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  • Articles  (33)
  • uncertainty  (19)
  • reliability  (15)
  • Architecture, Civil Engineering, Surveying  (24)
  • Sociology  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Air Transport Management 1 (1994), S. 229-236 
    ISSN: 0969-6997
    Keywords: Denver ; airlines ; airport passenger buildings ; airports ; automation ; baggage systems ; reliability
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Architecture, Civil Engineering, Surveying , Economics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 10 (1996), S. 167-186 
    ISSN: 1436-3259
    Keywords: Reservoir stochastic theory ; reliability ; mean ; variance ; indicator function ; storage bounds ; nonlinear programming ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A new formulation is presented for the analysis of reservoir systems synthesizing concepts from the traditional stochastic theory of reservoir storage, moments analysis and reliability programming. The analysis is based on the development of the first and second moments for the stochastic storage state variable. These expressions include terms for the failure probabilities (probabilities of spill or deficit) and consider the storage bounds explicitly. Using this analysis, expected values of the storage state, variances of storage, optimal release policies and failure probabilities — useful information in the context of reservoir operations and design, can be obtained from a nonlinear programming solution. The solutions developed from studies of single reservoir operations on both an annual and monthly basis, compare favorably with those obtained from simulation. The presentation herein is directed to both traditional reservoir storage theorists who are interested in the design of a reservoir and modern reservoir analysts who are interested in the long term operation of reservoirs.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 309-320 
    ISSN: 1436-3259
    Keywords: Entropy ; reliability ; redundancy ; water distribution networks ; nodal pair reliability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Entropy based expressions for measurement of reliability and redundancy have recently been reported. These measures approach assessment of the reliability of the distribution network from the intrinsic redundancy of the network layout. The paper extends earlier work on entropy functions by including a more explicit statement of the alternate paths available in the network and by recognizing that under certain circumstances, e.g., failure of some part of the network work, an outflow link from a node under normal working condition may become an inflow link to the same node. The measures are assessed by comparison with parameters measuring Nodal Pair Reliability and percentage of flow supplied at adequate pressure for a range of networks and link failure conditions in this networks. The entropy measures are shown to reflect changes in the network reliability, as measured by these two comparative parameters, very well.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 433-448 
    ISSN: 1436-3259
    Keywords: Risk ; uncertainty ; reservoir operation ; sedimentation ; computer application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract An attempt of using stochastic hydrologic technique to assess the intrinsic risk of reservoir operation is made in this study. A stochastic simulation model for reservoir operation is developed. The model consists of three components: synthetic generation model for streamflow and sediment sequences, one-dimensional delta deposit model for sediment transport processes in reservoirs, and simulation model for reservoir operation. This kind of integrated simulation model can be used to simulate not only the inflow uncertainty of streamflow and sedimentation, but also the variation in operation rules of reservoirs. It is herein used for the risk assessment of a reservoir, and the simulation is performed for different operation scenarios. Simulation for the 100-year period of sediment transport and deposition in the river-reservoir system indicates that the navigation risk is much higher than that of hydropower generation or sediment deposition in the reservoir. The risk of sediment deposition at the river-section near the backwater profile is also high thereby the navigation at the river-segment near this profile takes high risk because of inadequate navigation depth.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 259-268 
    ISSN: 1436-3259
    Keywords: Rainfall ; runoff ; modeling ; uncertainty ; stochastics ; stochastic integral equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract In this paper a very general rainfall-runoff model structure (described below) is shown to reduce to a unit hydrograph model structure. For the general model, a multi-linear unit hydrograph approach is used to develop subarea runoff, and is coupled to a multi-linear channel flow routing method to develop a link-node rainfall-runoff model network. The spatial and temporal rainfall distribution over the catchment is probabilistically related to a known rainfall data source located in the catchment in order to account for the stochastic nature of rainfall with respect to the rain gauge measured data. The resulting link node model structure is a series of stochastic integral equations, one equation for each subarea. A cumulative stochastic integral equation is developed as a sum of the above series, and includes the complete spatial and temporal variabilities of the rainfall over the catchment. The resulting stochastic integral equation is seen to be an extension of the well-known single area unit hydrograph method, except that the model output of a runoff hydrograph is a distribution of outcomes (or realizations) when applied to problems involving prediction of storm runoff; that is, the model output is a set of probable runoff hydrographs, each outcome being the results of calibration to a known storm event.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Fire technology 29 (1993), S. 226-245 
    ISSN: 1572-8099
    Keywords: Smoke-contaminated electronics ; surface-mounted ; recondition ; hydrogen chloride ; cleaning ; reliability ; conformal coating ; decontamination ; migration ; cleanliness ; PVC ; ultrasonic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract This work deals with problems that arise when modern surface-mounted electronics are to be reconditioned after smoke contamination. In a fire, hydrogen chloride, which is formed when polyvinylchloride is present, is deposited on various materials. Electronic equipment is especially sensitive since malfunction may occur after a longer or shorter time of operation due to the chloride contamination. Earlier work has shown that through-hole electronics can be reconditioned, with good results, after deposition of up to 100 µg chloride/cm2 in the surrounding area. The lower limit when cleaning is needed is often specified to 10 µg chloride/cm2. In this work, therefore, surface-mounted electronics have been exposed to smoke containing hydrogen chloride, which has contaminated the test boards with 45 to 75 µg chloride/cm2. Three different methods for cleaning smoke-contaminated electronics were investigated: manual, automatic spray, and ultrasonic. Each method was able to clean to a contamination level lower than 1.5 µg sodium chloride equivalents/cm2. The automatic spray method could not remove all contaminants beneath the components. All three methods were capable of improving the surface insulation resistance to a satisfactory level. Conformal coating can, to a large extent, protect the electronics against corrosive smoke. However, decontamination of boards conformally coated with acrylic coatings may be complicated since smoke products are partly absorbed into the conformal coating. The large difference between chloride contamination in a fire and during the manufacture of electronic equipment is the nature of deposition. Experiments have shown that the hydrogen chloride reacts with lead in the solder to form lead chloride. During manufacture, chloride salts are deposited all over the test board. Migration between conductors of different potential has not occurred. This is due to the fact that chloride is localized on the conductors as lead chloride. Galvanic corrosion, on the other hand, has occurred between metals within one conductor.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Fire technology 23 (1987), S. 175-185 
