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System Behaviour (system + behaviour)

Distribution by Scientific Domains

Engineering	69%

Selected Abstracts

Systemverhalten und Prozessoptimierung beim Erddruckschild

GEOMECHANICS AND TUNNELLING, Issue 3 2008
Ulrich Maidl Dr.-Ing.
Eine konsequente Analyse der Prozessdaten kann die Sicherheit, aber auch die Effektivität des Ressourceneinsatzes beim hoch technisierten Schildvortrieb erheblich steigern. Präventive Maßnahmen zur Prozessoptimierung können durch die zeitnahe Analyse des Systemverhaltens während des Bauablaufs rechtzeitig eingeleitet werden. Eine Analyse des Systemverhaltens wird durch die Aufspaltung des Bauablaufs in Teilprozesse und die Definition der Schlüsselprozesse möglich. Im folgenden Artikel wird am Beispiel des Erddruckschilds aufgezeigt, wie beim heutigen Stand der Technik Prozesse realitätsnah simuliert und während der Ausführung unter Einsatz der vorhandenen Mess- und Datenerfassungstechnik analysiert werden können. System Behaviour and Process Optimization at EPB Shield A consistent analysis of the process parameters in highly mechanised shield tunnelling, not only increases the safety, but it also improves the efficiency of the resources in action. The real time analysis of the system's behaviour allows to timely carry out preventive measures during the construction process with the aim of optimizing the construction process. The analysis of the system's behaviour is possible by splitting the construction sequence in a series of partial processes and by defining the key processes. The present paper represents an EPB shield study case, which shows how the present state of the art allows simulating processes realistically during construction, by applying existing monitoring and data registration technology. [source]

A new space-vector transformation for four-conductor systems

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2000
A. Ferrero
Linear transformations are often employed in the study of three-phase systems, since they allow for simplifying the equations describing the system behaviour. Among them, the Fortescue, Clarke and Park transformations are very widely employed. In particular, the last one leads to the formulation of the Space-Vector theory, that is currently employed in the fields of AC machine theory, power definitions and active filtering. The greatest limitation in the use of these transformations is that they are restricted to systems with only three conductors. However, four-conductor systems are often present in the common practice of the electric systems and the application of the Space- Vector theory to such systems is not as straightforward as in the case of the three-conductor systems: a zero-sequence quantity must be considered separately. This paper proposes a linear transformation that extends the properties of the Space- Vector theory to four-conductor systems, and includes the Park transformation as a special case. The mathematical derivation of this new transformation is reported, and its application is discussed by means of some examples. [source]

