations ; economic geology ; mining ; sedimentology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A logarithmic transformation may be used to improve the efficiency of estimates of the mean when observations follow the lognormal distribution. But if this transformation is applied to observations that follow another distribution, bias may be introduced. We consider some consequences of erroneously applying lognormal estimation theory and demonstrate that biased estimates may be obtained for certain classes of distributions. Illustrations of bias obtained in gold sampling are given.
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    URL: http://dx.doi.org/10.1007/BF02080488
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    Sampling variation of principal components (1977)
    Springer
    Mathematical geology 9 (1977), S. 497-506 
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    ISSN: 1573-8868
    Keywords: principal components ; sampling ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The convenience of reducing the dimension of a data matrix by principal component analysis invites substantive interpretation of the coefficients of the components. To test the consistency of component coefficients, 10 samples of approximately 25, 50, 100, and 200 items each were randomly drawn, with replacement, from a source sample consisting of 2086 subalkaline asalt analyses. From each sample principal components were calculated using 9 major oxides as variables. Although the eigenvalues are remarkably consistent, both across and within sample size groups, the coefficients of the eigenvectors are subject to considerable sample variance. It is sometimes assumed that the coefficients of the components calculated from small samples are well enough known to be used in detailed petrological interpretation. Our results indicate that the validity of this assumption should be tested in each specific research even when rather large samples are used. The testing procedure used here is suitable of a sufficiently large reservoir of sample items is available; in the absence of such a reservoir complete simulation could be used.
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    URL: http://dx.doi.org/10.1007/BF02100961
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    Application of Markov analysis to the Banff Formation (Mississippian), Alberta (1975)
    Springer
    Mathematical geology 7 (1975), S. 47-61 
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    ISSN: 1573-8868
    Keywords: Markov processes ; simulation ; cyclothems ; stratigraphy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The Banff Formation (Mississippian) is a sequence of limestone and shale exposed in the southern Canadian Rocky Mountains and underlying the adjacent plains. It was chosen as a vehicle to evaluate Markov-inspired techniques in sedimentary sequences where repetition of rock types is typical but a pattern of cyclicity is not obvious. Distributions of rock-unit thickness in two outcrop sections of the Banff Formation are not all exponential, therefore a one-step Markov model using an equal observational interval is not valid. Memory is indicated by the embedded-chain model. The most likely pattern of recurrence is delineated; shale is the most independent lithologic type and therefore the initial lithology in any ideal pattern. Neither factoring nor powering a probability matrix for the Banff Formation revealed geological cyclicity as defined by W. Schwarzacher. Several problems limit the application of Markov models to sedimentary sequences. Statistical validity requires a minimum number of observations, and in the attainment of a sound statistical basis, geological pertinence may be seriously reduced. Treatment of the probability matrix, by principal components analysis or by powering, yields an exacting criterion for cyclicity.
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    URL: http://dx.doi.org/10.1007/BF02080633
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    Exploration geochemistry—Distribution of elements and recognition of anomalies (1975)
    Springer
    Mathematical geology 7 (1975), S. 415-446 
    Details
    ISSN: 1573-8868
    Keywords: data processing ; discriminant analysis ; graphics ; mapping ; sampling ; simulation ; geochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The exploration geochemist faces a serious problem in reconciling theoretical statistics with the empirical distribution of elements in materials in the earth's crust. The results of computer-simulation experiments being conducted by the Exploration Geochemistry Group at the University of New Brunswick illustrate some of the problems of the relation between frequency distributions and spatial distributions of elements and raise some interesting questions about sampling patterns and physical size of samples. Most importantly, the simulation experiments and empirical examples support the contention that attempts to make an assumption of normality more efficient by performing log transformations on positively skewed data may defeat the purpose of statistical analysis for exploration work. New developments in computer-data presentation and interpretation, including population sorting and classification, illustrate the increasing use of the computer in exploration geochemistry.
