Power electronics reliability analysis.
Energy Technology Data Exchange (ETDEWEB)
Smith, Mark A.; Atcitty, Stanley
2009-12-01
This report provides the DOE and industry with a general process for analyzing power electronics reliability. The analysis can help with understanding the main causes of failures, downtime, and cost and how to reduce them. One approach is to collect field maintenance data and use it directly to calculate reliability metrics related to each cause. Another approach is to model the functional structure of the equipment using a fault tree to derive system reliability from component reliability. Analysis of a fictitious device demonstrates the latter process. Optimization can use the resulting baseline model to decide how to improve reliability and/or lower costs. It is recommended that both electric utilities and equipment manufacturers make provisions to collect and share data in order to lay the groundwork for improving reliability into the future. Reliability analysis helps guide reliability improvements in hardware and software technology including condition monitoring and prognostics and health management.
Systems reliability/structural reliability
International Nuclear Information System (INIS)
Green, A.E.
1980-01-01
The question of reliability technology using quantified techniques is considered for systems and structures. Systems reliability analysis has progressed to a viable and proven methodology whereas this has yet to be fully achieved for large scale structures. Structural loading variants over the half-time of the plant are considered to be more difficult to analyse than for systems, even though a relatively crude model may be a necessary starting point. Various reliability characteristics and environmental conditions are considered which enter this problem. The rare event situation is briefly mentioned together with aspects of proof testing and normal and upset loading conditions. (orig.)
Reliability of electronic systems
International Nuclear Information System (INIS)
Roca, Jose L.
2001-01-01
Reliability techniques have been developed subsequently as a need of the diverse engineering disciplines, nevertheless they are not few those that think they have been work a lot on reliability before the same word was used in the current context. Military, space and nuclear industries were the first ones that have been involved in this topic, however not only in these environments it is that it has been carried out this small great revolution in benefit of the increase of the reliability figures of the products of those industries, but rather it has extended to the whole industry. The fact of the massive production, characteristic of the current industries, drove four decades ago, to the fall of the reliability of its products, on one hand, because the massively itself and, for other, to the recently discovered and even not stabilized industrial techniques. Industry should be changed according to those two new requirements, creating products of medium complexity and assuring an enough reliability appropriated to production costs and controls. Reliability began to be integral part of the manufactured product. Facing this philosophy, the book describes reliability techniques applied to electronics systems and provides a coherent and rigorous framework for these diverse activities providing a unifying scientific basis for the entire subject. It consists of eight chapters plus a lot of statistical tables and an extensive annotated bibliography. Chapters embrace the following topics: 1- Introduction to Reliability; 2- Basic Mathematical Concepts; 3- Catastrophic Failure Models; 4-Parametric Failure Models; 5- Systems Reliability; 6- Reliability in Design and Project; 7- Reliability Tests; 8- Software Reliability. This book is in Spanish language and has a potentially diverse audience as a text book from academic to industrial courses. (author)
Electronic structure of BN-aromatics: Choice of reliable computational tools
Mazière, Audrey; Chrostowska, Anna; Darrigan, Clovis; Dargelos, Alain; Graciaa, Alain; Chermette, Henry
2017-10-01
The importance of having reliable calculation tools to interpret and predict the electronic properties of BN-aromatics is directly linked to the growing interest for these very promising new systems in the field of materials science, biomedical research, or energy sustainability. Ionization energy (IE) is one of the most important parameters to approach the electronic structure of molecules. It can be theoretically estimated, but in order to evaluate their persistence and propose the most reliable tools for the evaluation of different electronic properties of existent or only imagined BN-containing compounds, we took as reference experimental values of ionization energies provided by ultra-violet photoelectron spectroscopy (UV-PES) in gas phase—the only technique giving access to the energy levels of filled molecular orbitals. Thus, a set of 21 aromatic molecules containing B-N bonds and B-N-B patterns has been merged for a comparison between experimental IEs obtained by UV-PES and various theoretical approaches for their estimation. Time-Dependent Density Functional Theory (TD-DFT) methods using B3LYP and long-range corrected CAM-B3LYP functionals are used, combined with the Δ SCF approach, and compared with electron propagator theory such as outer valence Green's function (OVGF, P3) and symmetry adapted cluster-configuration interaction ab initio methods. Direct Kohn-Sham estimation and "corrected" Kohn-Sham estimation are also given. The deviation between experimental and theoretical values is computed for each molecule, and a statistical study is performed over the average and the root mean square for the whole set and sub-sets of molecules. It is shown that (i) Δ SCF+TDDFT(CAM-B3LYP), OVGF, and P3 are the most efficient way for a good agreement with UV-PES values, (ii) a CAM-B3LYP range-separated hybrid functional is significantly better than B3LYP for the purpose, especially for extended conjugated systems, and (iii) the "corrected" Kohn-Sham result is a
International Nuclear Information System (INIS)
Baek, Kyunghyun; Jang, Kyungsoo; Lee, Youn-Jung; Ryu, Kyungyul; Choi, Woojin; Kim, Doyoung; Yi, Junsin
2013-01-01
We report the effect of silver (Ag)-buffer layer Indium-Tin-Oxide (ITO) film on a polyethylene terephthalate substrate on the electrical, optical and reliable properties for transparent–flexible displays. The electrical and optical characteristics of an ITO-only film and an Ag-layer-inserted ITO film are measured and compared to assess the applicability of the triple layered structure in flexible displays. The sheet resistance, the resistivity and the light transmittance of the ITO-only film were 400 Ω/sq, 1.33 × 10 −3 Ω-cm and 99.2%, while those of the ITO film inserted with a 10 nm thick Ag layer were 165 Ω/sq, 4.78 × 10 −4 Ω-cm and about 97%, respectively. To evaluate the mechanical reliability of the different ITO films, bending tests were carried out. After the dynamic bending test of 900 cycles, the sheet resistance of the ITO film inserted with the Ag layer changed from 154 Ω/sq to 475 Ω/sq, about a 3-time increase but that of the ITO-only film changed from 400 Ω/sq to 61,986 Ω/sq, about 150-time increase. When the radius is changed from 25 mm to 20 mm in the static bending test, the sheet resistance of the ITO-only film changed from 400 to 678.3 linearly whereas that of the Ag-layer inserted ITO film changed a little from 154.4 to 154.9. These results show that Ag-layer inserted ITO film had better mechanical characteristics than the ITO-only film. - Highlights: ► Transparent flexible electrode fabricated on glass substrate. ► Electrode fabricated using vertically-patterned design on glass substrate. ► Optimization of the vertical patterns ► Application of the vertically-patterned electrode in transparent–flexible electronics
Electronics reliability calculation and design
Dummer, Geoffrey W A; Hiller, N
1966-01-01
Electronics Reliability-Calculation and Design provides an introduction to the fundamental concepts of reliability. The increasing complexity of electronic equipment has made problems in designing and manufacturing a reliable product more and more difficult. Specific techniques have been developed that enable designers to integrate reliability into their products, and reliability has become a science in its own right. The book begins with a discussion of basic mathematical and statistical concepts, including arithmetic mean, frequency distribution, median and mode, scatter or dispersion of mea
Field reliability of electronic systems
International Nuclear Information System (INIS)
Elm, T.
1984-02-01
This report investigates, through several examples from the field, the reliability of electronic units in a broader sense. That is, it treats not just random parts failure, but also inadequate reliability design and (externally and internally) induced failures. The report is not meant to be merely an indication of the state of the art for the reliability prediction methods we know, but also as a contribution to the investigation of man-machine interplay in the operation and repair of electronic equipment. The report firmly links electronics reliability to safety and risk analyses approaches with a broader, system oriented view of reliability prediction and with postfailure stress analysis. It is intended to reveal, in a qualitative manner, the existence of symptom and cause patterns. It provides a background for further investigations to identify the detailed mechanisms of the faults and the remedical actions and precautions for achieving cost effective reliability. (author)
Structural Reliability Methods
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager; Madsen, H. O.
The structural reliability methods quantitatively treat the uncertainty of predicting the behaviour and properties of a structure given the uncertain properties of its geometry, materials, and the actions it is supposed to withstand. This book addresses the probabilistic methods for evaluation...... of structural reliability, including the theoretical basis for these methods. Partial safety factor codes under current practice are briefly introduced and discussed. A probabilistic code format for obtaining a formal reliability evaluation system that catches the most essential features of the nature...... of the uncertainties and their interplay is the developed, step-by-step. The concepts presented are illustrated by numerous examples throughout the text....
Power Electronics Packaging Reliability | Transportation Research | NREL
Packaging Reliability Power Electronics Packaging Reliability A photo of a piece of power electronics laboratory equipment. NREL power electronics packaging reliability research investigates the electronics packaging around a semiconductor switching device determines the electrical, thermal, and
Structural systems reliability analysis
International Nuclear Information System (INIS)
Frangopol, D.
1975-01-01
For an exact evaluation of the reliability of a structure it appears necessary to determine the distribution densities of the loads and resistances and to calculate the correlation coefficients between loads and between resistances. These statistical characteristics can be obtained only on the basis of a long activity period. In case that such studies are missing the statistical properties formulated here give upper and lower bounds of the reliability. (orig./HP) [de
Component reliability for electronic systems
Bajenescu, Titu-Marius I
2010-01-01
The main reason for the premature breakdown of today's electronic products (computers, cars, tools, appliances, etc.) is the failure of the components used to build these products. Today professionals are looking for effective ways to minimize the degradation of electronic components to help ensure longer-lasting, more technically sound products and systems. This practical book offers engineers specific guidance on how to design more reliable components and build more reliable electronic systems. Professionals learn how to optimize a virtual component prototype, accurately monitor product reliability during the entire production process, and add the burn-in and selection procedures that are the most appropriate for the intended applications. Moreover, the book helps system designers ensure that all components are correctly applied, margins are adequate, wear-out failure modes are prevented during the expected duration of life, and system interfaces cannot lead to failure.
Reliability based structural design
Vrouwenvelder, A.C.W.M.
2014-01-01
According to ISO 2394, structures shall be designed, constructed and maintained in such a way that they are suited for their use during the design working life in an economic way. To fulfil this requirement one needs insight into the risk and reliability under expected and non-expected actions. A
Reliability of Power Electronic Converter Systems
DEFF Research Database (Denmark)
-link capacitance in power electronic converter systems; wind turbine systems; smart control strategies for improved reliability of power electronics system; lifetime modelling; power module lifetime test and state monitoring; tools for performance and reliability analysis of power electronics systems; fault...... for advancing the reliability, availability, system robustness, and maintainability of PECS at different levels of complexity. Drawing on the experience of an international team of experts, this book explores the reliability of PECS covering topics including an introduction to reliability engineering in power...... electronic converter systems; anomaly detection and remaining-life prediction for power electronics; reliability of DC-link capacitors in power electronic converters; reliability of power electronics packaging; modeling for life-time prediction of power semiconductor modules; minimization of DC...
Structural Optimization with Reliability Constraints
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1986-01-01
During the last 25 years considerable progress has been made in the fields of structural optimization and structural reliability theory. In classical deterministic structural optimization all variables are assumed to be deterministic. Due to the unpredictability of loads and strengths of actual......]. In this paper we consider only structures which can be modelled as systems of elasto-plastic elements, e.g. frame and truss structures. In section 2 a method to evaluate the reliability of such structural systems is presented. Based on a probabilistic point of view a modern structural optimization problem...... is formulated in section 3. The formulation is a natural extension of the commonly used formulations in determinstic structural optimization. The mathematical form of the optimization problem is briefly discussed. In section 4 two new optimization procedures especially designed for the reliability...
Design for Reliability of Power Electronic Systems
DEFF Research Database (Denmark)
Wang, Huai; Ma, Ke; Blaabjerg, Frede
2012-01-01
Advances in power electronics enable efficient and flexible processing of electric power in the application of renewable energy sources, electric vehicles, adjustable-speed drives, etc. More and more efforts are devoted to better power electronic systems in terms of reliability to ensure high......). A collection of methodologies based on Physics-of-Failure (PoF) approach and mission profile analysis are presented in this paper to perform reliability-oriented design of power electronic systems. The corresponding design procedures and reliability prediction models are provided. Further on, a case study...... on a 2.3 MW wind power converter is discussed with emphasis on the reliability critical components IGBTs. Different aspects of improving the reliability of the power converter are mapped. Finally, the challenges and opportunities to achieve more reliable power electronic systems are addressed....
Reliability Based Ship Structural Design
DEFF Research Database (Denmark)
Dogliani, M.; Østergaard, C.; Parmentier, G.
1996-01-01
This paper deals with the development of different methods that allow the reliability-based design of ship structures to be transferred from the area of research to the systematic application in current design. It summarises the achievements of a three-year collaborative research project dealing...... with developments of models of load effects and of structural collapse adopted in reliability formulations which aim at calibrating partial safety factors for ship structural design. New probabilistic models of still-water load effects are developed both for tankers and for containerships. New results are presented...... structure of several tankers and containerships. The results of the reliability analysis were the basis for the definition of a target safety level which was used to asses the partial safety factors suitable for in a new design rules format to be adopted in modern ship structural design. Finally...
Reliability-Based Optimization in Structural Engineering
DEFF Research Database (Denmark)
Enevoldsen, I.; Sørensen, John Dalsgaard
1994-01-01
In this paper reliability-based optimization problems in structural engineering are formulated on the basis of the classical decision theory. Several formulations are presented: Reliability-based optimal design of structural systems with component or systems reliability constraints, reliability...
System Reliability of Timber Structures
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Sørensen, John Dalsgaard
2010-01-01
elements, alternate load path(s) etc. in the structural design. In general these characteristics can have a positive influence on system reliability of a structure however, in Eurocodes ductility is only awarded for concrete and steel structures but not for timber structures. It is well......-know that structural systems can redistribute internal forces due to ductility of a connection, i.e. some additional loads can be carried by the structure. The same effect is also possible for reinforced concrete structures and structures of steel. However, for timber structures codes do not award that ductility......For reduction of the risk of collapse in the event of loss of structural element(s), a structural engineer may take necessary steps to design a collapse-resistant structure that is insensitive to accidental circumstances e.g. by incorporating characteristics like redundancy, ties, ductility, key...
Reliability of power electronic converter systems
Chung, Henry Shu-hung; Blaabjerg, Frede; Pecht, Michael
2016-01-01
This book outlines current research into the scientific modeling, experimentation, and remedial measures for advancing the reliability, availability, system robustness, and maintainability of Power Electronic Converter Systems (PECS) at different levels of complexity.
On the NPP structural reliability
International Nuclear Information System (INIS)
Klemin, A.I.; Polyakov, E.F.
1980-01-01
Reviewed are the main statements peculiarities and possibilities of the first branch guiding technical material (GTM) ''The methods of calculation of structural reliability of NPP and its systems at the stage of projecting''. It is stated, that in GTM presented are recomendations on the calculation of reliability of such specific systems, as the system of the reactor control and protection the system of measuring instruments and automatics and safe systems. GTM are based on analytical methods of modern theory of realibility with the Use of metodology of minimal cross sections of complex systems. It is stressed, that the calculations on the proposed methods permit to calculate a wide complex of reliability parameters, reflecting separately or together prorerties of NPP dependability and maintainability. For NPP, operating by a variable schedule of leading, aditionally considered are parameters, characterizing reliability with account of the proposed regime of power change, i.e. taking into account failures, caused by decrease of the obtained power lower, than the reguired or increase of the required power higher, than the obtained
Structural reliability assessment capability in NESSUS
Millwater, H.; Wu, Y.-T.
1992-07-01
The principal capabilities of NESSUS (Numerical Evaluation of Stochastic Structures Under Stress), an advanced computer code developed for probabilistic structural response analysis, are reviewed, and its structural reliability assessed. The code combines flexible structural modeling tools with advanced probabilistic algorithms in order to compute probabilistic structural response and resistance, component reliability and risk, and system reliability and risk. An illustrative numerical example is presented.
Design for Reliability of Power Electronic Systems
DEFF Research Database (Denmark)
Yang, Yongheng; Wang, Huai; Sangwongwanich, Ariya
2018-01-01
Power density, efficiency, cost, and reliability are the major challenges when designing a power electronic system. Latest advancements in power semiconductor devices (e.g., silicon carbide devices) and topological innovations have vital contributions to power density and efficiency. Nevertheless......, dedicated heat sink systems for thermal management are required to dissipate the power losses in power electronic systems; otherwise, the power devices will be heated up and eventually fail to operate. In addition, in many mission critical applications (e.g., marine systems), the operating condition (i...
Reliability Issues and Solutions in Flexible Electronics Under Mechanical Fatigue
Yi, Seol-Min; Choi, In-Suk; Kim, Byoung-Joon; Joo, Young-Chang
2018-03-01
Flexible devices are of significant interest due to their potential expansion of the application of smart devices into various fields, such as energy harvesting, biological applications and consumer electronics. Due to the mechanically dynamic operations of flexible electronics, their mechanical reliability must be thoroughly investigated to understand their failure mechanisms and lifetimes. Reliability issue caused by bending fatigue, one of the typical operational limitations of flexible electronics, has been studied using various test methodologies; however, electromechanical evaluations which are essential to assess the reliability of electronic devices for flexible applications had not been investigated because the testing method was not established. By employing the in situ bending fatigue test, we has studied the failure mechanism for various conditions and parameters, such as bending strain, fatigue area, film thickness, and lateral dimensions. Moreover, various methods for improving the bending reliability have been developed based on the failure mechanism. Nanostructures such as holes, pores, wires and composites of nanoparticles and nanotubes have been suggested for better reliability. Flexible devices were also investigated to find the potential failures initiated by complex structures under bending fatigue strain. In this review, the recent advances in test methodology, mechanism studies, and practical applications are introduced. Additionally, perspectives including the future advance to stretchable electronics are discussed based on the current achievements in research.
Dependent systems reliability estimation by structural reliability approach
DEFF Research Database (Denmark)
Kostandyan, Erik; Sørensen, John Dalsgaard
2014-01-01
Estimation of system reliability by classical system reliability methods generally assumes that the components are statistically independent, thus limiting its applicability in many practical situations. A method is proposed for estimation of the system reliability with dependent components, where...... the leading failure mechanism(s) is described by physics of failure model(s). The proposed method is based on structural reliability techniques and accounts for both statistical and failure effect correlations. It is assumed that failure of any component is due to increasing damage (fatigue phenomena...... identification. Application of the proposed method can be found in many real world systems....
Reliability and optimization of structural systems
International Nuclear Information System (INIS)
Thoft-Christensen, P.
1987-01-01
The proceedings contain 28 papers presented at the 1st working conference. The working conference was organized by the IFIP Working Group 7.5. The proceedings also include 4 papers which were submitted, but for various reasons not presented at the working conference. The working conference was attended by 50 participants from 18 countries. The conference was the first scientific meeting of the new IFIP Working Group 7.5 on 'Reliability and Optimization of Structural Systems'. The purpose of the Working Group 7.5 is to promote modern structural system optimization and reliability theory, to advance international cooperation in the field of structural system optimization and reliability theory, to stimulate research, development and application of structural system optimization and reliability theory, to further the dissemination and exchange of information on reliability and optimization of structural system optimization and reliability theory, and to encourage education in structural system optimization and reliability theory. (orig./HP)
Reliability-based optimization of engineering structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2008-01-01
The theoretical basis for reliability-based structural optimization within the framework of Bayesian statistical decision theory is briefly described. Reliability-based cost benefit problems are formulated and exemplitied with structural optimization. The basic reliability-based optimization...... problems are generalized to the following extensions: interactive optimization, inspection and repair costs, systematic reconstruction, re-assessment of existing structures. Illustrative examples are presented including a simple introductory example, a decision problem related to bridge re...
Reliable design of electronic equipment an engineering guide
Natarajan, Dhanasekharan
2014-01-01
This book explains reliability techniques with examples from electronics design for the benefit of engineers. It presents the application of de-rating, FMEA, overstress analyses and reliability improvement tests for designing reliable electronic equipment. Adequate information is provided for designing computerized reliability database system to support the application of the techniques by designers. Pedantic terms and the associated mathematics of reliability engineering discipline are excluded for the benefit of comprehensiveness and practical applications. This book offers excellent support
Reliability Based Optimization of Structural Systems
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
1987-01-01
The optimization problem to design structural systems such that the reliability is satisfactory during the whole lifetime of the structure is considered in this paper. Some of the quantities modelling the loads and the strength of the structure are modelled as random variables. The reliability...... is estimated using first. order reliability methods ( FORM ). The design problem is formulated as the optimization problem to minimize a given cost function such that the reliability of the single elements satisfies given requirements or such that the systems reliability satisfies a given requirement....... For these optimization problems it is described how a sensitivity analysis can be performed. Next, new optimization procedures to solve the optimization problems are presented. Two of these procedures solve the system reliability based optimization problem sequentially using quasi-analytical derivatives. Finally...
On industrial application of structural reliability theory
Energy Technology Data Exchange (ETDEWEB)
Thoft-Christensen, P
1998-06-01
In this paper it is shown that modern structural reliability theory is being successfully applied to a number of different industries. This review of papers is in no way complete. In the literature there is a large number of similar applications and also application not touched on in this presentation. There has been some concern among scientists from this area that structural reliability theory is not being used by industry. It is probably correct that structural reliability theory is not being used by industry as much as it should be used. However, the work by the ESReDA Working Group clearly shows the vary wide application of structural reliability theory by many different industries. One must also have in mind that industry often is reluctant to publish data related to safety and reliability. (au) 32 refs.
On industrial application of structural reliability theory
International Nuclear Information System (INIS)
Thoft-Christensen, P.
1998-01-01
In this paper it is shown that modern structural reliability theory is being successfully applied to a number of different industries. This review of papers is in no way complete. In the literature there is a large number of similar applications and also application not touched on in this presentation. There has been some concern among scientists from this area that structural reliability theory is not being used by industry. It is probably correct that structural reliability theory is not being used by industry as much as it should be used. However, the work by the ESReDA Working Group clearly shows the vary wide application of structural reliability theory by many different industries. One must also have in mind that industry often is reluctant to publish data related to safety and reliability. (au)
Reliability analysis and assessment of structural systems
International Nuclear Information System (INIS)
Yao, J.T.P.; Anderson, C.A.
1977-01-01
The study of structural reliability deals with the probability of having satisfactory performance of the structure under consideration within any specific time period. To pursue this study, it is necessary to apply available knowledge and methodology in structural analysis (including dynamics) and design, behavior of materials and structures, experimental mechanics, and the theory of probability and statistics. In addition, various severe loading phenomena such as strong motion earthquakes and wind storms are important considerations. For three decades now, much work has been done on reliability analysis of structures, and during this past decade, certain so-called 'Level I' reliability-based design codes have been proposed and are in various stages of implementation. These contributions will be critically reviewed and summarized in this paper. Because of the undesirable consequences resulting from the failure of nuclear structures, it is important and desirable to consider the structural reliability in the analysis and design of these structures. Moreover, after these nuclear structures are constructed, it is desirable for engineers to be able to assess the structural reliability periodically as well as immediately following the occurrence of severe loading conditions such as a strong-motion earthquake. During this past decade, increasing use has been made of techniques of system identification in structural engineering. On the basis of non-destructive test results, various methods have been developed to obtain an adequate mathematical model (such as the equations of motion with more realistic parameters) to represent the structural system
Structural Reliability of Wind Turbine Blades
DEFF Research Database (Denmark)
Dimitrov, Nikolay Krasimirov
turbine blades. The main purpose is to draw a clear picture of how reliability-based design of wind turbines can be done in practice. The objectives of the thesis are to create methodologies for efficient reliability assessment of composite materials and composite wind turbine blades, and to map...... the uncertainties in the processes, materials and external conditions that have an effect on the health of a composite structure. The study considers all stages in a reliability analysis, from defining models of structural components to obtaining the reliability index and calibration of partial safety factors...... by developing new models and standards or carrying out tests The following aspects are covered in detail: ⋅ The probabilistic aspects of ultimate strength of composite laminates are addressed. Laminated plates are considered as a general structural reliability system where each layer in a laminate is a separate...
A Reliability-Oriented Design Method for Power Electronic Converters
DEFF Research Database (Denmark)
Wang, Huai; Zhou, Dao; Blaabjerg, Frede
2013-01-01
Reliability is a crucial performance indicator of power electronic systems in terms of availability, mission accomplishment and life cycle cost. A paradigm shift in the research on reliability of power electronics is going on from simple handbook based calculations (e.g. models in MIL-HDBK-217F h...... and reliability prediction models are provided. A case study on a 2.3 MW wind power converter is discussed with emphasis on the reliability critical component IGBT modules....
Reliability of structural systems subject to fatigue
International Nuclear Information System (INIS)
Rackwitz, R.
1984-01-01
Concepts and computational procedures for the reliability calculation of structural systems subject to fatigue are outlined. Systems are dealt with by approximately computing componential times to first failure. So-called first-order reliability methods are then used to formulate dependencies between componential failures and to evaluate the system failure probability. (Author) [pt
Evaluation of structural reliability using simulation methods
Directory of Open Access Journals (Sweden)
Baballëku Markel
2015-01-01
Full Text Available Eurocode describes the 'index of reliability' as a measure of structural reliability, related to the 'probability of failure'. This paper is focused on the assessment of this index for a reinforced concrete bridge pier. It is rare to explicitly use reliability concepts for design of structures, but the problems of structural engineering are better known through them. Some of the main methods for the estimation of the probability of failure are the exact analytical integration, numerical integration, approximate analytical methods and simulation methods. Monte Carlo Simulation is used in this paper, because it offers a very good tool for the estimation of probability in multivariate functions. Complicated probability and statistics problems are solved through computer aided simulations of a large number of tests. The procedures of structural reliability assessment for the bridge pier and the comparison with the partial factor method of the Eurocodes have been demonstrated in this paper.
Reliability-Based Optimization of Structural Elements
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
In this paper structural elements from an optimization point of view are considered, i.e. only the geometry of a structural element is optimized. Reliability modelling of the structural element is discussed both from an element point of view and from a system point of view. The optimization...
Development in structural systems reliability theory
International Nuclear Information System (INIS)
Murotsu, Y.
1986-01-01
This paper is concerned with two topics on structural systems reliability theory. One covers automatic generation of failure mode equations, identifications of stochastically dominant failure modes, and reliability assessment of redundant structures. Reduced stiffness matrixes and equivalent nodal forces representing the failed elements are introduced for expressing the safety of the elements, using a matrix method. Dominant failure modes are systematically selected by a branch-and-bound technique and heuristic operations. The other discusses the various optimum design problems based on reliability concept. Those problems are interpreted through a solution to a multi-objective optimization problem. (orig.)
Development in structural systems reliability theory
Energy Technology Data Exchange (ETDEWEB)
Murotsu, Y
1986-07-01
This paper is concerned with two topics on structural systems reliability theory. One covers automatic generation of failure mode equations, identifications of stochastically dominant failure modes, and reliability assessment of redundant structures. Reduced stiffness matrixes and equivalent nodal forces representing the failed elements are introduced for expressing the safety of the elements, using a matrix method. Dominant failure modes are systematically selected by a branch-and-bound technique and heuristic operations. The other discusses the various optimum design problems based on reliability concept. Those problems are interpreted through a solution to a multi-objective optimization problem.
Reliability analysis of prestressed concrete containment structures
International Nuclear Information System (INIS)
Jiang, J.; Zhao, Y.; Sun, J.
1993-01-01
The reliability analysis of prestressed concrete containment structures subjected to combinations of static and dynamic loads with consideration of uncertainties of structural and load parameters is presented. Limit state probabilities for given parameters are calculated using the procedure developed at BNL, while that with consideration of parameter uncertainties are calculated by a fast integration for time variant structural reliability. The limit state surface of the prestressed concrete containment is constructed directly incorporating the prestress. The sensitivities of the Choleskey decomposition matrix and the natural vibration character are calculated by simplified procedures. (author)
Reliability-Based Design of Coastal Structures
DEFF Research Database (Denmark)
Burcharth, H. F.
1997-01-01
The objective of this paper is to introduce the application of reliability theory for conceptual design and evaluation of coastal structures. It is without the scope to discuss the validity and quality of the various design formulae available for coastal structures. The contents of the paper is a....... Proceedings Conference of Port and Coastal Engineering in developing countries. Rio de Janeiro, Brazil, 1995....
Structural reliability of atomic power plant
International Nuclear Information System (INIS)
Klemin, A.I.; Polyakov, E.F.
1980-01-01
In 1978 the first specialized technical manual ''Technique of Calculating the Structural Reliability of an Atomic Power Plant and Its Systems in the Design Stage'' was developed. The present article contains information about the main characteristics and capabilities of the manual. The manual gives recommendations concerning the calculations of the reliability of such specific systems as the reactor control and safety system, the system of instrumentation and automatic control, and safety systems. 2 refs
System reliability developments in structural engineering
International Nuclear Information System (INIS)
Moses, F.
1982-01-01
Two major limitations occur in present structural design code developments utilizing reliability theory. The notional system reliabilities may differ significantly from calibrated component reliabilities. Secondly, actual failures are often due to gross errors not reflected in most present code formats. A review is presented of system reliability methods and further new concepts are developed. The incremental load approach for identifying and expressing collapse modes is expanded by employing a strategy to identify and enumerate the significant structural collapse modes. It further isolates the importance of critical components in the system performance. Ductile and brittle component behavior and strength correlation is reflected in the system model and illustrated in several examples. Modal combinations for the system reliability are also reviewed. From these developments a system factor can be addended to component safety checking equations. Values may be derived from system behavior by substituting in a damage model which accounts for the response range from component failure to collapse. Other strategies are discussed which emphasize quality assurance during design and in-service inspection for components whose behavior is critical to the system reliability. (Auth.)
Reliability assessment of nuclear structural systems
International Nuclear Information System (INIS)
Reich, M.; Hwang, H.
1983-01-01
Reliability assessment of nuclear structural systems has been receiving more emphasis over the last few years. This paper deals with the recent progress made by the Structural Analysis Division of Brookhaven National Laboratory (BNL), in the development of a probability-based reliability analysis methodology for safety evaluation of reactor containments and other seismic category I structures. An important feature of this methodology is the incorporation of finite element analysis and random vibration theory. By utilizing this method, it is possible to evaluate the safety of nuclear structures under various static and dynamic loads in terms of limit state probability. Progress in other related areas, such as the establishment of probabilistic characteristics for various loads and structural resistance, are also described. Results of an application of the methodology to a realistic reinforced concrete containment subjected to dead and live loads, accidental internal pressures and earthquake ground accelerations are presented
Structural reliability methods: Code development status
Millwater, Harry R.; Thacker, Ben H.; Wu, Y.-T.; Cruse, T. A.
1991-05-01
The Probabilistic Structures Analysis Method (PSAM) program integrates state of the art probabilistic algorithms with structural analysis methods in order to quantify the behavior of Space Shuttle Main Engine structures subject to uncertain loadings, boundary conditions, material parameters, and geometric conditions. An advanced, efficient probabilistic structural analysis software program, NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) was developed as a deliverable. NESSUS contains a number of integrated software components to perform probabilistic analysis of complex structures. A nonlinear finite element module NESSUS/FEM is used to model the structure and obtain structural sensitivities. Some of the capabilities of NESSUS/FEM are shown. A Fast Probability Integration module NESSUS/FPI estimates the probability given the structural sensitivities. A driver module, PFEM, couples the FEM and FPI. NESSUS, version 5.0, addresses component reliability, resistance, and risk.
Optimal Structural Reliability of Offshore Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Tarp-Johansen, N.J.
2005-01-01
The main failure modes of modern large wind turbines are fatigue failure of wings, hub, shaft and main tower, local buckling of main tower, and failure of the foundation. This paper considers reliability-based optimal design of wind turbines. Compared to onshore wind turbines and building...... structures, humans spent little time in the vicinity of offshore wind turbines and the probability of human injury during storm conditions is small. Further environmental pollution will also in general be small in case of failure. One could therefore argue that the reliability level of offshore wind turbines...... can be lower than for onshore wind turbines and other civil engineering structures and can be assessed by reliability-based cost-optimization. Specifically this paper considers the main tower and foundation. Both fatigue and ultimate strength failure modes are included. Different formulations...
Evaluation criteria of structural steel reliability
International Nuclear Information System (INIS)
Zav'yalov, A.S.
1980-01-01
Different low-carbon and medium-carbon structural steels are investigated. It is stated that steel reliability evaluation criteria depend on the fracture mode, steel suffering from the brittle fracture under the influence of the stresses (despite their great variety) arising in articles during the production and operation. Fibrous steel fracture at the given temperature and article thickness says about its high ductility and toughness and brittle fractures are impossible. Brittle fractures take place in case of a crystalline and mixed fracture with a predominant crystalline component. Evaluation methods of article and sample steel structural strength differing greatly from real articles in a thickness (diameter) or used at temperatures higher than possible operation temperatures cannot be reliability evaluation criteria because at a great thickness (diameter) and lower operation temperatures steel fracture and its strain mode can change resulting in a sharp reliability degradation
Reliability analysis of an offshore structure
DEFF Research Database (Denmark)
Sorensen, J. D.; Faber, M. H.; Thoft-Christensen, P.
1992-01-01
A jacket type offshore structure from the North Sea is considered. The time variant reliability is estimated for failure defined as brittle fracture and crack through the tubular member walls. The stochastic modelling is described. The hot spot stress spectral moments as function of the stochasti...
On Industrial Application of Structural Reliability Theory
DEFF Research Database (Denmark)
Thoft-Christensen, Palle
For the last two decades we have seen an increasing interest in applying structural reliability theory to many different industries. However, the number of real applications is much smaller than what one would expect. At the beginning most applications were in the design/analyses area especially...
Reliability Analysis of Elasto-Plastic Structures
DEFF Research Database (Denmark)
Thoft-Christensen, Palle; Sørensen, John Dalsgaard
1984-01-01
. Failure of this type of system is defined either as formation of a mechanism or by failure of a prescribed number of elements. In the first case failure is independent of the order in which the elements fail, but this is not so by the second definition. The reliability analysis consists of two parts...... are described and the two definitions of failure can be used by the first formulation, but only the failure definition based on formation of a mechanism by the second formulation. The second part of the reliability analysis is an estimate of the failure probability for the structure on the basis...
Materials and Reliability Handbook for Semiconductor Optical and Electron Devices
Pearton, Stephen
2013-01-01
Materials and Reliability Handbook for Semiconductor Optical and Electron Devices provides comprehensive coverage of reliability procedures and approaches for electron and photonic devices. These include lasers and high speed electronics used in cell phones, satellites, data transmission systems and displays. Lifetime predictions for compound semiconductor devices are notoriously inaccurate due to the absence of standard protocols. Manufacturers have relied on extrapolation back to room temperature of accelerated testing at elevated temperature. This technique fails for scaled, high current density devices. Device failure is driven by electric field or current mechanisms or low activation energy processes that are masked by other mechanisms at high temperature. The Handbook addresses reliability engineering for III-V devices, including materials and electrical characterization, reliability testing, and electronic characterization. These are used to develop new simulation technologies for device operation and ...
Electronic structure of silicene
International Nuclear Information System (INIS)
Voon, L. C. Lew Yan
2015-01-01
In this topical review, we discuss the electronic structure of free-standing silicene by comparing results obtained using different theoretical methods. Silicene is a single atomic layer of silicon similar to graphene. The interest in silicene is the same as for graphene, in being two-dimensional and possessing a Dirac cone. One advantage of silicene is due to its compatibility with current silicon electronics. Both empirical and first-principles techniques have been used to study the electronic properties of silicene. We will provide a brief overview of the parameter space for first-principles calculations. However, since the theory is standard, no extensive discussion will be included. Instead, we will emphasize what empirical methods can provide to such investigations and the current state of these theories. Finally, we will review the properties computed using both types of theories for free-standing silicene, with emphasis on areas where we have contributed. Comparisons to graphene is provided throughout. (topical review)
Reliability and Robustness Evaluation of Timber Structures
DEFF Research Database (Denmark)
Cizmar, Dean; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning
In the last few decades there have been intensely research concerning reliability of timber structures. This is primarily because there is an increased focus on society on sustainability and environmental aspects. Modern timber as a building material is also being competitive compared to concrete...... and steel. However, reliability models applied to timber were always related to individual components but not the systems. as any real structure is a complex system, system behaviour must be of a particular interest. In the chapter 1 of this document an overview of stochastic models for strength and loads...... (deterministic, probabilistic and risk based approaches) of the robustness are given. Chapter 3 deals more detailed with the robustness of timber structures....
Structural reliability analysis and seismic risk assessment
International Nuclear Information System (INIS)
Hwang, H.; Reich, M.; Shinozuka, M.
1984-01-01
This paper presents a reliability analysis method for safety evaluation of nuclear structures. By utilizing this method, it is possible to estimate the limit state probability in the lifetime of structures and to generate analytically the fragility curves for PRA studies. The earthquake ground acceleration, in this approach, is represented by a segment of stationary Gaussian process with a zero mean and a Kanai-Tajimi Spectrum. All possible seismic hazard at a site represented by a hazard curve is also taken into consideration. Furthermore, the limit state of a structure is analytically defined and the corresponding limit state surface is then established. Finally, the fragility curve is generated and the limit state probability is evaluated. In this paper, using a realistic reinforced concrete containment as an example, results of the reliability analysis of the containment subjected to dead load, live load and ground earthquake acceleration are presented and a fragility curve for PRA studies is also constructed
International Nuclear Information System (INIS)
Grosso, G.
1986-01-01
The aim of this chapter is to present, in detail, some theoretical methods used to calculate electronic band structures in crystals. The basic strategies employed to attack the problem of electronic-structure calculations are presented. Successive sections present the basic formulations of the tight-binding, orthogonalized-plane-wave, Green'sfunction, and pseudopotential methods with a discussion of their application to perfect solids. Exemplifications in the case of a few selected problems provide further insight by the author into the physical aspects of the different methods and are a guide to the use of their mathematical techniques. A discussion is offered of completely a priori Hartree-Fock calculations and attempts to extend them. Special aspects of the different methods are also discussed in light of recently published related work
Estimation of structural reliability under combined loads
International Nuclear Information System (INIS)
Shinozuka, M.; Kako, T.; Hwang, H.; Brown, P.; Reich, M.
1983-01-01
For the overall safety evaluation of seismic category I structures subjected to various load combinations, a quantitative measure of the structural reliability in terms of a limit state probability can be conveniently used. For this purpose, the reliability analysis method for dynamic loads, which has recently been developed by the authors, was combined with the existing standard reliability analysis procedure for static and quasi-static loads. The significant parameters that enter into the analysis are: the rate at which each load (dead load, accidental internal pressure, earthquake, etc.) will occur, its duration and intensity. All these parameters are basically random variables for most of the loads to be considered. For dynamic loads, the overall intensity is usually characterized not only by their dynamic components but also by their static components. The structure considered in the present paper is a reinforced concrete containment structure subjected to various static and dynamic loads such as dead loads, accidental pressure, earthquake acceleration, etc. Computations are performed to evaluate the limit state probabilities under each load combination separately and also under all possible combinations of such loads
Power Electronic Packaging Design, Assembly Process, Reliability and Modeling
Liu, Yong
2012-01-01
Power Electronic Packaging presents an in-depth overview of power electronic packaging design, assembly,reliability and modeling. Since there is a drastic difference between IC fabrication and power electronic packaging, the book systematically introduces typical power electronic packaging design, assembly, reliability and failure analysis and material selection so readers can clearly understand each task's unique characteristics. Power electronic packaging is one of the fastest growing segments in the power electronic industry, due to the rapid growth of power integrated circuit (IC) fabrication, especially for applications like portable, consumer, home, computing and automotive electronics. This book also covers how advances in both semiconductor content and power advanced package design have helped cause advances in power device capability in recent years. The author extrapolates the most recent trends in the book's areas of focus to highlight where further improvement in materials and techniques can d...
Design for Reliability of Power Electronics in Renewable Energy Systems
DEFF Research Database (Denmark)
Ma, Ke; Yang, Yongheng; Wang, Huai
2014-01-01
Power electronics is the enabling technology for maximizing the power captured from renewable electrical generation, e.g., the wind and solar technology, and also for an efficient integration into the grid. Therefore, it is important that the power electronics are reliable and do not have too many...... failures during operation which otherwise will increase cost for operation, maintenance and reputation. Typically, power electronics in renewable electrical generation has to be designed for 20–30 years of operation, and in order to do that, it is crucial to know about the mission profile of the power...... electronics technology as well as to know how the power electronics technology is loaded in terms of temperature and other stressors relevant, to reliability. Hence, this chapter will show the basics of power electronics technology for renewable energy systems, describe the mission profile of the technology...
Power Electronics and Reliability in Renewable Energy Systems
DEFF Research Database (Denmark)
Blaabjerg, Frede; Ma, Ke; Zhou, Dao
2012-01-01
Power Electronics are needed in almost all kind of renewable energy systems. It is used both for controlling the renewable source and also for interfacing to the load, which can be grid-connected or working in stand-alone mode. More and more efforts are put into making renewable energy systems...... better in terms of reliability in order to ensure a high availability of the power sources, in this case the knowledge of mission profile of a certain application is crucial for the reliability evaluation/design of power electronics. In this paper an overview on the power electronic circuits behind...... the most common converter configurations for wind turbine and photovoltaic is done. Next different aspects of improving the system reliability are mapped. Further on examples of how to control the chip temperature in different power electronic configurations as well as operation modes for wind power...
The electronic structures of solids
Coles, B R
2013-01-01
The Electronic Structures of Solids aims to provide students of solid state physics with the essential concepts they will need in considering properties of solids that depend on their electronic structures and idea of the electronic character of particular materials and groups of materials. The book first discusses the electronic structure of atoms, including hydrogen atom and many-electron atom. The text also underscores bonding between atoms and electrons in metals. Discussions focus on bonding energies and structures in the solid elements, eigenstates of free-electron gas, and electrical co
Subset simulation for structural reliability sensitivity analysis
International Nuclear Information System (INIS)
Song Shufang; Lu Zhenzhou; Qiao Hongwei
2009-01-01
Based on two procedures for efficiently generating conditional samples, i.e. Markov chain Monte Carlo (MCMC) simulation and importance sampling (IS), two reliability sensitivity (RS) algorithms are presented. On the basis of reliability analysis of Subset simulation (Subsim), the RS of the failure probability with respect to the distribution parameter of the basic variable is transformed as a set of RS of conditional failure probabilities with respect to the distribution parameter of the basic variable. By use of the conditional samples generated by MCMC simulation and IS, procedures are established to estimate the RS of the conditional failure probabilities. The formulae of the RS estimator, its variance and its coefficient of variation are derived in detail. The results of the illustrations show high efficiency and high precision of the presented algorithms, and it is suitable for highly nonlinear limit state equation and structural system with single and multiple failure modes
Estimation of structural reliability under combined loads
International Nuclear Information System (INIS)
Shinozuka, M.; Kako, T.; Hwang, H.; Brown, P.; Reich, M.
1983-01-01
For the overall safety evaluation of seismic category I structures subjected to various load combinations, a quantitative measure of the structural reliability in terms of a limit state probability can be conveniently used. For this purpose, the reliability analysis method for dynamic loads, which has recently been developed by the authors, was combined with the existing standard reliability analysis procedure for static and quasi-static loads. The significant parameters that enter into the analysis are: the rate at which each load (dead load, accidental internal pressure, earthquake, etc.) will occur, its duration and intensity. All these parameters are basically random variables for most of the loads to be considered. For dynamic loads, the overall intensity is usually characterized not only by their dynamic components but also by their static components. The structure considered in the present paper is a reinforced concrete containment structure subjected to various static and dynamic loads such as dead loads, accidental pressure, earthquake acceleration, etc. Computations are performed to evaluate the limit state probabilities under each load combination separately and also under all possible combinations of such loads. Indeed, depending on the limit state condition to be specified, these limit state probabilities can indicate which particular load combination provides the dominant contribution to the overall limit state probability. On the other hand, some of the load combinations contribute very little to the overall limit state probability. These observations provide insight into the complex problem of which load combinations must be considered for design, for which limit states and at what level of limit state probabilities. (orig.)
Structural Reliability Analysis of Wind Turbines: A Review
Directory of Open Access Journals (Sweden)
Zhiyu Jiang
2017-12-01
Full Text Available The paper presents a detailed review of the state-of-the-art research activities on structural reliability analysis of wind turbines between the 1990s and 2017. We describe the reliability methods including the first- and second-order reliability methods and the simulation reliability methods and show the procedure for and application areas of structural reliability analysis of wind turbines. Further, we critically review the various structural reliability studies on rotor blades, bottom-fixed support structures, floating systems and mechanical and electrical components. Finally, future applications of structural reliability methods to wind turbine designs are discussed.
Reliability analysis applied to structural tests
Diamond, P.; Payne, A. O.
1972-01-01
The application of reliability theory to predict, from structural fatigue test data, the risk of failure of a structure under service conditions because its load-carrying capability is progressively reduced by the extension of a fatigue crack, is considered. The procedure is applicable to both safe-life and fail-safe structures and, for a prescribed safety level, it will enable an inspection procedure to be planned or, if inspection is not feasible, it will evaluate the life to replacement. The theory has been further developed to cope with the case of structures with initial cracks, such as can occur in modern high-strength materials which are susceptible to the formation of small flaws during the production process. The method has been applied to a structure of high-strength steel and the results are compared with those obtained by the current life estimation procedures. This has shown that the conventional methods can be unconservative in certain cases, depending on the characteristics of the structure and the design operating conditions. The suitability of the probabilistic approach to the interpretation of the results from full-scale fatigue testing of aircraft structures is discussed and the assumptions involved are examined.
Sensitivity analysis in a structural reliability context
International Nuclear Information System (INIS)
Lemaitre, Paul
2014-01-01
This thesis' subject is sensitivity analysis in a structural reliability context. The general framework is the study of a deterministic numerical model that allows to reproduce a complex physical phenomenon. The aim of a reliability study is to estimate the failure probability of the system from the numerical model and the uncertainties of the inputs. In this context, the quantification of the impact of the uncertainty of each input parameter on the output might be of interest. This step is called sensitivity analysis. Many scientific works deal with this topic but not in the reliability scope. This thesis' aim is to test existing sensitivity analysis methods, and to propose more efficient original methods. A bibliographical step on sensitivity analysis on one hand and on the estimation of small failure probabilities on the other hand is first proposed. This step raises the need to develop appropriate techniques. Two variables ranking methods are then explored. The first one proposes to make use of binary classifiers (random forests). The second one measures the departure, at each step of a subset method, between each input original density and the density given the subset reached. A more general and original methodology reflecting the impact of the input density modification on the failure probability is then explored. The proposed methods are then applied on the CWNR case, which motivates this thesis. (author)
Techniques for increasing the reliability of accelerator control system electronics
International Nuclear Information System (INIS)
Utterback, J.
1993-09-01
As the physical size of modern accelerators becomes larger and larger, the number of required control system circuit boards increases, and the probability of one of those circuit boards failing while in service also increases. In order to do physics, the experimenters need the accelerator to provide beam reliably with as little down time as possible. With the advent of colliding beams physics, reliability becomes even more important due to the fact that a control system failure can cause the loss of painstakingly produced antiprotons. These facts prove the importance of keeping reliability in mind when designing and maintaining accelerator control system electronics
Reliability analysis of grid connected small wind turbine power electronics
International Nuclear Information System (INIS)
Arifujjaman, Md.; Iqbal, M.T.; Quaicoe, J.E.
2009-01-01
Grid connection of small permanent magnet generator (PMG) based wind turbines requires a power conditioning system comprising a bridge rectifier, a dc-dc converter and a grid-tie inverter. This work presents a reliability analysis and an identification of the least reliable component of the power conditioning system of such grid connection arrangements. Reliability of the configuration is analyzed for the worst case scenario of maximum conversion losses at a particular wind speed. The analysis reveals that the reliability of the power conditioning system of such PMG based wind turbines is fairly low and it reduces to 84% of initial value within one year. The investigation is further enhanced by identifying the least reliable component within the power conditioning system and found that the inverter has the dominant effect on the system reliability, while the dc-dc converter has the least significant effect. The reliability analysis demonstrates that a permanent magnet generator based wind energy conversion system is not the best option from the point of view of power conditioning system reliability. The analysis also reveals that new research is required to determine a robust power electronics configuration for small wind turbine conversion systems.
Study of structural reliability of existing concrete structures
Druķis, P.; Gaile, L.; Valtere, K.; Pakrastiņš, L.; Goremikins, V.
2017-10-01
Structural reliability of buildings has become an important issue after the collapse of a shopping center in Riga 21.11.2013, caused the death of 54 people. The reliability of a building is the practice of designing, constructing, operating, maintaining and removing buildings in ways that ensure maintained health, ward suffered injuries or death due to use of the building. Evaluation and improvement of existing buildings is becoming more and more important. For a large part of existing buildings, the design life has been reached or will be reached in the near future. The structures of these buildings need to be reassessed in order to find out whether the safety requirements are met. The safety requirements provided by the Eurocodes are a starting point for the assessment of safety. However, it would be uneconomical to require all existing buildings and structures to comply fully with these new codes and corresponding safety levels, therefore the assessment of existing buildings differs with each design situation. This case study describes the simple and practical procedure of determination of minimal reliability index β of existing concrete structures designed by different codes than Eurocodes and allows to reassess the actual reliability level of different structural elements of existing buildings under design load.
Modeling of humidity-related reliability in enclosures with electronics
DEFF Research Database (Denmark)
Hygum, Morten Arnfeldt; Popok, Vladimir
2015-01-01
Reliability of electronics that operate outdoor is strongly affected by environmental factors such as temperature and humidity. Fluctuations of these parameters can lead to water condensation inside enclosures. Therefore, modelling of humidity distribution in a container with air and freely exposed...
Reliability & availability of wind turbine electrical & electronic components
Tavner, P.; Faulstich, S.; Hahn, B.; Bussel, van G.J.W.
2010-01-01
Recent analysis of European onshore wind turbine reliability data has shown that whilst wind turbine mechanical subassemblies tend to have relatively low failure rates but long downtimes, electrical and electronic subassemblies have relatively high failure rates and short downtimes. For onshore wind
Design for low-power and reliable flexible electronics
Huang, Tsung-Ching (Jim)
Flexible electronics are emerging as an alternative to conventional Si electronics for large-area low-cost applications such as e-paper, smart sensors, and disposable RFID tags. By utilizing inexpensive manufacturing methods such as ink-jet printing and roll-to-roll imprinting, flexible electronics can be made on low-cost plastics just like printing a newspaper. However, the key elements of exible electronics, thin-film transistors (TFTs), have slower operating speeds and less reliability than their Si electronics counterparts. Furthermore, depending on the material property, TFTs are usually mono-type -- either p- or n-type -- devices. Making air-stable complementary TFT circuits is very challenging and not applicable to most TFT technologies. Existing design methodologies for Si electronics, therefore, cannot be directly applied to exible electronics. Other inhibiting factors such as high supply voltage, large process variation, and lack of trustworthy device modeling also make designing larger-scale and robust TFT circuits a significant challenge. The major goal of this dissertation is to provide a viable solution for robust circuit design in exible electronics. I will first introduce a reliability simulation framework that can predict the degraded TFT circuits' performance under bias-stress. This framework has been validated using the amorphous-silicon (a-Si) TFT scan driver for TFT-LCD displays. To reuse the existing CMOS design ow for exible electronics, I propose a Pseudo-CMOS cell library that can make TFT circuits operable under low supply voltage and which has post-fabrication tunability for reliability and performance enhancement. This cell library has been validated using 2V self-assembly-monolayer (SAM) organic TFTs with a low-cost shadow-mask deposition process. I will also demonstrate a 3-bit 1.25KS/s Flash ADC in a-Si TFTs, which is based on the proposed Pseudo-CMOS cell library, and explore more possibilities in display, energy, and sensing
Quality assurance and reliability in the Japanese electronics industry
Pecht, Michael; Boulton, William R.
