Single-shell tank interim stabilization risk analysis
International Nuclear Information System (INIS)
Basche, A.D.
1998-01-01
The purpose of the Single-Shell Tank (SST) Interim Stabilization Risk Analysis is to provide a cost and schedule risk analysis of HNF-2358, Rev. 1, Single-Shell Tank Interim Stabilization Project Plan (Project Plan) (Ross et al. 1998). The analysis compares the required cost profile by fiscal year (Section 4.2) and revised schedule completion date (Section 4.5) to the Project Plan. The analysis also evaluates the executability of the Project Plan and recommends a path forward for risk mitigation
Comprehensive wellbore stability analysis utilizing Quantitative Risk Assessment
Energy Technology Data Exchange (ETDEWEB)
Moos, Daniel; Peska, Pavel; Finkbeiner, Thomas [GeoMechanics International, Palo Alto, CA 94303 (United States); Zoback, Mark [Stanford University, Stanford, CA 94305 (United States)
2003-06-01
A comprehensive geomechanical approach to wellbore stability requires knowledge of rock strength, pore pressure and the magnitude and orientation of the three principal stresses. These parameters are often uncertain, making confidence in deterministic predictions of the risks associated with instabilities during drilling and production difficult to assess. This paper demonstrates the use of Quantitative Risk Assessment (QRA) to formally account for the uncertainty in each input parameter to assess the probability of achieving a desired degree of wellbore stability at a given mud weight. We also utilize QRA to assess how the uncertainty in each parameter affects the mud weight calculated to maintain stability. In one case study, we illustrate how this approach allows us to compute optimal mud weight windows and casing set points at a deep-water site. In another case study, we demonstrate how to assess the feasibility of underbalanced drilling and open-hole completion of horizontal wells utilizing a comprehensive stability analysis that includes application of QRA.
Directory of Open Access Journals (Sweden)
Zhengqi He
2018-04-01
Full Text Available In China, large hydraulic engineering projects have made a great contribution to social economic development; at the same time, they also lead to social risks that affect social stability. The pluralism of stakeholders in large hydraulic engineering projects and the complex interrelationship among stakeholders are the important factors affecting social stability risk. Previous studies of social stability risk have mainly focused on risk identification and risk assessment, without considering the relationships among stakeholders and their linkages of risks. For large hydraulic engineering projects, this paper investigated the relevant risk factors and their interrelationships through a literature review and interviews that represented stakeholder perspectives. The key social stability risk factors were identified based on social network analysis. A multi-channel project financial system, a perfect interest compensation mechanism, an efficient prevention mechanism of group events, and a complete project schedule control system were proposed to mitigate the social stability risks. This study combined stakeholder management with risk management by using social network analysis, providing reference for the social stability risk management of large engineering projects in China.
RISKS AND CONSTRAINTS FOR THE MONETARY STABILITY
Directory of Open Access Journals (Sweden)
Camelia MILEA
2013-09-01
Full Text Available Starting from the definition according to which monetary stability requires an appropriate level of liquidity in an economy with dynamic objectives, of growth and job creation, non-inflationary in terms of price stability, based on the analysis of the effects of some relevant economic phenomena and on the economic literature, in this article, the author has highlighted some of the risks to monetary stability. One of the major risks is represented by the loss of its instruments, i.e. the instruments for liquidity management, through monetary and exchange rate policies. Another important risk is represented by the capital fluctuation due to various shocks: exchange rate, political, financial and capital account liberalization. Also, as a result of the analysis of relevant studies and of the effects of the European integration in terms of monetary stability, the author has shown the elements on which depends monetary stability. Among these, there are: the existence of an institutional framework with a clear goal and a proper degree of responsibility, strong operational independence of monetary policy, monetary policy implementation with a view to ensuring an appropriate balance between discipline and discretion, the level of the interest rate of monetary policy, the efficiency of the transmission mechanism of monetary policy, the existence of a viable and stable financial system, the existence of enough instruments at hand for the central bank, the structure and soundness of the financial and banking system. The paper is a capitalization of the research project “Global Risks for the Financial and Monetary Stability. Implications for Romania and European Union” elaborated in 2013, at “Victor Slăvescu” Centre for Financial and Monetary Research.
Containment vessel stability analysis
International Nuclear Information System (INIS)
Harstead, G.A.; Morris, N.F.; Unsal, A.I.
1983-01-01
The stability analysis for a steel containment shell is presented herein. The containment is a freestanding shell consisting of a vertical cylinder with a hemispherical dome. It is stiffened by large ring stiffeners and relatively small longitudinal stiffeners. The containment vessel is subjected to both static and dynamic loads which can cause buckling. These loads must be combined prior to their use in a stability analysis. The buckling loads were computed with the aid of the ASME Code case N-284 used in conjunction with general purpose computer codes and in-house programs. The equations contained in the Code case were used to compute the knockdown factors due to shell imperfections. After these knockdown factors were applied to the critical stress states determined by freezing the maximum dynamic stresses and combining them with other static stresses, a linear bifurcation analysis was carried out with the aid of the BOSOR4 program. Since the containment shell contained large penetrations, the Code case had to be supplemented by a local buckling analysis of the shell area surrounding the largest penetration. This analysis was carried out with the aid of the NASTRAN program. Although the factor of safety against buckling obtained in this analysis was satisfactory, it is claimed that the use of the Code case knockdown factors are unduly conservative when applied to the analysis of buckling around penetrations. (orig.)
International Nuclear Information System (INIS)
Baron, J.H.; Nunez McLeod, J.; Rivera, S.S.
1997-01-01
This book contains a selection of research works performed in the CEDIAC Institute (Cuyo National University) in the area of Risk Analysis, with specific orientations to the subjects of uncertainty and sensitivity studies, software reliability, severe accident modeling, etc. This volume presents important material for all those researches who want to have an insight in the risk analysis field, as a tool to solution several problems frequently found in the engineering and applied sciences field, as well as for the academic teachers who want to keep up to date, including the new developments and improvements continuously arising in this field [es
Active Risk Management and Banking Stability
Silva Buston, C.F.
2013-01-01
Abstract: This paper analyzes the net impact of two opposing effects of active risk management at banks on their stability: higher risk-taking incentives and better isolation of credit supply from varying economic conditions. We present a model where banks actively manage their portfolio risk by
TOOMPEA HILL STABILITY ANALYSIS
Pastarus, Jüri-Rivaldo
1997-01-01
On Toompea Hill situated in the center of Tallinn there are several natural, ancient architectural and historical monuments. It has become apparent that the processes in the rock mass caused an unfavorable environmental side effect accompanied by significant subsidence of the Toompea Hill. Identification of the reasons of the Toompea Hill's subsidence and opening the physical substance of these processes is the main aim of the present work. For the feasibility study stability problems were in...
Directory of Open Access Journals (Sweden)
Tri Handhika
2012-01-01
Full Text Available At any given time, market price of risk must be the same for all derivatives and it is linked in par-ticular to interest rate. The Brennan-Schwartz model is one of the stochastic differential equations for the interest rate under the risk neutral probability measure. To estimate parameters of this model, it is required that the real data which are collected in the real world in which the distribution of interest rate process is under the actual probability measure. Therefore, parameter estimators are obtained by changing the measure which is determined by the market price of risk. Hence, market price of risk must make the Brennan-Schwartz model becomes stable, which is important to describe resistance of the model to the perturbation in the initial state or parameters of the model. This paper aims to analyze the market price of risk from three major industrial countries: USA, Japan, and Canada. This analysis can be used as a guideline to decide that the interest rate of these three major industrial countries can be modeled as Brennan-Schwartz model. ";} // -->activate javascript
International Nuclear Information System (INIS)
Correa Lizarazu, X.
2013-01-01
The power point presentation Colombia risk evaluation experiences, sanitarian regulations evolution, chemical dangers food, biological dangers food, codex alimentarius, trade, industrial effects, dangers identification, data collection and risk profile
International Nuclear Information System (INIS)
Valtonen, K.
1990-01-01
The objective of this study has been to examine TVO-I oscillation incident, which occured in February 22.1987 and to find out safety implications of oscillations in ATWS incidents. Calculations have been performed with RAMONA-3B and TRAB codes. RAMONA-3B is a BWR transient analysis code with three-dimencional neutron kinetics and nonequilibrium, nonhomogeneous thermal hydraulics. TRAB code is a one-dimencional BWR transient code which uses methods similar to RAMONA-3B. The results have shown that both codes are capable of analyzing of the oscillation incidents. Both out-of-phase and in-phase oscillations are possible. If the reactor scram fails (ATWS) during oscillations the severe fuel failures are always possible and the reactor core may exceed the prompt criticality
Stability analysis of nonlinear systems
Lakshmikantham, Vangipuram; Martynyuk, Anatoly A
2015-01-01
The book investigates stability theory in terms of two different measure, exhibiting the advantage of employing families of Lyapunov functions and treats the theory of a variety of inequalities, clearly bringing out the underlying theme. It also demonstrates manifestations of the general Lyapunov method, showing how this technique can be adapted to various apparently diverse nonlinear problems. Furthermore it discusses the application of theoretical results to several different models chosen from real world phenomena, furnishing data that is particularly relevant for practitioners. Stability Analysis of Nonlinear Systems is an invaluable single-sourse reference for industrial and applied mathematicians, statisticians, engineers, researchers in the applied sciences, and graduate students studying differential equations.
PATRIMONIAL ANALYSIS OF FINANCIAL STABILITY
Directory of Open Access Journals (Sweden)
GABRIELA CORINA SLUSARIUC
2011-01-01
Full Text Available Patrimonial analysis of financial stability is realized with the help of some indicator determined on the balance: working capital; required working capital and net treasury. These indicators are determined and presented in evolution at two companies with different situations, and there are given conclusions and suggestions concerning achieving and maintaining the financial equilibrium or initiating corrective measures in time, before the imbalance would take irrecoverable forms.
Information security risk analysis
Peltier, Thomas R
2001-01-01
Effective Risk AnalysisQualitative Risk AnalysisValue AnalysisOther Qualitative MethodsFacilitated Risk Analysis Process (FRAP)Other Uses of Qualitative Risk AnalysisCase StudyAppendix A: QuestionnaireAppendix B: Facilitated Risk Analysis Process FormsAppendix C: Business Impact Analysis FormsAppendix D: Sample of ReportAppendix E: Threat DefinitionsAppendix F: Other Risk Analysis OpinionsIndex
Milanović, Jovica V
2017-08-13
Future power systems will be significantly different compared with their present states. They will be characterized by an unprecedented mix of a wide range of electricity generation and transmission technologies, as well as responsive and highly flexible demand and storage devices with significant temporal and spatial uncertainty. The importance of probabilistic approaches towards power system stability analysis, as a subsection of power system studies routinely carried out by power system operators, has been highlighted in previous research. However, it may not be feasible (or even possible) to accurately model all of the uncertainties that exist within a power system. This paper describes for the first time an integral approach to probabilistic stability analysis of power systems, including small and large angular stability and frequency stability. It provides guidance for handling uncertainties in power system stability studies and some illustrative examples of the most recent results of probabilistic stability analysis of uncertain power systems.This article is part of the themed issue 'Energy management: flexibility, risk and optimization'. © 2017 The Author(s).
Stability analysis of tokamak plasmas
International Nuclear Information System (INIS)
Bourdelle, C.
2000-10-01
In a tokamak plasma, the energy transport is mainly turbulent. In order to increase the fusion reactions rate, it is needed to improve the energy confinement. The present work is dedicated to the identification of the key parameters leading to plasmas with a better confined energy in order to guide the future experiments. For this purpose, a numerical code has been developed. It calculates the growth rates characterizing the instabilities onset. The stability analysis is completed by the evaluation of the shearing rate of the rotation due to the radial electric field. When this shearing rate is greater than the growth rate the ion turbulence is fully stabilised. The shearing rate and the growth rate are determined from the density, temperature and security factor profiles of a given plasma. Three types of plasmas have been analysed. In the Radiative Improved modes of TEXTOR, high charge number ions seeding lowers the growth rates. In Tore Supra-high density plasmas, a strong magnetic shear and/or a more efficient ion heating linked to a bifurcation of the toroidal rotation direction (which is not understood) trigger the improvement of the confinement. In other Tore Supra plasmas, locally steep electron pressure gradients have been obtained following magnetic shear reversal. This locally negative magnetic shear has a stabilizing effect. In these three families of plasmas, the growth rates decrease, the confinement improves, the density and temperature profiles are steeper. This steepening induces an increase of the rotation shearing rate, which then maintains the confinement high quality. (author)
Food risk analysis is a holistic approach to food safety because it considers all aspects of the problem. Risk assessment modeling is the foundation of food risk analysis. Proper design and simulation of the risk assessment model is important to properly predict and control risk. Because of knowl...
Optimal allosteric stabilization sites using contact stabilization analysis.
Dickson, Alex; Bailey, Christopher T; Karanicolas, John
2017-06-05
Proteins can be destabilized by a number of environmental factors such as temperature, pH, and mutation. The ability to subsequently restore function under these conditions by adding small molecule stabilizers, or by introducing disulfide bonds, would be a very powerful tool, but the physical principles that drive this stabilization are not well understood. The first problem lies is in choosing an appropriate binding site or disulfide bond location to best confer stability to the active site and restore function. Here, we present a general framework for predicting which allosteric binding sites correlate with stability in the active site. Using the Karanicolas-Brooks Gō-like model, we examine the dynamics of the enzyme β-glucuronidase using an Umbrella Sampling method to thoroughly sample the conformational landscape. Each intramolecular contact is assigned a score termed a "stabilization factor" that measures its correlation with structural changes in the active site. We have carried out this analysis for three different scaling strengths for the intramolecular contacts, and we examine how the calculated stabilization factors depend on the ensemble of destabilized conformations. We further examine a locally destabilized mutant of β-glucuronidase that has been characterized experimentally, and show that this brings about local changes in the stabilization factors. We find that the proximity to the active site is not sufficient to determine which contacts can confer active site stability. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
Aven, Terje
2012-01-01
Foundations of Risk Analysis presents the issues core to risk analysis - understanding what risk means, expressing risk, building risk models, addressing uncertainty, and applying probability models to real problems. The author provides the readers with the knowledge and basic thinking they require to successfully manage risk and uncertainty to support decision making. This updated edition reflects recent developments on risk and uncertainty concepts, representations and treatment. New material in Foundations of Risk Analysis includes:An up to date presentation of how to understand, define and
Stability Analysis of ISS Medications
Wotring, V. E.
2014-01-01
the United States Pharmacopeia (USP) to measure the amount of intact active ingredient, identify degradation products and measure their amounts. Some analyses were conducted by an independent analytical laboratory, but certain (Schedule) medications could not be shipped to their facility and were analyzed at JSC. RESULTS Nine medications were analyzed with respect to active pharmaceutical ingredient (API) and degradant amounts. Results were compared to the USP requirements for API and degradants/impurities content for every FDA-approved medication. One medication met USP requirements at 5 months after its expiration date. Four of the nine (44% of those tested) medications tested met USP requirements up to 8 months post-expiration. Another 3 medications (33% of those tested) met USP guidelines 2-3 months before expiration. One medication, a compound classed by the FDA as a dietary supplement and sometimes used as a sleep aid, failed to meet USP requirements at 11 months post-expiration. CONCLUSION Analysis of each medication at a single time point provides limited information on the stability of a medication stored in particular conditions; it is not possible to predict how long a medication may be safe and effective from these data. Notwithstanding, five of the nine medications tested (56%) met USP requirements for API and degradants/impurities at least 5 months past expiration dates. The single compound that failed to meet USP requirements is not regulated as strictly as prescription medications are during manufacture; it is unknown if this medication would have met the requirements prior to flight. Notably, it was the furthest beyond its expiration date. Only more comprehensive analysis of flight-aged samples compared to appropriate ground controls will permit determination of spaceflight effects on medication stability.
International Nuclear Information System (INIS)
Thompson, W.A. Jr.
1979-11-01
This paper briefly describes WASH 1400 and the Lewis report. It attempts to define basic concepts such as risk and risk analysis, common mode failure, and rare event. Several probabilistic models which go beyond the WASH 1400 methodology are introduced; the common characteristic of these models is that they recognize explicitly that risk analysis is time dependent whereas WASH 1400 takes a per demand failure rate approach which obscures the important fact that accidents are time related. Further, the presentation of a realistic risk analysis should recognize that there are various risks which compete with one another for the lives of the individuals at risk. A way of doing this is suggested
High beta and second stability region transport and stability analysis
International Nuclear Information System (INIS)
1990-01-01
This document summarizes progress made on the research of high beta and second region transport and stability. In the area second stability region studies we report on an investigation of the possibility of second region access in the center of TFTR ''supershots.'' The instabilities found may coincide with experimental observation. Significant progress has been made on the resistive stability properties of high beta poloidal ''supershot'' discharges. For these studies profiles were taken from the TRANSP transport analysis code which analyzes experimental data. Invoking flattening of the pressure profile on mode rational surfaces causes tearing modes to persist into the experimental range of interest. Further, the experimental observation of the modes seems to be consistent with the predictions of the MHD model. In addition, code development in several areas has proceeded
Univariate stability analysis methods for determining genotype ...
African Journals Online (AJOL)
Twenty two different stability statistics were used for analyzing genotype × environment (GE) interaction of durum wheat experimental data (20 genotypes in 15 environments). Combined analysis of variance indicated that GE interaction significantly influenced genotypes yield. According to type I stability concept, genotypes ...
Power system stability modelling, analysis and control
Sallam, Abdelhay A
2015-01-01
This book provides a comprehensive treatment of the subject from both a physical and mathematical perspective and covers a range of topics including modelling, computation of load flow in the transmission grid, stability analysis under both steady-state and disturbed conditions, and appropriate controls to enhance stability.
Stability analysis of rubblemound breakwater using ANN
Digital Repository Service at National Institute of Oceanography (India)
Mandal, S.; Rao, S.; Manjunath, Y.R.; Kim, D.H.
The stability analysis of coastal structure is very important because it involves many design parameters to be considered for the safe and economical design of structure. In the present study neural network technique is adopted to predict...
MHD stability analysis of helical system plasmas
International Nuclear Information System (INIS)
Nakamura, Yuji
2000-01-01
Several topics of the MHD stability studies in helical system plasmas are reviewed with respect to the linear and ideal modes mainly. Difference of the method of the MHD stability analysis in helical system plasmas from that in tokamak plasmas is emphasized. Lack of the cyclic (symmetric) coordinate makes an analysis more difficult. Recent topic about TAE modes in a helical system is also described briefly. (author)
Truck Roll Stability Data Collection and Analysis
Energy Technology Data Exchange (ETDEWEB)
Stevens, SS
2001-07-02
this database, instrumented vehicles would not need roadside beacons. The speed, acceleration, and roll stability of the vehicle could be determined prior to entering a curve, and a warning issued, if appropriate, for curves that have been characterized in the database. Thus, the analysis indicates that the data can be effectively used to provide a timely warning of rollover risk.
Jaya, A. I.; Lestari, A. D.; Ratianingsih, R.; Puspitasari, J. W.
2018-03-01
Obesity is found in 90% of the world's patients with a type 2 diabetes mellitus (DM) diagnosis. If it is not being treatment, the disease advances to a metabolic syndrome related to some atherosclerotic cardiovascular diseases. In this study, a mathematical model was constructed that represent the prognosis of type 2 DM. The prognosis is started from the transition of vulnerable people to overweight and obese. The advanced prognosis makes the type 2 DM sufferer become a metabolic syndrome. The model has no disease-free critical point, while the implicit endemic critical point is guaranteed for some requirements. The analysis of the critical point stability, by Jacobian matrix and Routh Hurwitz criteria, requires a parameter interval that identified from the characteristic polynomial. The requirements show that we have to pay attention to the transition rate of overweight to obese, more over the transition rate of obese to type 2 DM. The simulations show that the unstable condition of type 2 DM is easier to achieve because of the tightness of the parameter stability interval.
Risk analysis methodology survey
Batson, Robert G.
1987-01-01
NASA regulations require that formal risk analysis be performed on a program at each of several milestones as it moves toward full-scale development. Program risk analysis is discussed as a systems analysis approach, an iterative process (identification, assessment, management), and a collection of techniques. These techniques, which range from simple to complex network-based simulation were surveyed. A Program Risk Analysis Handbook was prepared in order to provide both analyst and manager with a guide for selection of the most appropriate technique.
Abandoned metal mine stability risk evaluation.
Bétournay, Marc C
2009-10-01
The abandoned mine legacy is critical in many countries around the world, where mine cave-ins and surface subsidence disruptions are perpetual risks that can affect the population, infrastructure, historical legacies, land use, and the environment. This article establishes abandoned metal mine failure risk evaluation approaches and quantification techniques based on the Canadian mining experience. These utilize clear geomechanics considerations such as failure mechanisms, which are dependent on well-defined rock mass parameters. Quantified risk is computed using probability of failure (probabilistics using limit-equilibrium factors of safety or applicable numerical modeling factor of safety quantifications) times a consequence impact value. Semi-quantified risk can be based on failure-case-study-based empirical data used in calculating probability of failure, and personal experience can provide qualified hazard and impact consequence assessments. The article provides outlines for land use and selection of remediation measures based on risk.
Stability Analysis of the Embankment Model
Directory of Open Access Journals (Sweden)
G.S. Gopalakrishna
2009-01-01
Full Text Available In analysis of embankment model affected by dynamic force, employment of shaking table is a scientific way in assessment of earthquake behavior. This work focused on saturated loose sandy foundation and enbankment. The results generated through the pore pressure sensors indicated pore water pressure playing main role in creation of liquefaction and stability of the system, and also revealed deformation, settlement, liquefaction intensity and time stability of system in direct correlation with the strength and characteristics of soil. One of the economical methods in stabilization of soil foundation is improvement of some part soil foundation.
Stability analysis of zigzag boron nitride nanoribbons
International Nuclear Information System (INIS)
Rai, Hari Mohan; Late, Ravikiran; Saxena, Shailendra K.; Kumar, Rajesh; Sagdeo, Pankaj R.; Jaiswal, Neeraj K.; Srivastava, Pankaj
2015-01-01
We have explored the structural stability of bare and hydrogenated zigzag boron nitride nanoribbons (ZBNNRs). In order to investigate the structural stability, we calculate the cohesive energy for bare, one-edge and both edges H-terminated ZBNNRs with different widths. It is found that the ZBNNRs with width Nz=8 are energetically more favorable than the lower-width counterparts (Nz<8). Bare ZBNNRs have been found energetically most stable as compared to the edge terminated ribbons. Our analysis reveals that the structural stability is a function of ribbon-width and it is not affected significantly by the type of edge-passivation (one-edge or both-edges)
Rock stability analysis – A case study
Directory of Open Access Journals (Sweden)
Lahmili A.
2018-01-01
Full Text Available The problems of the stability of the mineral-bearing structure ST2 at 560 m of depth in the east zone of Bou-azzer mine disturbs the advance of the exploitation. The geological and structural study based on field observations and the analysis of core drilling shows the presence of altered and fractured diorite surmounted by cobalt mineralization. Based on the empirical methods of Barton (Q-system and Bieniawski (RMR the bed rock is classified as poor quality. The analytical study made it possible to dimension supporting by bow-pieces and bolting. The existence of several types of discontinuities (fault, diaclases and joints has made the realization of numerical simulation by the finite elements method very difficult. These discontinuities create a network of natural fractures which cut out the blocks in various forms likely to be detached or slip into the excavation, thus encouraging the infiltration of water creating pressure on the massif. The classical studies show their limits in practice for installation of supporting because they must take into account the characteristics of discontinuities. Hence a structural analysis of the massif is essential. The cracking survey of ST2 at 560 m of depth in the east zone of Bou-azzer mine at 560m of depth, and their processing by the DIPS software, showed the existence of three main families of discontinuity NW-SE with a dip of 75SW, NS subverticale and NE-SW with a dip of 57NW, and two families of minor joints NW-SE and NE-SW with successive dips of 40SW and 75SE. The analysis of fracturing surveys allowed us to evaluate the risks of falling blocks and the families of discontinuity responsible for them, and to limit the zones presenting a risk of slip and the families responsible for them. The importance of this study is of knowing how and where to put supporting to be opposed to the risk of fall and tilting of the blocks, caused by the network of discontinuities of the massif.
Oxidation stability and risk evaluation of biodiesel
Directory of Open Access Journals (Sweden)
Hoshino Takashi
2007-01-01
Full Text Available This review describes oxidation and thermal stability and hazardous possibility of biodiesel by auto-oxidation. As it can be distributed using today’s infrastructure biodisel production has increased especially in the European Union. Biodiesel has many surpassing properties as an automotive fuel. Biodiesel is considered safer than diesel fuel because of the high flash point, but it has oxygen and double bond(s. Fatty acid methyl esters are more sensitive to oxidative degradation than fossil diesel fuel. The ability of producing peroxides is rather high, therefore we should care of handling of biodiesel.
Information Security Risk Analysis
Peltier, Thomas R
2010-01-01
Offers readers with the knowledge and the skill-set needed to achieve a highly effective risk analysis assessment. This title demonstrates how to identify threats and then determine if those threats pose a real risk. It is suitable for industry and academia professionals.
1996-06-01
Risk analysis plays a key role in the implementation of an architecture. Early definition of the situations, : processes, or events that have the potential for impeding the implementation of key elements of the ITS : National Architecture is a critic...
Linear stability analysis of heated parallel channels
International Nuclear Information System (INIS)
Nourbakhsh, H.P.; Isbin, H.S.
1982-01-01
An analyis is presented of thermal hydraulic stability of flow in parallel channels covering the range from inlet subcooling to exit superheat. The model is based on a one-dimensional drift velocity formulation of the two phase flow conservation equations. The system of equations is linearized by assuming small disturbances about the steady state. The dynamic response of the system to an inlet flow perturbation is derived yielding the characteristic equation which predicts the onset of instabilities. A specific application is carried out for homogeneous and regional uniformly heated systems. The particular case of equal characteristic frequencies of two-phase and single phase vapor region is studied in detail. The D-partition method and the Mikhailov stability criterion are used for determining the marginal stability boundary. Stability predictions from the present analysis are compared with the experimental data from the solar test facility. 8 references
Transient stability risk assessment of power systems incorporating wind farms
DEFF Research Database (Denmark)
Miao, Lu; Fang, Jiakun; Wen, Jinyu
2013-01-01
Large-scale wind farm integration has brought several aspects of challenges to the transient stability of power systems. This paper focuses on the research of the transient stability of power systems incorporating with wind farms by utilizing risk assessment methods. The detailed model of double...... fed induction generator has been established. Wind penetration variation and multiple stochastic factors of power systems have been considered. The process of transient stability risk assessment based on the Monte Carlo method has been described and a comprehensive risk indicator has been proposed....... An investigation has been conducted into an improved 10-generator 39-bus system with a wind farm incorporated to verify the validity and feasibility of the risk assessment method proposed....
Component of the risk analysis
International Nuclear Information System (INIS)
Martinez, I.; Campon, G.
2013-01-01
The power point presentation reviews issues like analysis of risk (Codex), management risk, preliminary activities manager, relationship between government and industries, microbiological danger and communication of risk
Habitat stability, predation risk and 'memory syndromes'.
Dalesman, S; Rendle, A; Dall, S R X
2015-05-27
Habitat stability and predation pressure are thought to be major drivers in the evolutionary maintenance of behavioural syndromes, with trait covariance only occurring within specific habitats. However, animals also exhibit behavioural plasticity, often through memory formation. Memory formation across traits may be linked, with covariance in memory traits (memory syndromes) selected under particular environmental conditions. This study tests whether the pond snail, Lymnaea stagnalis, demonstrates consistency among memory traits ('memory syndrome') related to threat avoidance and foraging. We used eight populations originating from three different habitat types: i) laboratory populations (stable habitat, predator-free); ii) river populations (fairly stable habitat, fish predation); and iii) ditch populations (unstable habitat, invertebrate predation). At a population level, there was a negative relationship between memories related to threat avoidance and food selectivity, but no consistency within habitat type. At an individual level, covariance between memory traits was dependent on habitat. Laboratory populations showed no covariance among memory traits, whereas river populations showed a positive correlation between food memories, and ditch populations demonstrated a negative relationship between threat memory and food memories. Therefore, selection pressures among habitats appear to act independently on memory trait covariation at an individual level and the average response within a population.
Stability Analysis of Bulk Viscous Cosmology
Sharif, M.; Mumtaz, Saadia
2018-01-01
In this paper, we study phase space analysis of FRW universe model by taking a power-law model for bulk viscosity coefficient. An autonomous system of equations is developed by defining normalized dimensionless variables. We find corresponding critical points for di.erent values of the parameters to investigate stability of the system. It is found that the presence of power-law model of bulk viscosity appears as an e.ective ingredient to enhance the stability of the respective universe model.
Risk Analysis of Marine Structures
DEFF Research Database (Denmark)
Hansen, Peter Friis
1998-01-01
Basic concepts of risk analysis is introduced. Formulation and analysis of fault and event trees are treated.......Basic concepts of risk analysis is introduced. Formulation and analysis of fault and event trees are treated....
Benchmark risk analysis models
Ale BJM; Golbach GAM; Goos D; Ham K; Janssen LAM; Shield SR; LSO
2002-01-01
A so-called benchmark exercise was initiated in which the results of five sets of tools available in the Netherlands would be compared. In the benchmark exercise a quantified risk analysis was performed on a -hypothetical- non-existing hazardous establishment located on a randomly chosen location in
Stability analysis for three-plane wedges
Tharp, Thomas M.
Stability analysis for rock wedges bounded by three planar discontinuities is a time-consuming procedure usually carried out by stereographic projection. An algorithm is presented which identifies the behavior mode for wedges and calculates the factor of safety more accurately than is possible by graphical methods. The upper and lower hemisphere stereographic projections also are plotted. This is the standard presentation format and it allows a visual check of the influence of assumed geometries and friction angles.