Ankerung im Untertagebau , Entwicklungen in Theorie und Praxis

GEOMECHANICS AND TUNNELLING, Issue 5 2008
Stefan Kainrath-Reumayer Dipl.-Ing.
Die systematische Ankerung des Gebirges stellt ein wesentliches Verfahren zur Stabilisierung unterirdischer Hohlraumbauten dar. Die geschichtliche Entwicklung verschiedener Ankersysteme wird kurz vorgestellt und Unterteilungsmöglichkeiten werden aufgezeigt. Unterschiedliche Ansätze der Systemankerungen in analytischen und numerischen Berechnungen werden mit der diskreten Modellierung des Gesamtssystems in numerischen Berechnungen mit FLAC3D verglichen. Der Einfluss von Systemankerungen auf das Systemverhalten ist von einer Reihe von Randbedingungen abhängig, der Erfolg der Anwendung oftmals von den verwendeten Ankersystemen. Extreme Spannungszustände im Gebirge stellen hohe Anforderungen an die Methodik der Gebirgsankerung in Untertagebauwerken, die mit den herkömmlichen Ankerungssystemen nur eher unzufriedenstellend zu bewältigen sind. In Abhängigkeit von den Eigenschaften des Gebirges ist unter solch hohen, die Festigkeit des intakten Gebirges meist bereits überschreitenden Spannungszuständen mit großen Verschiebungen, Stabilitätsproblemen sowie Bergschlagphänomenen zu rechnen. Um diesen Anforderungen bestmöglich gerecht zu werden, wird ein neuartiger, energieabsorbierender Ankertyp "Roofex" vorgestellt, der sowohl unter langsam kriechenden, statischen, wie auch abrupten, dynamischen Beanspruchungen einen kontrollierbaren und konstanten Widerstand entlang eines definierten Gleitwegs aufweist. Rock bolting in subsurface constructions , developments in theory and praxis The systematic bolting of rock is a key support element in NATM tunnelling. A short review on the historical development and methods of classification is presented. Different methods of implementation in analytical and numerical calculations are compared to the discrete modelling of the system via FLAC 3D. The influence of the systematic rock bolting to the system behaviour is dependent on many boundary conditions, the success often depends on the used rock bolting techniques. High rock mass stress conditions in underground excavations are serious challenges for rock bolting systems, where conventional bolting systems can only cope with in an rather unsatisfactory way. Depending on the rock mass conditions, high stresses, which mostly exceed already the intact rock mass strength, will lead to serious stability problems, high deformation rates and rockburst phenomena. To provide the mining and tunnelling industry with a rock reinforcement fixture that is better suited to mining with high stress conditions, Atlas Copco GDE designed a new, energy absorbing rock bolt "Roofex" that can accommodate both very large displacements (static yielding) and high energy release (dynamic rupture) in the rock mass by offering an accurate pre-set deformation behaviour. [source]

A conceptual model of preferential flow systems in forested hillslopes: evidence of self-organization

HYDROLOGICAL PROCESSES, Issue 10 2001
Roy C. Sidle
Abstract Preferential flow paths are known to be important conduits of subsurface stormflow in forest hillslopes. Earlier research on preferential flow paths focused on vertical transport; however, lateral transport is also evident in steep forested slopes underlain by bedrock or till. Macropores consisting of decayed and live roots, subsurface erosion, surface bedrock fractures, and animal burrows form the basis of a ,backbone' for lateral preferential flow in such sites. Evidence from field studies in Japan indicates that although individual macropore segments are generally <0·5 m in length, they have a tendency to self-organize into larger preferential flow systems as sites become wetter. Staining tests show clear evidence of interconnected macropore flow segments, including: flow within decayed root channels and subsurface erosion cavities; flow in small depressions of the bedrock substrate; fracture flow in weathered bedrock; exchange between macropores and mesopores; and flow at the organic horizon,mineral soil interface and in buried pockets of organic material and loose soil. Here we develop a three-dimensional model for preferential flow systems based on distributed attributes of macropores and potential connecting nodes (e.g. zones of loose soil and buried organic matter). We postulate that the spatially variable and non-linear preferential flow response observed at our Japan field site, as well as at other sites, is attributed to discrete segments of macropores connecting at various nodes within the regolith. Each node is activated by local soil water conditions and is influenced strongly by soil depth, permeability, pore size, organic matter distribution, surface and substrate topography, and possibly momentum dissipation. This study represents the first attempt to characterize the spatially distributed nature of preferential flow paths at the hillslope scale and presents strong evidence that these networks exhibit complex system behaviour. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Heating and cooling energy recovery for an HVAC system: Economic analysis for the Italian climate

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2001
Adolfo Palombo
Abstract In this paper the economic analysis of the energy recovery in all-outdoor-air HVAC systems for the Italian climate is performed. The energy recovery device considered here is the same for both heating and cooling periods. During the summer season, the energy saving is achieved by evaporative cooling. The performances of the hybrid innovative HVAC system and the traditional system are calculated hour by hour by following the test reference year (TRY) profile. Such analysis is carried out taking into account simultaneously, the trend of some climatic indexes computed in order to (i) better understand the influence of climate on the HVAC system behaviour, (ii) obtain a swift feasibility analysis of the energy recovery system and (iii) perform a rough operating cost estimate of the traditional HVAC system. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Dimensioning and optimization of push-to-talk over cellular server