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    URL: http://dx.doi.org/10.1007/BF02080498
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    Entropy and spatial disorder (1993)
    Springer
    Mathematical geology 25 (1993), S. 329-355 
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    ISSN: 1573-8868
    Keywords: spatial entropy ; Gaussian model ; simulation ; fluid flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The majority of geostatistical estimation and simulation algorithms rely on a covariance model as the sole characteristic of the spatial distribution of the attribute under study. The limitation to a single covariance implicitly calls for a multivariate Gaussian model for either the attribute itself or for its normal scores transform. The Gaussian model could be justified on the basis that it is both analytically simple and it is a maximum entropy model, i.e., a model that minimizes unwarranted structural properties. As a consequence, the Gaussian model also maximizes spatial disorder (beyond the imposed covariance) which can cause flow simulation results performed on multiple stochastic images to be very similar; thus, the space of response uncertainty could be too narrow entailing a misleading sense of safety. The ability of the sole covariance to adequately describe spatial distributions for flow studies, and the assumption that maximum spatial disorder amounts to either no additional information or a safe prior hypothesis are questioned. This paper attempts to clarify the link between entropy and spatial disorder and to provide, through a detailed case study, an appreciation for the impact of entropy of prior random function models on the resulting response distributions.
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    URL: http://dx.doi.org/10.1007/BF00901422
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    Improvement of Fourier-Based Unconditional and Conditional Simulations for Band Limited Fractal (von Kármán) Statistical Models (1999)
    Springer
    Mathematical geology 31 (1999), S. 627-649 
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    ISSN: 1573-8868
    Keywords: simulation ; conditional simulation ; fourier methods ; band-limited fractal ; variogram ; fast kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract We evaluate the performance and statistical accuracy of the fast Fourier transform method for unconditional and conditional simulation. The method is applied under difficult but realistic circumstances of a large field (1001 by 1001 points) with abundant conditioning criteria and a band limited, anisotropic, fractal-based statistical characterization (the von Kármán model). The simple Fourier unconditional simulation is conducted by Fourier transform of the amplitude spectrum model, sampled on a discrete grid, multiplied by a random phase spectrum. Although computationally efficient, this method failed to adequately match the intended statistical model at small scales because of sinc-function convolution. Attempts to alleviate this problem through the “covariance” method (computing the amplitude spectrum by taking the square root of the discrete Fourier transform of the covariance function) created artifacts and spurious high wavenumber content. A modified Fourier method, consisting of pre-aliasing the wavenumber spectrum, satisfactorily remedies sinc smoothing. Conditional simulations using Fourier-based methods require several processing stages, including a smooth interpolation of the differential between conditioning data and an unconditional simulation. Although kriging is the ideal method for this step, it can take prohibitively long where the number of conditions is large. Here we develop a fast, approximate kriging methodology, consisting of coarse kriging followed by faster methods of interpolation. Though less accurate than full kriging, this fast kriging does not produce visually evident artifacts or adversely affect the a posteriori statistics of the Fourier conditional simulation.
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    Some theoretical aspects on morphology development in seeded composite latexes. I. Batch conditions below monomer saturation (1993)
    Springer
    Colloid & polymer science 271 (1993), S. 607-615 
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    ISSN: 1435-1536
    Keywords: Emulsion ; morphology ; interfacial tension ; thermodynamics ; modeling ; simulation ; copolymers ; seed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In seeded emulsion polymerization, during the second stage, new interfaces appear and the surface area changes. A thermodynamic equilibrium approach is presented which predicts particle morphology of a whole range of non-spherical particles upon polymer conversion. Simulation takes into account swelling ratio, molar volumes and interfacial tension. As the particle geometry is complex, a new mathematical procedure is detailed. The computed data are useful to discuss either the stability or the instability of the particles morphology. These results must be compared with actual experimental structures.