1995-02-01
Quality and reliability are two attributes required for all Japanese products, although the JTEC panel found these attributes to be secondary to customer cost requirements. While our Japanese hosts gave presentations on the challenges of technology, cost, and miniaturization, quality and reliability were infrequently the focus of our discussions. Quality and reliability were assumed to be sufficient to meet customer needs. Fujitsu's slogan, 'quality built-in, with cost and performance as prime consideration,' illustrates this point. Sony's definition of a next-generation product is 'one that is going to be half the size and half the price at the same performance of the existing one'. Quality and reliability are so integral to Japan's electronics industry that they need no new emphasis.
Adhesives technology for electronic applications materials, processing, reliability
Licari, James J
2011-01-01
Adhesives are widely used in the manufacture and assembly of electronic circuits and products. Generally, electronics design engineers and manufacturing engineers are not well versed in adhesives, while adhesion chemists have a limited knowledge of electronics. This book bridges these knowledge gaps and is useful to both groups. The book includes chapters covering types of adhesive, the chemistry on which they are based, and their properties, applications, processes, specifications, and reliability. Coverage of toxicity, environmental impacts and the regulatory framework make this book par
Reliability Analysis of Structural Timber Systems
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Hoffmeyer, P.
2000-01-01
Structural systems like timber trussed rafters and roof elements made of timber can be expected to have some degree of redundancy and nonlinear/plastic behaviour when the loading consists of for example snow or imposed load. In this paper this system effect is modelled and the statistic...... of variation. In the paper a stochastic model is described for the strength of a single piece of timber taking into account the stochastic variation of the strength and stiffness with length. Also stochastic models for different types of loads are formulated. First, simple representative systems with different...... types of redundancy and non-linearity are considered. The statistical characteristics of the load bearing capacity are determined by reliability analysis. Next, more complex systems are considered modelling the mechanical behaviour of timber roof elements I stressed skin panels made of timber. Using...
Fuse Modeling for Reliability Study of Power Electronic Circuits
DEFF Research Database (Denmark)
Bahman, Amir Sajjad; Iannuzzo, Francesco; Blaabjerg, Frede
2017-01-01
This paper describes a comprehensive modeling approach on reliability of fuses used in power electronic circuits. When fuses are subjected to current pulses, cyclic temperature stress is introduced to the fuse element and will wear out the component. Furthermore, the fuse may be used in a large......, and rated voltage/current are opposed to shift in time to effect early breaking during the normal operation of the circuit. Therefore, in such cases, a reliable protection required for the other circuit components will not be achieved. The thermo-mechanical models, fatigue analysis and thermo...
International Nuclear Information System (INIS)
Salmela, Olli
2005-01-01
In this paper, the dependability of 3rd generation telecommunications network systems is studied. Special attention is paid to a case where increased-reliability-risk electronic components are introduced to the system. The paper consists of three parts: First, the reliability data of four electronic components is considered. This includes statistical analysis of the reliability test data, thermo-mechanical finite element analysis of the printed wiring board structures, and based on those, a field reliability estimate of the components is constructed. Second, the component level reliability data is introduced into the network element reliability analysis. This is accomplished by using a reliability block diagram technique and Monte Carlo simulation of the network element. The end result of the second part is a reliability estimate of the network element with and without the high-risk component. Third, the whole 3rd generation network having multiple network elements is analyzed. In this part, the criticality of introducing high-risk electronic components into a 3rd generation telecommunications network is considered
Energy Technology Data Exchange (ETDEWEB)
Salmela, Olli [Nokia Networks, P.O. Box 301, 00045 Nokia Group (Finland)]. E-mail: olli.salmela@nokia.com
2005-08-01
In this paper, the dependability of 3rd generation telecommunications network systems is studied. Special attention is paid to a case where increased-reliability-risk electronic components are introduced to the system. The paper consists of three parts: First, the reliability data of four electronic components is considered. This includes statistical analysis of the reliability test data, thermo-mechanical finite element analysis of the printed wiring board structures, and based on those, a field reliability estimate of the components is constructed. Second, the component level reliability data is introduced into the network element reliability analysis. This is accomplished by using a reliability block diagram technique and Monte Carlo simulation of the network element. The end result of the second part is a reliability estimate of the network element with and without the high-risk component. Third, the whole 3rd generation network having multiple network elements is analyzed. In this part, the criticality of introducing high-risk electronic components into a 3rd generation telecommunications network is considered.
Selected Methods For Increases Reliability The Of Electronic Systems Security
Directory of Open Access Journals (Sweden)
Paś Jacek
2015-11-01
Full Text Available The article presents the issues related to the different methods to increase the reliability of electronic security systems (ESS for example, a fire alarm system (SSP. Reliability of the SSP in the descriptive sense is a property preservation capacity to implement the preset function (e.g. protection: fire airport, the port, logistics base, etc., at a certain time and under certain conditions, e.g. Environmental, despite the possible non-compliance by a specific subset of elements this system. Analyzing the available literature on the ESS-SSP is not available studies on methods to increase the reliability (several works similar topics but moving with respect to the burglary and robbery (Intrusion. Based on the analysis of the set of all paths in the system suitability of the SSP for the scenario mentioned elements fire events (device critical because of security.
Non-destructive Reliability Evaluation of Electronic Device by ESPI
International Nuclear Information System (INIS)
Yoon, Sung Un; Kim, Koung Suk; Kang, Ki Soo; Jo, Seon Hyung
2001-01-01
This paper propose electronic speckle pattern interferometry(ESPI) for reliability evaluation of electronic device. Especially, vibration problem in a fan of air conditioner, motor of washing machine and etc. is important factor to design the devices. But, it is difficult to apply previous method, accelerometer to the devices with complex geometry. ESPI, non-contact measurement technique applies a commercial fan of air conditioner to vibration analysis. Vibration mode shapes, natural frequency and the range of the frequency are decided and compared with that of FEM analysis. In mechanical deign of new product, ESPI adds weak point of previous method to supply effective design information
Junction Temperature Control for More Reliable Power Electronics
DEFF Research Database (Denmark)
Andresen, Markus; Ma, Ke; Buticchi, Giampaolo
2018-01-01
The thermal stress of power electronic components is one of the most important causes of their failure. Proper thermal management plays an important role for more reliable and cost-effective energy conversion. As one of the most vulnerable and expensive components, power semiconductor components ...... the desired cost-benefit tradeoff. This paper analyzes also the many open questions of this research area. Among them, it is worth highlighting that a verification of the actual lifetime extension is still missing....
Reliability of structural materials in nuclear industry
International Nuclear Information System (INIS)
Pinard Legry, G.
1996-01-01
The reliability of nuclear installations is a fundamental point for the exploitation of nuclear energy. It requires an extensive knowledge of the behaviour of materials in the operating conditions and during the expected service life of the installations. In nuclear power plants multiple risks of failure can exist and are expressed by corrosion and deformation phenomena or by modification in the mechanical characteristics of materials. The knowledge of the evolution with time of a given material requires to take into account the data relative to the material itself, to its environment and to the physical conditions of this environment. The study of materials aging needs a more precise knowledge of the kinetics of phenomena at any scale and of their interactions, and a micro- or macro-modeling of their behaviour during long periods of time. This paper gives an overview of the aging phenomena that occur in the structural materials involved in PWR and fast neutron reactors: thermal aging, generalized corrosion, corrosion under constraint, intergranular corrosion, crack growth under loading, wear, irradiation etc.. (J.S.)
Electronic structure of superlattices
International Nuclear Information System (INIS)
Altarelli, M.
1987-01-01
Calculations of electronic states in semiconductor superlattices are briefly reviewed, with emphasis on the envelope-function method and on comparison with experiments. The energy levels in presence of external magnetic fields are discussed and compared to magneto-optical experiments. (author) [pt
Electronic structure of alloys
International Nuclear Information System (INIS)
Ehrenreich, H.; Schwartz, L.M.
1976-01-01
The description of electronic properties of binary substitutional alloys within the single particle approximation is reviewed. Emphasis is placed on a didactic exposition of the equilibrium properties of the transport and magnetic properties of such alloys. Topics covered include: multiple scattering theory; the single band alloy; formal extensions of the theory; the alloy potential; realistic model state densities; the s-d model; and the muffin tin model. 43 figures, 3 tables, 151 references
Electronic device for endosurgical skills training (EDEST): study of reliability.
Pagador, J B; Uson, J; Sánchez, M A; Moyano, J L; Moreno, J; Bustos, P; Mateos, J; Sánchez-Margallo, F M
2011-05-01
Minimally Invasive Surgery procedures are commonly used in many surgical practices, but surgeons need specific training models and devices due to its difficulty and complexity. In this paper, an innovative electronic device for endosurgical skills training (EDEST) is presented. A study on reliability for this device was performed. Different electronic components were used to compose this new training device. The EDEST was focused on two basic laparoscopic tasks: triangulation and coordination manoeuvres. A configuration and statistical software was developed to complement the functionality of the device. A calibration method was used to assure the proper work of the device. A total of 35 subjects (8 experts and 27 novices) were used to check the reliability of the system using the MTBF analysis. Configuration values for triangulation and coordination exercises were calculated as 0.5 s limit threshold and 800-11,000 lux range of light intensity, respectively. Zero errors in 1,050 executions (0%) for triangulation and 21 errors in 5,670 executions (0.37%) for coordination were obtained. A MTBF of 2.97 h was obtained. The results show that the reliability of the EDEST device is acceptable when used under previously defined light conditions. These results along with previous work could demonstrate that the EDEST device can help surgeons during first training stages.
Structural reliability codes for probabilistic design
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager
1997-01-01
probabilistic code format has not only strong influence on the formal reliability measure, but also on the formal cost of failure to be associated if a design made to the target reliability level is considered to be optimal. In fact, the formal cost of failure can be different by several orders of size for two...... different, but by and large equally justifiable probabilistic code formats. Thus, the consequence is that a code format based on decision theoretical concepts and formulated as an extension of a probabilistic code format must specify formal values to be used as costs of failure. A principle of prudence...... is suggested for guiding the choice of the reference probabilistic code format for constant reliability. In the author's opinion there is an urgent need for establishing a standard probabilistic reliability code. This paper presents some considerations that may be debatable, but nevertheless point...
Compilation of the calculation elements of the electronic equipments reliability
International Nuclear Information System (INIS)
Lefevre, R.; D'Harcourt, A.; Dupuy, G.
1968-01-01
The aim of this work is to allow the practical execution of the estimated calculation of the electronic devices reliability and to standardize the source and the approach of the calculations while giving a systematic character to their execution mode. The systematic character of the calculations allows a comparison of the reliability of different materials and a rapid control of the calculations validity; at last, it brings out the use conditions of all the components of a set. A reliability calculation made according to the method described here reveals: -components badly used -the relative influence on the reliability of the set, of a component or a components group taking into account of the number, of the characteristics and of the use of these ones. At last, the results of the calculation allows to organize the exploitation (availability) and the maintenance (staff, stock of components) of the materials. The failure rates given in this book are only relating to the components service-life and do not correspond to precocious failures. (authors) [fr
Reliability enhancement of portal frame structure by finite element synthesis
International Nuclear Information System (INIS)
Nakagiri, S.
1989-01-01
The stochastic finite element methods have been applied to the evaluation of structural response and reliability of uncertain structural systems. The structural reliability index of the advanced first-order second moment (AFOSM) method is a candidate of the measure of assessing structural safety and reliability. The reliability index can be evaluated when a baseline design of structures under interest is proposed and the covariance matrix of the probabilistic variables is acquired to represent uncertainties involved in the structure systems. The reliability index thus evaluated is not assured the largest one for the structure. There is left a possibility to enhance the structural reliability for the given covariance matrix by changing the baseline design. From such a viewpoint of structural optimization, some ideas have been proposed to maximize the reliability or to minimize the failure probability of uncertain structural systems. A method of changing the design is proposed to increase the reliability index from its baseline value to another desired value. The reliability index in this paper is calculated mainly by the method of Lagrange multiplier
Electronics for Piezoelectric Smart Structures
Warkentin, D. J.; Tani, J.
1997-01-01
This paper briefly presents work addressing some of the basic considerations for the electronic components used in smart structures incorporating piezoelectric elements. After general remarks on the application of piezoelectric elements to the problem of structural vibration control, three main topics are described. Work to date on the development of techniques for embedding electronic components within structural parts is presented, followed by a description of the power flow and dissipation requirements of those components. Finally current work on the development of electronic circuits for use in an 'active wall' for acoustic noise is introduced.
Future of structural reliability methodology in nuclear power plant technology
Energy Technology Data Exchange (ETDEWEB)
Schueeller, G I [Technische Univ. Muenchen (Germany, F.R.); Kafka, P [Gesellschaft fuer Reaktorsicherheit m.b.H. (GRS), Garching (Germany, F.R.)
1978-10-01
This paper presents the authors' personal view as to which areas of structural reliability in nuclear power plant design need most urgently to be advanced. Aspects of simulation modeling, design rules, codification and specification of reliability, system analysis, probabilistic structural dynamics, rare events and particularly the interaction of systems and structural reliability are discussed. As an example, some considerations of the interaction effects between the protective systems and the pressure vessel are stated. The paper concludes with recommendation for further research.
Reliability of high power electron accelerators for radiation processing
International Nuclear Information System (INIS)
Zimek, Z.
2011-01-01
Accelerators applied for radiation processing are installed in industrial facilities where accelerator availability coefficient should be at the level of 95% to fulfill requirements according to industry standards. Usually the exploitation of electron accelerator reviles the number of short and few long lasting failures. Some technical shortages can be overcome by practical implementation the experience gained in accelerator technology development by different accelerator manufactures. The reliability/availability of high power accelerators for application in flue gas treatment process must be dramatically improved to meet industrial standards. Support of accelerator technology dedicated for environment protection should be provided by governmental and international institutions to overcome accelerator reliability/availability problem and high risk and low direct profit in this particular application. (author)
Reliability of high power electron accelerators for radiation processing
Energy Technology Data Exchange (ETDEWEB)
Zimek, Z. [Department of Radiation Chemistry and Technology, Institute of Nuclear Chemistry and Technology, Warsaw (Poland)
2011-07-01
Accelerators applied for radiation processing are installed in industrial facilities where accelerator availability coefficient should be at the level of 95% to fulfill requirements according to industry standards. Usually the exploitation of electron accelerator reviles the number of short and few long lasting failures. Some technical shortages can be overcome by practical implementation the experience gained in accelerator technology development by different accelerator manufactures. The reliability/availability of high power accelerators for application in flue gas treatment process must be dramatically improved to meet industrial standards. Support of accelerator technology dedicated for environment protection should be provided by governmental and international institutions to overcome accelerator reliability/availability problem and high risk and low direct profit in this particular application. (author)
Control of climatics environments to enhance reliability of electronics systems
International Nuclear Information System (INIS)
Sekhon, K.S.
1979-01-01
The techniques to control temperature and humidity to reduce failures in semiconductor devices are presented. The maximum operating junction temperature affects the electronic system reliability, and the equation for the junction temperature of the device shows that internal and external thermal resistances affect component life. Junction temperature reductions up to 60 C were achieved by the development of heat pipes for microcircuits, which will enhance electronics life by 32 times. Humidity control by improved sealing and use of heaters to prevent moisture condensation proved difficult and costly, and high pressure dehydrators were heavy and expensive. Therefore, low pressure dehydrator was developed which is smaller, lighter, and less expensive. The development of low pressure dehumidifying system including test data is presented
Reliability metrics extraction for power electronics converter stressed by thermal cycles
DEFF Research Database (Denmark)
Ma, Ke; Choi, Uimin; Blaabjerg, Frede
2017-01-01
Due to the continuous demands for highly reliable and cost-effective power conversion, the quantified reliability performances of the power electronics converter are becoming emerging needs. The existing reliability modelling approaches for the power electronics converter mainly focuses on the pr...... performance of power electronics system. The final predicted results showed good accuracy with much more reliability information compared to the existing approaches, and the quantified reliability correlation to the mission profiles of converter is mathematically established....
Structural dynamics of electronic and photonic systems
Suhir, Ephraim; Steinberg, David S
2011-01-01
The proposed book will offer comprehensive and versatile methodologies and recommendations on how to determine dynamic characteristics of typical micro- and opto-electronic structural elements (printed circuit boards, solder joints, heavy devices, etc.) and how to design a viable and reliable structure that would be able to withstand high-level dynamic loading. Particular attention will be given to portable devices and systems designed for operation in harsh environments (such as automotive, aerospace, military, etc.) In-depth discussion from a mechanical engineer's viewpoint will be conducte
System Reliability of Timber Structures with Ductile Behaviour
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Čizmar, Dean
2011-01-01
The present paper considers the evaluation of timber structures with the focus on robustness due to connection ductility. The robustness analysis is based on the structural reliability framework applied to a simplified mechanical system. The structural timber system is depicted as a parallel system....... An evaluation method of the ductile behaviour is introduced. For different ductile behaviours, the system reliability is estimated based on Monte Carlo simulation. A correlation between the strength of the structural elements is introduced. The results indicate that the reliability of a structural timber system...
Electronic structure of silicon superlattices
International Nuclear Information System (INIS)
Krishnamurthy, S.; Moriarty, J.A.
1984-01-01
Utilizing a new complex-band-structure technique, the electronic structure of model Si-Si/sub 1-x/Ge/sub x/ and MOS superlattices has been obtained over a wide range of layer thickness d (11 less than or equal to d less than or equal to 110 A). For d greater than or equal to 44 A, it is found that these systems exhibit a direct fundamental band gap. Further calculations of band-edge effective masses and impurity scattering rates suggest the possibility of a band-structure-driven enhancement in electron mobility over bulk silicon
Reliability based Robustness of Timber Structures through NDT Data Updating
DEFF Research Database (Denmark)
Sousa, Hélder S.; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning
2011-01-01
This work presents a framework for reliability-based assessment of timber structures / members using data gathered from non-destructive test results. These results are used for modeling an update of the mechanical characteristics of timber, using Bayesian methods. Results gathered from ultrasound...... of the structure, thus, being possible to evaluate reliability based in time dependent factors, as well to categorize that structure in terms of robustness. For exemplification of the underlined concepts, three different types of structures are studied....
Reliability and considerations of electronic voting, a global vision
Directory of Open Access Journals (Sweden)
Jussibeth Tatiana Places Chungata
2017-03-01
Full Text Available This article is intended to perform an analysis of all the aspects that comprise and revolve around the use or implementation of new technologies in election processes such as automation of democracy; this is done through the collection of bibliographic information from articles, books, and other sources on concepts, differences, comparisons, methodology of citizen participation, experiences, among others. With the purpose of establishing the utility or inconveniences that may present this electronic voting system to use it in real elections. There are realized general descriptions of every topic, where little by little possible factors of adoption are explored or I reject to this new technology, clarifying in the functionality, used elements and factors to comply. As a result, it reflects on the positive and negative impact that have these systems in society, giving points to consider about this Automation at different stages which comprise the electoral processes, from the construction, configuration, storage up to the transmission and consolidation of results. Is leaves clear them criteria that is should evaluate a system of vote electronic that van from reliability to effectiveness in their processes, to determine the need and relationship of costs - benefits. Without leaving of side our country, there is described the current condition that has the system of electronic vote in our electoral processes, which until now has not been implemented, only has performed testing of printing in our community.
Risk-based Optimization and Reliability Levels of Coastal Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Burcharth, H. F.
Identification of optimum reliability levels for coastal structures is considered. A class of breakwaters is considered where no human injuries can be expected in cases of failure. The optimum reliability level is identified by minimizing the total costs over the service life of the structure, in...... on the minimumcost reliability levels is investigated for different values of the real rate of interest, the service lifetime, the downtime costs due to malfunction and the decommission costs.......Identification of optimum reliability levels for coastal structures is considered. A class of breakwaters is considered where no human injuries can be expected in cases of failure. The optimum reliability level is identified by minimizing the total costs over the service life of the structure...
Risk-based Optimization and Reliability Levels of Coastal Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Burcharth, Hans F.
2005-01-01
Identification of optimum reliability levels for coastal structures is considered. A class of breakwaters is considered where no human injuries can be expected in cases of failure. The optimum reliability level is identified by minimizing the total costs over the service life of the structure, i...... on the minimumcost reliability levels is investigated for different values of the real rate of interest, the service lifetime, the downtime costs due to malfunction and the decommission costs....... Identification of optimum reliability levels for coastal structures is considered. A class of breakwaters is considered where no human injuries can be expected in cases of failure. The optimum reliability level is identified by minimizing the total costs over the service life of the structure...
Reliability of Elasto-Plastic Structural Systems
DEFF Research Database (Denmark)
Delmar, M. V.; Sørensen, John Dalsgaard
1990-01-01
This paper proposes a method for generating safety margins and failure mode equations for elasto-plastic structures where interaction of load effects is taken into account. Structural failure is defined by large nodal displacements or plastic collapse. A branch-and-bound technique is used...
Improving Electronic Sensor Reliability by Robust Outlier Screening
Directory of Open Access Journals (Sweden)
Federico Cuesta
2013-10-01
Full Text Available Electronic sensors are widely used in different application areas, and in some of them, such as automotive or medical equipment, they must perform with an extremely low defect rate. Increasing reliability is paramount. Outlier detection algorithms are a key component in screening latent defects and decreasing the number of customer quality incidents (CQIs. This paper focuses on new spatial algorithms (Good Die in a Bad Cluster with Statistical Bins (GDBC SB and Bad Bin in a Bad Cluster (BBBC and an advanced outlier screening method, called Robust Dynamic Part Averaging Testing (RDPAT, as well as two practical improvements, which significantly enhance existing algorithms. Those methods have been used in production in Freescale® Semiconductor probe factories around the world for several years. Moreover, a study was conducted with production data of 289,080 dice with 26 CQIs to determine and compare the efficiency and effectiveness of all these algorithms in identifying CQIs.
Reliability Analysis of the CERN Radiation Monitoring Electronic System CROME
AUTHOR|(CDS)2126870
For the new in-house developed CERN Radiation Monitoring Electronic System (CROME) a reliability analysis is necessary to ensure compliance with the statu-tory requirements regarding the Safety Integrity Level. The required Safety Integrity Level by IEC 60532 standard is SIL 2 (for the Safety Integrated Functions Measurement, Alarm Triggering and Interlock Triggering). The ﬁrst step of the reliability analysis was a system and functional analysis which served as basis for the implementation of the CROME system in the software “Iso-graph”. In the “Prediction” module of Isograph the failure rates of all components were calculated. Failure rates for passive components were calculated by the Military Standard 217 and failure rates for active components were obtained from lifetime tests by the manufacturers. The FMEA was carried out together with the board designers and implemented in the “FMECA” module of Isograph. The FMEA served as basis for the Fault Tree Analysis and the detection of weak points...
Thermal Management and Reliability of Power Electronics and Electric Machines
Energy Technology Data Exchange (ETDEWEB)
Narumanchi, Sreekant
2016-08-03
Increasing the number of electric-drive vehicles (EDVs) on America's roads has been identified as a strategy with near-term potential for dramatically decreasing the nation's dependence on oil -- by the U.S. Department of Energy, the federal cross-agency EV-Everywhere Challenge, and the automotive industry. Mass-market deployment will rely on meeting aggressive technical targets, including improved efficiency and reduced size, weight, and cost. Many of these advances will depend on optimization of thermal management. Effective thermal management is critical to improving the performance and ensuring the reliability of EDVs. Efficient heat removal makes higher power densities and lower operating temperatures possible, and in turn enables cost and size reductions. The National Renewable Energy Laboratory (NREL), along with DOE and industry partners is working to develop cost-effective thermal management solutions to increase device and component power densities. In this presentation, the activities in recent years related to thermal management and reliability of automotive power electronics and electric machines will be presented.
Thermal Management and Reliability of Power Electronics and Electric Machines
Energy Technology Data Exchange (ETDEWEB)
Narumanchi, Sreekant
2016-06-13
Increasing the number of electric-drive vehicles (EDVs) on America's roads has been identified as a strategy with near-term potential for dramatically decreasing the nation's dependence on oil - by the U.S. Department of Energy, the federal cross-agency EV-Everywhere Challenge, and the automotive industry. Mass-market deployment will rely on meeting aggressive technical targets, including improved efficiency and reduced size, weight, and cost. Many of these advances will depend on optimization of thermal management. Effective thermal management is critical to improving the performance and ensuring the reliability of EDVs. Efficient heat removal makes higher power densities and lower operating temperatures possible, and in turn enables cost and size reductions. The National Renewable Energy Laboratory (NREL), along with DOE and industry partners is working to develop cost-effective thermal management solutions to increase device and component power densities. In this presentation, the activities in recent years related to thermal management and reliability of automotive power electronics and electric machines are presented.
Recent advances in computational structural reliability analysis methods
Thacker, Ben H.; Wu, Y.-T.; Millwater, Harry R.; Torng, Tony Y.; Riha, David S.
1993-10-01
The goal of structural reliability analysis is to determine the probability that the structure will adequately perform its intended function when operating under the given environmental conditions. Thus, the notion of reliability admits the possibility of failure. Given the fact that many different modes of failure are usually possible, achievement of this goal is a formidable task, especially for large, complex structural systems. The traditional (deterministic) design methodology attempts to assure reliability by the application of safety factors and conservative assumptions. However, the safety factor approach lacks a quantitative basis in that the level of reliability is never known and usually results in overly conservative designs because of compounding conservatisms. Furthermore, problem parameters that control the reliability are not identified, nor their importance evaluated. A summary of recent advances in computational structural reliability assessment is presented. A significant level of activity in the research and development community was seen recently, much of which was directed towards the prediction of failure probabilities for single mode failures. The focus is to present some early results and demonstrations of advanced reliability methods applied to structural system problems. This includes structures that can fail as a result of multiple component failures (e.g., a redundant truss), or structural components that may fail due to multiple interacting failure modes (e.g., excessive deflection, resonate vibration, or creep rupture). From these results, some observations and recommendations are made with regard to future research needs.
Reliability based Design of Coastal Structures
DEFF Research Database (Denmark)
Burcharth, H. F.
2003-01-01
Conventional design practice for coastal structures is deterministic in nature and is based on the concept of a design load which should not exceed the resistance (carrying capacity) of the structure. The design load is usually defined on a probabilistic basis as a characteristic value of the load......, for example the expectation (mean) value of the 100-year return period event. However, this selection is often made without consideration of the involved uncertainties. In most cases the resistance is defined in terms of the load that causes a certain design impact or damage to the structure...
Reliability assessment of Indian Point Unit 3 containment structure
International Nuclear Information System (INIS)
Kawakami, J.; Hwang, H.; Chang, M.T.; Reich, M.
1984-01-01
In the current design criteria, the load combinations specified for design of concrete containment structures are in the deterministic formats. However, by applying the probability-based reliability method developed by BNL to the concrete containment structures designed according to the criteria, it is possible to evaluate the reliability levels implied in the current design criteria. For this purpose, the reliability analysis is applied to the Indian Point Unit No. 3 containment. The details of the containment structure such as the geometries and the rebar arrangements, etc., are taken from the working drawings and the final safety analysis reports. Three kinds of loads are considered in the reliability analysis. They are, dead load (D), accidental pressure due to a large LOCA (P), and earthquake ground acceleration (E). Reliability analysis of the containment subjected to all combinations of loads is performed. Results are presented in this report
Reliability Evaluation of a Structure at Sea
DEFF Research Database (Denmark)
Burcharth, H. F.
1994-01-01
Conventional design practice for coastal structures is deterministic in nature and is based on the concept of a design load, which should not exceed the resistance (carrying capacity) of the structure. The design load is usually defined on a probabilistic basis as a characteristic value of the load......, e.g. the expectation (mean) value of the lOO-year return period event, however, often without consideration of the involved uncertainties. The resistance is in most cases defined in terms of the load which causes a certain design impact or damage to the structure and is not given as an ultimate...... formulae are semi-empirical being based mainly on central fitting to model test results. The often considerable scatter in test results is not considered in general because the formulae normally express only the mean values. Consequently, the applied characteristic value of the resistance is then the mean...
Reliability Evaluation of a Structure at Sea
DEFF Research Database (Denmark)
Burcharth, H. F.
1992-01-01
Conventional design practice for coastal structures is deterministic in nature and is based on the concept of a design load, which should not exceed the resistance (carrying capacity) of the structure. The design load is usually defined on a probabilistic basis as a characteristic value of the load......, e.g. the expectation (mean) value of the 100-year return period event, however, often without consideration of the involved uncertainties. The resistance is in most cases defined in terms of the load which causes a certain design impact or damage to the structure and is not given as an ultimate...... formulae are semi-empirical being based mainly on central fitting to model test results. The often considerable scatter in test results is not considered in general because the formulae normally express only the mean values. Consequently, the applied characteristic value of the resistance is then the mean...
Some aspects of the interaction between systems- and structural reliability
International Nuclear Information System (INIS)
Schueller, G.K.; Schmitt, W.
1979-01-01
The purpose of this paper is to study the interaction between systems- and structural reliability analysis with reference to the design of structural components of LWR. Presently the evaluation of systems reliability is carried out apart from structural reliability analysis. Moreover, two basically different methodologies are used for analysis. While in systems analysis the simplified binary approach is still generally accepted, in structural reliability one has to resort to more sophisticated procedures to obtain realistic results. The interactive effect may be illustrated as follows: For example, the integrity of the primary circuit interacts with the integrity of the containment structure. This means that the probability of occurrence of the pipe rupture which may cause a LOCA and consequently leads to a build-up of temperature and pressure within the containment affects directly its structural reliability. The piping system, particularly the primary piping, in turn interacts with the protective system, which is part of the safety system. This piping structure is also subjected to various operational loading conditions. In a numerical example dealing with leakage probabilities of pipes it is shown how methods of structural reliability may be used to gain more insight in the estimation of failure rates of system components. (orig.)
Electronic structure and correlation effects in actinides
International Nuclear Information System (INIS)
Albers, R.C.
1998-01-01
This report consists of the vugraphs given at a conference on electronic structure. Topics discussed are electronic structure, f-bonding, crystal structure, and crystal structure stability of the actinides and how they are inter-related
Reliability analysis of RC containment structures under combined loads
International Nuclear Information System (INIS)
Hwang, H.; Reich, M.; Kagami, S.
1984-01-01
This paper discusses a reliability analysis method and load combination design criteria for reinforced concrete containment structures under combined loads. The probability based reliability analysis method is briefly described. For load combination design criteria, derivations of the load factors for accidental pressure due to a design basis accident and safe shutdown earthquake (SSE) for three target limit state probabilities are presented
Ballistic transport and electronic structure
Schep, Kees M.; Kelly, Paul J.; Bauer, Gerrit E.W.
1998-01-01
The role of the electronic structure in determining the transport properties of ballistic point contacts is studied. The conductance in the ballistic regime is related to simple geometrical projections of the Fermi surface. The essential physics is first clarified for simple models. For real
The Electronic Structure of Calcium
DEFF Research Database (Denmark)
Jan, J.-P.; Skriver, Hans Lomholt
1981-01-01
The electronic structure of calcium under pressure is re-examined by means of self-consistent energy band calculations based on the local density approximation and using the linear muffin-tin orbitals (LMTO) method with corrections to the atomic sphere approximation included. At zero pressure...
Electronic structure of metal clusters
International Nuclear Information System (INIS)
Wertheim, G.K.
1989-01-01
Photoemission spectra of valence electrons in metal clusters, together with threshold ionization potential measurements, provide a coherent picture of the development of the electronic structure from the isolated atom to the large metallic cluster. An insulator-metal transition occurs at an intermediate cluster size, which serves to define the boundary between small and large clusters. Although the outer electrons may be delocalized over the entire cluster, a small cluster remains insulating until the density of states near the Fermi level exceeds 1/kT. In large clusters, with increasing cluster size, the band structure approaches that of the bulk metal. However, the bands remain significantly narrowed even in a 1000-atom cluster, giving an indication of the importance of long-range order. The core-electron binding-energy shifts of supported metal clusters depend on changes in the band structure in the initial state, as well as on various final-state effects, including changes in core hole screening and the coulomb energy of the final-state charge. For cluster supported on amorphous carbon, this macroscopic coulomb shift is often dominant, as evidenced by the parallel shifts of the core-electron binding energy and the Fermi edge. Auger data confirm that final-state effects dominate in cluster of Sn and some other metals. Surface atom core-level shifts provide a valuable guide to the contributions of initial-state changes in band structure to cluster core-electron binding energy shifts, especially for Au and Pt. The available data indicate that the shift observed in supported, metallic clusters arise largely from the charge left on the cluster by photoemission. As the metal-insulator transition is approached from above, metallic screening is suppressed and the shift is determined by the local environment. (orig.)
Hai An; Ling Zhou; Hui Sun
2016-01-01
Aiming to resolve the problems of a variety of uncertainty variables that coexist in the engineering structure reliability analysis, a new hybrid reliability index to evaluate structural hybrid reliability, based on the random–fuzzy–interval model, is proposed in this article. The convergent solving method is also presented. First, the truncated probability reliability model, the fuzzy random reliability model, and the non-probabilistic interval reliability model are introduced. Then, the new...
Quantifiable and Reliable Structural Health Management Systems, Phase I
National Aeronautics and Space Administration — Major concerns for implementing a practical built-in structural health monitoring system are prediction accuracy and data reliability. It is proposed to develop...
Reliability-based optimal structural design by the decoupling approach
International Nuclear Information System (INIS)
Royset, J.O.; Der Kiureghian, A.; Polak, E.
2001-01-01
A decoupling approach for solving optimal structural design problems involving reliability terms in the objective function, the constraint set or both is discussed and extended. The approach employs a reformulation of each problem, in which reliability terms are replaced by deterministic functions. The reformulated problems can be solved by existing semi-infinite optimization algorithms and computational reliability methods. It is shown that the reformulated problems produce solutions that are identical to those of the original problems when the limit-state functions defining the reliability problem are affine. For nonaffine limit-state functions, approximate solutions are obtained by solving series of reformulated problems. An important advantage of the approach is that the required reliability and optimization calculations are completely decoupled, thus allowing flexibility in the choice of the optimization algorithm and the reliability computation method
Review of Industrial Applications of Structural Reliability Theory
DEFF Research Database (Denmark)
Thoft-Christensen, Palle
For the last two decades we have seen an increasing interest in applying structural reliability theory to many different industries. However, the number of real practical applications is much smaller than what one would expect.......For the last two decades we have seen an increasing interest in applying structural reliability theory to many different industries. However, the number of real practical applications is much smaller than what one would expect....
Structural Reliability of the Nigerian Grown Abura Timber Bridge ...
African Journals Online (AJOL)
Structural reliability analysis was carried out on the Nigerian grown Abura timber, to ascertain its structural performance as timber bridge beams. Samples of the Nigerian grown Abura timber were bought from timber market, seasoned naturally and their structural/strength properties were determined at a moisture content of ...
Stochastic Finite Elements in Reliability-Based Structural Optimization
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Engelund, S.
1995-01-01
Application of stochastic finite elements in structural optimization is considered. It is shown how stochastic fields modelling e.g. the modulus of elasticity can be discretized in stochastic variables and how a sensitivity analysis of the reliability of a structural system with respect to optimi......Application of stochastic finite elements in structural optimization is considered. It is shown how stochastic fields modelling e.g. the modulus of elasticity can be discretized in stochastic variables and how a sensitivity analysis of the reliability of a structural system with respect...... to optimization variables can be performed. A computer implementation is described and an illustrative example is given....
Stochastic Finite Elements in Reliability-Based Structural Optimization
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Engelund, S.
Application of stochastic finite elements in structural optimization is considered. It is shown how stochastic fields modelling e.g. the modulus of elasticity can be discretized in stochastic variables and how a sensitivity analysis of the reliability of a structural system with respect to optimi......Application of stochastic finite elements in structural optimization is considered. It is shown how stochastic fields modelling e.g. the modulus of elasticity can be discretized in stochastic variables and how a sensitivity analysis of the reliability of a structural system with respect...
Studies in the electronic structure of matter
International Nuclear Information System (INIS)
Swarts, C.A.
1979-01-01
Chapter I: Here the results of various theories for the angular distribution of electrons photoemitted from the outermost p-shell of rare gas atoms are compared. The theories compared are (I) the local density theories of Slater (X/sub α/) and of Hohenberg, Kohn and Sham, (II) the pseudopotential method, (III) Hartree-Fock theory as evaluated by Kennedy and Manson, and (IV) Amusia's Random Phase Approximation with Exchange (RPAE). It is shown that the local density theories, although simple, generally fail to produce reliable cross section; the more complicated Hartree-Fock method is no more reliable; the a priori RPAE method is most reliable, but tedious; and the phenomenological pseudopotential method offers a good combination of reliability and simplicity. The muffin-tin approximation, widely used in molecular and condensed matter physics, is examined and found to be adequate. Chapter II: Extended Hueckel theory is applied to GaAs, GaP and to the nitrogen isoelectronic trap in GaAs and GaP. The computed perfect crystal band structures are found to be in reasonable agreement with those computed with empirical pseudopotentials. Nitrogen impurity levels in GaAs and GaP are calculated using a cluster model. Chapter III: By means of model calculations for an independent electron metal, we obtain exact lineshapes for the photon absorption, emission and photoemission spectra of deep core states. We find in each case an X-ray edge anomaly as pedicted by Nozieres and De Dominicis. Sumrules are used as a general check on the calculations and to explain the deviations of the exact theory from the exciton theory away from threshold
Integrated Reliability-Based Optimal Design of Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1987-01-01
In conventional optimal design of structural systems the weight or the initial cost of the structure is usually used as objective function. Further, the constraints require that the stresses and/or strains at some critical points have to be less than some given values. Finally, all variables......-based optimal design is discussed. Next, an optimal inspection and repair strategy for existing structural systems is presented. An optimization problem is formulated , where the objective is to minimize the expected total future cost of inspection and repair subject to the constraint that the reliability...... value. The reliability can be measured from an element and/or a systems point of view. A number of methods to solve reliability-based optimization problems has been suggested, see e.g. Frangopol [I]. Murotsu et al. (2], Thoft-Christensen & Sørensen (3] and Sørensen (4). For structures where...
A reliable method for the stability analysis of structures ...
African Journals Online (AJOL)
The detection of structural configurations with singular tangent stiffness matrix is essential because they can be unstable. The secondary paths, especially in unstable buckling, can play the most important role in the loss of stability and collapse of the structure. A new method for reliable detection and accurate computation of ...
Efficiency criteria for high reliability measured system structures
International Nuclear Information System (INIS)
Sal'nikov, N.L.
2012-01-01
The procedures of structural redundancy are usually used to develop high reliability measured systems. To estimate efficiency of such structures the criteria to compare different systems has been developed. So it is possible to develop more exact system by inspection of redundant system data unit stochastic characteristics in accordance with the developed criteria [ru
Interactive Reliability-Based Optimization of Structural Systems
DEFF Research Database (Denmark)
Pedersen, Claus
In order to introduce the basic concepts within the field of reliability-based structural optimization problems, this chapter is devoted to a brief outline of the basic theories. Therefore, this chapter is of a more formal nature and used as a basis for the remaining parts of the thesis. In section...... 2.2 a general non-linear optimization problem and corresponding terminology are presented whereupon optimality conditions and the standard form of an iterative optimization algorithm are outlined. Subsequently, the special properties and characteristics concerning structural optimization problems...... are treated in section 2.3. With respect to the reliability evalutation, the basic theory behind a reliability analysis and estimation of probability of failure by the First-Order Reliability Method (FORM) and the iterative Rackwitz-Fiessler (RF) algorithm are considered in section 2.5 in which...
Neglect Of Parameter Estimation Uncertainty Can Significantly Overestimate Structural Reliability
Directory of Open Access Journals (Sweden)
Rózsás Árpád
2015-12-01
Full Text Available Parameter estimation uncertainty is often neglected in reliability studies, i.e. point estimates of distribution parameters are used for representative fractiles, and in probabilistic models. A numerical example examines the effect of this uncertainty on structural reliability using Bayesian statistics. The study reveals that the neglect of parameter estimation uncertainty might lead to an order of magnitude underestimation of failure probability.
Electronic structure of lanthanide scandates
Mizzi, Christopher A.; Koirala, Pratik; Marks, Laurence D.
2018-02-01
X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and density functional theory calculations were used to study the electronic structure of three lanthanide scandates: GdSc O3,TbSc O3 , and DySc O3 . X-ray photoelectron spectra simulated from first-principles calculations using a combination of on-site hybrid and GGA +U methods were found to be in good agreement with experimental x-ray photoelectron spectra. The hybrid method was used to model the ground state electronic structure and the GGA +U method accounted for the shift of valence state energies due to photoelectron emission via a Slater-Janak transition state approach. From these results, the lanthanide scandate valence bands were determined to be composed of Ln 4 f ,O 2 p , and Sc 3 d states, in agreement with previous work. However, contrary to previous work the minority Ln 4 f states were found to be located closer to, and in some cases at, the valence band maximum. This suggests that minority Ln 4 f electrons may play a larger role in lanthanide scandate properties than previously thought.
Structural reliability analysis based on the cokriging technique
International Nuclear Information System (INIS)
Zhao Wei; Wang Wei; Dai Hongzhe; Xue Guofeng
2010-01-01
Approximation methods are widely used in structural reliability analysis because they are simple to create and provide explicit functional relationships between the responses and variables in stead of the implicit limit state function. Recently, the kriging method which is a semi-parameter interpolation technique that can be used for deterministic optimization and structural reliability has gained popularity. However, to fully exploit the kriging method, especially in high-dimensional problems, a large number of sample points should be generated to fill the design space and this can be very expensive and even impractical in practical engineering analysis. Therefore, in this paper, a new method-the cokriging method, which is an extension of kriging, is proposed to calculate the structural reliability. cokriging approximation incorporates secondary information such as the values of the gradients of the function being approximated. This paper explores the use of the cokriging method for structural reliability problems by comparing it with the Kriging method based on some numerical examples. The results indicate that the cokriging procedure described in this work can generate approximation models to improve on the accuracy and efficiency for structural reliability problems and is a viable alternative to the kriging.
Assessment of structural reliability of precast concrete buildings
Directory of Open Access Journals (Sweden)
Koyankin Alexandr
2018-01-01
Full Text Available Precast housing construction is currently being under rapid development, however, reliability of building structures made from precast reinforced concrete cannot be assessed rationally due to insufficient research data on that subject. In this regard, experimental and numerical studies were conducted to assess structural reliability of precast buildings as described in the given paper. Experimental studies of full-scale and model samples were conducted; numerical studies were held based on finite element models using “Lira” software. The objects under study included fragment of flooring of a building under construction, full-size fragment of flooring, full-scale models of precast cross-beams-to-columns joints and joints between hollow-core floor slabs and precast and cast-in-place cross-beams. Conducted research enabled to perform an objective assessment of structural reliability of precast buildings.
Reliability of redundant structures of nuclear reactor protection systems
International Nuclear Information System (INIS)
Vojnovic, B.
1983-01-01
In this paper, reliability of various redundant structures of PWR protection systems has been analysed. Structures of reactor tip systems as well as the systems for activation of safety devices have been presented. In all those systems redundancy is achieved by means of so called majority voting logic ('r out of n' structures). Different redundant devices have been compared, concerning probability of occurrence of safe as well as unsafe failures. (author)
Transitioning to Physics-of-Failure as a Reliability Driver in Power Electronics
DEFF Research Database (Denmark)
Wang, Huai; Liserre, Marco; Blaabjerg, Frede
2014-01-01
Power electronics has progressively gained important status in power generation, distribution and consumption. With more than 70% of electricity processed through power electronics, recent research endeavors to improve the reliability of power electronic systems to comply with more stringent...... constraints on cost, safety and availability in various applications. This paper serves to give an overview of the major aspects of reliability in power electronics and to address the future trends in this multidisciplinary research direction. The ongoing paradigm shift in reliability research is presented...... first. Then the three major aspects of power electronics reliability are discussed, respectively, which cover from physics-of-failure analysis of critical power elec-tronic components, state-of-the-art design for reliability process and robustness validation, and intelligent control and condition...
Reliability evaluation of containments including soil-structure interaction
International Nuclear Information System (INIS)
Pires, J.; Hwang, H.; Reich, M.
1985-12-01
Soil-structure interaction effects on the reliability assessment of containment structures are examined. The probability-based method for reliability evaluation of nuclear structures developed at Brookhaven National Laboratory is extended to include soil-structure interaction effects. In this method, reliability of structures is expressed in terms of limit state probabilities. Furthermore, random vibration theory is utilized to calculate limit state probabilities under random seismic loads. Earthquake ground motion is modeled by a segment of a zero-mean, stationary, filtered Gaussian white noise random process, represented by its power spectrum. All possible seismic hazards at a site, represented by a hazard curve, are also included in the analysis. The soil-foundation system is represented by a rigid surface foundation on an elastic halfspace. Random and other uncertainties in the strength properties of the structure, in the stiffness and internal damping of the soil, are also included in the analysis. Finally, a realistic reinforced concrete containment is analyzed to demonstrate the application of the method. For this containment, the soil-structure interaction effects on; (1) limit state probabilities, (2) structural fragility curves, (3) floor response spectra with probabilistic content, and (4) correlation coefficients for total acceleration response at specified structural locations, are examined in detail. 25 refs., 21 figs., 12 tabs
Position Mooring Control Based on a Structural Reliability Criterion
DEFF Research Database (Denmark)
Fang, Shaoji; Leira, Bernt J.; Blanke, Mogens
2013-01-01
is achieved using structural reliability indices in a cost function, where both the mean mooring-line tension and dynamic effects are considered. An optimal set-point is automatically produced without need for manual interaction. The parameters of the extreme value distribution are calculated on-line thereby...... mooring lines simultaneously from exceeding a stress threshold, this paper suggests a new algorithm to determine the reference position and an associated control system. The safety of each line is assessed through a structural reliability index. A reference position where all mooring lines are safe...
Electron scattering and nuclear structure
International Nuclear Information System (INIS)
Frois, B.
1987-01-01
The search for the appropriate degrees of freedom to describe nuclei is the central focus of nuclear physics today. Therefore the authors explore in this review their current understanding of nuclear structure as defined by electromagnetic data. The precision of the electromagnetic probe allows us to define accurately the limits of present theoretical descriptions. The authors review here a broad range of subjects that have been addressed by recent experiments, from the study of meson exchange currents and single-particle distributions to collective excitations in heavy nuclei. However, they do not discuss elastic magnetic scattering, inelastic excitation of discrete states, or single-nucleon knockout reactions since these reactions were recently reviewed. The principal aim of this review is to offer a fresh perspective on nuclear structure, based on the new generation of electron scattering data presented here and in the above-mentioned articles
Reliability analysis of structures under periodic proof tests in service
Yang, J.-N.
1976-01-01
A reliability analysis of structures subjected to random service loads and periodic proof tests treats gust loads and maneuver loads as random processes. Crack initiation, crack propagation, and strength degradation are treated as the fatigue process. The time to fatigue crack initiation and ultimate strength are random variables. Residual strength decreases during crack propagation, so that failure rate increases with time. When a structure fails under periodic proof testing, a new structure is built and proof-tested. The probability of structural failure in service is derived from treatment of all the random variables, strength degradations, service loads, proof tests, and the renewal of failed structures. Some numerical examples are worked out.
Durability reliability analysis for corroding concrete structures under uncertainty
Zhang, Hao
2018-02-01
This paper presents a durability reliability analysis of reinforced concrete structures subject to the action of marine chloride. The focus is to provide insight into the role of epistemic uncertainties on durability reliability. The corrosion model involves a number of variables whose probabilistic characteristics cannot be fully determined due to the limited availability of supporting data. All sources of uncertainty, both aleatory and epistemic, should be included in the reliability analysis. Two methods are available to formulate the epistemic uncertainty: the imprecise probability-based method and the purely probabilistic method in which the epistemic uncertainties are modeled as random variables. The paper illustrates how the epistemic uncertainties are modeled and propagated in the two methods, and shows how epistemic uncertainties govern the durability reliability.
Structural Reliability Aspects in Design of Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2007-01-01
Reliability assessment, optimal design and optimal operation and maintenance of wind turbines are an area of significant interest for the fast growing wind turbine industry for sustainable production of energy. Offshore wind turbines in wind farms give special problems due to wake effects inside...... the farm. Reliability analysis and optimization of wind turbines require that the special conditions for wind turbine operation are taken into account. Control of the blades implies load reductions for large wind speeds and parking for high wind speeds. In this paper basic structural failure modes for wind...... turbines are described. Further, aspects are presented related to reliability-based optimization of wind turbines, assessment of optimal reliability level and operation and maintenance....
Electronic structure of spin systems
Energy Technology Data Exchange (ETDEWEB)
Saha-Dasgupta, Tanusri
2016-04-15
Highlights: • We review the theoretical modeling of quantum spin systems. • We apply the Nth order muffin-tin orbital electronic structure method. • The method shows the importance of chemistry in the modeling. • CuTe{sub 2}O{sub 5} showed a 2-dimensional coupled spin dimer behavior. • Ti substituted Zn{sub 2}VO(PO{sub 4}){sub 2} showed spin gap behavior. - Abstract: Low-dimensional quantum spin systems, characterized by their unconventional magnetic properties, have attracted much attention. Synthesis of materials appropriate to various classes within these systems has made this field very attractive and a site of many activities. The experimental results like susceptibility data are fitted with the theoretical model to derive the underlying spin Hamiltonian. However, often such a fitting procedure which requires correct guess of the assumed spin Hamiltonian leads to ambiguity in deciding the representative model. In this review article, we will describe how electronic structure calculation within the framework of Nth order muffin-tin orbital (NMTO) based Wannier function technique can be utilized to identify the underlying spin model for a large number of such compounds. We will show examples from compounds belonging to vanadates and cuprates.
Reliability Oriented Circuit Design For Power Electronics Applications
DEFF Research Database (Denmark)
Sintamarean, Nicolae Cristian
is presented. Chapter 3 presents the electro-thermal model validation and the reliability studies performed by the proposed tool. The chapter ends with a detailed lifetime analysis, which emphasizes the mission-profile variation and gate-driver parameters variation impact on the PV-inverter devices lifetime......Highly reliable components are required in order to minimize the downtime during the lifetime of the converter and implicitly the maintenance costs. Therefore, the design of high reliable converters under constrained reliability and cost is a great challenge to be overcome in the future....... Moreover, the impact of the mission-profile sampling time on the lifetime estimation accuracy is also determined. The second part of the thesis introduced in Chapter 4, presents a novel gate-driver concept which reduces the dependency of the device power losses variations on the device loading variations...
