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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 13 (1999), S. 383-407 
    ISSN: 1573-1650
    Keywords: critical period ; reliability ; resilience ; surface water reservoirs ; within-year and over-year behaviours
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Surface water reservoirs can beclassified as either within-year or over-year based onthe duration of their critical period (CP). Ingeneral, within-year systems are those which willrefill and spill several times in a year, whereasover-year systems have much longer critical periods,usually of the order of years. If the duration of thecritical period, and hence the precise mode ofbehaviour, of a reservoir were to be known apriori, then advantage could be taken of this toselect the level of detail required for reservoiranalysis. For example, if the reservoir system ispurely over-year, i.e. the CP is much longer than 12months, then only annual streamflow data are requiredfor analysis. On the contrary, systems which exhibitdual within-year and over-year behaviours will requiretime series data of a finer resolution to capture boththe seasonal and annual discrepancies between thedemand and inflow. Such a consideration often resultsin a phenomenal increase in the analysis time overthat required for annual data. Finally, if the systemis purely within-year, then the analysis effort can besignificantly reduced by concentrating on the criticalor driest year of the record. In this paper, weexamine the properties of the test in current use fordistinguishing between within-year and over-yearbehaviours. In particular we investigate how theparameter of the test is related to the CP, and weargue that knowing the CP is a more complete test. Wethen develop predictive equations for the CP and weoffer suggestions for extending the study.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 12 (1998), S. 13-30 
    ISSN: 1573-1650
    Keywords: risk ; reliability ; resiliency ; vulnerability ; drought risk index ; drought damage index ; simulation ; water supply ; reservoir operation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract In this study, simulation is used to evaluate the performance of the municipal water system in Fukuoka city. In combination with daily simulation model, a kind of risk model incorporating water demand prediction is presented. This model applies five risk indices: reliability, resiliency, vulnerability, drought risk index (DRI) and drought damage index (DDI). They aid in the identification of operation policies for the municipal water system, and the planning and operational policies obtained are aimed at achieving minimum risk for a given scenario of operation. In this paper, the performance risk of the municipal water system is investigated under three alternatives: (1) the existing system operation when available supply from the Chikugo river is decreased; (2) water restrictions for different percentages of reduction are implemented; and (3) available water supply increases when desalination of sea water is implemented. The results obtained show that savings of between 5 and 12% of water consumption from May 1, or increasing of daily desalination of sea water about 30 000 m3 or more, may efficiently decrease the performance risk of the Fukuoka water supply system. Potentials also exist for further increase of reservoir storage by more rational operation. The measure that more attention should be paid to increasing the water supply from stable sources is recommended as well.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 12 (1998), S. 95-120 
    ISSN: 1573-1650
    Keywords: reliability ; resilience ; vulnerability ; reservoirhedging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Based on a detailed Monte-Carlo simulation, the effects of hedging parameters namely, starting water availability (SWA), ending water availability (EWA) and hedging factor (HF) on reservoir storage performance indicators have been investigated within the storage-yield plane of over-year reservoirs. Also, trade-off relationships between the various storage performance indicators are developed and selection of reasonable compromising hedging policies based on performance criteria is attempted for over-year reservoirs. Regions within the storage-yield plane of over-year reservoirs where hedging would be effective are identified. This would help the reservoir managers in mitigating the severity during long stretched critical drought periods.
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  • 4
    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.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Transportation 21 (1994), S. 203-228 
    ISSN: 1572-9435
    Keywords: reliability ; SP experiments ; uncertainty ; users' benefits ; value of time ; variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract Current benefits from travel time savings have only been related to the benefits from reducing mean travel time. Some previous attempts of including variability in the generalised cost function have mainly assumed commuters with fixed arrival time. This paper presents a comprehensive framework for valuing travel time variability that allows for any journey purpose and arrival time constraint. The proposed model is based on the expected utility approach and the mean-standard deviation approach. Stated Preference methods are considered the best technique for providing the data for calibrating the models. The values of time derived from the models are highly influenced by the value of travel time variability and it strongly depends on the probability distribution function travellers are faced with.
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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.
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  • 7
    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.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 6 (1992), S. 57-67 
    ISSN: 1573-1650
    Keywords: Athens water supply ; reliability ; operating rules ; safety storage ; hydrological simulation ; reservoir design ; policy analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract This paper presents an investigation of a real-world water-resources problem involving both planning and management aspects. The Athens water supply system is studied in order to assist its future operation and the design of alternative system-improving works. The yield of the existing system is first assessed via simulation. Then the risk of system failure to meet the water demand is evaluated for various water demand scenarios and operation policies, with emphasis on the 1989–90 critical situation. Alternative future reservoirs in the Evinos River Basin are studied by testing large number of technical solutions. Uncertainties on hydrology, leakage losses, water demand, and possible damages are taken into account. Finally, a computer programme is developed to assist the water supply policy design for the existing Mornos-Iliki system.
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  • 9
    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.
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  • 10
    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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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 2 (1988), S. 21-34 
    ISSN: 1573-1650
    Keywords: Stochastic programming ; linear programming ; objective function ; synthetic streamflow ; reliability ; skewed ; random variable ; spill ; release ; storage ; free board
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A generalized linear decision rule is presented which takes into account the aspect of spill in a multi-lag LDR model. The proposed rule incorporates past inflow experience to determine the optimum release rules based on a stochastic (linear) programming optimization model. It also prescribes a procedure of determining spill, should it occur, and the method of adjusting the release policy, accordingly, for the subsequent periods, which are directly affected by the spill of the current period. The use of the rule also makes it possible to produce a specification for a reservoir with a smaller capacity by taking liberal constraints on the reservoir freeboard during the monsoon months. The problem is solved, for the purpose of illustration, using the historical data of a river located in central India. Two synthetic streamflow series of a duration of 50 years each are generated under lognormal flow assumption. The prescribed release rules are applied to a hypothetical reservoir with the optimum capacity determined by the linear programming method, and the generated series as the inflow. The results and findings are quite satisfactory.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 2 (1988), S. 87-102 
    ISSN: 1573-1650
    Keywords: Performance ; resilience ; reliability ; developing countries ; agricultural planning ; investment scheduling ; income redistribution ; trade-off
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The conflict between performance measured in terms of economic and income redistribution objectives, resilience and reliability of irrigated agricultural expansions in developing countries is investigated via a planning framework consisting of three sequential optimization models. The first model determines the most economic planning alternatives. The second model examines, in terms of an income redistribution criterion, the social attractiveness of each plan. The third model determines resilience and operating rules of the various alternatives. The planning framework is appled for a hypothetical agricultural expansion on the order of 30 000 hectares based on data from the Nile Delta in Egypt. The trade-off between system performance, reliability and resilience is derived.
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  • 13
    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.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 1 (1987), S. 241-254 
    ISSN: 1573-1650
    Keywords: Groundwater management ; optimization ; uncertainty analysis ; reliability ; multiple-objective analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Like any other resources planning and management, groundwater management is performed in a stochastic environment in which the system itself involves a number of random elements. Consequences as a result of decisions made based on analyses are not certain. This paper presents a management model using the chance-constrained framework which explicitly considers the random nature of aquifer properties. The model enables the derivation of an optimal groundwater management policy that would satisfy required operation performance reliability. Furthermore, the chance-constrained model is extended to the multi-objective optimization framework in which a tradeoff between total water supply pumpage and system performance reliability is explicitly considered. The models are applied to a hypothetical example of a steady, nonuniform, homogeneous confined aquifer.
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