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    Problem-Based Learning in Residency Education: A Novel Implementation Using a Simulator (1999)
    Springer
    Journal of clinical monitoring and computing 15 (1999), S. 227-232 
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    ISSN: 1573-2614
    Keywords: simulation ; problem-based learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Background. We developed a problem-based learning exercise with a full-scale human patient simulator to teach residents the emergency management and differential diagnosis of acute intraoperative hypotension. Methods.We developed the exercise through the following steps: clear definition of learning objectives, preparation of an appropriate case stem, development of clinically realistic scenarios to illustrate objectives, and an interactive instructor to stimulate discussion. Results. The exercise focused on the differential diagnosis of intraoperative hypotension, and the acute treatment of hypovolemia, cardiac tamponade, tension pneumothorax, and anaphylaxis. Conclusions. Exercises on a full-scale patient simulator are a natural extension of problem-based learning. Recent research in learning theory provides the rationale for this teaching modality's potential as a learning tool.
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    URL: http://dx.doi.org/10.1023/A:1009980500385
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    Autoregulation in a Simulator-Based Educational Model of Intracranial Physiology (1999)
    Springer
    Journal of clinical monitoring and computing 15 (1999), S. 481-491 
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    ISSN: 1573-2614
    Keywords: Cerebral blood flow ; cerebral vascular resistance ; cerebral perfusion pressure ; PaCO2 ; PaO2 ; cerebral metabolic rate of oxygen consumption ; educational model ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Objective.To implement a realistic autoregulation mechanism toenhance an existing educational brain model that displays in real-time thecerebral metabolic rate (CMRO2), cerebral blood flow (CBF),cerebral blood volume (CBV), intracranial pressure (ICP), and cerebralperfusion pressure (CPP). Methods.A dynamic cerebrovascular resistance(CVR) feedback loop adjusts automatically to maintain CBF within a range ofthe CPP and defines autoregulation. The model obtains physiologic parametersfrom a full-scale patient simulator. We assumed that oxygen demand andarterial partial pressure of carbon dioxide (CO2 responsivity) arethe two major factors involved in determining CBF. In addition, our brainmodel increases oxygen extraction up to 70% once CBF becomes insufficient tosupport CMRO2. The model was validated against data from theliterature. Results.The model's response varied less than 9%from the literature data. Similarly, based on correlation coefficients betweenthe brain model and experimental data, a good fit was obtained for curvesdescribing the relationship between CBF and PaCO2 at a meanarterial blood pressure of 150 mm Hg (R2 = 0.92) and 100 mm Hg(R2 = 0.70). Discussion.The autoregulated brain model, withincorporated CO2 responsivity and a variable oxygen extraction,automatically produces changes in CVR, CBF, CBV, and ICP consistent withliterature reports, when run concurrently with a METI full-scale patientsimulator (Medical Education Technologies, Inc., Sarasota, Florida). Once themodel is enhanced to include herniation, vasospasm, and drug effects, itsutility will be expanded beyond demonstrating only basic neuroanesthesiaconcepts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009998606087
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    A Simple Strategy for Faster Induction and More Cost-Effective Use of Anesthetic Vapor (1999)
    Springer
    Journal of clinical monitoring and computing 15 (1999), S. 17-21 
    Details
    ISSN: 1573-2614
    Keywords: Low flow anesthesia ; inhaled anesthetics ; anesthetic cost ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Introduction. Inducing general anesthesia often involves mask ventilation using high fresh gas flow (FGF) to administer anesthetic vapor prior to endotracheal intubation. A common practice is to turn the vaporizer off when the mask is removed from the patient's face to avoid room contamination (VAPOff). An alternative approach is to leave the vaporizer on and turn the FGF to minimum to reduce the amount of vapor laden gas that can enter the room (FGFOff). The objective of this study is to compare the relative induction times and vapor costs associated with each induction strategy. Methods. Each induction method was simulated using Gasman® (MedMan Simulations, Chestnut Hill, MA) for Windows assuming a 70 kg patient. To simulate a period of mask ventilation with anesthetic vapor prior to intubation, the FGF was set to 6 l/min and the isoflurane vapor concentration to 1.2% (1 MAC) for three minutes with an alveolar ventilation of 5 l/min and cardiac output of 5 l/min. For the first simulation of the intubation period (FGFOff), FGF was turned to 150 ml/min, minute ventilation was set to zero and the vaporizer setting unchanged for one minute. Initial settings were then restored and the rate of change of anesthetic vapor concentration in the circuit (Vckt) and alveolus (Valv) followed for 10 minutes along with the cost of delivered vapor (V$). For the second simulation (VAPOff), after the initial three minutes