Reliability analysis of offshore structures using OMA based fatigue stresses
DEFF Research Database (Denmark)
Silva Nabuco, Bruna; Aissani, Amina; Glindtvad Tarpø, Marius
2017-01-01
focus is on the uncertainty observed on the different stresses used to predict the damage. This uncertainty can be reduced by Modal Based Fatigue Monitoring which is a technique based on continuously measuring of the accelerations in few points of the structure with the use of accelerometers known...... points of the structure, the stress history can be calculated in any arbitrary point of the structure. The accuracy of the estimated actual stress is analyzed by experimental tests on a scale model where the obtained stresses are compared to strain gauges measurements. After evaluating the fatigue...... stresses directly from the operational response of the structure, a reliability analysis is performed in order to estimate the reliability of using Modal Based Fatigue Monitoring for long term fatigue studies....
Structural Reliability Methods for Wind Power Converter System Component Reliability Assessment
DEFF Research Database (Denmark)
Kostandyan, Erik; Sørensen, John Dalsgaard
2012-01-01
Wind power converter systems are essential subsystems in both off-shore and on-shore wind turbines. It is the main interface between generator and grid connection. This system is affected by numerous stresses where the main contributors might be defined as vibration and temperature loadings....... The temperature variations induce time-varying stresses and thereby fatigue loads. A probabilistic model is used to model fatigue failure for an electrical component in the power converter system. This model is based on a linear damage accumulation and physics of failure approaches, where a failure criterion...... is defined by the threshold model. The attention is focused on crack propagation in solder joints of electrical components due to the temperature loadings. Structural Reliability approaches are used to incorporate model, physical and statistical uncertainties. Reliability estimation by means of structural...
Neurology objective structured clinical examination reliability using generalizability theory.
Blood, Angela D; Park, Yoon Soo; Lukas, Rimas V; Brorson, James R
2015-11-03
This study examines factors affecting reliability, or consistency of assessment scores, from an objective structured clinical examination (OSCE) in neurology through generalizability theory (G theory). Data include assessments from a multistation OSCE taken by 194 medical students at the completion of a neurology clerkship. Facets evaluated in this study include cases, domains, and items. Domains refer to areas of skill (or constructs) that the OSCE measures. G theory is used to estimate variance components associated with each facet, derive reliability, and project the number of cases required to obtain a reliable (consistent, precise) score. Reliability using G theory is moderate (Φ coefficient = 0.61, G coefficient = 0.64). Performance is similar across cases but differs by the particular domain, such that the majority of variance is attributed to the domain. Projections in reliability estimates reveal that students need to participate in 3 OSCE cases in order to increase reliability beyond the 0.70 threshold. This novel use of G theory in evaluating an OSCE in neurology provides meaningful measurement characteristics of the assessment. Differing from prior work in other medical specialties, the cases students were randomly assigned did not influence their OSCE score; rather, scores varied in expected fashion by domain assessed. © 2015 American Academy of Neurology.
Electronic structure of semiconductor interfaces
Energy Technology Data Exchange (ETDEWEB)
Herman, F
1983-02-01
The study of semiconductor interfaces is one of the most active and exciting areas of current semiconductor research. Because interfaces play a vital role in modern semiconductor technology (integrated circuits, heterojunction lasers, solar cells, infrared detectors, etc.), there is a strong incentive to understand interface properties at a fundamental level and advance existing technology thereby. At the same time, technological advances such as molecular beam epitaxy have paved the way for the fabrication of semiconductor heterojunctions and superlattices of novel design which exhibit unusual electronic, optical, and magnetic properties and offer unique opportunities for fundamental scientific research. A general perspective on this subject is offered treating such topics as the atomic and electronic structure of semiconductor surfaces and interfaces; oxidation and oxide layers; semiconductor heterojunctions and superlattices; rectifying metal-semiconductor contacts; and interface reactions. Recent progress is emphasized and some future directions are indicated. In addition, the role that large-scale scientific computation has played in furthering our theoretical understanding of semiconductor surfaces and interfaces is discussed. Finally, the nature of theoretical models, and the role they play in describing the physical world is considered.
Electronic structure of semiconductor interfaces
International Nuclear Information System (INIS)
Herman, F.
1983-01-01
The study of semiconductor interfaces is one of the most active and exciting areas of current semiconductor research. Because interfaces play a vital role in modern semiconductor technology (integrated circuits, heterojunction lasers, solar cells, infrared detectors, etc.), there is a strong incentive to understand interface properties at a fundamental level and advance existing technology thereby. At the same time, technological advances such as molecular beam epitaxy have paved the way for the fabrication of semiconductor heterojunctions and superlattices of novel design which exhibit unusual electronic, optical, and magnetic properties and offer unique opportunities for fundamental scientific research. A general perspective on this subject is offered treating such topics as the atomic and electronic structure of semiconductor surfaces and interfaces; oxidation and oxide layers; semiconductor heterojunctions and superlattices; rectifying metal-semiconductor contacts; and interface reactions. Recent progress is emphasized and some future directions are indicated. In addition, the role that large-scale scientific computation has played in furthering our theoretical understanding of semiconductor surfaces and interfaces is discussed. Finally, the nature of theoretical models, and the role they play in describing the physical world is considered. (Author) [pt
Condon, David; Revelle, William
2017-01-01
Separating the signal in a test from the irrelevant noise is a challenge for all measurement. Low test reliability limits test validity, attenuates important relationships, and can lead to regression artifacts. Multiple approaches to the assessment and improvement of reliability are discussed. The advantages and disadvantages of several different approaches to reliability are considered. Practical advice on how to assess reliability using open source software is provided.
Overview of humidity driven reliability issues of electronics
DEFF Research Database (Denmark)
Ambat, Rajan
2017-01-01
Electronic control units, power modules, and consumer electronics are used today in a wide variety of varying climatic conditions. Varying external climatic conditions of temperature and humidity can cause an uncontrolled local climate inside the device enclosure. Uncontrolled humidity together w...
Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon
Garion, Cédric
2014-01-01
Despite its good physical properties, the glassy carbon material is not widely used, especially for structural applications. Nevertheless, its transparency to particles and temperature resistance are interesting properties for the applications to vacuum chambers and components in high energy physics. For example, it has been proposed for fast shutter valve in particle accelerator [1] [2]. The mechanical properties have to be carefully determined to assess the reliability of structures in such a material. In this paper, mechanical tests have been carried out to determine the elastic parameters, the strength and toughness on commercial grades. A statistical approach, based on the Weibull’s distribution, is used to characterize the material both in tension and compression. The results are compared to the literature and the difference of properties for these two loading cases is shown. Based on a Finite Element analysis, a statistical approach is applied to define the reliability of a structural component in gl...
Reliability Analysis of Timber Structures through NDT Data Upgrading
DEFF Research Database (Denmark)
Sousa, Hélder; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning
The first part of this document presents, in chapter 2, a description of timber characteristics and common used NDT and MDT for timber elements. Stochastic models for timber properties and damage accumulation models are also referred. According to timber’s properties a framework is proposed...... for a safety reassessment procedure. For that purpose a theoretical background for structural reliability assessment including probabilistic concepts for structural systems and stochastic models are given in chapter 3. System models, both series and parallel systems, are presented as well as methods...... for robustness are dealt in chapter 5. The second part of this document begins in chapter 6, where a practical application of the premise definitions and methodologies is given through the implementation of upgraded models with NDT and MDT data. Structural life-cycle is, therefore, assessed and reliability...
Reliability of structures by using probability and fatigue theories
International Nuclear Information System (INIS)
Lee, Ouk Sub; Kim, Dong Hyeok; Park, Yeon Chang
2008-01-01
Methodologies to calculate failure probability and to estimate the reliability of fatigue loaded structures are developed. The applicability of the methodologies is evaluated with the help of the fatigue crack growth models suggested by Paris and Walker. The probability theories such as the FORM (first order reliability method), the SORM (second order reliability method) and the MCS (Monte Carlo simulation) are utilized. It is found that the failure probability decreases with the increase of the design fatigue life and the applied minimum stress, the decrease of the initial edge crack size, the applied maximum stress and the slope of Paris equation. Furthermore, according to the sensitivity analysis of random variables, the slope of Pairs equation affects the failure probability dominantly among other random variables in the Paris and the Walker models
Seismic reliability assessment methodology for CANDU concrete containment structures
International Nuclear Information System (INIS)
Stephens, M.J.; Nessim, M.A.; Hong, H.P.
1995-05-01
A study was undertaken to develop a reliability-based methodology for the assessment of existing CANDU concrete containment structures with respect to seismic loading. The focus of the study was on defining appropriate specified values and partial safety factors for earthquake loading and resistance parameters. Key issues addressed in the work were the identification of an approach to select design earthquake spectra that satisfy consistent safety levels, and the use of structure-specific data in the evaluation of structural resistance. (author). 23 refs., 9 tabs., 15 figs
MEMS Reliability: Infrastructure, Test Structures, Experiments, and Failure Modes
Energy Technology Data Exchange (ETDEWEB)
TANNER,DANELLE M.; SMITH,NORMAN F.; IRWIN,LLOYD W.; EATON,WILLIAM P.; HELGESEN,KAREN SUE; CLEMENT,J. JOSEPH; MILLER,WILLIAM M.; MILLER,SAMUEL L.; DUGGER,MICHAEL T.; WALRAVEN,JEREMY A.; PETERSON,KENNETH A.
2000-01-01
The burgeoning new technology of Micro-Electro-Mechanical Systems (MEMS) shows great promise in the weapons arena. We can now conceive of micro-gyros, micro-surety systems, and micro-navigators that are extremely small and inexpensive. Do we want to use this new technology in critical applications such as nuclear weapons? This question drove us to understand the reliability and failure mechanisms of silicon surface-micromachined MEMS. Development of a testing infrastructure was a crucial step to perform reliability experiments on MEMS devices and will be reported here. In addition, reliability test structures have been designed and characterized. Many experiments were performed to investigate failure modes and specifically those in different environments (humidity, temperature, shock, vibration, and storage). A predictive reliability model for wear of rubbing surfaces in microengines was developed. The root causes of failure for operating and non-operating MEMS are discussed. The major failure mechanism for operating MEMS was wear of the polysilicon rubbing surfaces. Reliability design rules for future MEMS devices are established.
Reliability-based design code calibration for concrete containment structures
International Nuclear Information System (INIS)
Han, B.K.; Cho, H.N.; Chang, S.P.
1991-01-01
In this study, a load combination criteria for design and a probability-based reliability analysis were proposed on the basis of a FEM-based random vibration analysis. The limit state model defined for the study is a serviceability limit state of the crack failure that causes the emission of radioactive materials, and the results are compared with the case of strength limit state. More accurate reliability analyses under various dynamic loads such as earthquake loads were made possible by incorporating the FEM and random vibration theory, which is different from the conventional reliability analysis method. The uncertainties in loads and resistance available in Korea and the references were adapted to the situation of Korea, and especially in case of earthquake, the design earthquake was assessed based on the available data for the probabilistic description of earthquake ground acceleration in the Korea peninsula. The SAP V-2 is used for a three-dimensional finite element analysis of concrete containment structure, and the reliability analysis is carried out by modifying HRAS reliability analysis program for this study. (orig./GL)
Effects of structural modification on reliability of nanoscale nitride HEMTs
Gaddipati, Vamsi Mohan
AlGaN based nanoscale high-electron-mobility transistors (HEMTs) are the next generation of transistor technology that features the unique combination of higher power, wider bandwidth, low noise, higher efficiency, and temperature/radiation hardness than conventional AlGaAs and Si based technologies. However, as evidenced by recent stress tests, reliability of these devices (characterized by a gradual decrease in the output current/power leading to failure of the device in just tens of hours of operation) remains a major concern. Although, in these tests, physical damages were clearly visible in the device, the root cause and nature of these damages have not yet been fully assessed experimentally. Therefore, a comprehensive theoretical study of the physical mechanisms responsible for degradation of AlGaN HEMTs is essential before these devices are deployed in targeted applications. The main objective of the proposed research is to computationally investigate how degradation of state-of-the-art nanoscale AlGaN HEMTs is governed by an intricate and dynamical coupling of thermo-electromechanical processes at different length (atoms-to-transistor) and time (femtosecondto- hours) scales while operating in high voltage, large mechanical, and high temperature/radiation stresses. This work centers around a novel hypotheses as follows: High voltage applied to AlGaN HEMT causes excessive internal heat dissipation, which triggers gate metal diffusion into the semiconducting barrier layer and structural modifications (defect ii formation) leading to diminished polarization induced charge density and output current. Since the dynamical system to be studied is complex, chaotic (where the evolution rule is guided by atomicity of the underlying material), and involve coupled physical processes, an in-house multiscale simulator (QuADS 3-D) has been employed and augmented, where material parameters are obtained atomistically using firstprinciples, structural relaxation and defect
International Nuclear Information System (INIS)
Leskovar, B.
1980-02-01
The reliability of some electronics components for the Deep Underwater Muon and Neutrino Detection (DUMAND) System is discussed. An introductory overview of engineering concepts and technique for reliability assessment is given. Component reliability is discussed in the contest of major factors causing failures, particularly with respect to physical and chemical causes, process technology and testing, and screening procedures. Failure rates are presented for discrete devices and for integrated circuits as well as for basic electronics components. Furthermore, the military reliability specifications and standards for semiconductor devices are reviewed
Reliability of containment and safety-related structures
International Nuclear Information System (INIS)
Nessim, M.A.
1995-09-01
A research program on Reliability of Containment and Safety-related Structures has been developed and is described in this document. This program is designed to support AECB's regulatory activities aimed at ensuring the safety of these structures. These activities include evaluating submissions by operators and requesting special assessments when necessary. The results of the proposed research will also be useful in revising and enhancing the CSA design standards for containment and safety-related structures. The process of developing the research program started with an information collection and review phase. The sources of information included C-FER's previous work in the area, various recent research publications, regulatory documents and relevant design standards, and a detailed discussion with AECB staff. The second step was to outline the process of reliability evaluation, and identify the required models and parameters. Comparison between the required and available information was used to identify gaps in the state-of-the-art, and the research program was designed to fill these gaps. The program is organized in four major topics, namely: development of an approach for reliability analysis; compilation and development of the required analysis tools; application to specific problems related to design, assessment, maintenance and testing of structures; and testing and validation. It is suggested that the program should be supported by an on-going process of communication and consultation between AECB staff and industry experts. This will lend credibility to the results and facilitate their future application. (author). 1 fig
Reliability and corrosion induced degradation of electronic system
International Nuclear Information System (INIS)
Tapas, V.K.; Varde, P.V.
2014-01-01
This paper describe the corrosion induced degradation of electronic system failures due to environmental conditions such as humidity, temperature, ionic or organic contaminants, residuals; etc. which can accelerates as electrochemical reaction and causes corrosion of electronic components, Corrosive gases and water vapours from humid condition come into contact with the base metal results in buildup of various chemical reaction products. Ionic contamination responsible for electrochemical reaction, forms soluble complexes with metals, it can degrade the protective oxide film that forms on the positively biased metallization and/or lead to change in the local pH. Deterioration of metal components or electronic circuitry due to electrochemical migration needs to be controlled in order to reduce the corrosion. With explosive increase in demand and miniaturization in electronic system resulted in smaller components, closer spacing and thinner metallic path, it is expected that the corrosion and deterioration of electronic components may become cause or concern. This paper summarises the current understanding of chemistry behind possible causes of corrosion of electronic devices and its failure mechanism. (author)
Modelling and estimating degradation processes with application in structural reliability
International Nuclear Information System (INIS)
Chiquet, J.
2007-06-01
The characteristic level of degradation of a given structure is modeled through a stochastic process called the degradation process. The random evolution of the degradation process is governed by a differential system with Markovian environment. We put the associated reliability framework by considering the failure of the structure once the degradation process reaches a critical threshold. A closed form solution of the reliability function is obtained thanks to Markov renewal theory. Then, we build an estimation methodology for the parameters of the stochastic processes involved. The estimation methods and the theoretical results, as well as the associated numerical algorithms, are validated on simulated data sets. Our method is applied to the modelling of a real degradation mechanism, known as crack growth, for which an experimental data set is considered. (authors)
ZERBERUS - the code for reliability analysis of crack containing structures
International Nuclear Information System (INIS)
Cizelj, L.; Riesch-Oppermann, H.
1992-04-01
Brief description of the First- and Second Order Reliability Methods, being the theoretical background of the code, is given. The code structure is described in detail, with special emphasis to the new application fields. The numerical example investigates failure probability of steam generator tubing affected by stress corrosion cracking. The changes necessary to accommodate this analysis within the ZERBERUS code are explained. Analysis results are compared to different Monte Carlo techniques. (orig./HP) [de
An overview of reliability methods in mechanical and structural design
Wirsching, P. H.; Ortiz, K.; Lee, S. J.
1987-01-01
An evaluation is made of modern methods of fast probability integration and Monte Carlo treatment for the assessment of structural systems' and components' reliability. Fast probability integration methods are noted to be more efficient than Monte Carlo ones. This is judged to be an important consideration when several point probability estimates must be made in order to construct a distribution function. An example illustrating the relative efficiency of the various methods is included.
Reliability, Validity and Factor Structure of Drug Abuse Screening Test
Sayed Hadi Sayed Alitabar; Mojtaba Habibi; Maryam Falahatpisheh; Musa Arvin
2016-01-01
Background and Objective: According to the increasing of substance use in the country, more researches about this phenomenon are necessary. This Study Investigates the Validity, Reliability and Confirmatory Factor Structure of the Drug Abuse Screening test (DAST). Materials and Methods: The Sample Consisted of 381 Patients (143 Women and 238 Men) with a Multi-Stage Cluster Sampling of Areas 2, 6 and 12 of Tehran Were Selected from Each Region, 6 Randomly Selected Drug Rehabilitation Center. T...
Time-dependent reliability analysis and condition assessment of structures
International Nuclear Information System (INIS)
Ellingwood, B.R.
1997-01-01
Structures generally play a passive role in assurance of safety in nuclear plant operation, but are important if the plant is to withstand the effect of extreme environmental or abnormal events. Relative to mechanical and electrical components, structural systems and components would be difficult and costly to replace. While the performance of steel or reinforced concrete structures in service generally has been very good, their strengths may deteriorate during an extended service life as a result of changes brought on by an aggressive environment, excessive loading, or accidental loading. Quantitative tools for condition assessment of aging structures can be developed using time-dependent structural reliability analysis methods. Such methods provide a framework for addressing the uncertainties attendant to aging in the decision process
Rapid and reliable protein structure determination via chemical shift threading.
Hafsa, Noor E; Berjanskii, Mark V; Arndt, David; Wishart, David S
2018-01-01
Protein structure determination using nuclear magnetic resonance (NMR) spectroscopy can be both time-consuming and labor intensive. Here we demonstrate how chemical shift threading can permit rapid, robust, and accurate protein structure determination using only chemical shift data. Threading is a relatively old bioinformatics technique that uses a combination of sequence information and predicted (or experimentally acquired) low-resolution structural data to generate high-resolution 3D protein structures. The key motivations behind using NMR chemical shifts for protein threading lie in the fact that they are easy to measure, they are available prior to 3D structure determination, and they contain vital structural information. The method we have developed uses not only sequence and chemical shift similarity but also chemical shift-derived secondary structure, shift-derived super-secondary structure, and shift-derived accessible surface area to generate a high quality protein structure regardless of the sequence similarity (or lack thereof) to a known structure already in the PDB. The method (called E-Thrifty) was found to be very fast (often chemical shift refinement, these results suggest that protein structure determination, using only NMR chemical shifts, is becoming increasingly practical and reliable. E-Thrifty is available as a web server at http://ethrifty.ca .
Reliable protection of electronics against lightning: some practical applications
Laan, van der P.C.T.; Deursen, van A.P.J.
1998-01-01
The classical lightning conductor, which must prevent fire, has to have a sufficiently small resistance. An analogous condition can be formulated for the new challenge: the protection of sensitive electronics against lightning. In this case, the so-called transfer impedance, which gives the
Reliability-Based Structural Optimization of Wave Energy Converters
DEFF Research Database (Denmark)
Ambühl, Simon; Kramer, Morten; Sørensen, John Dalsgaard
2014-01-01
More and more wave energy converter (WEC) concepts are reaching prototype level. Once the prototype level is reached, the next step in order to further decrease the levelized cost of energy (LCOE) is optimizing the overall system with a focus on structural and maintenance (inspection) costs......, as well as on the harvested power from the waves. The target of a fully-developed WEC technology is not maximizing its power output, but minimizing the resulting LCOE. This paper presents a methodology to optimize the structural design of WECs based on a reliability-based optimization problem...
High-Reliable PLC RTOS Development and RPS Structure Analysis
Energy Technology Data Exchange (ETDEWEB)
Sohn, H. S.; Song, D. Y.; Sohn, D. S.; Kim, J. H. [Enersys Co., Daejeon (Korea, Republic of)
2008-04-15
One of the KNICS objectives is to develop a platform for Nuclear Power Plant(NPP) I and C(Instrumentation and Control) system, especially plant protection system. The developed platform is POSAFE-Q and this work supports the development of POSAFE-Q with the development of high-reliable real-time operating system(RTOS) and programmable logic device(PLD) software. Another KNICS objective is to develop safety I and C systems, such as Reactor Protection System(RPS) and Engineered Safety Feature-Component Control System(ESF-CCS). This work plays an important role in the structure analysis for RPS. Validation and verification(V and V) of the safety critical software is an essential work to make digital plant protection system highly reliable and safe. Generally, the reliability and safety of software based system can be improved by strict quality assurance framework including the software development itself. In other words, through V and V, the reliability and safety of a system can be improved and the development activities like software requirement specification, software design specification, component tests, integration tests, and system tests shall be appropriately documented for V and V.
High-Reliable PLC RTOS Development and RPS Structure Analysis
International Nuclear Information System (INIS)
Sohn, H. S.; Song, D. Y.; Sohn, D. S.; Kim, J. H.
2008-04-01
One of the KNICS objectives is to develop a platform for Nuclear Power Plant(NPP) I and C(Instrumentation and Control) system, especially plant protection system. The developed platform is POSAFE-Q and this work supports the development of POSAFE-Q with the development of high-reliable real-time operating system(RTOS) and programmable logic device(PLD) software. Another KNICS objective is to develop safety I and C systems, such as Reactor Protection System(RPS) and Engineered Safety Feature-Component Control System(ESF-CCS). This work plays an important role in the structure analysis for RPS. Validation and verification(V and V) of the safety critical software is an essential work to make digital plant protection system highly reliable and safe. Generally, the reliability and safety of software based system can be improved by strict quality assurance framework including the software development itself. In other words, through V and V, the reliability and safety of a system can be improved and the development activities like software requirement specification, software design specification, component tests, integration tests, and system tests shall be appropriately documented for V and V.
Structural reliability in context of statistical uncertainties and modelling discrepancies
International Nuclear Information System (INIS)
Pendola, Maurice
2000-01-01
Structural reliability methods have been largely improved during the last years and have showed their ability to deal with uncertainties during the design stage or to optimize the functioning and the maintenance of industrial installations. They are based on a mechanical modeling of the structural behavior according to the considered failure modes and on a probabilistic representation of input parameters of this modeling. In practice, only limited statistical information is available to build the probabilistic representation and different sophistication levels of the mechanical modeling may be introduced. Thus, besides the physical randomness, other uncertainties occur in such analyses. The aim of this work is triple: 1. at first, to propose a methodology able to characterize the statistical uncertainties due to the limited number of data in order to take them into account in the reliability analyses. The obtained reliability index measures the confidence in the structure considering the statistical information available. 2. Then, to show a methodology leading to reliability results evaluated from a particular mechanical modeling but by using a less sophisticated one. The objective is then to decrease the computational efforts required by the reference modeling. 3. Finally, to propose partial safety factors that are evolving as a function of the number of statistical data available and as a function of the sophistication level of the mechanical modeling that is used. The concepts are illustrated in the case of a welded pipe and in the case of a natural draught cooling tower. The results show the interest of the methodologies in an industrial context. [fr
Efficiency evaluation of an electronic equipment: availability,reliability and maintenance
International Nuclear Information System (INIS)
Guyot, C.
1966-01-01
This concept of efficiency often called ''system effectiveness'', is presented and analyzed in terms of reliability and maintenance. It allows to define the availability factor of an electronic equipment. A procedure of evaluation is proposed. (A.L.B.)
Reliability data bank in electronics: ITALTEL experience over 10 years of operation
International Nuclear Information System (INIS)
Turconi, G.
1986-01-01
The purpose of this paper is to show the Italtel Reliability Data Bank experience in electronics after ten years from data bank creation. Technological evolution on systems and equipment have originated a reliability data bank evolution in order to maintain and improve its performances. This paper will describe the concepts employed to design the today data bank features enabling it to be an important Company tool for reliability activities. (orig.)
Reliability prediction system based on the failure rate model for electronic components
International Nuclear Information System (INIS)
Lee, Seung Woo; Lee, Hwa Ki
2008-01-01
Although many methodologies for predicting the reliability of electronic components have been developed, their reliability might be subjective according to a particular set of circumstances, and therefore it is not easy to quantify their reliability. Among the reliability prediction methods are the statistical analysis based method, the similarity analysis method based on an external failure rate database, and the method based on the physics-of-failure model. In this study, we developed a system by which the reliability of electronic components can be predicted by creating a system for the statistical analysis method of predicting reliability most easily. The failure rate models that were applied are MILHDBK- 217F N2, PRISM, and Telcordia (Bellcore), and these were compared with the general purpose system in order to validate the effectiveness of the developed system. Being able to predict the reliability of electronic components from the stage of design, the system that we have developed is expected to contribute to enhancing the reliability of electronic components
Reliability-Based Structural Optimization of Wave Energy Converters
Directory of Open Access Journals (Sweden)
Simon Ambühl
2014-12-01
Full Text Available More and more wave energy converter (WEC concepts are reaching prototypelevel. Once the prototype level is reached, the next step in order to further decrease thelevelized cost of energy (LCOE is optimizing the overall system with a focus on structuraland maintenance (inspection costs, as well as on the harvested power from the waves.The target of a fully-developed WEC technology is not maximizing its power output,but minimizing the resulting LCOE. This paper presents a methodology to optimize thestructural design of WECs based on a reliability-based optimization problem and the intentto maximize the investor’s benefits by maximizing the difference between income (e.g., fromselling electricity and the expected expenses (e.g., structural building costs or failure costs.Furthermore, different development levels, like prototype or commercial devices, may havedifferent main objectives and will be located at different locations, as well as receive varioussubsidies. These points should be accounted for when performing structural optimizationsof WECs. An illustrative example on the gravity-based foundation of the Wavestar deviceis performed showing how structural design can be optimized taking target reliability levelsand different structural failure modes due to extreme loads into account.
Reliability-based inspection of prestressed concrete containment structures
International Nuclear Information System (INIS)
Pandey, M.D.
1996-03-01
A study was undertaken to develop a reliability-based approach to the planning of inspection programs for prestressed concrete containment structures. The main function of the prestressing system is to ensure the leak integrity of the containment by maintaining a compressive state of stress under the tensile forces which arise in a hypothesized loss of coolant accident. Prestressing force losses (due to creep and shrinkage, stress relaxation or tendon corrosion) can lead to tensile stresses under accident pressure, resulting in loss of containment leak integrity due to concrete cracking and tensile yielding of the non-prestressed reinforcement. Therefore, the evaluation of prestressing inspection programs was based on their effectiveness in maintaining an acceptable reliability level with respect to a limit state representing yeilding of non-prestressed reinforcement. An annual target reliability of 10 -4 was used for this limit state. As specified in CSA-N287.7, the evaluation of prestressing systems for containment structures is based on the results of lift-off tests to determine the prestressing force. For unbonded systems the tests are carried out on a randomly selected sample from each tendon group in the structure. For bonded systems, the test is carried out on an unbonded test beam that matches the section geometry and material properties of the containment structure. It was found that flexural testing is useful in updating the probability of concrete cracking under accident pressure. For unbonded systems, the analysis indicated that the sample size recommended by the CSA Standard (4% of the tendon population) is adequate. The CSA recommendation for a five year inspection interval is conservative unless severe degradation of the prestressing system, characterized by a high prestressing loss rate (>3%) and a large coefficient of variation of the measured prestressing force (>15%), is observed
Reliability updating based on monitoring of structural response parameters
International Nuclear Information System (INIS)
Leira, B.J.
2016-01-01
Short- and long-term aspects of measuring structural response parameters are addressed. Two specific examples of such measurements are considered for the purpose of illustration and in order to focus the discussion. These examples are taken from the petroleum industry (monitoring of riser response) and from the shipping industry (monitoring of ice-induced strains in a ship hull). Similarities and differences between the two cases are elaborated with respect to which are the most relevant mechanical limit states. Furthermore, main concerns related to reliability levels within a short-term versus long-term time horizon are highlighted. Quantifying the economic benefits of applying monitoring systems is also addressed. - Highlights: • Two examples of structural response monitoring are described. • Application of measurements is discussed in relation to updating of load and structural parameters. • Quantification of the value of response monitoring is made for both of the examples.
Electronic structure of point defects in semiconductors
International Nuclear Information System (INIS)
Bruneval, Fabien
2014-01-01
trace concentration (of the order of one part per million). However, owing to the heavy burden of the quantum-mechanical electronic structure calculations, which grow very rapidly with the number of electrons, the present day simulations do not easily exceed a few hundred atoms nowadays. This induces effective defect concentrations of the order of one percent which are very far from the diluted defects observed in the experiments. The extrapolation of high concentrations to low concentrations is difficult because defects in semiconductors often bear a net electric charge which induces long-range interactions between the spuriously interacting charged defects. The first part of my work presents the techniques available in this area, improvements in the techniques and some understanding of these spurious interactions. The second topic addressed in this memoir focuses on improving the electronic structure of defects in semiconductors and insulators. Defects in these materials introduce discrete electronic levels within the band gap of the pristine bulk material. These electronic levels correspond to the electrons involved in the defect states. Their wave function is more or less localized around the defect region and the filling of the state may also vary with the thermodynamic conditions (Fermi level). These levels inside the band gap govern the modification of the properties of electronic and optical transport. Unfortunately the standard ab initio approaches, in the context of Density Functional Theory (DFT), are unable to get the correct band gaps of semiconductors and insulators. This is why many defect properties cannot be predicted with certainty within these approaches. This second part demonstrates how the introduction of the many-body perturbation theory in the so-called GW approximation solves the problem of band gaps and thus allows one to obtain more reliable defect properties. Of course, the field of ab initio electronic structure for defects is far from being
Electron backscatter diffraction: Strategies for reliable data acquisition and processing
International Nuclear Information System (INIS)
Randle, Valerie
2009-01-01
In electron backscatter diffraction (EBSD) software packages there are many user choices both in data acquisition and in data processing and display. In order to extract maximum scientific value from an inquiry, it is helpful to have some guidelines for best practice in conducting an EBSD investigation. The purpose of this article therefore is to address selected topics of EBSD practice, in a tutorial manner. The topics covered are a brief summary on the principles of EBSD, specimen preparation, calibration of an EBSD system, experiment design, speed of data acquisition, data clean-up, microstructure characterisation (including grain size) and grain boundary characterisation. This list is not meant to cover exhaustively all areas where EBSD is used, but rather to provide a resource consisting of some useful strategies for novice EBSD users.
Directory of Open Access Journals (Sweden)
Hai An
2016-08-01
Full Text Available Aiming to resolve the problems of a variety of uncertainty variables that coexist in the engineering structure reliability analysis, a new hybrid reliability index to evaluate structural hybrid reliability, based on the random–fuzzy–interval model, is proposed in this article. The convergent solving method is also presented. First, the truncated probability reliability model, the fuzzy random reliability model, and the non-probabilistic interval reliability model are introduced. Then, the new hybrid reliability index definition is presented based on the random–fuzzy–interval model. Furthermore, the calculation flowchart of the hybrid reliability index is presented and it is solved using the modified limit-step length iterative algorithm, which ensures convergence. And the validity of convergent algorithm for the hybrid reliability model is verified through the calculation examples in literature. In the end, a numerical example is demonstrated to show that the hybrid reliability index is applicable for the wear reliability assessment of mechanisms, where truncated random variables, fuzzy random variables, and interval variables coexist. The demonstration also shows the good convergence of the iterative algorithm proposed in this article.
Structural reliability analysis applied to pipeline risk analysis
Energy Technology Data Exchange (ETDEWEB)
Gardiner, M. [GL Industrial Services, Loughborough (United Kingdom); Mendes, Renato F.; Donato, Guilherme V.P. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)
2009-07-01
Quantitative Risk Assessment (QRA) of pipelines requires two main components to be provided. These are models of the consequences that follow from some loss of containment incident, and models for the likelihood of such incidents occurring. This paper describes how PETROBRAS have used Structural Reliability Analysis for the second of these, to provide pipeline- and location-specific predictions of failure frequency for a number of pipeline assets. This paper presents an approach to estimating failure rates for liquid and gas pipelines, using Structural Reliability Analysis (SRA) to analyze the credible basic mechanisms of failure such as corrosion and mechanical damage. SRA is a probabilistic limit state method: for a given failure mechanism it quantifies the uncertainty in parameters to mathematical models of the load-resistance state of a structure and then evaluates the probability of load exceeding resistance. SRA can be used to benefit the pipeline risk management process by optimizing in-line inspection schedules, and as part of the design process for new construction in pipeline rights of way that already contain multiple lines. A case study is presented to show how the SRA approach has recently been used on PETROBRAS pipelines and the benefits obtained from it. (author)
Reliability of ultrasound for measurement of selected foot structures.
Crofts, G; Angin, S; Mickle, K J; Hill, S; Nester, C J
2014-01-01
Understanding the relationship between the lower leg muscles, foot structures and function is essential to explain how disease or injury may relate to changes in foot function and clinical pathology. The aim of this study was to investigate the inter-operator reliability of an ultrasound protocol to quantify features of: rear, mid and forefoot sections of the plantar fascia (PF); flexor hallucis brevis (FHB); flexor digitorum brevis (FDB); abductor hallucis (AbH); flexor digitorum longus (FDL); flexor hallucis longus (FHL); tibialis anterior (TA); and peroneus longus and brevis (PER). A sample of 6 females and 4 males (mean age 29.1 ± 7.2 years, mean BMI 25.5 ± 4.8) was recruited from a university student and staff population. Scans were obtained using a portable Venue 40 musculoskeletal ultrasound system (GE Healthcare UK) with a 5-13 MHz wideband linear array probe with a 12.7 mm × 47.1mm footprint by two operators in the same scanning session. Intraclass Correlation Coefficients (ICC) values for muscle thickness (ICC range 0.90-0.97), plantar fascia thickness (ICC range 0.94-0.98) and cross sectional muscle measurements (ICC range 0.91-0.98) revealed excellent inter-operator reliability. The limits of agreement, relative to structure size, ranged from 9.0% to 17.5% for muscle thickness, 11.0-18.0% for plantar fascia, and 11.0-26.0% for cross sectional area measurements. The ultrasound protocol implemented in this work has been shown to be reliable. It therefore offers the opportunity to quantify the structures concerned and better understand their contributions to foot function. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.
Reliability-Based Inspection Planning for Structural Systems
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
1993-01-01
A general model for reliability-based optimal inspection and repair strategies for structural systems is described. The total expected costs in the design lifetime is minimized with the number of inspections, the inspection times and efforts as decision variables. The equivalence of this model...... with a preposterior analysis from statistical decision theory is discussed. It is described how information obtained by an inspection can be used in a repair decision. Stochastic models for inspection, measurement and repair actions are presented. The general model is applied for inspection and repair planning...
Electronic structure studies of fullerites and fullerides
International Nuclear Information System (INIS)
Merkel, M.; Sohmen, E.; Masaki, A.; Romberg, H.; Alexander, M.; Knupfer, M.; Golden, M.S.; Adelmann, P.; Renker, B.; Fink, J.
1993-01-01
The electronic structure of fullerites and fullerides has been investigated by high-resolution photoemission and by high-energy electron energy-loss spectroscopy in transmission. Information on the occupied Π and σ bands, on the unoccupied Π * and σ * bands, and on the joint density of states has been obtained. In particular, we report on the changes of the electronic structure of fullerides as a function of dopant concentration. (orig.)
Solvated electron structure in glassy matrices
International Nuclear Information System (INIS)
Kevan, L.
1981-01-01
Current knowledge of the detailed geometrical structure of solvated electrons in aqueous and organic media is summarized. The geometry of solvated electrons in glassy methanol, ethanol, and 2-methyltetrahydrofuran is discussed. Advanced electron magnetic resonance methods and development of new methods of analysis of electron spin echo modulation patterns, second moment line shapes, and forbidden photon spin-flip transitions for paramagnetic species in these disordered systems are discussed. 66 references are cited
Electronic structure and tautomerism of thioamides
Energy Technology Data Exchange (ETDEWEB)
Novak, Igor, E-mail: inovak@csu.edu.au [Charles Sturt University, POB 883, Orange, NSW 2800 (Australia); Klasinc, Leo, E-mail: klasinc@irb.hr [Physical Chemistry Department, Ruđer Bošković Institute, HR-10002 Zagreb (Croatia); McGlynn, Sean P., E-mail: sean.mcglynn@chemgate.chem.lsu.edu [Louisiana State University, Baton Rouge, LA 70803 (United States)
2016-05-15
Highlights: • Electronic structure of thioamide group and its relation to Lewis basicity. • Tautomerism of the (thio)amide groups. • Substituent effects on the electronic structure of (thio)amide group. - Abstract: The electronic structures of several thioamides have been studied by UV photoelectron spectroscopy (UPS). The relative stabilities of keto–enol tautomers have been determined using high-level ab initio calculations and the results were used in the analysis of UPS spectra. The main features of electronic structure and tautomerism of thioamide derivatives are discussed. The predominant tautomers in the gas phase are of keto–(thio)keto form. The addition of cyclohexanone moiety to the thioamide group enhances the Lewis base character of the sulfur atom. The addition of phenyl group to the (thio)amide group significantly affects its electronic structure.
Out Brief for the Structural Reliability Partnership Workshop
Energy Technology Data Exchange (ETDEWEB)
Boyce, Brad [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Fang, Eliot [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kolski, Alyssa [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zimmerman, Jonathan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Furmanski, Jevan [Exxon Mobil, Annandale, NJ (United States); Ravi-Chandar, Krishnaswamy [Univ. of Texas, Austin, TX (United States)
2017-08-30
The Structural Reliability Partnership Workshop was held in Albuquerque, NM on August 29-30, 2017 and was hosted by Sandia National Laboratories. Attendees were present from academia, industry and several other national laboratories. The workshop kicked off with an introduction to the SRP to familiarize potential members with what the purpose, structure and benefits would be to their organization. Technical overviews were given on several topics by attendees from each sector – national labs, universities and industry – to provide a snapshot of the type of work that is currently being conducted on structural reliability. Attendees were then given the opportunity to suggest and discuss potential Challenge Scenario topics. Three were ultimately decided upon as being the most important: Additive Manufacturing, Hydrogen Pipeline Steels, and Bolted Joined Structures. These were then analyzed using Quad Charts to determine What, How, Who, and Why these areas would be further investigated. Rather than restricting future research to only one area, the option was left open to investigate both the top two, depending on interest and cost associated with hosting such an event. More informal collaboration may be undertaken for the third topic if members have time and interest. Other items discussed pertained to the organization, structure and policies of the Partnership. Topics including Data Management, IP, and mechanisms of partnering/information sharing were touched upon but final decisions were not made. Further action is needed before this can be done. Action items were outlined and assigned, where possible. The next workshop is to be held in early August 2018 in Boulder, CO and is to be hosted by NIST. In the interim, quarterly updates are to take place via WebEx to maintain a line of communication and to ensure progress on both the administrative and technical tasks.
Temple, L Parker
2012-01-01
Implosion is a focused study of the history and uses of high-reliability, solid-state electronics, military standards, and space systems that support our national security and defense. This book is unique in combining the interdependent evolution of and interrelationships among military standards, solid-state electronics, and very high-reliability space systems. Starting with a brief description of the physics that enabled the development of the first transistor, Implosion covers the need for standardizing military electronics, which began during World War II and continu
Design for Reliability of Power Electronics for Grid-Connected Photovoltaic Systems
DEFF Research Database (Denmark)
Yang, Yongheng; Sangwongwanich, Ariya; Blaabjerg, Frede
2016-01-01
Power electronics is the enabling technology for optimizing energy harvesting from renewable systems like Photovoltaic (PV) and wind power systems, and also for interfacing grid-friendly energy systems. Advancements in the power semiconductor technology (e.g., wide band-gap devices) have pushed...... the conversion efficiency of power electronics to above 98%, where however te reliability of power electronics is becoming of high concern. Therefore, it is important to design for reliable power electronic systems to lower the risks of many failures during operation; otherwise will increase the cost...... for maintenance and reputation, thus affecting the cost of PV energy. Today's PV power conversion applications require the power electronic systems with low failure rates during a service life of 20 years or even more. To achieve so, it is vital to know the main life-limiting factors of power electronic systems...
Reliability prediction for structures under cyclic loads and recurring inspections
Directory of Open Access Journals (Sweden)
Alberto W. S. Mello Jr
2009-06-01
Full Text Available This work presents a methodology for determining the reliability of fracture control plans for structures subjected to cyclic loads. It considers the variability of the parameters involved in the problem, such as initial flaw and crack growth curve. The probability of detection (POD curve of the field non-destructive inspection method and the condition/environment are used as important factors for structural confidence. According to classical damage tolerance analysis (DTA, inspection intervals are based on detectable crack size and crack growth rate. However, all variables have uncertainties, which makes the final result totally stochastic. The material properties, flight loads, engineering tools and even the reliability of inspection methods are subject to uncertainties which can affect significantly the final maintenance schedule. The present methodology incorporates all the uncertainties in a simulation process, such as Monte Carlo, and establishes a relationship between the reliability of the overall maintenance program and the proposed inspection interval, forming a “cascade” chart. Due to the scatter, it also defines the confidence level of the “acceptable” risk. As an example, the damage tolerance analysis (DTA results are presented for the upper cockpit longeron splice bolt of the BAF upgraded F-5EM. In this case, two possibilities of inspection intervals were found: one that can be characterized as remote risk, with a probability of failure (integrity nonsuccess of 1 in 10 million, per flight hour; and other as extremely improbable, with a probability of nonsuccess of 1 in 1 billion, per flight hour, according to aviation standards. These two results are compared with the classical military airplane damage tolerance requirements.
Electron scattering and nuclear structure
International Nuclear Information System (INIS)
Wolynec, E.
1985-01-01
A review of the historical development and the theory necessary to the interpretation of the experimental results is made. Some measurement techniques, experimental results and the technique of analysis of these data are presented. Future perspectives, due to the appearence of continous electron current accelerators, in this field of study are discussed. (L.C.) [pt
Electron gun controlled smart structure
Martin, Jeffrey W.; Main, John Alan; Redmond, James M.; Henson, Tammy D.; Watson, Robert D.
2001-01-01
Disclosed is a method and system for actively controlling the shape of a sheet of electroactive material; the system comprising: one or more electrodes attached to the frontside of the electroactive sheet; a charged particle generator, disposed so as to direct a beam of charged particles (e.g. electrons) onto the electrode; a conductive substrate attached to the backside of the sheet; and a power supply electrically connected to the conductive substrate; whereby the sheet changes its shape in response to an electric field created across the sheet by an accumulation of electric charge within the electrode(s), relative to a potential applied to the conductive substrate. Use of multiple electrodes distributed across on the frontside ensures a uniform distribution of the charge with a single point of e-beam incidence, thereby greatly simplifying the beam scanning algorithm and raster control electronics, and reducing the problems associated with "blooming". By placing a distribution of electrodes over the front surface of a piezoelectric film (or other electroactive material), this arrangement enables improved control over the distribution of surface electric charges (e.g. electrons) by creating uniform (and possibly different) charge distributions within each individual electrode. Removal or deposition of net electric charge can be affected by controlling the secondary electron yield through manipulation of the backside electric potential with the power supply. The system can be used for actively controlling the shape of space-based deployable optics, such as adaptive mirrors and inflatable antennae.
Feelings about culture scales: development, factor structure, reliability, and validity.
Maffini, Cara S; Wong, Y Joel
2015-04-01
Although measures of cultural identity, values, and behavior exist in the multicultural psychological literature, there is currently no measure that explicitly assesses ethnic minority individuals' positive and negative affect toward culture. Therefore, we developed 2 new measures called the Feelings About Culture Scale--Ethnic Culture and Feelings About Culture Scale--Mainstream American Culture and tested their psychometric properties. In 6 studies, we piloted the measures, conducted factor analyses to clarify their factor structure, and examined reliability and validity. The factor structure revealed 2 dimensions reflecting positive and negative affect for each measure. Results provided evidence for convergent, discriminant, criterion-related, and incremental validity as well as the reliability of the scales. The Feelings About Culture Scales are the first known measures to examine both positive and negative affect toward an individual's ethnic culture and mainstream American culture. The focus on affect captures dimensions of psychological experiences that differ from cognitive and behavioral constructs often used to measure cultural orientation. These measures can serve as a valuable contribution to both research and counseling by providing insight into the nuanced affective experiences ethnic minority individuals have toward culture. (c) 2015 APA, all rights reserved).
Reliability, Validity and Factor Structure of Drug Abuse Screening Test
Directory of Open Access Journals (Sweden)
Sayed Hadi Sayed Alitabar
2016-05-01
Full Text Available Background and Objective: According to the increasing of substance use in the country, more researches about this phenomenon are necessary. This Study Investigates the Validity, Reliability and Confirmatory Factor Structure of the Drug Abuse Screening test (DAST. Materials and Methods: The Sample Consisted of 381 Patients (143 Women and 238 Men with a Multi-Stage Cluster Sampling of Areas 2, 6 and 12 of Tehran Were Selected from Each Region, 6 Randomly Selected Drug Rehabilitation Center. The DAST Was Used as Instrument. Divergent & Convergent Validity of this Scale Was Assessed with Problems Assessment for Substance Using Psychiatric Patients (PASUPP and Relapse Prediction Scale (RPS.Results: The DAST after the First Time Factor Structure of Using Confirmatory Factor Analysis Was Confirmed. The DAST Had a Good Internal Consistency (Cranach’s Alpha, and the Reliability of the Test Within a Week, 0.9, 0.8. Also this Scale Had a Positive Correlation with Problems Assessment for Substance Using Psychiatric Patients and Relapse Prediction Scale (P<0.01.Conclusion: The Overall Results Showed that the Drug Abuse Screening Test in Iranian Society Is Valid. It Can Be Said that Self-Report Scale Tool Is Useful for Research Purposes and Addiction.
Analysis of NPP protection structure reliability under impact of a falling aircraft
International Nuclear Information System (INIS)
Shul'man, G.S.
1996-01-01
Methodology for evaluation of NPP protection structure reliability by impact of aircraft fall down is considered. The methodology is base on the probabilistic analysis of all potential events. The problem is solved in three stages: determination of loads on structural units, calculation of local reliability of protection structures by assigned loads and estimation of the structure reliability. The methodology proposed may be applied at the NPP design stage and by determination of reliability of already available structures
Reliability-Based Optimal Design for Very Large Floating Structure
Institute of Scientific and Technical Information of China (English)
ZHANG Shu-hua(张淑华); FUJIKUBO Masahiko
2003-01-01
Costs and losses induced by possible future extreme environmental conditions and difficulties in repairing post-yielding damage strongly suggest the need for proper consideration in design rather than just life loss prevention. This can be addressed through the development of design methodology that balances the initial cost of the very large floating structure (VLFS) against the expected potential losses resulting from future extreme wave-induced structural damage. Here, the development of a methodology for determining optimal, cost-effective design will be presented and applied to a VLFS located in the Tokyo bay. Optimal design criteria are determined based on the total expected life-cycle cost and acceptable damage probability and curvature of the structure, and a set of sizes of the structure are obtained. The methodology and applications require expressions of the initial cost and the expected life-cycle damage cost as functions of the optimal design variables. This study includes the methodology, total life-cycle cost function, structural damage modeling, and reliability analysis.
STRUCTURAL STABILITY AND ELECTRONIC STRUCTURE OF ...
African Journals Online (AJOL)
2012-12-31
Dec 31, 2012 ... may be applications at high temperature strength and corrosion ... B2 structure, like that found in cesium-chloride (CsCl) and chemical formula RM, where R denotes a rare - earth element and M denotes a late transition metal ...
Reliability Analysis of Tubular Joints in Offshore Structures
DEFF Research Database (Denmark)
Thoft-Christensen, Palle; Sørensen, John Dalsgaard
1987-01-01
Reliability analysis of single tubular joints and offshore platforms with tubular joints is" presented. The failure modes considered are yielding, punching, buckling and fatigue failure. Element reliability as well as systems reliability approaches are used and illustrated by several examples....... Finally, optimal design of tubular.joints with reliability constraints is discussed and illustrated by an example....
Electronic structure of metallic glasses
International Nuclear Information System (INIS)
Oelhafen, P.; Lapka, R.; Gubler, U.; Krieg, J.; DasGupta, A.; Guentherodt, H.J.; Mizoguchi, T.; Hague, C.; Kuebler, J.; Nagel, S.R.
1981-01-01
This paper is organized in six sections and deals with (1) the glassy transition metal alloys, their d-band structure, the d-band shifts on alloying and their relation to the alloy heat of formation (ΔH) and the glass forming ability, (2) the glass to crystal phase transition viewed by valence band spectroscopy, (3) band structure calculations, (4) metallic glasses prepared by laser glazing, (5) glassy normal metal alloys, and (6) glassy hydrides
Electronic structure and tautomerism of aryl ketones
International Nuclear Information System (INIS)
Novak, Igor; Klasinc, Leo; Šket, Boris; McGlynn, S.P.
2015-01-01
Graphical abstract: Photoelectron spectroscopy, tautomerism. - Highlights: • UV photoelectron spectroscopy of aryl ketones. • The relative stability of tautomers and their electronic structures. • The factors influencing tautomerism. - Abstract: The electronic structures of several aryl ketones (AK) and their α-halo derivatives have been studied by UV photoelectron spectroscopy (UPS). The relative stabilities of keto–enol tautomers have been determined using high-level ab initio calculations and the results were used in the analysis of UPS spectra. The main features of electronic structure and tautomerism of the AK derivatives are discussed
Phenomenology of the electron structure function
International Nuclear Information System (INIS)
Slominski, W.; Szwed, J.
2001-01-01
The advantages of introducing the electron structure function (ESF) in electron induced processes are demonstrated. Contrary to the photon structure function it is directly measured in such processes. At present energies, a simultaneous analysis of both the electron and the photon structure functions gives an important test of the experimentally applied methods. Estimates of the ESF at LEP momenta are given. At very high momenta contributions from W and Z bosons together with γ-Z interference can be observed. Predictions for the next generation of experiments are given. (orig.)