Nonlinear physical systems spectral analysis, stability and bifurcations
Kirillov, Oleg N
2013-01-01
Bringing together 18 chapters written by leading experts in dynamical systems, operator theory, partial differential equations, and solid and fluid mechanics, this book presents state-of-the-art approaches to a wide spectrum of new and challenging stability problems.Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations focuses on problems of spectral analysis, stability and bifurcations arising in the nonlinear partial differential equations of modern physics. Bifurcations and stability of solitary waves, geometrical optics stability analysis in hydro- and magnetohydrodynam
Stability analysis in K-means clustering.
Steinley, Douglas
2008-11-01
This paper develops a new procedure, called stability analysis, for K-means clustering. Instead of ignoring local optima and only considering the best solution found, this procedure takes advantage of additional information from a K-means cluster analysis. The information from the locally optimal solutions is collected in an object by object co-occurrence matrix. The co-occurrence matrix is clustered and subsequently reordered by a steepest ascent quadratic assignment procedure to aid visual interpretation of the multidimensional cluster structure. Subsequently, measures are developed to determine the overall structure of a data set, the number of clusters and the multidimensional relationships between the clusters.
Nonlinear stability analysis of the frame structures
Directory of Open Access Journals (Sweden)
Ćorić Stanko
2016-01-01
Full Text Available In this paper the phenomenon of instability of frames in elasto-plastic domain was investigated. Numerical analysis was performed by the finite element method. Stiffness matrices were derived using the trigonometric shape functions related to exact solution of the differential equation of bending according to the second order theory. When the buckling of structure occurs in plastic domain, it is necessary to replace the constant modulus of elasticity E with the tangent modulus Et. Tangent modulus is stress dependent function and takes into account the changes of the member stiffness in the inelastic range. For the purposes of numerical investigation in this analysis, part of the computer program ALIN was created in a way that this program now can be used for elastic and elasto-plastic stability analysis of frame structures. This program is developed in the C++ programming language. Using this program, it is possible to calculate the critical load of frames in the elastic and inelastic domain. In this analysis, the algorithm for the calculation of buckling lengths of compressed columns of the frames was also established. The algorithm is based on the calculation of the global stability analysis of frame structures. Results obtained using this algorithm were compared with the approximate solutions from the European (EC3 and national (JUS standards for the steel structures. By the given procedure in this paper it is possible to follow the behavior of the plane frames in plastic domain and to calculate the real critical load in that domain.
Stability Analysis Method of Parallel Inverter
Directory of Open Access Journals (Sweden)
Jun Li
2017-01-01
Full Text Available In order to further provide theoretical support for the stability of an auxiliary inverter parallel system, a new model which covers most of control parameters needs to be established. However, the ability of the small-signal model established by the traditional method is extremely limited, so this paper proposes a new small-signal modeling method for the parallel system. The new small-signal model not only can analyze the influence of the droop parameters on the system performance, but also can analyze the influence of the output impedance of the inverter, the unbalanced and nonlinear loads, and the power calculation method and cut-off frequency of the low-pass filter on the system performance and stability. Based on this method, this paper carries out a comprehensive analysis on the performance of a parallel inverter system. And the correctness of the modeling method and analysis process of the system performance and stability are verified by the consistency of the simulation and experimental results.
International Nuclear Information System (INIS)
Uppuluri, V.R.R.
1979-01-01
Mathematical foundations of risk analysis are addressed. The importance of having the same probability space in order to compare different experiments is pointed out. Then the following topics are discussed: consequences as random variables with infinite expectations; the phenomenon of rare events; series-parallel systems and different kinds of randomness that could be imposed on such systems; and the problem of consensus of estimates of expert opinion
Stability Analysis and Stabilization of Miduk Heap Leaching Structure, Iran
Directory of Open Access Journals (Sweden)
Mehdi Amini
2013-06-01
Full Text Available To construct copper heap leaching structures, a stepped heap of ore is placed over an isolated sloping surface and then washed with sulphuric acid. The isolated bed of such a heap consists of some natural and geosynthetic layers. Shear strength parameters between these layers are low, so they form the possible sliding surfaces of the heaps. Economic and environmental considerations call for studying such slides. In this study, firstly, results of the laboratory tests carried on the materials of the heap leaching structures bed are presented. Then, the instability mechanisms of such structures are investigated and proper approaches are summarized for their stabilization. Finally, stability of the Miduk copper heap is evaluated as a case history, and appropriate approaches and their effects are discussed for its stabilization.
The stability of bank efficiency rankings when risk preferences and objectives are different
Koetter, M.
2008-01-01
We analyze the stability of efficiency rankings of German universal banks between 1993 and 2004. First, we estimate traditional efficiency scores with stochastic cost and alternative profit frontier analysis. Then, we explicitly allow for different risk preferences and measure efficiency with a
Airfoil stall interpreted through linear stability analysis
Busquet, Denis; Juniper, Matthew; Richez, Francois; Marquet, Olivier; Sipp, Denis
2017-11-01
Although airfoil stall has been widely investigated, the origin of this phenomenon, which manifests as a sudden drop of lift, is still not clearly understood. In the specific case of static stall, multiple steady solutions have been identified experimentally and numerically around the stall angle. We are interested here in investigating the stability of these steady solutions so as to first model and then control the dynamics. The study is performed on a 2D helicopter blade airfoil OA209 at low Mach number, M 0.2 and high Reynolds number, Re 1.8 ×106 . Steady RANS computation using a Spalart-Allmaras model is coupled with continuation methods (pseudo-arclength and Newton's method) to obtain steady states for several angles of incidence. The results show one upper branch (high lift), one lower branch (low lift) connected by a middle branch, characterizing an hysteresis phenomenon. A linear stability analysis performed around these equilibrium states highlights a mode responsible for stall, which starts with a low frequency oscillation. A bifurcation scenario is deduced from the behaviour of this mode. To shed light on the nonlinear behavior, a low order nonlinear model is created with the same linear stability behavior as that observed for that airfoil.
Stability analysis of intershaft squeeze film dampers
El-Shafei, A.
1991-08-01
Intershaft squeeze film dampers have been investigated for damping of dual rotor aircraft jet engines. Initial investigations indicated that the intershaft dampers would attenuate the amplitude of the engine vibration and decrease the force transmitted through the intershaft bearing, thereby increasing its life. Also it was thought that the intershaft damper would enhance the stability of the rotor-bearing system. Unfortunately, it was determined both theoretically and experimentally that the intershaft squeeze film damper was unstable above the engine's first critical speed. In this paper, a stability analysis of rotors incorporating intershaft squeeze film dampers is performed. A rotor model consisting of two Jeffcott rotors with two intershaft squeeze film dampers is investigated. Examining the system characteristic equation for the conditions at which the roots indicate an ever growing unstable motion results in the stability conditions. The cause of the instability is identified as the rotation of the oil in the damper clearance. The oil rotation adds energy to the forward whirl of the rotor system above the critical speed and thus causes the instability. Below the critical speed the oil film removes energy from the forward rotor whirl. It is also shown that the backward whirl of the rotor system is always stable. Several proposed configurations of intershaft squeeze film dampers are discussed, and it is shown that the intershaft dampers are stable supercritically only with a configuration in which the oil film does not rotate.
Stability analysis of cylindrical Vlasov equilibria
International Nuclear Information System (INIS)
Short, R.W.
1979-01-01
A general method of stability analysis is described which may be applied to a large class of such problems, namely those which are described dynamically by the Vlasov equation, and geometrically by cylindrical symmetry. The method is presented for the simple case of the Vlasov-Poisson (electrostatic) equations, and the results are applied to a calculation of the lower-hybrid-drift instability in a plasma with a rigid rotor distribution function. The method is extended to the full Vlasov-Maxwell (electromagnetic) equations. These results are applied to a calculation of the instability of the extraordinary electromagnetic mode in a relativistic E-layer interacting with a background plasma
Stability analysis of cylindrical Vlasov equilibria
International Nuclear Information System (INIS)
Short, R.W.
1979-01-01
A general method of stability analysis is described which may be applied to a large class of such problems, namely those which are described dynamically by the Vlasov equation, and geometrically by clindrical symmetry. The method is presented for the simple case of the Vlasov-Poisson (electrostatic) equations, and the results are applied to a calculation of the lower-hybrid-drift instability in a plasma with a rigid rotor distribution function. The method is extended to the full Vlasov-Maxwell (electromagnetic) equations. These results are applied to a calculation of the instability of the extraordinary electromagnetic mode in a relativistic E-layer interacting with a background plasma
Dynamic Analysis of Power System Voltage Stability.
Gebreselassie, Assefa
This thesis investigates the effects of loads and voltage regulators on the dynamic voltage stability of power systems. The analysis focuses on the interactions of machine flux dynamics with loads and voltage control devices. The results are based on eigenvalue analysis of the linearized models and time simulation of the nonlinear models, using models from the Power System Toolbox, a Matlab -based package for the simulation and small signal analysis of nonlinear power systems. The voltage stability analysis results are developed using a single machine single load system with typical machine and network parameters and the NPCC 10-machine system. Dynamic models for generators, exciters and loads are used. The generator is modeled with a pair of poles and one damper circuit in both the d-axis and the q-axis. Saturation effects are included in the model. The IEEE Type DC1 DC commutator exciter model is used for all the exciters. Five different types of loads: constant impedance, constant current, constant power, a first order induction motor model (slip model) and a third order induction motor model (slip-flux model) are considered. The modes of instability and the stability limits of the different representation of loads are examined for two different operating modes of the exciters. The first, when all the exciters are on automatic control and the second when some exciters are on manual control. Modal participation factors are used to determine the characteristics of the critical modes. The characteristics of the unstable modes are verified by performing time simulation of the nonlinear models. Oscillatory and non-oscillatory instabilities are experienced by load buses when all the exciters are on automatic control and some exciters are on manual control respectively, for loads which are predominantly constant power and induction motors. It is concluded that the mode of instability does not depend on the type of loads but on the operating condition of the exciters
Voltage stability analysis using a modified continuation load flow ...
African Journals Online (AJOL)
Abstract. This paper addresses the rising problem of identifying the voltage stability limits of load buses in a power system and how to optimally place capacitor banks for voltage stability improvement. This paper uses the concept of the continuation power flow analysis used in voltage stability analysis. It uses the modified ...
Risk Analysis in Investment Appraisal
Savvides, Savvakis C.
1994-01-01
This paper was prepared for the purpose of presenting the methodology and uses of the Monte Carlo simulation technique as applied in the evaluation of investment projects to analyse and assess risk. The first part of the paper highlights the importance of risk analysis in investment appraisal. The second part presents the various stages in the application of the risk analysis process. The third part examines the interpretation of the results generated by a risk analysis application including ...
Bounded Linear Stability Margin Analysis of Nonlinear Hybrid Adaptive Control
Nguyen, Nhan T.; Boskovic, Jovan D.
2008-01-01
This paper presents a bounded linear stability analysis for a hybrid adaptive control that blends both direct and indirect adaptive control. Stability and convergence of nonlinear adaptive control are analyzed using an approximate linear equivalent system. A stability margin analysis shows that a large adaptive gain can lead to a reduced phase margin. This method can enable metrics-driven adaptive control whereby the adaptive gain is adjusted to meet stability margin requirements.
Power System Transient Stability Analysis through a Homotopy Analysis Method
Energy Technology Data Exchange (ETDEWEB)
Wang, Shaobu; Du, Pengwei; Zhou, Ning
2014-04-01
As an important function of energy management systems (EMSs), online contingency analysis plays an important role in providing power system security warnings of instability. At present, N-1 contingency analysis still relies on time-consuming numerical integration. To save computational cost, the paper proposes a quasi-analytical method to evaluate transient stability through time domain periodic solutions’ frequency sensitivities against initial values. First, dynamic systems described in classical models are modified into damping free systems whose solutions are either periodic or expanded (non-convergent). Second, because the sensitivities experience sharp changes when periodic solutions vanish and turn into expanded solutions, transient stability is assessed using the sensitivity. Third, homotopy analysis is introduced to extract frequency information and evaluate the sensitivities only from initial values so that time consuming numerical integration is avoided. Finally, a simple case is presented to demonstrate application of the proposed method, and simulation results show that the proposed method is promising.
RISK ANALYSIS SERIES. PART ONE - WHY RISK ANALYSIS?
Iulian N. BUJOREANU
2012-01-01
The goal of this paper is to introduce the reader to the Risk Analysis Series to be developed in the pages of the Journal of Defense Resources Management. Risk analysis is of outmost importance in dealing with resource allocation and this is the reason the paper’s author started this series. Different views and approaches will be added during further discussion about risk analysis so that the reader develops a habit or skills of dealing with this intricate and challenging field.
International Conference on Risk Analysis
Oliveira, Teresa; Rigas, Alexandros; Gulati, Sneh
2015-01-01
This book covers the latest results in the field of risk analysis. Presented topics include probabilistic models in cancer research, models and methods in longevity, epidemiology of cancer risk, engineering reliability and economical risk problems. The contributions of this volume originate from the 5th International Conference on Risk Analysis (ICRA 5). The conference brought together researchers and practitioners working in the field of risk analysis in order to present new theoretical and computational methods with applications in biology, environmental sciences, public health, economics and finance.
Multidimensional Risk Analysis: MRISK
McCollum, Raymond; Brown, Douglas; O'Shea, Sarah Beth; Reith, William; Rabulan, Jennifer; Melrose, Graeme
2015-01-01
Multidimensional Risk (MRISK) calculates the combined multidimensional score using Mahalanobis distance. MRISK accounts for covariance between consequence dimensions, which de-conflicts the interdependencies of consequence dimensions, providing a clearer depiction of risks. Additionally, in the event the dimensions are not correlated, Mahalanobis distance reduces to Euclidean distance normalized by the variance and, therefore, represents the most flexible and optimal method to combine dimensions. MRISK is currently being used in NASA's Environmentally Responsible Aviation (ERA) project o assess risk and prioritize scarce resources.
Stability of fundamental couplings: A global analysis
Martins, C. J. A. P.; Pinho, A. M. M.
2017-01-01
Astrophysical tests of the stability of fundamental couplings are becoming an increasingly important probe of new physics. Motivated by the recent availability of new and stronger constraints we update previous works testing the consistency of measurements of the fine-structure constant α and the proton-to-electron mass ratio μ =mp/me (mostly obtained in the optical/ultraviolet) with combined measurements of α , μ and the proton gyromagnetic ratio gp (mostly in the radio band). We carry out a global analysis of all available data, including the 293 archival measurements of Webb et al. and 66 more recent dedicated measurements, and constraining both time and spatial variations. While nominally the full data sets show a slight statistical preference for variations of α and μ (at up to two standard deviations), we also find several inconsistencies between different subsets, likely due to hidden systematics and implying that these statistical preferences need to be taken with caution. The statistical evidence for a spatial dipole in the values of α is found at the 2.3 sigma level. Forthcoming studies with facilities such as ALMA and ESPRESSO should clarify these issues.
Effects of joint stabilizers on proprioception and stability: A systematic review and meta-analysis.
Ghai, Shashank; Driller, Matthew; Ghai, Ishan
2017-05-01
The current review and meta-analysis systematically investigated the effect of joint stabilizers on proprioception, postural stability, and neurological activity. Systematic identification of published literature was performed on online databases; Scopus, PEDro, SportDiscus, and EMBASE, followed by a critical PEDro methodological quality appraisal. Data from the studies were extracted and summarized in a tabular format. Of 2954 records, 50 studies, involving 1443 participants met our inclusion criteria. In the included studies, 60% of studies reported significant enhancements (p 0.05) and 21% of studies reported no effects of joint stabilizers on proprioception and/or postural stability. Meta-analysis of pooled studies demonstrated beneficial effects of joint stabilizers on the knee (95% CI: 0.35°-0.61°) and ankle (at 10: 0.1°-0.65°) joint proprioception, and negligible effects on postural stability (-0.28°-0.19°). The pooled evidence suggests that application of joint stabilizers enhances joint proprioception and stability by not merely altering the mechanical stability of the underlying musculoskeletal structures but by also causing subtle changes in cerebral haemodynamics and musculoskeletal activation. These findings support clinical implications of joint stabilizers as a prophylactic and rehabilitation measure in modern sports and rehabilitation settings. Copyright © 2016 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Helms, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2017-02-10
The US energy sector is vulnerable to multiple hazards including both natural disasters and malicious attacks from an intelligent adversary. The question that utility owners, operators and regulators face is how to prioritize their investments to mitigate the risks from a hazard that can have the most impact on the asset of interest. In order to be able to understand their risk landscape and develop a prioritized mitigation strategy, they must quantify risk in a consistent way across all hazards their asset is facing. Without being able to quantitatively measure risk, it is not possible to defensibly prioritize security investments or evaluate trade-offs between security and functionality. Development of a methodology that will consistently measure and quantify risk across different hazards is needed.
Jing, Wenjun; Zhao, Yan
2018-02-01
Stability is an important part of geotechnical engineering research. The operating experiences of underground storage caverns in salt rock all around the world show that the stability of the caverns is the key problem of safe operation. Currently, the combination of theoretical analysis and numerical simulation are the mainly adopts method of reserve stability analysis. This paper introduces the concept of risk into the stability analysis of underground geotechnical structure, and studies the instability of underground storage cavern in salt rock from the perspective of risk analysis. Firstly, the definition and classification of cavern instability risk is proposed, and the damage mechanism is analyzed from the mechanical angle. Then the main stability evaluating indicators of cavern instability risk are proposed, and an evaluation method of cavern instability risk is put forward. Finally, the established cavern instability risk assessment system is applied to the analysis and prediction of cavern instability risk after 30 years of operation in a proposed storage cavern group in the Huai’an salt mine. This research can provide a useful theoretical base for the safe operation and management of underground storage caverns in salt rock.
Random matrix theory filters in portfolio optimisation: A stability and risk assessment
Daly, J.; Crane, M.; Ruskin, H. J.
2008-07-01
Random matrix theory (RMT) filters, applied to covariance matrices of financial returns, have recently been shown to offer improvements to the optimisation of stock portfolios. This paper studies the effect of three RMT filters on the realised portfolio risk, and on the stability of the filtered covariance matrix, using bootstrap analysis and out-of-sample testing. We propose an extension to an existing RMT filter, (based on Krzanowski stability), which is observed to reduce risk and increase stability, when compared to other RMT filters tested. We also study a scheme for filtering the covariance matrix directly, as opposed to the standard method of filtering correlation, where the latter is found to lower the realised risk, on average, by up to 6.7%. We consider both equally and exponentially weighted covariance matrices in our analysis, and observe that the overall best method out-of-sample was that of the exponentially weighted covariance, with our Krzanowski stability-based filter applied to the correlation matrix. We also find that the optimal out-of-sample decay factors, for both filtered and unfiltered forecasts, were higher than those suggested by Riskmetrics [J.P. Morgan, Reuters, Riskmetrics technical document, Technical Report, 1996. http://www.riskmetrics.com/techdoc.html], with those for the latter approaching a value of α=1. In conclusion, RMT filtering reduced the realised risk, on average, and in the majority of cases when tested out-of-sample, but increased the realised risk on a marked number of individual days-in some cases more than doubling it.
International Nuclear Information System (INIS)
David, A.
1992-01-01
This paper reports that the oil industry has been an internationally based industry that has been heavily dependent on outside financing sources. Historically, financing came from investment houses that, in most cases, participated in the projects as equity investors. However, investment companies can no longer satisfy the capital requirements of the current high level of exploration and development activities. The current trend is to involve commercial banks on a purely lending basis. Commercial banks, by their nature, are risk averse. In the case of oil and gas exploration and production they are asked to take not only technical risk and price risk but geopolitical risk as well. Methods have been developed by commercial banks to reduce technical and price risks to point which enables them to be comfortable with a loan. However, geopolitical risks are more difficult to assess. The risk associated with many countries are the nationalization of the investment, new tax restrictions, restriction of currency movements, and/or revisions to the production sharing agreements
MATHEMATICAL RISK ANALYSIS: VIA NICHOLAS RISK MODEL AND BAYESIAN ANALYSIS
Directory of Open Access Journals (Sweden)
Anass BAYAGA
2010-07-01
Full Text Available The objective of this second part of a two-phased study was to explorethe predictive power of quantitative risk analysis (QRA method andprocess within Higher Education Institution (HEI. The method and process investigated the use impact analysis via Nicholas risk model and Bayesian analysis, with a sample of hundred (100 risk analysts in a historically black South African University in the greater Eastern Cape Province.The first findings supported and confirmed previous literature (KingIII report, 2009: Nicholas and Steyn, 2008: Stoney, 2007: COSA, 2004 that there was a direct relationship between risk factor, its likelihood and impact, certiris paribus. The second finding in relation to either controlling the likelihood or the impact of occurrence of risk (Nicholas risk model was that to have a brighter risk reward, it was important to control the likelihood ofoccurrence of risks as compared with its impact so to have a direct effect on entire University. On the Bayesian analysis, thus third finding, the impact of risk should be predicted along three aspects. These aspects included the human impact (decisions made, the property impact (students and infrastructural based and the business impact. Lastly, the study revealed that although in most business cases, where as business cycles considerably vary dependingon the industry and or the institution, this study revealed that, most impacts in HEI (University was within the period of one academic.The recommendation was that application of quantitative risk analysisshould be related to current legislative framework that affects HEI.
CAREM-25 Steam Generator Stability Analysis
International Nuclear Information System (INIS)
Rabiti, A.; Delmastro, D.
2003-01-01
In this work the stability of a once-through CAREM-25 steam generator is analyzed.A fix nodes numerical model, that allows the modelling of the liquid, two-phase and superheated steam zones, is implemented.This model was checked against a mobile finite elements model under saturated steam conditions at the channel exit and a good agreement was obtained.Finally the stability of a CAREM steam generator is studied and the range of in let restrictions that a assure the system stability is analyzed
Stability analysis of impulsive parabolic complex networks
International Nuclear Information System (INIS)
Wang Jinliang; Wu Huaining
2011-01-01
Highlights: → Two impulsive parabolic complex network models are proposed. → The global exponential stability of impulsive parabolic complex networks are considered. → The robust global exponential stability of impulsive parabolic complex networks are considered. - Abstract: In the present paper, two kinds of impulsive parabolic complex networks (IPCNs) are considered. In the first one, all nodes have the same time-varying delay. In the second one, different nodes have different time-varying delays. Using the Lyapunov functional method combined with the inequality techniques, some global exponential stability criteria are derived for the IPCNs. Furthermore, several robust global exponential stability conditions are proposed to take uncertainties in the parameters of the IPCNs into account. Finally, numerical simulations are presented to illustrate the effectiveness of the results obtained here.
Global stability analysis and control of leptospirosis
Directory of Open Access Journals (Sweden)
Okosun Kazeem Oare
2016-01-01
Full Text Available The aim of this paper is to investigate the effectiveness and cost-effectiveness of leptospirosis control measures, preventive vaccination and treatment of infective humans that may curtail the disease transmission. For this, a mathematical model for the transmission dynamics of the disease that includes preventive, vaccination, treatment of infective vectors and humans control measures are considered. Firstly, the constant control parameters’ case is analyzed, also calculate the basic reproduction number and investigate the existence and stability of equilibria. The threshold condition for disease-free equilibrium is found to be locally asymptotically stable and can only be achieved when the basic reproduction number is less than unity. The model is found to exhibit the existence of multiple endemic equilibria. Furthermore, to assess the relative impact of each of the constant control parameters measures the sensitivity index of the basic reproductive number to the model’s parameters are calculated. In the time-dependent constant control case, Pontryagin’s Maximum Principle is used to derive necessary conditions for the optimal control of the disease. The cost-effectiveness analysis is carried out by first of all using ANOVA to check on the mean costs. Then followed by Incremental Cost-Effectiveness Ratio (ICER for all the possible combinations of the disease control measures. Our results revealed that the most cost-effective strategy for the control of leptospirosis is the combination of the vaccination and treatment of infective livestocks. Though the combinations of all control measures is also effective, however, this strategy is not cost-effective and so too costly. Therefore, more efforts from policy makers on vaccination and treatment of infectives livestocks regime would go a long way to combat the disease epidemic.
RISK ANALYSIS SERIES. PART ONE - WHY RISK ANALYSIS?
Directory of Open Access Journals (Sweden)
Iulian N. BUJOREANU
2012-01-01
Full Text Available The goal of this paper is to introduce the reader to the Risk Analysis Series to be developed in the pages of the Journal of Defense Resources Management. Risk analysis is of outmost importance in dealing with resource allocation and this is the reason the paper’s author started this series. Different views and approaches will be added during further discussion about risk analysis so that the reader develops a habit or skills of dealing with this intricate and challenging field.
Stability Analysis for HIFiRE Experiments
Li, Fei; Choudhari, Meelan M.; Chang, Chau-Lyan; White, Jeffery A.; Kimmel, Roger; Adamczak, David; Borg, Matthew; Stanfield, Scott; Smith, Mark S.
2012-01-01
The HIFiRE-1 flight experiment provided a valuable database pertaining to boundary layer transition over a 7-degree half-angle, circular cone model from supersonic to hypersonic Mach numbers, and a range of Reynolds numbers and angles of attack. This paper reports selected findings from the ongoing computational analysis of the measured in-flight transition behavior. Transition during the ascent phase at nearly zero degree angle of attack is dominated by second mode instabilities except in the vicinity of the cone meridian where a roughness element was placed midway along the length of the cone. The growth of first mode instabilities is found to be weak at all trajectory points analyzed from the ascent phase. For times less than approximately 18.5 seconds into the flight, the peak amplification ratio for second mode disturbances is sufficiently small because of the lower Mach numbers at earlier times, so that the transition behavior inferred from the measurements is attributed to an unknown physical mechanism, potentially related to step discontinuities in surface height near the locations of a change in the surface material. Based on the time histories of temperature and/or heat flux at transducer locations within the aft portion of the cone, the onset of transition correlated with a linear N-factor, based on parabolized stability equations, of approximately 13.5. Due to the large angles of attack during the re-entry phase, crossflow instability may play a significant role in transition. Computations also indicate the presence of pronounced crossflow separation over a significant portion of the trajectory segment that is relevant to transition analysis. The transition behavior during this re-entry segment of HIFiRE-1 flight shares some common features with the predicted transition front along the elliptic cone shaped HIFiRE-5 flight article, which was designed to provide hypersonic transition data for a fully 3D geometric configuration. To compare and contrast the
Object Oriented Risk Analysis Workshop
Pons, M. Güell I.; Jaboyedoff, M.
2009-04-01
In the framework of the RISET Project (Interfaculty Network of Support to Education and Technology) an educational tool for introducing risk analysis has been developed. This workshop enables to carry a group of students (role-play game) through a step-by-step process of risk identification and quantification. The aim is to assess risk in a characteristic alpine village regarding natural hazards (rockfall, snow avalanche, flooding…) and is oriented to affected objects such as buildings, infrastructures... The workshop contains the following steps: 1.- Planning of the study and definition of stakeholders 2.- Hazard identification 3.- Risk analysis 4.- Risk assessment 5.- Proposition of mitigation measures 6- Risk management and cost-benefit analysis. During the process, information related to past events and useful concepts are provided in order to bring up discussion and decision making. The Risk Matrix and other graphical tools allow having a visual representation of the risk level and help to prioritize counter measures. At the end of the workshop, there is the possibility to compare the results between different groups and print out a summarizing report. This approach provides a rapid and comprehensible risk evaluation. The workshop is accessible from the internet and will be used for educational purposes at bachelor and master level as well as for external persons dealing with risk analysis.
Risk analysis: opening the process
International Nuclear Information System (INIS)
Hubert, Ph.; Mays, C.
1998-01-01
This conference on risk analysis took place in Paris, 11-14 october 1999. Over 200 paper where presented in the seven following sessions: perception; environment and health; persuasive risks; objects and products; personal and collective involvement; assessment and valuation; management. A rational approach to risk analysis has been developed in the three last decades. Techniques for risk assessment have been thoroughly enhanced, risk management approaches have been developed, decision making processes have been clarified, the social dimensions of risk perception and management have been investigated. Nevertheless this construction is being challenged by recent events which reveal how deficits in stakeholder involvement, openness and democratic procedures can undermine risk management actions. Indeed, the global process most components of risk analysis may be radically called into question. Food safety has lately been a prominent issue, but now debates appear, or old debates are revisited in the domains of public health, consumer products safety, waste management, environmental risks, nuclear installations, automobile safety and pollution. To meet the growing pressures for efficiency, openness, accountability, and multi-partner communication in risk analysis, institutional changes are underway in many European countries. However, the need for stakeholders to develop better insight into the process may lead to an evolution of all the components of risks analysis, even in its most (technical' steps. For stakeholders of different professional background, political projects, and responsibilities, risk identification procedures must be rendered understandable, quantitative risk assessment must be intelligible and accommodated in action proposals, ranging from countermeasures to educational programs to insurance mechanisms. Management formats must be open to local and political input and other types of operational feedback. (authors)
Stability analysis of spacecraft power systems
Halpin, S. M.; Grigsby, L. L.; Sheble, G. B.; Nelms, R. M.
1990-01-01
The problems in applying standard electric utility models, analyses, and algorithms to the study of the stability of spacecraft power conditioning and distribution systems are discussed. Both single-phase and three-phase systems are considered. Of particular concern are the load and generator models that are used in terrestrial power system studies, as well as the standard assumptions of load and topological balance that lead to the use of the positive sequence network. The standard assumptions regarding relative speeds of subsystem dynamic responses that are made in the classical transient stability algorithm, which forms the backbone of utility-based studies, are examined. The applicability of these assumptions to a spacecraft power system stability study is discussed in detail. In addition to the classical indirect method, the applicability of Liapunov's direct methods to the stability determination of spacecraft power systems is discussed. It is pointed out that while the proposed method uses a solution process similar to the classical algorithm, the models used for the sources, loads, and networks are, in general, more accurate. Some preliminary results are given for a linear-graph, state-variable-based modeling approach to the study of the stability of space-based power distribution networks.