of vapor delivery, the vaporizer was set to zero, minute ventilation was set to zero and the FGF left unchanged for one minute. The initial settings were then restored and Vckt, Valv and V$ followed for ten minutes. The cost calculation was based upon a 100 ml bottle of Isoflurane at $72/bottle. Actual gas flow was measured at the y-piece of a circle system for fresh gas flows from 0.15 to 6 l/min. Results. At the end of the simulated intubation period (minute 4), Vckt was unchanged with the FGFOff method whereas it had fallen by more than half with the VAPOff method. Using VAPOff, it took until the 6-minute mark for Vckt to return to the same concentration that existed prior to intubation at minute three. Throughout the 10 minute simulated induction, Valv using FGFOff exceeded Valv using VAPOff although the difference became small at the end of the period. V$ was essentially identical at all time points. No flow into the room was measured at the minimum fresh gas flow whereas higher fresh gas flows resulted in a significant portion of the fresh gas flowing into the room. Conclusions. The strategy of turning the FGF to minimum and leaving the vaporizer on during intubation does not contaminate the room and speeds induction by fostering a greater alveolar concentration than the VAPOff method. Cost savings are derived using FGFOff since a higher alveolar concentration is achieved at the same vapor cost. Additional cost savings are demonstrated since a low flow technique is possible immediately after intubation when using FGFOff. The practice of turning off the vaporizer during endotracheal intubation while FGF remains high should be abandoned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009900605045
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    How to predict viscous fingering in three component flow (1993)
    Springer
    Transport in porous media 12 (1993), S. 207-236 
    Details
    ISSN: 1573-1634
    Keywords: Miscible flow ; Riemann problems ; simulation ; viscous fingering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In a WAG process (Water Alternate Gas), water and a miscible solvent (gas) are injected into a reservoir containing water and oil. The solvent will finger through the oil, leading to early breakthrough and poor recovery. Compared with a miscible flood, when only solvent is injected, fingering is supressed by the simultaneous injection of water, since this reduces the apparent mobility contrast between the injected and displaced fluids. The fingering in a miscible flood, with only hydrocarbon flowing, can be modelled successfully using a Todd and Longstaff fractional flow. In this paper, we demonstrate how to modify the effective Todd and Longstaff mobility ratio self-consistently to account for fingering in three component systems. The resultant empirical equations of flow are solved exactly in one dimension and are in excellent agreement with the averaged saturation and concentration profiles computed using two dimensional high resolution simulation, for a variety of injected water saturations, in both secondary and tertiary displacements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00624459
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    Renormalization calculations of immiscible flow (1993)
    Springer
    Transport in porous media 12 (1993), S. 237-260 
    Details
    ISSN: 1573-1634
    Keywords: Effective properties ; relative permeability ; pseudoization ; rescaling ; heterogeneity ; simulation ; reservoir characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Oil reservoir properties can vary over a wide range of length scales. Reservoir simulation of the fluid flow uses numerical grid blocks have typical lengths of hundreds of metres. We need to specify meaningful values to put into reservoir engineering calculations given the large number of heterogeneities that they have to encompass. This process of rescaling data results in the calculation of ‘effective’ or ‘pseudo’ rock properties. That is a property for use on the large scale incorporating the many heterogeneities measured on smaller scales. For single phase flow, a variety of techniques have been tried in the past. These range from very simple statistical estimates to detailed numerical simulation. Unfortunately, the simple estimates tend to be inaccurate in real applications and the numerical simulation can be computationally expensive if not impossible for very fine grid representations of the reservoir. Likewise, pseudorelative permeabilities are time consuming to generate and often inaccurate. Real-space renormalization is an alternative technique which has been found to be computationally efficient and accurate when applied to single-phase flow. This approach solves the problem regionally rather than trying to solve the whole problem in one simulation. The effective properties of small regions are first calculated and then placed on a coarse grid. The grid is further coarsened and the process repeated until a single effective property has been calculated. This has enabled calculation of effective permeability of extremely large grids to be performed, up to 540 million grid blocks in one application. This paper extends the renormalization technique to two-phase fluid flow and shows that the method is at least 100 times faster than conventional pseudoization techniques. We compare the results with high resolution numerical simulation and conventional pseudoization methods for three different permeability models. We show that renormalization is as accurate as the conventional methods when used to predict oil recovery from heterogeneous systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00624460