Electronic structure and tautomerism of aryl ketones
Energy Technology Data Exchange (ETDEWEB)
Novak, Igor, E-mail: inovak@csu.edu.au [Charles Sturt University, POB 883, Orange, NSW 2800 (Australia); Klasinc, Leo, E-mail: klasinc@irb.hr [Physical Chemistry Department, Ruđer Bošković Institute, HR-10002 Zagreb (Croatia); Šket, Boris, E-mail: Boris.Sket@fkkt.uni-lj.si [Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 (Slovenia); McGlynn, S.P., E-mail: sean.mcglynn@chemgate.chem.lsu.edu [Louisiana State University, Baton Rouge, LA 70803 (United States)
2015-07-15
Graphical abstract: Photoelectron spectroscopy, tautomerism. - Highlights: • UV photoelectron spectroscopy of aryl ketones. • The relative stability of tautomers and their electronic structures. • The factors influencing tautomerism. - Abstract: The electronic structures of several aryl ketones (AK) and their α-halo derivatives have been studied by UV photoelectron spectroscopy (UPS). The relative stabilities of keto–enol tautomers have been determined using high-level ab initio calculations and the results were used in the analysis of UPS spectra. The main features of electronic structure and tautomerism of the AK derivatives are discussed.
A damage mechanics based approach to structural deterioration and reliability
Energy Technology Data Exchange (ETDEWEB)
Bhattcharya, B.; Ellingwood, B. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Civil Engineering
1998-02-01
Structural deterioration often occurs without perceptible manifestation. Continuum damage mechanics defines structural damage in terms of the material microstructure, and relates the damage variable to the macroscopic strength or stiffness of the structure. This enables one to predict the state of damage prior to the initiation of a macroscopic flaw, and allows one to estimate residual strength/service life of an existing structure. The accumulation of damage is a dissipative process that is governed by the laws of thermodynamics. Partial differential equations for damage growth in terms of the Helmholtz free energy are derived from fundamental thermodynamical conditions. Closed-form solutions to the equations are obtained under uniaxial loading for ductile deformation damage as a function of plastic strain, for creep damage as a function of time, and for fatigue damage as function of number of cycles. The proposed damage growth model is extended into the stochastic domain by considering fluctuations in the free energy, and closed-form solutions of the resulting stochastic differential equation are obtained in each of the three cases mentioned above. A reliability analysis of a ring-stiffened cylindrical steel shell subjected to corrosion, accidental pressure, and temperature is performed.
A damage mechanics based approach to structural deterioration and reliability
International Nuclear Information System (INIS)
Bhattcharya, B.; Ellingwood, B.
1998-02-01
Structural deterioration often occurs without perceptible manifestation. Continuum damage mechanics defines structural damage in terms of the material microstructure, and relates the damage variable to the macroscopic strength or stiffness of the structure. This enables one to predict the state of damage prior to the initiation of a macroscopic flaw, and allows one to estimate residual strength/service life of an existing structure. The accumulation of damage is a dissipative process that is governed by the laws of thermodynamics. Partial differential equations for damage growth in terms of the Helmholtz free energy are derived from fundamental thermodynamical conditions. Closed-form solutions to the equations are obtained under uniaxial loading for ductile deformation damage as a function of plastic strain, for creep damage as a function of time, and for fatigue damage as function of number of cycles. The proposed damage growth model is extended into the stochastic domain by considering fluctuations in the free energy, and closed-form solutions of the resulting stochastic differential equation are obtained in each of the three cases mentioned above. A reliability analysis of a ring-stiffened cylindrical steel shell subjected to corrosion, accidental pressure, and temperature is performed
Reliability algorithms applied to reinforced concrete structures durability assessment
Directory of Open Access Journals (Sweden)
C. G. Nogueira
Full Text Available This paper addresses the analysis of probabilistic corrosion time initiation in reinforced concrete structures exposed to ions chloride penetration. Structural durability is an important criterion which must be evaluated in every type of structure, especially when these structures are constructed in aggressive atmospheres. Considering reinforced concrete members, chloride diffusion process is widely used to evaluate the durability. Therefore, at modelling this phenomenon, corrosion of reinforcements can be better estimated and prevented. These processes begin when a threshold level of chlorides concentration is reached at the steel bars of reinforcements. Despite the robustness of several models proposed in the literature, deterministic approaches fail to predict accurately the corrosion time initiation due to the inherently randomness observed in this process. In this regard, the durability can be more realistically represented using probabilistic approaches. A probabilistic analysis of ions chloride penetration is presented in this paper. The ions chloride penetration is simulated using the Fick's second law of diffusion. This law represents the chloride diffusion process, considering time dependent effects. The probability of failure is calculated using Monte Carlo simulation and the First Order Reliability Method (FORM with a direct coupling approach. Some examples are considered in order to study these phenomena and a simplified method is proposed to determine optimal values for concrete cover.
A Survey on the Reliability of Power Electronics in Electro-Mobility Applications
DEFF Research Database (Denmark)
Gadalla, Brwene Salah Abdelkarim; Schaltz, Erik; Blaabjerg, Frede
2015-01-01
Reliability is an important issue in the field of power electronics since most of the electrical energy is today processed by power electronics. In most of the electro-mobility applications, e.g. electric and hybridelectric vehicles, power electronic are commonly used in very harsh environment...... and extending the service lifetime as well. Research within power electronics is of high interest as it has an important impact in the industry of the electro-mobility applications. According to the aforementioned explanations, this paper will provide an overview of the common factors (thermal cycles, power...... cycles, vibrations, voltage stress and current ripple stress) affecting the reliability of power electronics in electromobility applications. Also, the researchers perspective is summarized from 2001 to 2015....
Epitaxial graphene electronic structure and transport
International Nuclear Information System (INIS)
De Heer, Walt A; Berger, Claire; Wu Xiaosong; Sprinkle, Mike; Hu Yike; Ruan Ming; First, Phillip N; Stroscio, Joseph A; Haddon, Robert; Piot, Benjamin; Faugeras, Clement; Potemski, Marek; Moon, Jeong-Sun
2010-01-01
Since its inception in 2001, the science and technology of epitaxial graphene on hexagonal silicon carbide has matured into a major international effort and is poised to become the first carbon electronics platform. A historical perspective is presented and the unique electronic properties of single and multilayered epitaxial graphenes on electronics grade silicon carbide are reviewed. Early results on transport and the field effect in Si-face grown graphene monolayers provided proof-of-principle demonstrations. Besides monolayer epitaxial graphene, attention is given to C-face grown multilayer graphene, which consists of electronically decoupled graphene sheets. Production, structure and electronic structure are reviewed. The electronic properties, interrogated using a wide variety of surface, electrical and optical probes, are discussed. An overview is given of recent developments of several device prototypes including resistance standards based on epitaxial graphene quantum Hall devices and new ultrahigh frequency analogue epitaxial graphene amplifiers.
Instructional Approach to Molecular Electronic Structure Theory
Dykstra, Clifford E.; Schaefer, Henry F.
1977-01-01
Describes a graduate quantum mechanics projects in which students write a computer program that performs ab initio calculations on the electronic structure of a simple molecule. Theoretical potential energy curves are produced. (MLH)
Analysis of performance reliability of electrical and electronic equipment of car-tractor
Directory of Open Access Journals (Sweden)
Kravchenko О.Р.
2016-08-01
Full Text Available The analysis of the operational reliability of electrical and electronic equipment of vehicles, trucks Mercedes-Benz Actros 1844 LS and Volvo FH 1242, conducting international cargo transportation is performed. It is established that the equipment is reliable, which meets modern requirements, but where there is a violation of the resolution. The reason for repair work is constructive and operational factors. Distribution of efficiency and overall performance of operational reliability is retrieved. Items with more bounce are found. Common factors of violation of efficiency cars, trucks in operation, are largely different stages in warranty runs are obtained.
Reliability analysis of large scaled structures by optimization technique
International Nuclear Information System (INIS)
Ishikawa, N.; Mihara, T.; Iizuka, M.
1987-01-01
This paper presents a reliability analysis based on the optimization technique using PNET (Probabilistic Network Evaluation Technique) method for the highly redundant structures having a large number of collapse modes. This approach makes the best use of the merit of the optimization technique in which the idea of PNET method is used. The analytical process involves the minimization of safety index of the representative mode, subjected to satisfaction of the mechanism condition and of the positive external work. The procedure entails the sequential performance of a series of the NLP (Nonlinear Programming) problems, where the correlation condition as the idea of PNET method pertaining to the representative mode is taken as an additional constraint to the next analysis. Upon succeeding iterations, the final analysis is achieved when a collapse probability at the subsequent mode is extremely less than the value at the 1st mode. The approximate collapse probability of the structure is defined as the sum of the collapse probabilities of the representative modes classified by the extent of correlation. Then, in order to confirm the validity of the proposed method, the conventional Monte Carlo simulation is also revised by using the collapse load analysis. Finally, two fairly large structures were analyzed to illustrate the scope and application of the approach. (orig./HP)
Electron conductance in curved quantum structures
DEFF Research Database (Denmark)
Willatzen, Morten; Gravesen, Jens
2010-01-01
is computationally fast and provides direct (geometrical) parameter insight as regards the determination of the electron transmission coefficient. We present, as a case study, calculations of the electron conductivity of a helically shaped quantum-wire structure and discuss the influence of the quantum......A differential-geometry analysis is employed to investigate the transmission of electrons through a curved quantum-wire structure. Although the problem is a three-dimensional spatial problem, the Schrodinger equation can be separated into three general coordinates. Hence, the proposed method...
Structural Reliability Using Probability Density Estimation Methods Within NESSUS
Chamis, Chrisos C. (Technical Monitor); Godines, Cody Ric
2003-01-01
A reliability analysis studies a mathematical model of a physical system taking into account uncertainties of design variables and common results are estimations of a response density, which also implies estimations of its parameters. Some common density parameters include the mean value, the standard deviation, and specific percentile(s) of the response, which are measures of central tendency, variation, and probability regions, respectively. Reliability analyses are important since the results can lead to different designs by calculating the probability of observing safe responses in each of the proposed designs. All of this is done at the expense of added computational time as compared to a single deterministic analysis which will result in one value of the response out of many that make up the density of the response. Sampling methods, such as monte carlo (MC) and latin hypercube sampling (LHS), can be used to perform reliability analyses and can compute nonlinear response density parameters even if the response is dependent on many random variables. Hence, both methods are very robust; however, they are computationally expensive to use in the estimation of the response density parameters. Both methods are 2 of 13 stochastic methods that are contained within the Numerical Evaluation of Stochastic Structures Under Stress (NESSUS) program. NESSUS is a probabilistic finite element analysis (FEA) program that was developed through funding from NASA Glenn Research Center (GRC). It has the additional capability of being linked to other analysis programs; therefore, probabilistic fluid dynamics, fracture mechanics, and heat transfer are only a few of what is possible with this software. The LHS method is the newest addition to the stochastic methods within NESSUS. Part of this work was to enhance NESSUS with the LHS method. The new LHS module is complete, has been successfully integrated with NESSUS, and been used to study four different test cases that have been
Electronic structure and optical properties of metal doped tetraphenylporphyrins
Shah, Esha V.; Roy, Debesh R.
2018-05-01
A density functional scrutiny on the structure, electronic and optical properties of metal doped tetraphenylporphyrins MTPP (M=Fe, Co, Ni) is performed. The structural stability of the molecules is evaluated based on the electronic parameters like HOMO-LUMO gap (HLG), chemical hardness (η) and binding energy of the central metal atom to the molecular frame etc. The computed UltraViolet-Visible (UV-Vis) optical absorption spectra for all the compounds are also compared. The molecular structures reported are the lowest energy configurations. The entire calculations are carried out with a widely reliable functional, viz. B3LYP with a popular basis set which includes a scaler relativistic effect, viz. LANL2DZ.
Overview of nuclear structure with electrons
International Nuclear Information System (INIS)
Geesaman, D. F.
1999-01-01
Following a broad summary of the author's view of nuclear structure in 1974, he will discuss the key elements they have learned in the past 25 years from the research at the M.I.T. Bates Linear Accelerator center and its sister electron accelerator laboratories. Electron scattering has provided the essential measurements for most of the progress. The future is bright for nuclear structure research as their ability to realistically calculate nuclear structure observables has dramatically advanced and they are increasingly able to incorporate an understanding of quantum chromodynamics into their picture of the nucleus
Quality and reliability assurance of electronic components in small-scale and middle-sized plants
International Nuclear Information System (INIS)
Becker, P.
1982-01-01
Electronic components are forever finding their way into new fields of application and have an ever increasing influence on the quality and reliability of the products in which they are used. The user has very negligible influence on the production methods used for the manufacture of the components and the element properties. (orig.) [de
DEFF Research Database (Denmark)
Verdingovas, Vadimas
were to a significant extent guided by the climatic reliability issues the electronic companies are currently facing. The research in this thesis is focused on the synergistic effects of process related contamination, humidity, potential bias, and PCBA design related aspects, while various tests...... assuming parasitic circuit due to water layer formation on the PCBA surface. The chapters 2-5 review the factors influencing the climatic reliability of electronics namely humidity interaction with materials and ionic contamination on the PCBA surface, common types and sources of ionic contamination...... in electronics, the test methods and techniques, and failure mechanisms related to climate and contamination. Chapter 6 summarizes the materials and experimental methods employed in this thesis. The results of various investigations are presented as individual research papers as published or in the draft form...
The effect of corrosion on the structural reliability of steel offshore structures
International Nuclear Information System (INIS)
Melchers, Robert E.
2005-01-01
This paper considers essential theoretical concepts and data requirements for engineering structural reliability assessment suitable for the estimation of the safety and reliability of corroding ships, offshore structures and pipelines. Such infrastructure operates in a harsh environment. Allowance must be made for structural deterioration since protective measures such as paint coatings, galvanizing or cathodic protection may be ineffective. Reliability analysis requires accurate engineering models for the description and prediction of material corrosion loss and for the maximum depth of pitting. New probability-based models for both these forms of corrosion have been proposed recently and calibrated against a wide range of data. The effects of water velocity and of water pollution are reviewed and compared with recently reported field data for a corrosion at an offshore oil platform. The data interpreted according to the model show good correlation when allowance is made for the season of first immersion and the adverse effects of seawater velocity and of water pollution. An example is given to illustrate the application of reliability analysis to a pipeline subject to pitting corrosion. An important outcome is that good quality estimation of the longer-term probability of loss of structural integrity requires good modelling of the longer-term corrosion behaviour. This is usually associated with anaerobic corrosion. As a result, it cannot be extrapolated from data for short-term corrosion as this is associated with aerobic corrosion conditions
The effect of corrosion on the structural reliability of steel offshore structures
Energy Technology Data Exchange (ETDEWEB)
Melchers, Robert E. [Centre for Infrastructure Performance and Reliability, Department of Civil, Surveying and Environmental Engineering, School of Engineering, University of Newcastle, University Drive, Callaghan NSW 2300 (Australia)]. E-mail: rob.melchers@newcastle.edu.au
2005-10-01
This paper considers essential theoretical concepts and data requirements for engineering structural reliability assessment suitable for the estimation of the safety and reliability of corroding ships, offshore structures and pipelines. Such infrastructure operates in a harsh environment. Allowance must be made for structural deterioration since protective measures such as paint coatings, galvanizing or cathodic protection may be ineffective. Reliability analysis requires accurate engineering models for the description and prediction of material corrosion loss and for the maximum depth of pitting. New probability-based models for both these forms of corrosion have been proposed recently and calibrated against a wide range of data. The effects of water velocity and of water pollution are reviewed and compared with recently reported field data for a corrosion at an offshore oil platform. The data interpreted according to the model show good correlation when allowance is made for the season of first immersion and the adverse effects of seawater velocity and of water pollution. An example is given to illustrate the application of reliability analysis to a pipeline subject to pitting corrosion. An important outcome is that good quality estimation of the longer-term probability of loss of structural integrity requires good modelling of the longer-term corrosion behaviour. This is usually associated with anaerobic corrosion. As a result, it cannot be extrapolated from data for short-term corrosion as this is associated with aerobic corrosion conditions.
Development on methods for evaluating structure reliability of piping components
International Nuclear Information System (INIS)
Schimpfke, T.; Grebner, H.; Peschke, J.; Sievers, J.
2003-01-01
In the frame of the German reactor safety research program of the Federal Ministry of Economics and Labour, GRS has started to develop an analysis code named PROST (PRObabilistic STructure analysis) for estimating the leak and break probabilities of piping systems in nuclear power plants. The development is based on the experience achieved with applications of the public available US code PRAISE 3.10 (Piping Reliability Analysis Including Seismic Events), which was supplemented by additional features regarding the statistical evaluation and the crack orientation. PROST is designed to be more flexible to changes and supplementations. Up to now it can be used for calculating fatigue problems. The paper mentions the main capabilities and theoretical background of the present PROST development and presents a parametric study on the influence by changing the method of stress intensity factor and limit load calculation and the statistical evaluation options on the leak probability of an exemplary pipe with postulated axial crack distribution. Furthermore the resulting leak probability of an exemplary pipe with postulated circumferential crack distribution is compared with the results of the modified PRAISE computer program. The intention of this investigation is to show trends. Therefore the resulting absolute values for probabilities should not be considered as realistic evaluations. (author)
Electronic Structure of Eu6C60
Institute of Scientific and Technical Information of China (English)
WANG Xiao-Xiong; LI Hong-Nian; XU Ya-Bo; WANG Peng; ZHANG Wen-Hua; XU Fa-Qiang
2009-01-01
We study the valence band of Eu-intercalated C60 by synchrotron radiation photoelectron spectroscopy to un-derstand the ferromagnetism (FM) and the giant magnetoresistance (GMR) of Eu6C60. The results reveal the semiconducting property and the remarkable 5d6s-π hybridization. Eu-C60 bonding has both ionic and covalent contributions. No more than half the 5d6s electrons transfer from Eu to the LUMO derived band of C60, and the LUMO+1 derived band is not filled. The remaining valence electrons of Eu, together with some π (LUMO, HOMO and HOMO-1) electrons, constitute the covalent bond. The electronic structure implies that the magnetic coupling in Eu6C60 should be through the intra-atomic f-sd exchange and the medium of the π electrons. The possibility of the GMR being tunnelling magnetoresistance is ruled out.
Atomic and electronic structures of novel silicon surface structures
Energy Technology Data Exchange (ETDEWEB)
Terry, J.H. Jr.
1997-03-01
The modification of silicon surfaces is presently of great interest to the semiconductor device community. Three distinct areas are the subject of inquiry: first, modification of the silicon electronic structure; second, passivation of the silicon surface; and third, functionalization of the silicon surface. It is believed that surface modification of these types will lead to useful electronic devices by pairing these modified surfaces with traditional silicon device technology. Therefore, silicon wafers with modified electronic structure (light-emitting porous silicon), passivated surfaces (H-Si(111), Cl-Si(111), Alkyl-Si(111)), and functionalized surfaces (Alkyl-Si(111)) have been studied in order to determine the fundamental properties of surface geometry and electronic structure using synchrotron radiation-based techniques.
Structural changes induced by electron irradiation
International Nuclear Information System (INIS)
Koike, J.; Pedraza, D.F.
1993-01-01
Highly oriented pyrolytic graphite was irradiated at room temperature with 300 kV electrons. Transmission electron microscopy and electron energy loss spectroscopy were employed to study the structural changes produced by irradiation. The occurrence of a continuous ring intensity in the selected area diffraction (SAD) pattern obtained on a specimen irradiated with the electron beam parallel to the c-crystallographic axis indicated that microstructural changes had occurred. However, from the SAD pattern obtained for the specimens tilted relative to the irradiation direction, it was found that up to a fluence of 1.1x10 27 e/m 2 graphite remained crystalline. An SAD pattern of a specimen irradiated with the electron beam perpendicular to the c-axis confirmed the persistence of crystalline order. High resolution electron microscopy showed that ordering along the c-axis direction remained. A density reduction of 8.9% due to irradiation was determined from the plasmon frequency shift. A qualitative model is proposed to explain these observations. A new determination of the threshold displacement energy, Ed, of carbon atoms in graphite was done by examining the appearance of a continuous ring in the SAD pattern at various electron energies. A value of 30 eV was obtained whether the incident electron beam was parallel or perpendicular to the c-axis, demonstrating that Ed is independent of the displacement direction
Design for reliability in power electronics in renewable energy systems – status and future
DEFF Research Database (Denmark)
Wang, Huai; Blaabjerg, Frede; Ma, Ke
2013-01-01
Advances in power electronics enable efficient and flexible interconnection of renewable sources, loads and electric grids. While targets concerning efficiency of power converters are within reach, recent research endeavors to predict and improve their reliability to ensure high availability, low...... maintenance costs, and herefore, low Levelized-Cost-of-Energy (LCOE) of renewable energy systems. This paper presents the prior-art Design for Reliability (DFR) process for power converters and addresses the paradigm shift to Physics-of-Failure (PoF) approach and mission profile based analysis. Moreover...
Thermal Management and Reliability of Automotive Power Electronics and Electric Machines
Energy Technology Data Exchange (ETDEWEB)
Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bennion, Kevin S [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Cousineau, Justine E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); DeVoto, Douglas J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Feng, Xuhui [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Kekelia, Bidzina [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Kozak, Joseph P [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Major, Joshua [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Moreno, Gilberto [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Paret, Paul P [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Tomerlin, Jeff J [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2018-02-09
Low-cost, high-performance thermal management technologies are helping meet aggressive power density, specific power, cost, and reliability targets for power electronics and electric machines. The National Renewable Energy Laboratory is working closely with numerous industry and research partners to help influence development of components that meet aggressive performance and cost targets through development and characterization of cooling technologies, and thermal characterization and improvements of passive stack materials and interfaces. Thermomechanical reliability and lifetime estimation models are important enablers for industry in cost-and time-effective design.
Assessment of Electronic Circuits Reliability Using Boolean Truth Table Modeling Method
International Nuclear Information System (INIS)
EI-Shanshoury, A.I.
2011-01-01
This paper explores the use of Boolean Truth Table modeling Method (BTTM) in the analysis of qualitative data. It is widely used in certain fields especially in the fields of electrical and electronic engineering. Our work focuses on the evaluation of power supply circuit reliability using (BTTM) which involves systematic attempts to falsify and identify hypotheses on the basis of truth tables constructed from qualitative data. Reliability parameters such as the system's failure rates for the power supply case study are estimated. All possible state combinations (operating and failed states) of the major components in the circuit were listed and their effects on overall system were studied
Structural stability and electronic structure of YCu ductile ...
African Journals Online (AJOL)
We investigate the structural, elastic and electronic properties of cubic YCu intermetallic compound. Which crystallize in the CsCl- B2 type structure, the investigated using the first principle full potential linearized augmented plane wave method (FP-LAPW) within density functional Theory (DFT). We used generalized ...
CARES/PC - CERAMICS ANALYSIS AND RELIABILITY EVALUATION OF STRUCTURES
Szatmary, S. A.
1994-01-01
The beneficial properties of structural ceramics include their high-temperature strength, light weight, hardness, and corrosion and oxidation resistance. For advanced heat engines, ceramics have demonstrated functional abilities at temperatures well beyond the operational limits of metals. This is offset by the fact that ceramic materials tend to be brittle. When a load is applied, their lack of significant plastic deformation causes the material to crack at microscopic flaws, destroying the component. CARES/PC performs statistical analysis of data obtained from the fracture of simple, uniaxial tensile or flexural specimens and estimates the Weibull and Batdorf material parameters from this data. CARES/PC is a subset of the program CARES (COSMIC program number LEW-15168) which calculates the fast-fracture reliability or failure probability of ceramic components utilizing the Batdorf and Weibull models to describe the effects of multi-axial stress states on material strength. CARES additionally requires that the ceramic structure be modeled by a finite element program such as MSC/NASTRAN or ANSYS. The more limited CARES/PC does not perform fast-fracture reliability estimation of components. CARES/PC estimates ceramic material properties from uniaxial tensile or from three- and four-point bend bar data. In general, the parameters are obtained from the fracture stresses of many specimens (30 or more are recommended) whose geometry and loading configurations are held constant. Parameter estimation can be performed for single or multiple failure modes by using the least-squares analysis or the maximum likelihood method. Kolmogorov-Smirnov and Anderson-Darling goodness-of-fit tests measure the accuracy of the hypothesis that the fracture data comes from a population with a distribution specified by the estimated Weibull parameters. Ninety-percent confidence intervals on the Weibull parameters and the unbiased value of the shape parameter for complete samples are provided
Optimization and Reliability Problems in Structural Design of Wind Turbines
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
2007-01-01
are discussed. Limit state equations are presented for fatigue limit states and for ultimate limit states with extreme wind load, and illustrated by bending failure. Illustrative examples are presented, and as a part of the results optimal reliability levels are obtained which corresponds to an annual...... reliability index equal to 3. An example with fatigue failure indicates that the reliability level is almost the same for single wind turbines and for wind turbines in wind farms if the wake effects are modeled equivalently in the design equation and the limit state equation....
Electron acoustic nonlinear structures in planetary magnetospheres
Shah, K. H.; Qureshi, M. N. S.; Masood, W.; Shah, H. A.
2018-04-01
In this paper, we have studied linear and nonlinear propagation of electron acoustic waves (EAWs) comprising cold and hot populations in which the ions form the neutralizing background. The hot electrons have been assumed to follow the generalized ( r , q ) distribution which has the advantage that it mimics most of the distribution functions observed in space plasmas. Interestingly, it has been found that unlike Maxwellian and kappa distributions, the electron acoustic waves admit not only rarefactive structures but also allow the formation of compressive solitary structures for generalized ( r , q ) distribution. It has been found that the flatness parameter r , tail parameter q , and the nonlinear propagation velocity u affect the propagation characteristics of nonlinear EAWs. Using the plasmas parameters, typically found in Saturn's magnetosphere and the Earth's auroral region, where two populations of electrons and electron acoustic solitary waves (EASWs) have been observed, we have given an estimate of the scale lengths over which these nonlinear waves are expected to form and how the size of these structures would vary with the change in the shape of the distribution function and with the change of the plasma parameters.
Structure of conduction electrons on polysilanes
Energy Technology Data Exchange (ETDEWEB)
Ichikawa, Tsuneki [Hokkaido Univ., Sapporo (Japan); Kumagai, Jun
1998-10-01
The orbital structures of conduction electrons on permethylated oligosilane, Si{sub 2n}(CH{sub 3}){sub 2n+2}(n = 2 - 8), and poly(cyclohexylmethylsilane) have been determined by the electron spin-echo envelope modulation signals of the radical anions of these silanes in a deuterated rigid matrix at 77 K. The conduction electron on permethylated oligosilane is delocalized over the entire main chain, whereas that on poly(cyclohexylmethylsilane) is localized on a part of the main chain composed of about six Si atoms. Quantum-chemical calculations suggest that Anderson localization due to fluctuation of {sigma} conjugation by conformational disorder of the main chain is responsible for the localization of both the conduction electron and the hole. (author)
Indian Academy of Sciences (India)
Abstract. Results of ab initio electronic structure calculations on the compound MgB2 using the. FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, c/a ratio and the bulk modulus, all of which are in excellent ...
Electronic structure of Fe-based superconductors
Indian Academy of Sciences (India)
Abstract. Fe-based superconductors have drawn much attention during the last decade due to the presence of superconductivity in materials containing the magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested the dominant ...
Electronic structure of Fe-based superconductors
Indian Academy of Sciences (India)
2015-05-29
May 29, 2015 ... Fe-based superconductors have drawn much attention during the last decade due to the presence of superconductivity in materials containing the magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested the ...
Indian Academy of Sciences (India)
Results of ab initio electronic structure calculations on the compound MgB2 using the FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with ...
The electronic structure of antiferromagnetic chromium
DEFF Research Database (Denmark)
Skriver, Hans Lomholt
1981-01-01
The author has used the local spin density formalism to perform self-consistent calculations of the electronic structure of chromium in the non-magnetic and commensurate antiferromagnetic phases, as a function of the lattice parameter. A change of a few per cent in the atomic radius brings...
Electronic structure calculations of calcium silicate hydrates
International Nuclear Information System (INIS)
Sterne, P.A.; Meike, A.
1995-11-01
Many phases in the calcium-silicate-hydrate system can develop in cement exposed over long periods of time to temperatures above 25 C. As a consequence, chemical reactions involving these phases can affect the relative humidity and water chemistry of a radioactive waste repository that contains significant amounts of cement. In order to predict and simulate these chemical reactions, the authors are developing an internally consistent database of crystalline Ca-Si-hydrate structures. The results of first principles electronic structure calculations on two such phases, wollastonite (CaSiO 3 ) and xonotlite (Ca 6 Si 6 O 17 (OH) 2 ), are reported here. The calculated ground state properties are in very good agreement with experiment, providing equilibrium lattice parameters within about 1--1.4% of the experimentally reported values. The roles of the different types of oxygen atoms, which are fundamental to understanding the energetics of crystalline Ca-Si-hydrates are briefly discussed in terms of their electronic state densities. The good agreement with experiment for the lattice parameters and the consistency of the electronic density of states features for the two structures demonstrate the applicability of these electronic structure methods in calculating the fundamental properties of these phases
Reliability of Capacitors for DC-Link Applications in Power Electronic Converters
DEFF Research Database (Denmark)
Wang, Huai; Blaabjerg, Frede
2014-01-01
DC-link capacitors are an important part in the majority of power electronic converters which contribute to cost, size and failure rate on a considerable scale. From capacitor users' viewpoint, this paper presents a review on the improvement of reliability of dc link in power electronic converters...... from two aspects: 1) reliability-oriented dc-link design solutions; 2) conditioning monitoring of dc-link capacitors during operation. Failure mechanisms, failure modes and lifetime models of capacitors suitable for the applications are also discussed as a basis to understand the physics......-of-failure. This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their dc-link applications....
Electronic structure and electron dynamics at Si(100)
Energy Technology Data Exchange (ETDEWEB)
Weinelt, M. [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Festkoerperphysik, Erlangen (Germany); Max-Born-Institut, Berlin (Germany); Kutschera, M.; Schmidt, R.; Orth, C.; Fauster, T. [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Festkoerperphysik, Erlangen (Germany); Rohlfing, M. [International University Bremen, School of Engineering and Science, P.O. Box 750 561, Bremen (Germany)
2005-02-01
The electronic structure and electron dynamics at a Si(100) surface is studied by two-photon photoemission (2PPE). At 90 K the occupied D{sub up} dangling-bond state is located 150{+-}50 meV below the valence-band maximum (VBM) at the center of the surface Brillouin zone anti {gamma} and exhibits an effective hole mass of (0.5{+-}0.15)m{sub e}. The unoccupied D{sub down} band has a local minimum at anti {gamma} at 650{+-}50 meV above the VBM and shows strong dispersion along the dimer rows of the c(4 x 2) reconstructed surface. At 300 K the D{sub down} position shifts comparable to the Si conduction-band minimum by 40 meV to lower energies but the dispersion of the dangling-bond states is independent of temperature. The surface band bending for p-doped silicon is less than 30 meV, while acceptor-type defects cause significant and preparation-dependent band bending on n-doped samples. 2PPE spectra of Si(100) are dominated by interband transitions between the occupied and unoccupied surface states and emission out of transiently and permanently charged surface defects. Including electron-hole interaction in many-body calculations of the quasi-particle band structure leads us to assign a dangling-bond split-off state to a quasi-one-dimensional surface exciton with a binding energy of 130 meV. Electrons resonantly excited to the unoccupied D{sub down} dangling-bond band with an excess energy of about 350 meV need 1.5{+-}0.2 ps to scatter via phonon emission to the band bottom at anti {gamma} and relax within 5 ps with an excited hole in the occupied surface band to form an exciton living for nanoseconds. (orig.)
Partial Safety Factors and Target Reliability Level in Danish Structural Codes
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Hansen, J. O.; Nielsen, T. A.
2001-01-01
The partial safety factors in the newly revised Danish structural codes have been derived using a reliability-based calibration. The calibrated partial safety factors result in the same average reliability level as in the previous codes, but a much more uniform reliability level has been obtained....... The paper describes the code format, the stochastic models and the resulting optimised partial safety factors....
Diamond surface: atomic and electronic structure
International Nuclear Information System (INIS)
Pate, B.B.
1984-01-01
Experimental studies of the diamond surface (with primary emphasis on the (111) surface) are presented. Aspects of the diamond surface which are addressed include (1) the electronic structure, (2) the atomic structure, and (3) the effect of termination of the lattice by foreign atoms. Limited studies of graphite are discussed for comparison with the diamond results. Experimental results from valence band and core level photoemission spectroscopy (PES), Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and carbon 1s near edge x-ray absorption fine structure (NEXAFS) spectroscopy (both the total electron yield (TEY) and Auger electron yield (AEY) techniques) are used to study and characterize both the clean and hydrogenated surface. In addition, the interaction of hydrogen with the diamond surface is examined using results from vibrational high resolution low energy electron loss spectroscopy (in collaboration with Waclawski, Pierce, Swanson, and Celotta at the National Bureau of Standards) and photon stimulated ion desorption (PSID) yield at photon energies near the carbon k-edge (hv greater than or equal to 280 eV). Both EELS and PSID verify that the mechanically polished 1 x 1 surface is hydrogen terminated and also that the reconstructed surface is hydrogen free. The (111) 2 x 2/2 x 1 reconstructed surface is obtained from the hydrogenated (111) 1 x 1:H surface by annealing to approx. = 1000 0 C. We observe occupied intrinsic surface states and a surface chemical shift (0.95 +- 0.1 eV) to lower binding energy of the carbon 1s level on the hydrogen-free reconstructed surface. Atomic hydrogen is found to be reactive with the reconstructed surface, while molecular hydrogen is relatively inert. Exposure of the reconstructed surface to atomic hydrogen results in chemisorption of hydrogen and removal of the intrinsic surface state emission in and near the band gap region
Electronic structure and electron momentum density in TiSi
Energy Technology Data Exchange (ETDEWEB)
Ghaleb, A.M. [Department of Physics, College of Science, University of Kirkuk, Kirkuk (Iraq); Mohammad, F.M. [Department of Physics, College of Science, University of Tikreet, Tikreet (Iraq); Sahariya, Jagrati [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Sharma, Mukesh [Physics Division, Forensic Science Laboratory, Jaipur, Rajasthan (India); Ahuja, B.L., E-mail: blahuja@yahoo.com [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India)
2013-03-01
We report the electron momentum density in titanium monosilicide using {sup 241}Am Compton spectrometer. Experimental Compton profile has been compared with the theoretical profiles computed using linear combination of atomic orbitals (LCAO). The energy bands, density of states and Fermi surface structures of TiSi are reported using the LCAO and the full potential linearized augmented plane wave methods. Theoretical anisotropies in directional Compton profiles are interpreted in terms of energy bands. To confirm the conducting behavior, we also report the real space analysis of experimental Compton profile of TiSi.
Extented second moment algebra as an efficient tool in structural reliability
International Nuclear Information System (INIS)
Ditlevsen, O.
1982-01-01
During the seventies, second moment structural reliability analysis was extensively discussed with respect to philosophy and method. One recent clarification into a consistent formalism is represented by the extended second moment reliability theory with the generalized reliability index as its measure of safety. Its methods of formal failure probability calculations are useful independent of the opinion that one may adopt about the philosophy of the second moment reliability formalism. After an introduction of the historical development of the philosphy the paper gives a short introductory review of the extended second moment structural reliability theory. (orig.)
Analysis of time-dependent reliability of degenerated reinforced concrete structure
Directory of Open Access Journals (Sweden)
Zhang Hongping
2016-07-01
Full Text Available Durability deterioration of structure is a highly random process. The maintenance of degenerated structure involves the calculation of the reliability of time-dependent structure. This study introduced reinforced concrete structure resistance decrease model and related statistical parameters of uncertainty, analyzed resistance decrease rules of corroded bending element of reinforced concrete structure, and finally calculated timedependent reliability of the corroded bending element of reinforced concrete structure, aiming to provide a specific theoretical basis for the application of time-dependent reliability theory.
Total Longitudinal Moment Calculation and Reliability Analysis of Yacht Structures
Zhi, Wenzheng; Lin, Shaofen
In order to check the reliability of the yacht in FRP (Fiber Reinforce Plastic) materials, in this paper, the vertical force and the calculation method of the overall longitudinal bending moment on yacht was analyzed. Specially, this paper focuses on the impact of speed on the still water bending moment on yacht. Then considering the mechanical properties of the cap type stiffeners in composite materials, the ultimate bearing capacity of the yacht has been worked out, finally the reliability of the yacht was calculated with using response surface methodology. The result can be used in yacht design and yacht driving.
Maalderink, H.H.H.; Bruning, F.B.J.; Schipper, M.M.R. de; Werff, J.J.J. van der; Germs, W.W.C.; Remmers, J.J.C.; Meinders, E.R.
2018-01-01
The need for personalised and smart products drives the development of structural electronics with mass-customisation capability. A number of challenges need to be overcome in order to address the potential of complete free form manufacturing of electronic devices. One key challenge is the
Maalderink, H.H.; Bruning, F.B.J.; de Schipper, M.R.; van der Werff, J.J.; Germs, W.C.; Remmers, J.J.C.; Meinders, E.R.
2018-01-01
The need for personalised and smart products drives the development of structural electronics with mass-customisation capability. A number of challenges need to be overcome in order to address the potential of complete free form manufacturing of electronic devices. One key challenge is the
Electronic structure of super heavy atoms revisited
International Nuclear Information System (INIS)
Gitman, D M; Levin, A D; Tyutin, I V; Voronov, B L
2013-01-01
The electronic structure of an atom with Z ⩽ Z c = 137 can be described by the Dirac equation with the Coulomb field of a point charge Ze. It was believed that the Dirac equation with Z > Z c poses difficulties because the formula for the lower energy level of the Dirac Hamiltonian formally gives imaginary eigenvalues. But a strict mathematical consideration shows that difficulties with the electronic spectrum for Z > Z c do not arise if the Dirac Hamiltonian is correctly defined as a self-adjoint operator. In this paper, we briefly summarize the main physical results of that consideration in a form suitable for physicists with some additional new details and numerical calculations of the electronic spectra. (comment)
Electronic Structure of Strongly Correlated Materials
Anisimov, Vladimir
2010-01-01
Electronic structure and physical properties of strongly correlated materials containing elements with partially filled 3d, 4d, 4f and 5f electronic shells is analyzed by Dynamical Mean-Field Theory (DMFT). DMFT is the most universal and effective tool used for the theoretical investigation of electronic states with strong correlation effects. In the present book the basics of the method are given and its application to various material classes is shown. The book is aimed at a broad readership: theoretical physicists and experimentalists studying strongly correlated systems. It also serves as a handbook for students and all those who want to be acquainted with fast developing filed of condensed matter physics.
Level III Reliability methods feasible for complex structures
Waarts, P.H.; Boer, A. de
2001-01-01
The paper describes the comparison between three types of reliability methods: code type level I used by a designer, full level I and a level III method. Two cases that are typical for civil engineering practise, a cable-stayed subjected to traffic load and the installation of a soil retaining sheet
Reliability Based Calibration of Fatigue Design Guidelines for Ship Structures
DEFF Research Database (Denmark)
Folsø, Rasmus; Otto, S.; Parmentier, G.
2002-01-01
A simple reliability based framework is applied to calibrate a new set of fatigue design guidelines. This new guideline considers two different approaches for the assessment of both loads, stresses and local stress raising effects, and partial safety factors must be given for any combination...
Reliability of redundant ductile structures with uncertain system ...
Indian Academy of Sciences (India)
tance, applied loads and geometric parameters, and in some cases in the .... Statistical dependence among (i) girder strengths ... element reliability solution techniques; such formulation unfortunately remains ..... The spread of plasticity through a member after failure of a section .... The following form of the bivariate Gumbel.
Electronic band structures of binary skutterudites
International Nuclear Information System (INIS)
Khan, Banaras; Aliabad, H.A. Rahnamaye; Saifullah; Jalali-Asadabadi, S.; Khan, Imad; Ahmad, Iftikhar
2015-01-01
The electronic properties of complex binary skutterudites, MX 3 (M = Co, Rh, Ir; X = P, As, Sb) are explored, using various density functional theory (DFT) based theoretical approaches including Green's Function (GW) as well as regular and non-regular Tran Blaha modified Becke Jhonson (TB-mBJ) methods. The wide range of calculated bandgap values for each compound of this skutterudites family confirm that they are theoretically as challenging as their experimental studies. The computationally expensive GW method, which is generally assume to be efficient in the reproduction of the experimental bandgaps, is also not very successful in the calculation of bandgaps. In this article, the issue of the theoretical bandgaps of these compounds is resolved by reproducing the accurate experimental bandgaps, using the recently developed non-regular TB-mBJ approach, based on DFT. The effectiveness of this technique is due to the fact that a large volume of the binary skutterudite crystal is empty and hence quite large proportion of electrons lie outside of the atomic spheres, where unlike LDA and GGA which are poor in the treatment of these electrons, this technique properly treats these electrons and hence reproduces the clear electronic picture of these compounds. - Highlights: • Theoretical and experimental electronic band structures of binary skutterudites are reviewed. • The literature reveals that none of the existing theoretical results are consistent with the experiments. • GW, regular and non-regular TB-mBJ methods are used to reproduce the correct results. • The GW and regular TB-mBJ results are better than the available results in literature. • However, non-regular TB-mBJ reproduces the correct experimental band structures
Electronic band structures of binary skutterudites
Energy Technology Data Exchange (ETDEWEB)
Khan, Banaras [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Aliabad, H.A. Rahnamaye [Department of Physics, Hakim Sabzevari University, Sabzevar (Iran, Islamic Republic of); Saifullah [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Jalali-Asadabadi, S. [Department of Physics, Faculty of Science, University of Isfahan (UI), 81744 Isfahan (Iran, Islamic Republic of); Khan, Imad [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Ahmad, Iftikhar, E-mail: ahma5532@gmail.com [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan)
2015-10-25
The electronic properties of complex binary skutterudites, MX{sub 3} (M = Co, Rh, Ir; X = P, As, Sb) are explored, using various density functional theory (DFT) based theoretical approaches including Green's Function (GW) as well as regular and non-regular Tran Blaha modified Becke Jhonson (TB-mBJ) methods. The wide range of calculated bandgap values for each compound of this skutterudites family confirm that they are theoretically as challenging as their experimental studies. The computationally expensive GW method, which is generally assume to be efficient in the reproduction of the experimental bandgaps, is also not very successful in the calculation of bandgaps. In this article, the issue of the theoretical bandgaps of these compounds is resolved by reproducing the accurate experimental bandgaps, using the recently developed non-regular TB-mBJ approach, based on DFT. The effectiveness of this technique is due to the fact that a large volume of the binary skutterudite crystal is empty and hence quite large proportion of electrons lie outside of the atomic spheres, where unlike LDA and GGA which are poor in the treatment of these electrons, this technique properly treats these electrons and hence reproduces the clear electronic picture of these compounds. - Highlights: • Theoretical and experimental electronic band structures of binary skutterudites are reviewed. • The literature reveals that none of the existing theoretical results are consistent with the experiments. • GW, regular and non-regular TB-mBJ methods are used to reproduce the correct results. • The GW and regular TB-mBJ results are better than the available results in literature. • However, non-regular TB-mBJ reproduces the correct experimental band structures.
An automatic chip structure optical inspection system for electronic components
Song, Zhichao; Xue, Bindang; Liang, Jiyuan; Wang, Ke; Chen, Junzhang; Liu, Yunhe
2018-01-01
An automatic chip structure inspection system based on machine vision is presented to ensure the reliability of electronic components. It consists of four major modules, including a metallographic microscope, a Gigabit Ethernet high-resolution camera, a control system and a high performance computer. An auto-focusing technique is presented to solve the problem that the chip surface is not on the same focusing surface under the high magnification of the microscope. A panoramic high-resolution image stitching algorithm is adopted to deal with the contradiction between resolution and field of view, caused by different sizes of electronic components. In addition, we establish a database to storage and callback appropriate parameters to ensure the consistency of chip images of electronic components with the same model. We use image change detection technology to realize the detection of chip images of electronic components. The system can achieve high-resolution imaging for chips of electronic components with various sizes, and clearly imaging for the surface of chip with different horizontal and standardized imaging for ones with the same model, and can recognize chip defects.
Electronic structure of Pu carbides: photoelectron spectroscopy
Czech Academy of Sciences Publication Activity Database
Gouder, T.; Havela, L.; Shick, Alexander; Huber, F.
2008-01-01
Roč. 403, č. 5-9 (2008), s. 852-853 ISSN 0921-4526 R&D Projects: GA AV ČR(CZ) IAA100100530 Grant - others:EU(XE) RITA -CT-2006-026176 Institutional research plan: CEZ:AV0Z10100520 Keywords : photoemission * electronic structure * plutonium Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.822, year: 2008
Structural and electronic properties of thallium compounds
International Nuclear Information System (INIS)
Paliwal, Neetu; Srivastava, Vipul
2016-01-01
The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of thallium pnictides TlX (X=Sb, Bi) at high pressure. As a function of volume, the total energy is evaluated. Apart from this, the lattice parameter (a_0), bulk modulus (B_0), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in TlSb and TlBi compounds. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.
Structural and electronic properties of thallium compounds
Energy Technology Data Exchange (ETDEWEB)
Paliwal, Neetu, E-mail: neetumanish@gmail.com [Department of Physics, AISECT University Bhopal, 464993 (India); Srivastava, Vipul [Department of Engineering Physics, NRI Institute of Research & Technology, Raisen Road, Bhopal, 462021 (India)
2016-05-06
The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of thallium pnictides TlX (X=Sb, Bi) at high pressure. As a function of volume, the total energy is evaluated. Apart from this, the lattice parameter (a{sub 0}), bulk modulus (B{sub 0}), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in TlSb and TlBi compounds. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.
Martowicz, Adam; Uhl, Tadeusz
2012-10-01
The paper discusses the applicability of a reliability- and performance-based multi-criteria robust design optimization technique for micro-electromechanical systems, considering their technological uncertainties. Nowadays, micro-devices are commonly applied systems, especially in the automotive industry, taking advantage of utilizing both the mechanical structure and electronic control circuit on one board. Their frequent use motivates the elaboration of virtual prototyping tools that can be applied in design optimization with the introduction of technological uncertainties and reliability. The authors present a procedure for the optimization of micro-devices, which is based on the theory of reliability-based robust design optimization. This takes into consideration the performance of a micro-device and its reliability assessed by means of uncertainty analysis. The procedure assumes that, for each checked design configuration, the assessment of uncertainty propagation is performed with the meta-modeling technique. The described procedure is illustrated with an example of the optimization carried out for a finite element model of a micro-mirror. The multi-physics approach allowed the introduction of several physical phenomena to correctly model the electrostatic actuation and the squeezing effect present between electrodes. The optimization was preceded by sensitivity analysis to establish the design and uncertain domains. The genetic algorithms fulfilled the defined optimization task effectively. The best discovered individuals are characterized by a minimized value of the multi-criteria objective function, simultaneously satisfying the constraint on material strength. The restriction of the maximum equivalent stresses was introduced with the conditionally formulated objective function with a penalty component. The yielded results were successfully verified with a global uniform search through the input design domain.
International Nuclear Information System (INIS)
Stewart, Mark G.; Al-Harthy, Ali
2008-01-01
A stochastic analysis is developed to assess the temporal and spatial variability of pitting corrosion on the reliability of corroding reinforced concrete (RC) structures. The structure considered herein is a singly reinforced RC beam with Y16 or Y27 reinforcing bars. Experimental data obtained from corrosion tests are used to characterise the probability distribution of pit depth. The RC beam is discretised into a series of small elements and maximum pit depths are generated for each reinforcing steel bar in each element. The loss of cross-sectional area, reduction in yield strength and reduction in flexural resistance are then inferred. The analysis considers various member spans, loading ratios, bar diameters and numbers of bars in a given cross-section, and moment diagrams. It was found that the maximum corrosion loss in a reinforcing bar conditional on beam collapse was no more than 16%. The probabilities of failure considering spatial variability of pitting corrosion were up to 200% higher than probabilities of failure obtained from a non-spatial analysis after 50 years of corrosion. This shows the importance of considering spatial variability in a structural reliability analysis for deteriorating structures, particularly for corroding RC beams in flexure
DEFF Research Database (Denmark)
Iwankiewicz, R.; Nielsen, Søren R. K.; Skjærbæk, P. S.
The subject of the paper is the investigation of the sensitivity of structural reliability estimation by a reduced hysteretic model for a reinforced concrete frame under an earthquake excitation.......The subject of the paper is the investigation of the sensitivity of structural reliability estimation by a reduced hysteretic model for a reinforced concrete frame under an earthquake excitation....
Reliability and service life of wood structures and buildings
Directory of Open Access Journals (Sweden)
Zdeňka Havířová
2005-01-01
Full Text Available Service life of constructions and buildings of wood is dependent on temperature and moisture conditions in layers of the building cladding where the wood framework is built in. Temperature/moisture conditions or the corresponding equilibrium moisture content (EMC of the construction show considerable effects on the functional reliability of the whole building from the viewpoint of mechanical resistance and stability (ER1, energy savings and thermal protection (ER6 and hygiene, health and environment protection (ER3. To ensure the reliability of constructions and buildings for the period of their supposed service life a more profound analysis of constructions is necessary from the aspect of a global thermal/technical evaluation.
Reliability and service life of wood structures and buildings
Zdeňka Havířová; Pavel Kubů
2005-01-01
Service life of constructions and buildings of wood is dependent on temperature and moisture conditions in layers of the building cladding where the wood framework is built in. Temperature/moisture conditions or the corresponding equilibrium moisture content (EMC) of the construction show considerable effects on the functional reliability of the whole building from the viewpoint of mechanical resistance and stability (ER1), energy savings and thermal protection (ER6) and hygiene, health and e...
Correlated electronic structure of CeN
Energy Technology Data Exchange (ETDEWEB)
Panda, S.K., E-mail: swarup.panda@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Di Marco, I. [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Delin, A. [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); KTH Royal Institute of Technology, School of Information and Communication Technology, Department of Materials and Nano Physics, Electrum 229, SE-164 40 Kista (Sweden); KTH Royal Institute of Technology, Swedish e-Science Research Center (SeRC), SE-100 44 Stockholm (Sweden); Eriksson, O., E-mail: olle.eriksson@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden)
2016-04-15
Highlights: • The electronic structure of CeN is studied within the GGA+DMFT approach using SPTF and Hubbard I approximation. • 4f spectral functions from SPTF and Hubbard I are coupled to explain the various spectroscopic manifestations of CeN. • The calculated XPS and BIS spectra show good agreement with the corresponding experimental spectra. • The contribution of the various l-states and the importance of cross-sections for the photoemission process are analyzed. - Abstract: We have studied in detail the electronic structure of CeN including spin orbit coupling (SOC) and electron–electron interaction, within the dynamical mean-field theory combined with density-functional theory in generalized gradient approximation (GGA+DMFT). The effective impurity problem has been solved through the spin-polarized T-matrix fluctuation-exchange (SPTF) solver and the Hubbard I approximation (HIA). The calculated l-projected atomic partial densities of states and the converged potential were used to obtain the X-ray-photoemission-spectra (XPS) and Bremstrahlung Isochromat spectra (BIS). Following the spirit of Gunnarsson–Schonhammer model, we have coupled the SPTF and HIA 4f spectral functions to explain the various spectroscopic manifestations of CeN. Our computed spectra in such a coupled scheme explain the experimental data remarkably well, establishing the validity of our theoretical model in analyzing the electronic structure of CeN. The contribution of the various l-states in the total spectra and the importance of cross sections are also analyzed in detail.