Applying programmatic risk assessment to nuclear materials stabilization R and D planning
International Nuclear Information System (INIS)
Kenley, C.R.; Brown-van Hoozer, S.A.
1997-01-01
A systems engineering approach to programmatic risk assessment, derived from the aerospace industry, was applied to various stabilization technologies to assess their relative maturity and availability for use in stabilizing nuclear materials. The assessment provided valuable information for trading off available technologies and identified the at-risk technologies that will require close tracking by the Department of Energy (DOE) to mitigate programmatic risks
Carlson, T.J.; Jong, C.A.F. de; Dekeling, R.P.A.
2012-01-01
The workshop looked at the assessment of risk to aquatic animals exposed to anthropogenic sound. The discussion focused on marine mammals given the worldwide attention being paid to them at the present time, particularly in relationship to oil and gas exploration, ocean power, and increases in ship
A linear stability analysis of supercritical water reactors, (1). Thermal-hydraulic stability
International Nuclear Information System (INIS)
Tin Tin Yi; Koshizuka, Seiichi; Oka, Yoshiaki
2004-01-01
This paper summarizes the analysis results of the thermal-hydraulic stability of a high-temperature reactor cooled and moderated by supercritical-pressure light water (SCLWR-H). A linear stability analysis code in the frequency domain was developed to study the thermal-hydraulic stability of SCLWR-H at constant supercritical pressure. The analysis method is based on linearization by perturbation of numerically-discretized one-dimensional single-channel single-phase conservation equations. The effect of water rods on stability is considered. The thermal-hydraulic stability of SCLWR-H for full-power and partial-power normal operations was investigated by frequency domain method. Our analysis reveals that though SCLWR-H has low coolant flow rate and large density change in the core, the thermal-hydraulic stability can be maintained both at normal operation and during power raising phase of constant pressure startup by applying an orifice pressure drop coefficient an the inlet of the fuel assemblies. A parametric study was also carried out to determine the parameters affecting the stability. (author)
Stability analysis of automobile driver steering control
Allen, R. W.
1981-01-01
In steering an automobile, the driver must basically control the direction of the car's trajectory (heading angle) and the lateral deviation of the car relative to a delineated pathway. A previously published linear control model of driver steering behavior which is analyzed from a stability point of view is considered. A simple approximate expression for a stability parameter, phase margin, is derived in terms of various driver and vehicle control parameters, and boundaries for stability are discussed. A field test study is reviewed that includes the measurement of driver steering control parameters. Phase margins derived for a range of vehicle characteristics are found to be generally consistent with known adaptive properties of the human operator. The implications of these results are discussed in terms of driver adaptive behavior.
Linear stability analysis of supersonic axisymmetric jets
Directory of Open Access Journals (Sweden)
Zhenhua Wan
2014-01-01
Full Text Available Stabilities of supersonic jets are examined with different velocities, momentum thicknesses, and core temperatures. Amplification rates of instability waves at inlet are evaluated by linear stability theory (LST. It is found that increased velocity and core temperature would increase amplification rates substantially and such influence varies for different azimuthal wavenumbers. The most unstable modes in thin momentum thickness cases usually have higher frequencies and azimuthal wavenumbers. Mode switching is observed for low azimuthal wavenumbers, but it appears merely in high velocity cases. In addition, the results provided by linear parabolized stability equations show that the mean-flow divergence affects the spatial evolution of instability waves greatly. The most amplified instability waves globally are sometimes found to be different from that given by LST.
Stability analysis of artificial synthetic overweight elements
International Nuclear Information System (INIS)
Zhou Jian
1990-01-01
Stability of artificial synthetic overweight elements has been analysed theoretically using a diagram of nuclear stability. It is indicated that overweight nucleus can be synthesized only when a certain amount of neutrons participate simultaneously in the synthesis. The maximum number of protons in overweight elements is 1002. The proton number of 'extreme overweight' elements of which the neutron star is possibly composed is in the range from 326 to 1002. It is expected that the mass number of the stable overweight elements with proton number 114 is in the range from 299 to 315
An analysis for crack layer stability
Sehanobish, K.; Botsis, J.; Moet, A.; Chudnovsky, A.
1986-01-01
The problem of uncontrolled crack propagation and crack arrest is considered with respect to crack layer (CL) translational stability. CL propagation is determined by the difference between the energy release rate and the amount of energy required for material transformation, and necessary and sufficient conditions for CL instability are derived. CL propagation in polystyrene is studied for two cases. For the case of remotely applied fixed load fatigue, the sufficient condition of instability is shown to be met before the necessary condition, and the necessary condition controls the stability. For the fixed displacement case, neither of the instability conditions are met, and CL propagation remains stable, resulting in crack arrest.
Management of Risks to Financial Stability from the Perspective of a Central Bank
Directory of Open Access Journals (Sweden)
Gabriela Lățea
2016-11-01
Full Text Available This article investigates the main issues pertaining to a central bank’s concerns relative to financial stability, as seen from the perspective of risks, sources and key ways of action. At macroeconomic level, central banks need to identify and monitor the risk that market operators face payment default towards local entities (companies, households, government and/or foreign creditors. Moreover, central banks entrusted with supervisory and licensing tasks are also carefully examining the various risks threatening banks, be they credit risk, liquidity risk, market risk, or risks associated with exposure concentration and distribution. On financial markets, prices, profit margins, interest rates, net exposure to certain financial instruments must be monitored to be able to identify build - ups of risks, stress and significant drawbacks to its adequate functioning. Adding to these is the Contingent Claims Analysis (CCA1, which involves oversight and assessment of risks in various sectors as well as of the needs to counter them, by drawing on the real market data to identify the probability of default in one sector or another and the impact on other sectors in an integrated manner.
DEFF Research Database (Denmark)
Nauta, Maarten
In several countries quantitative microbiological risk assessments (QMRAs) have been performed for Campylobacter in chicken meat. The models constructed for this purpose provide a good example of the development of QMRA in general and illustrate the diversity of available methods. Despite...... the differences between the models, the most prominent conclusions of the QMRAs are similar. These conclusions for example relate to the large risk of highly contaminated meat products and the insignificance of contamination from Campylobacter positive flocks to negative flocks during slaughter and processing....... Nonetheless, there seems to be a discrepancy between model predictions and the accumulating microbiological data. For example, a recent study in the Netherlands showed that model predictions on the efficacy of “testing and scheduling” of broiler flocks as a control strategy, could not be confirmed...
Methods of stability analysis in nonlinear mechanics
International Nuclear Information System (INIS)
Warnock, R.L.; Ruth, R.D.; Gabella, W.; Ecklund, K.
1989-01-01
We review our recent work on methods to study stability in nonlinear mechanics, especially for the problems of particle accelerators, and compare our ideals to those of other authors. We emphasize methods that (1) show promise as practical design tools, (2) are effective when the nonlinearity is large, and (3) have a strong theoretical basis. 24 refs., 2 figs., 2 tabs
Genotypic stability and clustering analysis of confectionery ...
African Journals Online (AJOL)
Nine groundnut genotypes were evaluated in terminal moisture-stress areas of northeastern Ethiopia during 2005 and 2006 cropping seasons with the objective of analyzing genotypic stability and clustering of confectionery groundnut for seed and protein yield. The genotypes were evaluated on a plot size of 15 m2 at Kobo ...
Introduction of the risk analysis
International Nuclear Information System (INIS)
Campon, G.; Martinez, I.
2013-01-01
An introduction of risks analysis was given in the exposition which main issues were: food innocuousness, world, regional and national food context,change of paradigms, health definition, risk, codex, standardization, food chain role, trade agreement, codex alimentarius, food transmission diseases cost impact
Postural Stability Analysis with Inertial Measurement Units in Alzheimer's Disease
Directory of Open Access Journals (Sweden)
Miguel F. Gago
2014-01-01
Full Text Available Background: The cause of frequent falls in patients with Alzheimer's disease (AD is still not well understood. Nevertheless, balance control and sensory organization are known to be critical for moving safely and adapting to the environment. Methods: We evaluated postural stability in 20 AD patients (11 fallers and 9 nonfallers and 16 healthy controls with an inertial measurement unit (triaxial accelerometers and gyroscopes attached to the center of mass (COM in different balance conditions (Romberg on flat surface and frontward/backward-inclined surface, with or without visual suppression in a motor lab. Results: In AD patients, the group of fallers showed a different kinetic pattern of postural stability characterized by higher vulnerability to visual suppression, higher total/maximal displacement and a mediolateral/anteroposterior range of sway, and a consequent need for more corrections of COM pitch and roll angles. Conclusion: Further studies are needed to consolidate the normative values of the discriminatory kinetic variables with the potential of inclusion in a multifactorial analysis of the risk of falls. Nevertheless, these results highlight signs of impairment of central postural control in AD, which may require early therapeutic intervention.
Quantitative Hazard and Risk Analysis
Geza Tarnai; Balazs Saghi; Izabela Krbilova
2006-01-01
In this paper a quantitative method for hazard and risk analysis is discussed. The method was developed and introduced for the allocation of safety requirements to the functions of a railway signaling remote control system.
Angle Stability Analysis for Voltage-Controlled Converters
DEFF Research Database (Denmark)
Lin, Hengwei; Jia, Chenxi; Guerrero, Josep M.
2017-01-01
a criterion to analyze the quasi-steady angle stability and the direct current (DC) side stability for VSCs. The operating limit and the angle instability mechanism are revealed, which is generally applicable to the voltage-controlled converters. During the analysis, the influence of the parameters on angle...... stability is studied. Further, the difference on instability mechanism between power electronic converters and synchronous generators are explained in detail. Finally, experiment results with corrective actions verify the analysis.......Power electronics based voltage source converters (VSCs) keep increasing in modern electrical systems. As a branch of stability problems, angle stability is significant for an electrical system. Based on small disturbance analysis and time scale decomposition perspective, this paper proposes...
The impact of bank size and funding risk on bank stability
Directory of Open Access Journals (Sweden)
Michael Adusei
2015-12-01
Full Text Available Does bank size significantly explain the variations in bank stability? Does bank funding risk significantly impact bank stability? This paper addresses these two questions with data from the rural banking industry in Ghana. Controlling for credit risk, liquidity risk, diversification in the business model, profitability, inflation, financial structure and gross domestic product, the results suggest that an increase in the size of a rural bank results in an increase in its stability. The results also show that funding risk positively impacts bank stability. The positive relationship between size and bank stability has important repercussions for the current debate on whether or not to constrain bank size to insulate the financial system from future crisis. The positive relationship between funding risk and bank stability also has important implications for the current debate on funding of retail banks.
ANALYSIS OF THE TRANSIENT STABILITY LIMIT OF NIGERIA'S ...
African Journals Online (AJOL)
user
network engineers have to devise methodologies based on the dynamic stability analysis. This motivates the development of power system transient stability model presented herein. The developed model is thus applied to a specimen of the Nigeria's transmission power system, i.e. the Ikeja-West Sub-network. This choice ...
Performance and stability analysis of a photovoltaic power system
Merrill, W. C.; Blaha, R. J.; Pickrell, R. L.
1978-01-01
The performance and stability characteristics of a 10 kVA photovoltaic power system are studied using linear Bode analysis and a nonlinear analog simulation. Power conversion efficiencies, system stability, and system transient performance results are given for system operation at various levels of solar insolation. Additionally, system operation and the modeling of system components for the purpose of computer simulation are described.
Mathematical modelling and linear stability analysis of laser fusion cutting
International Nuclear Information System (INIS)
Hermanns, Torsten; Schulz, Wolfgang; Vossen, Georg; Thombansen, Ulrich
2016-01-01
A model for laser fusion cutting is presented and investigated by linear stability analysis in order to study the tendency for dynamic behavior and subsequent ripple formation. The result is a so called stability function that describes the correlation of the setting values of the process and the process’ amount of dynamic behavior.
Linear and nonlinear stability analysis, associated to experimental fast reactors
International Nuclear Information System (INIS)
Amorim, E.S. do; Moura Neto, C. de; Rosa, M.A.P.
1980-07-01
Phenomena associated to the physics of fast neutrons were analysed by linear and nonlinear Kinetics with arbitrary feedback. The theoretical foundations of linear kinetics and transfer functions aiming at the analysis of fast reactors stability, are established. These stability conditions were analitically proposed and investigated by digital and analogic programs. (E.G.) [pt
Genotype x environment interaction and stability analysis for yield ...
African Journals Online (AJOL)
etc
2015-05-06
May 6, 2015 ... Various stability indices were used to assess stability and genotype by environment performances. Combined analysis of variance (ANOVA) for yield .... Mean grain yield (kg/ha) of 17 Kabuli-type chickpea genotypes grown at five locations in Ethiopia. ... Performance trials have to be conducted in multiple.
Stability analysis for downflow in heated channels
International Nuclear Information System (INIS)
Sampaio, P.A.B. de.
1985-01-01
Stability and flow distribution are analysed for downflow in heated channels. It is shown that at low flow rates instabilities associated with the buoyancy forces may appear. A computer code in FORTRAN language to determine downflow distribution among n heated channels is presented. The model used to calculate downflow distribution and the onset of instability is compared with experiments performed in a test section with two parallel channels. (Author) [pt
Stability Analysis Method of Parallel Inverter
Li, Jun; Chen, Jie; Xue, Yaru; Qiu, Ruichang; Liu, Zhigang
2017-01-01
In order to further provide theoretical support for the stability of an auxiliary inverter parallel system, a new model which covers most of control parameters needs to be established. However, the ability of the small-signal model established by the traditional method is extremely limited, so this paper proposes a new small-signal modeling method for the parallel system. The new small-signal model not only can analyze the influence of the droop parameters on the system performance, but also ...
Aerodynamic analysis of seamless horizontal stabilizer
Nithya, S.; Kanimozhi, S.
2017-05-01
This project presents an investigative view into the concept of seamless aeroelastic wing and hingeless flexible trailing edge. Wings are designed to provide maximum lift and minimal drag and weight. But with conventional wings where rivets are used and the control surfaces are separately hinged, parasite drag comes into play. This project is about analysing a smooth seamless wing with hinge-less flexible trailing edge. This type of wing reduces the drag considerably and the hinge-less trailing edge leads to a minimal control demand and reduces the noise produced when the aircraft comes for landing. Seamless aeroelastic wing will function as an integrated one piece lifting and control surface. It has been designed to enhance a desirable wing camber for control by deflecting a hinge-less flexible trailing edge part instead of a traditional hinged control surface. This kind of flexible wing can be achieved either by a curved beam and disc actuation mechanism or by piezo-electric materials, whose shape change can be achieved by electricity. The intent of this project is to analyze the effects of introducing the concept of Seamless Wing to the horizontal stabilizer. While the removal of rivets and serrations that hinge the elevators to the stabilizer reduces the overall drag by a reasonable value, the overall concept of a control surface-less stabilizer where the maneuvers are done by deflecting the trailing edge offers better maneuverability.
Advances in power system modelling, control and stability analysis
Milano, Federico
2016-01-01
Advances in Power System Modelling, Control and Stability Analysis captures the variety of new methodologies and technologies that are changing the way modern electric power systems are modelled, simulated and operated.
SPECTRAL ANALYSIS OF GAS BEARING SYSTEMS FOR STABILITY STUDIES
latter case is given in terms of a herringbone-grooved journal bearing . This method of stability analysis is applicable to both thrust and journal bearings for both whirl and pneumatic-hammer instabilities.
Dynamics, stability analysis and quantization of β-Fermi–Pasta ...
Indian Academy of Sciences (India)
- action potential among ... linear and nonlinear forces and these give rise to a set of nonlinear coupled equations whose analytic ... Further, they also carried out stability analysis for these q-breathers by employing Floquet method [20]. Here ...
Rohmer, Jeremy; Verdel, Thierry
2017-04-01
Uncertainty analysis is an unavoidable task of stability analysis of any geotechnical systems. Such analysis usually relies on the safety factor SF (if SF is below some specified threshold), the failure is possible). The objective of the stability analysis is then to estimate the failure probability P for SF to be below the specified threshold. When dealing with uncertainties, two facets should be considered as outlined by several authors in the domain of geotechnics, namely "aleatoric uncertainty" (also named "randomness" or "intrinsic variability") and "epistemic uncertainty" (i.e. when facing "vague, incomplete or imprecise information" such as limited databases and observations or "imperfect" modelling). The benefits of separating both facets of uncertainty can be seen from a risk management perspective because: - Aleatoric uncertainty, being a property of the system under study, cannot be reduced. However, practical actions can be taken to circumvent the potentially dangerous effects of such variability; - Epistemic uncertainty, being due to the incomplete/imprecise nature of available information, can be reduced by e.g., increasing the number of tests (lab or in site survey), improving the measurement methods or evaluating calculation procedure with model tests, confronting more information sources (expert opinions, data from literature, etc.). Uncertainty treatment in stability analysis usually restricts to the probabilistic framework to represent both facets of uncertainty. Yet, in the domain of geo-hazard assessments (like landslides, mine pillar collapse, rockfalls, etc.), the validity of this approach can be debatable. In the present communication, we propose to review the major criticisms available in the literature against the systematic use of probability in situations of high degree of uncertainty. On this basis, the feasibility of using a more flexible uncertainty representation tool is then investigated, namely Possibility distributions (e
Debt Stabilization and Debt Mutualization in a Monetary Union with Endogenous Risk Premia
Engwerda, Jacob; van Aarle, B.; Weeren, A.J.T.M.
2015-01-01
In this paper we analyse debt stabilization in a monetary union that features endogenous risk premia. In particular, we analyse debt stabilization in two diametrically opposed regimes. In the first regime, the “national fiscal discipline regime”, financial markets impose sovereign risk premia based
Truck Roll Stability Data Collection and Analysis; TOPICAL
International Nuclear Information System (INIS)
Stevens, SS
2001-01-01
, instrumented vehicles would not need roadside beacons. The speed, acceleration, and roll stability of the vehicle could be determined prior to entering a curve, and a warning issued, if appropriate, for curves that have been characterized in the database. Thus, the analysis indicates that the data can be effectively used to provide a timely warning of rollover risk
Stability analysis and the stabilization of a class of discrete-time dynamic neural networks.
Patan, Krzysztof
2007-05-01
This paper deals with problems of stability and the stabilization of discrete-time neural networks. Neural structures under consideration belong to the class of the so-called locally recurrent globally feedforward networks. The single processing unit possesses dynamic behavior. It is realized by introducing into the neuron structure a linear dynamic system in the form of an infinite impulse response filter. In this way, a dynamic neural network is obtained. It is well known that the crucial problem with neural networks of the dynamic type is stability as well as stabilization in learning problems. The paper formulates stability conditions for the analyzed class of neural networks. Moreover, a stabilization problem is defined and solved as a constrained optimization task. In order to tackle this problem two methods are proposed. The first one is based on a gradient projection (GP) and the second one on a minimum distance projection (MDP). It is worth noting that these methods can be easily introduced into the existing learning algorithm as an additional step, and suitable convergence conditions can be developed for them. The efficiency and usefulness of the proposed approaches are justified by using a number of experiments including numerical complexity analysis, stabilization effectiveness, and the identification of an industrial process.
Lin, Wen-Juan; He, Yong; Zhang, Chuan-Ke; Wu, Min
2018-01-01
This paper is concerned with the stability analysis of neural networks with a time-varying delay. To assess system stability accurately, the conservatism reduction of stability criteria has attracted many efforts, among which estimating integral terms as exact as possible is a key issue. At first, this paper develops a new relaxed integral inequality to reduce the estimation gap of popular Wirtinger-based inequality (WBI). Then, for showing the advantages of the proposed inequality over several existing inequalities that also improve the WBI, four stability criteria are derived through different inequalities and the same Lyapunov-Krasovskii functional (LKF), and the conservatism comparison of them is analyzed theoretically. Moreover, an improved criterion is established by combining the proposed inequality and an augmented LKF with delay-product-type terms. Finally, several numerical examples are used to demonstrate the advantages of the proposed method.
Modeling, Stability Analysis and Active Stabilization of Multiple DC-Microgrids Clusters
DEFF Research Database (Denmark)
Shafiee, Qobad; Dragicevic, Tomislav; Vasquez, Juan Carlos
2014-01-01
. This model can be also used to synthesis and study dynamics of control loops in dc MGs and also dc MG clusters. An active stabilization method is proposed to be implemented as a dc active power filter (APF) inside the MGs in order to not only increase damping of dc MGs at the presence of CPLs but also......DC microgrids (MGs), as an alternative option, have attracted increasing interest in recent years due to many potential advantages as compare to the ac system. Stability of these systems can be an important issue under high penetration of load converters which behaves as constant power loads (CPLs......), and more especially during interconnection with other MGs, creating dc MG clusters. This paper develops a small signal model for dc MGs from the control point of view, in order to study stability analysis and investigate effects of CPLs and line impedances between the MGs on stability of these systems...
Risk Analysis in Road Tunnels – Most Important Risk Indicators
DEFF Research Database (Denmark)
Berchtold, Florian; Knaust, Christian; Thöns, Sebastian
2016-01-01
Methodologies on fire risk analysis in road tunnels consider numerous factors affecting risks (risk indicators) and express the results by risk measures. But only few comprehensive studies on effects of risk indicators on risk measures are available. For this reason, this study quantifies the eff...
Directory of Open Access Journals (Sweden)
O. Liubkina
2013-10-01
Full Text Available The article examines the current state and major imbalances in the financial market of Ukraine, which are the source of risk to the national economy and can significantly affect the monetary stability during the post-crisis period and the period of recession. Threats that are associated with peculiarities of the institutional structure of the financial market of Ukraine are analyzed, namely, on the one hand, the importance of banking institutions, and on the other – functional inadequacy of the banking systems in ensuring monetary and financial stability. The analysis shows that the weaknesses of the banking system have led to the accumulation of risks and structural misbalances in the Ukrainian economy which pose a danger to stability in the financial sector. Conclusions and measures are substantiated for the use of tools of monetary policy in order to strengthen monetary and financial stability. Among them are: the necessity of changes in the methodological tools of assessment of the financial stability and accumulation of systemic risk in the economy, measures to manage the inflation risk as the main internal risk for Ukraine, ways of enhancement of interaction between the banking system and the national economy through the interest rate benchmark.
Stability analysis of a heated channel cooled by supercritical water
International Nuclear Information System (INIS)
Magni, M. C.; Delmastro, D. F; Marcel, C. P
2009-01-01
A simple model to study thermal-hydraulic stability of a heated cannel under supercritical conditions is presented. Single cannel stability analysis for the SCWR (Supercritical Water Cooled Reactor) design was performed. The drastic change of fluid density in the reactor core of a SCWR may induce DWO (Density Wave Oscillations) similar to those observed in BWRs. Due to the similarities between subcritical and supercritical systems we may treat the supercritical fluid as a pseudo two-phase system. Thus, we may extend the modeling approach often used for boiling flow stability analysis to supercritical pressure operation conditions. The model developed in this work take into account three regions: a heavy fluid region, similar to an incompressible liquid; a zone where a heavy fluid and a light fluid coexist, similar to two-phase mixture; and a light fluid region which behaves like superheated steam. It was used the homogeneous equilibrium model (HEM) for the pseudo boiling zone, and the ideal gas model for the pseudo superheated steam zone. System stability maps were obtained using linear stability analysis in the frequency domain. Two possible instability mechanisms are observed: DWO and excursive Ledinegg instabilities. Also, a sensitivity analysis showed that frictions in pseudo superheated steam zone, together with acceleration effect, are the most destabilizing effects. On the other hand, frictions in pseudo liquid zone are the most important stabilizing effect. [es
Stability analysis of Centurion electric power system
Energy Technology Data Exchange (ETDEWEB)
Galu, Y.; Munda, J.L.; Jimoh, A.A. [Tshwane Univ. of Technology, Pretoria (South Africa)
2008-07-01
A Centurion electric power system was simulated. Data from a section of the Tshwane Municipality network in South Africa were used to evaluate the use of a power system stabilizer (PSS) and a flexible AC transmission system (FACTS) controller and a thyristor controlled series compensator (TCSC). The single-machine infinite bus (SMIB) power system model was used to validate the effectiveness of the systems under various disturbance scenarios. The system's synchronous generator was characterized as a higher order model. Thevenin's equivalent of the transmission network was used to reduce the single-machine infinite bus power system in relation to the reactance of the transformer, transmission line per circuit, and the impedance of the receiving end system. Three-phase faults were applied at the generator terminal busbar in order to evaluate the model's performance. The study demonstrated that use of the PSS and TCSC-based controllers provide an improved response in terms of both overshoot and settling time. 17 refs., 10 figs.
Solar Dynamic Power System Stability Analysis and Control
Momoh, James A.; Wang, Yanchun
1996-01-01
The objective of this research is to conduct dynamic analysis, control design, and control performance test of solar power system. Solar power system consists of generation system and distribution network system. A bench mark system is used in this research, which includes a generator with excitation system and governor, an ac/dc converter, six DDCU's and forty-eight loads. A detailed model is used for modeling generator. Excitation system is represented by a third order model. DDCU is represented by a seventh order system. The load is modeled by the combination of constant power and constant impedance. Eigen-analysis and eigen-sensitivity analysis are used for system dynamic analysis. The effects of excitation system, governor, ac/dc converter control, and the type of load on system stability are discussed. In order to improve system transient stability, nonlinear ac/dc converter control is introduced. The direct linearization method is used for control design. The dynamic analysis results show that these controls affect system stability in different ways. The parameter coordination of controllers are recommended based on the dynamic analysis. It is concluded from the present studies that system stability is improved by the coordination of control parameters and the nonlinear ac/dc converter control stabilize system oscillation caused by the load change and system fault efficiently.
Stability Analysis of Neural Networks-Based System Identification
Directory of Open Access Journals (Sweden)
Talel Korkobi
2008-01-01
Full Text Available This paper treats some problems related to nonlinear systems identification. A stability analysis neural network model for identifying nonlinear dynamic systems is presented. A constrained adaptive stable backpropagation updating law is presented and used in the proposed identification approach. The proposed backpropagation training algorithm is modified to obtain an adaptive learning rate guarantying convergence stability. The proposed learning rule is the backpropagation algorithm under the condition that the learning rate belongs to a specified range defining the stability domain. Satisfying such condition, unstable phenomena during the learning process are avoided. A Lyapunov analysis leads to the computation of the expression of a convenient adaptive learning rate verifying the convergence stability criteria. Finally, the elaborated training algorithm is applied in several simulations. The results confirm the effectiveness of the CSBP algorithm.
Linear stability analysis in a solid-propellant rocket motor
Energy Technology Data Exchange (ETDEWEB)
Kim, K.M.; Kang, K.T.; Yoon, J.K. [Agency for Defense Development, Taejon (Korea, Republic of)
1995-10-01
Combustion instability in solid-propellant rocket motors depends on the balance between acoustic energy gains and losses of the system. The objective of this paper is to demonstrate the capability of the program which predicts the standard longitudinal stability using acoustic modes based on linear stability analysis and T-burner test results of propellants. Commercial ANSYS 5.0A program can be used to calculate the acoustic characteristic of a rocket motor. The linear stability prediction was compared with the static firing test results of rocket motors. (author). 11 refs., 17 figs.
Climate Change, State Stability, and Political Risk in Africa
2016-09-30
and how climate change poses threats to stability in Africa, identified strategies to support accountable and effective governance in Africa, and...interviews, the CCAPS program seeks to identify where and how climate change could undermine state stability, to define strategies for building...269–81. v Lisa Friedman, “Which Nations Are Most Vulnerable to Climate Change ? The Daunting Politics of Choosing ,” 2010, http://www.nytimes.com/cwire
Linear modeling of rotorcraft for stability analysis and preliminary design
Wirth, Walter M.
1993-01-01
Approved for public release; distribution is unlimited. This thesis investigates linear state space modeling of single main rotor helicopters culminating in a computer program that can be used for 1) stability and control analysis for any single main rotor helicopter or 2) preliminary design of a helicopter. The trim solution for a flight condition is found, the aircraft is perturbed about the nominal point, and the stability and control derivatives are determined. State space models and ...
Stability analysis of linear switching systems with time delays
International Nuclear Information System (INIS)
Li Ping; Zhong Shouming; Cui Jinzhong
2009-01-01
The issue of stability analysis of linear switching system with discrete and distributed time delays is studied in this paper. An appropriate switching rule is applied to guarantee the stability of the whole switching system. Our results use a Riccati-type Lyapunov functional under a condition on the time delay. So, switching systems with mixed delays are developed. A numerical example is given to illustrate the effectiveness of our results.
Stability analysis for cellular neural networks with variable delays
International Nuclear Information System (INIS)
Zhang Qiang; Wei Xiaopeng; Xu Jin
2006-01-01
Some sufficient conditions for the global exponential stability of cellular neural networks with variable delay are obtained by means of a method based on delay differential inequality. The method, which does not make use of Lyapunov functionals, is simple and effective for the stability analysis of neural networks with delay. Some previously established results in the literature are shown to be special cases of the presented result
Risk Characterization uncertainties associated description, sensitivity analysis
International Nuclear Information System (INIS)
Carrillo, M.; Tovar, M.; Alvarez, J.; Arraez, M.; Hordziejewicz, I.; Loreto, I.