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    Models of stochastic geometry — A survey (1993)
    Springer
    Mathematical methods of operations research 38 (1993), S. 235-260 
    Details
    ISSN: 1432-5217
    Keywords: Boolean model ; damaged forests ; mark correlation function ; marked point process ; M/G/∞ ; random compact set ; simulation ; spatial correlation ; spatial statistics ; stochastic model ; tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract This paper discusses some models of stochastic geometry which are of potential interest for operations research. These are the Boolean model, a certain model for random compact sets and marked point processes. The Boolean model is a generalization of the well-known queueing systemM/G/∞. The random compact set model may be useful for modelling spatial spreading processes such as fires, cancers or holes in the Earth's surface. Marked point processes are used here as models of forests and used for a statistical study of the spatial distribution of damaged trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01416606
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  • 92
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    Stochastic Comparison Algorithm for Discrete Optimization with Estimation of Time-Varying Objective Functions (1999)
    Springer
    Journal of optimization theory and applications 103 (1999), S. 137-159 
    Details
    ISSN: 1573-2878
    Keywords: Stochastic optimization ; simulation ; estimation ; time-varying objective functions ; discrete event dynamic systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, the optimization of time-varying objective functions, known only through estimates, is considered. Recent research defined algorithms for static optimization problems. Based on one of these algorithms, we derive an optimization scheme for the time-varying case. In stochastic optimization problems, convergence of an algorithm to the optimum prevents the algorithm from being efficiently adaptive to changes of the objective function if it is time-varying. So, convergence cannot be required in a time-varying scenario. Rather, we require convergence to the optimum with high probability together with a satisfactory dynamical behavior. Analytical and simulative results illustrate the performance of the proposed algorithm compared with other optimization techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021777501274
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    The stalactite plot for the detection of multivariate outliers (1993)
    Springer
    Statistics and computing 3 (1993), S. 27-35 
    Details
    ISSN: 1573-1375
    Keywords: elemental set ; Mahalanobis distance ; masking ; Monte Carlo testing ; normalized distance ; outliers ; simulation ; stalactite plot
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Detection of multiple outliers in multivariate data using Mahalanobis distances requires robust estimates of the means and covariance of the data. We obtain this by sequential construction of an outlier free subset of the data, starting from a small random subset. The stalactite plot provides a cogent summary of suspected outliers as the subset size increases. The dependence on subset size can be virtually removed by a simulation-based normalization. Combined with probability plots and resampling procedures, the stalactite plot, particularly in its normalized form, leads to identification of multivariate outliers, even in the presence of appreciable masking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146951
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  • 94
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    Time-Dependent Rheological Properties of Semi-Solid Metal Alloys (1999)
    Springer
    Mechanics of time-dependent materials 3 (1999), S. 15-30 
    Details
    ISSN: 1573-2738
    Keywords: modelling ; semi-solid materials ; simulation ; suspensions ; thixoforming ; thixotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Semi-solid metal alloys, as used in thixoforming, have a special microstructure of globular grains suspended in a liquid metal matrix. The complex rheological properties are strongly influenced by the local solid fraction, particle shape, particle size and state of agglomeration. There is a high demand for models and software tools allowing the simulation of semi-solid casting processes. The material under investigation is a tin-lead alloy (Sn-15%Pb) which exhibits a similar microstructure to aluminium alloys. The experiments were performed with a concentric cylinder rheometer of the Searle type. Initially, the liquid alloy is cooled down to the semi-solid range under constant shearing and then kept under isothermal conditions for further experimentation. Based on the experimental data, a single-phase model has been derived where the semi-solid alloy is regarded as a homogeneous material with thixotropic properties and the microstructure is characterised by a structural parameter. The model consists of two parts: the equation of state, including a finite yield stress, and a rate equation for the structural parameter. The model equations are employed in numerical software and used for the simulation of characteristic filling cases and the comparison with the conventional filling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009856708511