Electronic structure theory of the superheavy elements
Energy Technology Data Exchange (ETDEWEB)
Eliav, Ephraim, E-mail: ephraim@tau.ac.il [School of Chemistry, Tel Aviv University, 6997801 Tel Aviv (Israel); Fritzsche, Stephan, E-mail: s.fritzsche@gsi.de [Helmholtz-Institut Jena, Fröbelstieg 3, D-07743 Jena (Germany); Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, D-07743 Jena (Germany); Kaldor, Uzi, E-mail: kaldor@tau.ac.il [School of Chemistry, Tel Aviv University, 6997801 Tel Aviv (Israel)
2015-12-15
High-accuracy calculations of atomic properties of the superheavy elements (SHE) up to element 122 are reviewed. The properties discussed include ionization potentials, electron affinities and excitation energies, which are associated with the spectroscopic and chemical behavior of these elements, and are therefore of considerable interest. Accurate predictions of these quantities require high-order inclusion of relativity and electron correlation, as well as large, converged basis sets. The Dirac–Coulomb–Breit Hamiltonian, which includes all terms up to second order in the fine-structure constant α, serves as the framework for the treatment; higher-order Lamb shift terms are considered in some selected cases. Electron correlation is treated by either the multiconfiguration self-consistent-field approach or by Fock-space coupled cluster theory. The latter is enhanced by the intermediate Hamiltonian scheme, allowing the use of larger model (P) spaces. The quality of the calculations is assessed by applying the same methods to lighter homologs of the SHEs and comparing with available experimental information. Very good agreement is obtained, within a few hundredths of an eV, and similar accuracy is expected for the SHEs. Many of the properties predicted for the SHEs differ significantly from what may be expected by straightforward extrapolation of lighter homologs, demonstrating that the structure and chemistry of SHEs are strongly affected by relativity. The major scientific challenge of the calculations is to find the electronic structure and basic atomic properties of the SHE and assign its proper place in the periodic table. Significant recent developments include joint experimental–computational studies of the excitation spectrum of Fm and the ionization energy of Lr, with excellent agreement of experiment and theory, auguring well for the future of research in the field.
The Reliability of Electronic Health Record Data Used for Obstetrical Research.
Altman, Molly R; Colorafi, Karen; Daratha, Kenn B
2018-01-01
Hospital electronic health record (EHR) data are increasingly being called upon for research purposes, yet only recently has it been tested to examine its reliability. Studies that have examined reliability of EHR data for research purposes have varied widely in methods used and field of inquiry, with little reporting of the reliability of perinatal and obstetric variables in the current literature. To assess the reliability of data extracted from a commercially available inpatient EHR as compared with manually abstracted data for common attributes used in obstetrical research. Data extracted through automated EHR reports for 3,250 women who delivered a live infant at a large hospital in the Pacific Northwest were compared with manual chart abstraction for the following perinatal measures: delivery method, labor induction, labor augmentation, cervical ripening, vertex presentation, and postpartum hemorrhage. Almost perfect agreement was observed for all four modes of delivery (vacuum assisted: kappa = 0.92; 95% confidence interval [CI] = 0.88-0.95, forceps assisted: kappa = 0.90; 95%CI = 0.76-1.00, cesarean delivery: kappa = 0.91; 95%CI = 0.90-0.93, and spontaneous vaginal delivery: kappa = 0.91; 95%CI = 0.90-0.93). Cervical ripening demonstrated substantial agreement (kappa = 0.77; 95%CI = 0.73-0.80); labor induction (kappa = 0.65; 95%CI = 0.62-0.68) and augmentation (kappa = 0.54; 95%CI = 0.49-0.58) demonstrated moderate agreement between the two data sources. Vertex presentation (kappa = 0.35; 95%CI = 0.31-0.40) and post-partum hemorrhage (kappa = 0.21; 95%CI = 0.13-0.28) demonstrated fair agreement. Our study demonstrates variability in the reliability of obstetrical data collected and reported through the EHR. While delivery method was satisfactorily reliable in our sample, other examined perinatal measures were less so when compared with manual chart abstraction. The use of multiple
An Energy-Based Limit State Function for Estimation of Structural Reliability in Shock Environments
Directory of Open Access Journals (Sweden)
Michael A. Guthrie
2013-01-01
Full Text Available limit state function is developed for the estimation of structural reliability in shock environments. This limit state function uses peak modal strain energies to characterize environmental severity and modal strain energies at failure to characterize the structural capacity. The Hasofer-Lind reliability index is briefly reviewed and its computation for the energy-based limit state function is discussed. Applications to two degree of freedom mass-spring systems and to a simple finite element model are considered. For these examples, computation of the reliability index requires little effort beyond a modal analysis, but still accounts for relevant uncertainties in both the structure and environment. For both examples, the reliability index is observed to agree well with the results of Monte Carlo analysis. In situations where fast, qualitative comparison of several candidate designs is required, the reliability index based on the proposed limit state function provides an attractive metric which can be used to compare and control reliability.
Spectral-Product Methods for Electronic Structure Calculations (Preprint)
National Research Council Canada - National Science Library
Langhoff, P. W; Mills, J. E; Boatz, J. A
2006-01-01
.... The spectral-product approach to molecular electronic structure avoids the repeated evaluations of the one- and two-electron integrals required in construction of polyatomic Hamiltonian matrices...
Spectral-Product Methods for Electronic Structure Calculations (Postprint)
National Research Council Canada - National Science Library
Langhoff, P. W; Hinde, R. J; Mills, J. D; Boatz, J. A
2007-01-01
.... The spectral-product approach to molecular electronic structure avoids the repeated evaluations of the one- and two-electron integrals required in construction of polyatomic Hamiltonian matrices...
Electronic structure and superconductivity of europium
International Nuclear Information System (INIS)
Nixon, Lane W.; Papaconstantopoulos, D.A.
2010-01-01
We have calculated the electronic structure of Eu for the bcc, hcp, and fcc crystal structures for volumes near equilibrium up to a calculated 90 GPa pressure using the augmented-plane-wave method in the local-density approximation. The frozen-core approximation was used with a semi-empirical shift of the f-states energies in the radial Schroedinger equation to move the occupied 4f valence states below the Γ 1 energy and into the core. This shift of the highly localized f-states yields the correct europium phase ordering with lattice parameters and bulk moduli in good agreement with experimental data. The calculated superconductivity properties under pressure for the bcc and hcp structures are also found to agree with and follow a T c trend similar to recent measurement by Debessai et al.
Electromagnetic Radiation of Electrons in Periodic Structures
Potylitsyn, Alexander Petrovich
2011-01-01
Periodic magnetic structures (undulators) are widely used in accelerators to generate monochromatic undulator radiation (UR) in the range from far infrared to the hard X-ray region. Another periodic crystalline structure is used to produce quasimonochromatic polarized photon beams via the coherent bremsstrahlung mechanism (CBS). Due to such characteristics as monochromaticity, polarization and adjustability, these types of radiation is of large interest for applied and basic research of accelerator-emitted radiation. The book provides a detailed overview of the fundamental principles behind electromagnetic radiation emitted from accelerated charged particles (e.g. UR, CBS, radiation of fast electrons in Laser flash fields) as well as a unified description of relatively new radiation mechanisms which attracted great interest in recent years. This are the so-called polarization radiation excited by the Coulomb field of incident particles in periodic structures, parametric X-rays, resonant transition radiation a...
Boson structure functions from inelastic electron scattering
International Nuclear Information System (INIS)
De Jager, C.W.
1986-01-01
The even /sup 104-110/Pd isotopes and /sup 196/Pt have been investigated at NIKHEF-K by high-resolution inelastic electron scattering. A new IBA-2 calculation has been performed for the Pd isotopes, in which the ratio of the proton and neutron coupling constants is taken from pion scattering. One set of boson structure functions sufficed for the description of the first and second E2-excitations in all Pd isotopes. The data showed no sensitivity for different structure functions for proton and neutron bosons. A preliminary analysis of a number of negative parity states (3/sup -/,5/sup -/ and 7/sup -/), observed in /sup 196/Pt, was performed through the introduction of an f-boson. The first E4-excitation in the palladium isotopes can be reasonably described with a β-structure function, but all other E4-excitations require the introduction of g-boson admixtures
Photoelectron spectroscopy bulk and surface electronic structures
Suga, Shigemasa
2014-01-01
Photoelectron spectroscopy is now becoming more and more required to investigate electronic structures of various solid materials in the bulk, on surfaces as well as at buried interfaces. The energy resolution was much improved in the last decade down to 1 meV in the low photon energy region. Now this technique is available from a few eV up to 10 keV by use of lasers, electron cyclotron resonance lamps in addition to synchrotron radiation and X-ray tubes. High resolution angle resolved photoelectron spectroscopy (ARPES) is now widely applied to band mapping of materials. It attracts a wide attention from both fundamental science and material engineering. Studies of the dynamics of excited states are feasible by time of flight spectroscopy with fully utilizing the pulse structures of synchrotron radiation as well as lasers including the free electron lasers (FEL). Spin resolved studies also made dramatic progress by using higher efficiency spin detectors and two dimensional spin detectors. Polarization depend...
Electronic Structures of LNA Phosphorothioate Oligonucleotides
Directory of Open Access Journals (Sweden)
Henrik G. Bohr
2017-09-01
Full Text Available Important oligonucleotides in anti-sense research have been investigated in silico and experimentally. This involves quantum mechanical (QM calculations and chromatography experiments on locked nucleic acid (LNA phosphorothioate (PS oligonucleotides. iso-potential electrostatic surfaces are essential in this study and have been calculated from the wave functions derived from the QM calculations that provide binding information and other properties of these molecules. The QM calculations give details of the electronic structures in terms of e.g., energy and bonding, which make them distinguish or differentiate between the individual PS diastereoisomers determined by the position of sulfur atoms. Rules are derived from the electronic calculations of these molecules and include the effects of the phosphorothioate chirality and formation of electrostatic potential surfaces. Physical and electrochemical descriptors of the PS oligonucleotides are compared to the experiments in which chiral states on these molecules can be distinguished. The calculations demonstrate that electronic structure, electrostatic potential, and topology are highly sensitive to single PS configuration changes and can give a lead to understanding the activity of the molecules. Keywords: LNA phosphorothioate, DNA/LNA oligonucleotide, diastereoisomers, Hartree-Fock calculations, iso-potential surface, anion chromatograms
Extraordinary electronic properties in uncommon structure types
Ali, Mazhar Nawaz
In this thesis I present the results of explorations into several uncommon structure types. In Chapter 1 I go through the underlying idea of how we search for new compounds with exotic properties in solid state chemistry. The ideas of exploring uncommon structure types, building up from the simple to the complex, using chemical intuition and thinking by analogy are discussed. Also, the history and basic concepts of superconductivity, Dirac semimetals, and magnetoresistance are briefly reviewed. In chapter 2, the 1s-InTaS2 structural family is introduced along with the discovery of a new member of the family, Ag0:79VS2; the synthesis, structure, and physical properties of two different polymorphs of the material are detailed. Also in this chapter, we report the observation of superconductivity in another 1s structure, PbTaSe2. This material is especially interesting due to it being very heavy (resulting in very strong spin orbit coulping (SOC)), layered, and noncentrosymmetric. Electronic structure calculations reveal the presence of a bulk 3D Dirac cone (very similar to graphene) that is gapped by SOC originating from the hexagonal Pb layer. In Chapter 3 we show the re-investigation of the crystal structure of the 3D Dirac semimetal, Cd3As2. It is found to be centrosymmetric, rather than noncentrosymmetric, and as such all bands are spin degenerate and there is a 4-fold degenerate bulk Dirac point at the Fermi level, making Cd3As2 a 3D electronic analog to graphene. Also, for the first time, scanning tunneling microscopy experiments identify a 2x2 surface reconstruction in what we identify as the (112) cleavage plane of single crystals; needle crystals grow with a [110] long axis direction. Lastly, in chapter 4 we report the discovery of "titanic" (sadly dubbed ⪉rge, nonsaturating" by Nature editors and given the acronym XMR) magnetoresistance (MR) in the non-magnetic, noncentrosymmetric, layered transition metal dichalcogenide WTe2; over 13 million% at 0.53 K in
Projected quasiparticle theory for molecular electronic structure
Scuseria, Gustavo E.; Jiménez-Hoyos, Carlos A.; Henderson, Thomas M.; Samanta, Kousik; Ellis, Jason K.
2011-09-01
We derive and implement symmetry-projected Hartree-Fock-Bogoliubov (HFB) equations and apply them to the molecular electronic structure problem. All symmetries (particle number, spin, spatial, and complex conjugation) are deliberately broken and restored in a self-consistent variation-after-projection approach. We show that the resulting method yields a comprehensive black-box treatment of static correlations with effective one-electron (mean-field) computational cost. The ensuing wave function is of multireference character and permeates the entire Hilbert space of the problem. The energy expression is different from regular HFB theory but remains a functional of an independent quasiparticle density matrix. All reduced density matrices are expressible as an integration of transition density matrices over a gauge grid. We present several proof-of-principle examples demonstrating the compelling power of projected quasiparticle theory for quantum chemistry.
Studies in the electronic structure of matter
International Nuclear Information System (INIS)
Swarts, C.A.
1979-01-01
The results of various theories for the angular distribution of electrons photoemitted from the outermost p-shell of rare gas atoms are compared. The theories compared are the local density theories of Slater (X/sub α/) and of Hohenberg, Kohn and Sham, the pseudopotential method, Hartree-Fock theory as evaluated by Kennedy and Manson, and Amusia's random phase approximation with exchange (RPAE). Extended Huekel theory is applied to GaAs, GaP, and to the nitrogen isoelectronic trap in GaAs and GaP. The computer perfect crystal band structures are found to be in reasonable agreement with those computed with empirical pseudopotentials. Nitrogen impurity levels in GaAs and GaP are calculated using a cluster model. By means of model calculations for an independent electron metal, exact lineshapes are obtained for the photon absorption, emission and photoemission spectra of deep core states. 97 references
On the use of NDT Data for Reliability-Based Assessment of Existing Timber Structures
DEFF Research Database (Denmark)
Sousa, Hélder S.; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning
2013-01-01
The objective of this paper is to address the possibilities of using non-destructive testing (NDT) data for updating information and obtaining adequate characterization of the reliability level of existing timber structures and, also, for assessing the evolution in time of performance...... of these structures when exposed to deterioration. By improving the knowledge upon the mechanical properties of timber, better and more substantiated decisions after a reliability safety assessment are aimed at. Bayesian methods are used to update the mechanical properties of timber and reliability assessment......, and information of NDT is also used to calibrate these models. The proposed approach is used for reliability assessment of different structural timber systems. Reliability of the structural system is assessed regarding the failure consequences of individual elements defined as key elements which were determined...
Reliability Analysis of Sealing Structure of Electromechanical System Based on Kriging Model
Zhang, F.; Wang, Y. M.; Chen, R. W.; Deng, W. W.; Gao, Y.
2018-05-01
The sealing performance of aircraft electromechanical system has a great influence on flight safety, and the reliability of its typical seal structure is analyzed by researcher. In this paper, we regard reciprocating seal structure as a research object to study structural reliability. Having been based on the finite element numerical simulation method, the contact stress between the rubber sealing ring and the cylinder wall is calculated, and the relationship between the contact stress and the pressure of the hydraulic medium is built, and the friction force on different working conditions are compared. Through the co-simulation, the adaptive Kriging model obtained by EFF learning mechanism is used to describe the failure probability of the seal ring, so as to evaluate the reliability of the sealing structure. This article proposes a new idea of numerical evaluation for the reliability analysis of sealing structure, and also provides a theoretical basis for the optimal design of sealing structure.
Studies in the electronic structure of matter
International Nuclear Information System (INIS)
Miller, D.L.
1979-01-01
KLL Auger transition rates for helium are computed using simple atomic orbital wavefunctions which take into account the difference in average electron--electron repulsion of initial and final states. The results are consistent with transition rates computed by other authors using a variety of many-electron techniques. It is suggested that wavefunctions determined in the manner described provide a useful representation of the autoionizing state within the first Bohr radius. A method for extracting atomic pseudopotentials from photoelectron angular distributions is described and applied photoionization of the outermost p shells of Ar, Kr, and Xe and to the 4d shell of Xe. The pseudopotentials obtained reproduce the data, and also predict accurate cross sections and phase shifts for photoelectron energies up to 100 eV. It is suggested that the pseudopotentials aptly mimic the effects of intrashell electron--electron correlations in the photoionization process. The extended Hueckel theory is applied to the nitrogen trap in GaAs and GaP. Perfect crystal band structures are computed and are shown to be in reasonable agreement with those computed with empirical pseudopotentials. Nitrogen impurity levels in GaAs and GaP are computed using an extended Hueckel cluster model. In each case the model predicts two states within the band gap, in contrast to experiment which detects one impurity state in GaP and none in GaAs. It is suggested that the choice of cluster used unrealistically concentrates states near the conduction band edge on the central atom
Studies in the electronic structure of matter
International Nuclear Information System (INIS)
Miller, D.L.
1979-01-01
KLL Auger transition rates for helium are computed using simple atomic orbital wavefunctions which take into account the difference in average electron-electron repulsion of initial and final states. The results are consistent with transition rates computed by other authors using a variety of many-electron techniques. It is suggested that wavefunctions determined in the manner described provide a useful representation of the autoionizing state within the first Bohr radius. A method for extracting atomic psuedopotentials from photoelectron angular distributions is described and applied photoionization of the outermost p shells of Ar, Kr, and Xe and to the 4d shell of Xe. The pseudopotentials obtained reproduce the data, and also predict accurate cross sections and phase shifts for photoelectron energies up to 100 eV. It is suggested that the pseudopotentials aptly mimic the effects of intrashell electron-electron correlations in the photoionization process. The extended Hueckel theory is applied to the nitrogen trap in GaAs and GaP. Perfect crystal band structures are computed and are shown to be in reasonable agreement with those computed with empirical psuedopotentials. Nitrogen impurity levles in GaAs and GaP are computed using an extended Hueckel cluster model. In each case the model predicts two states within the band gap, in contrast to experiment which detects one impurity state in GaP and none in GaAs. It is suggested that the choice of cluster used unrealistically concentrates states near the conduction band edge on the central atom
Electronic structure of defects in semiconductor heterojunctions
International Nuclear Information System (INIS)
Haussy, Bernard; Ganghoffer, Jean Francois
2002-01-01
Full text.heterojunctions and semiconductors and superlattices are well known and well used by people interested in optoelectronics communications. Components based on the use of heterojunctions are interesting for confinement of light and increase of quantum efficiency. An heterojunction is the contact zone between two different semiconductors, for example GaAs and Ga 1-x Al x As. Superlattices are a succession of heterojunctions (up to 10 or 20). These systems have been the subjects of many experiments ao analyse the contact between semiconductors. They also have been theoretically studied by different types of approach. The main result of those studies is the prediciton of band discontinuities. Defects in heterojunctions are real traps for charge carriers; they can affect the efficiency of the component decreasing the currents and the fluxes in it. the knowledge of their electronic structure is important, a great density of defects deeply modifies the electronic structure of the whole material creating real new bands of energy in the band structure of the component. in the first part of this work, we will describe the heterostructure and the defect in terms of quantum wells and discrete levels. This approach allows us to show the role of the width of the quantum well describing the structure but induces specific behaviours due to the one dimensional modelling. Then a perturbative treatment is proposed using the Green's functions formalism. We build atomic chains with different types of atoms featuring the heterostructure and the defect. Densities of states of a structure with a defect and levels associated to the defect are obtained. Results are comparable with the free electrons work, but the modelling do not induce problems due to a one dimensional approach. To extend our modelling, a three dimensions approach, based on a cavity model, is investigated. The influence of the defect, - of hydrogenoid type - introduced in the structure, is described by a cavity
International Nuclear Information System (INIS)
Khatibinia, Mohsen; Javad Fadaee, Mohammad; Salajegheh, Javad; Salajegheh, Eysa
2013-01-01
An efficient metamodeling framework in conjunction with the Monte-Carlo Simulation (MCS) is introduced to reduce the computational cost in seismic reliability assessment of existing RC structures. In order to achieve this purpose, the metamodel is designed by combining weighted least squares support vector machine (WLS-SVM) and a wavelet kernel function, called wavelet weighted least squares support vector machine (WWLS-SVM). In this study, the seismic reliability assessment of existing RC structures with consideration of soil–structure interaction (SSI) effects is investigated in accordance with Performance-Based Design (PBD). This study aims to incorporate the acceptable performance levels of PBD into reliability theory for comparing the obtained annual probability of non-performance with the target values for each performance level. The MCS method as the most reliable method is utilized to estimate the annual probability of failure associated with a given performance level in this study. In WWLS-SVM-based MCS, the structural seismic responses are accurately predicted by WWLS-SVM for reducing the computational cost. To show the efficiency and robustness of the proposed metamodel, two RC structures are studied. Numerical results demonstrate the efficiency and computational advantages of the proposed metamodel for the seismic reliability assessment of structures. Furthermore, the consideration of the SSI effects in the seismic reliability assessment of existing RC structures is compared to the fixed base model. It shows which SSI has the significant influence on the seismic reliability assessment of structures.
Atomic Reference Data for Electronic Structure Calculations
Kotochigova, S; Shirley, E L
We have generated data for atomic electronic structure calculations, to provide a standard reference for results of specified accuracy under commonly used approximations. Results are presented here for total energies and orbital energy eigenvalues for all atoms from H to U, at microHartree accuracy in the total energy, as computed in the local-density approximation (LDA) the local-spin-density approximation (LSD); the relativistic local-density approximation (RLDA); and scalar-relativistic local-density approximation (ScRLDA).
The electronic structure of impurities in semiconductors
Nylandsted larsen, A; Svane, A
2002-01-01
The electronic structure of isolated substitutional or interstitial impurities in group IV, IV-IV, and III-V compound semiconductors will be studied. Mössbauer spectroscopy will be used to investigate the incorporation of the implanted isotopes on the proper lattice sites. The data can be directly compared to theoretical calculations using the LMTO scheme. Deep level transient spectroscopy will be used to identify the band gap levels introduced by metallic impurities, mainly in Si~and~Si$ _{x}$Ge$_{1-x}$. \\\\ \\\\
Unoccupied surface electronic structure of Gd(0001)
International Nuclear Information System (INIS)
Li, D.; Dowben, P.A.; Ortega, J.E.; Himpsel, F.J.
1994-01-01
The unoccupied surface electronic structure of Gd(0001) was investigated with high-resolution inverse-photoemission spectroscopy. An empty surface state near E F is observed at bar Γ. Two other surface-sensitive features are also revealed at 1.2 and 3.1 eV above the Fermi level. Hydrogen adsorption on Gd surfaces was used to distinguish the surface-sensitive features from the bulk features. The unoccupied bulk-band critical points are determined to be Γ 3 + at 1.9 eV and A 1 at 0.8 eV
Cobalamins uncovered by modern electronic structure calculations
DEFF Research Database (Denmark)
Kepp, Kasper Planeta; Ryde, Ulf
2009-01-01
electronic-structure calculations, in particular density functional methods, the understanding of the molecular mechanism of cobalamins has changed dramatically, going from a dominating view of trans-steric strain effects to a much more complex view involving an arsenal of catalytic strategies. Among...... these are cis-steric distortions, electrostatic stabilization of radical products, the realization that nucleotide units can serve as polar handles, and the careful design of the active sites, with polar residues in the radical enzymes and non-polar residues in the transferases. Together, these strategies...
Electronic golden structure of the periodic chart
Energy Technology Data Exchange (ETDEWEB)
Malinowski, Leonard J. [Interdisciplinary Research Club, Monroeville, PA (United States)], E-mail: LJMalinowski@gmail.com
2009-11-15
The golden ratio has been studied since the ancient Greeks due to its inherent symmetry and aesthetic beauty, especially in the five Platonic Solids. The golden mean is now established as a pillar of El Naschie's E infinity where it achieves the physical manifestation of 0.618 034 MeV. The largest atomic electron orbital total energies average to the golden mean energy. This paper examines the golden ratio in order to expand upon a century old attempt to produce a relatively static, visual, geometric model of atomic structure.
Electronic golden structure of the periodic chart
International Nuclear Information System (INIS)
Malinowski, Leonard J.
2009-01-01
The golden ratio has been studied since the ancient Greeks due to its inherent symmetry and aesthetic beauty, especially in the five Platonic Solids. The golden mean is now established as a pillar of El Naschie's E infinity where it achieves the physical manifestation of 0.618 034 MeV. The largest atomic electron orbital total energies average to the golden mean energy. This paper examines the golden ratio in order to expand upon a century old attempt to produce a relatively static, visual, geometric model of atomic structure.
System reliability of concrete structures subjected to chloride ingress
DEFF Research Database (Denmark)
Leira, B.J.; Thöns, Sebastian
2017-01-01
attack on the entire bridge, a system model with 90 components is next introduced. This model is employed in order to perform reliability updating based on observations at a number of sites along the bridge. An Enhanced Monte Carlo simulation method (EMC) is applied for this purpose. It is shown...... that application of this simulation method reduces computation times significantly as compared to crude Monte Carlo methods....... are obtained based on measurements from the Gimsøystraumen bridge in Norway. These probability distributions are subsequently employed as input to a prediction model for chloride concentration at the steel reinforcement for a single but arbitrary position along the reinforcement. In order to address chloride...
Electronic structure of A15 compounds
International Nuclear Information System (INIS)
Pickett, W.E.
1980-01-01
For the past twenty-five years compounds with the A15 crystal structure have dominated the class of high temperature superconductors. The crystal structure of an A15 compound A 3 B is cubic (space group O/sub h/ 3 ). However, the site symmetry (D/sub 2d/) of the A atoms is much lower than cubic, an unusual occurrence in cubic binary compounds. Variations on this theme have supplied the basis of many theoretical models of the anomalous temperature (T) dependence of normal state properties and the low temperature cubic reversible tetragonal structural transformations which accompany high values of T/sub c/ in A15 compounds. In this paper results of self-consistent pseudopotential band structure calculations are used to assess some important aspects of the unique and unusual behavior in A15 compounds: (1) the role of the B atom in determining the overall electronic structure will be shown to be important; (2) the effect of the low site symmetry of the A atom on the charge density and potential will be assessed; and (3) the bonding will be shown to be metallic-covalent with no significant A-B charge transfer
A study in the reliability analysis method for nuclear power plant structures (I)
Energy Technology Data Exchange (ETDEWEB)
Oh, Byung Hwan; Choi, Seong Cheol; Shin, Ho Sang; Yang, In Hwan; Kim, Yi Sung; Yu, Young; Kim, Se Hun [Seoul, Nationl Univ., Seoul (Korea, Republic of)
1999-03-15
Nuclear power plant structures may be exposed to aggressive environmental effects that may cause their strength and stiffness to decrease over their service life. Although the physics of these damage mechanisms are reasonably well understood and quantitative evaluation of their effects on time-dependent structural behavior is possible in some instances, such evaluations are generally very difficult and remain novel. The assessment of existing steel containment in nuclear power plants for continued service must provide quantitative evidence that they are able to withstand future extreme loads during a service period with an acceptable level of reliability. Rational methodologies to perform the reliability assessment can be developed from mechanistic models of structural deterioration, using time-dependent structural reliability analysis to take loading and strength uncertainties into account. The final goal of this study is to develop the analysis method for the reliability of containment structures. The cause and mechanism of corrosion is first clarified and the reliability assessment method has been established. By introducing the equivalent normal distribution, the procedure of reliability analysis which can determine the failure probabilities has been established. The influence of design variables to reliability and the relation between the reliability and service life will be continued second year research.
DEFF Research Database (Denmark)
Vernica, Ionut; Wang, Huai; Blaabjerg, Frede
2018-01-01
Because of the high cost of failure, the reliability performance of power semiconductor devices is becoming a more and more important and stringent factor in many energy conversion applications. Thus, the need for appropriate reliability analysis of the power electronics emerges. Due to its...
Quantifiable and Reliable Structural Health Management Systems, Phase II
National Aeronautics and Space Administration — Under Project Constellation, NASA is developing a new generation of spacecraft for human spaceflight. A significant percentage of the structures used in these...
Reliability Evaluation and Probabilistic Design of Coastal Structures
DEFF Research Database (Denmark)
Burcharth, H. F.
1993-01-01
Conventional design practice for coastal structures is deterministic in nature and is based on the concept of a design load, which should not exceed the resistance (carrying capacity) of the structure. The design load is usually defined on a probabilistic basis as a characteristic value of the load......, e.g. the expectation (mean) value of the lOO-year return period event, however, often without consideration of the involved uncertainties. The resistance is in most cases defined in terms of the load which causes a certain design impact or damage to the structure and is not given as an ultimate...... force or deformation. This is because most of the available design formulae only give the relationship between wave characteristics and structural response, e.g. in terms of run-up, overtopping, armour layer damage etc. An example is the Hudson formula for armour layer stability. Almost all such design...
structural reliability of the nigerian grown abura timber bridge beam
African Journals Online (AJOL)
ENGR. J. I. AGUWA
2013-07-02
Jul 2, 2013 ... Structural analysis and deterministic design of a timber bridge beam using the Nigerian ... practice especially when it involves naturally occuring materials .... the beam due to distributed loads is; from [15]. (4). It is assumed that ...
Reliability assessment of aging structures subjected to gradual and shock deteriorations
International Nuclear Information System (INIS)
Wang, Cao; Zhang, Hao; Li, Quanwang
2017-01-01
Civil structures and infrastructure facilities are susceptible to deterioration posed by the effects of natural hazards and aggressive environmental conditions. These factors may increase the risk of service interruption of infrastructures, and should be taken into account when assessing the structural reliability during an infrastructure's service life. Modeling the resistance deterioration process reasonably is the basis for structural reliability analysis. In this paper, a novel model is developed for describing the deterioration of aging structures. The deterioration is a combination of two stochastic processes: the gradual deterioration posed by environmental effects and the shock deterioration caused by severe load attacks. The dependency of the deterioration magnitude on the load intensity is considered. The Gaussian copula function is employed to help construct the joint distribution of correlated random variables. Semi-analytical methods are developed to assess the structural failure time and the number of significant load events (shocks) to failure. Illustrative examples are presented to demonstrate the applicability of the proposed model in structural reliability analysis. Parametric studies are performed to investigate the role of deterioration-load correlation in structural reliability. - Highlights: • A new resistance deterioration model for aging structures is proposed. • Time-dependent reliability analysis methods incorporating the proposed deterioration model are developed. • Parametric studies are performed to investigate the role of deterioration-load correlation in structural reliability.
Blouin, Danielle; Day, Andrew G; Pavlov, Andrey
2011-12-01
Although never directly compared, structured interviews are reported as being more reliable than unstructured interviews. This study compared the reliability of both types of interview when applied to a common pool of applicants for positions in an emergency medicine residency program. In 2008, one structured interview was added to the two unstructured interviews traditionally used in our resident selection process. A formal job analysis using the critical incident technique guided the development of the structured interview tool. This tool consisted of 7 scenarios assessing 4 of the domains deemed essential for success as a resident in this program. The traditional interview tool assessed 5 general criteria. In addition to these criteria, the unstructured panel members were asked to rate each candidate on the same 4 essential domains rated by the structured panel members. All 3 panels interviewed all candidates. Main outcomes were the overall, interitem, and interrater reliabilities, the correlations between interview panels, and the dimensionality of each interview tool. Thirty candidates were interviewed. The overall reliability reached 0.43 for the structured interview, and 0.81 and 0.71 for the unstructured interviews. Analyses of the variance components showed a high interrater, low interitem reliability for the structured interview, and a high interrater, high interitem reliability for the unstructured interviews. The summary measures from the 2 unstructured interviews were significantly correlated, but neither was correlated with the structured interview. Only the structured interview was multidimensional. A structured interview did not yield a higher overall reliability than both unstructured interviews. The lower reliability is explained by a lower interitem reliability, which in turn is due to the multidimensionality of the interview tool. Both unstructured panels consistently rated a single dimension, even when prompted to assess the 4 specific domains
Ghaffarian, Reza; Evans, John W.
2014-01-01
For five decades, the semiconductor industry has distinguished itself by the rapid pace of improvement in miniaturization of electronics products-Moore's Law. Now, scaling hits a brick wall, a paradigm shift. The industry roadmaps recognized the scaling limitation and project that packaging technologies will meet further miniaturization needs or ak.a "More than Moore". This paper presents packaging technology trends and accelerated reliability testing methods currently being practiced. Then, it presents industry status on key advanced electronic packages, factors affecting accelerated solder joint reliability of area array packages, and IPC/JEDEC/Mil specifications for characterizations of assemblies under accelerated thermal and mechanical loading. Finally, it presents an examples demonstrating how Accelerated Testing and Analysis have been effectively employed in the development of complex spacecraft thereby reducing risk. Quantitative assessments necessarily involve the mathematics of probability and statistics. In addition, accelerated tests need to be designed which consider the desired risk posture and schedule for particular project. Such assessments relieve risks without imposing additional costs. and constraints that are not value added for a particular mission. Furthermore, in the course of development of complex systems, variances and defects will inevitably present themselves and require a decision concerning their disposition, necessitating quantitative assessments. In summary, this paper presents a comprehensive view point, from technology to systems, including the benefits and impact of accelerated testing in offsetting risk.
Electronic structure of hcp transition metals
DEFF Research Database (Denmark)
Jepsen, O.; Andersen, O. Krogh; Mackintosh, A. R.
1975-01-01
Using the linear muffin-tin-orbital method described in the previous paper, we have calculated the electronic structures of the hcp transition metals, Zr, Hf, Ru, and Os. We show how the band structures of these metals may be synthesized from the sp and d bands, and illustrate the effects...... of hybridization, relativistic band shifts, and spin-orbit coupling by the example of Os. By making use of parameters derived from the muffin-tin potential, we discuss trends in the positions and widths of the energy bands, especially the d bands, as a function of the location in the periodic table. The densities...... of states of the four metals are presented, and the calculated heat capacities compared with experiment. The Fermi surfaces of both Ru and Os are found to be in excellent quantitative agreement with de Haas-van Alphen measurements, indicating that the calculated d-band position is misplaced by less than 10...
Experimental Benchmarking of Pu Electronic Structure
International Nuclear Information System (INIS)
Tobin, J.G.; Moore, K.T.; Chung, B.W.; Wall, M.A.; Schwartz, A.J.; Ebbinghaus, B.B.; Butterfield, M.T.; Teslich, N.E. Jr.; Bliss, R.A.; Morton, S.A.; Yu, S.W.; Komesu, T.; Waddill, G.D.; van der Laan, G.; Kutepov, A.L.
2008-01-01
The standard method to determine the band structure of a condensed phase material is to (1) obtain a single crystal with a well defined surface and (2) map the bands with angle resolved photoelectron spectroscopy (occupied or valence bands) and inverse photoelectron spectroscopy (unoccupied or conduction bands). Unfortunately, in the case of Pu, the single crystals of Pu are either nonexistent, very small and/or having poorly defined surfaces. Furthermore, effects such as electron correlation and a large spin-orbit splitting in the 5f states have further complicated the situation. Thus, we have embarked upon the utilization of unorthodox electron spectroscopies, to circumvent the problems caused by the absence of large single crystals of Pu with well-defined surfaces. Our approach includes the techniques of resonant photoelectron spectroscopy, x-ray absorption spectroscopy, electron energy loss spectroscopy, Fano Effect measurements, and Bremstrahlung Isochromat Spectroscopy, including the utilization of micro-focused beams to probe single-crystallite regions of polycrystalline Pu samples.
Deep learning and the electronic structure problem
Mills, Kyle; Spanner, Michael; Tamblyn, Isaac
In the past decade, the fields of artificial intelligence and computer vision have progressed remarkably. Supported by the enthusiasm of large tech companies, as well as significant hardware advances and the utilization of graphical processing units to accelerate computations, deep neural networks (DNN) are gaining momentum as a robust choice for many diverse machine learning applications. We have demonstrated the ability of a DNN to solve a quantum mechanical eigenvalue equation directly, without the need to compute a wavefunction, and without knowledge of the underlying physics. We have trained a convolutional neural network to predict the total energy of an electron in a confining, 2-dimensional electrostatic potential. We numerically solved the one-electron Schrödinger equation for millions of electrostatic potentials, and used this as training data for our neural network. Four classes of potentials were assessed: the canonical cases of the harmonic oscillator and infinite well, and two types of randomly generated potentials for which no analytic solution is known. We compare the performance of the neural network and consider how these results could lead to future advances in electronic structure theory.
Further HTGR core support structure reliability studies. Interim report No. 1
International Nuclear Information System (INIS)
Platus, D.L.
1976-01-01
Results of a continuing effort to investigate high temperature gas cooled reactor (HTGR) core support structure reliability are described. Graphite material and core support structure component physical, mechanical and strength properties required for the reliability analysis are identified. Also described are experimental and associated analytical techniques for determining the required properties, a procedure for determining number of tests required, properties that might be monitored by special surveillance of the core support structure to improve reliability predictions, and recommendations for further studies. Emphasis in the study is directed towards developing a basic understanding of graphite failure and strength degradation mechanisms; and validating analytical methods for predicting strength and strength degradation from basic material properties
Reliability assessment of Indian Point Unit 3 containment structure under combined loads
International Nuclear Information System (INIS)
Hwang, H.; Shinozuka, M.; Kawakami, J.; Reich, M.
1984-01-01
In the current design criteria, the load combinations specified for design of concrete containment structures are in the deterministic format. However, by applying the probability-based reliability analysis method developed by BNL to the concrete containment structures designed according to the criteria, it is possible to evaluate the reliability levels implied in the current design criteria. For this purpose, the reliability analysis is applied to the Indian Point Unit No. 3 containment. The details of the containment structure such as the geometries and the rebar arrangements, etc., are taken from the working drawings and the Final Safety Analysis Report. Three kinds of loads are considered in the reliability analysis. They are, dead load, accidental pressure due to a large LOCA, and earthquake ground acceleration. This paper presents the reliability analysis results of the Indian Point Unit 3 containment subjected to all combinations of loads
DEFF Research Database (Denmark)
Vernica, Ionut; Wang, Huai; Blaabjerg, Frede
2018-01-01
conventional approach, mainly based on failure statistics from the field, the reliability evaluation of the power devices is still a challenging task. In order to address the given problem, a MATLAB based reliability assessment tool has been developed. The Design for Reliability and Robustness (DfR2) tool...... allows the user to easily investigate the reliability performance of the power electronic components (or sub-systems) under given input mission profiles and operating conditions. The main concept of the tool and its framework are introduced, highlighting the reliability assessment procedure for power...... semiconductor devices. Finally, a motor drive application is implemented and the reliability performance of the power devices is investigated with the help of the DfR2 tool, and the resulting reliability metrics are presented....
Analysis of complete logical structures in system reliability assessment
International Nuclear Information System (INIS)
Amendola, A.; Clarotti, C.A.; Contini, S.; Spizzichino, F.
1980-01-01
The application field of the fault-tree techniques has been explored in order to assess whether the AND-OR structures covered all possible actual binary systems. This resulted in the identification of various situations requiring the complete AND-OR-NOT structures for their analysis. We do not use the term non-coherent for such cases, since the monotonicity or not of a structure function is not a characteristic of a system, but of the particular top event being examined. The report presents different examples of complete fault-trees, which can be examined according to different degrees of approximation. In fact, the exact analysis for the determination of the smallest irredundant bases is very time consuming and actually necessary only in some particular cases (multi-state systems, incidental situations). Therefore, together with the exact procedure, the report shows two different methods of logical analysis that permit the reduction of complete fault-trees to AND-OR structures. Moreover, it discusses the problems concerning the evaluation of the probability distribution of the time to first top event occurrence, once the hypothesis of structure function monotonicity is removed
Structure and navigation for electronic publishing
Tillinghast, John; Beretta, Giordano B.
1998-01-01
The sudden explosion of the World Wide Web as a new publication medium has given a dramatic boost to the electronic publishing industry, which previously was a limited market centered around CD-ROMs and on-line databases. While the phenomenon has parallels to the advent of the tabloid press in the middle of last century, the electronic nature of the medium brings with it the typical characteristic of 4th wave media, namely the acceleration in its propagation speed and the volume of information. Consequently, e-publications are even flatter than print media; Shakespeare's Romeo and Juliet share the same computer screen with a home-made plagiarized copy of Deep Throat. The most touted tool for locating useful information on the World Wide Web is the search engine. However, due to the medium's flatness, sought information is drowned in a sea of useless information. A better solution is to build tools that allow authors to structure information so that it can easily be navigated. We experimented with the use of ontologies as a tool to formulate structures for information about a specific topic, so that related concepts are placed in adjacent locations and can easily be navigated using simple and ergonomic user models. We describe our effort in building a World Wide Web based photo album that is shared among a small network of people.
Electronic structure and superconductivity of fcc Cr
International Nuclear Information System (INIS)
Xu, J.; Freeman, A.J.; Jarlborg, T.; Brodsky, M.B.
1984-01-01
Results of self-consistent electronic structure calculations are reported for metastable fcc Cr metal. Unlike the case of bcc Cr which has E/sub F/ at a minimum in the density of states (DOS), the DOS at E/sub F/ in fcc Cr is at a peak making this one of the higher-DOS metals with the fcc structure (e.g., comparable with that of Ni and Pt). A calculated Stoner factor of 0.82 indicates that ferromagnetic ordering is not expected. Calculations of the electron-phonon coupling parameter lambda and superconducting transition temperature T/sub c/ were made using the rigid-ion approximation and strong-coupling theory with various estimates of the (unknown) phonon contribution. We conclude that T/sub c/'sroughly-equal2.5 K are reasonable, although they are substantially smaller than the T/sub c/roughly-equal10 K derived from measurements on Au-Cr-Au sandwiches
Design Protocols and Analytical Strategies that Incorporate Structural Reliability Models
Duffy, Stephen F.
1997-01-01
Al single crystal turbine blade material; map a simplistic failure strength envelope of the material; develop a statistically based reliability computer algorithm, verify the reliability model and computer algorithm, and model stator vanes for rig tests. Thus establishing design protocols that enable the engineer to analyze and predict the mechanical behavior of ceramic composites and intermetallics would mitigate the prototype (trial and error) approach currently used by the engineering community. The primary objective of the research effort supported by this short term grant is the continued creation of enabling technologies for the macroanalysis of components fabricated from ceramic composites and intermetallic material systems. The creation of enabling technologies aids in shortening the product development cycle of components fabricated from the new high technology materials.
A New Approach to Structural Reliability in Fatigue Failure
1998-03-01
6. AUTHOR(S) Dr. Sia Nemat-Nasser (PI) Dr. Joseph Zarka 7. PERFORMING ORGANIZATION NAMES(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION UniveBity of...their own problems. IV PUBLICATIONS Huang, J., J. Zarka and P. Navidi, "A New Approach in Relaibility of Welded Structures," Proceedings of the ASCE
Electronic structure of Ca, Sr, and Ba under pressure.
Animalu, A. O. E.; Heine, V.; Vasvari, B.
1967-01-01
Electronic band structure calculations phase of Ca, Sr and Ba over wide range of atomic volumes under pressure electronic band structure calculations for fcc phase of Ca, Sr and Ba over wide range of atomic volumes under pressure electronic band structure calculations for fcc phase of Ca, Sr and Ba over wide range of atomic volumes under pressure
A reliability analysis framework with Monte Carlo simulation for weld structure of crane's beam
Wang, Kefei; Xu, Hongwei; Qu, Fuzheng; Wang, Xin; Shi, Yanjun
2018-04-01
The reliability of the crane product in engineering is the core competitiveness of the product. This paper used Monte Carlo method analyzed the reliability of the weld metal structure of the bridge crane whose limit state function is mathematical expression. Then we obtained the minimum reliable welding feet height value for the welds between cover plate and web plate on main beam in different coefficients of variation. This paper provides a new idea and reference for the growth of the inherent reliability of crane.
Reliability of Structural Systems with regard to Permanent Displacements
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1991-01-01
approach - a differential equation approach - a superposition approach - the simple method These three approaches are described in Sørensen & Thoft-Christensen [5], Sørensen et al. [6] and Sørensen & Thoft-Christensen [7]. It is assumed that the structural system can be modelled by a multi-linear elastic......In this paper the problem of estimating the accumulated permanent displacements of an offshore platform during one storm is considered. For dynamically sensitive structural systems subjected to wave loads this problem is generally very difficult. However, for dynamic insensitive systems some...... methods/experience related to permanent deformations are described in Grinda et al. [1] and Papadrakakis & Loukakis [2]. For general dynamic systems modelled by one-degree-of-freedom (and two-degrees-of freedom) systems a number of methods exist, see e.g. Nielsen et al. [3] and Toro & Cornell [4]. However...
A Structural Reliability Business Process Modelling with System Dynamics Simulation
Lam, C. Y.; Chan, S. L.; Ip, W. H.
2010-01-01
Business activity flow analysis enables organizations to manage structured business processes, and can thus help them to improve performance. The six types of business activities identified here (i.e., SOA, SEA, MEA, SPA, MSA and FIA) are correlated and interact with one another, and the decisions from any business activity form feedback loops with previous and succeeding activities, thus allowing the business process to be modelled and simulated. For instance, for any company that is eager t...
Structural similarity image quality reliability: Determining parameters and window size
Silvestre-Blanes, Javier
2011-01-01
The need to obtain objective values of the quality of distorted images with respect to the original is fundamental in multimedia and image processing applications. It is generally required that this value correlates well with the human vision system (HVS). In spite of the properties and the general use of the mean square error (MSE) measurement, this has a poor correlation with HSV, which has led to the development of methods such as structural similarity (SSIM). This metric improves the corr...
Application of response surfaces for reliability analysis of marine structures
International Nuclear Information System (INIS)
Leira, Bernt J.; Holmas, Tore; Herfjord, Kjell
2005-01-01
Marine structures subjected to multiple environmental loads (i.e. waves, current, wind) are considered. These loads are characterized by a set of corresponding parameters. The structural fatigue damage and long-term response are expressed in terms of these environmental parameters based on application of polynomial response surfaces. For both types of analysis, an integration across the range of variation for all the environmental parameters is required. The location of the intervals which give rise to the dominant contribution for these integrals depends on the relative magnitude of the coefficients defining the polynomials. The required degree of numerical subdivision in order to obtain accurate results is also of interest. These issues are studied on a non-dimensional form. The loss of accuracy which results when applying response surfaces of too low order is also investigated. Response surfaces with cut-off limits at specific lower-bound values for the environmental parameters are further investigated. Having obtained general expressions on non-dimensional form, examples which correspond to specific response quantities for marine structures are considered. Typical values for the polynomial coefficients, and for the statistical distributions representing the environmental parameters, are applied. Convergence studies are subsequently performed for the particular example response quantities in order to make comparison with the general formulation. For the extreme response, the application of 'extreme contours' obtained from the statistical distributions of the environmental parameters is explored
Electronic structure of MnSi : The role of electron-electron interactions
Carbone, F; Zangrando, M; Brinkman, A; Nicolaou, A; Bondino, F; Magnano, E; Nugroho, A. A.; Parmigiani, F; Jarlborg, T; van der Marel, D
We present an experimental study of the electronic structure of MnSi. Using x-ray absorption spectroscopy (XAS), x-ray photoemission, and x-ray fluorescence, we provide experimental evidence that MnSi has a mixed valence ground state. We show that self-consistent local density approximation
Electronic structure of MnSi: The role of electron-electron interactions
Carbone, F.; Zangrando, M.; Brinkman, Alexander; Nicolaou, A.; Bondino, F.; Magnano, E.; Nugroho, A.A.; Parmigiani, F.; Jarlborg, Th.; van der Marel, D.
2006-01-01
We present an experimental study of the electronic structure of MnSi. Using x-ray absorption spectroscopy (XAS), x-ray photoemission, and x-ray fluorescence, we provide experimental evidence that MnSi has a mixed valence ground state. We show that self-consistent local density approximation
Fingerprint-based structure retrieval using electron density.
Yin, Shuangye; Dokholyan, Nikolay V
2011-03-01
We present a computational approach that can quickly search a large protein structural database to identify structures that fit a given electron density, such as determined by cryo-electron microscopy. We use geometric invariants (fingerprints) constructed using 3D Zernike moments to describe the electron density, and reduce the problem of fitting of the structure to the electron density to simple fingerprint comparison. Using this approach, we are able to screen the entire Protein Data Bank and identify structures that fit two experimental electron densities determined by cryo-electron microscopy. Copyright © 2010 Wiley-Liss, Inc.
Electromagnetic radiation of electrons in periodic structures
International Nuclear Information System (INIS)
Potylitsyn, Alexander Petrovich
2011-01-01
Periodic magnetic structures (undulators) are widely used in accelerators to generate monochromatic undulator radiation (UR) in the range from far infrared to the hard X-ray region. Another periodic crystalline structure is used to produce quasimonochromatic polarized photon beams via the coherent bremsstrahlung mechanism (CBS). Due to such characteristics as monochromaticity, polarization and adjustability, these types of radiation is of large interest for applied and basic research of accelerator-emitted radiation. The book provides a detailed overview of the fundamental principles behind electromagnetic radiation emitted from accelerated charged particles (e.g. UR, CBS, radiation of fast electrons in Laser flash fields) as well as a unified description of relatively new radiation mechanisms which attracted great interest in recent years. This are the so-called polarization radiation excited by the Coulomb field of incident particles in periodic structures, parametric X-rays, resonant transition radiation and the Smith-Purcell effect. Characteristics of such radiation sources and perspectives of their usage are discussed. The recent experimental results as well as their interpretation are presented. (orig.)
Temperature dependence of the electronic structure of semiconductors and insulators
Energy Technology Data Exchange (ETDEWEB)
Poncé, S., E-mail: samuel.pon@gmail.com; Gillet, Y.; Laflamme Janssen, J.; Gonze, X. [European Theoretical Spectroscopy Facility and Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des étoiles 8, bte L07.03.01, B-1348 Louvain-la-neuve (Belgium); Marini, A. [Consiglio Nazionale delle Ricerche (CNR), Via Salaria Km 29.3, CP 10, 00016 Monterotondo Stazione (Italy); Verstraete, M. [European Theoretical Spectroscopy Facility and Physique des matériaux et nanostructures, Université de Liège, Allée du 6 Août 17, B-4000 Liège (Belgium)
2015-09-14
The renormalization of electronic eigenenergies due to electron-phonon coupling (temperature dependence and zero-point motion effect) is sizable in many materials with light atoms. This effect, often neglected in ab initio calculations, can be computed using the perturbation-based Allen-Heine-Cardona theory in the adiabatic or non-adiabatic harmonic approximation. After a short description of the recent progresses in this field and a brief overview of the theory, we focus on the issue of phonon wavevector sampling convergence, until now poorly understood. Indeed, the renormalization is obtained numerically through a slowly converging q-point integration. For non-zero Born effective charges, we show that a divergence appears in the electron-phonon matrix elements at q → Γ, leading to a divergence of the adiabatic renormalization at band extrema. This problem is exacerbated by the slow convergence of Born effective charges with electronic wavevector sampling, which leaves residual Born effective charges in ab initio calculations on materials that are physically devoid of such charges. Here, we propose a solution that improves this convergence. However, for materials where Born effective charges are physically non-zero, the divergence of the renormalization indicates a breakdown of the adiabatic harmonic approximation, which we assess here by switching to the non-adiabatic harmonic approximation. Also, we study the convergence behavior of the renormalization and develop reliable extrapolation schemes to obtain the converged results. Finally, the adiabatic and non-adiabatic theories, with corrections for the slow Born effective charge convergence problem (and the associated divergence) are applied to the study of five semiconductors and insulators: α-AlN, β-AlN, BN, diamond, and silicon. For these five materials, we present the zero-point renormalization, temperature dependence, phonon-induced lifetime broadening, and the renormalized electronic band structure.