2013-01-01
The power point presentation is about risks to the estimated levels of exposure, uncertainty and variability in the analysis, sensitivity analysis, risks from exposure to multiple substances, formulation of guidelines for carcinogenic and genotoxic compounds and risk subpopulations
Non linear stability analysis of parallel channels with natural circulation
Energy Technology Data Exchange (ETDEWEB)
Mishra, Ashish Mani; Singh, Suneet, E-mail: suneet.singh@iitb.ac.in
2016-12-01
Highlights: • Nonlinear instabilities in natural circulation loop are studied. • Generalized Hopf points, Sub and Supercritical Hopf bifurcations are identified. • Bogdanov–Taken Point (BT Point) is observed by nonlinear stability analysis. • Effect of parameters on stability of system is studied. - Abstract: Linear stability analysis of two-phase flow in natural circulation loop is quite extensively studied by many researchers in past few years. It can be noted that linear stability analysis is limited to the small perturbations only. It is pointed out that such systems typically undergo Hopf bifurcation. If the Hopf bifurcation is subcritical, then for relatively large perturbation, the system has unstable limit cycles in the (linearly) stable region in the parameter space. Hence, linear stability analysis capturing only infinitesimally small perturbations is not sufficient. In this paper, bifurcation analysis is carried out to capture the non-linear instability of the dynamical system and both subcritical and supercritical bifurcations are observed. The regions in the parameter space for which subcritical and supercritical bifurcations exist are identified. These regions are verified by numerical simulation of the time-dependent, nonlinear ODEs for the selected points in the operating parameter space using MATLAB ODE solver.
Stability analysis of sandy slope considering anisotropy effect in ...
Indian Academy of Sciences (India)
1Faculty of Engineering, Azarbaijan Shahid Madani University, ... 2School of Civil Engineering, Iran University of Science and Technology, ..... material. 4.3 Stability analysis result. For each analysis case with specified geometrical configuration for slope, a wide range of slip surfaces are considered by establishing a grid of ...
Conceptual risk assessment framework for global change risk analysis SRP
CSIR Research Space (South Africa)
Elphinstone, CD
2007-12-01
Full Text Available This report is submitted as a deliverable of the SRP project Global Change Risk Analysis which aims at applying risk analysis as a unifying notion for quantifying and communicating threats to ecosystem services originating from global change...
Intelligent Adversary Risk Analysis: A Bioterrorism Risk Management Model (PREPRINT)
2009-02-20
Society for Risk Analysis, February 20, 2009 1. INTELLIGENT ADVERSARY RISK ANALISIS IS DIFFERENT THAN HAZARD RISK ANALYSIS Risk analysis has...future work and our conclusions. 1.1. Intelligent adversary risk analysis requires new approaches We believe that risk analysis of uncertain hazards...public panic and social disruption; and require special action for public health preparedness. B to Second highest priority agents include those
Stability Analysis for a Multi-Camera Photogrammetric System
Directory of Open Access Journals (Sweden)
Ayman Habib
2014-08-01
Full Text Available Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, and describes the existing methods for performing stability analysis for a single camera. The paper then points out the lack of coverage of stability analysis for multi-camera systems, suggests a modification of the collinearity model to be used for the calibration of an entire photogrammetric system, and proposes three methods for system stability analysis. The proposed methods explore the impact of the changes in interior orientation and relative orientation/mounting parameters on the reconstruction process. Rather than relying on ground truth in real datasets to check the system calibration stability, the proposed methods are simulation-based. Experiment results are shown, where a multi-camera photogrammetric system was calibrated three times, and stability analysis was performed on the system calibration parameters from the three sessions. The proposed simulation-based methods provided results that were compatible with a real-data based approach for evaluating the impact of changes in the system calibration parameters on the three-dimensional reconstruction.
Environmental modeling and health risk analysis (ACTS/RISK)
National Research Council Canada - National Science Library
Aral, M. M
2010-01-01
... presents a review of the topics of exposure and health risk analysis. The Analytical Contaminant Transport Analysis System (ACTS) and Health RISK Analysis (RISK) software tools are an integral part of the book and provide computational platforms for all the models discussed herein. The most recent versions of these two softwa...
Synthesized dynamic modeling and stability analysis of novel HVDC system
Energy Technology Data Exchange (ETDEWEB)
Xu Sun; Li Kong [Inst. of Electrical Engineering, CAS, BJ (China)
2008-07-01
At the present time, many projects large offshore wind power fields connecting to the grid adopt the novel HVDC technology. Voltage source converter structure and PWM modulation technology are used in the system and active power and reactive power can be controlled respectively, so it can ensure the excellent performance of the projects. It is very necessary to build its detailed dynamic model and analyze its stability to be the base for further research. In this paper, firstly, the switch function model is established as the base of further analysis. Secondly, the steady model, small signal model and high frequency dynamic model of novel HVDC based on state space average method are established respectively. Thirdly, the stability of the whole system is analyzed on the base of above models of the novel HVDC. Finally, the whole system is validated practically by simulation analysis to prove the validity of model and stability analysis. (orig.)
Probabilistic approaches for geotechnical site characterization and slope stability analysis
Cao, Zijun; Li, Dianqing
2017-01-01
This is the first book to revisit geotechnical site characterization from a probabilistic point of view and provide rational tools to probabilistically characterize geotechnical properties and underground stratigraphy using limited information obtained from a specific site. This book not only provides new probabilistic approaches for geotechnical site characterization and slope stability analysis, but also tackles the difficulties in practical implementation of these approaches. In addition, this book also develops efficient Monte Carlo simulation approaches for slope stability analysis and implements these approaches in a commonly available spreadsheet environment. These approaches and the software package are readily available to geotechnical practitioners and alleviate them from reliability computational algorithms. The readers will find useful information for a non-specialist to determine project-specific statistics of geotechnical properties and to perform probabilistic analysis of slope stability.
Static Voltage Stability Analysis by Using SVM and Neural Network
Directory of Open Access Journals (Sweden)
Mehdi Hajian
2013-01-01
Full Text Available Voltage stability is an important problem in power system networks. In this paper, in terms of static voltage stability, and application of Neural Networks (NN and Supported Vector Machine (SVM for estimating of voltage stability margin (VSM and predicting of voltage collapse has been investigated. This paper considers voltage stability in power system in two parts. The first part calculates static voltage stability margin by Radial Basis Function Neural Network (RBFNN. The advantage of the used method is high accuracy in online detecting the VSM. Whereas the second one, voltage collapse analysis of power system is performed by Probabilistic Neural Network (PNN and SVM. The obtained results in this paper indicate, that time and number of training samples of SVM, are less than NN. In this paper, a new model of training samples for detection system, using the normal distribution load curve at each load feeder, has been used. Voltage stability analysis is estimated by well-know L and VSM indexes. To demonstrate the validity of the proposed methods, IEEE 14 bus grid and the actual network of Yazd Province are used.
Stability Analysis of Nonuniform Rectangular Beams Using Homotopy Perturbation Method
Directory of Open Access Journals (Sweden)
Seval Pinarbasi
2012-01-01
Full Text Available The design of slender beams, that is, beams with large laterally unsupported lengths, is commonly controlled by stability limit states. Beam buckling, also called “lateral torsional buckling,” is different from column buckling in that a beam not only displaces laterally but also twists about its axis during buckling. The coupling between twist and lateral displacement makes stability analysis of beams more complex than that of columns. For this reason, most of the analytical studies in the literature on beam stability are concentrated on simple cases: uniform beams with ideal boundary conditions and simple loadings. This paper shows that complex beam stability problems, such as lateral torsional buckling of rectangular beams with variable cross-sections, can successfully be solved using homotopy perturbation method (HPM.
Global robust exponential stability analysis for interval recurrent neural networks
International Nuclear Information System (INIS)
Xu Shengyuan; Lam, James; Ho, Daniel W.C.; Zou Yun
2004-01-01
This Letter investigates the problem of robust global exponential stability analysis for interval recurrent neural networks (RNNs) via the linear matrix inequality (LMI) approach. The values of the time-invariant uncertain parameters are assumed to be bounded within given compact sets. An improved condition for the existence of a unique equilibrium point and its global exponential stability of RNNs with known parameters is proposed. Based on this, a sufficient condition for the global robust exponential stability for interval RNNs is obtained. Both of the conditions are expressed in terms of LMIs, which can be checked easily by various recently developed convex optimization algorithms. Examples are provided to demonstrate the reduced conservatism of the proposed exponential stability condition
Stability analysis of embedded nonlinear predictor neural generalized predictive controller
Directory of Open Access Journals (Sweden)
Hesham F. Abdel Ghaffar
2014-03-01
Full Text Available Nonlinear Predictor-Neural Generalized Predictive Controller (NGPC is one of the most advanced control techniques that are used with severe nonlinear processes. In this paper, a hybrid solution from NGPC and Internal Model Principle (IMP is implemented to stabilize nonlinear, non-minimum phase, variable dead time processes under high disturbance values over wide range of operation. Also, the superiority of NGPC over linear predictive controllers, like GPC, is proved for severe nonlinear processes over wide range of operation. The necessary conditions required to stabilize NGPC is derived using Lyapunov stability analysis for nonlinear processes. The NGPC stability conditions and improvement in disturbance suppression are verified by both simulation using Duffing’s nonlinear equation and real-time using continuous stirred tank reactor. Up to our knowledge, the paper offers the first hardware embedded Neural GPC which has been utilized to verify NGPC–IMP improvement in realtime.
Collision Risk Analysis for HSC
DEFF Research Database (Denmark)
Urban, Jesper; Pedersen, Preben Terndrup; Simonsen, Bo Cerup
1999-01-01
conventional ships. To reach a documented level of safety, it is therefore not possible directly to transfer experience with conventional ships. The purpose of this paper is to present new rational scientific tools to assess and quantify the collision risk associated with HSC transportation. The paper...... analysis tools to quantify the effect of the high speed have been available. Instead nearly all research on ship accidents has been devoted to analysis of the consequences of given accident scenarios. The proposed collision analysis includes an analysis which determines the probability of a collision...... for a HSC on a given route, an analysis of the released energy during a collision, analytical closed form solutions for the absorbed energy in the structure and finally an assessment of the overall structural crushing behaviour of the vessel, including the level of acceleration and the size of the crushing...
Power system small signal stability analysis and control
Mondal, Debasish; Sengupta, Aparajita
2014-01-01
Power System Small Signal Stability Analysis and Control presents a detailed analysis of the problem of severe outages due to the sustained growth of small signal oscillations in modern interconnected power systems. The ever-expanding nature of power systems and the rapid upgrade to smart grid technologies call for the implementation of robust and optimal controls. Power systems that are forced to operate close to their stability limit have resulted in the use of control devices by utility companies to improve the performance of the transmission system against commonly occurring power system
Credit Risk Evaluation : Modeling - Analysis - Management
Wehrspohn, Uwe
2002-01-01
An analysis and further development of the building blocks of modern credit risk management: -Definitions of default -Estimation of default probabilities -Exposures -Recovery Rates -Pricing -Concepts of portfolio dependence -Time horizons for risk calculations -Quantification of portfolio risk -Estimation of risk measures -Portfolio analysis and portfolio improvement -Evaluation and comparison of credit risk models -Analytic portfolio loss distributions The thesis contributes to the evaluatio...
International Nuclear Information System (INIS)
Amjady, Nima; Ansari, Mohammad Reza
2008-01-01
The introduction of liberalized electricity markets in many countries has resulted in more highly stressed power systems. On the other hand, operating points of a power system are acceptable in the feasible region, which is surrounded by the borders of different stabilities. Power system instability is critical for all participants of the electricity market. Determination of different stability margins can result in the optimum utilization of power system with minimum risk. This paper focuses on the small disturbance voltage stability, which is an important subset of the power system global stability. This kind of voltage stability is usually evaluated by static analysis tools such as continuation power flow, while it essentially has dynamic nature. Besides, a combination of linear and nonlinear analysis tools is required to correctly analyze it. In this paper, a hybrid evaluation method composed of static, dynamic, linear, and nonlinear analysis tools is proposed for this purpose. Effect of load scenario, generation pattern, branch and generator contingency on the small disturbance voltage stability are evaluated by the hybrid method. The test results are given for New England and IEEE68 bus test systems. (author)
Surficial Stability Analysis for Landslide Prediction
Cho, Sung Eun
2017-04-01
In Korea where rainfall of strong intensities is frequent, the depth of weathered residual soil is shallow in mountainous region. Therefore, full saturation of soil layer caused by the reaching of rainwater from the slope surface to impermeable bedrock is one of important causes of landslide. In this study, a shallow slope failure analysis method for slopes with shallow bedrock was developed to predict landslide based on one-dimensional Green-Ampt model. Constant intensities of rainfall were considered and shallow impermeable boundary condition was imposed on the Green-Ampt model to simulate the impermeable bedrock underlying the shallow weathered residual soil. The prediction results showed that the proposed method can be used to predict the landslide due to rainfall infiltration by efficiently considering the movement of the saturated region in the hillslope with shallow impermeable bedrock. Acknowledgements This research was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2012M3A2A1050981).
Command Process Modeling & Risk Analysis
Meshkat, Leila
2011-01-01
Commanding Errors may be caused by a variety of root causes. It's important to understand the relative significance of each of these causes for making institutional investment decisions. One of these causes is the lack of standardized processes and procedures for command and control. We mitigate this problem by building periodic tables and models corresponding to key functions within it. These models include simulation analysis and probabilistic risk assessment models.
Stability of risk attitudes and media coverage of economic news
Tausch, Franziska; Zumbuehl, Maria
2016-01-01
This paper investigates the impact of exogenous changes in individuals' perceived economic environment on their self-stated risk attitudes by exploiting changes in media coverage of economic news. We use information on risk attitudes from the German Socioeconomic Panel and combine it with data on the average daily frequency of economic news reports during the year and the month preceding the date of the risk attitude elicitation. Using fixed effects regressions we observe effects of both long...
International Nuclear Information System (INIS)
Additon, S.L.; Peregoy, W.L.; Foppe, T.L.
1999-01-01
Building 707 and its addition, Building 707A, were selected, after the production mission of Rocky Flats was terminated a few years ago, to stabilize many of the plutonium residues remaining at the site by 2002. The facility had undergone substantial safety improvements to its safety systems and conduct of operations for resumption of plutonium operations in the early 1990s and appeared ideally suited for this new mission to support accelerated Site closure. During development of a new authorization basis, a seismic evaluation was performed. This evaluation addressed an unanalyzed expansion joint and suspect connection details for the precast concrete tilt-up construction and concluded that the seismic capacity of the facility is less than half of that determined by previous analysis. Further, potential seismic interaction was identified between a collapsing Building 707 and the seismically upgraded Building 707A, possibly causing the partial collapse of the latter. Both the operating contractor and the Department of Energy sought a sound technical basis for deciding how to proceed. This paper addresses the risks of the as-is facility and possible benefits of upgrades to support a decision on whether to upgrade the seismic capacity of Building 707, accept the risk of the as-is facility for its short remaining mission, or relocate critical stabilization missions. The paper also addresses the Department of Energy's policy on natural phenomena
Pitching stability analysis of half-rotating wing air vehicle
Wang, Xiaoyi; Wu, Yang; Li, Qian; Li, Congmin; Qiu, Zhizhen
2017-06-01
Half-Rotating Wing (HRW) is a new power wing which had been developed by our work team using rotating-type flapping instead of oscillating-type flapping. Half-Rotating Wing Air Vehicle (HRWAV) is similar as Bionic Flapping Wing Air Vehicle (BFWAV). It is necessary to guarantee pitching stability of HRWAV to maintain flight stability. The working principle of HRW was firstly introduced in this paper. The rule of motion indicated that the fuselage of HRWAV without empennage would overturn forward as it generated increased pitching movement. Therefore, the empennage was added on the tail of HRWAV to balance the additional moment generated by aerodynamic force during flight. The stability analysis further shows that empennage could weaken rapidly the pitching disturbance on HRWAV and a new balance of fuselage could be achieved in a short time. Case study using numerical analysis verified correctness and validity of research results mentioned above, which could provide theoretical guidance to design and control HRWAV.
Stability Analysis for Compliant Constant-Force Compression Mechanisms
Directory of Open Access Journals (Sweden)
Ikechukwu Celestine UGWUOKE
2009-12-01
Full Text Available Stability analysis in compliant mechanism (CM design is of utmostimportance. From a practical point of view, a CM that is unstable is of nosignificance (has no practical value. Three useful plots were considered in theevaluation of each of the dynamic models of nine configurations of compliantconstant-force compression mechanisms (CCFCMs for their stabilitycharacteristics, which includes the polar plot based on the Routh-Hurwitzstability criterion, the Bode plot, and the Nyquist diagram which considersstability in the real frequency domain. Frequency-domain stability criterion isvery useful for determining suitable approaches to adjusting the CCFCMparameters in order to increase its relative stability. The results obtained showthat the CCFCMs investigated do exhibit higher relative stability for highervalues of damping ratio, and for zero damping ratio, all the CCFCMsinvestigated were unstable. The result also show that for the CCFCMsinvestigated to be stable, damping ratio must be greater than 0.03 (ξ > 0.03and depending on what attributes are most desirable, the CCFCM parameterscan be optimized to achieve the desired results. Nyquist criterion provides uswith suitable information concerning the absolute stability and furthermore,can be utilized to define and ascertain the relative stability of a system.
Applying programmatic risk assessment to nuclear materials stabilization R and D planning
International Nuclear Information System (INIS)
A systems engineering approach to programmatic risk assessment, derived from the aerospace industry, was applied to various stabilization technologies to assess their relative maturity and availability for use in stabilizing nuclear materials. The assessment provided valuable information for trading off available technologies and identified the at-risk technologies that will require close tracking by the Department of Energy (DOE) to mitigate programmatic risks. This paper presents the programmatic risk assessment methodology developed for the 1995 R and D Plan and updated for the 1996 R and D Plan. Results of the 1996 assessment also are presented (DOE/ID-10561, 1996)
Uncertainty in the process of risk analysis
International Nuclear Information System (INIS)
Lovecek, Tomas; Kampova, Katarina
2009-01-01
In the risk analysis we are often trying to describe and assess various quantities, which express the surrounding risk environment and in this way influence its existence and size. In connection with quantifying these risk factors we come across the problem of uncertainty, which rests in the fact that the values of these factors are unknown at the time of analysis and in this way they make the process of risk analysis complicated. In the presented article we deal with the interconnections of this uncertainly as well as with the possibilities of its interpretation and quantification in the risk analysis process. Key words: Risk, Risk Analysis, Uncertainty, Numerical Methods, Exact Methods
High beta and second stability region transport and stability analysis. Final report
Energy Technology Data Exchange (ETDEWEB)
Hughes, M.H.; Phillips, M.W.
1996-01-01
This report describes MHD equilibrium and stability studies carried out at Northrop Grumman`s Advanced Technology and Development Center during the period March 1 to December 31, 1995. Significant progress is reported in both ideal and resistive MHD modeling of TFTR plasmas. Specifically, attention is concentrated on analysis of Advanced Tokamak experiments at TFTR involving plasmas in which the q-profiles were non-monotonic.
Habitat stability, predation risk and ‘memory syndromes’
S. Dalesman; A. Rendle; S.R.X. Dall
2015-01-01
Habitat stability and predation pressure are thought to be major drivers in the evolutionary maintenance of behavioural syndromes, with trait covariance only occurring within specific habitats. However, animals also exhibit behavioural plasticity, often through memory formation. Memory formation across traits may be linked, with covariance in memory traits (memory syndromes) selected under particular environmental conditions. This study tests whether the pond snail, Lymnaea stagnalis, demonst...
Stability analysis of sandy slope considering anisotropy effect in ...
Indian Academy of Sciences (India)
This paper aims to investigate the effect of anisotropy of shear strength parameter on the stability of a sandy slope by performing the limit equilibrium analysis. Because of scarcity of mathematical equation for anisotropic friction angle of sand, at first, all results of principal stress rotation tests are processed by artificial neural ...
Stability Analysis of a Mathematical Model for Onchocerciaisis ...
African Journals Online (AJOL)
ADOWIE PERE
Stability Analysis of a Mathematical Model for Onchocerciaisis. 668. BAKO, DU; AKINWANDE, NI; ENAGI, AI; KUTA, FA; ABDULRAHMAN, S. Table 1: Values of Parameters of the model. S/N. Parameters. Value. Source. 1 ω. 0.019. Estimated. 2 h. Λ. 3,449,679. Estimated. 3 h. µ. 0.019. CIA 2016. 4. 1 α. 2.12. Shuaib 2015. 5.
Stabilization diagrams using operational modal analysis and sliding filters
DEFF Research Database (Denmark)
Olsen, Peter; Juul, Martin Ørum Ørhem; Tarpø, Marius Glindtvad
2017-01-01
This paper presents a filtering technique for doing effective operational modal analysis. The result of the filtering method is construction of stabilization diagram that clearly separates physical poles from spurious noise poles needed for unbiased fitting. A band pass filter is moved slowly over...
Yield evaluation and stability analysis in newly selected `KSA' cotton ...
African Journals Online (AJOL)
Yield evaluation and stability analysis in newly selected `KSA' cotton cultivars in Western Kenya. R M Opondo, G A Ombakho. Abstract. (African Crop Science Journal, 1997 5(2): 119-126). http://dx.doi.org/10.4314/acsj.v5i2.27854 · AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians ...
The analysis of Stability reliability of Qian Tang River seawall
Wu, Xue-Xiong
2017-11-01
Qiantang River seawall due to high water soaking pond by foreshore scour, encountered during the low tide prone slope overall instability. Considering the seawall beach scour in front of random change, using the simplified Bishop method, combined with the variability of soil mechanics parameters, calculation and analysis of Qiantang River Xiasha seawall segments of the overall stability.
Transient stability analysis of a distribution network with distributed generators
Xyngi, I.; Ishchenko, A.; Popov, M.; Van der Sluis, L.
2009-01-01
This letter describes the transient stability analysis of a 10-kV distribution network with wind generators, microturbines, and CHP plants. The network being modeled in Matlab/Simulink takes into account detailed dynamic models of the generators. Fault simulations at various locations are
Stability Analysis for Hybrid Automata Using Conservative Gains
Langerak, Romanus; Engell, S.; Guegen, H.; Polderman, Jan W.; Krilavicius, T.; Zaytoon, J.
2003-01-01
This paper presents a stability analysis approach for a class of hybrid automata. It is assumed that the dynamics in each location of the hybrid automaton is linear and asymptotically stable, and that the guards on the transitions are hyperplanes in the state space. For each pair of ingoing and
Stability Analysis of Static Slip-Energy Recovery Drive via ...
African Journals Online (AJOL)
A set of nonlinear differential equations which describe the system dynamics are derived and linearized about an operating point using perturbation technique. The Eigenvalue analysis of the linearized model shows that the drive system is almost completely stable in the entire operating range Routh stability criterion is used ...
Experimental bifurcation analysis of an impact oscillator – Determining stability
DEFF Research Database (Denmark)
Bureau, Emil; Schilder, Frank; Elmegård, Michael
2014-01-01
We propose and investigate three different methods for assessing stability of dynamical equilibrium states during experimental bifurcation analysis, using a control-based continuation method. The idea is to modify or turn off the control at an equilibrium state and study the resulting behavior...
Stability Analysis for Multi-Parameter Linear Periodic Systems
DEFF Research Database (Denmark)
Seyranian, A.P.; Solem, Frederik; Pedersen, Pauli
1999-01-01
This paper is devoted to stability analysis of general linear periodic systems depending on real parameters. The Floquet method and perturbation technique are the basis of the development. We start out with the first and higher-order derivatives of the Floquet matrix with respect to problem...
Stability analysis of the carbuncle phenomenon and the sonic point ...
Indian Academy of Sciences (India)
Aayush Agrawal
instability, we perform a thorough stability analysis and extend previous studies by analysing the pseudo-spectra and hence the ... viour in Riemann solvers and thus help in the design of better solvers for high-Reynolds-number flows. Keywords. ..... the domain and random perturbations being added to all flow variables.
Stability analysis for a general age-dependent vaccination model
International Nuclear Information System (INIS)
El Doma, M.
1995-05-01
An SIR epidemic model of a general age-dependent vaccination model is investigated when the fertility, mortality and removal rates depends on age. We give threshold criteria of the existence of equilibriums and perform stability analysis. Furthermore a critical vaccination coverage that is sufficient to eradicate the disease is determined. (author). 12 refs
analysis and correlation of stability parameters in malting barley
African Journals Online (AJOL)
Administrator
Interaction principal component axis (IPCA) scores,. Additive .... TABLE 1. Additive main effects and multiplicative interactions (AMMI) analysis of variance for grain yield of 20 genotypes of ... BLE 2. Mean grain yield and genotypic stability parameters for 20 malting barley genotypes grown over 12 environments in Ethiopia.
Yield stability analysis of pearl millet hybrids in Nigeria
African Journals Online (AJOL)
hope&shola
2006-02-02
Feb 2, 2006 ... years. Genotype x environment interaction was observed, a large component of which was accounted ... Table 1. The different environments, years, locations, total rainfall, latitudes and environmental means for grain yield average ... Table 2. Pooled analysis of variance for stability of grain yield (t/ha).
38 CFR 75.115 - Risk analysis.
2010-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 2 2010-07-01 2010-07-01 false Risk analysis. 75.115...) INFORMATION SECURITY MATTERS Data Breaches § 75.115 Risk analysis. If a data breach involving sensitive... analysis or VA's Office of Inspector General conducts an independent risk analysis of the data breach. The...
Aeroelastic stability analysis of a Darrieus wind turbine
Energy Technology Data Exchange (ETDEWEB)
Popelka, D.
1982-02-01
An aeroelastic stability analysis has been developed for predicting flutter instabilities on vertical axis wind turbines. The analytical model and mathematical formulation of the problem are described as well as the physical mechanism that creates flutter in Darrieus turbines. Theoretical results are compared with measured experimental data from flutter tests of the Sandia 2 Meter turbine. Based on this comparison, the analysis appears to be an adequate design evaluation tool.
Assessment of the Prony's method for BWR stability analysis
International Nuclear Information System (INIS)
Ortiz-Villafuerte, Javier; Castillo-Duran, Rogelio; Palacios-Hernandez, Javier C.
2011-01-01
Highlights: → This paper describes a method to determine the degree of stability of a BWR. → Performance comparison between Prony's and common AR techniques is presented. → Benchmark data and actual BWR transient data are used for comparison. → DR and f results are presented and discussed. → The Prony's method is shown to be a robust technique for BWR stability. - Abstract: It is known that Boiling Water Reactors are susceptible to present power oscillations in regions of high power and low coolant flow, in the power-flow operational map. It is possible to fall in one of such instability regions during reactor startup, since both power and coolant flow are being increased but not proportionally. One other possibility for falling into those areas is the occurrence of a trip of recirculation pumps. Stability monitoring in such cases can be difficult, because the amount or quality of power signal data required for calculation of the stability key parameters may not be enough to provide reliable results in an adequate time range. In this work, the Prony's Method is presented as one complementary alternative to determine the degree of stability of a BWR, through time series data. This analysis method can provide information about decay ratio and oscillation frequency from power signals obtained during transient events. However, so far not many applications in Boiling Water Reactors operation have been reported and supported to establish the scope of using such analysis for actual transient events. This work presents first a comparison of decay ratio and frequency oscillation results obtained by Prony's method and those results obtained by the participants of the Forsmark 1 and 2 Boiling Water Reactor Stability Benchmark using diverse techniques. Then, a comparison of decay ratio and frequency oscillation results is performed for four real BWR transient event data, using Prony's method and two other techniques based on an autoregressive modeling. The four
Analysis of edge stability for models of heat flux width
Directory of Open Access Journals (Sweden)
M.A. Makowski
2017-08-01
Full Text Available Detailed measurements of the ne, Te, and Ti profiles in the vicinity of the separatrix of ELMing H-mode discharges have been used to examine plasma stability at the extreme edge of the plasma and assess stability dependent models of the heat flux width. The results are strongly contrary to the critical gradient model, which posits that a ballooning instability determines a gradient scale length related to the heat flux width. The results of this analysis are not sensitive to the choice of location to evaluate stability. Significantly, it is also found that the results are completely consistent with the heuristic drift model for the heat flux width. Here the edge pressure gradient scales with plasma density and is proportional to the pressure gradient inferred from the equilibrium in accordance with the predictions of that theory.
Stability analysis for stochastic BAM nonlinear neural network with delays
Lv, Z. W.; Shu, H. S.; Wei, G. L.
2008-02-01
In this paper, stochastic bidirectional associative memory neural networks with constant or time-varying delays is considered. Based on a Lyapunov-Krasovskii functional and the stochastic stability analysis theory, we derive several sufficient conditions in order to guarantee the global asymptotically stable in the mean square. Our investigation shows that the stochastic bidirectional associative memory neural networks are globally asymptotically stable in the mean square if there are solutions to some linear matrix inequalities(LMIs). Hence, the global asymptotic stability of the stochastic bidirectional associative memory neural networks can be easily checked by the Matlab LMI toolbox. A numerical example is given to demonstrate the usefulness of the proposed global asymptotic stability criteria.
THE FINANCIAL STABILITY ANALYSIS THROUGH THE WORKING CAPITAL
Directory of Open Access Journals (Sweden)
LĂPĂDUŞI MIHAELA LOREDANA
2012-12-01
Full Text Available The main goal of any business is to maintain the financial stability not only on the short term but also on medium and long term, in other words to maintain a harmony between financial sources and financial needs, respectively the equality between the assets and liabilities from the balance sheet. On short term, maintaining the financial stability involves correlating the temporary resources with the temporary uses by using the necessary working capital, and on the long-term, the financial stability involves comparing the permanent resources with the permanent uses by working capital indicator. The determination of the financial state of the company at a certain moment represents the key moment in establishing and adopting the economic and financial decisions in the management of the company. Maintaining the financial stability of the company represents one of the main objectives of the financial analysis and management and it also provides the optimum development of the entire economic and financial activity of the company. The analysis of the working capital size is based on the financial statement data and information, and based on this analysis is considered the financial situation of the company, the financial equilibrium state at a certain moment. The purpose of this article is to highlight the fact that the maintenance of the financial stability on medium and long term is subordinated to the “working capital” indicator, its content and interpretation evolving in time and varying differently from one company to another. The results of this research may have broad applicability in the field of the companies’ activity and it materializes in the complex approach of the working capital regarded as a classic indicator, frequently used in the financial analysis and with profound significance in establishing the financial state in general and the equilibrium state in particular.