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    Synthesis and Characterization of a Polycrystalline Ionic Thin Film by Large-Scale Molecular-Dynamics Simulation (1999)
    Springer
    Interface science 7 (1999), S. 15-31 
    Details
    ISSN: 1573-2746
    Keywords: polycrystal ; ionic ; oxide ; molecular-dynamics ; simulation ; growth ; thin film ; structure ; characterization ; grain boundary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A simulation methodology for the synthesis of polycrystalline, ionic thin films is developed. The method involves the preparation of a polycrystalline substrate onto which a thin film is subsequently grown by crystallization from the melt. A detailed structural analysis of a textured sixteen-grain FeO film, with a grain size of approximately 4.7 nm, shows that the interiors of the grains are almost perfect single crystals with only a very few vacancies and no interstitials. The grains are delineated by 〈001〉 tilt grain boundaries; as expected, the low-angle grain boundaries in the film consist of arrays of dislocations, while the high-angle grain boundaries are relatively narrow and well ordered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008782230777
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    Environment of the P b center at the Si(111)/oxide interface (1993)
    Springer
    Interface science 1 (1993), S. 139-146 
    Details
    ISSN: 1573-2746
    Keywords: Silicon ; defects ; hyperfine interactions ; oxidation ; computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We assess several models for the environment of the P b center (Si dangling bond center) at the interface of Si(111) with its oxide. The comparison of hyperfine constants observed with those predicted using large cluster models favors a local structure in which there is an Si-Si bond within the oxide close to the Si dangling bond. Such Si-Si bonds are also suggested by a number of other experiments and are consistent with the “reactive layer” model proposed to rationalize a range of oxidation studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203603
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    Dataflow query execution in a parallel main-memory environment (1993)
    Springer
    Distributed and parallel databases 1 (1993), S. 103-128 
    Details
    ISSN: 1573-7578
    Keywords: parallel query processing ; multi-join queries ; simulation ; analytical modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, the performance and characteristics of the execution of various join-trees on a parallel DBMS are studied. The results of this study are a step into the direction of the design of a query optimization strategy that is fit for parallel execution of complex queries. Among others, synchronization issues are identified to limit the performance gain from parallelism. A new hash-join algorithm is introduced that has fewer synchronization constraints than the known hash-join algorithms. Also, the behavior of individual join operations in a join-tree is studied in a simulation experiment. The results show that the introduced Pipelining hash-join algorithm yields a better performance for multi-join queries. The format of the optimal join-tree appears to depend on the size of the operands of the join: A multi-join between small operands performs best with a bushy schedule; larger operands are better off with a linear schedule. The results from the simulation study are confirmed with an analytic model for dataflow query execution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01277522
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    Strain tensor for large three-dimensional surface deformation of sheet metal from an object grating (1999)
    Springer
    Experimental mechanics 39 (1999), S. 30-35 
    Details
    ISSN: 1741-2765
    Keywords: Three-dimensional deformation ; sheet metal ; grating method ; deformation gradient ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Grating techniques are used to determine the three-dimensional deformation and the tangential strain of sheet metal. A grating is fixed on the surface and taken by stereo CCD cameras in different deformation states. By suitable line-following software, the grating coordinates in the images are determined with subpixel accuracy. Using photogrammetric methods, the three-dimensional coordinates are calculated from the image coordinates. The strain usually is determined by means of a deformation gradient, which is calculated from every deformed triangle. In this paper, the gradient is determined in the center of four neighboring meshes using a polynomial approximation of the displacement function in a reference position. The influence of the nontangential deformation is considered. By simulation, a flat sheet metal is deformed to a rotational symmetric surface. The difference of the known exact strain is compared with the numerically derived strain with respect to different grating pitches. The proposed method yields good results even in the case of large spatial deformation. It is applied to the deformation of a hatlike test specimen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02329298
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