Reliability Assessment of a Bridge Structure Subjected to Chloride Attack
DEFF Research Database (Denmark)
Leira, Bernt J.; Thöns, Sebastian; Nielsen, Michael Havbro Faber
2018-01-01
Prediction of the service lifetime of concrete structures with respect to chloride ingress involves a number of parameters that are associated with large uncertainties. Hence, full-scale measurements are strongly in demand. This paper begins by summarizing statistical distributions based on measu......Prediction of the service lifetime of concrete structures with respect to chloride ingress involves a number of parameters that are associated with large uncertainties. Hence, full-scale measurements are strongly in demand. This paper begins by summarizing statistical distributions based...... on measurements taken from the Gimsøystraumen Bridge in Norway. A large number of chloride profiles are available based on concrete coring samples, and for each of these profiles the diffusion coefficient and surface concentration (due to sea spray) are estimated. Extensive measurements of the concrete cover...... depth are also performed. The probability distributions are input into a prediction model for chloride concentration at the steel reinforcement. By also introducing the critical chloride concentration as a random variable, the probability of exceeding the critical threshold is determined as a function...
Electron Liquids in Semiconductor Quantum Structures
International Nuclear Information System (INIS)
Pinczuk, Aron
2009-01-01
The groups led by Stormer and Pinczuk have focused this project on goals that seek the elucidation of novel many-particle effects that emerge in two-dimensional electron systems (2DES) as the result from fundamental quantum interactions. This experimental research is conducted under extreme conditions of temperature and magnetic field. From the materials point of view, the ultra-high mobility systems in GaAs/AlGaAs quantum structures continue to be at the forefront of this research. The newcomer materials are based on graphene, a single atomic layer of graphite. The graphene research is attracting enormous attention from many communities involved in condensed matter research. The investigated many-particle phenomena include the integer and fractional quantum Hall effect, composite fermions, and Dirac fermions, and a diverse group of electron solid and liquid crystal phases. The Stormer group performed magneto-transport experiments and far-infrared spectroscopy, while the Pinczuk group explores manifestations of such phases in optical spectra.
Electrons and photons in periodic structures
DEFF Research Database (Denmark)
Pedersen, Jesper Goor
. In particular, the modulation leads to the emergence of band gaps, which are accompanied by a strongly modified density of states near and within the band gap. The main focus is on two applications of such modified densities of states. Firstly, the intentional introduction of defects in an otherwise perfectly...... periodic modulation of an electron gas leads to the emergence of localized defect states with energies within the band gap, where no propagating modes exist. Secondly, the divergence of the photonic density of states near a photonic band gap leads to strongly modified light-matter interactions, which has...... of the density of states near the band gap edge. Using a perturbative approach, we demonstrate certain limits of the attainable slow down factors due to broadening of electromagnetic modes. We discuss the effect of damping due to a finite conductivity as well as structural disorder, and provide a common...
Electronic structure of single crystal C60
International Nuclear Information System (INIS)
Wu, J.; Shen, Z.X.; Dessau, D.S.; Cao, R.; Marshall, D.S.; Pianetta, P.; Lindau, I.; Yang, X.; Terry, J.; King, D.M.; Wells, B.O.; Elloway, D.; Wendt, H.R.; Brown, C.A.; Hunziker, H.; Vries, M.S. de
1992-01-01
We report angle-resolved photoemission data from single crystals of C 60 cleaved in UHV. Unlike the other forms of pure carbon, the valence band spectrum of C 60 consists of many sharp features that can be essentially accounted for by the quantum chemical calculations describing individual molecules. This suggests that the electronic structure of solid C 60 is mainly determined by the bonding interactions within the individual molecules. We also observe remarkable intensity modulations of the photoemission features as a function of photon energy, suggesting strong final state effects. Finally, we address the issue of the band width of the HOMO state of C 60 . We assert that the width of the photoemission peak of C 60 does not reflect the intrinsic band width because it is broadened by the non 0-0 transitions via the Franck-Condon principle. Our view point provides a possible reconciliation between these photoemission data and those measured by other techniques. (orig.)
Multilevel domain decomposition for electronic structure calculations
International Nuclear Information System (INIS)
Barrault, M.; Cances, E.; Hager, W.W.; Le Bris, C.
2007-01-01
We introduce a new multilevel domain decomposition method (MDD) for electronic structure calculations within semi-empirical and density functional theory (DFT) frameworks. This method iterates between local fine solvers and global coarse solvers, in the spirit of domain decomposition methods. Using this approach, calculations have been successfully performed on several linear polymer chains containing up to 40,000 atoms and 200,000 atomic orbitals. Both the computational cost and the memory requirement scale linearly with the number of atoms. Additional speed-up can easily be obtained by parallelization. We show that this domain decomposition method outperforms the density matrix minimization (DMM) method for poor initial guesses. Our method provides an efficient preconditioner for DMM and other linear scaling methods, variational in nature, such as the orbital minimization (OM) procedure
African Journals Online (AJOL)
eobe
Corresponding author, Tel: +234-703. RELIABILITY .... V , , given by the code of practice. However, checks must .... an optimization procedure over the failure domain F corresponding .... of Concrete Members based on Utility Theory,. Technical ...
Soil-structure interaction effects on the reliability evaluation of reactor containments
International Nuclear Information System (INIS)
Pires, J.; Hwang, H.; Reich, M.
1986-01-01
The probability-based method for the seismic reliability assessment of nuclear structures, which has been developed at Brookhaven National Laboratory (BNL), is extended to include the effects of soil-structure interaction. A reinforced concrete containment building is analyzed in order to examine soil-structure interaction effects on: (1) structural fragilities; (2) floor response spectra statistics; and (3) correlation coefficients for total acceleration responses at specified structural locations
Rakow, Glenn; Schnurr, Richard; Dailey, Christopher; Shakoorzadeh, Kamdin
2003-01-01
NASA's James Webb Space Telescope (JWST) faces difficult technical and budgetary challenges to overcome before it is scheduled launch in 2010. The Integrated Science Instrument Module (ISIM), shares these challenges. The major challenge addressed in this paper is the data network used to collect, process, compresses and store Infrared data. A total of 114 Mbps of raw information must be collected from 19 sources and delivered to the two redundant data processing units across a twenty meter deployed thermally restricted interface. Further data must be transferred to the solid-state recorder and the spacecraft. The JWST detectors are kept at cryogenic temperatures to obtain the sensitivity necessary to measure faint energy sources. The Focal Plane Electronics (FPE) that sample the detector, generate packets from the samples, and transmit these packets to the processing electronics must dissipate little power in order to help keep the detectors at these cold temperatures. Separating the low powered front-end electronics from the higher-powered processing electronics, and using a simple high-speed protocol to transmit the detector data minimize the power dissipation near the detectors. Low Voltage Differential Signaling (LVDS) drivers were considered an obvious choice for physical layer because of their high speed and low power. The mechanical restriction on the number cables across the thermal interface force the Image packets to be concentrated upon two high-speed links. These links connect the many image packet sources, Focal Plane Electronics (FPE), located near the cryogenic detectors to the processing electronics on the spacecraft structure. From 12 to 10,000 seconds of raw data are processed to make up an image, various algorithms integrate the pixel data Loss of commands to configure the detectors as well as the loss of science data itself may cause inefficiency in the use of the telescope that are unacceptable given the high cost of the observatory. This
Electronic Structure and Transport in Solids from First Principles
Mustafa, Jamal Ibrahim
The focus of this dissertation is the determination of the electronic structure and trans- port properties of solids. We first review some of the theory and computational methodology used in the calculation of electronic structure and materials properties. Throughout the dissertation, we make extensive use of state-of-the-art software packages that implement density functional theory, density functional perturbation theory, and the GW approximation, in addition to specialized methods for interpolating matrix elements for extremely accurate results. The first application of the computational framework introduced is the determination of band offsets in semiconductor heterojunctions using a theory of quantum dipoles at the interface. This method is applied to the case of heterojunction formed between a new metastable phase of silicon, with a rhombohedral structure, and cubic silicon. Next, we introduce a novel method for the construction of localized Wannier functions, which we have named the optimized projection functions method (OPFM). We illustrate the method on a variety of systems and find that it can reliably construct localized Wannier functions with minimal user intervention. We further develop the OPFM to investigate a class of materials called topological insulators, which are insulating in the bulk but have conductive surface states. These properties are a result of a nontrivial topology in their band structure, which has interesting effects on the character of the Wannier functions. In the last sections of the main text, the noble metals are studied in great detail, including their electronic properties and carrier dynamics. In particular, we investigate, the Fermi surface properties of the noble metals, specifically electron-phonon scattering lifetimes, and subsequently the transport properties determined by carriers on the Fermi surface. To achieve this, a novel sampling technique is developed, with wide applicability to transport calculations
Analysis methods for structure reliability of piping components
International Nuclear Information System (INIS)
Schimpfke, T.; Grebner, H.; Sievers, J.
2004-01-01
In the frame of the German reactor safety research program of the Federal Ministry of Economics and Labour (BMWA) GRS has started to develop an analysis code named PROST (PRObabilistic STructure analysis) for estimating the leak and break probabilities of piping systems in nuclear power plants. The long-term objective of this development is to provide failure probabilities of passive components for probabilistic safety analysis of nuclear power plants. Up to now the code can be used for calculating fatigue problems. The paper mentions the main capabilities and theoretical background of the present PROST development and presents some of the results of a benchmark analysis in the frame of the European project NURBIM (Nuclear Risk Based Inspection Methodologies for Passive Components). (orig.)
Juma, Mary Atieno; Zhang, Xuliang; He, Song Bai; Abusabah, Ahmed I. A.
2015-12-01
Recently, there has been a lot of research with electronic products because more and different functions are integrated into devices and the final product sizes have to be small to meet the market demand. A lot of research has been done on the (TSVs) Through Silicon Vias. In this paper, through silicon via liners are investigated. The liners: silicon dioxide, polystyrene and polypropylene carbonate are exposed to pressure on their inner surfaces and this yielded hoop stresses within their thickness. Deflections too occurred and this is a proof that deformation really took place. In one of our papers, hoop stresses for the same materials were investigated. The values were a little higher but different for each material used. In this paper, we use global cylindrical, partial cylinder model with different theta in Analysis system 14 to model the through silicon via liners. The values are lower meaning the reliability of the liners have been optimized and boosted. However, silicon dioxide liner had the lowest hoop stress around its circumference and lowest deflection value meaning that it's still one of the most reliable materials in the manufacture of through silicon via liners in the industry; but overdependence can be avoided if the other liners are used too.
Reliability of a structured interview for admission to an emergency medicine residency program.
Blouin, Danielle
2010-10-01
Interviews are most important in resident selection. Structured interviews are more reliable than unstructured ones. We sought to measure the interrater reliability of a newly designed structured interview during the selection process to an Emergency Medicine residency program. The critical incident technique was used to extract the desired dimensions of performance. The interview tool consisted of 7 clinical scenarios and 1 global rating. Three trained interviewers marked each candidate on all scenarios without discussing candidates' responses. Interitem consistency and estimates of variance were computed. Twenty-eight candidates were interviewed. The generalizability coefficient was 0.67. Removing the central tendency ratings increased the coefficient to 0.74. Coefficients of interitem consistency ranged from 0.64 to 0.74. The structured interview tool provided good although suboptimal interrater reliability. Increasing the number of scenarios improves reliability as does applying differential weights to the rating scale anchors. The latter would also facilitate the identification of those candidates with extreme ratings.
Carbon Electrode-Molecule Junctions: A Reliable Platform for Molecular Electronics.
Jia, Chuancheng; Ma, Bangjun; Xin, Na; Guo, Xuefeng
2015-09-15
The development of reliable approaches to integrate individual or a small collection of molecules into electrical nanocircuits, often termed "molecular electronics", is currently a research focus because it can not only overcome the increasing difficulties and fundamental limitations of miniaturization of current silicon-based electronic devices, but can also enable us to probe and understand the intrinsic properties of materials at the atomic- and/or molecular-length scale. This development might also lead to direct observation of novel effects and fundamental discovery of physical phenomena that are not accessible by traditional materials or approaches. Therefore, researchers from a variety of backgrounds have been devoting great effort to this objective, which has started to move beyond simple descriptions of charge transport and branch out in different directions, reflecting the interdisciplinarity. This Account exemplifies our ongoing interest and great effort in developing efficient lithographic methodologies capable of creating molecular electronic devices through the combination of top-down micro/nanofabrication with bottom-up molecular assembly. These devices use nanogapped carbon nanomaterials (such as single-walled carbon nanotubes (SWCNTs) and graphene), with a particular focus on graphene, as point contacts formed by electron beam lithography and precise oxygen plasma etching. Through robust amide linkages, functional molecular bridges terminated with diamine moieties are covalently wired into the carboxylic acid-functionalized nanogaps to form stable carbon electrode-molecule junctions with desired functionalities. At the macroscopic level, to improve the contact interface between electrodes and organic semiconductors and lower Schottky barriers, we used SWCNTs and graphene as efficient electrodes to explore the intrinsic properties of organic thin films, and then build functional high-performance organic nanotransistors with ultrahigh responsivities
Electronic structure of semiconductor quantum films
International Nuclear Information System (INIS)
Zhang, S.B.; Yeh, C.; Zunger, A.
1993-01-01
The electronic structure of thin (≤30 A) free-standing ideal films of Si(001), Si(110), and GaAs(110) is calculated using a plane-wave pseudopotential description. Unlike the expectation based on the simple effective-mass model, we find the following. (i) The band gaps of (001) quantum films exhibit even-odd oscillation as a function of the number N of monolayers. (ii) In addition to sine-type envelope functions which vanish at the film boundaries, some states have cosine envelope functions with extrema at boundaries. (iii) Even-layer Si(001) films exhibit at the valence-band maximum a state whose energy does not vary with the film thickness. Such zero confinement states have constant envelope throughout the film. (iv) Optical transitions in films exhibit boundary-imposed selection rules. Furthermore, oscillator strengths for pseudodirect transitions in the vicinity of forbidden direct transitions can be enhanced by several orders of magnitude. These findings, obtained in direct supercell calculations, can be explained in terms of a truncated crystal (TC) analysis. In this approach the film's wave functions are expanded in terms of pairs of bulk wave functions exhibiting a destructive interference at the boundaries. This maps the eigenvalue spectra of a film onto the bulk band structure evaluated at special k points which satisfy the boundary conditions. We find that the TC representation reproduces accurately the above-mentioned results of direct diagonalization of the film's Hamiltonian. This provides a simple alternative to the effective-mass model and relates the properties of quantum structures to those of the bulk material
Nonlinearity in structural and electronic materials
International Nuclear Information System (INIS)
Bishop, A.R.; Beardmore, K.M.; Ben-Naim, E.
1997-01-01
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project strengthens a nonlinear technology base relevant to a variety of problems arising in condensed matter and materials science, and applies this technology to those problems. In this way the controlled synthesis of, and experiments on, novel electronic and structural materials provide an important focus for nonlinear science, while nonlinear techniques help advance the understanding of the scientific principles underlying the control of microstructure and dynamics in complex materials. This research is primarily focused on four topics: (1) materials microstructure: growth and evolution, and porous media; (2) textures in elastic/martensitic materials; (3) electro- and photo-active polymers; and (4) ultrafast photophysics in complex electronic materials. Accomplishments included the following: organization of a ''Nonlinear Materials'' seminar series and international conferences including ''Fracture, Friction and Deformation,'' ''Nonequilibrium Phase Transitions,'' and ''Landscape Paradigms in Physics and Biology''; invited talks at international conference on ''Synthetic Metals,'' ''Quantum Phase Transitions,'' ''1996 CECAM Euroconference,'' and the 1995 Fall Meeting of the Materials Research Society; large-scale simulations and microscopic modeling of nonlinear coherent energy storage at crack tips and sliding interfaces; large-scale simulation and microscopic elasticity theory for precursor microstructure and dynamics at solid-solid diffusionless phase transformations; large-scale simulation of self-assembling organic thin films on inorganic substrates; analysis and simulation of smoothing of rough atomic surfaces; and modeling and analysis of flux pattern formation in equilibrium and nonequilibrium Josephson junction arrays and layered superconductors
The Seismic Reliability of Offshore Structures Based on Nonlinear Time History Analyses
International Nuclear Information System (INIS)
Hosseini, Mahmood; Karimiyani, Somayyeh; Ghafooripour, Amin; Jabbarzadeh, Mohammad Javad
2008-01-01
Regarding the past earthquakes damages to offshore structures, as vital structures in the oil and gas industries, it is important that their seismic design is performed by very high reliability. Accepting the Nonlinear Time History Analyses (NLTHA) as the most reliable seismic analysis method, in this paper an offshore platform of jacket type with the height of 304 feet, having a deck of 96 feet by 94 feet, and weighing 290 million pounds has been studied. At first, some Push-Over Analyses (POA) have been preformed to recognize the more critical members of the jacket, based on the range of their plastic deformations. Then NLTHA have been performed by using the 3-components accelerograms of 100 earthquakes, covering a wide range of frequency content, and normalized to three Peak Ground Acceleration (PGA) levels of 0.3 g, 0.65 g, and 1.0 g. By using the results of NLTHA the damage and rupture probabilities of critical member have been studied to assess the reliability of the jacket structure. Regarding that different structural members of the jacket have different effects on the stability of the platform, an ''importance factor'' has been considered for each critical member based on its location and orientation in the structure, and then the reliability of the whole structure has been obtained by combining the reliability of the critical members, each having its specific importance factor
LIF: A new Kriging based learning function and its application to structural reliability analysis
International Nuclear Information System (INIS)
Sun, Zhili; Wang, Jian; Li, Rui; Tong, Cao
2017-01-01
The main task of structural reliability analysis is to estimate failure probability of a studied structure taking randomness of input variables into account. To consider structural behavior practically, numerical models become more and more complicated and time-consuming, which increases the difficulty of reliability analysis. Therefore, sequential strategies of design of experiment (DoE) are raised. In this research, a new learning function, named least improvement function (LIF), is proposed to update DoE of Kriging based reliability analysis method. LIF values how much the accuracy of estimated failure probability will be improved if adding a given point into DoE. It takes both statistical information provided by the Kriging model and the joint probability density function of input variables into account, which is the most important difference from the existing learning functions. Maximum point of LIF is approximately determined with Markov Chain Monte Carlo(MCMC) simulation. A new reliability analysis method is developed based on the Kriging model, in which LIF, MCMC and Monte Carlo(MC) simulation are employed. Three examples are analyzed. Results show that LIF and the new method proposed in this research are very efficient when dealing with nonlinear performance function, small probability, complicated limit state and engineering problems with high dimension. - Highlights: • Least improvement function (LIF) is proposed for structural reliability analysis. • LIF takes both Kriging based statistical information and joint PDF into account. • A reliability analysis method is constructed based on Kriging, MCS and LIF.
Recent Advances in Optimal Design of Structures from a Reliability Point of View
DEFF Research Database (Denmark)
Thoft-Christensen, Palle; Sørensen, John Dalsgaard
1987-01-01
-Christensen and Baker[4] and Madsen et al.[5]. Next a heuristic method, the so-called ß-unzipping method[6] is mentioned. This method can be used to estimate the reliability of a structural system if some modelling assumptions are fulfilled. In the third section some elements of structural optimisation theory...... section. First, a short review of the reliability theory for structural elements (e.g., beams and tubular joints) based on the so-called ß-index philosophy (Cornell[1], Ditlevsen[2], and Hasofer and Lind[3]) is given. Detailed descriptions are given in textbooks such as those by Thoft...
Structural system reliability calculation using a probabilistic fault tree analysis method
Torng, T. Y.; Wu, Y.-T.; Millwater, H. R.
1992-01-01
The development of a new probabilistic fault tree analysis (PFTA) method for calculating structural system reliability is summarized. The proposed PFTA procedure includes: developing a fault tree to represent the complex structural system, constructing an approximation function for each bottom event, determining a dominant sampling sequence for all bottom events, and calculating the system reliability using an adaptive importance sampling method. PFTA is suitable for complicated structural problems that require computer-intensive computer calculations. A computer program has been developed to implement the PFTA.
International Nuclear Information System (INIS)
Stepanek, P.; Stastnik, S.; Salajka, V.; Hradil, P.; Skolar, J.; Chlanda, V.
2003-01-01
The contribution presents some aspects of the static reliability of concrete structures under temperature effects and under mechanical loading. The mathematical model of a load-bearing concrete structure was performed using the FEM method. The temperature field and static stress that generated states of stress were taken into account. A brief description of some aspects of evaluation of the reliability within the primary circuit concrete structures is stated. The knowledge of actual physical and mechanical characteristics and chemical composition of concrete were necessary for obtaining correct results of numerical analysis. (author)
International Nuclear Information System (INIS)
Lucia, A.C.
1984-01-01
The probability of failure of a structural component can be estimated by either statistical methods or a probabilistic structural reliability approach (where the failure is seen as a level crossing of a damage stochastic process which develops in space and in time). The probabilistic approach has the advantage that it makes available not only an absolute value of the failure probability but also a lot of additional information. The disadvantage of the probabilistic approach is its complexity. It is discussed for the following situations: reliability of a structural component, material properties, data for fatigue crack growth evaluation, a bench mark exercise on reactor pressure vessel failure probability computation, and non-destructive examination for assuring a given level of structural reliability. (U.K.)
Safety management of pipelines based on structural reliability: historical perspective and progress
Energy Technology Data Exchange (ETDEWEB)
Beck, Andre Teofilo; Bazan, Felipe Alexander Vargas [Universidade de Sao Paulo (USP), SP (Brazil); Mendes, Renato [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Donato, Guilherme [Petroleo Brasileiro S.A. (PETROBRAS/CENPES), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas e Desenvolvimento; Gardiner, Michael [GL Noble Denton, Loughborough (United Kingdom)
2012-07-01
Since the early beginnings in the sixties and seventies, Structural Reliability theory has reached a mature stage encompassing solid theoretical developments and increasing practical applications. Structural reliability methods have permeated the engineering profession, finding applications in code calibration, structural optimization, life extension of existing structures, life-cycle management of infrastructure risks and costs, and so on. This review paper shows that the ground work for Reliability Based Design and Assessment (RBDA) of onshore pipeline systems is already developed. Hence, this allows the economic management of the risks involved in operation of pipeline systems. It is shown that RBDA is a rational tool to safely manage the operational life of pipeline systems, optimizing initial design and the expenditures in inspection and maintenance operations. (author)
Some recent developments in the risk- and reliability analysis of structures
International Nuclear Information System (INIS)
Bauer, J.; Choi, H.S.; Kappler, H.; Melzer, H.J.; Panggabean, H.; Reichmann, K.H.; Schueller, G.I.; Schwarz, R.F.
1979-01-01
This report consists of six contributions divided into four general topics. While Part I concentrates on the development of Analytical Methods in Structural Reliability, Part II to IV are devoted to the application of these methods to Offshore-, Nuclear - and generally to Wind- and Earthquake Exposed Structures. (orig.) [de
Directory of Open Access Journals (Sweden)
Ertekin Öztekin Öztekin
2015-12-01
Full Text Available Design of the distance of bolts to each other and design of the distance of bolts to the edge of connection plates are made based on minimum and maximum boundary values proposed by structural codes. In this study, reliabilities of those distances were investigated. For this purpose, loading types, bolt types and plate thicknesses were taken as variable parameters. Monte Carlo Simulation (MCS method was used in the reliability computations performed for all combination of those parameters. At the end of study, all reliability index values for all those distances were presented in graphics and tables. Results obtained from this study compared with the values proposed by some structural codes and finally some evaluations were made about those comparisons. Finally, It was emphasized in the end of study that, it would be incorrect of the usage of the same bolt distances in the both traditional designs and the higher reliability level designs.
Electronic structure and phase equilibria in ternary substitutional alloys
International Nuclear Information System (INIS)
Traiber, A.J.S.; Allen, S.M.; Waterstrat, R.M.
1996-01-01
A reliable, consistent scheme to study phase equilibria in ternary substitutional alloys based on the tight-binding approximation is presented. With electronic parameters from linear muffin-tin orbital calculations, the computed density of states and band structures compare well with those from more accurate abinitio calculations. Disordered alloys are studied within the tight-binding coherent-potential approximation extended to alloys; energetics of ordered systems are obtained through effective pair interactions computed with the general perturbation method; and partially ordered alloys are studied with a novel simplification of the molecular coherent-potential approximation combined with the general perturbation method. The formalism is applied to bcc-based Zr-Ru-Pd alloys which are promising candidates for medical implant devices. Using energetics obtained from the above scheme, we apply the cluster- variation method to study phase equilibria for particular pseudo- binary alloys and show that results are consistent with observed behavior of electronic specific heat coefficient with composition for Zr 0.5 (Ru, Pd) 0.5
DEFF Research Database (Denmark)
Bech, B; Lönn, L; Falkenberg, M
2011-01-01
Objectives To study the construct validity and reliability of a novel endovascular global rating scale, Structured Assessment of endoVascular Expertise (SAVE). Design A Clinical, experimental study. Materials Twenty physicians with endovascular experiences ranging from complete novices to highly....... Validity was analysed by correlating experience with performance results. Reliability was analysed according to generalisability theory. Results The mean score on the 29 items of the SAVE scale correlated well with clinical experience (R = 0.84, P ... with clinical experience (R = -0.53, P validity and reliability of assessment with the SAVE scale was high when applied to performances in a simulation setting with advanced realism. No ceiling effect...
Optimised and balanced structural and system reliability of offshore wind turbines. An account
Energy Technology Data Exchange (ETDEWEB)
Tarp-Johansen, N.J.; Kozine, I. (Risoe National Lab., DTU, Roskilde, (DK)); Rademarkers, L. (Netherlands Energy Research Foundation (NL)); Dalsgaard Soerensen, J. (Aalborg Univ. (DK)) Ronold, K. (Det Norske Veritas (DK))
2005-04-15
This report gives the results of the research project 'Optimised and Uniform Safety and Reliability of Offshore Wind Turbines (an account)'. The main subject of the project has been the account of the state-of-the art of knowledge about, and/or attempts to, harmonisation of the structural reliability of wind turbines, on the one hand, and the reliability of the wind turbine's control/safety system, on the other hand. Within the project some research pointing ahead has also been conducted. (au)
Study of Fuze Structure and Reliability Design Based on the Direct Search Method
Lin, Zhang; Ning, Wang
2017-03-01
Redundant design is one of the important methods to improve the reliability of the system, but mutual coupling of multiple factors is often involved in the design. In my study, Direct Search Method is introduced into the optimum redundancy configuration for design optimization, in which, the reliability, cost, structural weight and other factors can be taken into account simultaneously, and the redundant allocation and reliability design of aircraft critical system are computed. The results show that this method is convenient and workable, and applicable to the redundancy configurations and optimization of various designs upon appropriate modifications. And this method has a good practical value.
The Role of Human Error in Design, Construction, and Reliability of Marine Structures.
1994-10-01
the fundamental reason for the disparities between computed or notional reliabilities and actuarial relia- bilities. Another important finding from...Marine Structures Lack of recognition of HOE is the fundamental reason for the disparities between computed or notional reliabilities and actuarial ...Conference on Offshore Mechanics and Arctic Engineering, ASME Paper No. OMAE-92-1372, Calgary, Alberta, Canada. Bea, R. G., et al. (1994). "Quality Assurance
Seismic reliability assessment methodology for CANDU concrete containment structures-phase 11
International Nuclear Information System (INIS)
Hong, H.P.
1996-07-01
This study was undertaken to verify a set of load factors for reliability-based seismic evaluation of CANDU containment structures in Eastern Canada. Here, the new, site-specific, results of probabilistic seismic hazard assessment (response spectral velocity) were applied. It was found that the previously recommended load factors are relatively insensitive to the new seismic hazard information, and are adequate for a reliability-based seismic evaluation process. (author). 4 refs., 5 tabs., 9 figs
Scale for positive aspects of caregiving experience: development, reliability, and factor structure.
Kate, N; Grover, S; Kulhara, P; Nehra, R
2012-06-01
OBJECTIVE. To develop an instrument (Scale for Positive Aspects of Caregiving Experience [SPACE]) that evaluates positive caregiving experience and assess its psychometric properties. METHODS. Available scales which assess some aspects of positive caregiving experience were reviewed and a 50-item questionnaire with a 5-point rating was constructed. In all, 203 primary caregivers of patients with severe mental disorders were asked to complete the questionnaire. Internal consistency, test-retest reliability, cross-language reliability, split-half reliability, and face validity were evaluated. Principal component factor analysis was run to assess the factorial validity of the scale. RESULTS. The scale developed as part of the study was found to have good internal consistency, test-retest reliability, cross-language reliability, split-half reliability, and face validity. Principal component factor analysis yielded a 4-factor structure, which also had good test-retest reliability and cross-language reliability. There was a strong correlation between the 4 factors obtained. CONCLUSION. The SPACE developed as part of this study has good psychometric properties.
Graph-based linear scaling electronic structure theory
Energy Technology Data Exchange (ETDEWEB)
Niklasson, Anders M. N., E-mail: amn@lanl.gov; Negre, Christian F. A.; Cawkwell, Marc J.; Swart, Pieter J.; Germann, Timothy C.; Bock, Nicolas [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Mniszewski, Susan M.; Mohd-Yusof, Jamal; Wall, Michael E.; Djidjev, Hristo [Computer, Computational, and Statistical Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Rubensson, Emanuel H. [Division of Scientific Computing, Department of Information Technology, Uppsala University, Box 337, SE-751 05 Uppsala (Sweden)
2016-06-21
We show how graph theory can be combined with quantum theory to calculate the electronic structure of large complex systems. The graph formalism is general and applicable to a broad range of electronic structure methods and materials, including challenging systems such as biomolecules. The methodology combines well-controlled accuracy, low computational cost, and natural low-communication parallelism. This combination addresses substantial shortcomings of linear scaling electronic structure theory, in particular with respect to quantum-based molecular dynamics simulations.
Directory of Open Access Journals (Sweden)
Shujuan Wang
2015-01-01
Full Text Available This paper investigates the structural design optimization to cover both the reliability and robustness under uncertainty in design variables. The main objective is to improve the efficiency of the optimization process. To address this problem, a hybrid reliability-based robust design optimization (RRDO method is proposed. Prior to the design optimization, the Sobol sensitivity analysis is used for selecting key design variables and providing response variance as well, resulting in significantly reduced computational complexity. The single-loop algorithm is employed to guarantee the structural reliability, allowing fast optimization process. In the case of robust design, the weighting factor balances the response performance and variance with respect to the uncertainty in design variables. The main contribution of this paper is that the proposed method applies the RRDO strategy with the usage of global approximation and the Sobol sensitivity analysis, leading to the reduced computational cost. A structural example is given to illustrate the performance of the proposed method.
Williams, Janet B W; Kobak, Kenneth A
2008-01-01
The Montgomery-Asberg Depression Rating Scale (MADRS) is often used in clinical trials to select patients and to assess treatment efficacy. The scale was originally published without suggested questions for clinicians to use in gathering the information necessary to rate the items. Structured and semi-structured interview guides have been found to improve reliability with other scales. To describe the development and test-retest reliability of a structured interview guide for the MADRS (SIGMA). A total of 162 test-retest interviews were conducted by 81 rater pairs. Each patient was interviewed twice, once by each rater conducting an independent interview. The intraclass correlation for total score between raters using the SIGMA was r=0.93, Preliability. Use of the SIGMA can result in high reliability of MADRS scores in evaluating patients with depression.
Cioclov, Dimitru Dragos
2013-01-01
Probabilistic methods for failure risk assessment are introduced, with reference to load carrying structures, such as pressure vessels (PV) and components of pipes systems. The definition of the failure risk associated with structural integrity is made in the context of the general approach to structural reliability. Sources of risk are summarily outlined with emphasis on variability and uncertainties (V&U) which might be encountered in the analysis. To highlight the problem, in its practical...
Electronic structure and chemical properties of superheavy elements
Energy Technology Data Exchange (ETDEWEB)
Pershina, V [Gesellschaft fuer Schwerionenforschung (GSI), Helmholtzzentrum fuer Schwerionenforschung Gmbh (Germany)
2009-12-31
Relativistic electronic structure calculations of superheavy elements (Z>=104) are analyzed. Preference is given to those related to experimental research. The role of relativistic effects is discussed.
On new cautious structural reliability models in the framework of imprecise probabilities
DEFF Research Database (Denmark)
Utkin, Lev; Kozine, Igor
2010-01-01
measures when the number of events of interest or observations is very small. The main feature of the models is that prior ignorance is not modelled by a fixed single prior distribution, but by a class of priors which is defined by upper and lower probabilities that can converge as statistical data......New imprecise structural reliability models are described in this paper. They are developed based on the imprecise Bayesian inference and are imprecise Dirichlet, imprecise negative binomial, gamma-exponential and normal models. The models are applied to computing cautious structural reliability...
Directory of Open Access Journals (Sweden)
Xing Jiang
2018-03-01
Full Text Available In recent years, the ultra-high voltage direct current (UHVDC transmission system has been developed rapidly for its significant long-distance, high-capacity and low-loss properties. Equipment failures and overall outages of the UHVDC system have increasingly vital influence on the power supply of the receiving end grid. To improve the reliability level of UHVDC systems, a quantitative selection and configuration approach of redundant structures is proposed in this paper, which is based on multi-state reliability equivalence. Specifically, considering the symmetry characteristic of an UHVDC system, a state space model is established as a monopole rather than a bipole, which effectively reduces the state space dimensions to be considered by deducing the reliability merging operator of two poles. Considering the standby effect of AC filters and the recovery effect of converter units, the number of available converter units and corresponding probability are expressed with in universal generating function (UGF form. Then, a sensitivity analysis is performed to quantify the impact of component reliability parameters on system reliability and determine the most specific devices that should be configured in the redundant structure. Finally, a cost-benefit analysis is utilized to help determine the optimal scheme of redundant devices. Case studies are conducted to demonstrate the effectiveness and accuracy of the proposed method. Based on the numerical results, configuring a set of redundant transformers is indicated to be of the greatest significance to improve the reliability level of UHVDC transmission systems.
Reliability-Based Calibration of Load Duration Factors for Timber Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Svensson, Staffan; Stang, Birgitte Friis Dela
2005-01-01
John Dalsgaard Sørensen, Staffan Svensson, Birgitte Dela Stang : Reliability-Based Calibration of Load Duration Factors for Timber Structures Abstract : The load bearing capacity of timber structures decrease with time depending on the type of load and timber. Based on representative limit...... states and stochastic models for timber structures, load duration factors are calibrated using probabilistic methods. Load duration e.ects are estimated on basis of simulation of realizations of wind, snow and imposed loads in accordance with the load models in the Danish structural codes. Three damage...... accumulation models are considered, namely Gerhards model, Barrett and Foschi _ s model and Foschi and Yao _ s model. The parameters in these models are .tted by the Maximum Likelihood Method using data relevant for Danish structural timber and the statistical uncertainty is quanti .ed. The reliability...
Electronic structure of shandite Co3Sn2S2
Dedkov, Y. S.; Holder, M.; Molodtsov, S. L.; Rosner, H.
2008-03-01
The electronic structure of shandite Co3Sn2S2 was determined by photoelectron spectroscopy and compared with ab initio band structure calculations. Presented results give evidence that this compound has half-metallic ferromagnetic properties.
Reliability of the Structured Clinical Interview for DSM-5 Sleep Disorders Module.
Taylor, Daniel J; Wilkerson, Allison K; Pruiksma, Kristi E; Williams, Jacob M; Ruggero, Camilo J; Hale, Willie; Mintz, Jim; Organek, Katherine Marczyk; Nicholson, Karin L; Litz, Brett T; Young-McCaughan, Stacey; Dondanville, Katherine A; Borah, Elisa V; Brundige, Antoinette; Peterson, Alan L
2018-03-15
To develop and demonstrate interrater reliability for a Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) Sleep Disorders (SCISD). The SCISD was designed to be a brief, reliable, and valid interview assessment of adult sleep disorders as defined by the DSM-5. A sample of 106 postdeployment active-duty military members seeking cognitive behavioral therapy for insomnia in a randomized clinical trial were assessed with the SCISD prior to treatment to determine eligibility. Audio recordings of these interviews were double-scored for interrater reliability. The interview is 8 pages long, includes 20 to 51 questions, and takes 10 to 20 minutes to administer. Of the nine major disorders included in the SCISD, six had prevalence rates high enough (ie, n ≥ 5) to include in analyses. Cohen kappa coefficient (κ) was used to assess interrater reliability for insomnia, hypersomnolence, obstructive sleep apnea hypopnea (OSAH), circadian rhythm sleep-wake, nightmare, and restless legs syndrome disorders. There was excellent interrater reliability for insomnia (1.0) and restless legs syndrome (0.83); very good reliability for nightmare disorder (0.78) and OSAH (0.73); and good reliability for hypersomnolence (0.50) and circadian rhythm sleep-wake disorders (0.50). The SCISD is a brief, structured clinical interview that is easy for clinicians to learn and use. The SCISD showed moderate to excellent interrater reliability for six of the major sleep disorders in the DSM-5 among active duty military seeking cognitive behavioral therapy for insomnia in a randomized clinical trial. Replication and extension studies are needed. Registry: ClinicalTrials.gov; Title: Comparing Internet and In-Person Brief Cognitive Behavioral Therapy of Insomnia; Identifier: NCT01549899; URL: https://clinicaltrials.gov/ct2/show/NCT01549899. © 2018 American Academy of Sleep Medicine.
Directory of Open Access Journals (Sweden)
Xingfa Yang
2018-01-01
Full Text Available Nondeterministic parameters of certain distribution are employed to model structural uncertainties, which are usually assumed as stochastic factors. However, model parameters may not be precisely represented due to some factors in engineering practices, such as lack of sufficient data, data with fuzziness, and unknown-but-bounded conditions. To this end, interval and fuzzy parameters are implemented and an efficient approach to structural reliability analysis with random-interval-fuzzy hybrid parameters is proposed in this study. Fuzzy parameters are first converted to equivalent random ones based on the equal entropy principle. 3σ criterion is then employed to transform the equivalent random and the original random parameters to interval variables. In doing this, the hybrid reliability problem is transformed into the one only with interval variables, in other words, nonprobabilistic reliability analysis problem. Nevertheless, the problem of interval extension existed in interval arithmetic, especially for the nonlinear systems. Therefore, universal grey mathematics, which can tackle the issue of interval extension, is employed to solve the nonprobabilistic reliability analysis problem. The results show that the proposed method can obtain more conservative results of the hybrid structural reliability.
Li, Haibin; He, Yun; Nie, Xiaobo
2018-01-01
Structural reliability analysis under uncertainty is paid wide attention by engineers and scholars due to reflecting the structural characteristics and the bearing actual situation. The direct integration method, started from the definition of reliability theory, is easy to be understood, but there are still mathematics difficulties in the calculation of multiple integrals. Therefore, a dual neural network method is proposed for calculating multiple integrals in this paper. Dual neural network consists of two neural networks. The neural network A is used to learn the integrand function, and the neural network B is used to simulate the original function. According to the derivative relationships between the network output and the network input, the neural network B is derived from the neural network A. On this basis, the performance function of normalization is employed in the proposed method to overcome the difficulty of multiple integrations and to improve the accuracy for reliability calculations. The comparisons between the proposed method and Monte Carlo simulation method, Hasofer-Lind method, the mean value first-order second moment method have demonstrated that the proposed method is an efficient and accurate reliability method for structural reliability problems.
Electronic conductance of quantum wire with serial periodic potential structures
International Nuclear Information System (INIS)
Fayad, Hisham M.; Shabat, Mohammed M.; Abdus Salam International Centre for Theoretical Physics, Trieste
2000-08-01
A theory based on the total transfer matrix is presented to investigate the electronic conductance in a quantum wire with serial periodic potentials. We apply the formalism in computation of the electronic conductance in a wire with different physical parameters of the wire structure. The numerical results could be used in designing some future quantum electronic devices. (author)
Structure of liquid alkali metals as electron-ion plasmas
International Nuclear Information System (INIS)
Chaturvedi, D.K.; Senatore, G.; Tosi, M.P.
1980-08-01
The static structure factor of liquid alkali metals near freezing, and its dependence on temperature and pressure, are evaluated in an electron-ion plasma model from an accurate theoretical determination of the structure factor of the one-component classical plasma and electron-screening theory. Very good agreement is obtained with the available experimental data. (author)
Reliability and Hierarchical Structure of DSM-5 Pathological Traits in a Danish Mixed Sample
DEFF Research Database (Denmark)
Bo, Sune; Bach, Bo; Mortensen, Erik Lykke
2016-01-01
In this study we assessed the DSM-5 trait model in a large Danish sample (n = 1,119) with respect to reliability of the applied Danish version of the Personality Inventory for DSM-5 (PID-5) self-report form by means of internal consistency and item discrimination. In addition, we tested whether...... the five-factor structure of the DSM-5 trait model can be replicated in a Danish independent sample using the PID-5 self-report form. Finally, we examined the hierarchical structure of DSM-5 traits. In terms of internal consistency and item discrimination, the applied PID-5 scales were generally found...... reliable and functional; our data resembled the five-factor structure of previous findings, and we identified a hierarchical structure from one to five factors that was conceptually reasonable and corresponded with existing findings. These results support the new DSM-5 trait model and suggest that it can...
Effect of soil–structure interaction on the reliability of reinforced concrete bridges
Directory of Open Access Journals (Sweden)
Kamel Bezih
2015-09-01
Full Text Available In the design of reinforced concrete (RC bridges, the random and nonlinear behavior of soil may lead to insufficient reliability levels. For this reason, it is necessary to take into account the variability of soil properties which can significantly affect the bridge behavior regarding ultimate and serviceability limit states. This study investigates the failure probability for existing reinforced concrete bridges due to the effects of interaction between the soil and the structure. In this paper, a coupled reliability–mechanical approach is developed to study the effect of soil–structure interaction for RC bridges. The modeling of this interaction is incorporated into the mechanical model of RC continuous beams, by considering nonlinear elastic soil stiffness. The reliability analysis highlights the large importance of soil–structure interaction and shows that the structural safety is highly sensitive to the variability of soil properties, especially when the nonlinear behavior of soil is considered.
DEFF Research Database (Denmark)
Hovgaard, Mads Knude; Hansen, Jannick Balleby; Brincker, Rune
2013-01-01
A scenario- and vibration based structural damage detection method is demonstrated though simulation. The method is Finite Element (FE) based. The value of the monitoring is calculated using structural reliability theory. A high cycle fatigue crack propagation model is assumed as the damage mecha......- and without monitoring. Monte Carlo Sampling (MCS) is used to estimate the probabilities and the tower of an onshore NREL 5MW wind turbine is given as a calculation case......A scenario- and vibration based structural damage detection method is demonstrated though simulation. The method is Finite Element (FE) based. The value of the monitoring is calculated using structural reliability theory. A high cycle fatigue crack propagation model is assumed as the damage...
Fan, Xiao-Ning; Zhi, Bo
2017-07-01
Uncertainties in parameters such as materials, loading, and geometry are inevitable in designing metallic structures for cranes. When considering these uncertainty factors, reliability-based design optimization (RBDO) offers a more reasonable design approach. However, existing RBDO methods for crane metallic structures are prone to low convergence speed and high computational cost. A unilevel RBDO method, combining a discrete imperialist competitive algorithm with an inverse reliability strategy based on the performance measure approach, is developed. Application of the imperialist competitive algorithm at the optimization level significantly improves the convergence speed of this RBDO method. At the reliability analysis level, the inverse reliability strategy is used to determine the feasibility of each probabilistic constraint at each design point by calculating its α-percentile performance, thereby avoiding convergence failure, calculation error, and disproportionate computational effort encountered using conventional moment and simulation methods. Application of the RBDO method to an actual crane structure shows that the developed RBDO realizes a design with the best tradeoff between economy and safety together with about one-third of the convergence speed and the computational cost of the existing method. This paper provides a scientific and effective design approach for the design of metallic structures of cranes.
Methodology for performing RF reliability experiments on a generic test structure
Sasse, G.T.; de Vries, Rein J.; Schmitz, Jurriaan
2007-01-01
This paper discusses a new technique developed for generating well defined RF large voltage swing signals for on wafer experiments. This technique can be employed for performing a broad range of different RF reliability experiments on one generic test structure. The frequency dependence of a
International Nuclear Information System (INIS)
Chevalier, M.J.; Smith, D.J.; Dean, D.W.
2012-01-01
Deterministic assessments are used to assess the integrity of structural systems operating at high temperature by providing a lower bound lifetime prediction, requiring considerable engineering judgement. However such a result may not satisfy the structural integrity assessment purpose if the results are overly conservative or conversely plant observations (such as failures) could undermine the assessment result if observed before the lower bound lifetime. This paper develops a reliability methodology for high temperature assessments and illustrates the impact and importance of managing the uncertainties within such an analysis. This is done by separating uncertainties into three classifications; aleatory uncertainty, quantifiable epistemic uncertainty and unquantifiable epistemic uncertainty. The result is a reliability model that can predict the behaviour of a structural system based upon plant observations, including failure and survival data. This can be used to reduce the over reliance upon engineering judgement which is prevalent in deterministic assessments. Highlights: ► Deterministic assessments are shown to be heavily reliant upon engineering judgment. ► Based upon the R5 procedure, a reliability model for a structural system is developed. ► Variables must be classified as either aleatory or epistemic to model their impact on reliability. ► Operation experience is then used to reduce reliance upon engineering judgment. ► This results in a model which can predict system behaviour and learn from operational experience.
The Study of Factor Structure and Reliability of an Abbreviated School Climate Survey
Ding, Cody; Liu, Ying; Berkowitz, Marvin
2011-01-01
The concept of school climate has been an important variable in research on quality of school life and student learning. One of the challenges in such a research effort is to develop instruments that could effectively and efficiently measure the construct. The purpose of the current study was to examine the factor structure and reliability of an…
DEFF Research Database (Denmark)
Ingwersen, Kim Gordon; Hjarbæk, John; Eshøj, Henrik
2016-01-01
Aim To evaluate the inter-rater reliability of measuring structural changes in the tendon of patients, clinically diagnosed with supraspinatus tendinopathy (cases) and healthy participants (controls), on ultrasound (US) images captured by standardised procedures. Methods A total of 40 participant...
Monte Carlo simulation - a powerful tool to support experimental activities in structure reliability
International Nuclear Information System (INIS)
Yuritzinn, T.; Chapuliot, S.; Eid, M.; Masson, R.; Dahl, A.; Moinereau, D.
2003-01-01
Monte-Carlo Simulation (MCS) can have different uses in supporting structure reliability investigations and assessments. In this paper we focus our interest on the use of MCS as a numerical tool to support the fitting of the experimental data related to toughness experiments. (authors)
Reliability and factor structure of the audit among male and female ...
African Journals Online (AJOL)
We assessed the reliability and dimensional structure of the Alcohol Use Disorders Identification Test (AUDIT) among bar patrons in a rural area of South Africa. In total, 406 bar patrons completed a questionnaire containing the AUDIT, and demographic and psychosocial measures. The participants consisted of 314 (77.3%) ...
Woodburn, Jim; Sutcliffe, Nick
1996-01-01
The Objective Structured Clinical Examination (OSCE), initially developed for undergraduate medical education, has been adapted for assessment of clinical skills in podiatry students. A 12-month pilot study found the test had relatively low levels of reliability, high construct and criterion validity, and good stability of performance over time.…
RESEARCH OF SYNERGETIC RELIABILITY OF PEARLITE-REDUCED STRUCTURAL STEEL 09G2FB
Directory of Open Access Journals (Sweden)
Gustov Yuriy Ivanovich
2012-10-01
Full Text Available The primary objective of the research is the synergetic reliability of perlite-reduced structural steel 09G2FB exposed to various thermal and mechanical treatments. In the aftermath of the above exposure, the steel in question has proved to assume a set of strength-related and plastic mechanical properties (σσδ and ψ.
Kingston, Greer B.; Rajabali Nejad, Mohammadreza; Gouldby, Ben P.; van Gelder, Pieter H.A.J.M.
2011-01-01
With the continual rise of sea levels and deterioration of flood defence structures over time, it is no longer appropriate to define a design level of flood protection, but rather, it is necessary to estimate the reliability of flood defences under varying and uncertain conditions. For complex
The Reliability and Structure of the Classroom Assessment Scoring System in German Pre-Schools
Stuck, Andrea; Kammermeyer, Gisela; Roux, Susanna
2016-01-01
This study examined the reliability and structure of the Classroom Assessment Scoring System (CLASS; Pianta, R. C., K. M. La Paro, and B. K. Hamre. 2008. "Classroom Assessment Scoring System. Manual Pre-K." Baltimore, MD: Brookes) and the quality of interactional processes in a German pre-school setting, drawing on a sample of 390…
Electronic structure of Mo and W investigated with positron annihilation
Energy Technology Data Exchange (ETDEWEB)
Dutschke, Markus [Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg (Germany); Sekania, Michael [Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg (Germany); Andronikashvili Institute of Physics, Tbilisi (Georgia); Benea, Diana [Faculty of Physics, Babes-Bolyai University, Cluj-Napoca (Romania); Department of Chemistry, Ludwig Maximilian University of Munich (Germany); Ceeh, Hubert; Weber, Joseph A.; Hugenschmidt, Christoph [FRM II, Technische Universitaet Muenchen, Garching (Germany); Chioncel, Liviu [Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg (Germany); Augsburg Center for Innovative Technologies, University of Augsburg (Germany)
2016-07-01
We perform electronic structure calculations to analyze the momentum distribution of the transition metals molybdenum and tungsten. We study the influence of positron-electron and the electron-electron interactions on the shape of the two-dimensional angular correlation of positron annihilation radiation (2D-ACAR) spectra. Our analysis is performed within the framework of the combined Density Functional (DFT) and Dynamical Mean-Field Theory (DMFT). Computed spectra are compared with recent experimental investigations.
International Nuclear Information System (INIS)
2005-06-01
As the 35th domestic symposium of Atomic Energy Research Committee, the Japan Welding Engineering Society, the symposium was held titled as Applications of structural reliability/risk assessment methods to nuclear energy'. Six speakers gave lectures titled as 'Structural reliability and risk assessment methods', 'Risk-informed regulation of US nuclear energy and role of probabilistic risk assessment', 'Reliability and risk assessment methods in chemical plants', 'Practical structural design methods based on reliability in architectural and civil areas', 'Maintenance activities based on reliability in thermal power plants' and 'LWR maintenance strategies based on Probabilistic Fracture Mechanics'. (T. Tanaka)
Electronic structures of elements according to ionization energies.