Dynamic stability and bifurcation analysis in fractional thermodynamics
Béda, Péter B.
2018-02-01
In mechanics, viscoelasticity was the first field of applications in studying geomaterials. Further possibilities arise in spatial non-locality. Non-local materials were already studied in the 1960s by several authors as a part of continuum mechanics and are still in focus of interest because of the rising importance of materials with internal micro- and nano-structure. When material instability gained more interest, non-local behavior appeared in a different aspect. The problem was concerned to numerical analysis, because then instability zones exhibited singular properties for local constitutive equations. In dynamic stability analysis, mathematical aspects of non-locality were studied by using the theory of dynamic systems. There the basic set of equations describing the behavior of continua was transformed to an abstract dynamic system consisting of differential operators acting on the perturbation field variables. Such functions should satisfy homogeneous boundary conditions and act as indicators of stability of a selected state of the body under consideration. Dynamic systems approach results in conditions for cases, when the differential operators have critical eigenvalues of zero real parts (dynamic stability or instability conditions). When the critical eigenvalues have non-trivial eigenspace, the way of loss of stability is classified as a typical (or generic) bifurcation. Our experiences show that material non-locality and the generic nature of bifurcation at instability are connected, and the basic functions of the non-trivial eigenspace can be used to determine internal length quantities of non-local mechanics. Fractional calculus is already successfully used in thermo-elasticity. In the paper, non-locality is introduced via fractional strain into the constitutive relations of various conventional types. Then, by defining dynamic systems, stability and bifurcation are studied for states of thermo-mechanical solids. Stability conditions and genericity
Ideal MHD stability analysis of KSTAR target AT mode
International Nuclear Information System (INIS)
Yi, S.M.; Kim, J.H.; You, K.I.; Kim, J.Y.
2009-01-01
Full text: A main research objective of KSTAR (Korea Superconducting Tokamak Advanced Research) device is to demonstrate the steady-state operation capability of high-performance AT (Advanced Tokamak) mode. To meet this goal, it is critical for KSTAR to have a good MHD stability boundary, particularly against the high-beta ideal instabilities such as the external kink and the ballooning modes. To support this MHD stability KSTAR has been designed to have a strong plasma shape and a close interval between plasma and passive- plate wall. During the conceptual design phase of KSTAR, a preliminary study was performed to estimate the high beta MHD stability limit of KSTAR target AT mode using PEST and VACUUM codes and it was shown that the target AT mode can be stable up to β N ∼ 5 with a well-defined plasma pressure and current profiles. Recently, a new calculation has been performed to estimate the ideal stability limit in various KSTAR operating conditions using DCON code, and it has been observed that there is some difference between the new and old calculation results, particularly in the dependence of the maximum β N value on the toroidal mode number. Here, we thus present a more detailed analysis of the ideal MHD stability limit of KSTAR target AT mode using various codes, which include GATO as well as PEST and DCON, in the comparison of calculation results among the three codes. (author)
Spatial energy market risk analysis using the semivariance risk measure
International Nuclear Information System (INIS)
Yu, Zuwei
2007-01-01
The paper concentrates on the analysis of semivariance (SV) as a market risk measure for market risk analysis of mean-semivariance (MSV) portfolios. The advantage of MSV over variance as a risk measure is that MSV provides a more logical measure of risk than the MV method. In addition, the relationship of the SV with the lower partial movements is discussed. A spatial risk model is proposed as a basis of risk assessment for short-term energy markets. Transaction costs and other practical constraints are also included. A case study is provided to show the successful application of the model. (author)
Stability Analysis of the Slowed-Rotor Compound Helicopter Configuration
Floros, Matthew W.; Johnson, Wayne
2007-01-01
The stability and control of rotors at high advance ratio are considered. Teetering, articulated, gimbaled, and rigid hub types are considered for a compound helicopter (rotor and fixed wing). Stability predictions obtained using an analytical rigid flapping blade analysis, a rigid blade CAMRAD II model, and an elastic blade CAMRAD II model are compared. For the flapping blade analysis, the teetering rotor is the most stable, showing no instabilities up to an advance ratio of 3 and a Lock number of 18. A notional elastic blade model of a teetering rotor is unstable at an advance ratio of 1.5, independent of pitch frequency. Analysis of the trim controls and blade flapping shows that for small positive collective pitch, trim can be maintained without excessive control input or flapping angles.
Risk Analysis Group annual progress report 1984
International Nuclear Information System (INIS)
1985-06-01
The activities of the Risk Analysis Group at Risoe during 1984 are presented. These include descriptions in some detail of work on general development topics and risk analysis performed as contractor. (author)
International Nuclear Information System (INIS)
Wheeler, T.
1994-12-01
The potential radiological and nonradiological risks associated with specific radioactive waste shipping campaigns at the Hanford Site are estimated. The shipping campaigns analyzed are associated with the transportation of wastes from the N-Reactor site at the 200-W Area, both within the Hanford Reservation, for disposal. The analysis is based on waste that would be generated from the N-Reactor stabilization program
Stability Analysis of a Helicopter with an External Slung Load System
Thanapalan, Kary
2016-01-01
This paper describes the stability analysis of a helicopter with an underslung external load system. The Lyapunov second method is considered for the stability analysis. The system is considered as a cascade connection of uncertain nonlinear system. The stability analysis is conducted to ensure the stabilisation of the helicopter system and the positioning of the underslung load at hover condition. Stability analysis and numerical results proved that if desired condition for the stability is ...
Behrendt, Silke; Bühringer, Gerhard; Höfler, Michael; Lieb, Roselind; Beesdo-Baum, Katja
2017-10-01
Comorbid internalizing mental disorders in alcohol use disorders (AUD) can be understood as putative independent risk factors for AUD or as expressions of underlying shared psychopathology vulnerabilities. However, it remains unclear whether: 1) specific latent internalizing psychopathology risk-profiles predict AUD-incidence and 2) specific latent internalizing comorbidity-profiles in AUD predict AUD-stability. To investigate baseline latent internalizing psychopathology risk profiles as predictors of subsequent AUD-incidence and -stability in adolescents and young adults. Data from the prospective-longitudinal EDSP study (baseline age 14-24 years) were used. The study-design included up to three follow-up assessments in up to ten years. DSM-IV mental disorders were assessed with the DIA-X/M-CIDI. To investigate risk-profiles and their associations with AUD-outcomes, latent class analysis with auxiliary outcome variables was applied. AUD-incidence: a 4-class model (N=1683) was identified (classes: normative-male [45.9%], normative-female [44.2%], internalizing [5.3%], nicotine dependence [4.5%]). Compared to the normative-female class, all other classes were associated with a higher risk of subsequent incident alcohol dependence (p<0.05). AUD-stability: a 3-class model (N=1940) was identified with only one class (11.6%) with high probabilities for baseline AUD. This class was further characterized by elevated substance use disorder (SUD) probabilities and predicted any subsequent AUD (OR 8.5, 95% CI 5.4-13.3). An internalizing vulnerability may constitute a pathway to AUD incidence in adolescence and young adulthood. In contrast, no indication for a role of internalizing comorbidity profiles in AUD-stability was found, which may indicate a limited importance of such profiles - in contrast to SUD-related profiles - in AUD stability. Copyright © 2017 Elsevier B.V. All rights reserved.
A background risk analysis. Vol. 1
International Nuclear Information System (INIS)
Taylor, J.R.
1979-01-01
This 4-volumes report gives a background of ideas, principles, and examples which might be of use in developing practical methods for risk analysis. Some of the risk analysis techniques, described are somewhat experimental. The report is written in an introductory style, but where some point needs further justification or evaluation, this is given in the form of a chapter appendix. In this way, it is hoped that the report can serve two purposes, - as a basis for starting risk analysis work and as a basis for discussing effectiveness of risk analysis procedures. The report should be seen as a preliminary stage, prior to a program of industrial trials of risk analysis methods. Vol. 1 contains a short history of risk analysis, and chapters on risk, failures, errors and accidents, and general procedures for risk analysis. (BP)
A background to risk analysis. Vol. 3
International Nuclear Information System (INIS)
Taylor, J.R.
1979-01-01
This 4-volumes report gives a background of ideas, principles, and examples which might be of use in developing practical methods for risk analysis. Some of the risk analysis techniques described are somewhat experimental. The report is written in an introductory style, but where some point needs further justifi- cation or evaluation, this is given in the form of a chapter appenix. In this way, it is hoped that the report can serve two purposes, - as a basis for starting risk analysis work and as a basis for discussing effectiveness of risk analysis procedures. The report should be seen as a preliminary stage, prior to a program of industrial trials of risk analysis methods. Vol. 3 contains chapters on quantification of risk, failure and accident probability, risk analysis and design, and examles of risk analysis for process plant. (BP)
Stability Analysis of Periodic Systems by Truncated Point Mappings
Guttalu, R. S.; Flashner, H.
1996-01-01
An approach is presented deriving analytical stability and bifurcation conditions for systems with periodically varying coefficients. The method is based on a point mapping(period to period mapping) representation of the system's dynamics. An algorithm is employed to obtain an analytical expression for the point mapping and its dependence on the system's parameters. The algorithm is devised to derive the coefficients of a multinominal expansion of the point mapping up to an arbitrary order in terms of the state variables and of the parameters. Analytical stability and bifurcation condition are then formulated and expressed as functional relations between the parameters. To demonstrate the application of the method, the parametric stability of Mathieu's equation and of a two-degree of freedom system are investigated. The results obtained by the proposed approach are compared to those obtained by perturbation analysis and by direct integration which we considered to the "exact solution". It is shown that, unlike perturbation analysis, the proposed method provides very accurate solution even for large valuesof the parameters. If an expansion of the point mapping in terms of a small parameter is performed the method is equivalent to perturbation analysis. Moreover, it is demonstrated that the method can be easily applied to multiple-degree-of-freedom systems using the same framework. This feature is an important advantage since most of the existing analysis methods apply mainly to single-degree-of-freedom systems and their extension to higher dimensions is difficult and computationally cumbersome.
Stabilization diagrams using operationalmodal analysis and sliding filters
DEFF Research Database (Denmark)
Olsen, Peter; Juul, Martin O.; Tarpø, Marius
2017-01-01
This paper presents a filtering technique for doing effective operational modal analysis. The result of the filtering method is construction of stabilization diagram that clearly separates physical poles from spurious noise poles needed for unbiased fitting. A band pass filter is moved slowly ove......(TDPR) system identification algorithm on simulated data.......This paper presents a filtering technique for doing effective operational modal analysis. The result of the filtering method is construction of stabilization diagram that clearly separates physical poles from spurious noise poles needed for unbiased fitting. A band pass filter is moved slowly over...... the entire frequency spectrum of the measured data, and poles in the band are identified for each new filter position. In this way all poles are identified many times, making the physical poles stand out to make them immediately identifiable. The technique is illustrated using the Time Domain Poly Reference...
Preliminary hazards analysis of thermal scrap stabilization system. Revision 1
International Nuclear Information System (INIS)
Lewis, W.S.
1994-01-01
This preliminary analysis examined the HA-21I glovebox and its supporting systems for potential process hazards. Upon further analysis, the thermal stabilization system has been installed in gloveboxes HC-21A and HC-21C. The use of HC-21C and HC-21A simplified the initial safety analysis. In addition, these gloveboxes were cleaner and required less modification for operation than glovebox HA-21I. While this document refers to glovebox HA-21I for the hazards analysis performed, glovebox HC-21C is sufficiently similar that the following analysis is also valid for HC-21C. This hazards analysis document is being re-released as revision 1 to include the updated flowsheet document (Appendix C) and the updated design basis (Appendix D). The revised Process Flow Schematic has also been included (Appendix E). This Current revision incorporates the recommendations provided from the original hazards analysis as well. The System Design Description (SDD) has also been appended (Appendix H) to document the bases for Safety Classification of thermal stabilization equipment
Bank stability as a risk factor for pipeline infrastructure: a Scottish example
Maniatis, Georgios; Williams, Richard; Hoey, Trevor
2017-04-01
Bank erosion is a spatially variable process controlled by a number of factors that are interrelated (e.g. grain size, moisture content, organic content, vegetation, bank gradient). As a risk factor, bank erosion has been strongly connected to the failure of infrastructure that crosses or is adjacent to morphologically dynamic rivers. To manage this risk, comprehensive infrastructure asset management programs should include risk assessment of all structures that cross or are near a river. In Scotland, a significant proportion of cross-river infrastructure is pipe bridges, for both clean and waste water. These river crossings are maintained and managed by Scottish Water, a supplier responsible for a 48,000 km long drinking water pipe network and a 52,000 km long wastewater pipe network. Recently, Scottish Water began a comprehensive pipe bridge asset inspection program, which incorporates the acquisition of data to assess riverbank stability. The first step in the development of this database is the use of a prototype software application (a tablet app) which simplifies the surveying process by framing specific geomorphological questions and surveying tasks. As a result, the surveys can be conducted by inspectors with no specialist training in bank stability assessment and then reviewed by those with more expertise. Here, results are presented of a review of survey data, enabling the identification of the assets that are most at risk from bank erosion. The assessment focuses on assets from catchments in two contrasting areas of Scotland; the Hebrides and Glasgow. The uncertainty analysis focuses on input data quality and the variability of information available for desk based risk assessments using Geographic Information Systems (GIS). In parallel, considerations regarding the extension of this framework towards a unified strategy for assessing bank erosion are discussed such as the selection of a statistical framework and the catchment classification process
Tools for voltage stability analysis, including a probabilistic approach
Energy Technology Data Exchange (ETDEWEB)
Vieira Filho, X.; Martins, N.; Bianco, A.; Pinto, H.J.C.P. [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Pereira, M.V.F. [Power System Research (PSR), Inc., Rio de Janeiro, RJ (Brazil); Gomes, P.; Santos, M.G. dos [ELETROBRAS, Rio de Janeiro, RJ (Brazil)
1994-12-31
This paper reviews some voltage stability analysis tools that are being used or envisioned for expansion and operational planning studies in the Brazilian system, as well as, their applications. The paper also shows that deterministic tools can be linked together in a probabilistic framework, so as to provide complementary help to the analyst in choosing the most adequate operation strategies, or the best planning solutions for a given system. (author) 43 refs., 8 figs., 8 tabs.
Stability Analysis of Discontinuous Galerkin Approximations to the Elastodynamics Problem
Antonietti, Paola F.
2015-11-21
We consider semi-discrete discontinuous Galerkin approximations of both displacement and displacement-stress formulations of the elastodynamics problem. We prove the stability analysis in the natural energy norm and derive optimal a-priori error estimates. For the displacement-stress formulation, schemes preserving the total energy of the system are introduced and discussed. We verify our theoretical estimates on two and three dimensions test problems.
Mood-stabilizing pharmacological treatment in bipolar disorders and risk of suicide
DEFF Research Database (Denmark)
Søndergård, Lars; Lopez, Ana Garcia; Andersen, Per Kragh
2008-01-01
OBJECTIVES: This study investigated the association between continued mood-stabilizing treatment (lithium and anticonvulsants) in bipolar disorder (BD) and the risk of suicide. METHODS: Using linkage of national registers, the association between continued mood-stabilizing treatment and suicide w...... similar reduction in the rate of suicide, the results suggest that treatment with lithium may have some superiority in relation to prevention of suicide.......OBJECTIVES: This study investigated the association between continued mood-stabilizing treatment (lithium and anticonvulsants) in bipolar disorder (BD) and the risk of suicide. METHODS: Using linkage of national registers, the association between continued mood-stabilizing treatment and suicide...... was investigated among all patients discharged nationwide from hospital psychiatry as an in- or outpatient in a period from 1995 to 2000 in Denmark with a diagnosis of BD. RESULTS: A total of 5,926 patients were included in the study and among these 51 patients committed suicide eventually during the study period...
Mood-stabilizing pharmacological treatment in bipolar disorders and risk of suicide
DEFF Research Database (Denmark)
Søndergård, Lars; Lopez, A.G.; Andersen, Per Kragh
2008-01-01
Objectives: This study investigated the association between continued mood-stabilizing treatment (lithium and anticonvulsants) in bipolar disorder (BD) and the risk of suicide. Methods: Using linkage of national registers, the association between continued mood-stabilizing treatment and suicide w...... similar reduction in the rate of suicide, the results suggest that treatment with lithium may have some superiority in relation to prevention of suicide Udgivelsesdato: 2008......Objectives: This study investigated the association between continued mood-stabilizing treatment (lithium and anticonvulsants) in bipolar disorder (BD) and the risk of suicide. Methods: Using linkage of national registers, the association between continued mood-stabilizing treatment and suicide...... was investigated among all patients discharged nationwide from hospital psychiatry as an in- or outpatient in a period from 1995 to 2000 in Denmark with a diagnosis of BD. Results: A total of 5,926 patients were included in the study and among these 51 patients committed suicide eventually during the study period...
Habitat stability, predation risk and ‘memory syndromes’
Dalesman, S.; Rendle, A.; Dall, S.R.X.
2015-01-01
Habitat stability and predation pressure are thought to be major drivers in the evolutionary maintenance of behavioural syndromes, with trait covariance only occurring within specific habitats. However, animals also exhibit behavioural plasticity, often through memory formation. Memory formation across traits may be linked, with covariance in memory traits (memory syndromes) selected under particular environmental conditions. This study tests whether the pond snail, Lymnaea stagnalis, demonstrates consistency among memory traits (‘memory syndrome’) related to threat avoidance and foraging. We used eight populations originating from three different habitat types: i) laboratory populations (stable habitat, predator-free); ii) river populations (fairly stable habitat, fish predation); and iii) ditch populations (unstable habitat, invertebrate predation). At a population level, there was a negative relationship between memories related to threat avoidance and food selectivity, but no consistency within habitat type. At an individual level, covariance between memory traits was dependent on habitat. Laboratory populations showed no covariance among memory traits, whereas river populations showed a positive correlation between food memories, and ditch populations demonstrated a negative relationship between threat memory and food memories. Therefore, selection pressures among habitats appear to act independently on memory trait covariation at an individual level and the average response within a population. PMID:26013966
Stability Analysis of a Reaction-Diffusion System Modeling Atherogenesis
Ibragimov, Akif
2010-01-01
This paper presents a linear, asymptotic stability analysis for a reaction-diffusionconvection system modeling atherogenesis, the initiation of atherosclerosis, as an inflammatory instability. Motivated by the disease paradigm articulated by Ross, atherogenesis is viewed as an inflammatory spiral with a positive feedback loop involving key cellular and chemical species interacting and reacting within the intimal layer of muscular arteries. The inflammatory spiral is initiated as an instability from a healthy state which is defined to be an equilibrium state devoid of certain key inflammatory markers. Disease initiation is studied through a linear, asymptotic stability analysis of a healthy equilibrium state. Various theorems are proved, giving conditions on system parameters guaranteeing stability of the health state, and a general framework is developed for constructing perturbations from a healthy state that exhibit blow-up, which are interpreted as corresponding to disease initiation. The analysis reveals key features that arterial geometry, antioxidant levels, and the source of inflammatory components (through coupled third-kind boundary conditions or through body sources) play in disease initiation. © 2010 Society for Industrial and Applied Mathematics.
Decentralized, cooperative control of multivehicle systems: Design and stability analysis
Weitz, Lesley Anne
2009-12-01
This dissertation addresses the design and stability analysis of decentralized, cooperative control laws for multivehicle systems. Advances in communication, navigation, and surveillance systems have enabled greater autonomy in multivehicle systems, and there is a shift toward decentralized, cooperative systems for computational efficiency and robustness. In a decentralized control scheme, control inputs are determined onboard each vehicle; therefore, decentralized controllers are more efficient for large numbers of vehicles, and the system is more robust to communication failures and reconfiguration. The design of decentralized, cooperative control laws is explored for a nonlinear vehicle model that can be represented in a double-integrator form. Cooperative controllers are functions of spacing errors with respect to other vehicles in the system, where the communication structure defines the information that is available to each vehicle. Control inputs are selected to achieve internal stability, or zero steady-state spacing errors, between vehicles in the system. Closed-loop equations of motion for the cooperative system can be written in a structural form, where damping and stiffness matrices contain control gains acting on the velocity and positions of the vehicles, respectively. The form of the stiffness matrix is determined by the communication structure, where different communication structures yield different control forms. Communication structures are compared using two structural analysis tools: modal cost and frequency-response functions, which evaluate the response of the multivehicle systems to disturbances. The frequency-response information is shown to reveal the string stability of different cooperative control forms. The effects of time delays in the feedback states of the cooperative control laws on system stability are also investigated. Closed-loop equations of motion are modeled as delay differential equations, and two stability notions are
Financial Analysis Analogies for Software Risk
Masood Uzzafer
2010-01-01
A dynamic software risk assessment model is presented. Analogies between dynamic financial analysis and software risk assessment models are established and based on these analogies it suggested that dynamic risk model for software projects is the way to move forward for the risk assessment of software project. It is shown how software risk assessment change during different phases of a software project and hence requires a dynamic risk assessment model to capture these va...
The analysis of actual versus perceived risks
International Nuclear Information System (INIS)
Covello, V.T.; Flamm, W.G.; Rodricks, J.V.; Tardiff, R.G.
1983-01-01
The major aims of the Society for Risk Analysis, as stated in its constitution, are to promote knowledge and understanding of risk analysis techniques and their applications; to promote communication and interaction among those engaged in risk analysis; and to disseminate risk analysis information and promote the advancement of all aspects of risk analysis. Members of the Society are drawn from a variety of disciplines, including the health sciences, engineering, the physical sciences, the humanities, and the behavioral and social sciences. An important function of the Society is the annual meeting, at which various aspects of risk analysis are discussed. The first annual meeting, represented by this volume, was the International Workshop on the Analysis of Actual vs. Perceived Risks, held from June 1-3, 1981, at the National Academy of Sciences in Washington, DC
Sex offender modus operandi stability and relationship with actuarial risk assessment.
Lasher, Michael P; McGrath, Robert J; Cumming, Georgia F
2015-03-01
Three studies conducted in Vermont yielded data on 82 sexual recidivists' index offenses (Time 1) and sexual reoffenses (Time 2) across 16 modus operandi (MO) characteristics. The current study examines the stability of these 16 characteristics between Time 1 and Time 2 offenses. Probabilities of Time 1-Time 2 characteristic combinations are reported, including when controlling for static risk as measured by the Static-99R and Vermont Assessment of Sex Offender Risk-2 (VASOR-2). Overall, considerable stability of offenders' MO was evident between Time 1 and Time 2 offenses. Victim characteristics and offense behaviors were the most stable MO characteristics, and degree of force used and victim injury were less stable and trended toward less forceful and less injurious reoffenses. Controlling for static risk had little impact on the patterns of MO stability. © The Author(s) 2014.
Stability Analysis of Methane Hydrate-Bearing Soils Considering Dissociation
Directory of Open Access Journals (Sweden)
Hiromasa Iwai
2015-06-01
Full Text Available It is well known that the methane hydrate dissociation process may lead to unstable behavior such as large ground deformations, uncontrollable gas production, etc. A linear instability analysis was performed in order to investigate which variables have a significant effect on the onset of the instability behavior of methane hydrate-bearing soils subjected to dissociation. In the analysis a simplified viscoplastic constitutive equation is used for the soil sediment. The stability analysis shows that the onset of instability of the material system mainly depends on the strain hardening-softening parameter, the degree of strain, and the permeability for water and gas. Then, we conducted a numerical analysis of gas hydrate-bearing soil considering hydrate dissociation in order to investigate the effect of the parameters on the system. The simulation method used in the present study can describe the chemo-thermo-mechanically coupled behaviors such as phase changes from hydrates to water and gas, temperature changes and ground deformation. From the numerical results, we found that basically the larger the permeability for water and gas is, the more stable the simulation results are. These results are consistent with those obtained from the linear stability analysis.
RAMS (Risk Analysis - Modular System) methodology
Energy Technology Data Exchange (ETDEWEB)
Stenner, R.D.; Strenge, D.L.; Buck, J.W. [and others
1996-10-01
The Risk Analysis - Modular System (RAMS) was developed to serve as a broad scope risk analysis tool for the Risk Assessment of the Hanford Mission (RAHM) studies. The RAHM element provides risk analysis support for Hanford Strategic Analysis and Mission Planning activities. The RAHM also provides risk analysis support for the Hanford 10-Year Plan development activities. The RAMS tool draws from a collection of specifically designed databases and modular risk analysis methodologies and models. RAMS is a flexible modular system that can be focused on targeted risk analysis needs. It is specifically designed to address risks associated with overall strategy, technical alternative, and `what if` questions regarding the Hanford cleanup mission. RAMS is set up to address both near-term and long-term risk issues. Consistency is very important for any comparative risk analysis, and RAMS is designed to efficiently and consistently compare risks and produce risk reduction estimates. There is a wide range of output information that can be generated by RAMS. These outputs can be detailed by individual contaminants, waste forms, transport pathways, exposure scenarios, individuals, populations, etc. However, they can also be in rolled-up form to support high-level strategy decisions.
Stability Analysis for Seed Yield over Environments in Coriander
Directory of Open Access Journals (Sweden)
Sangeeta Yadav
2016-11-01
Full Text Available Thirty five genotypes of coriander (Coriandrum sativum L. were tested in four artificially created environments to judge their stability in performance of seed yield. The differences among genotypes and environments were significant for seed yield. Stability parameters varied considerably among the tested genotypes in all the methods used. The variation in result in different methods was due to non-fulfillment of assumption of different models. However, AMMI analysis provides the information on main effects as well as interaction effects and depiction of PCA score gives better understanding of the pattern of genotype – environment interaction. The sum of squares due to PCAs was also used for the computation of AMMI stability values for better understanding of the adaptability behavior of genotypes hence, additive main effects and multiplicative interaction (AMMI model was most appropriate for the analysis of G x E interactions for seed yield in coriander. Genotypes RVC 15, RVC 19, RVC 22, RVC 25 and Panipat local showed wider adaptability while, Simpo S 33 exhibited specific adaptability to favourable conditions of high fertility. These genotypes could be utilized in breeding programmers to transfer the adaptability genes into high yielding genetic back ground of coriander.
Stability analysis on natural circulation boiling water reactors
Energy Technology Data Exchange (ETDEWEB)
Metz, Peter
1999-05-01
The purpose of the study is a stability analysis of the simplified boiling water reactor concept. A fluid dynamics code, DYNOS, was developed and successfully validated against FRIGG and DESIRE data and a stability benchmark on the Ringhals 1 forced circulation BWR. Three simplified desings were considered in the analysis: The SWRIOOO by Siemens and the SBWR and ESBWR from the General Electric Co. For all three design operational characteristics, i.e. power versus flow rate maps, were calculated. The effects which different geometric and operational parameters, such as the riser height, inlet subcooling etc., have on the characteristics have been investigated. Dynamic simulations on the three simplified design revealed the geysering and the natural circulation oscillations modes only. They were, however, only encountered at pressure below 0.6 MPa. Stability maps for all tree simplified BWRs were calculated and plotted. The study concluded that a fast pressurisation of the reactor vessel is necessary to eliminate the possibility of geysering or natural circulation oscillations mode instability. (au) 26 tabs., 88 ills.
Analysis of the hydrodynamic stability of natural circulation
International Nuclear Information System (INIS)
Olive, J.; Baby, J.P.
1980-01-01
A mathematical model (EOLE) for the analysis of the stability of boilers with natural circulation is discussed. The method employed consists in linearizing one-dimensional flow equations and in integrating them while employing the Laplace transformation. The properties of a two-phase fluid are schematized by a homogeneous model with slip. The computation results in the circulation loop transfer functions and its natural modes of oscillation (frequency and damping). A discussion follows which compares results obtained with this method to those of other existing models in the case of a straight pipe with forced circulation. Agreement proved to be satisfactory. The results are then given of a parametric study involving the stability of a PWR natural circulation steam generator. These results show that the model can satisfy, at least qualitatively, trends observed empirically or obtained with other more complex theoretical models. (author)
Stability Analysis and Design of Impulsive Control Lorenz Systems Family
International Nuclear Information System (INIS)
Yu Yongbin; Zhang Fengli; Zhang Hongbin; Yu Juebang; Liao Xiaofeng
2009-01-01
Lorenz systems family unifying Lorenz system, Chen system and Lue system is a typical chaotic family. In this paper, we consider impulsive control Lorenz chaotic systems family with time-varying impulse intervals. By establishing an effective tool of a set of inequalities, we analyze the asymptotic stability of impulsive control Lorenz systems family and obtain some new less conservative conditions. Based on the stability analysis, we design a novel impulsive controller with time-varying impulse intervals. Illustrative examples are provided to show the feasibility and effectiveness of our method. The obtained results not only can be used to design impulsive control for Lorenz systems family, but also can be extended to other chaotic systems. (general)
Stability analysis of maize hybrids across north west of Pakistan
International Nuclear Information System (INIS)
Rahman, H.; Durreshawar; Ali, S.; Iftikhar, F.; Khalil, I.H.; Shah, S.M.A.; Ahmad, H.