    ISSN: 1572-8099
    Keywords: Fire evaluation ; expert ; consensus ; stability ; reliability ; validity ; scaling measurement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract In this article some of the methodological problems associated with using the Delphi technique for the development of a Firesafety Evaluation (Points) Scheme are examined. These problems relate to: questionnaire design, the merits and demerits of Delphi groups versus panel groups, the definition of key terms (such as expert, consensus and stability), the reliability, validity and level of measurement achieved by Likert-type scaling techniques, and the differences in the decisionmaking processes of expert and nonexpert groups.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Transportation 27 (2000), S. 201-219 
    ISSN: 1572-9435
    Keywords: benefit-cost analysis ; investment timing ; major transportation investments ; net present value ; timing rules ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract The timing decision for major transportation investments – when to build – typically is made without an objective approach for considering the economic value of implementation at different times. This paper uses a model of benefit-cost analysis and derives rules for timing major transportation investments. Three sets of conditions are considered, depending on whether annual benefits of an investment are uncertain and whether the objective is to maximize net present value or simply to achieve positive net present value. The timing rules under each set of conditions are stated in three forms: benefit-cost ratio, annual benefits, and implementation time. The paper compares these timing rules analytically, discusses potential applications, and illustrates them with a numerical example. Consequences of incorrectly using the timing rules are also examined with the example.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Transportation 17 (1990), S. 29-47 
    ISSN: 1572-9435
    Keywords: freight ; mode ; choice — behaviour ; modelling ; company ; structure ; decision-making ; factor analysis ; disaggregate data ; causal relationships ; reliability ; consignment ; control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract In the next few years, exciting developments in the field of freight transport are likely to occur. The Channel Tunnel will be perceived as giving railways much greater distance of operation, compared to the current train ferry to/from Great Britain. The further development of swap-body technology will allow easier modal transfer and the creation, in 1992, of a single market in Europe will transform the pattern of trade. All of these are likely to have significant impacts on modal choice, and hence modal split, in freight transport. Reappraisal by many firms of the modes of transport used is likely but will it result in a net transfer of freight from road to rail and, if so, to what extent? To answer such questions, an accurate and reliable method of predicting modal split is required. Research in the past has concentrated on the development of modal split models based on generalised costs. These fail to explain adequately the prevalence of road freight in the UK. From surveys of freight managers within industry, it is clear that models to date rely too heavily on the economic cost factor and too little on behavioural factors (Jeffs 1985). This paper derives from a recent study of freight transport modal choice from the standpoint of the transport decision-maker within the firm. It attempts to shed light on the actual parameters which should be incorporated into a modal split model. Many variables appear to exert an influence on modal choice decision-making process. However, it is possible to categorise them into six main groups, namely: customer-requirements; product-characteristics; company structure/organisation; government interventions; available transport facilities; and perceptions of the decision-maker him/herself. It is the interactions and inter-relationships between these which ultimately determine freight modal split. This study has shown that the relationship between the outcome of the transport decision process and the values of particular determinants of modal split is not straight-forward, due to the complexity and variety of interactions involved. Perhaps one of the main reasons for researchers' failure hitherto to develop a successful modal-split model has been the preoccupation with techniques that rely on the development of common metric (e.g. generalised cost), which has led to the exclusion of some important explanatory variables along quite different dimensions. Another important issue concerns the appropriate level of aggregation. In order not to reduce the explanatory power of the key variables, it is important to work at a disaggregate level, although this does make substantial demands on data. The use of factor analysis enables both the aggregation of information without loss of behavioural reality and the specification of variables in terms of a common metric. In conclusion, freight transport has usually been examined within too narrow a framework. It must be placed firmly within the context of the total industrial process. The demand for freight transport is directly influenced by the level, composition and geographical distribution of production and consumption activities. Freight flows are complex and so it is highly unlikely that a universal mode-choice model can ever be developed. Future research should, therefore, be directed towards developing partial models in response to specific needs of those involved in decision-taking in the freight sector.
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  • 10
    ISSN: 1572-9435
    Keywords: ATIS ; dynamic assignment ; IVHS ; reliability ; route guidance ; traffic simulation ; travel behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract This paper investigates the reliability of information on prevailing trip times on the links of a network as a basis for route choice decisions by individual drivers. It considers a type of information strategy in which no attempt is made by some central controller or coordinating entity to predict what the travel times on each link would be by the time it is reached by a driver that is presently at a given location. A specially modified model combining traffic simulation and path assignment capabilities is used to analyze the reliability of the real-time information supplied to the drivers. This is accomplished by comparing the supplied travel times (at the link and path levels) to the actual trip times experienced in the network after the information has been given. In addition, the quality of the decisions made by drivers on the basis of this information (under alternative path switching rules) is evaluated ex-post by comparing the actually experienced travel time (given the decision made) to the time that the driver would have experienced without the real-time information. Results of a series of simulation experiments under recurrent congestion conditions are discussed, illustrating the interactions between information reliability and user response.
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