Zadeh, Dariush H
2017-11-28
The electronic structures of elements in the periodic table were analyzed using available experimental ionization energies. Two new parameters were defined to carry out the study. The first parameter-apparent nuclear charge (ANC)-quantified the overall charge of the nucleus and inner electrons observed by an outer electron during the ionization process. This parameter was utilized to define a second parameter, which presented the shielding ability of an electron against the nuclear charge. This second parameter-electron shielding effect (ESE)-provided an insight into the electronic structure of atoms. This article avoids any sort of approximation, interpolation or extrapolation. First experimental ionization energies were used to obtain the two aforementioned parameters. The second parameter (ESE) was then graphed against the electron number of each element, and was used to read the corresponding electronic structure. The ESE showed spikes/peaks at the end of each electronic shell, providing insight into when an electronic shell closes and a new one starts. The electronic structures of elements in the periodic table were mapped using this methodology. These graphs did not show complete agreement with the previously known "Aufbau" filling rule. A new filling rule was suggested based on the present observations. Finally, a new way to organize elements in the periodic table is suggested. Two earlier topics of effective nuclear charge, and shielding factor were also briefly discussed and compared numerically to demonstrate the capability of the new approach.
Correct Brillouin zone and electronic structure of BiPd
Yaresko, Alexander; Schnyder, Andreas P.; Benia, Hadj M.; Yim, Chi-Ming; Levy, Giorgio; Damascelli, Andrea; Ast, Christian R.; Peets, Darren C.; Wahl, Peter
2018-02-01
A promising route to the realization of Majorana fermions is in noncentrosymmetric superconductors, in which spin-orbit coupling lifts the spin degeneracy of both bulk and surface bands. A detailed assessment of the electronic structure is critical to evaluate their suitability for this through establishing the topological properties of the electronic structure. This requires correct identification of the time-reversal-invariant momenta. One such material is BiPd, a recently rediscovered noncentrosymmetric superconductor which can be grown in large, high-quality single crystals and has been studied by several groups using angular resolved photoemission to establish its surface electronic structure. Many of the published electronic structure studies on this material are based on a reciprocal unit cell which is not the actual Brillouin zone of the material. We show here the consequences of this for the electronic structures and show how the inferred topological nature of the material is affected.
Reliability prediction of large fuel cell stack based on structure stress analysis
Liu, L. F.; Liu, B.; Wu, C. W.
2017-09-01
The aim of this paper is to improve the reliability of Proton Electrolyte Membrane Fuel Cell (PEMFC) stack by designing the clamping force and the thickness difference between the membrane electrode assembly (MEA) and the gasket. The stack reliability is directly determined by the component reliability, which is affected by the material property and contact stress. The component contact stress is a random variable because it is usually affected by many uncertain factors in the production and clamping process. We have investigated the influences of parameter variation coefficient on the probability distribution of contact stress using the equivalent stiffness model and the first-order second moment method. The optimal contact stress to make the component stay in the highest level reliability is obtained by the stress-strength interference model. To obtain the optimal contact stress between the contact components, the optimal thickness of the component and the stack clamping force are optimally designed. Finally, a detailed description is given how to design the MEA and gasket dimensions to obtain the highest stack reliability. This work can provide a valuable guidance in the design of stack structure for a high reliability of fuel cell stack.
Karri, Naveen K.; Mo, Changki
2018-06-01
Structural reliability of thermoelectric generation (TEG) systems still remains an issue, especially for applications such as large-scale industrial or automobile exhaust heat recovery, in which TEG systems are subject to dynamic loads and thermal cycling. Traditional thermoelectric (TE) system design and optimization techniques, focused on performance alone, could result in designs that may fail during operation as the geometric requirements for optimal performance (especially the power) are often in conflict with the requirements for mechanical reliability. This study focused on reducing the thermomechanical stresses in a TEG system without compromising the optimized system performance. Finite element simulations were carried out to study the effect of TE element (leg) geometry such as leg length and cross-sectional shape under constrained material volume requirements. Results indicated that the element length has a major influence on the element stresses whereas regular cross-sectional shapes have minor influence. The impact of TE element stresses on the mechanical reliability is evaluated using brittle material failure theory based on Weibull analysis. An alternate couple configuration that relies on the industry practice of redundant element design is investigated. Results showed that the alternate configuration considerably reduced the TE element and metallization stresses, thereby enhancing the structural reliability, with little trade-off in the optimized performance. The proposed alternate configuration could serve as a potential design modification for improving the reliability of systems optimized for thermoelectric performance.
Electronic structure of hybrid interfaces for polymer-based electronics
International Nuclear Information System (INIS)
Fahlman, M; Crispin, A; Crispin, X; Henze, S K M; Jong, M P de; Osikowicz, W; Tengstedt, C; Salaneck, W R
2007-01-01
The fundamentals of the energy level alignment at anode and cathode electrodes in organic electronics are described. We focus on two different models that treat weakly interacting organic/metal (and organic/organic) interfaces: the induced density of interfacial states model and the so-called integer charge transfer model. The two models are compared and evaluated, mainly using photoelectron spectroscopy data of the energy level alignment of conjugated polymers and molecules at various organic/metal and organic/organic interfaces. We show that two different alignment regimes are generally observed: (i) vacuum level alignment, which corresponds to the lack of vacuum level offsets (Schottky-Mott limit) and hence the lack of charge transfer across the interface, and (ii) Fermi level pinning where the resulting work function of an organic/metal and organic/organic bilayer is independent of the substrate work function and an interface dipole is formed due to charge transfer across the interface. We argue that the experimental results are best described by the integer charge transfer model which predicts the vacuum level alignment when the substrate work function is above the positive charge transfer level and below the negative charge transfer level of the conjugated material. The model further predicts Fermi level pinning to the positive (negative) charge transfer level when the substrate work function is below (above) the positive (negative) charge transfer level. The nature of the integer charge transfer levels depend on the materials system: for conjugated large molecules and polymers, the integer charge transfer states are polarons or bipolarons; for small molecules' highest occupied and lowest unoccupied molecular orbitals and for crystalline systems, the relevant levels are the valence and conduction band edges. Finally, limits and further improvements to the integer charge transfer model are discussed as well as the impact on device design. (topical review)
An Intelligent Method for Structural Reliability Analysis Based on Response Surface
Institute of Scientific and Technical Information of China (English)
桂劲松; 刘红; 康海贵
2004-01-01
As water depth increases, the structural safety and reliability of a system become more and more important and challenging. Therefore, the structural reliability method must be applied in ocean engineering design such as offshore platform design. If the performance function is known in structural reliability analysis, the first-order second-moment method is often used. If the performance function could not be definitely expressed, the response surface method is always used because it has a very clear train of thought and simple programming. However, the traditional response surface method fits the response surface of quadratic polynomials where the problem of accuracy could not be solved, because the true limit state surface can be fitted well only in the area near the checking point. In this paper, an intelligent computing method based on the whole response surface is proposed, which can be used for the situation where the performance function could not be definitely expressed in structural reliability analysis. In this method, a response surface of the fuzzy neural network for the whole area should be constructed first, and then the structural reliability can be calculated by the genetic algorithm. In the proposed method, all the sample points for the training network come from the whole area, so the true limit state surface in the whole area can be fitted. Through calculational examples and comparative analysis, it can be known that the proposed method is much better than the traditional response surface method of quadratic polynomials, because, the amount of calculation of finite element analysis is largely reduced, the accuracy of calculation is improved,and the true limit state surface can be fitted very well in the whole area. So, the method proposed in this paper is suitable for engineering application.
The electronic structure of core states under extreme compressions
International Nuclear Information System (INIS)
Straub, G.K.
1992-01-01
At normal density and for modest compressions, the electronic structure of a metal can be accurately described by treating the conduction electrons and their interactions with the usual methods of band theory. The core electrons remain essentially the same as for an isolated free atom and do not participate in the bonding forces responsible for creating a condensed phase. As the density increases, the core electrons begin to ''see'' one another as the overlap of the tails of wave functions can no longer be neglected. The electronic structure of the core electrons is responsible for an effective repulsive interaction that eventually becomes free-electron-like at very high compressions. The electronic structure of the interacting core electrons may be treated in a simple manner using the Atomic Surface Method (ASM). The ASM is a first-principles treatment of the electronic structure involving a rigorous integration of the Schroedinger equation within the atomic-sphere approximation. Solid phase wave functions are constructed from isolated atom wave functions and the band width W l and the center of gravity of the band C l are obtained from simple formulas. The ASM can also utilize analytic forms of the atomic wave functions and thus provide direct functional dependence of various aspects of the electronic structure. Of particular use in understanding the behavior of the core electrons, the ASM provides the ability to analytically determine the density dependence of the band widths and positions. The process whereby core states interact with one another is best viewed as the formation of narrow electron bands formed from atomic states. As the core-core overlap increases, the bands increase in width and mean energy. In Sec.3 this picture is further developed and from the ASM one obtains the analytic dependence on density of the relative motion of the different bands. Also in Sec. 3 is a discussion of the transition to free electron bands
Push-pull alkenes: structure and p-electron distribution
Directory of Open Access Journals (Sweden)
ERICH KLEINPETER
2006-01-01
Full Text Available Push-pull alkenes are substituted alkenes with one or two electron-donating substituents on one end of C=C double bond and with one or two electron-accepting substituents at the other end. Allowance for p-electron delocalization leads to the central C=C double bond becoming ever more polarized and with rising push-pull character, the p-bond order of this double bond is reduced and, conversely, the corresponding p-bond orders of the C–Don and C–Acc bonds are accordingly increased. This push-pull effect is of decisive influence on both the dynamic behavior and the chemical reactivity of this class of compounds and thus it is of considerable interest to both determine and to quantify the inherent push-pull effect. Previously, the barriers to rotation about the C=C, C–Don and/or C–Acc partial double bonds (DG±, as determined by dynamic NMR spectroscopy or the 13C chemical shift difference of the polarized C=C partial double bond (DdC=C were employed for this purpose. However, these parameters can have serious limitations, viz. the barriers can be immeasurable on the NMR timescale (either by being too high or too low; heavily-biased conformers are present, etc. or DdC=C behaves in a non-additive manner with respect to the combination of the four substituents. Hence, a general parameter to quantify the push-pull effect is not yet available. Ab initio MO calculations on a collection of compounds, together with NBO analysis, provided valuable information on the structure, bond energies, electron occupancies and bonding/antibonding interactions. In addition to DG±C=C (either experimentally determined or theoretically calculated and DdC=C, the bond length of the C=C partial double bond was also examined and it proved to be a reliable parameter to quantify the push-pull effect. Equally so, the quotient of the occupation numbers of the antibonding andbonding p orbitals of the central C=C partial double bond ( p*C=C/ pC=C could also be employed for
Orbital Models and Electronic Structure Theory
DEFF Research Database (Denmark)
Linderberg, Jan
2012-01-01
This tribute to the work by Carl Johan Ballhausen focuses on the emergence of quantitative means for the study of the electronic properties of complexes and molecules. Development, refinement and application of the orbital picture elucidated electric and magnetic features of ranges of molecules...
Structural reliability analysis under evidence theory using the active learning kriging model
Yang, Xufeng; Liu, Yongshou; Ma, Panke
2017-11-01
Structural reliability analysis under evidence theory is investigated. It is rigorously proved that a surrogate model providing only correct sign prediction of the performance function can meet the accuracy requirement of evidence-theory-based reliability analysis. Accordingly, a method based on the active learning kriging model which only correctly predicts the sign of the performance function is proposed. Interval Monte Carlo simulation and a modified optimization method based on Karush-Kuhn-Tucker conditions are introduced to make the method more efficient in estimating the bounds of failure probability based on the kriging model. Four examples are investigated to demonstrate the efficiency and accuracy of the proposed method.
Crystal structure from one-electron theory
DEFF Research Database (Denmark)
Skriver, H. L.
1985-01-01
The authors have studied the crystal structure of all the 3d, 4d, and 5d transition metals at zero pressure and temperature by means of the linear muffin-tin orbital method and Andersen's force theorem. They find that, although the structural energy differences seem to be overestimated by the the......The authors have studied the crystal structure of all the 3d, 4d, and 5d transition metals at zero pressure and temperature by means of the linear muffin-tin orbital method and Andersen's force theorem. They find that, although the structural energy differences seem to be overestimated...
Design of a composite structure to achieve a specified reliability level
International Nuclear Information System (INIS)
Boyer, C.; Beakou, A.; Lemaire, M.
1997-01-01
Safety factors are widely used in structural design. For composite material structures, however, the lack of experimental feed-back does not allow the use of safety factors optimized from cost and reliability point of view. Reliability methods are one way to achieve the calibration of partial safety factors using a more rational method than judgement alone. First we present the calibration process. The reliability methods FORM, SORM, simulation, are initially applied to a laminate plate under uniform pressure. In this example, we compare three design criteria; the different reliability methods agree with the reference method for all criteria used. We chose the Tsai-Hill criteria and the FORM method to calculate safety factors. Then, a calibration process is undertaken on a composite pipe and this serves to illustrate the different steps in the calculation. Finally, we present a calibration of a general plate structure. The partial safety factors and their sensitivities to the different parameters of the stochastic variables are given according to load type
LDA+U and tight-binding electronic structure of InN nanowires
Molina-Sánchez, A.; García-Cristóbal, A.; Cantarero, A.; Terentjevs, A.; Cicero, G.
2010-10-01
In this paper we employ a combined ab initio and tight-binding approach to obtain the electronic and optical properties of hydrogenated Indium nitride (InN) nanowires. We first discuss InN band structure for the wurtzite structure calculated at the LDA+U level and use this information to extract the parameters needed for an empirical tight-binging implementation. These parameters are then employed to calculate the electronic and optical properties of InN nanowires in a diameter range that would not be affordable by ab initio techniques. The reliability of the large nanowires results is assessed by explicitly comparing the electronic structure of a small diameter wire studied both at LDA+U and tight-binding level.
Reliability Analysis and Test Planning using CAPO-Test for Existing Structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Engelund, S.; Faber, Michael Havbro
2000-01-01
Evaluation of the reliability of existing concrete structures often requires that the compressive strength of the concrete is estimated on the basis of tests performed with concrete samples from the structure considered. In this paper the CAPO-test method is considered. The different sources...... of uncertainty related to this method are described. It is shown how the uncertainty in the transformation from the CAPO-test results to estimates of the concrete strength can be modeled. Further, the statistical uncertainty is modeled using Bayesian statistics. Finally, it is shown how reliability-based optimal...... planning of CAPO-tests can be performed taking into account the expected costs due to the CAPO-tests and possible repair or failure of the structure considered. An illustrative example is presented where the CAPO-test is compared with conventional concrete cylinder compression tests performed on cores...
Reliability analysis based on a novel density estimation method for structures with correlations
Directory of Open Access Journals (Sweden)
Baoyu LI
2017-06-01
Full Text Available Estimating the Probability Density Function (PDF of the performance function is a direct way for structural reliability analysis, and the failure probability can be easily obtained by integration in the failure domain. However, efficiently estimating the PDF is still an urgent problem to be solved. The existing fractional moment based maximum entropy has provided a very advanced method for the PDF estimation, whereas the main shortcoming is that it limits the application of the reliability analysis method only to structures with independent inputs. While in fact, structures with correlated inputs always exist in engineering, thus this paper improves the maximum entropy method, and applies the Unscented Transformation (UT technique to compute the fractional moments of the performance function for structures with correlations, which is a very efficient moment estimation method for models with any inputs. The proposed method can precisely estimate the probability distributions of performance functions for structures with correlations. Besides, the number of function evaluations of the proposed method in reliability analysis, which is determined by UT, is really small. Several examples are employed to illustrate the accuracy and advantages of the proposed method.
International Nuclear Information System (INIS)
Procaccia, H.; Morilhat, P.; Carle, R.; Menjon, G.
1996-01-01
The management of the service life of mechanical materials implies an evaluation of their risk of failure during their use. To evaluate this risk the following methods are used: the classical frequency statistics applied to experience feedback data concerning failures noticed during operation of active parts (pumps, valves, exchangers, circuit breakers etc..); the Bayesian approach in the case of scarce statistical data and when experts are needed to compensate the lack of information; the structures reliability approach when no data are available and when a theoretical model of degradation must be used, in particular for passive structures (pressure vessels, pipes, tanks, etc..). The aim of this book is to describe the principles and applications of this third approach to industrial installations. Chapter 1 recalls the historical aspects of the probabilistic approach to the reliability of structures and the existing codes. Chapter 2 presents the level 1 deterministic method applied so far for the conceiving of passive structures. The Cornell reliability index, already used in civil engineering codes, is defined in chapter 3. The Hasofer and Lind reliability index, a generalization of the Cornell index, is defined in chapter 4. Chapter 5 concerns the application of probabilistic approaches to optimization studies with the introduction of the economical variables linked to the risk and the possible actions to limit this risk (in-service inspection, maintenance, repairing etc..). Chapters 6 and 7 describe the Monte Carlo simulation and approximation methods for failure probabilistic calculations, and recall the fracture mechanics basis and the models of load and degradation of industrial installations. Some applications are given in chapter 9 with the cases of the safety margins quantization of a fissured pipe and the optimizing of the in-service inspection policy of a steam generator. Chapter 10 raises the problem of the coupling between mechanical and reliability
Complex band structure and electronic transmission eigenchannels
DEFF Research Database (Denmark)
Jensen, Anders; Strange, Mikkel; Smidstrup, Soren
2017-01-01
and complex band structure, in this case individual eigenchannel transmissions and different complex bands. We present calculations of decay constants for the two most conductive states as determined by complex band structure and standard DFT Landauer transport calculations for one semi-conductor and two...
Syntheses and electronic structures of decamethylmetallocenes
International Nuclear Information System (INIS)
Robbins, J.L.
1981-04-01
The synthesis of decamethylmanganocene [(eta-C 5 (CH 3 ) 5 ) 2 Mn or (Me 5 Cp) 2 Mn)] is described. Magnetic susceptibility and electron paramagnetic resonance (EPR) studies show that (Me 5 Cp) 2 Mn is a low-spin, 17-electron compound with an orbitally degenerate, 2 E/sub 2g/ [e/sub 2g/ 3 a/sub 1g/ 2 ] ground state. An x-ray crystallographic study of (Me 5 Cp) 2 Mn shows that it is a monomeric, D/sub 5d/ decamethylmetallocene with metal to ring carbon distances that are about 0.3 A shorter than those determined for high-spin manganocenes. The syntheses of new (Me 5 Cp) 2 M (M = Mg,V,Cr,Co, and Ni) and [(Me 5 Cp) 2 M]PF 6 (M = Cr,Co, and Ni) compounds are described. In addition, a preparative route to a novel, dicationic decamethylmetallocene, [(Me 5 Cp) 2 Ni](PF 6 ) 2 is reported. Infrared, nuclear magnetic resonance, magnetic susceptibility, and/or x-ray crystallographic studies indicate that all the above compounds are D/sub 5d/ or D/sub 5h/ decamethylmetallocenes with low-spin electronic configurations. Cyclic voltammetry studies verify the reversibility and the one-electron nature of the (Me 5 Cp) 2 M → [(Me 5 Cp) 2 M] + (M = Cr,Mn,Fe,Co,Ni), [(Me 5 Cp) 2 Mn] - → (Me 5 Cp) 2 Mn and [(Me 5 Cp) 2 Ni] + → [Me 5 Cp) 2 Ni] 2+ redox reactions. These studies reveal that the neutral decamethylmetallocenes are much more easily oxidized than their metallocene counterparts. This result attests to the electron-donating properties of the ten substituent methyl groups. Proton and carbon-13 NMR data are reported for the diamagnetic Mg(II), Mn(I), Fe(II), Co(III), and Ni(IV) decamethylmetallocenes and for [(Me 5 Cp) 2 V(CO) 2 ] + . The uv-visible absorption spectra of the 15-, 18- and 20- electron decamethylmetallocenes are also reported
Syntheses and electronic structures of decamethylmetallocenes
Energy Technology Data Exchange (ETDEWEB)
Robbins, J.L.
1981-04-01
The synthesis of decamethylmanganocene ((eta-C/sub 5/(CH/sub 3/)/sub 5/)/sub 2/Mn or (Me/sub 5/Cp)/sub 2/Mn)) is described. Magnetic susceptibility and electron paramagnetic resonance (EPR) studies show that (Me/sub 5/Cp)/sub 2/Mn is a low-spin, 17-electron compound with an orbitally degenerate, /sup 2/E/sub 2g/ (e/sub 2g//sup 3/ a/sub 1g//sup 2/) ground state. An x-ray crystallographic study of (Me/sub 5/Cp)/sub 2/Mn shows that it is a monomeric, D/sub 5d/ decamethylmetallocene with metal to ring carbon distances that are about 0.3 A shorter than those determined for high-spin manganocenes. The syntheses of new (Me/sub 5/Cp)/sub 2/M (M = Mg,V,Cr,Co, and Ni) and ((Me/sub 5/Cp)/sub 2/M)PF/sub 6/ (M = Cr,Co, and Ni) compounds are described. In addition, a preparative route to a novel, dicationic decamethylmetallocene, ((Me/sub 5/Cp)/sub 2/Ni)(PF/sub 6/)/sub 2/ is reported. Infrared, nuclear magnetic resonance, magnetic susceptibility, and/or x-ray crystallographic studies indicate that all the above compounds are D/sub 5d/ or D/sub 5h/ decamethylmetallocenes with low-spin electronic configurations. Cyclic voltammetry studies verify the reversibility and the one-electron nature of the (Me/sub 5/Cp)/sub 2/M ..-->.. ((Me/sub 5/Cp)/sub 2/M)/sup +/ (M = Cr,Mn,Fe,Co,Ni), ((Me/sub 5/Cp)/sub 2/Mn)/sup -/ ..-->.. (Me/sub 5/Cp)/sub 2/Mn and ((Me/sub 5/Cp)/sub 2/Ni)/sup +/ ..-->.. (Me/sub 5/Cp)/sub 2/Ni)/sup 2 +/ redox reactions. These studies reveal that the neutral decamethylmetallocenes are much more easily oxidized than their metallocene counterparts. This result attests to the electron-donating properties of the ten substituent methyl groups. Proton and carbon-13 NMR data are reported for the diamagnetic Mg(II), Mn(I), Fe(II), Co(III), and Ni(IV) decamethylmetallocenes and for ((Me/sub 5/Cp)/sub 2/V(CO)/sub 2/)/sup +/. The uv-visible absorption spectra of the 15-, 18- and 20- electron decamethylmetallocenes are also reported.
Electronic structure and optical properties of solid C60
International Nuclear Information System (INIS)
Mattesini, M.; Ahuja, R.; Sa, L.; Hugosson, H.W.; Johansson, B.; Eriksson, O.
2009-01-01
The electronic structure and the optical properties of face-centered-cubic C 60 have been investigated by using an all-electron full-potential method. Our ab initio results show that the imaginary dielectric function for high-energy values looks very similar to that of graphite, revealing close electronic structure similarities between the two systems. We have also identified the origin of different peaks in the dielectric function of fullerene by means of the calculated electronic density of states. The computed optical spectrum compares fairly well with the available experimental data for the Vis-UV absorption spectrum of solid C 60 .
Electronic structure of fractionally nuclear charged atoms
International Nuclear Information System (INIS)
Pavao, Antonio C.; Bastos, Cristiano C.; Ferreira, Joacy V.
2008-01-01
Different properties of quark chemistry are studied by performing accurate ab initio Hartree- Fock calculations on fractionally nuclear charged atoms. Ground and first excited states of sodium atoms with quarks attached to the nucleus are obtained using CI calculations. It is suggested that the sodium 2 P -> 2 S electronic transition can be used as a guide in searching for unconfined quarks. Also, the variation of the binding electronic energy with nuclear charge in the isoelectronic series of fractionally nuclear charged atoms A ±2/3 and A ±1/3 (A = H, Li, Na, P and Ca) is analyzed. The present calculations suggest that unconfined colored particles have large appetite for heavy nuclei and that quark-antiquark pairs could be stabilized in presence of the atomic matter. (author)
Tailoring electronic structure of polyazomethines thin films
J. Weszka; B. Hajduk; M. Domański; M. Chwastek; J. Jurusik; B. Jarząbek; H. Bednarski; P. Jarka
2010-01-01
Purpose: The aim of this work is to show how electronic properties of polyazomethine thin films deposited by chemical vapor deposition method (CVD) can be tailored by manipulating technological parameters of pristine films preparation as well as modifying them while the as-prepared films put into iodine atmosphere.Design/methodology/approach: The recent achievements in the field of designing and preparation methods to be used while preparing polymer photovoltaic solar cells or optoelectronic ...
Edwards, L.; Santisteban, J. R.
The determination of accurate reliable residual stresses is critical to many fields of structural integrity. Neutron stress measurement is a non-destructive technique that uniquely provides insights into stress fields deep within engineering components and structures. As such, it has become an increasingly important tool within engineering, leading to improved manufacturing processes to reduce stress and distortion as well as to the definition of more precise lifing procedures. This paper describes the likely impact of the next generation of dedicated engineering stress diffractometers currently being constructed and the utility of the technique using examples of residual stresses both beneficial and detrimental to structural integrity.
Reliability of multi-model and structurally different single-model ensembles
Energy Technology Data Exchange (ETDEWEB)
Yokohata, Tokuta [National Institute for Environmental Studies, Center for Global Environmental Research, Tsukuba, Ibaraki (Japan); Annan, James D.; Hargreaves, Julia C. [Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Yokohama, Kanagawa (Japan); Collins, Matthew [University of Exeter, College of Engineering, Mathematics and Physical Sciences, Exeter (United Kingdom); Jackson, Charles S.; Tobis, Michael [The University of Texas at Austin, Institute of Geophysics, 10100 Burnet Rd., ROC-196, Mail Code R2200, Austin, TX (United States); Webb, Mark J. [Met Office Hadley Centre, Exeter (United Kingdom)
2012-08-15
The performance of several state-of-the-art climate model ensembles, including two multi-model ensembles (MMEs) and four structurally different (perturbed parameter) single model ensembles (SMEs), are investigated for the first time using the rank histogram approach. In this method, the reliability of a model ensemble is evaluated from the point of view of whether the observations can be regarded as being sampled from the ensemble. Our analysis reveals that, in the MMEs, the climate variables we investigated are broadly reliable on the global scale, with a tendency towards overdispersion. On the other hand, in the SMEs, the reliability differs depending on the ensemble and variable field considered. In general, the mean state and historical trend of surface air temperature, and mean state of precipitation are reliable in the SMEs. However, variables such as sea level pressure or top-of-atmosphere clear-sky shortwave radiation do not cover a sufficiently wide range in some. It is not possible to assess whether this is a fundamental feature of SMEs generated with particular model, or a consequence of the algorithm used to select and perturb the values of the parameters. As under-dispersion is a potentially more serious issue when using ensembles to make projections, we recommend the application of rank histograms to assess reliability when designing and running perturbed physics SMEs. (orig.)
Electronic structure and formation energy of a vacancy in aluminum
International Nuclear Information System (INIS)
Chakraborty, B.; Siegel, R.W.
1981-11-01
The electronic structure of a vacancy in Al was calculated self-consistently using norm-conserving ionic pseudopotentials obtained from ab initio atomic calculations. A 27-atom-site supercell containing 1 vacancy and 26 atoms was used to simulate the environment of the vacancy. A vacancy formation energy of 1.5 eV was also calculated (cf. the experimental value of 0.66 eV). The effects of the supercell and the nature of the ionic potential on the resulting electronic structure and formation energy are discussed. Results for the electronic structure of a divacancy are also presented. 3 figures
One-Electron Theory of Metals. Cohesive and Structural Properties
DEFF Research Database (Denmark)
Skriver, Hans Lomholt
The work described in the report r.nd the 16 accompanying publications is based upon a one-electron theory obtained within the local approximation to density-functional theory, and deals with the ground state of metals as obtained from selfconsistent electronic-structure calculations performed...... by means of the Linear Muffin-Tin Orbital (LMTO) method. It has been the goal of the work to establish how well this one-electron approach describes physical properties such as the crystal structures of the transition metals, the structural phase transitions in the alkali, alkaline earth, and rare earth...
Structure and electron-ion correlation in liquid Mg
Energy Technology Data Exchange (ETDEWEB)
Tahara, Shuta [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Fujii, Hiroyuki [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Yokota, Yukinobu [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Kawakita, Yukinobu [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Kohara, Shinji [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Takeda, Shin' ichi [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan)]. E-mail: takeda@rc.kyushu-u.ac.jp
2006-11-15
For liquid Mg at 700 deg. C, structure factors were obtained from both neutron and X-ray diffraction measurements. The bond angle and coordination number distributions were derived from the reverse Monte Carlo analysis. By a combination of both structure factors, charge density function and electron-ion partial structure factor were deduced.
International Nuclear Information System (INIS)
Han Bong Koo
1998-01-01
A reinforced concrete nuclear power plant containment structure is subjected to various random static and stochastic loads during its lifetime. Since these loads involve inherent randomness and other uncertainties, an appropriate probabilistic model for each load must be established in order to perform reliability analysis. The current ASME code for reinforced concrete containment structures are not based on probability concepts. The stochastic nature of natural hazard or accidental loads and the variations of material properties require a probabilistic approach for a rational assessment of structural safety and performance. The paper develops probability-based load factors for the limit state design of reinforced concrete containment structures. The purpose of constructing reinforced concrete containment structure is to protect against radioactive release, and so the use of a serviceability limit state against crack failure that can cause the emission of radioactive materials is suggested as a critical limit state for reinforced concrete containment structures. Load factors for the design of reinforced concrete containment structures are proposed and carried out the reliability assessments. (orig.)
De Wilde, Katrien Sophie; Tency, Inge; Boudrez, Hedwig; Temmerman, Marleen; Maes, Lea; Clays, Els
2016-06-01
Smoking during pregnancy can cause several maternal and neonatal health risks, yet a considerable number of pregnant women continue to smoke. The objectives of this study were to test the factorial structure, validity and reliability of the Dutch version of the Modified Reasons for Smoking Scale (MRSS) in a sample of smoking pregnant women and to understand reasons for continued smoking during pregnancy. A longitudinal design was performed. Data of 97 pregnant smokers were collected during prenatal consultation. Structural equation modelling was performed to assess the construct validity of the MRSS: an exploratory factor analysis was conducted, followed by a confirmatory factor analysis.Test-retest reliability (addiction, pleasure, habit and social function. Results for internal consistency and test-retest reliability were good to acceptable. There were significant associations of nicotine dependence with tension reduction and addiction and of daily consumption with addiction and habit. Validity and reliability of the MRSS were shown in a sample of pregnant smokers. Tension reduction was the most important reason for continued smoking, followed by pleasure and addiction. Although the score for nicotine dependence was low, addiction was an important reason for continued smoking during pregnancy; therefore, nicotine replacement therapy could be considered. Half of the respondents experienced depressive symptoms. Hence, it is important to identify those women who need more specialized care, which can include not only smoking cessation counselling but also treatment for depression. © 2016 John Wiley & Sons, Ltd.
Effects of Common Structural Rules on hull-girder reliability of an Aframax oil tanker
International Nuclear Information System (INIS)
Parunov, Josko; Guedes Soares, C.
2008-01-01
This paper aims at quantifying the changes in notional reliability levels that result from redesigning an existing Aframax tanker to comply with the Common Structural Rules (CSR) for double-hull oil tankers. The probability of structural failure is calculated using the first-order reliability method. The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance with the International Association of Classification Societies (IACS)-recommended procedure, while transfer functions are calculated using the sink-source 3D linear method. The still-water loads are defined on the basis of a statistical analysis of loading conditions from the loading manual. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by progressive collapse analysis and by a single-step procedure according to CSR. The reliability assessment is performed for 'as-built' and 'corroded' states of the existing ship and a reinforced ship complying with CSR. It is shown that the hull-girder failure probability of an Aframax tanker is reduced several times due to the reinforcements according to CSR. Sensitivity analysis and a parametric study are performed to investigate the variability of results with the change of parameters of pertinent random variables within their plausible ranges. Finally, differences between load combination approaches by Ferry-Borges and Castanheta method and Turkstra's rule are investigated
Electronic structure of molecular Rydberg states of some small molecules and molecular ion
International Nuclear Information System (INIS)
Sun Biao; Li Jiaming
1993-01-01
Based on an independent-particle-approximation (i.e. the multiple scattering self-consistent-field theory), the electronic structures of Rydberg states of the small diatomic molecules H 2 , He 2 and the He 2 + molecular ion were studied. The principal quantum number of the first state of the Rydberg series is determined from a convention of the limit of the molecular electronic configuration. The dynamics of the excited molecules and molecular ion has been elucidated. The theoretical results are in fair agreement with the existing experimental measurements, thus they can serve as a reliable basis for future refined treatment such as the configuration interaction calculation
DEFF Research Database (Denmark)
Conseil, Helene; Gudla, Visweswara Chakravarthy; Jellesen, Morten Stendahl
2016-01-01
The design of electronic device enclosures plays a major role in determining the humidity build-up inside the device as a response to the varying external humidity. Therefore, the corrosion reliability of electronic devices has direct connection to the enclosure design. This paper describes......, thermal mass, and port/opening size. The effect of the internal humidity build-up on corrosion reliability has been evaluated by measuring the leakage current (LC) on interdigitated test comb patterns, which are precontaminated with sodium chloride and placed inside the enclosure. The results showed...... that the exposure to cycling temperature causes significant change of internal water vapor concentration. The maximum value of humidity reached was a function of the opening size and the presence of thermal mass inside the enclosure. A pumping effect was observed due to cycling temperature, and the increase...
Structural and electronic parameters of ferroelectric KWOF
Atuchin, V. V.; Gavrilova, T. A.; Kesler, V. G.; Molokeev, M. S.; Aleksandrov, K. S.
2010-11-01
The low-temperature ferroelectric G2 polymorph of K 3WO 3F 3 oxyfluoride is formed by chemical synthesis. The electronic parameters of G2-K 3WO 3F 3 have been measured by X-ray photoelectron spectroscopy under excitation with Al Kα radiation (1486.6 eV). Detailed spectra have been recorded for all element core levels and Auger lines. The chemical bonding effects in the WO 3F 3 and WO 6 octahedrons are considered by using the binding energy difference ΔBE(O-W)=BE(O 1s)-BE(W 4f).
Nodal Structure of the Electronic Wigner Function
DEFF Research Database (Denmark)
Schmider, Hartmut; Dahl, Jens Peder
1996-01-01
On the example of several atomic and small molecular systems, the regular behavior of nodal patterns in the electronic one-particle reduced Wigner function is demonstrated. An expression found earlier relates the nodal pattern solely to the dot-product of the position and the momentum vector......, if both arguments are large. An argument analogous to the ``bond-oscillatory principle'' for momentum densities links the nuclear framework in a molecule to an additional oscillatory term in momenta parallel to bonds. It is shown that these are visible in the Wigner function in terms of characteristic...
Electronic structure of the light actinides
International Nuclear Information System (INIS)
Dunlap, B.D.
1976-01-01
In the last few years, considerable advances have been made in our understanding of the properties of the light actinides. Although these are 5f transition elements formally equivalent to the lanthanide (4f) elements, these materials show a much more varied behavior due to the larger spatial extent and ionizability of the 5f electrons. A review is given of some areas of current interest, especially where hyperfine measurements have played an active role. These include studies of a variety of magnetic phenomena, systematics of isomer shift measurements, and studies of paramagnetic relaxation
Kim, Jae-Woo; Jeong, Jin-Woo; Kang, Jun-Tae; Choi, Sungyoul; Ahn, Seungjoon; Song, Yoon-Ho
2014-02-01
Highly reliable field electron emitters were developed using a formulation for reproducible damage-free carbon nanotube (CNT) composite pastes with optimal inorganic fillers and a ball-milling method. We carefully controlled the ball-milling sequence and time to avoid any damage to the CNTs, which incorporated fillers that were fully dispersed as paste constituents. The field electron emitters fabricated by printing the CNT pastes were found to exhibit almost perfect adhesion of the CNT emitters to the cathode, along with good uniformity and reproducibility. A high field enhancement factor of around 10 000 was achieved from the CNT field emitters developed. By selecting nano-sized metal alloys and oxides and using the same formulation sequence, we also developed reliable field emitters that could survive high-temperature post processing. These field emitters had high durability to post vacuum annealing at 950 °C, guaranteeing survival of the brazing process used in the sealing of field emission x-ray tubes. We evaluated the field emitters in a triode configuration in the harsh environment of a tiny vacuum-sealed vessel and observed very reliable operation for 30 h at a high current density of 350 mA cm-2. The CNT pastes and related field emitters that were developed could be usefully applied in reliable field emission devices.
Energy Technology Data Exchange (ETDEWEB)
Broas, M., E-mail: mikael.broas@aalto.fi; Mattila, T. T.; Paulasto-Kröckel, M. [Department of Electrical Engineering and Automation, Aalto University, Espoo, P.O. Box 13500, FIN-00076 Aalto (Finland); Liu, X.; Ge, Y. [Department of Materials Science and Engineering, Aalto University, Espoo, P.O. Box 16200, FIN-00076 Aalto (Finland)
2015-06-28
This paper describes a reliability assessment and failure analysis of a poly-Si/non-stoichiometric silicon nitride thin film composite structure. A set of poly-Si/SiN{sub x} thin film structures were exposed to a mixed flowing gas (MFG) environment, which simulates outdoor environments, for 90 days, and an elevated temperature and humidity (85 °C/95% R.H.) test for 140 days. The mechanical integrity of the thin films was observed to degrade during exposure to the chemically reactive atmospheres. The degree of degradation was analyzed with nanoindentation tests. Statistical analysis of the forces required to initiate a fracture in the thin films indicated degradation due to the exposure to the MFG environment in the SiN{sub x} part of the films. Scanning electron microscopy revealed a porous-like reaction layer on top of SiN{sub x}. The morphology of the reaction layer resembled that of galvanically corroded poly-Si. Transmission electron microscopy further clarified the microstructure of the reaction layer which had a complex multi-phase structure extending to depths of ∼100 nm. Furthermore, the layer was oxidized two times deeper in a 90 days MFG-tested sample compared to an untested reference. The formation of the layer is proposed to be caused by galvanic corrosion of elemental silicon in non-stoichiometric silicon nitride during hydrofluoric acid etching. The degradation is proposed to be due uncontrolled oxidation of the films during the stress tests.
Yamazaki, H.; Uno, N.; Kurauchi, F.
2012-01-01
This study describes a method of evaluating the level of service of road networks, based on the average travel time and travel time reliability using electronic toll collection (ETC) data. The authors focused on the variance in travel time under normal circumstances, thus, traffic accidents were removed from the database, and any effect of individual vehicle preference was excluded. They evaluated the travel time distribution based on the average travel time from ETC data for each 15-min inte...
Directory of Open Access Journals (Sweden)
Mokeev Alexey
2017-01-01
Full Text Available This paper reviews issues of reliability and efficiency upgrades of power systems functions by means of a widespread implementation of intelligent electronic devices (IED in various purposes supporting synchrophasor measurement technology. Thus, such issues as IED’s operational analysis in the conditions of electromagnetic and electromechanical transient processes and synthesis of digital filters that improve static and dynamic responses of these devices play an important role in their development.
Mokeev Alexey
2017-01-01
This paper reviews issues of reliability and efficiency upgrades of power systems functions by means of a widespread implementation of intelligent electronic devices (IED) in various purposes supporting synchrophasor measurement technology. Thus, such issues as IED’s operational analysis in the conditions of electromagnetic and electromechanical transient processes and synthesis of digital filters that improve static and dynamic responses of these devices play an important role in their devel...
Electron beam crosslinked PVC : structure property relationships
International Nuclear Information System (INIS)
Gupta, Neeraj K.; Sabharwal, Sunil
2001-01-01
PVC is used extensively for its insulating properties for the manufacture of wires and cables and for other applications. Its gradual degradation, oxidation and even dehydro chlorination restricts use for long lasting period in installations such as high temperature zones, underground cables, communication systems, electro-nuclear facilities, etc. The technological properties and performance characteristics of PVC based insulation can be improved via crosslinking by high-energy electrons. PVC is however a polymer, which on irradiation predominantly undergoes degradation. To avoid degradation, it needs to be compounded with sensitizing agents or multifunctional monomers so that crosslinking is the predominant reaction. Radiation cross linkable formulations are complex mixtures of resin and various additives incorporated for achieving desired technological and performance characteristics, ease of processing and improving quality. The proper choice of additives and sensitizing agents enable low dose requirements for efficient crosslinking and improvements in various technological properties. The purposes of this work was to investigate the effect of using a binary sensitizer blend of a trifunctional monomer and a rubber in PVC, and develop suitable electron beam cross linkable formulations for wire insulation. This paper presents some aspects of the investigations and development of insulation demonstrated at industrial scale
Electronic structure and isomer shifts of Sn halides
International Nuclear Information System (INIS)
Terra, J.; Guenzburger, D.
1988-01-01
The all-electron first-principles Discrete Variational method was employed to study the electronic structure of SnF 4 , SnCl 4 , SnBr 4 and SnI 4 . Values of the electronic density at the Sn nucleus were derived and related to 119 Sn Isomer Shifts to obtain the nuclear constant Δ 2 >. Differences in values of ρ(o) area discussed in terms of the chemical bonding between Sn and halogen atoms. (author) [pt
Electronic structure of graphene beyond the linear dispersion regime
POWER, STEPHEN; FERREIRA, MAURO
2011-01-01
PUBLISHED Among the many interesting features displayed by graphene, one of the most attractive is the simplicity with which its electronic structure can be described. The study of its physical properties is significantly simplified by the linear dispersion relation of electrons in a narrow range around the Fermi level. Unfortunately, the mathematical simplicity of graphene electrons is limited only to this narrow energy region and is not very practical when dealing with problems that invo...
International Nuclear Information System (INIS)
Witt, F.J.
1980-01-01
Primary pressure systems of nuclear power plants are built to exacting codes and standards with provisions for inservice inspection and repair if necessary. Analyses and experiments have demonstrated by deterministic means that very large margins exist on safety impacting failures under normal operating and upset conditions. Probabilistic structural reliability analyses provide additional support that failures of significance are very, very remote. They may range in degree of sophistication from very simple calculations to very complex computer analyses involving highly developed mathematical techniques. The end result however should be consistent with the desired usage. In this paper a probabilistic structural reliability analysis is performed as a supplement to in-depth deterministic evaluations with the primary objective to demonstrate an acceptably low probability of failure for the conditions considered. (author)
Finite Element Reliability Analysis of Chloride Ingress into Reinforced Concrete Structures
DEFF Research Database (Denmark)
Frier, Christian; Sørensen, John Dalsgaard
2007-01-01
For many reinforced concrete structures corrosion of the reinforcement is an important problem since it can result in maintenance and repair actions. Further, a reduction of the load-bearing capacity can occur. In the present paper the Finite Element Reliability Method (FERM) is employed for obta......For many reinforced concrete structures corrosion of the reinforcement is an important problem since it can result in maintenance and repair actions. Further, a reduction of the load-bearing capacity can occur. In the present paper the Finite Element Reliability Method (FERM) is employed...... concentration and reinforcement cover depth are modelled by stochastic fields, which are discretized using the Expansion Optimum Linear Estimation (EOLE) approach. The response gradients needed for FORM analysis are derived analytically using the Direct Differentiation Method (DDM). As an example, a bridge pier...... in a marine environment is considered and the results are given in terms of distributions of time for initiation of corrosion....
International Nuclear Information System (INIS)
Maaroufi, S; Parrain, F; Lefeuvre, E; Boutaud, B; Molin, R Dal
2015-01-01
In this paper we propose an approach to study the reliability of piezoelectric structures and more precisely energy harvesting micro-devices dedicated to autonomous active medical implants (new generation pacemakers). The structure under test is designed as a bimorph piezoelectric cantilever with a seismic mass at its tip. Good understanding of material aging and mechanical failure is critical for this kind of system. To study the reliability and durability of the piezoelectric part we propose to establish a new accelerated methodology and an associated test bench where the environment and stimuli can be precisely controlled over a wide period of time. This will allow the identification of potential failure modes and the study of their impacts by the way of direct mechanical investigation based on stiffness and blocking force measurements performed periodically. (paper)
Maaroufi, S.; Parrain, F.; Lefeuvre, E.; Boutaud, B.; Dal Molin, R.
2015-12-01
In this paper we propose an approach to study the reliability of piezoelectric structures and more precisely energy harvesting micro-devices dedicated to autonomous active medical implants (new generation pacemakers). The structure under test is designed as a bimorph piezoelectric cantilever with a seismic mass at its tip. Good understanding of material aging and mechanical failure is critical for this kind of system. To study the reliability and durability of the piezoelectric part we propose to establish a new accelerated methodology and an associated test bench where the environment and stimuli can be precisely controlled over a wide period of time. This will allow the identification of potential failure modes and the study of their impacts by the way of direct mechanical investigation based on stiffness and blocking force measurements performed periodically.
Phase stability and electronic structure of transition-metal aluminides
International Nuclear Information System (INIS)
Carlsson, A.E.
1992-01-01
This paper will describe the interplay between die electronic structure and structural energetics in simple, complex, and quasicrystalline Al-transition metal (T) intermetallics. The first example is the Ll 2 -DO 22 competition in Al 3 T compounds. Ab-initio electronic total-energy calculations reveal surprisingly large structural-energy differences, and show that the phase stability of both stoichiometric and ternary-substituted compounds correlates closely with a quasigap in the electronic density of states (DOS). Secondly, ab-initio calculations for the structural stability of the icosahedrally based Al 12 W structure reveal similar quasigap effects, and provide a simple physical explanation for the stability of the complex aluminide structures. Finally, parametrized tight-binding model calculations for the Al-Mn quasicrystal reveal a large spread in the local Mn DOS behavior, and support a two-site model for the quasicrystal's magnetic behavior
Electronic structure of filled tetrahedral semiconductors
Wood, D.M.; Zunger, Alex; Groot, R. de
1985-01-01
We discuss the susceptibility of zinc-blende semiconductors to band-structure modification by insertion of small atoms at their tetrahedral interstitial states. GaP is found to become a direct-gap semiconductor with two He atoms present at its interstitial sites; Si does not. Analysis of the factors
Electronic Band Structure of Helical Polyisocyanides.
Champagne, Benoît; Liégeois, Vincent; Fripiat, Joseph G; Harris, Frank E
2017-10-19
Restricted Hartree-Fock computations are reported for a methyl isocyanide polymer (repeating unit -C═N-CH 3 ), whose most stable conformation is expected to be a helical chain. The computations used a standard contracted Gaussian orbital set at the computational levels STO-3G, 3-21G, 6-31G, and 6-31G**, and studies were made for two line-group configurations motivated by earlier work and by studies of space-filling molecular models: (1) A structure of line-group symmetry L9 5 , containing a 9-fold screw axis with atoms displaced in the axial direction by 5/9 times the lattice constant, and (2) a structure of symmetry L4 1 that had been proposed, containing a 4-fold screw axis with translation by 1/4 of the lattice constant. Full use of the line-group symmetry was employed to cause most of the computational complexity to depend only on the size of the asymmetric repeating unit. Data reported include computed bond properties, atomic charge distribution, longitudinal polarizability, band structure, and the convoluted density of states. Most features of the description were found to be insensitive to the level of computational approximation. The work also illustrates the importance of exploiting line-group symmetry to extend the range of polymer structural problems that can be treated computationally.
Directory of Open Access Journals (Sweden)
Leszek CHYBOWSKI
2012-01-01
Full Text Available The paper presents the need to develop a description of the importance of the technological systems reliability structure elements in terms of security of the system. Basic issues related to the exploration of weak links and important elements in the system as well as a proposal to develop the current approach to assessing the importance of the system components have been presented. Moreover, the differences between the unreliability of suitability and unreliability of safety have been pointed out.
Reliability and risk functions for structural components taking into account inspection results
International Nuclear Information System (INIS)
Rackwitz, R.; Schall, G.
1989-01-01
The method of outcrossings has been shown to be efficient when calculating the failure probability of metallic structural components under ergodic Gaussian loading. Using Paris/Erdogan's crack growth law it is possible to develop a semi-analytical calculation model for both the reliability and the risk function. For numerical studies an approximate method of asymptotic nature is proposed. The same methodology also enables to incorporate inspection observations. (orig.) [de
Effect of soil–structure interaction on the reliability of reinforced concrete bridges
Kamel Bezih; Alaa Chateauneuf; Mahdi Kalla; Claude Bacconnet
2015-01-01
In the design of reinforced concrete (RC) bridges, the random and nonlinear behavior of soil may lead to insufficient reliability levels. For this reason, it is necessary to take into account the variability of soil properties which can significantly affect the bridge behavior regarding ultimate and serviceability limit states. This study investigates the failure probability for existing reinforced concrete bridges due to the effects of interaction between the soil and the structure. In this ...
Guidelines for Interactive Reliability-Based Structural Optimization using Quasi-Newton Algorithms
DEFF Research Database (Denmark)
Pedersen, C.; Thoft-Christensen, Palle
increase of the condition number and preserve positive definiteness without discarding previously obtained information. All proposed modifications are also valid for non-interactive optimization problems. Heuristic rules from various optimization problems concerning when and how to impose interactions......Guidelines for interactive reliability-based structural optimization problems are outlined in terms of modifications of standard quasi-Newton algorithms. The proposed modifications minimize the condition number of the approximate Hessian matrix in each iteration, restrict the relative and absolute...
Electronic structure and ionicity of actinide oxides from first principles
DEFF Research Database (Denmark)
Petit, Leon; Svane, Axel; Szotek, Z.
2010-01-01
The ground-state electronic structures of the actinide oxides AO, A2O3, and AO2 (A=U, Np, Pu, Am, Cm, Bk, and Cf) are determined from first-principles calculations, using the self-interaction corrected local spin-density approximation. Emphasis is put on the degree of f-electron localization, whi...
On the electronic structure of high Tc superconductors
International Nuclear Information System (INIS)
Fink, J.; Nuecker, N.; Romberg, H.; Alexander, M.; Knupfer, M.; Mante, J.; Claessen, R.; Buslaps, T.; Harm, S.; Manzke, R.; Skibowski, M.
1992-01-01
Studies of the electronic structure of high-T c superconductors and related compounds by high-energy spectroscopies are reviewed. In particular, we report on investigations by electron energy-loss, angle-resolved photoemission, and inverse angle-resolved photoemission spectroscopy. Information on the symmetry and the character of states close to the Fermi level has been obtained. 25 refs., 8 figs
Electronic structure and equilibrium properties of hcp titanium
Indian Academy of Sciences (India)
The electronic structures of hexagonal-close-packed divalent titanium (3-d) and zirconium (4-d) transition metals are studied by using a non-local model potential method. From the present calculation of energy bands, Fermi energy, density of states and the electronic heat capacity of these two metals are determined and ...
Weiss oscillations in the electronic structure of modulated graphene
International Nuclear Information System (INIS)
Tahir, M; Sabeeh, K; MacKinnon, A
2007-01-01
We present a theoretical study of the electronic structure of modulated graphene in the presence of a perpendicular magnetic field. The density of states and the bandwidth for the Dirac electrons in this system are determined. The appearance of unusual Weiss oscillations in the bandwidth and density of states is the main focus of this work
Electronic Structure of Au25 Clusters: Between Discrete and Continuous
Katsiev, Khabiboulakh
2016-07-15
Here, an approach based on synchrotron resonant photoemission is emplyed to explore the transition between quantization and hybridization of the electronic structure in atomically precise ligand-stabilized nanoparticles. While the presence of ligands maintains quantization in Au25 clusters, their removal renders increased hybridization of the electronic states at the vicinity of the Fermi level. These observations are supported by DFT studies.