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 1 2008
M. T. Alam
The PoC (push-to-talk over cellular) application allows point-to-point or point-to-multipoint voice communication between mobile network users. The related work over PoC focuses on the performance analysis only and is ignorant about dimensioning a PoC controller to optimize revenue for service providers. In this paper, we dimension a PoC service with the assumption that the network grade of service is provided. The on-demand sessions should have access priority over pre-established sessions. A PoC controller should be able to terminate a PoC session based on an optimal timer. Moreover, the number of simultaneous session initiations by a PoC client is also a configurable parameter. We derived relations to provide access priority to special PoC sessions based on available transmit/receive units (TRU) and threshold level. Load sharing expressions are reported for a PoC controller using the Lagrange multiplier technique. A simple relation to control the PoC session timer is proposed. Finally, the derivation of maximum number of allowable simultaneous sessions is depicted using two-state Markov models. Numerical results have been computed with the corresponding derivation to provide a useful insight into the system behaviour. A PoC service can benefit from these optimal values of our work during the busy hour. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Robust control of multi-axis magnetic bearing systems

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 14 2001
T.-J. Yeh
Abstract This paper proposes robust control schemes for multi-axis magnetic bearing systems under current control and voltage control. The control schemes are based on a model which characterizes not only the electromagnetic interaction but also secondary effects such as flux leakage, fringing fluxes, and finite core permeance in the magnetic bearing. In the current control case, a sliding-mode-based robust controller, whose control parameters have to be deliberately chosen to account for the uni-directionality of magnetic forces, is proposed to provide robust performance against uncertain dynamics. In the voltage control case, a control scheme that combines the sliding methodology and the backstepping technique is used to provide robust performance under the influence of the electrical dynamics. It is demonstrated through simulations and experiments that, because the nonlinearity and the uncertainty inherently residing in the system behaviour are directly tackled, the proposed controllers achieve superior tracking performances compared to control lers based on linearization. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Efficient IP-multicast via Inmarsat BGAN, a 3GPP satellite network

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2007
Paul Febvre
Abstract This paper outlines a number of challenges associated with supporting IP-multicast services efficiently across the Inmarsat Broadband Global Area Network (BGAN) 3GPP-based satellite network operating over the Imarsat-4 satellite constellation. The paper presents a network architecture that extends the 3GPP reference architecture to allow IP-multicast to be delivered when the Core Network is in a 3GPP Release-4 (non-MBMS compliant) configuration. This paper further extends the service and system concepts defined in 3GPP MBMS to provide improved flexibility and accountability, and improved scalability and efficiency when operating with the Inmarsat-4 BGAN TDM/TDMA air interface. This paper describes a number of radio resource management techniques that were deployed in a test system and the validation testing that was undertaken to support multimedia distribution and VoIP-based netted communications applications. The tuning of application and system behaviour to achieve acceptable performance is described in outline. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A systems analysis of soil and forest degradation in a mid-hill watershed of Nepal using a bio-economic model

LAND DEGRADATION AND DEVELOPMENT, Issue 5 2005
B. K. Sitaula
Abstract Forest degradation, manifested through decline in forest cover, and the resulting soil erosion and organic carbon losses, is a serious problem caused by a complex coupling of bio-physical, socio-economic and technological factors in the Himalayan watersheds. Greater understanding of the linkages between these factors requires a systems approach. We have proposed such an approach using a bio-economic model to explore the system behaviour of forest degradation, soil erosion, and soil C losses in the forest areas. The outcome of the model simulation over a 20-year period indicates that soil erosion and C loss rates may increase more than four-fold by the year 2020 under the existing socio-economic and biophysical regime (the base scenario). Reductions in the population growth rate, introduction of improved agricultural technology and increase in the prices of major agricultural crops can help slow down the rates of forest decline, soil erosion and C loss or even stabilize or reverse them. The results suggest that economic incentives may be highly effective in the reduction of soil loss, as well as C release to the atmosphere. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Kinks and rotations in long Josephson junctions