2010-01-01
Stability analysis was carried out to study stability in performance and genotype x environment interactions for 18 maize hybrids across three locations of NWFP i.e., Agricultural University Peshawar (AUP), Agricultural Research Station (ARS), Baffa, (Mansehra) and Cereal Crops Research Institute (CCRI), Pirsabak (Nowshera), during 2006. Data were recorded on different morphological and yield parameters. Analysis of variance indicated significant differences among the three locations for all the traits studied. Hybrids showed significant differences for all parameters except anthesis silking interval (ASI) and ear height, which were non significant across the three locations. The hybrid x location interactions also revealed significant differences for days to 50% silking, days to 50% anthesis, ASI, grain moisture at harvest and grain yield per hectare while non significant differences were observed for plant height and ear height. Based on yield performance of hybrids across the three locations, Baffa ranked first as compared to the other two locations. Hybrid DK-1 x EV-9806 was the highest yielding across the three locations followed by hybrid AGB-108, while the lowest yield was observed for hybrid CSCY. Stability in performance was evident for hybrid CS-2Y2 with regard to days required for silking and anthesis. Stability in anthesis silking interval (ASI) was manifested for hybrid CS-222. Hybrid AGB-108 was comparatively stable for grain yield across the tested locations. Remaining hybrids seemed to be considerably influenced by Genotype x environment interactions encountered at the tested locations and location specific selection has to be made while selecting a maize hybrid for a particular location. (author)
Structural stability analysis considerations in fusion reactor plasma chamber design
International Nuclear Information System (INIS)
Delaney, M.J.; Cramer, B.A.
1978-01-01
This paper presents an approach to analyzing a toroidal plasma chamber for the prevention of both static and dynamic buckling. Results of stability analyses performed for the doublet shaped plasma chamber of the General Atomic 3.8 meter radius TNS ignition test reactor are presented. Load conditions are the static external atmospheric pressure load and the dynamic plasma disruption pulse load. Methods for analysis of plasma chamber structures are presented for both types of load. Analysis for static buckling is based on idealizing the plasma chamber into standard structural shapes and applying classical cylinder and circular torus buckling equations. Results are verified using the Buckling of Shells of Revolution (BOSOR4) finite difference computer code. Analysis for the dynamic loading is based on a pulse buckling analysis method for circular cylinders
Tear film stability analysis system: introducing a new application for videokeratography.
Goto, Tomoko; Zheng, Xiaodong; Okamoto, Shigeki; Ohashi, Yuichi
2004-11-01
To review our previous studies regarding the development of a tear stability analysis system (TSAS) using videokeratography and the clinical application of TSAS for evaluation of tear film stability in patients subject to laser in situ keratomileusis (LASIK). New software, namely TSAS, was developed for the videokeratography system TMS-2N (topographic modeling system). TSAS automatically captures consecutive corneal surface images every second for 10 seconds. Corneal topographs were analyzed for tear breakup time (TMS-BUT) and tear breakup area (TMS-BUA, the ratio of breakup area to entire color-code area). First, we recruited volunteers to test the sensitivity and specificity of this new system in comparison with the routine method for tear stability analysis, tear film breakup time evaluation by slit-lamp microscope (SLE-BUT), with fluorescence staining. Second, we investigated the practicability of TSAS in dynamic evaluation of tear film stability before and after LASIK. TMS-BUT had a positive correlation with SLE-BUT, whereas TMS-BUA showed a negative correlation. Although they showed similar rates of specificity as SLE-BUT, the sensitivity rates of TMS-BUT and TMS-BUA were 97.5% and 95%, respectively, significantly higher than that of SLE-BUT (75%). The study on patients subject to LASIK showed that tear film stability significantly decreased during the early time period following LASIK and resolved at 6 months after surgery. Eyes that had abnormal TSAS evaluation tended to have higher risk of developing superficial punctuate keratitis and dry eye symptoms after LASIK, and their responses to treatment were slow. TSAS is a noninvasive and objective method with higher sensitivity for tear film stability analysis than SLE-BUT.
National Research Council Canada - National Science Library
Gaonkar, G
1998-01-01
Rotorcraft stability investigation involves a nonlinear trim analysis for the control inputs and periodic responses, and, as a follow-up, a linearized stability analysis for the Floquet transition matrix (FTM...
DEFF Research Database (Denmark)
Mihet-Popa, Lucian; Groza, Voicu; Isleifsson, Fridrik Rafn
2012-01-01
Experimental Testing for Stability Analysis of Distributed Energy Resources Components with Storage Devices and Loads......Experimental Testing for Stability Analysis of Distributed Energy Resources Components with Storage Devices and Loads...
Streamlining project delivery through risk analysis.
2015-08-01
Project delivery is a significant area of concern and is subject to several risks throughout Plan Development : Process (PDP). These risks are attributed to major areas of project development, such as environmental : analysis, right-of-way (ROW) acqu...
METHODOLOGY FOR INSTITUTIONAL ANALYSIS OF STABILITY OF REGIONAL FINANCIAL SYSTEM
Directory of Open Access Journals (Sweden)
A. V. Milenkov
2016-01-01
Full Text Available The relevance of the article due to the urgent need to develop a methodological framework in the field of regional finance research dictated by the substantial increase in the volume and composition of the socio-economic problems, the solution of which, including financial support, the responsibility of the public authorities of the Russian Federation. The article presents the results of the author's research in the field of institutional analysis of the stability of the regional financial system as a set of institutions and organizations interacting with the regional real sector of economy.Methodology. The methodological basis of this article are the economic and statistical methods of analysis, legal documents in the field of the sustainability of the regional financial system, publications in the field of economic and financial security.Conclusions / relevance. The practical significance of the work lies in the provisions of orientation, conclusions and recommendations aimed at the widespread use of search and adaptation of the institutional analysis of the sources of the regional stability of the financial system, which can be used by the legislative and executive authorities of the Russian Federation, the Ministry of Defence in the current activity.Methodological approaches to the structuring objectives of institutional analysis on the basis of the hierarchical representation of the institutional environment of functioning of federal subject the financial system.
Directory of Open Access Journals (Sweden)
Muhammad H. Al-Malack
2016-07-01
Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.
LISA Pathfinder E2E performance simulation: optical and self-gravity stability analysis
Brandt, N.; Fichter, W.; Kersten, M.; Lucarelli, S.; Montemurro, F.
2005-05-01
End-to-end (E2E) modelling and simulation, i.e. verifying the science performance of LISA Pathfinder (spacecraft and payload), is mandatory in order to minimize mission risks. In this paper, focus is on two particular applications of the E2E performance simulator currently being developed at EADS Astrium GmbH: the opto-dynamical stability and the self-gravity disturbance stability analysis. The E2E models applied here comprise the opto-dynamical modelling of the optical metrology systems (OMS) laser interferometry, the thermo-elastic distortion modelling of the OMS optical elements and the self-gravity disturbance model accounting for structural distortions. Preliminary analysis results are presented in detail, identifying shortcomings of the current LISA technology package (LTP) mounting baseline. As a consequence, the design is now being revised.
LISA Pathfinder E2E performance simulation: optical and self-gravity stability analysis
International Nuclear Information System (INIS)
Brandt, N; Fichter, W; Kersten, M; Lucarelli, S; Montemurro, F
2005-01-01
End-to-end (E2E) modelling and simulation, i.e. verifying the science performance of LISA Pathfinder (spacecraft and payload), is mandatory in order to minimize mission risks. In this paper, focus is on two particular applications of the E2E performance simulator currently being developed at EADS Astrium GmbH: the opto-dynamical stability and the self-gravity disturbance stability analysis. The E2E models applied here comprise the opto-dynamical modelling of the optical metrology systems (OMS) laser interferometry, the thermo-elastic distortion modelling of the OMS optical elements and the self-gravity disturbance model accounting for structural distortions. Preliminary analysis results are presented in detail, identifying shortcomings of the current LISA technology package (LTP) mounting baseline. As a consequence, the design is now being revised
Stability analysis of the high performance light water reactor
Energy Technology Data Exchange (ETDEWEB)
Ortega Gomez, Tino
2009-03-15
In the Generation IV international advanced nuclear reactor development program, the High Performance Light Water Reactor (HPLWR) is one of the most promising candidates. Important features are its inherently high thermodynamic efficiency (of approximately 45 %) and the ability to use existing supercritical water technology which previously has been developed and deployed for fossil fired power plants. Within a HPLWR core, the fluid experiences a drastic change in thermal and transport properties such as density, dynamic viscosity, specific heat and thermal conductivity, as the supercritical water is heated from 280 C to 500 C. The density change substantially exceeds that in a Boiling Water Reactor (i.e., HPLWR: density changes from 780 kg/m{sup 3} to 90 kg/m{sup 3}; BWR: density changes from 750 kg/m{sup 3} to 198 kg/m3). Due to this density change, the HPLWR can be - under certain operation parameters - susceptible to various thermal-hydraulic flow instabilities, which have to be avoided. In this thesis a stability analysis for the HPLWR is presented. This analysis is based on analytical considerations and numerical results, which were obtained by a computer code developed by the author. The heat-up stages of the HPLWR three-pass core are identified in respect to the relevant flow instability phenomena. The modeling approach successfully used for BWR stability analysis is extended to supercritical pressure operation conditions. In particular, a one-dimensional equation set representing the coolant flow of HPLWR fuel assemblies has been implemented in a commercial software named COMSOL to perform steady-state, time-dependent, and modal analyses. An investigation of important static instabilities (i.e., Ledinegg instabilities, flow maldistribution) and Pressure Drop Oscillations (PDO) have been carried out and none were found under operation conditions of the HPLWR. Three types of Density Wave Oscillation (DWO) modes have been studied: the single channel DWO, the
STABILITY ANALYSIS OF ORTHOTROPIC RECTANGULAR PLATES USING THE FORM FACTOR
Directory of Open Access Journals (Sweden)
Savin Sergey Yur’evich
2018-01-01
. We demonstrated how to obtain the solution of the stability problem for orthotropic rectangular plates by the form factor interpolation method using the results obtained from the aforementioned analytical expressions as the reference solutions. The solutions obtained by the form factor interpolation method are compared with the results of calculations by the finite element method and show a good accuracy. Conclusions: the analytical expressions for critical loads presented in this work can be used directly for the stability analysis of orthotropic rectangular plates loaded in one direction as well as to obtain one of the reference solutions by the form factor interpolation method for plates with arbitrary convex contour and combined boundary conditions. The proposed approach can be extended to other forms of plates, boundary conditions and loading types.
Physical Analysis Work for Slope Stability at Shah Alam, Selangor
Ishak, M. F.; Zaini, M. S. I.
2018-04-01
Slope stability analysis is performed to assess the equilibrium conditions and the safe design of a human-made or natural slope to find the endangered areas. Investigation of potential failure and determination of the slope sensitivity with regard to safety, reliability and economics were parts of this study. Ground anchor is designed to support a structure in this study. Ground anchor were implemented at the Mechanically Stabilized Earth (MSE) wall along Anak Persiaran Jubli Perak to overcome the further cracking of pavement parking, concrete deck and building of the Apartments. A result from the laboratory testing of soil sample such as index test and shear strength test were applied to the Slope/W software with regard to the ground anchors that were implemented. The ground anchors were implemented to increase the value of the factor of safety (FOS) of the MSE Wall. The value of the factor of safety (FOS) before implementing the ground anchor was 0.800 and after the ground anchor was implemented the value increase to 1.555. The increase percentage of factor of safety by implementing on stability of slope was 94.38%.
Stability Estimation of ABWR on the Basis of Noise Analysis
Furuya, Masahiro; Fukahori, Takanori; Mizokami, Shinya; Yokoya, Jun
In order to investigate the stability of a nuclear reactor core with an oxide mixture of uranium and plutonium (MOX) fuel installed, channel stability and regional stability tests were conducted with the SIRIUS-F facility. The SIRIUS-F facility was designed and constructed to provide a highly accurate simulation of thermal-hydraulic (channel) instabilities and coupled thermalhydraulics-neutronics instabilities of the Advanced Boiling Water Reactors (ABWRs). A real-time simulation was performed by modal point kinetics of reactor neutronics and fuel-rod thermal conduction on the basis of a measured void fraction in a reactor core section of the facility. A time series analysis was performed to calculate decay ratio and resonance frequency from a dominant pole of a transfer function by applying auto regressive (AR) methods to the time-series of the core inlet flow rate. Experiments were conducted with the SIRIUS-F facility, which simulates ABWR with MOX fuel installed. The variations in the decay ratio and resonance frequency among the five common AR methods are within 0.03 and 0.01 Hz, respectively. In this system, the appropriate decay ratio and resonance frequency can be estimated on the basis of the Yule-Walker method with the model order of 30.
DEFF Research Database (Denmark)
Yoon, Changwoo; Wang, Xiongfei; Bak, Claus Leth
2015-01-01
This paper investigates the harmonic stability of small-scale inverter-based power systems. A holistic procedure to assess the contribution of each inverter to the system stability is proposed by means of using the impedancebased stability criterion. Multiple unstable modes can be identified step......-by-step coming from the interactions among inverters and passive networks. Compared to the conventional system stability analysis, the approach is easy to implement and avoids the effect of potential unstable system dynamics on the impedance ratio derived for the stability analysis. PSCAD/ EMTDC simulations...... of a Cigre LV network Benchmark system with multiple renewable energy sources are carried out. The results confirm the validity of the proposed approach....
Analysis and Prediction of Micromilling Stability with Variable Tool Geometry
Directory of Open Access Journals (Sweden)
Ziyang Cao
2014-11-01
Full Text Available Micromilling can fabricate miniaturized components using micro-end mill at high rotational speeds. The analysis of machining stability in micromilling plays an important role in characterizing the cutting process, estimating the tool life, and optimizing the process. A numerical analysis and experimental method are presented to investigate the chatter stability in micro-end milling process with variable milling tool geometry. The schematic model of micromilling process is constructed and the calculation formula to predict cutting force and displacements is derived. This is followed by a detailed numerical analysis on micromilling forces between helical ball and square end mills through time domain and frequency domain method and the results are compared. Furthermore, a detailed time domain simulation for micro end milling with straight teeth and helical teeth end mill is conducted based on the machine-tool system frequency response function obtained through modal experiment. The forces and displacements are predicted and the simulation result between variable cutter geometry is deeply compared. The simulation results have important significance for the actual milling process.
Stabilization diagrams using operationalmodal analysis and sliding filters
DEFF Research Database (Denmark)
Olsen, Peter; Juul, Martin O.; Tarpø, Marius
2017-01-01
This paper presents a filtering technique for doing effective operational modal analysis. The result of the filtering method is construction of stabilization diagram that clearly separates physical poles from spurious noise poles needed for unbiased fitting. A band pass filter is moved slowly over...... the entire frequency spectrum of the measured data, and poles in the band are identified for each new filter position. In this way all poles are identified many times, making the physical poles stand out to make them immediately identifiable. The technique is illustrated using the Time Domain Poly Reference...
Frontal plane kinematics in walking with moderate hip osteoarthritis: stability and fall risk
Lin, X.B.; Meijer, O.G.; Lin, J.H.; Wu, W.H.; Lin, X.C.; Liang, B.W.; van Dieen, J.H.; Bruijn, S.M.
2015-01-01
Background Hip abductor weakness and unilateral pain in patients with moderate hip osteoarthritis may induce changes in frontal plane kinematics during walking that could affect stability and fall risk. Methods In 12 fall-prone patients with moderate hip osteoarthritis, 12 healthy peers, and 12
Overeating and Binge Eating in Emerging Adulthood: 10-Year Stability and Risk Factors
Goldschmidt, Andrea B.; Wall, Melanie M.; Zhang, Jun; Loth, Katie A.; Neumark-Sztainer, Dianne
2016-01-01
Overeating (eating an unusually large amount of food) and binge eating (overeating with loss of control [LOC]) predict adverse health consequences in adolescence. We aimed to characterize the stability of and risk factors for these distinct but interrelated constructs during critical developmental transitions. We used a population-based sample (n…
Study of nonlinear system stability using eigenvalue analysis: Gyroscopic motion
Shabana, Ahmed A.; Zaher, Mohamed H.; Recuero, Antonio M.; Rathod, Cheta
2011-11-01
orientation parameters and also to shed light on the important issue of using the eigenvalue analysis in the study of MBS stability. The validity of using the eigenvalue analysis based on the linearization of the nonlinear equations of motion in the study of the stability of railroad vehicle systems, which have known critical speeds, is examined. It is shown that such an eigenvalue analysis can lead to wrong conclusions regarding the stability of nonlinear systems.
Stability analysis of hybrid-driven underwater glider
Niu, Wen-dong; Wang, Shu-xin; Wang, Yan-hui; Song, Yang; Zhu, Ya-qiang
2017-10-01
Hybrid-driven underwater glider is a new type of unmanned underwater vehicle, which combines the advantages of autonomous underwater vehicles and traditional underwater gliders. The autonomous underwater vehicles have good maneuverability and can travel with a high speed, while the traditional underwater gliders are highlighted by low power consumption, long voyage, long endurance and good stealth characteristics. The hybrid-driven underwater gliders can realize variable motion profiles by their own buoyancy-driven and propeller propulsion systems. Stability of the mechanical system determines the performance of the system. In this paper, the Petrel-II hybrid-driven underwater glider developed by Tianjin University is selected as the research object and the stability of hybrid-driven underwater glider unitedly controlled by buoyancy and propeller has been targeted and evidenced. The dimensionless equations of the hybrid-driven underwater glider are obtained when the propeller is working. Then, the steady speed and steady glide path angle under steady-state motion have also been achieved. The steady-state operating conditions can be calculated when the hybrid-driven underwater glider reaches the desired steady-state motion. And the steadystate operating conditions are relatively conservative at the lower bound of the velocity range compared with the range of the velocity derived from the method of the composite Lyapunov function. By calculating the hydrodynamic coefficients of the Petrel-II hybrid-driven underwater glider, the simulation analysis has been conducted. In addition, the results of the field trials conducted in the South China Sea and the Danjiangkou Reservoir of China have been presented to illustrate the validity of the analysis and simulation, and to show the feasibility of the method of the composite Lyapunov function which verifies the stability of the Petrel-II hybrid-driven underwater glider.
Risk analysis of gravity dam instability using credibility theory Monte Carlo simulation model.
Xin, Cao; Chongshi, Gu
2016-01-01
Risk analysis of gravity dam stability involves complicated uncertainty in many design parameters and measured data. Stability failure risk ratio described jointly by probability and possibility has deficiency in characterization of influence of fuzzy factors and representation of the likelihood of risk occurrence in practical engineering. In this article, credibility theory is applied into stability failure risk analysis of gravity dam. Stability of gravity dam is viewed as a hybrid event considering both fuzziness and randomness of failure criterion, design parameters and measured data. Credibility distribution function is conducted as a novel way to represent uncertainty of influence factors of gravity dam stability. And combining with Monte Carlo simulation, corresponding calculation method and procedure are proposed. Based on a dam section, a detailed application of the modeling approach on risk calculation of both dam foundation and double sliding surfaces is provided. The results show that, the present method is feasible to be applied on analysis of stability failure risk for gravity dams. The risk assessment obtained can reflect influence of both sorts of uncertainty, and is suitable as an index value.
Risk analysis and safety rationale
International Nuclear Information System (INIS)
Bengtsson, G.
1989-01-01
Decision making with respect to safety is becoming more and more complex. The risk involved must be taken into account together with numerous other factors such as the benefits, the uncertainties and the public perception. Can the decision maker be aided by some kind of system, general rules of thumb, or broader perspective on similar decisions? This question has been addressed in a joint Nordic project relating to nuclear power. Modern techniques for risk assessment and management have been studied, and parallels drawn to such areas as offshore safety and management of toxic chemicals in the environment. The report summarises the finding of 5 major technical reports which have been published in the NORD-series. The topics includes developments, uncertainties and limitations in probabilistic safety assessments, negligible risks, risk-cost trade-offs, optimisation of nuclear safety and radiation protection, and the role of risks in the decision making process. (author) 84 refs
Floquet stability analysis of viscoelastic flow over a cylinder
Richter, David
2011-06-01
A Floquet linear stability analysis has been performed on a viscoelastic cylinder wake. The FENE-P model is used to represent the non-Newtonian fluid, and the analysis is done using a modified version of an existing nonlinear code to compute the linearized initial value problem governing the growth of small perturbations in the wake. By measuring instability growth rates over a wide range of disturbance spanwise wavenumbers α, the effects of viscoelasticity were identified and compared directly to Newtonian results.At a Reynolds number of 300, two unstable bands exist over the range 0. ≤ α≤ 10 for Newtonian flow. For the low α band, associated with the "mode A" wake instability, a monotonic reduction in growth rates is found for increasing polymer extensibility L. For the high α band, associated with the "mode B" instability, first a rise, then a significant decrease to a stable state is found for the instability growth rates as L is increased from L= 10 to L= 30. The mechanism behind this stabilization of both mode A and mode B instabilities is due to the change of the base flow, rather than a direct effect of viscoelasticity on the perturbation. © 2011 Elsevier B.V.
An Effective Distributed Model for Power System Transient Stability Analysis
Directory of Open Access Journals (Sweden)
MUTHU, B. M.
2011-08-01
Full Text Available The modern power systems consist of many interconnected synchronous generators having different inertia constants, connected with large transmission network and ever increasing demand for power exchange. The size of the power system grows exponentially due to increase in power demand. The data required for various power system applications have been stored in different formats in a heterogeneous environment. The power system applications themselves have been developed and deployed in different platforms and language paradigms. Interoperability between power system applications becomes a major issue because of the heterogeneous nature. The main aim of the paper is to develop a generalized distributed model for carrying out power system stability analysis. The more flexible and loosely coupled JAX-RPC model has been developed for representing transient stability analysis in large interconnected power systems. The proposed model includes Pre-Fault, During-Fault, Post-Fault and Swing Curve services which are accessible to the remote power system clients when the system is subjected to large disturbances. A generalized XML based model for data representation has also been proposed for exchanging data in order to enhance the interoperability between legacy power system applications. The performance measure, Round Trip Time (RTT is estimated for different power systems using the proposed JAX-RPC model and compared with the results obtained using traditional client-server and Java RMI models.
A background to risk analysis. Vol. 2
International Nuclear Information System (INIS)
Taylor, J.R.
1979-01-01
This 4-volumes report gives a background of ideas, principles and examples which might be of use in developing practical methods for risk analysis. Some of the risk analysis techniques described are somewhat experimental. The report is written in an introductory style, but where some point needs further justification or evaluation, this is given in the form of a chapter appendix. In this way, it is hoped that the report can serve two purposes, - as a basis for starting risk analysis work and as a basis for discussing effectiveness of risk analysis procedures. The report should be seen as a preliminary stage, prior to a program of industrial trials of risk analysis methods. Vol. 2 treats generic methods of qualitative failure analysis. (BP)
Analysis and assessment of STATCOM-based damping stabilizers for power system stability enhancement
Energy Technology Data Exchange (ETDEWEB)
Abido, M.A. [Electrical Engineering Department, King Fahd University of Petroleum and Minerals, KFUPM Box Number 183, Dhahran 31261 (Saudi Arabia)
2005-02-01
Power system stability enhancement via STATCOM-based stabilizers is thoroughly investigated in this paper. This study presents a singular value decomposition (SVD)-based approach to assess and measure the controllability of the poorly damped electromechanical modes by STATCOM different control channels. The coordination among the proposed damping stabilizers and the STATCOM internal ac and dc voltage controllers has been taken into consideration. The design problem of STATCOM-based stabilizers is formulated as an optimization problem. For coordination purposes, a time domain-based multiobjective junction to improve the system stability as well as ac and dc voltage regulation is proposed. Then, a real-coded genetic algorithm (RCGA) is employed to search for optimal stabilizer parameters. This aims to enhance both rotor angle stability and voltage regulation of the power system. The proposed stabilizers are tested on a weakly connected power system with different disturbances and loading conditions. The nonlinear simulation results show the effectiveness and robustness of the proposed control schemes over a wide range of loading conditions. It is also observed that the proposed STATCOM-based damping stabilizers extend the critical clearing time (CCT) and enhance greatly the power system transient stability.
Advances in Risk Analysis with Big Data.
Choi, Tsan-Ming; Lambert, James H
2017-08-01
With cloud computing, Internet-of-things, wireless sensors, social media, fast storage and retrieval, etc., organizations and enterprises have access to unprecedented amounts and varieties of data. Current risk analysis methodology and applications are experiencing related advances and breakthroughs. For example, highway operations data are readily available, and making use of them reduces risks of traffic crashes and travel delays. Massive data of financial and enterprise systems support decision making under risk by individuals, industries, regulators, etc. In this introductory article, we first discuss the meaning of big data for risk analysis. We then examine recent advances in risk analysis with big data in several topic areas. For each area, we identify and introduce the relevant articles that are featured in the special issue. We conclude with a discussion on future research opportunities. © 2017 Society for Risk Analysis.
van Aarle, B.; Engwerda, Jacob; Weeren, A.J.T.M.
2017-01-01
This paper analyses debt stabilization in a monetary union that features endogenous risk premia. In particular, debt stabilization in two diametrically opposed regimes is compared. In the first regime, the “national fiscal discipline regime”, financial markets impose sovereign risk premia based on
Geotechnical risk analysis user's guide
1987-03-01
All geotechnical predictions involve uncertainties. These are accounted for additionally by conservative factors of safety. Risk based design, on the other hand, attempts to quantify uncertainties and to adjust design conservatism accordingly. Such m...
Stability analysis of offshore wind farm and marine current farm
Shawon, Mohammad Hasanuzzaman
-trend for large electric energy production using offshore wind generators and marine current generators, respectively. Thus DFIG based offshore wind farm can be an economic solution to stabilize squirrel cage induction generator based marine current farm without installing any addition FACTS devices. This thesis first focuses on the stabilization of fixed speed IG based marine current farm using SDBR. Also stabilization of DFIG based variable speed wind farm utilizing SDBR is studied in this work. Finally a co-operative control strategy is proposed where DFIG is controlled in such a way that it can even provide necessary reactive power demand of induction generator, so that additional cost of FACTS devices can be avoided. In that way, the DFIGs of the offshore wind farm (OWF) will actively compensate the reactive power demand of adjacent IGs of the marine current farm (MCF) during grid fault. Detailed modeling and control scheme for the proposed system are demonstrated considering some realistic scenarios. The power system small signal stability analysis is also carried out by eigenvalue analysis for marine current generator topology, wind turbine generator topology and integrated topology. The relation between the modes and state variables are discussed in light of modal and sensitivity analyses. The results of theoretical analyses are verified by MATLAB/SIMULINK and laboratory standard power system simulator PSCAD/EMTDC.
A background to risk analysis. Vol. 4
International Nuclear Information System (INIS)
Taylor, J.R.
1979-01-01
This 4-volumes report gives a background of ideas, principles, and examples which might be of use in developing practical methods for risk analysis. Some of the risk analysis techniques described are somewhat experimental. The report is written in an introductory style, but where some point needs further justification or evaluation, this is given in the form of a chapter appendix. In this way, it is hoped that the report can serve two purposes, - as a basis for starting risk analysis work and as a basis for discussing effectiveness of risk analysis procedures. The report should be seen as a preliminary stage, prior to a program of industrial trials of risk analysis methods. Vol. 4 treats human error in plant operation. (BP)
Absolute Stability Analysis of a Phase Plane Controlled Spacecraft
Jang, Jiann-Woei; Plummer, Michael; Bedrossian, Nazareth; Hall, Charles; Jackson, Mark; Spanos, Pol
2010-01-01
Many aerospace attitude control systems utilize phase plane control schemes that include nonlinear elements such as dead zone and ideal relay. To evaluate phase plane control robustness, stability margin prediction methods must be developed. Absolute stability is extended to predict stability margins and to define an abort condition. A constrained optimization approach is also used to design flex filters for roll control. The design goal is to optimize vehicle tracking performance while maintaining adequate stability margins. Absolute stability is shown to provide satisfactory stability constraints for the optimization.
Stability Analysis of a Helicopter with an External Slung Load System
Directory of Open Access Journals (Sweden)
Kary Thanapalan
2016-01-01
Full Text Available This paper describes the stability analysis of a helicopter with an underslung external load system. The Lyapunov second method is considered for the stability analysis. The system is considered as a cascade connection of uncertain nonlinear system. The stability analysis is conducted to ensure the stabilisation of the helicopter system and the positioning of the underslung load at hover condition. Stability analysis and numerical results proved that if desired condition for the stability is met, then it is possible to locate the load at the specified position or its neighbourhood.
Reliability and validity of risk analysis
International Nuclear Information System (INIS)
Aven, Terje; Heide, Bjornar
2009-01-01
In this paper we investigate to what extent risk analysis meets the scientific quality requirements of reliability and validity. We distinguish between two types of approaches within risk analysis, relative frequency-based approaches and Bayesian approaches. The former category includes both traditional statistical inference methods and the so-called probability of frequency approach. Depending on the risk analysis approach, the aim of the analysis is different, the results are presented in different ways and consequently the meaning of the concepts reliability and validity are not the same.
Effects of rapid maxillary expansion on head posture, postural stability, and fall risk
Directory of Open Access Journals (Sweden)
Fatih Celebi
2017-01-01
Full Text Available Objective: The aim of this study was to investigate the effects of rapid maxillary expansion (RME on head posture, postural stability, and fall risk. Materials and Methods: A sample of 51 adolescent patients was randomly divided into two groups. In the first group, which consisted of 28 patients (15 females and 13 males, RME was performed as a part of routine orthodontic treatment. The remaining 23 individuals (12 females and 11 males served as the control group. Lateral cephalometric radiographs taken in natural head position, postural stability, and fall risk scores were obtained during the first visit. They were repeated on average 3.8 months and 3.5 months later for the study and control groups, respectively. The changes were analyzed using the Wilcoxon signed-rank test, paired samples t-test, Mann–Whitney U-test, and independent samples t-test. Results: As a result of RME, a statistically significant decrease was detected in the fall risk score (P < 0.05 in the study group, while the head position and postural stability remained unchanged. For the control group, no significant changes were observed in all measurements. Conclusions: The result of the present study suggests that RME has a capacity of improving fall risk.