Electronic Structure of Au25 Clusters: Between Discrete and Continuous
Katsiev, Khabiboulakh; Lozova, Nataliya; Wang, Lu; Katla, Saikrishna; Li, Ruipeng; Mei, Wai Ning; Skrabalak, Sara; Challa, Challa; Losovyj, Yaroslav
2016-01-01
Here, an approach based on synchrotron resonant photoemission is emplyed to explore the transition between quantization and hybridization of the electronic structure in atomically precise ligand-stabilized nanoparticles. While the presence of ligands maintains quantization in Au25 clusters, their removal renders increased hybridization of the electronic states at the vicinity of the Fermi level. These observations are supported by DFT studies.
Electronic Structure of Cdse Nanowires Terminated With Gold ...
African Journals Online (AJOL)
Bheema
Owing to their unusual electronic and structural properties, SC clusters have received considerable attention ... performing molecular dynamics simulations. A similar .... Analysis of the charge density, gap, corresponding to states with energies ...
Structures and electronics of buried and unburied semiconductor interfaces
International Nuclear Information System (INIS)
Kamiya, Itaru
2011-01-01
The structure of interfaces plays an important role in determining the electronic properties of semiconductor nanostructures. Here, such examples are shown and discussed using semiconductor nanostructures prepared by molecular beam epitaxy and colloidal synthesis.
Manganites in Perovskite Superlattices: Structural and Electronic Properties
Jiwuer, Jilili
2016-01-01
Perovskite manganites are widely investigated compounds due to the discovery of the colossal magnetoresistance effect in 1994. They have a broad range of structural, electronic, magnetic properties and potential device applications in sensors
Structure and electron-ion correlation of liquid germanium
Energy Technology Data Exchange (ETDEWEB)
Kawakita, Y. [Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan)]. E-mail: kawakita@rc.kyushu-u.ac.jp; Fujita, S. [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Kohara, S. [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Mikazuki-cho, Hyogo 679-5198 (Japan); Ohshima, K. [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Fujii, H. [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Yokota, Y. [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Takeda, S. [Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan)
2005-08-15
Structure factor of liquid germanium (Ge) has a shoulder at {theta} = 3.2 A{sup -1} in the high-momentum-transfer region of the first peak. To investigate the origin of such a non-simplicity in the structure, high energy X-ray diffraction measurements have been performed using 113.26 keV incident X-ray, at BL04B2 beamline of SPring-8. By a combination of the obtained structure factor with the reported neutron diffraction data, charge density function and electron-ion partial structure factor have been deduced. The peak position of the charge distribution is located at about 1 A, rather smaller r value than the half value of nearest neighbor distance ({approx}2.7 A), which suggests that valence electrons of liquid Ge play a role of screening electrons around a metallic ion rather than covalently bonding electrons.
Structure functions in electron-nucleon deep inelastic scattering
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Fazal-E-Aleem (University of the Punjab, Lahore (Pakistan). Dept. of Physics)
1982-06-26
The phenomenological expressions for the structure functions in electron-nucleon deep inelastic scattering are proposed and are shown to satisfy the experimental data as well as a number of sum rules.
First-principle calculations of structural, electronic, optical, elastic ...
Indian Academy of Sciences (India)
S CHEDDADI
2017-11-28
Nov 28, 2017 ... First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite ... The Kohn–Sham equations were solved using the ... RMTKmax = 7 was used for all the investigated systems,.
Electronic structure of incident carbon ions on a graphite surface
International Nuclear Information System (INIS)
Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.
1997-01-01
The electronic structure of an incident carbon ion on a graphite surface is discussed on the basis of ab initio molecular orbital calculations. A carbon cation forms a covalent bond with the graphite, and a carbon nonion is attracted to the graphite surface through van der Waals interaction. A carbon anion has no stable state on a graphite surface. The charge effects of incident ions become clear upon detailed examination of the electronic structure. (author)
Sustainability of transport structures - some aspects of the nonlinear reliability assessment
Pukl, Radomír; Sajdlová, Tereza; Strauss, Alfred; Lehký, David; Novák, Drahomír
2017-09-01
Efficient techniques for both nonlinear numerical analysis of concrete structures and advanced stochastic simulation methods have been combined in order to offer an advanced tool for assessment of realistic behaviour, failure and safety assessment of transport structures. The utilized approach is based on randomization of the non-linear finite element analysis of the structural models. Degradation aspects such as carbonation of concrete can be accounted in order predict durability of the investigated structure and its sustainability. Results can serve as a rational basis for the performance and sustainability assessment based on advanced nonlinear computer analysis of the structures of transport infrastructure such as bridges or tunnels. In the stochastic simulation the input material parameters obtained from material tests including their randomness and uncertainty are represented as random variables or fields. Appropriate identification of material parameters is crucial for the virtual failure modelling of structures and structural elements. Inverse analysis using artificial neural networks and virtual stochastic simulations approach is applied to determine the fracture mechanical parameters of the structural material and its numerical model. Structural response, reliability and sustainability have been investigated on different types of transport structures made from various materials using the above mentioned methodology and tools.
Improved reliability, accuracy and quality in automated NMR structure calculation with ARIA
Energy Technology Data Exchange (ETDEWEB)
Mareuil, Fabien [Institut Pasteur, Cellule d' Informatique pour la Biologie (France); Malliavin, Thérèse E.; Nilges, Michael; Bardiaux, Benjamin, E-mail: bardiaux@pasteur.fr [Institut Pasteur, Unité de Bioinformatique Structurale, CNRS UMR 3528 (France)
2015-08-15
In biological NMR, assignment of NOE cross-peaks and calculation of atomic conformations are critical steps in the determination of reliable high-resolution structures. ARIA is an automated approach that performs NOE assignment and structure calculation in a concomitant manner in an iterative procedure. The log-harmonic shape for distance restraint potential and the Bayesian weighting of distance restraints, recently introduced in ARIA, were shown to significantly improve the quality and the accuracy of determined structures. In this paper, we propose two modifications of the ARIA protocol: (1) the softening of the force field together with adapted hydrogen radii, which is meaningful in the context of the log-harmonic potential with Bayesian weighting, (2) a procedure that automatically adjusts the violation tolerance used in the selection of active restraints, based on the fitting of the structure to the input data sets. The new ARIA protocols were fine-tuned on a set of eight protein targets from the CASD–NMR initiative. As a result, the convergence problems previously observed for some targets was resolved and the obtained structures exhibited better quality. In addition, the new ARIA protocols were applied for the structure calculation of ten new CASD–NMR targets in a blind fashion, i.e. without knowing the actual solution. Even though optimisation of parameters and pre-filtering of unrefined NOE peak lists were necessary for half of the targets, ARIA consistently and reliably determined very precise and highly accurate structures for all cases. In the context of integrative structural biology, an increasing number of experimental methods are used that produce distance data for the determination of 3D structures of macromolecules, stressing the importance of methods that successfully make use of ambiguous and noisy distance data.
International Nuclear Information System (INIS)
Ling, Yang; Gui-Zhou, Hu; Yue, Hao; Xiao-Hua, Ma; Si, Quan; Li-Yuan, Yang; Shou-Gao, Jiang
2010-01-01
This paper investigates the impact of electrical degradation and current collapse on different thickness SiN x passivated AlGaN/GaN high electron mobility transistors. It finds that higher thickness SiN x passivation can significantly improve the high-electric-field reliability of a device. The degradation mechanism of the SiN x passivation layer under ON-state stress has also been discussed in detail. Under the ON-state stress, the strong electric-field led to degradation of SiN x passivation located in the gate-drain region. As the thickness of SiN x passivation increases, the density of the surface state will be increased to some extent. Meanwhile, it is found that the high NH 3 flow in the plasma enhanced chemical vapour deposition process could reduce the surface state and suppress the current collapse. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Some aspects of the reliability-based design of reactor containment structures
International Nuclear Information System (INIS)
Schueller, G.I.
1975-01-01
It is generally recognized that the load which a structure is likely to experience during its design life as well as its resistance are to be represented by random variables. A rational design procedure for reactor containment structures can therefore only be carried out within a probabilistic framework. Internal load conditions caused by system failure such as loss-of-coolant accident, pressure loads etc., and external load conditions caused for instance by impact due to aircraft crashes, external pressure waves and natural hazards such as earthquakes, floods, hurricanes are described by extreme value distributions of the Fisher-Tippett types. Statistical and physical arguments are given to support their application. The occurrence of these rare events with respect to time is modeled by a Poisson process. The yield strength of the containment structure for both steel (liner) and reinforced concrete shells is also modeled by extreme value distributions (of the smallest values). The failure criterion considered here is that of collapse determined by plastic yieldline formation. A failure mechanism as considered here describes a particular regime of plastic line formation. The probability of failure of a structure under a single load application of load types likely to occur during the design life of the structure is to be determined by integrating over all possible mechanisms. Finally Freudenthal's reliability function is utilized to combine the information derived above so that a containment design for given design lifes and reliabilities is possible. (orig.) [de
Reliability and safety engineering
Verma, Ajit Kumar; Karanki, Durga Rao
2016-01-01
Reliability and safety are core issues that must be addressed throughout the life cycle of engineering systems. Reliability and Safety Engineering presents an overview of the basic concepts, together with simple and practical illustrations. The authors present reliability terminology in various engineering fields, viz.,electronics engineering, software engineering, mechanical engineering, structural engineering and power systems engineering. The book describes the latest applications in the area of probabilistic safety assessment, such as technical specification optimization, risk monitoring and risk informed in-service inspection. Reliability and safety studies must, inevitably, deal with uncertainty, so the book includes uncertainty propagation methods: Monte Carlo simulation, fuzzy arithmetic, Dempster-Shafer theory and probability bounds. Reliability and Safety Engineering also highlights advances in system reliability and safety assessment including dynamic system modeling and uncertainty management. Cas...
Riggs, William R.
1994-05-01
SHARP is a Navy wide logistics technology development effort aimed at reducing the acquisition costs, support costs, and risks of military electronic weapon systems while increasing the performance capability, reliability, maintainability, and readiness of these systems. Lower life cycle costs for electronic hardware are achieved through technology transition, standardization, and reliability enhancement to improve system affordability and availability as well as enhancing fleet modernization. Advanced technology is transferred into the fleet through hardware specifications for weapon system building blocks of standard electronic modules, standard power systems, and standard electronic systems. The product lines are all defined with respect to their size, weight, I/O, environmental performance, and operational performance. This method of defining the standard is very conducive to inserting new technologies into systems using the standard hardware. This is the approach taken thus far in inserting photonic technologies into SHARP hardware. All of the efforts have been related to module packaging; i.e. interconnects, component packaging, and module developments. Fiber optic interconnects are discussed in this paper.
Electronic structure of UCl5: A reexamination
International Nuclear Information System (INIS)
Soule, E.; Edelstein, N.
1980-01-01
On the basis of the absorption spectrum of UCl 5 recorded at 4.2 K, Leung and Poon attempted a determination of both the spin-orbit coupling constant and the crystal field parameters. Their parameters, however, led to a calculated g-tensor at variance with the position of the electron paramagnetic resonance line observed by Miyake et al. It was therefore attempted to simultaneously interpret both spectra (absorption and EPR), assuming the validity of the Newman superposition model, and taking the point symmetry group on each uranium of the (UCl 5 ) 2 dimer as C 2 sub(v). We obtain one and only one satisfactory solution, namely a set of parameters that reasonably reproduce the observed absorption peaks, and lead to the following principal values of the g-tensor: gx = 0.226 (unobservable); gy = 1.187; gz = 1.186. Therefore the paradox stemming from the apparent isotropy of the EPR signal for a species of low point symmetry is resolved. (orig.)
Electronic structure of metal overlayers on rhodium
International Nuclear Information System (INIS)
Feibelman, P.J.; Hamann, D.R.
1983-01-01
We have evaluated work functions, surface core-level shifts, and surface band dispersions for clean, Ag-covered, and Pd-covered Rh(100) surfaces, and for clean and Ag-covered Rh(111). The calculations were performed self-consistently, using the surface-linearized augmented-plane-wave method. As expected from the Pauling electronegativities, Ag adsorption lowers the work function from the clean Rh value, by several tenths of an eV, while Pd has an almost negligible effect. The values calculated for the core-level shifts of various films are shown to correspond to expectations based on surface band narrowing and layerwise charge neutrality. Using the core-level shifts, we predict heat-of-adsorption differences (for Ag on Pd vs Ag on Rh, etc.) that are in quite good agreement with the empirical predictions of Miedema and Dorleijn. Finally, the chemical inactivity of the Ag-covered Rh surface is associated with the fact that, for that system, the outer-layer local density of states is essentially that of Ag, with a characteristically low value at the Fermi energy. On the other hand, the Pd-covered Rh surface should behave much like clean Rh with an extra electron per surface atom. The surface band dispersions for the Pd-covered and clean Rh surfaces are closely similar. This result contrasts sharply with the case of Pd-covered Nb, for which, because of the appreciable electronegativity difference, the Pd overlayer is effectively ''noble.''
Electronic structure properties of UO2 as a Mott insulator
Sheykhi, Samira; Payami, Mahmoud
2018-06-01
In this work using the density functional theory (DFT), we have studied the structural, electronic and magnetic properties of uranium dioxide with antiferromagnetic 1k-, 2k-, and 3k-order structures. Ordinary approximations in DFT, such as the local density approximation (LDA) or generalized gradient approximation (GGA), usually predict incorrect metallic behaviors for this strongly correlated electron system. Using Hubbard term correction for f-electrons, LDA+U method, as well as using the screened Heyd-Scuseria-Ernzerhof (HSE) hybrid functional for the exchange-correlation (XC), we have obtained the correct ground-state behavior as an insulator, with band gaps in good agreement with experiment.
New Insight into Carbon Nanotube Electronic Structure Selectivity
Energy Technology Data Exchange (ETDEWEB)
Sumpter, Bobby G [ORNL; Meunier, Vincent [ORNL; Jiang, Deen [ORNL
2009-01-01
The fundamental role of aryl diazonium salts for post synthesis selectivity of carbon nanotubes is investigated using extensive electronic structure calculations. The resulting understanding for diazonium salt based selective separation of conducting and semiconducting carbon nanotubes shows how the primary contributions come from the interplay between the intrinsic electronic structure of the carbon nanotubes and that of the anion of the salt. We demonstrate how the electronic transport properties change upon the formation of charge transfer complexes and upon their conversion into covalently attached functional groups. Our results are found to correlate well with experiments and provide for the first time an atomistic description for diazonium salt based chemical separation of carbon nanotubes
Electronic structure of the copper oxides
International Nuclear Information System (INIS)
Pickett, W.E.; Cohen, R.E.; Singh, D.; Krakauer, H.
1989-01-01
Since the discovery of the high temperature superconducting copper oxides a great deal has been learned from experiment about their behavior. From the theoretical side, there continues to be developments both within the band picture and from the model Hamiltonian viewpoint emphasizing correlations. In this paper the authors discuss these complementary viewpoints in relation to some of the experimental data. Due to their background in the band structure area, they approach the discussion by evaluating which phenomena can be (or has been) accounted for by the standard band approach, and point out which properties appear to require more intricate treatments of correlation
Electronic and geometric structures of calcium metaborates
International Nuclear Information System (INIS)
Baranovskij, V.I.; Lopatin, S.I.; Sizov, V.V.
2000-01-01
Calculations of geometric structure, vibration frequencies, ionization potentials and atomization energies of CaBO 2 and CaB 2 O 4 molecules were made. It is shown that linear conformations of the molecules are the most stable ones. In the metaborates studied calcium atom coordination with oxygen is a monodentate one, meanwhile CaB 2 O 4 can be considered as a Ca 2+ compound, whereas CaBO 2 - as a Ca + compound, which explains similarity of the molecule (from the viewpoint of its geometry, spectral and energy characteristics) to alkaline metal metaborates [ru
Equilibrium and nonequilibrium solvation and solute electronic structure
International Nuclear Information System (INIS)
Kim, H.J.; Hynes, J.T.
1990-01-01
When a molecular solute is immersed in a polar and polarizable solvent, the electronic wave function of the solute system is altered compared to its vacuum value; the solute electronic structure is thus solvent-dependent. Further, the wave function will be altered depending upon whether the polarization of the solvent is or is not in equilibrium with the solute charge distribution. More precisely, while the solvent electronic polarization should be in equilibrium with the solute electronic wave function, the much more sluggish solvent orientational polarization need not be. We call this last situation non-equilibrium solvation. We outline a nonlinear Schroedinger equation approach to these issues
Structure and electronic properties of azadirachtin.
de Castro, Elton A S; de Oliveira, Daniel A B; Farias, Sergio A S; Gargano, Ricardo; Martins, João B L
2014-02-01
We performed a combined DFT and Monte Carlo (13)C NMR chemical-shift study of azadirachtin A, a triterpenoid that acts as a natural insect antifeedant. A conformational search using a Monte Carlo technique based on the RM1 semiempirical method was carried out in order to establish its preferred structure. The B3LYP/6-311++G(d,p), wB97XD/6-311++G(d,p), M06/6-311++G(d,p), M06-2X/6-311++G(d,p), and CAM-B3LYP/6-311++G(d,p) levels of theory were used to predict NMR chemical shifts. A Monte Carlo population-weighted average spectrum was produced based on the predicted Boltzmann contributions. In general, good agreement between experimental and theoretical data was obtained using both methods, and the (13)C NMR chemical shifts were predicted highly accurately. The geometry was optimized at the semiempirical level and used to calculate the NMR chemical shifts at the DFT level, and these shifts showed only minor deviations from those obtained following structural optimization at the DFT level, and incurred a much lower computational cost. The theoretical ultraviolet spectrum showed a maximum absorption peak that was mainly contributed by the tiglate group.
Structural complexities in the active layers of organic electronics.
Lee, Stephanie S; Loo, Yueh-Lin
2010-01-01
The field of organic electronics has progressed rapidly in recent years. However, understanding the direct structure-function relationships between the morphology in electrically active layers and the performance of devices composed of these materials has proven difficult. The morphology of active layers in organic electronics is inherently complex, with heterogeneities existing across multiple length scales, from subnanometer to micron and millimeter range. A major challenge still facing the organic electronics community is understanding how the morphology across all of the length scales in active layers collectively determines the device performance of organic electronics. In this review we highlight experiments that have contributed to the elucidation of structure-function relationships in organic electronics and also point to areas in which knowledge of such relationships is still lacking. Such knowledge will lead to the ability to select active materials on the basis of their inherent properties for the fabrication of devices with prespecified characteristics.
Reliability Analysis-Based Numerical Calculation of Metal Structure of Bridge Crane
Directory of Open Access Journals (Sweden)
Wenjun Meng
2013-01-01
Full Text Available The study introduced a finite element model of DQ75t-28m bridge crane metal structure and made finite element static analysis to obtain the stress response of the dangerous point of metal structure in the most extreme condition. The simulated samples of the random variable and the stress of the dangerous point were successfully obtained through the orthogonal design. Then, we utilized BP neural network nonlinear mapping function trains to get the explicit expression of stress in response to the random variable. Combined with random perturbation theory and first-order second-moment (FOSM method, the study analyzed the reliability and its sensitivity of metal structure. In conclusion, we established a novel method for accurately quantitative analysis and design of bridge crane metal structure.
International Nuclear Information System (INIS)
Edwards, Lyndon
2005-01-01
Full text: The determination of accurate, reliable stresses is critical to many fields of engineering and, in particular, the structural integrity and hence, safety, of many systems. Neutron stress measurement is a non-destructive technique that uniquely provides insights into stress fields deep within components and structures. As such, it has become an increasingly important tool within the engineering community leading to improved manufacturing processes to reduce stress and distortion as well as to the definition of more precise structural integrity lifting procedures. This talk describes the current state of the art and identifies the key opportunities for improved structural integrity provided by the 2nd generation dedicated engineering stress diffractometers currently being designed and commissioned world-wide. Examples are provided covering a range of industrially relevant problems from the fields. (author)
Approximation of the Monte Carlo Sampling Method for Reliability Analysis of Structures
Directory of Open Access Journals (Sweden)
Mahdi Shadab Far
2016-01-01
Full Text Available Structural load types, on the one hand, and structural capacity to withstand these loads, on the other hand, are of a probabilistic nature as they cannot be calculated and presented in a fully deterministic way. As such, the past few decades have witnessed the development of numerous probabilistic approaches towards the analysis and design of structures. Among the conventional methods used to assess structural reliability, the Monte Carlo sampling method has proved to be very convenient and efficient. However, it does suffer from certain disadvantages, the biggest one being the requirement of a very large number of samples to handle small probabilities, leading to a high computational cost. In this paper, a simple algorithm was proposed to estimate low failure probabilities using a small number of samples in conjunction with the Monte Carlo method. This revised approach was then presented in a step-by-step flowchart, for the purpose of easy programming and implementation.
Commercial Off-The-Shelf (COTS) Electronics Reliability for Space Applications
Pellish, Jonathan
2018-01-01
This presentation describes the accelerating use of Commercial off the Shelf (COTS) parts in space applications. Component reliability and threats in the context of the mission, environment, application, and lifetime. Provides overview of traditional approaches applied to COTS parts in flight applications, and shows challenges and potential paths forward for COTS systems in flight applications it's all about data!
Scaltro, F.; Biglari, M.H.; Kodentsov, A.; Yakovleva, O.; Brom, E.
2009-01-01
The reliability of lead-free (LF) solder joints in surface-mounted device components (SMD) has been investigated after thermo-cycle testing. Kirkendall voids have been observed at the interface component/solder together with the formation of fractures. The evolution, the morphology and the elemental
First-principles study of the structural and electronic properties of III-phosphides
Energy Technology Data Exchange (ETDEWEB)
Ahmed, Rashid [Centre for High Energy Physics, University of the Punjab, Lahore 54590 (Pakistan)], E-mail: rasofi@hotmail.com; Fazal-e-Aleem [Centre for High Energy Physics, University of the Punjab, Lahore 54590 (Pakistan); Hashemifar, S. Javad; Akbarzadeh, Hadi [Department of Physics, Isfahan University of Technology, Isfahan 84156 (Iran, Islamic Republic of)
2008-05-01
We use density functional theory and different forms of the exchange-correlation approximation to calculate the structural and electronic properties of tetrahedrally coordinated III-phosphide semiconductors. The computed results for structural properties using generalized gradient approximation (GGA) agree well with the experimental data. For reliable description of energy band gap values, another form of GGA developed by Engel and Vosko has been applied. As anticipated, boron phosphide was found to be the hardest compound due to the strong B-P covalent bonding.
Adsorbate-induced modification of electronic band structure of epitaxial Bi(111) films
Energy Technology Data Exchange (ETDEWEB)
Matetskiy, A.V., E-mail: mateckij@iacp.dvo.ru [Institute of Automation and Control Processes FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); Bondarenko, L.V.; Tupchaya, A.Y.; Gruznev, D.V. [Institute of Automation and Control Processes FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); Eremeev, S.V. [Institute of Strength Physics and Materials Science, 634021 Tomsk (Russian Federation); Tomsk State University, 634050 Tomsk (Russian Federation); Zotov, A.V. [Institute of Automation and Control Processes FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); School of Natural Sciences, Far Eastern Federal University, 690950 Vladivostok (Russian Federation); Department of Electronics, Vladivostok State University of Economics and Service, 690600 Vladivostok (Russian Federation); Saranin, A.A. [Institute of Automation and Control Processes FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); School of Natural Sciences, Far Eastern Federal University, 690950 Vladivostok (Russian Federation)
2017-06-01
Highlights: • Modification of electronic properties of ultrathin Bi films by adsorbates is demonstrated. • Due to electron doping from Cs adatoms, surface-state bands shift to higher binding energies. • As a result, only electron pockets are left in the Fermi map. • Tin acts as an acceptor dopant for Bi, shifting Fermi level upward. • As a result, only hole pockets are left in the Fermi map. - Abstract: Changes of the electronic band structure of Bi(111) films on Si(111) induced by Cs and Sn adsorption have been studied using angle-resolved photoemission spectroscopy and density functional theory calculations. It has been found that small amounts of Cs when it presents at the surface in a form of the adatom gas leads to shifting of the surface and quantum well states to the higher binding energies due to the electron donation from adsorbate to the Bi film. In contrast, adsorbed Sn dissolves into the Bi film bulk upon heating and acts as an acceptor dopant, that results in shifting of the surface and quantum well states upward to the lower binding energies. These results pave the way to manipulate with the Bi thin film electron band structure allowing to achieve a certain type of conductivity (electron or hole) with a single spin channel at the Fermi level making the adsorbate-modified Bi a reliable base for prospective spintronics applications.
Atomic and electronic structures of divacancy in graphene nanoribbons
Energy Technology Data Exchange (ETDEWEB)
Zhao Jun [College of Physical Science and Technology, Yangtze University, Jingzhou, Hubei 434023 (China); Zeng Hui, E-mail: zenghui@yangtzeu.edu.cn [College of Physical Science and Technology, Yangtze University, Jingzhou, Hubei 434023 (China); Wei Jianwei [School of Mathematics and Physics, Chongqing University of Technology, Chongqing 400054 (China)
2012-01-15
First principles calculations have been performed to investigate the electronic structures and transport properties of defective graphene nanoribbons (GNRs) in the presence of pentagon-octagon-pentagon (5-8-5) defects. Electronic band structure results reveal that 5-8-5 defects in the defective zigzag graphene nanoribbon (ZGNR) is unfavorable for electronic transport. However, such defects in the defective armchair graphene nanoribbon (AGNR) give rise to smaller band gap than that in the pristine AGNR, and eventually results in semiconductor to metal-like transition. The distinct roles of 5-8-5 defects in two kinds of edged-GNR are attributed to the different coupling between {pi}{sup Low-Asterisk} and {pi} subbands influenced by the defects. Our findings indicate the possibility of a new route to improve the electronic transport properties of graphene nanoribbons via tailoring the atomic structures by ion irradiation.
Electronic structure of a graphene superlattice with massive Dirac fermions
International Nuclear Information System (INIS)
Lima, Jonas R. F.
2015-01-01
We study the electronic and transport properties of a graphene-based superlattice theoretically by using an effective Dirac equation. The superlattice consists of a periodic potential applied on a single-layer graphene deposited on a substrate that opens an energy gap of 2Δ in its electronic structure. We find that extra Dirac points appear in the electronic band structure under certain conditions, so it is possible to close the gap between the conduction and valence minibands. We show that the energy gap E g can be tuned in the range 0 ≤ E g ≤ 2Δ by changing the periodic potential. We analyze the low energy electronic structure around the contact points and find that the effective Fermi velocity in very anisotropic and depends on the energy gap. We show that the extra Dirac points obtained here behave differently compared to previously studied systems
Effects of Structural Correlations on Electronic Properties
International Nuclear Information System (INIS)
Pastawski, H.M.; Weisz, J.F.
1984-01-01
A one dimensional alloy model is treated in the nearest neighbour tight binding approximation in which the correlation of the atoms can be adjusted. The correlation can be changed from a situation in which there is a tendency for atoms to alternate to a situation in which the atoms are randomly located, consistent with a fixed concentration c for A c B 1-c . The results show that when there is short range order, at certain energies there is a tendency for localized states and formation of structure induced minimum in the density of states. The results for the ordered case are similar to those of Charge Density Wave (CDW). A smooth transition is carried out between this case and the randomly disordered case which behaves like the Anderson model for uncorrelated disorder. (M.W.O.) [pt
The surface electronic structure of Y(0001)
International Nuclear Information System (INIS)
Searle, C.
1998-12-01
Yttrium has been grown epitaxially on W(110). The growth was monitored by using photoemission spectroscopy with a synchrotron radiation source. The film thickness has been gauged by the attenuation of the W 4f 7/2 bulk component. The films have been grown reproducibly and show a prominent surface state which is indicative of good order and low contamination. Angle-Resolved Ultra-Violet Photoemission Spectroscopy has been used to examine the valence band of these ultra-thin films. The films show a very different structure to the valence band of a bulk crystal of yttrium. The differences have been investigated by a series of model calculations using the LMASA-46 tight-binding LMTO program. The calculations suggest that the ultra-thin film surface state may be hybridised with a tungsten orbital having (x 2 - y 2 ) character. (author)
Egle, Jonathan P; Smeenge, David M; Kassem, Kamal M; Mittal, Vijay K
2015-01-01
Electronic sources of medical information are plentiful, and numerous studies have demonstrated the use of the Internet by patients and the variable reliability of these sources. Studies have investigated neither the use of web-based resources by residents, nor the reliability of the information available on these websites. A web-based survey was distributed to surgical residents in Michigan and third- and fourth-year medical students at an American allopathic and osteopathic medical school and a Caribbean allopathic school regarding their preferred sources of medical information in various situations. A set of 254 queries simulating those faced by medical trainees on rounds, on a written examination, or during patient care was developed. The top 5 electronic resources cited by the trainees were evaluated for their ability to answer these questions accurately, using standard textbooks as the point of reference. The respondents reported a wide variety of overall preferred resources. Most of the 73 responding medical trainees favored textbooks or board review books for prolonged studying, but electronic resources are frequently used for quick studying, clinical decision-making questions, and medication queries. The most commonly used electronic resources were UpToDate, Google, Medscape, Wikipedia, and Epocrates. UpToDate and Epocrates had the highest percentage of correct answers (47%) and Wikipedia had the lowest (26%). Epocrates also had the highest percentage of wrong answers (30%), whereas Google had the lowest percentage (18%). All resources had a significant number of questions that they were unable to answer. Though hardcopy books have not been completely replaced by electronic resources, more than half of medical students and nearly half of residents prefer web-based sources of information. For quick questions and studying, both groups prefer Internet sources. However, the most commonly used electronic resources fail to answer clinical queries more than half
International Nuclear Information System (INIS)
Manikandan, M.; Santhosh, M.; Rajeswarapalanichamy, R.
2016-01-01
Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of actinide carbides AnC (An=U, Np) for three different crystal structures, namely NaCl, CsCl and ZnS. Among the considered structures, NaCl structure is found to be the most stable structure for these carbides at normal pressure. A pressure induced structural phase transition from NaCl to ZnS is observed. The electronic structure reveals that these carbides are metals. The calculated elastic constants indicate that these carbides are mechanically stable at normal pressure.
Corroded Anchor Structure Stability/Reliability (CAS_Stab-R) Software for Hydraulic Structures
2017-12-01
Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199 Final report Approved for public release...and maintenance of a large inventory of concrete navigation structures. Over the last 40 years, a number of existing Corps hydraulic structures have...ORGANIZATION NAME(S) AND ADDRESS(ES) Information Technology Laboratory U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road
Electronic properties in a quantum well structure of Weyl semimetal
International Nuclear Information System (INIS)
You, Wen-Long; Zhou, Jiao-Jiao; Wang, Xue-Feng; Oleś, Andrzej M.
2016-01-01
We investigate the confined states and transport of three-dimensional Weyl electrons around a one-dimensional external rectangular electrostatic potential. The confined states with finite transverse wave vector exist at energies higher than the half well depth or lower than the half barrier height. The rectangular potential appears completely transparent to the normal incident electrons but not otherwise. The tunneling transmission coefficient is sensitive to their incident angle and shows resonant peaks when their energy coincides with the confined spectra. In addition, for the electrons in the conduction (valence) band through a potential barrier (well), the transmission spectrum has a gap of width increasing with the incident angle. Interestingly, the electron linear zero-temperature conductance over the potential can approach zero when the Fermi energy is aligned to the top and bottom energies of the potential, when only electron beams normal to the potential interfaces can pass through. The considered structure can be used to collimate the Weyl electron beams.
Effect of electron emission on an ion sheath structure
International Nuclear Information System (INIS)
Mishra, M K; Phukan, A; Chakraborty, M
2014-01-01
This article reports on the variations of ion sheath structures due to the emission of both hot and cold electrons in the target plasma region of a double plasma device. The ion sheath is produced in front of a negatively biased plate. The plasma is produced by hot filament discharge in the source region, and no discharge is created in the target region of the device. The plate is placed in the target (diffused plasma) region where cold electron emitting filaments are present. These cold electrons are free from maintenance of discharge, which is sustained in the source region. The hot ionizing electrons are present in the source region. Three important parameters are changed by both hot and cold electrons i.e. plasma density, plasma potential and electron temperature. The decrease in plasma potential and the increase in plasma density lead to the contraction of the sheath. (paper)
Structure Identification in High-Resolution Transmission Electron Microscopic Images
DEFF Research Database (Denmark)
Vestergaard, Jacob Schack; Kling, Jens; Dahl, Anders Bjorholm
2014-01-01
A connection between microscopic structure and macroscopic properties is expected for almost all material systems. High-resolution transmission electron microscopy is a technique offering insight into the atomic structure, but the analysis of large image series can be time consuming. The present ...
Electronic and chemical properties of graphene-based structures:
DEFF Research Database (Denmark)
Vanin, Marco
In the present thesis several aspects of graphene-based structures have been investigated using density functional theory calculations to solve the electronic structure problem. A review of the implementation of a localized basis-set within the projector augmented wave method - the way of describ...... are attractive candidates although issues regarding the poisoning of the active site remain to be addressed....
Electronic structure of palladium and its relation to uv spectroscopy
DEFF Research Database (Denmark)
Christensen, N.E.
1976-01-01
The electronic-energy-band structure of palladium has been calculated by means of the relativistic augmented-plane-wave method covering energies up to 30 eV above the Fermi level. The optical interband transitions producing structure in the dielectric function up to photon energies of 25 eV have ...
The electron irradiation effects in different structures of diodes
International Nuclear Information System (INIS)
Li Quanfen; Wang Jiaxu
1993-01-01
This paper describes the different electron irradiation effects in different structures of diodes and the different results produced by different irradiation ways. From this work, we can know how to choose proper manufacture arts and comprehensive factors according to the structures of diodes and the irradiation conditions
Directory of Open Access Journals (Sweden)
Vuković Mira H.
2015-01-01
Full Text Available Introduction: The structure of healthcare professionals' economic reasoning (HPER is still unknown. The aim: The structural validity and the reliability of the HPER questionnaire were evaluated. Methods: The psychometric study about evaluation of the HPER factors was conducted. The healthcare professionals (physicians, dentists, pharmacists that are employed in healthcare state sector of Republic of Serbia were interviewed. The HPER Questionnaire contained 29 preliminary items. Its structure was evaluated by Principal Component Analysis for categorial and ordinal data. Results: The 9 items that defined seven HPER factors were extracted: (1 the negligence of the cost of quality by the administration and financier; (2 the consideration of the market price and healthcare benefit; (3 market orientation considering patient's requests; (4 the recognition of inadequate resource alocations by non-medical administrative authority; (5 the attitude about redirecting the profit from state to private healthcare sector; (6 the recognition of the unjustified spending by the healthcare professionals and (7 the relationship physician/patient. Conclusion: The HPER-9 Questionnaire has high structural validity and reliability in the HPER measurement.
Electron vortex magnetic holes: A nonlinear coherent plasma structure
Energy Technology Data Exchange (ETDEWEB)
Haynes, Christopher T., E-mail: c.t.haynes@qmul.ac.uk; Burgess, David; Sundberg, Torbjorn [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Camporeale, Enrico [Multiscale Dynamics, Centrum Wiskunde and Informatica (CWI), Amsterdam (Netherlands)
2015-01-15
We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.
Chemical modulation of electronic structure at the excited state
Li, F.; Song, C.; Gu, Y. D.; Saleem, M. S.; Pan, F.
2017-12-01
Spin-polarized electronic structures are the cornerstone of spintronics, and have thus attracted a significant amount of interest; in particular, researchers are looking into how to modulate the electronic structure to enable multifunctional spintronics applications, especially in half-metallic systems. However, the control of the spin polarization has only been predicted in limited two-dimensional systems with spin-polarized Dirac structures and is difficult to achieve experimentally. Here, we report the modulation of the electronic structure in the light-induced excited state in a typical half-metal, L a1 /2S r1 /2Mn O3 -δ . According to the spin-transport measurements, there appears a light-induced increase in magnetoresistance due to the enhanced spin scattering, which is closely associated with the excited spin polarization. Strikingly, the light-induced variation can be enhanced via alcohol processing and reduced by oxygen annealing. X-ray photoelectron spectroscopy measurements show that in the chemical process, a redox reaction occurs with a change in the valence of Mn. Furthermore, first-principles calculations reveal that the change in the valence of Mn alters the electronic structure and consequently modulates the spin polarization in the excited state. Our findings thus report a chemically tunable electronic structure, demonstrating interesting physics and the potential for multifunctional applications and ultrafast spintronics.
Energy Technology Data Exchange (ETDEWEB)
Moan, Torgeir [Centre for Ships and Ocean Structures, Norwegian University of Science and Technology, Marine Technology Centre, Tyholt, N 7491 Trondheim (Norway)], E-mail: tormo@marin.ntnu.no; Ayala-Uraga, Efren [Department of Marine Technology, Norwegian University of Science and Technology, Marine Technology Centre, Tyholt, N 7491 Trondheim (Norway)
2008-03-15
A reliability-based model for assessment of deteriorating ships subjected to multiple environmental conditions is established. Deterioration due to combined crack growth and corrosion in structural components of a ship hull is accounted for based on a fracture mechanics formulation. The model enables to take into account the corrosion-induced increased crack growth rate in two ways: (1) the increased stress range produced by the plate thinning (wastage) effect and (2) corrosion fatigue itself. Sensitivity studies are carried out to evaluate the effect of inspection updating on a production ship subjected to two different climate conditions. The hazard rate concept is adopted as a measure of reliability and emphasized throughout the different case studies.
On New Cautious Structural Reliability Models in the Framework of imprecise Probabilities
DEFF Research Database (Denmark)
Utkin, Lev V.; Kozine, Igor
2010-01-01
models and gen-eralizing conventional ones to imprecise probabili-ties. The theoretical setup employed for this purpose is imprecise statistical reasoning (Walley 1991), whose general framework is provided by upper and lower previsions (expectations). The appeal of this theory is its ability to capture......Uncertainty of parameters in engineering design has been modeled in different frameworks such as inter-val analysis, fuzzy set and possibility theories, ran-dom set theory and imprecise probability theory. The authors of this paper for many years have been de-veloping new imprecise reliability...... both aleatory (stochas-tic) and epistemic uncertainty and the flexibility with which information can be represented. The previous research of the authors related to generalizing structural reliability models to impre-cise statistical measures is summarized in Utkin & Kozine (2002) and Utkin (2004...
Morales, Alexandra; Reis, Sibília; Espada, José P; Orgilés, Mireia
2016-09-01
The Short Health Anxiety Inventory is a brief instrument to assess health anxiety widely used across countries; however, no validated version is available for Portuguese-speaking population. Factorial structure, reliability, and equivalency factor with the Spanish version were analyzed with Portuguese adolescents aged 14-18 years. A Portuguese adolescent cohort ( N = 629) and a comparative Spanish adolescent cohort ( N = 1502) were evaluated. The original two-factor version was the best fitting model for the Portuguese version. The reliability was excellent. Complete measurement invariance across both countries was supported. The Portuguese version of the Short Health Anxiety Inventory is a valid screening inventory to assess health anxiety in adolescents.
Orbital approach to the electronic structure of solids
Canadell, Enric; Iung, Christophe
2012-01-01
This book provides an intuitive yet sound understanding of how structure and properties of solids may be related. The natural link is provided by the band theory approach to the electronic structure of solids. The chemically insightful concept of orbital interaction and the essential machinery of band theory are used throughout the book to build links between the crystal and electronic structure of periodic systems. In such a way, it is shown how important tools for understandingproperties of solids like the density of states, the Fermi surface etc. can be qualitatively sketched and used to ei
Reliability estimation of structures under stochastic loading—A case study on nuclear piping
International Nuclear Information System (INIS)
Hari Prasad, M.; Rami Reddy, G.; Dubey, P.N.; Srividya, A.; Verma, A.K.
2013-01-01
Highlights: ► Structures are generally subjected to different types of loadings. ► One such type of loading is random sequence and has been treated as a stochastic fatigue loading. ► In this methodology both stress amplitude and number of cycles to failure have been considered as random variables. ► The methodology has been demonstrated with a case study on nuclear piping. ► The failure probability of piping has been estimated as a function of time. - Abstract: Generally structures are subjected to different types of loadings throughout their life time. These loads can be either discrete in nature or continuous in nature and also these can be either stationary or non stationary processes. This means that the structural reliability analysis not only considers random variables but also considers random variables which are functions of time, referred to as stochastic processes. A stochastic process can be viewed as a family of random variables. When a structure is subjected to a random loading, based on the stresses developed in the structure and failure criteria the failure probability can be estimated. In practice the structures are designed with higher factor of safety to take care of such random loads. In such cases the structure will fail only when the random loads are cyclic in nature. In traditional reliability analysis, the variation in the load is treated as a random variable and to account for the number of occurrences of the loading the concept of extreme value theory is used. But with this method one is neglecting the damage accumulation that will take place from one loading to another loading. Hence, in this paper, a new way of dealing with these types of problems has been discussed by using the concept of stochastic fatigue loading. The random loading has been considered as earthquake loading. The methodology has been demonstrated with a case study on nuclear power plant piping.
Buczyński, P.
2018-05-01
This article presents a new approach to reliability assessment of the road structure in which the base layer will be constructed in the process of cold deep recycling with foamed bitumen. In order to properly assess the reliability of the structure with the recycled base, it is necessary to determine the distribution of stress and strain in typical pavement layer systems. The true stress and strain values were established for particular structural layers using the complex modulus (E*) determined based on the master curves. The complex modulus was determined by the direct tension-compression test on cylindrical specimens (DTC-CY) at five temperatures (-7°C, 5°C, 13°C, 25°C, 40°C) and six loading times (0.1 Hz, 0.3 Hz, 1 Hz, 3 Hz, 10 Hz, 20 Hz) in accordance with EN 12697-26 in the linear viscoelasticity (LVE) range for small strains ranging from 25 to 50 με. The master curves of the complex modulus were constructed using the Richards model for the mixtures typically incorporated in structural layers, i.e., SMA11, AC16W, AC22P and MCAS. The values of the modulus characterizing particular layers were determined with temperature distribution in the structure taken into account, when the surface temperature was 40°C. The stress distribution was established for those calculation models. The stress values were used to evaluate the fatigue life under controlled stress conditions (IT-FT). This evaluation, with the controlled stress corresponding to that in the structure, facilitated the quality assessment of the rehabilitated recycled base course. Results showed that the recycled base mixtures having the indirect tensile strength (ITSDRY) similar to the stress in the structure under analysis needed an additional fatigue life evaluation in the indirect tensile test ITT. This approach to the recycled base quality assessment will allow eliminating the damage induced by overloading.
Design Considerations for Optimized Lateral Spring Structures for Wearable Electronics
Hussain, Aftab M.
2016-03-07
The market for wearable electronics has been gaining momentum in the recent years. For completely electronic wearable textiles with integrated sensors, actuators, computing units and communication circuitry, it is important that there is significant stretchability. This stretchability can be obtained by introducing periodic stretchable structures between the electronic circuits. In this work, we derive the equations and constraints governing the stretchability in horseshoe lateral spring structures. We have derived the optimum design and the parameters therein, to help develop the best spring structures for a given stretchability. We have also developed a figure of merit, called area efficiency of stretchability, to compare all twodimensional stretchable systems. Finally, we experimentally verify the validity of our equations by fabricating a metal/polymer bilayer thin film based stretchable horseshoe lateral spring structures. We obtain a stretchability of 1.875 which is comparable to the theoretical maxima of 2.01 for the given parameters.
Design Considerations for Optimized Lateral Spring Structures for Wearable Electronics
Hussain, Aftab M.; Hussain, Muhammad Mustafa
2016-01-01
The market for wearable electronics has been gaining momentum in the recent years. For completely electronic wearable textiles with integrated sensors, actuators, computing units and communication circuitry, it is important that there is significant stretchability. This stretchability can be obtained by introducing periodic stretchable structures between the electronic circuits. In this work, we derive the equations and constraints governing the stretchability in horseshoe lateral spring structures. We have derived the optimum design and the parameters therein, to help develop the best spring structures for a given stretchability. We have also developed a figure of merit, called area efficiency of stretchability, to compare all twodimensional stretchable systems. Finally, we experimentally verify the validity of our equations by fabricating a metal/polymer bilayer thin film based stretchable horseshoe lateral spring structures. We obtain a stretchability of 1.875 which is comparable to the theoretical maxima of 2.01 for the given parameters.
Studies on electronic structure of GaN(0001) surface
Xie Chang Kun; Xu Fa Qiang; Deng Rui; Liu Feng; Yibulaxin, K
2002-01-01
An electronic structure investigation on GaN(0001) is reported. The authors employ a full-potential linearized augmented plane-wave (FPLAPW) approach to calculate the partial density of state, which is in agreement with previous experimental results. The effects of the Ga3d semi-core levels on the electronic structure of GaN are discussed. The valence-electronic structure of the wurtzite GaN(0001) surface is investigated using synchrotron radiation excited angle-resolved photoemission spectroscopy. The bulk bands dispersion along GAMMA A direction in the Brillouin zones is measured using normal-emission spectra by changing photon-energy. The band structure derived from authors' experimental data is compared well with the results of authors' FPLAPW calculation. Furthermore, off-normal emission spectra are also measured along the GAMMA K and GAMMA M directions. Two surface states are identified, and their dispersions are characterized
Electronic structure of the high-temperature oxide superconductors
International Nuclear Information System (INIS)
Pickett, W.E.
1989-01-01
Since the discovery of superconductivity above 30 K by Bednorz and Mueller in the La copper oxide system, the critical temperature has been raised to 90 K in YBa 2 Cu 3 O 7 and to 110 and 125 K in Bi-based and Tl-based copper oxides, respectively. In the two years since this Nobel-prize-winning discovery, a large number of electronic structure calculations have been carried out as a first step in understanding the electronic properties of these materials. In this paper these calculations (mostly of the density-functional type) are gathered and reviewed, and their results are compared with the relevant experimental data. The picture that emerges is one in which the important electronic states are dominated by the copper d and oxygen p orbitals, with strong hybridization between them. Photon, electron, and positron spectroscopies provide important information about the electronic states, and comparison with electronic structure calculations indicates that, while many features can be interpreted in terms of existing calculations, self-energy corrections (''correlations'') are important for a more detailed understanding. The antiferromagnetism that occurs in some regions of the phase diagram poses a particularly challenging problem for any detailed theory. The study of structural stability, lattice dynamics, and electron-phonon coupling in the copper oxides is also discussed. Finally, a brief review is given of the attempts so far to identify interaction constants appropriate for a model Hamiltonian treatment of many-body interactions in these materials
Standardized structure of electronic records for information exchange
International Nuclear Information System (INIS)
Galabova, Sevdalina; Trencheva, Tereza; Trenchev, Ivan
2009-01-01
In the paper is presented the structure of the electronic record whose form is standardized in ISO 2709:2008. This International Standard describes a generalized structure, a framework designed specially for communications between data processing systems and not for use as a processing format within systems.Basic terms are defined as follows: character, data field, directory, directory map, field, field separator etc. It’s presented the general structure of a record. The application analysis of this structure shows the effective information exchange in the widest range.The purpose of this research is to find out advantages and structure of the information exchange format standardized in ISO 2709:2008. Key words: Standardized structure, electronic records, exchange formats, data field, directory, directory map, indicators, identifiers
STUDIES ON IGBT MODULE TO IMPROVE THE RELIABILITY OF POWER ELECTRONIC SYSTEMS
DEFF Research Database (Denmark)
Choi, Uimin
component level to converter level. It is divided into two main parts: the first part, which consists of Chapters 2 and 3, is reliability studies of the IGBT module regarding thermal stresses and the second part, composed of Chapters 4 and 5, discusses strategies to improve the reliability and availability...... are presented. Then, in Chapter 3, the effect of junction temperature swing duration t△Tj on the lifetime of the transfer molded Intelligent Power IGBT Module is investigated and modeled based on the power cycling test results. In addition, the physics-of-failure analysis results of the tested modules...... are presented. Finally, in Chapters 4 and 5, open-circuit fault detection and fault-tolerant control methods are proposed for two kinds of neutral-point clamped three-level inverters T-type and NPC inverters. One of main contributions in this project is the development of an apparatus and methodology...
Cooper, James A.
1986-01-01
A logic circuit is used to enhance redundant switch reliability. Two or more switches are monitored for logical high or low output. The output for the logic circuit produces a redundant and failsafe representation of the switch outputs. When both switch outputs are high, the output is high. Similarly, when both switch outputs are low, the logic circuit's output is low. When the output states of the two switches do not agree, the circuit resolves the conflict by memorizing the last output state which both switches were simultaneously in and produces the logical complement of this output state. Thus, the logic circuit of the present invention allows the redundant switches to be treated as if they were in parallel when the switches are open and as if they were in series when the switches are closed. A failsafe system having maximum reliability is thereby produced.
The stabilities and electron structures of Al-Mg clusters with 18 and 20 valence electrons
Yang, Huihui; Chen, Hongshan
2017-07-01
The spherical jellium model predicts that metal clusters having 18 and 20 valence electrons correspond to the magic numbers and will show specific stabilities. We explore in detail the geometric structures, stabilities and electronic structures of Al-Mg clusters containing 18 and 20 valence electrons by using genetic algorithm combined with density functional theories. The stabilities of the clusters are governed by the electronic configurations and Mg/Al ratios. The clusters with lower Mg/Al ratios are more stable. The molecular orbitals accord with the shell structures predicted by the jellium model but the 2S level interweaves with the 1D levels and the 2S and 1D orbitals form a subgroup. The clusters having 20 valence electrons form closed 1S21P61D102S2 shells and show enhanced stability. The Al-Mg clusters with a valence electron count of 18 do not form closed shells because one 1D orbital is unoccupied. The ionization potential and electron affinity are closely related to the electronic configurations; their values are determined by the subgroups the HOMO or LUMO belong to. Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjd/e2017-80042-9
Reliability technology principles and practice of failure prevention in electronic systems
Pascoe, Norman
2011-01-01
A unique book that describes the practical processes necessary to achieve failure free equipment performance, for quality and reliability engineers, design, manufacturing process and environmental test engineers. This book studies the essential requirements for successful product life cycle management. It identifies key contributors to failure in product life cycle management and particular emphasis is placed upon the importance of thorough Manufacturing Process Capability reviews for both in-house and outsourced manufacturing strategies. The readers? attention is also drawn to the ma
Halo Models of Large Scale Structure and Reliability of Cosmological N-Body Simulations
Directory of Open Access Journals (Sweden)
José Gaite
2013-05-01
Full Text Available Halo models of the large scale structure of the Universe are critically examined, focusing on the definition of halos as smooth distributions of cold dark matter. This definition is essentially based on the results of cosmological N-body simulations. By a careful analysis of the standard assumptions of halo models and N-body simulations and by taking into account previous studies of self-similarity of the cosmic web structure, we conclude that N-body cosmological simulations are not fully reliable in the range of scales where halos appear. Therefore, to have a consistent definition of halos is necessary either to define them as entities of arbitrary size with a grainy rather than smooth structure or to define their size in terms of small-scale baryonic physics.