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 15 2001
Wolfgang Hauck
Abstract Kinks and rotations are studied in long Josephson junctions for small and large surface losses. Geometric singular perturbation theory is used to prove existence for small surface losses, while numerical continuation is necessary to handle large surface losses. A survey of the system behaviour in terms of dissipation parameters and bias current is given. Linear orbital stability for kinks is proved for small surface losses by calculating the spectrum of the linearized problem. The spectrum is split into essential spectrum and discrete spectrum. For the determination of the discrete spectrum, robustness of exponential dichotomies is used. Puiseux series together with perturbation theory for linear operators are an essential tool. In a final step, a smooth Evans function together with geometric singular perturbation theory is used to count eigenvalues. For kinks, non-linear orbital stability is shown. For this purpose, the asymptotic behaviour of a semigroup is given and the theory of centre and stable manifolds is applied. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Statistical investigation of the nonlinear dynamical behavior of offshore structures

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008
Jürgen Reimers
The increasing amount of reports concerning damages of ships, structures and loss of cargo due to wave structure interaction demand the development of systems to predict critical situations in the offshore environment. Within the last years, research has been done to predict encounter with critical wave or wave groups such as "rogue waves" or the so,called "three sisters". The aim of such research is to develop programs that predict dangerous incidents and possibly alert the crew in time. The dangers of such extreme wave situations are severe, but occurrence of them is rather rare. Additionally and more often, structures are endangered because of fluid,structure,interaction leading to critical dynamical system behaviour in a wave environment that shows no extreme wave heights. The severeness of these incidents then depends on the experience and correctness of decision concerning the evasive actions of the master and his crew. Taking nonlinear effects into account, the statistical investigation of structures in waves shows critical behaviour of ships and structures without the absolute necessity of heavy sea conditions or the occurrence of dangerous sea phenomena. This paper describes the development of a program that uses a Monte,Carlo,Simulation technique based on a common panel,method for the creation of added masses and added dampings to predict the behaviour of the structure in several wave conditions. It shows possible ways to prevent the occurrence using similar early warning systems to those in development for critical wavegroups. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Systemverhalten und Prozessoptimierung beim Erddruckschild

Integrative functional genomics of salt acclimatization in the model legume Lotus japonicus

THE PLANT JOURNAL, Issue 6 2008
Diego H. Sanchez
Summary The model legume Lotus japonicus was subjected to non-lethal long-term salinity and profiled at the ionomic, transcriptomic and metabolomic levels. Two experimental designs with various stress doses were tested: a gradual step acclimatization and an initial acclimatization approach. Ionomic profiling by inductively coupled plasma/atomic emission spectrometry (ICP-AES) revealed salt stress-induced reductions in potassium, phosphorus, sulphur, zinc and molybdenum. Microarray profiling using the Lotus Genechip® allowed the identification of 912 probesets that were differentially expressed under the acclimatization regimes. Gas chromatography/mass spectrometry-based metabolite profiling identified 147 differentially accumulated soluble metabolites, indicating a change in metabolic phenotype upon salt acclimatization. Metabolic changes were characterized by a general increase in the steady-state levels of many amino acids, sugars and polyols, with a concurrent decrease in most organic acids. Transcript and metabolite changes exhibited a stress dose-dependent response within the range of NaCl concentrations used, although threshold and plateau behaviours were also observed. The combined observations suggest a successive and increasingly global requirement for the reprogramming of gene expression and metabolic pathways to maintain ionic and osmotic homeostasis. A simple qualitative model is proposed to explain the systems behaviour of plants during salt acclimatization. [source]