Stability analysis of an uncooled segment of superconductor
Energy Technology Data Exchange (ETDEWEB)
Seol, S. Y. [Chonnam National University, Gwangju (Korea, Republic of)
2017-09-15
If the part of the HTS magnet is exposed to the outside of the cryogenic coolant due to the fluctuation of the height of the cooling liquid or the vapor generation, the uncooled part becomes very unstable. In this paper, the unstable equilibrium temperature distribution of the uncooled part of a superconductor is obtained, and the maximum temperature and energy are calculated as a function of the uncooled length. Similar to the superconductor stability problem, the current sharing model was applied to derive the theoretical formula and calculated by numerical integration. We also applied a jump model, which assumes that joule heat is generated in all of the uncooled segment, and compares it with the current sharing model results. As a result of the analysis, the stable equilibrium state and the critical uncooled length in the jump model are not shown in the current sharing model. The stability of the conductors to external disturbances was discussed based on the obtained temperature distribution, maximum temperature, and energy.
Wellbore stability analysis in chemically active shale formations
Directory of Open Access Journals (Sweden)
Shi Xiang-Chao
2016-01-01
Full Text Available Maintaining wellbore stability involves significant challenges when drilling in low-permeability reactive shale formations. In the present study, a non-linear thermo-chemo-poroelastic model is provided to investigate the effect of chemical, thermal, and hydraulic gradients on pore pressure and stress distributions near the wellbores. The analysis indicates that when the solute concentration of the drilling mud is higher than that of the formation fluid, the pore pressure and the effective radial and tangential stresses decrease, and v. v. Cooling of the lower salinity formation decreases the pore pressure, radial and tangential stresses. Hole enlargement is the combined effect of shear and tensile failure when drilling in high-temperature shale formations. The shear and tensile damage indexes reveal that hole enlargement occurs in the vicinity of the wellbore at an early stage of drilling. This study also demonstrates that shale wellbore stability exhibits a time-delay effect due to changes in the pore pressure and stress. The delay time computed with consideration of the strength degradation is far less than that without strength degradation.
Analysis of the stability of events occurred in Laguna Verde
International Nuclear Information System (INIS)
Castillo D, R.; Ortiz V, J.; Calleros M, G.
2005-01-01
The new fuel designs for operation cycles more long have regions of uncertainty bigger that those of the old fuels, and therefore, they can have oscillations of power when an event is presented that causes that the reactor operates to high power and low flow of coolant. During the start up of the reactor there are continued procedures that avoid that oscillations are presented with that which makes sure the stable behavior of the reactor. However, when the reactor is operating to nominal conditions and they are shot or they are transferred to low speed the recirculation pumps, it cannot make sure that the reactor doesn't present oscillations of power when entering to the restricted operation regions. The methods of stability analysis commonly use signs of neutronic noise that require to be stationary, but after a transitory one where they commonly get lost the recirculation pumps the signs they don't have the required characteristics, for what they are used with certain level of uncertainty by the limited validity of the models. In this work the Prony method is used to determine the reactor stability, starting from signs of transitory and it is compared with autoregressive models. Four events are analyzed happened in the Laguna Verde power plant where the reactor was in the area of high power and low flow of coolant, giving satisfactory results. (Author)
Model and Stability Analysis of a Flexible Bladed Rotor
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available This paper presents a fully bladed flexible rotor and outlines the associated stability analysis. From an energetic approach based on the complete energies and potentials for Euler-Bernoulli beams, a system of equations is derived, in the rotational frame, for the rotor. This later one is made of a hollow shaft modelled by an Euler-Bernoulli beam supported by a set of bearings. It is connected to a rigid disk having a rotational inertia. A full set of flexible blades is also modelled by Euler-Bernoulli beams clamped in the disk. The flexural vibrations of the blades as well as those of the shaft are considered. The evolution of the eigenvalues of this rotor, in the corotational frame, is studied. A stability detection method, bringing coalescence and loci separation phenomena to the fore, in case of an asymmetric rotor, is undertaken in order to determine a parametric domain where turbomachinery cannot encounter damage. Finally, extensive parametric studies including the length and the stagger angle of the blades as well as their flexibility are presented in order to obtain robust criteria for stable and unstable areas prediction.
Models and Stability Analysis of Boiling Water Reactors
International Nuclear Information System (INIS)
Dorning, John
2002-01-01
We have studied the nuclear-coupled thermal-hydraulic stability of boiling water reactors (BWRs) using a model that includes: space-time modal neutron kinetics based on spatial w-modes; single- and two-phase flow in parallel boiling channels; fuel rod heat conduction dynamics; and a simple model of the recirculation loop. The BR model is represented by a set of time-dependent nonlinear ordinary differential equations, and is studied as a dynamical system using the modern bifurcation theory and nonlinear dynamical systems analysis. We first determine the stability boundary (SB) - or Hopf bifurcation set- in the most relevant parameter plane, the inlet-subcooling-number/external-pressure-drop plane, for a fixed control rod induced external reactivity equal to the 100% rod line value; then we transform the SB to the practical power-flow map used by BWR operating engineers and regulatory agencies. Using this SB, we show that the normal operating point at 100% power is very stable, that stability of points on the 100% rod line decreases as the flow rate is reduced, and that operating points in the low-flow/high-power region are least stable. We also determine the SB that results when the modal kinetics is replaced by simple point reactor kinetics, and we thereby show that the first harmonic mode does not have a significant effect on the SB. However, we later show that it nevertheless has a significant effect on stability because it affects the basin of attraction of stable operating points. Using numerical simulations we show that, in the important low-flow/high-power region, the Hopf bifurcation that occurs as the SB is crossed is subcritical; hence, growing oscillations can result following small finite perturbations of stable steady-states on the 100% rod line at points in the low-flow/high-power region. Numerical simulations are also performed to calculate the decay ratios (DRs) and frequencies of oscillations for various points on the 100% rod line. It is
Models and Stability Analysis of Boiling Water Reactors
Energy Technology Data Exchange (ETDEWEB)
John Dorning
2002-04-15
We have studied the nuclear-coupled thermal-hydraulic stability of boiling water reactors (BWRs) using a model that includes: space-time modal neutron kinetics based on spatial w-modes; single- and two-phase flow in parallel boiling channels; fuel rod heat conduction dynamics; and a simple model of the recirculation loop. The BR model is represented by a set of time-dependent nonlinear ordinary differential equations, and is studied as a dynamical system using the modern bifurcation theory and nonlinear dynamical systems analysis. We first determine the stability boundary (SB) - or Hopf bifurcation set- in the most relevant parameter plane, the inlet-subcooling-number/external-pressure-drop plane, for a fixed control rod induced external reactivity equal to the 100% rod line value; then we transform the SB to the practical power-flow map used by BWR operating engineers and regulatory agencies. Using this SB, we show that the normal operating point at 100% power is very stable, that stability of points on the 100% rod line decreases as the flow rate is reduced, and that operating points in the low-flow/high-power region are least stable. We also determine the SB that results when the modal kinetics is replaced by simple point reactor kinetics, and we thereby show that the first harmonic mode does not have a significant effect on the SB. However, we later show that it nevertheless has a significant effect on stability because it affects the basin of attraction of stable operating points. Using numerical simulations we show that, in the important low-flow/high-power region, the Hopf bifurcation that occurs as the SB is crossed is subcritical; hence, growing oscillations can result following small finite perturbations of stable steady-states on the 100% rod line at points in the low-flow/high-power region. Numerical simulations are also performed to calculate the decay ratios (DRs) and frequencies of oscillations for various points on the 100% rod line. It is
Risk analysis based on hazards interactions
Rossi, Lauro; Rudari, Roberto; Trasforini, Eva; De Angeli, Silvia; Becker, Joost
2017-04-01
Despite an increasing need for open, transparent, and credible multi-hazard risk assessment methods, models, and tools, the availability of comprehensive risk information needed to inform disaster risk reduction is limited, and the level of interaction across hazards is not systematically analysed. Risk assessment methodologies for different hazards often produce risk metrics that are not comparable. Hazard interactions (consecutive occurrence two or more different events) are generally neglected, resulting in strongly underestimated risk assessment in the most exposed areas. This study presents cases of interaction between different hazards, showing how subsidence can affect coastal and river flood risk (Jakarta and Bandung, Indonesia) or how flood risk is modified after a seismic event (Italy). The analysis of well documented real study cases, based on a combination between Earth Observation and in-situ data, would serve as basis the formalisation of a multi-hazard methodology, identifying gaps and research frontiers. Multi-hazard risk analysis is performed through the RASOR platform (Rapid Analysis and Spatialisation Of Risk). A scenario-driven query system allow users to simulate future scenarios based on existing and assumed conditions, to compare with historical scenarios, and to model multi-hazard risk both before and during an event (www.rasor.eu).
Stability analysis for an age-dependent vaccination model
International Nuclear Information System (INIS)
El-Doma, M.
1993-05-01
The stability of an SIR epidemic model with vaccination is investigated. We determine the steady states and examine their stability. Furthermore, a critical vaccination coverage that will eventually eradicate the disease is determined. (author). 9 refs
International Nuclear Information System (INIS)
Mazur, A.
1985-01-01
Risk-benefit analysis has become popular in the past decade as a means of improving decision making, especially in the area of technology policy. Here risk-benefit analysis is compared to other (equally defensible) approaches to decision making, showing how it favors some political interests more than others, and suggesting why it has recently come to the fore as a tool of political analysis. A considerable portion of the discussion concerns nuclear power. 6 references
Modeling and Stability Analysis of Wedge Clutch System
Directory of Open Access Journals (Sweden)
Jian Yao
2014-01-01
Full Text Available A wedge clutch with unique features of self-reinforcement and small actuation force was designed. Its self-reinforcement feature, associated with different factors such as the wedge angle and friction coefficient, brings different dynamics and unstable problem with improper parameters. To analyze this system, a complete mathematical model of the actuation system is built, which includes the DC motor, the wedge mechanism, and the actuated clutch pack. By considering several nonlinear factors, such as the slip-stick friction and the contact or not of the clutch plates, the system is piecewise linear. Through the stability analysis of the linearized system in clutch slipping phase, the stable condition of the designed parameters is obtained as α>arctan(μc. The mathematical model of the actuation system is validated by prototype testing. And with the validated model, the system dynamics in both stable and unstable conditions is investigated and discussed in engineering side.
Quantitative Analysis and Stability of the Rodenticide TETS ...
Journal Article The determination of the rodenticide tetramethylenedisulfotetramine (TETS) in drinking water is reportable through the use of automated sample preparation via solid phase extraction and detection using isotope dilution gas chromatography-mass spectrometry. The method was characterized over twenty-two analytical batches with quality control samples. Accuracies for low and high concentration quality control pools were 100 and 101%, respectively. The minimum reporting level (MRL) for TETS in this method is 0.50 ug/L. Five drinking waters representing a range of water quality parameters and disinfection practices were fortified with TETS at ten times the MRL and analyzed over a 28 day period to determine the stability of TETS in these waters. The amount of TETS measured in these samples averaged 100 ± 6% of the amount fortified suggesting that tap water samples may be held for up to 28 days prior to analysis.
Dynamic Stability Analysis Using High-Order Interpolation
Directory of Open Access Journals (Sweden)
Juarez-Toledo C.
2012-10-01
Full Text Available A non-linear model with robust precision for transient stability analysis in multimachine power systems is proposed. The proposed formulation uses the interpolation of Lagrange and Newton's Divided Difference. The High-Order Interpolation technique developed can be used for evaluation of the critical conditions of the dynamic system.The technique is applied to a 5-area 45-machine model of the Mexican interconnected system. As a particular case, this paper shows the application of the High-Order procedure for identifying the slow-frequency mode for a critical contingency. Numerical examples illustrate the method and demonstrate the ability of the High-Order technique to isolate and extract temporal modal behavior.
Robust stability analysis of adaptation algorithms for single perceptron.
Hui, S; Zak, S H
1991-01-01
The problem of robust stability and convergence of learning parameters of adaptation algorithms in a noisy environment for the single preceptron is addressed. The case in which the same input pattern is presented in the adaptation cycle is analyzed. The algorithm proposed is of the Widrow-Hoff type. It is concluded that this algorithm is robust. However, the weight vectors do not necessarily converge in the presence of measurement noise. A modified version of this algorithm in which the reduction factors are allowed to vary with time is proposed, and it is shown that this algorithm is robust and that the weight vectors converge in the presence of bounded noise. Only deterministic-type arguments are used in the analysis. An ultimate bound on the error in terms of a convex combination of the initial error and the bound on the noise is obtained.
A new method for tear film stability analysis using videokeratography.
Goto, Tomoko; Zheng, Xiaodong; Klyce, Stephen D; Kataoka, Hisashi; Uno, Toshihiko; Karon, Mike; Tatematsu, Yoshiyuki; Bessyo, Takeo; Tsubota, Kazuo; Ohashi, Yuichi
2003-05-01
To report a new tear film stability analysis system using videokeratography. Observational case series. New videokeratography software for TMS-2N (topographic modeling system; TOMEY Corporation, Nagoya, Japan) was developed that can automatically capture consecutive corneal surface images every second for 10 seconds. Forty-eight adult volunteers (80 eyes) were recruited for this study, and all subjects were examined with the new system. Corneal topographs were analyzed for tear breakup time (TMS-BUT) and the ratio of breakup area to entire color-code area (TMS-BUA) was calculated. Routine methods for tear film breakup time evaluation using slit-lamp microscope and fluorescence staining (SLE-BUT) were performed for comparison purposes. Regressive correlations of TMS-BUT or TMS-BUA with SLE-BUT were analyzed. Based on SLE results, subjects were separated into two groups with normal and short BUT, respectively. TMS-BUT and TMS-BUA were compared with SLE-BUT data with regard to the sensitivity and specificity of evaluation of dry eye symptoms. Topographic modeling system-tear breakup time (TMS-BUT) had a positive correlation with SLE-BUT (R = 0.7219, P TMS-BUA showed a negative correlation (R = 0.6317, P TMS-BUT, 9 (81.82%) of which were associated with dry eye symptoms. The sensitivities of TMS-BUT and TMS-BUA were 97.5% and 95%, respectively, significantly higher than that of SLE-BUT (75%), with P =.008 and 0.01, respectively. Topographic modeling system-BUT and TMS-BUA displayed a similar rate of specificity in comparison with SLE-BUT. This new videokeratography system is a noninvasive and objective method with increased sensitivity for tear film stability analysis.
Risk Analysis for Agricultural Cooperatives
Kenkel, Philip L.; Parrish, Robert
2013-01-01
Grain/fertilizer volumes are major risks for grain/supply cooperatives followed by fertilizer and fuel margins. Operating losses force stock write downs (22% probability) and negative cashflow (15% probability). Decisions on cash and stock patronage, infrastructure investment, and equity retirement improve member returns but increase stock write downs and negative cashflow probability
Linear stability analysis of Clarke-Riley diffusion flames
Gomez-Lendinez, Daniel; Coenen, Wilfried; Sanchez, Antonio L.
2016-11-01
The buoyancy-driven laminar flow associated with the Burke-Schumann diffusion flame developing from the edge of a semi-infinite horizontal fuel surface burning in a quiescent oxidizing atmosphere displays a self-similar structure, first described by Clarke and Riley (Journal of Fluid Mechanics, 74:415-431). Their analysis was performed for unity reactant Lewis numbers, with the viscosity and thermal conductivity taken to be linearly proportional to the temperature. Our work extends this seminal work by considering fuels with non-unity Lewis numbers and gas mixtures with a realistic power-law dependence of the different transport properties. The problem is formulated in terms of chemistry-free, Shvab-Zel'dovich, linear combinations of the temperature and reactant mass fractions, not changed directly by the reactions, as conserved scalars. The resulting self-similar base-flow solution is used in a linear stability analysis to determine the critical value of the boundary-layer thickness-measured by the local Grashof number-at which the flow becomes unstable, leading to the development of Görtler-like streamwise vortices. The analysis provides the dependence of the critical Grashof number on the relevant flame parameters.
Effects of Outlets on Cracking Risk and Integral Stability of Super-High Arch Dams
Lin, Peng; Liu, Hongyuan; Li, Qingbin; Hu, Hang
2014-01-01
In this paper, case study on outlet cracking is first conducted for the Goupitan and Xiaowan arch dams. A nonlinear FEM method is then implemented to study effects of the outlets on integral stability of the Xiluodu arch dam under two loading conditions, i.e., normal loading and overloading conditions. On the basis of the case study and the numerical modelling, the outlet cracking mechanism, risk, and corresponding reinforcement measures are discussed. Furthermore, the numerical simulation re...
Sadri, Sobhan; Wu, Christine
2013-06-01
For the first time, this paper investigates the application of the concept of Lyapunov exponents to the stability analysis of the nonlinear vehicle model in plane motion with two degrees of freedom. The nonlinearity of the model comes from the third-order polynomial expression between the lateral forces on the tyres and the tyre slip angles. Comprehensive studies on both system and structural stability analyses of the vehicle model are presented. The system stability analysis includes the stability, lateral stability region, and effects of driving conditions on the lateral stability region of the vehicle model in the state space. In the structural stability analysis, the ranges of driving conditions in which the stability of the vehicle model is guaranteed are given. Moreover, through examples, the largest Lyapunov exponent is suggested as an indicator of the convergence rate in which the disturbed vehicle model returns to its stable fixed point.
Directory of Open Access Journals (Sweden)
Ernesto Mordecki
2013-06-01
Full Text Available Some emergent economies present a high financial dollarization in loans and deposits, generating a specific risk in the banking activity. We quantify this exchange credit risk as the price of an option equivalent to this loan, and discuss the financial stability implications due to the (implicit issuance of these options. The exchange rate is modeled through a Levy process. The depth of the market depends on the type of the currencies involved. Whenever possible, we depart from option prices to calibrate a model, like in the EUR/USD market. But if the market is not liquid, as the USD/UYU market, we provide alternative pricing methodologies.
Initial Risk Analysis and Decision Making Framework
Energy Technology Data Exchange (ETDEWEB)
Engel, David W.
2012-02-01
Commercialization of new carbon capture simulation initiative (CCSI) technology will include two key elements of risk management, namely, technical risk (will process and plant performance be effective, safe, and reliable) and enterprise risk (can project losses and costs be controlled within the constraints of market demand to maintain profitability and investor confidence). Both of these elements of risk are incorporated into the risk analysis subtask of Task 7. Thus far, this subtask has developed a prototype demonstration tool that quantifies risk based on the expected profitability of expenditures when retrofitting carbon capture technology on a stylized 650 MW pulverized coal electric power generator. The prototype is based on the selection of specific technical and financial factors believed to be important determinants of the expected profitability of carbon capture, subject to uncertainty. The uncertainty surrounding the technical performance and financial variables selected thus far is propagated in a model that calculates the expected profitability of investments in carbon capture and measures risk in terms of variability in expected net returns from these investments. Given the preliminary nature of the results of this prototype, additional work is required to expand the scope of the model to include additional risk factors, additional information on extant and proposed risk factors, the results of a qualitative risk factor elicitation process, and feedback from utilities and other interested parties involved in the carbon capture project. Additional information on proposed distributions of these risk factors will be integrated into a commercial implementation framework for the purpose of a comparative technology investment analysis.
RISK ANALYSIS, ANALYSIS OF VARIANCE: GETTING MORE FROM OUR DATA
Analysis of variance (ANOVA) and regression are common statistical techniques used to analyze agronomic experimental data and determine significant differences among yields due to treatments or other experimental factors. Risk analysis provides an alternate and complimentary examination of the same...
Safety analysis, risk assessment, and risk acceptance criteria
International Nuclear Information System (INIS)
Jamali, K.
1997-01-01
This paper discusses a number of topics that relate safety analysis as documented in the Department of Energy (DOE) safety analysis reports (SARs), probabilistic risk assessments (PRA) as characterized primarily in the context of the techniques that have assumed some level of formality in commercial nuclear power plant applications, and risk acceptance criteria as an outgrowth of PRA applications. DOE SARs of interest are those that are prepared for DOE facilities under DOE Order 5480.23 and the implementing guidance in DOE STD-3009-94. It must be noted that the primary area of application for DOE STD-3009 is existing DOE facilities and that certain modifications of the STD-3009 approach are necessary in SARs for new facilities. Moreover, it is the hazard analysis (HA) and accident analysis (AA) portions of these SARs that are relevant to the present discussions. Although PRAs can be qualitative in nature, PRA as used in this paper refers more generally to all quantitative risk assessments and their underlying methods. HA as used in this paper refers more generally to all qualitative risk assessments and their underlying methods that have been in use in hazardous facilities other than nuclear power plants. This discussion includes both quantitative and qualitative risk assessment methods. PRA has been used, improved, developed, and refined since the Reactor Safety Study (WASH-1400) was published in 1975 by the Nuclear Regulatory Commission (NRC). Much debate has ensued since WASH-1400 on exactly what the role of PRA should be in plant design, reactor licensing, 'ensuring' plant and process safety, and a large number of other decisions that must be made for potentially hazardous activities. Of particular interest in this area is whether the risks quantified using PRA should be compared with numerical risk acceptance criteria (RACs) to determine whether a facility is 'safe.' Use of RACs requires quantitative estimates of consequence frequency and magnitude
[Import risk analysis in animal disease control].
Hauser, Ruth; Breidenbach, Eric; Thür, Barbara; Griot, Christian; Engels, Monika; Stärk, Katharina
2004-01-01
At the Swiss Federal Veterinary Office risk analyses are conducted according to international standards. A risk analysis contains the elements risk management, risk assessment and risk communication. A risk assessment is based on risk profile, hazard identification and a pathway model. All available information is gathered, documented and assessed and the risk estimated. The question. "What is the probability that unprocessed wild boar meat imported to Switzerland from the federal state Mecklenburg Western Pommerania is contaminated with classical swine fever virus?" was answered by a release assessment. The hazard identification recognized classical swine fever virus and attenuated live virus vaccine used for oral immunization as hazards. The probability of contamination was estimated to be small. The question: "What is the likelihood to introduce Aujeszky's disease to Switzerland and infect the indigenous pig population with the disease, by means of importing pork and meat products?" was answered by assessing the release, exposure and resulting consequences. The risk of an infection of the indigenous pig population was estimated to be very small, as 80% of the imported products derive from countries or zones free from Aujeszky's disease. Furthermore the majority of the imported products are processed. The strict implementation of the regulations governing feeding of food wastes to pigs reduces the probability of exposure. In all assessments the risk management decides on a strategy to deal with the risk, taking into consideration the results and recommendations derived from the risk assessment as well as other relevant factors.
Gender Analysis of Risk in Innovation System
DEFF Research Database (Denmark)
Ayinde, Ope; Muchie, Mammo; Abaniyan, E. O.
2011-01-01
This study analyzed risk by gender in innovation in Kwara state, Nigeria, using downy mildew resistant maize production as case study. The study employed primary and secondary data. The primary data were collected from well-structured questionnaires administered to both male and female producing...... the new maize variety. The analytical tools used include descriptive statistics, regression model; risk utility functions and risk parameter analysis. The result showed that invasion by animals, disease and pest, lack of access to credit wind and price fluctuation were the major risk facing the maize...... of the producers was risk averse. Gender was found responsible for the level of risk involve in the new variety maize production. Other factors that were found responsible for their level of risk involved in the production include age, position held in the society and farm size. Finally, the study recommends...
GIS risk analysis of hazardous materials transport
International Nuclear Information System (INIS)
Anders, C.; Olsten, J.
1991-01-01
The Geographic Information System (GIS) was used to assess the risks and vulnerability of transporting hazardous materials and wastes (such as gasoline, explosives, poisons, etc) on the Arizona highway system. This paper discusses the methodology that was utilized, and the application of GIS systems to risk analysis problems
Extractive waste management: A risk analysis approach.
Mehta, Neha; Dino, Giovanna Antonella; Ajmone-Marsan, Franco; Lasagna, Manuela; Romè, Chiara; De Luca, Domenico Antonio
2018-05-01
Abandoned mine sites continue to present serious environmental hazards because the heavy metals associated with extractive waste are continuously released into the environment, where they threaten human life and the environment. Remediating and securing extractive waste are complex, lengthy and costly processes. Thus, in most European countries, a site is considered for intervention when it poses a risk to human health and the surrounding environment. As a consequence, risk analysis presents a viable decisional approach towards the management of extractive waste. To evaluate the effects posed by extractive waste to human health and groundwater, a risk analysis approach was used for an abandoned nickel extraction site in Campello Monti in North Italy. This site is located in the Southern Italian Alps. The area consists of large and voluminous mafic rocks intruded by mantle peridotite. The mining activities in this area have generated extractive waste. A risk analysis of the site was performed using Risk Based Corrective Action (RBCA) guidelines, considering the properties of extractive waste and water for the properties of environmental matrices. The results showed the presence of carcinogenic risk due to arsenic and risks to groundwater due to nickel. The results of the risk analysis form a basic understanding of the current situation at the site, which is affected by extractive waste. Copyright © 2017 Elsevier B.V. All rights reserved.
Project cost analysis under risk
Directory of Open Access Journals (Sweden)
Florica LUBAN
2010-12-01
Full Text Available In this paper, an integrated approach based on Monte Carlo simulation and Six Sigma methodology is used to analyze the risk associated with a project's total cost. Monte Carlo simulation is applied to understand the variability in total cost caused by the probabilistic cost items. By Six Sigma methodology the range of variation of the project cost can be reduced by operating on the input factors with the greatest impact on total cost to cover the variation of 6 between the limits that were established in the design phase of Six Sigma.
Dealing with phenomenological uncertainty in risk analysis
International Nuclear Information System (INIS)
Theofanous, T.G.
1994-01-01
The Risk-Oriented Accident Analysis Methodology (ROAAM) is summarized and developed further towards a formal definition. The key ideas behind the methodology and these more formal aspects are also presented and discussed
Comprehensive risk analysis for structure type selection.
2010-04-01
Optimization of bridge selection and design traditionally has been sought in terms of the finished structure. This study presents a : more comprehensive risk-based analysis that includes user costs and accidents during the construction phase. Costs f...
Risk and safety analysis of nuclear systems
National Research Council Canada - National Science Library
Lee, John C; McCormick, Norman J
2011-01-01
.... The first half of the book covers the principles of risk analysis, the techniques used to develop and update a reliability data base, the reliability of multi-component systems, Markov methods used...
Frequency prediction by linear stability analysis around mean flow
Bengana, Yacine; Tuckerman, Laurette
2017-11-01
The frequency of certain limit cycles resulting from a Hopf bifurcation, such as the von Karman vortex street, can be predicted by linear stability analysis around their mean flows. Barkley (2006) has shown this to yield an eigenvalue whose real part is zero and whose imaginary part matches the nonlinear frequency. This property was named RZIF by Turton et al. (2015); moreover they found that the traveling waves (TW) of thermosolutal convection have the RZIF property. They explained this as a consequence of the fact that the temporal Fourier spectrum is dominated by the mean flow and first harmonic. We could therefore consider that only the first mode is important in the saturation of the mean flow as presented in the Self-Consistent Model (SCM) of Mantic-Lugo et al. (2014). We have implemented a full Newton's method to solve the SCM for thermosolutal convection. We show that while the RZIF property is satisfied far from the threshold, the SCM model reproduces the exact frequency only very close to the threshold. Thus, the nonlinear interaction of only the first mode with itself is insufficiently accurate to estimate the mean flow. Our next step will be to take into account higher harmonics and to apply this analysis to the standing waves, for which RZIF does not hold.
Analysis on soil compressibility changes of samples stabilized with lime
Directory of Open Access Journals (Sweden)
Elena-Andreea CALARASU
2016-12-01
Full Text Available In order to manage and control the stability of buildings located on difficult foundation soils, several techniques of soil stabilization were developed and applied worldwide. Taking into account the major significance of soil compressibility on construction durability and safety, the soil stabilization with a binder like lime is considered one of the most used and traditional methods. The present paper aims to assess the effect of lime content on soil geotechnical parameters, especially on compressibility ones, based on laboratory experimental tests, for several soil categories in admixture with different lime dosages. The results of this study indicate a significant improvement of stabilized soil parameters, such as compressibility and plasticity, in comparison with natural samples. The effect of lime stabilization is related to an increase of soil structure stability by increasing the bearing capacity.
Guo, Fangjian; Garvey, W Timothy
2016-02-01
To assess the stability of metabolic status and body mass index (BMI) status and their relative contribution to risk of diabetes, cardiovascular events, and mortality. A total of 14,685 participants from the Atherosclerosis Risk in Communities Study and 4,990 from the Coronary Artery Risk Development in Young Adults Study were included. People with healthy obesity (HO) are defined as those meeting all three indices of blood pressure, blood glucose, and blood lipids. People with unhealthy obesity crossed the risk threshold for all three criteria. In both healthy and unhealthy subgroups, risks for coronary heart disease (CHD), stroke, and mortality were comparable among BMI status during a mean 18.7-year follow-up. When compared with HO, hazard ratios were increased for diabetes (5.56, 95% confidence interval [CI] 4.12-7.48), CHD (5.60, 95% CI 3.14-9.98), stroke (4.84, 95% CI 2.13-10.97), and mortality (2.6, 95% CI 1.88-3.61) in people with unhealthy obesity. BMI only moderately increased the risks for diabetes among healthy subjects. In the Coronary Artery Risk Development in Young Adults Study over 20 years, 17.5% of lean subjects and 67.3% of overweight subjects at baseline developed obesity during follow-up. Despite rising BMI, metabolic status remained relatively stable. Metabolic status is relatively stable despite rising BMI. HO had lower risks for diabetes, CHD, stroke, and mortality than unhealthy subjects but increased diabetes risks than healthy lean people. Cardiometabolic risk factors confer much higher risk than obesity per se. © 2015 The Obesity Society.
Stability analysis of distributed order fractional chen system.
Aminikhah, H; Refahi Sheikhani, A; Rezazadeh, H
2013-01-01
We first investigate sufficient and necessary conditions of stability of nonlinear distributed order fractional system and then we generalize the integer-order Chen system into the distributed order fractional domain. Based on the asymptotic stability theory of nonlinear distributed order fractional systems, the stability of distributed order fractional Chen system is discussed. In addition, we have found that chaos exists in the double fractional order Chen system. Numerical solutions are used to verify the analytical results.
Stability Analysis of Distributed Order Fractional Chen System
Aminikhah, H.; Refahi Sheikhani, A.; Rezazadeh, H.
2013-01-01
We first investigate sufficient and necessary conditions of stability of nonlinear distributed order fractional system and then we generalize the integer-order Chen system into the distributed order fractional domain. Based on the asymptotic stability theory of nonlinear distributed order fractional systems, the stability of distributed order fractional Chen system is discussed. In addition, we have found that chaos exists in the double fractional order Chen system. Numerical solutions are used to verify the analytical results. PMID:24489508
A small - signal stability analysis of DFIG wind generation
Vittal, Eknath; O'Malley, Mark; Keane, Andrew
2009-01-01
This paper examines the small-signal stability impacts of high penetrations of doubly-fed induction generator (DFIG) wind turbines on power systems. It provides a basic overview of small-signal stability concepts and then examines the response of DFIG generation to two local contingency event. Using the New England 39 bus test system, this paper will demonstrate the stability implications of DFIG turbines utilizing terminal voltage control and fixed power factor control in response...
Agroecological Zoning of Wheat in Khorasan ProvinceRisk Analysis
Directory of Open Access Journals (Sweden)
M. Nassiri Mahallati
2011-01-01
Full Text Available Abstract In crop zonation studies potential yield is usually estimated by simulation models where management inputs are defined as recommended by research stations. However, these recommendations are not necessarily in accord with the local situation. Therefore, the prediction of simulation models is subjected to uncertainty or risk. In this research the risk of wheat yield estimation due to management inputs in Khorasan provinces is analysed by application of Monte Carlo simulation. Potential wheat yield was estimated by WOFOST model which was previously validated against the experimental data. The results of sensitivity analysis indicated that change in planting date in order of ±50 days relative to a reference sowing date resulted in a drastic variation in estimated wheat yield. However, potential wheat yield was not sensitive to variation in planting density in the range of ±50% of the reference density. Therefore, risk analysis was performed on planting date. 100 random planting dates were generated using a random data generator software and the WOFOST model was run for each generated date during 10 climatic years (1375-1385. Using the simulation results probability distribution of potential wheat yield was calculated for recommended planting date and dates with ±15 or ±30 days deviation. The results showed that risk of wheat yield in response to change in planting date was different between provinces. In the Northern Khorasan province earlier planting by 15 days compared to the average recommended date led to risk reduction while wheat yield was more risky when planting date was delayed by 30 days. In Khorasan Razavi province the recommended planting date resulted in lower risk but yield risk was increased by earlier planting. In Southern Khorasan province wheat yield was subjected to minimum risk and higher stability when the recommended planting date was delayed by 30 days. It was concluded that the low potential wheat yield
Analysis of Physical Education Students’ Emotional Stability and Reactibility
Directory of Open Access Journals (Sweden)
Radka Peřinová
2015-03-01
Full Text Available Analysis of Physical Education Students’ Emotional Stability and Reactibility This paper will aim to show the possible association between emotional stability and reaction time variability of Physical Education students. It can be stated that our study confirmed our suppositions which were based on works that have focused on similar topics. Our research sample showed the expected characteristics: primarily lower neuroticism values and higher extraversion when compared to the non-sporting population. Emotional stability which was reflected in the neuroticism dimension in EPQ-R (Eysenck Personality Questionnaire was shown to be connected with variability of the reaction time in the test of reactability to selected visual stimulus, disregarding the reaction rate. The effect of extraversion is partly reflected by the tendency of the sanguine temperament type to react in a balanced manner (i.e. with low reaction time variability during the reactability test. Due to the relatively low number of other temperament types in our sample, it is not possible to draw any conclusions in this regard. Analýza emocionální stability a reaktibility studentů tělesné výchovy Tento příspěvek poukazuje na možnou asociaci mezi emocionální stabilitou a časovou variabilitou dob reakcí u studentů tělesné výchovy. Lze konstatovat, že studie potvrdila naše předpoklady vycházející z odborných prací na obdobná témata. Výzkumný soubor vykazoval předpokládané charakteristiky, především nižších hodnot neuroticismu a vyšší extroverze oproti nesportující populaci. Emocionální stabilita vyjádřená pomocí dimenze neuroticismu (v EPQ-R se ukázala v asociaci s časovou variabilitou dob reakcí v testu reaktibility na výběrový zrakový podnět bez ohledu na rychlost reakce. Vliv extroverze do jisté míry odráží naznačená tendence sangvinického typu temperamentu reagovat vyrovnaně (tedy s nízkou časovou variabilitou dob
Probabilistic risk analysis in chemical engineering
International Nuclear Information System (INIS)
Schmalz, F.
1991-01-01
In risk analysis in the chemical industry, recognising potential risks is considered more important than assessing their quantitative extent. Even in assessing risks, emphasis is not on the probability involved but on the possible extent. Qualitative assessment has proved valuable here. Probabilistic methods are used in individual cases where the wide implications make it essential to be able to assess the reliability of safety precautions. In this case, assessment therefore centres on the reliability of technical systems and not on the extent of a chemical risk. 7 figs
In situ vitrification: application analysis for stabilization of transuranic waste
Energy Technology Data Exchange (ETDEWEB)
Oma, K.H.; Farnsworth, R.K.; Rusin, J.M.
1982-09-01
The in situ vitrification process builds upon the electric melter technology previously developed for high-level waste immobilization. In situ vitrification converts buried wastes and contaminated soil to an extremely durable glass and crystalline waste form by melting the materials, in place, using joule heating. Once the waste materials have been solidified, the high integrity waste form should not cause future ground subsidence. Environmental transport of the waste due to water or wind erosion, and plant or animal intrusion, is minimized. Environmental studies are currently being conducted to determine whether additional stabilization is required for certain in-ground transuranic waste sites. An applications analysis has been performed to identify several in situ vitrification process limitations which may exist at transuranic waste sites. Based on the process limit analysis, in situ vitrification is well suited for solidification of most in-ground transuranic wastes. The process is best suited for liquid disposal sites. A site-specific performance analysis, based on safety, health, environmental, and economic assessments, will be required to determine for which sites in situ vitrification is an acceptable disposal technique. Process economics of in situ vitrification compare favorably with other in-situ solidification processes and are an order of magnitude less than the costs for exhumation and disposal in a repository. Leachability of the vitrified product compares closely with that of Pyrex glass and is significantly better than granite, marble, or bottle glass. Total release to the environment from a vitrified waste site is estimated to be less than 10/sup -5/ parts per year. 32 figures, 30 tables.
In situ vitrification: application analysis for stabilization of transuranic waste
International Nuclear Information System (INIS)
Oma, K.H.; Farnsworth, R.K.; Rusin, J.M.
1982-09-01
The in situ vitrification process builds upon the electric melter technology previously developed for high-level waste immobilization. In situ vitrification converts buried wastes and contaminated soil to an extremely durable glass and crystalline waste form by melting the materials, in place, using joule heating. Once the waste materials have been solidified, the high integrity waste form should not cause future ground subsidence. Environmental transport of the waste due to water or wind erosion, and plant or animal intrusion, is minimized. Environmental studies are currently being conducted to determine whether additional stabilization is required for certain in-ground transuranic waste sites. An applications analysis has been performed to identify several in situ vitrification process limitations which may exist at transuranic waste sites. Based on the process limit analysis, in situ vitrification is well suited for solidification of most in-ground transuranic wastes. The process is best suited for liquid disposal sites. A site-specific performance analysis, based on safety, health, environmental, and economic assessments, will be required to determine for which sites in situ vitrification is an acceptable disposal technique. Process economics of in situ vitrification compare favorably with other in-situ solidification processes and are an order of magnitude less than the costs for exhumation and disposal in a repository. Leachability of the vitrified product compares closely with that of Pyrex glass and is significantly better than granite, marble, or bottle glass. Total release to the environment from a vitrified waste site is estimated to be less than 10 -5 parts per year. 32 figures, 30 tables
Stability analysis of a boundary layer over a hump using parabolized stability equations
Energy Technology Data Exchange (ETDEWEB)
Gao, B; Park, D H; Park, S O, E-mail: sopark@kaist.ac.kr [Division of Aerospace Engineering, Korea Advanced Institute of Science and Technology, Gusong-dong, Yusong-gu, Daejeon 305-701 (Korea, Republic of)
2011-10-15
Parabolized stability equations (PSEs) were used to investigate the stability of boundary layer flows over a small hump. The applicability of PSEs to flows with a small separation bubble was examined by comparing the result with DNS data. It was found that PSEs can efficiently track the disturbance waves with an acceptable accuracy in spite of a small separation bubble. A typical evolution scenario of Tollmien-Schlichting (TS) wave is presented. The adverse pressure gradient and the flow separation due to the hump have a strong effect on the amplification of the disturbances. The effect of hump width and height is also examined. When the width of the hump is reduced, the amplification factor is increased. The height of the hump is found to obviously influence the stability only when it is greater than the critical layer thickness.
Stability analysis of a boundary layer over a hump using parabolized stability equations
International Nuclear Information System (INIS)
Gao, B; Park, D H; Park, S O
2011-01-01
Parabolized stability equations (PSEs) were used to investigate the stability of boundary layer flows over a small hump. The applicability of PSEs to flows with a small separation bubble was examined by comparing the result with DNS data. It was found that PSEs can efficiently track the disturbance waves with an acceptable accuracy in spite of a small separation bubble. A typical evolution scenario of Tollmien-Schlichting (TS) wave is presented. The adverse pressure gradient and the flow separation due to the hump have a strong effect on the amplification of the disturbances. The effect of hump width and height is also examined. When the width of the hump is reduced, the amplification factor is increased. The height of the hump is found to obviously influence the stability only when it is greater than the critical layer thickness.
Reliability and risk analysis methods research plan
International Nuclear Information System (INIS)
1984-10-01
This document presents a plan for reliability and risk analysis methods research to be performed mainly by the Reactor Risk Branch (RRB), Division of Risk Analysis and Operations (DRAO), Office of Nuclear Regulatory Research. It includes those activities of other DRAO branches which are very closely related to those of the RRB. Related or interfacing programs of other divisions, offices and organizations are merely indicated. The primary use of this document is envisioned as an NRC working document, covering about a 3-year period, to foster better coordination in reliability and risk analysis methods development between the offices of Nuclear Regulatory Research and Nuclear Reactor Regulation. It will also serve as an information source for contractors and others to more clearly understand the objectives, needs, programmatic activities and interfaces together with the overall logical structure of the program
Intentional risk management through complex networks analysis
Chapela, Victor; Moral, Santiago; Romance, Miguel
2015-01-01
This book combines game theory and complex networks to examine intentional technological risk through modeling. As information security risks are in constant evolution, the methodologies and tools to manage them must evolve to an ever-changing environment. A formal global methodology is explained in this book, which is able to analyze risks in cyber security based on complex network models and ideas extracted from the Nash equilibrium. A risk management methodology for IT critical infrastructures is introduced which provides guidance and analysis on decision making models and real situations. This model manages the risk of succumbing to a digital attack and assesses an attack from the following three variables: income obtained, expense needed to carry out an attack, and the potential consequences for an attack. Graduate students and researchers interested in cyber security, complex network applications and intentional risk will find this book useful as it is filled with a number of models, methodologies a...
Systematic analysis of stability patterns in plant primary metabolism.
Directory of Open Access Journals (Sweden)
Dorothee Girbig
Full Text Available Metabolic networks are characterized by complex interactions and regulatory mechanisms between many individual components. These interactions determine whether a steady state is stable to perturbations. Structural kinetic modeling (SKM is a framework to analyze the stability of metabolic steady states that allows the study of the system Jacobian without requiring detailed knowledge about individual rate equations. Stability criteria can be derived by generating a large number of structural kinetic models (SK-models with randomly sampled parameter sets and evaluating the resulting Jacobian matrices. Until now, SKM experiments applied univariate tests to detect the network components with the largest influence on stability. In this work, we present an extended SKM approach relying on supervised machine learning to detect patterns of enzyme-metabolite interactions that act together in an orchestrated manner to ensure stability. We demonstrate its application on a detailed SK-model of the Calvin-Benson cycle and connected pathways. The identified stability patterns are highly complex reflecting that changes in dynamic properties depend on concerted interactions between several network components. In total, we find more patterns that reliably ensure stability than patterns ensuring instability. This shows that the design of this system is strongly targeted towards maintaining stability. We also investigate the effect of allosteric regulators revealing that the tendency to stability is significantly increased by including experimentally determined regulatory mechanisms that have not yet been integrated into existing kinetic models.
Stability analysis of a class of fractional delay differential equations
Indian Academy of Sciences (India)
In this paper we analyse stability of nonlinear fractional order delay differential equations of the form D y ( t ) = a f ( y ( t − ) ) − by ( t ) , where D is a Caputo fractional derivative of order 0 < ≤ 1. We describe stability regions using critical curves. To explain the proposed theory, we discuss fractional order logistic ...
Stability analysis of a class of fractional delay differential equations
Indian Academy of Sciences (India)
Abstract. In this paper we analyse stability of nonlinear fractional order delay differential equa- tions of the form Dα y(t) = af (y(t − τ )) − by(t), where Dα is a Caputo fractional derivative of order 0 < α ≤ 1. We describe stability regions using critical curves. To explain the proposed theory, we discuss fractional order logistic ...
Analysis of the Gyroscopic Stability of the Wheelset
Directory of Open Access Journals (Sweden)
Hao Dong
2014-01-01
Full Text Available The wheelset of the railway vehicle is a rotor which itself has gyroscopic effect. Nowadays, the rolling stock has entered the era of high speed, and the wheel rotates faster than in the past. The influence of gyroscopic effect on stability is little understood. Metelitsyn’s inequality theorem for asymptotic stability has some advantages to analyze this problem although this method is sufficient but not necessary condition. Based on its deduction, the extremal eigenvalues criterion and compared with Routh-Hurwitz criterion, both are applied to solve the critical value of speed. Further, according to the instability criterion, gyroscopic contributory ratio is derived to study how the role the gyroscopic effect plays in stability. Moreover, the effect of gyroscopic matrix or gyroscopic terms pitch rotor inertia Iy on stability coefficient is investigated. The results show that Iy is a key factor to wheelset gyroscopic stability. The gyroscopic effect becomes significant, and the stability increases with increasing Iy. The results also indicate that the critical value of speed solved by Metelitsyn theorem is more conservative than the one it solved by Hurwitz criterion, which proves that Metelitsyn inequality theorem for asymptotic stability is a sufficient but not necessary condition in the way of attaining the numerical simulation result. Finally, the test for the influence of gyroscopic effect on stability needs to be further studied.
Application of Lyapunov's Second Method in the Stability Analysis of ...
African Journals Online (AJOL)
In this paper, Lyapunov's method for determining the stability of non-linear systems under dynamic states is presented. The paper highlights a practical application of the method to investigate the stability of crude oil/natural gas separation process. Mathematical state models for the separation process, used in the ...
Improving Power System Stability Using Transfer Function: A Comparative Analysis
Directory of Open Access Journals (Sweden)
G. Shahgholian
2017-10-01
Full Text Available In this paper, a small-signal dynamic model of a single-machine infinite-bus (SMIB power system that includes IEEE type-ST1 excitation system and PSS based on transfer fu¬n¬c¬¬tion structure is presented. The changes in the operating co¬n¬dition of a power system on dynamic performance have been exa¬m¬ined. The dynamic performance of the closed-loop system is ana¬lyzed base on its eigenvalues. The effectiveness of the par¬a¬m¬e¬t¬ers changes on dynamic stability is verified by simulation res¬u¬l¬ts. Three types of PSS have been considered for analysis: (a the derivative PSS, (b the lead-lag PSS or conventional PSS, and (c the proportional-integral-derivative PSS. The objective fu¬nc¬t¬i¬o¬n is formulated to increase the dam¬¬ping ratio of the electromechanical mode eigenvalues. Simu¬la¬tion results show that the PID-PSS performs better for less ov¬e¬r¬shoot and less settling time comp¬ared with the CPSS and DPSS un¬der different load ope¬ration and the significant system pa¬r¬am¬eter variation conditions.
Stability analysis of lower dimensional gravastars in noncommutative geometry
Energy Technology Data Exchange (ETDEWEB)
Banerjee, Ayan [Jadavpur University, Department of Mathematics, Kolkata (India); Hansraj, Sudan [University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Durban (South Africa)
2016-11-15
The Banados et al. (Phys. Rev. Lett 69:1849, 1992), black hole solution is revamped from the Einstein field equations in (2 + 1)-dimensional anti-de Sitter spacetime, in a context of noncommutative geometry (Phys. Rev. D 87:084014, 2013). In this article, we explore the exact gravastar solutions in three-dimensional anti-de Sitter space given in the same geometry. As a first step we derive BTZ solution assuming the source of energy density as point-like structures in favor of smeared objects, where the particle mass M, is diffused throughout a region of linear size √(α) and is described by a Gaussian function of finite width rather than a Dirac delta function. We matched our interior solution to an exterior BTZ spacetime at a junction interface situated outside the event horizon. Furthermore, a stability analysis is carried out for the specific case when χ < 0.214 under radial perturbations about the static equilibrium solutions. To give theoretical support we are also trying to explore their physical properties and characteristics. (orig.)
Preliminary Analysis of Slope Stability in Kuok and Surrounding Areas
Directory of Open Access Journals (Sweden)
Dewandra Bagus Eka Putra
2016-12-01
Full Text Available The level of slope influenced by the condition of the rocks beneath the surface. On high level of slopes, amount of surface runoff and water transport energy is also enlarged. This caused by greater gravity, in line with the surface tilt from the horizontal plane. In other words, topsoil eroded more and more. When the slope becomes twice as steep, then the amount of erosion per unit area be 2.0 - 2.5 times more. Kuok and surrounding area is the road access between the West Sumatra and Riau which plays an important role economies of both provinces. The purpose of this study is to map the locations that have fairly steep slopes and potential mode of landslides. Based on SRTM data obtained, the roads in Kuok area has a minimum elevation of + 33 m and a maximum + 217.329 m. Rugged road conditions with slope ranging from 24.08 ° to 44.68 ° causing this area having frequent landslides. The result of slope stability analysis in a slope near the Water Power Plant Koto Panjang, indicated that mode of active failure is toppling failure or rock fall and the potential zone of failure is in the center part of the slope.
Stability Analysis of Reactive Multiphase Slug Flows in Microchannels
Directory of Open Access Journals (Sweden)
Alejandro A. Munera Parra
2014-05-01
Full Text Available Conducting multiphase reactions in micro-reactors is a promising strategy for intensifying chemical and biochemical processes. A major unresolved challenge is to exploit the considerable benefits offered by micro-scale operation for industrial scale throughputs by numbering-up whilst retaining the underlying advantageous flow characteristics of the single channel system in multiple parallel channels. Fabrication and installation tolerances in the individual micro-channels result in different pressure losses and, thus, a fluid maldistribution. In this work, an additional source of maldistribution, namely the flow multiplicities, which can arise in a multiphase reactive or extractive flow in otherwise identical micro-channels, was investigated. A detailed experimental and theoretical analysis of the flow stability with and without reaction for both gas-liquid and liquid-liquid slug flow has been developed. The model has been validated using the extraction of acetic acid from n-heptane with the ionic liquid 1-Ethyl-3-methylimidazolium ethyl sulfate. The results clearly demonstrate that the coupling between flow structure, the extent of reaction/extraction and pressure drop can result in multiple operating states, thus, necessitating an active measurement and control concept to ensure uniform behavior and optimal performance.
Crack stability analysis of low alloy steel primary coolant pipe
Energy Technology Data Exchange (ETDEWEB)
Tanaka, T.; Kameyama, M. [Kansai Electric Power Company, Osaka (Japan); Urabe, Y. [Mitsubishi Heavy Industries, Ltd., Takasago (Japan)] [and others
1997-04-01
At present, cast duplex stainless steel has been used for the primary coolant piping of PWRs in Japan and joints of dissimilar material have been applied for welding to reactor vessels and steam generators. For the primary coolant piping of the next APWR plants, application of low alloy steel that results in designing main loops with the same material is being studied. It means that there is no need to weld low alloy steel with stainless steel and that makes it possible to reduce the welding length. Attenuation of Ultra Sonic Wave Intensity is lower for low alloy steel than for stainless steel and they have advantageous inspection characteristics. In addition to that, the thermal expansion rate is smaller for low alloy steel than for stainless steel. In consideration of the above features of low alloy steel, the overall reliability of primary coolant piping is expected to be improved. Therefore, for the evaluation of crack stability of low alloy steel piping to be applied for primary loops, elastic-plastic future mechanics analysis was performed by means of a three-dimensioned FEM. The evaluation results for the low alloy steel pipings show that cracks will not grow into unstable fractures under maximum design load conditions, even when such a circumferential crack is assumed to be 6 times the size of the wall thickness.
WIPP fire hazards and risk analysis
International Nuclear Information System (INIS)
1991-05-01
The purpose of this analysis was to conduct a fire hazards risk analysis of the Transuranic (TRU) contact-handled waste receipt, emplacement, and disposal activities at the Waste Isolation Pilot Plant (WIPP). The technical bases and safety envelope for these operations are defined in the approved WIPP Final Safety Analysis Report (FSAR). Although the safety documentation for the initial phase of the Test Program, the dry bin scale tests, has not yet been approved by the Department of Energy (DOE), reviews of the draft to date, including those by the Advisory Committee on Nuclear Facility Safety (ACNFS), have concluded that the dry bin scale tests present no significant risks in excess of those estimated in the approved WIPP FSAR. It is the opinion of the authors and reviewers of this analysis, based on sound engineering judgment and knowledge of the WIPP operations, that a Fire Hazards and Risk Analysis specific to the dry bin scale test program is not warranted prior to first waste receipt. This conclusion is further supported by the risk analysis presented in this document which demonstrates the level of risk to WIPP operations posed by fire to be extremely low. 15 refs., 41 figs., 48 tabs
Hydrodynamic Stability Analysis of Particle-Laden Solid Rocket Motors
International Nuclear Information System (INIS)
Elliott, T S; Majdalani, J
2014-01-01
Fluid-wall interactions within solid rocket motors can result in parietal vortex shedding giving rise to hydrodynamic instabilities, or unsteady waves, that translate into pressure oscillations. The oscillations can result in vibrations observed by the rocket, rocket subsystems, or payload, which can lead to changes in flight characteristics, design failure, or other undesirable effects. For many years particles have been embedded in solid rocket propellants with the understanding that their presence increases specific impulse and suppresses fluctuations in the flowfield. This study utilizes a two dimensional framework to understand and quantify the aforementioned two-phase flowfield inside a motor case with a cylindrical grain perforation. This is accomplished through the use of linearized Navier-Stokes equations with the Stokes drag equation and application of the biglobal ansatz. Obtaining the biglobal equations for analysis requires quantification of the mean flowfield within the solid rocket motor. To that end, the extended Taylor-Culick form will be utilized to represent the gaseous phase of the mean flowfield while the self-similar form will be employed for the particle phase. Advancing the mean flowfield by quantifying the particle mass concentration with a semi-analytical solution the finalized mean flowfield is combined with the biglobal equations resulting in a system of eight partial differential equations. This system is solved using an eigensolver within the framework yielding the entire spectrum of eigenvalues, frequency and growth rate components, at once. This work will detail the parametric analysis performed to demonstrate the stabilizing and destabilizing effects of particles within solid rocket combustion
International Nuclear Information System (INIS)
Zheng Youqi; Wu Hongchun; Cao Liangzhi
2013-01-01
This paper describes the stability analysis for the coarse mesh finite difference (CMFD) acceleration used in the wavelet expansion method. The nonlinear CMFD acceleration scheme is transformed by linearization and the Fourier ansatz is introduced into the linearized formulae. The spectral radius is defined as the stability criterion, which is the least upper bound (LUB) of the largest eigenvalue of Fourier analysis matrix. The stability analysis considers the effect of mesh size (spectral length), coarse mesh division and scattering ratio. The results show that for the wavelet expansion method, the CMFD acceleration is conditionally stable. The small size of fine mesh brings stability and fast convergent. With the increase of the mesh size, the stability becomes worse. The scattering ratio does not impact the stability obviously. It makes the CMFD acceleration highly efficient in the strong scattering case. The results of Fourier analysis are verified by the numerical tests based on a homogeneous slab problem.
Standardised risk analysis as a communication tool
International Nuclear Information System (INIS)
Pluess, Ch.; Montanarini, M.; Bernauer, M.
1998-01-01
Full text of publication follows: several European countries require a risk analysis for the production, storage or transport a dangerous goods. This requirement imposes considerable administrative effort for some sectors of the industry. In order to minimize the effort of such studies, a generic risk analysis for an industrial sector proved to help. Standardised procedures can consequently be derived for efficient performance of the risk investigations. This procedure was successfully established in Switzerland for natural gas transmission lines and fossil fuel storage plants. The development process of the generic risk analysis involved an intense discussion between industry and authorities about methodology of assessment and the criteria of acceptance. This process finally led to scientific consistent modelling tools for risk analysis and to an improved communication from the industry to the authorities and the public. As a recent example, the Holland-Italy natural gas transmission pipeline is demonstrated, where this method was successfully employed. Although this pipeline traverses densely populated areas in Switzerland, using this established communication method, the risk problems could be solved without delaying the planning process. (authors)
Stability Analysis of Train Movement with Uncertain Factors
Directory of Open Access Journals (Sweden)
JingJing Ye
2015-01-01
Full Text Available We propose a new traffic model which is based on the traditional OV (optimal velocity car-following model. Here, some realistic factors are regarded as uncertain quantity, such as the headway distance. Our aim is to analyze and discuss the stability of car-following model under the constraint of uncertain factors. Then, according to the principle of expected value in fuzzy theory, an improved OV traffic model is constructed. Simulation results show that our proposed model can avoid collisions effectively under uncertain environment, and its stability can also be improved. Moreover, we discuss its stability as some parameters change, such as the relaxation time.
Directory of Open Access Journals (Sweden)
Céline Bonnyaud
Full Text Available The Timed Up and Go (TUG test is often used to estimate risk of falls. Foot clearance and displacement of the center of mass (COM, which are related to risk of tripping and dynamic stability have never been evaluated during the TUG. Accurate assessment of these parameters using instrumented measurements would provide a comprehensive assessment of risk of falls in hemiparetic patients. The aims of this study were to analyze correlations between TUG performance time and displacement of the COM and foot clearance in patients with stroke-related hemiparesis and healthy subjects during the walking and turning sub-tasks of the TUG and to compare these parameters between fallers and non-fallers.29 hemiparetic patients and 25 healthy subjects underwent three-dimensional gait analysis during the TUG test. COM and foot clearance were analyzed during the walking and turning sub-tasks of the TUG.Lateral displacement of the COM was greater and faster during the walking sub-tasks and vertical displacement of the COM was greater during the turn in the patients compared to the healthy subjects (respectively p<0.01 and p<0.05. Paretic foot clearance was greater during walking and displacement of the COM was slower during the turn in the patients (p<0.01. COM displacement and velocity during the turn were correlated with TUG performance in the patients, however, vertical COM displacement was not. These correlations were significant in the healthy subjects. There were no differences between COM parameters or foot clearance in fallers and non-fallers.Hemiparetic patients are less stable than healthy subjects, but compensate with a cautious gait to avoid tripping. Instrumented analysis of the TUG test appears relevant for the assessment of dynamic stability in hemiparetic patients, providing more information than straight-line gait.
Small-Signal Stability Analysis of Full-Load Converter Interfaced Wind Turbines
Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård; Jensen, Kim H.; Dixon, Andrew; Østergaard, Jacob
2009-01-01
Power system stability investigations of wind farms often cover the tasks of low-voltage-fault-ride-through, voltage and reactive power control, and power balancing, but not much attention has yet been paid to the task of small-signal stability. Small-signal stability analysis needs increasing focus since the share of wind power increases substituting power generation from conventional power plants. Here, a study based on modal analysis is presented which investigate the effect of large scale...
LDC commodity risk analysis and recommendations
Energy Technology Data Exchange (ETDEWEB)
NONE
2002-08-08
Under the current operation of the new competitive electricity market in Ontario, local distribution companies (LDCs) are required to pay the monthly invoice of the Independent Market Operator (IMO) before they collect from end-users for the consumption period covered by the invoice, with no clear guarantee that the recovery will occur. This situation creates a major cash flow problem and financial risk for LDCs and threatens the integrity and stability of the electricity market. This paper described 3 features of Ontario's competitive electricity market that create financial and commodity risk. The first problem is that there is no limit on how high prices can rise. Increases in wholesale commodity prices can result in a situation where the amount of the IMO's invoice is greater than the LDC's ability to pay at the time of receipt. Secondly, the LDC bears a 100 per cent payment obligation to the IMO administrator of the wholesale market. The third problem is that LDCs bear payment default risk from all consumers in the Ontario market, including electricity retailers. This paper presents some specific policy solutions that can protect the market from this threat. It was suggested that in order to protect the integrity of Ontario's electricity market during high prices, a policy must be drafted to address the commodity price financing risk (CPFR) issue. The policy must also define what happens if prices increase past the LDCs financing obligation limit. tabs., figs.
LDC commodity risk analysis and recommendations
International Nuclear Information System (INIS)
2002-01-01
Under the current operation of the new competitive electricity market in Ontario, local distribution companies (LDCs) are required to pay the monthly invoice of the Independent Market Operator (IMO) before they collect from end-users for the consumption period covered by the invoice, with no clear guarantee that the recovery will occur. This situation creates a major cash flow problem and financial risk for LDCs and threatens the integrity and stability of the electricity market. This paper described 3 features of Ontario's competitive electricity market that create financial and commodity risk. The first problem is that there is no limit on how high prices can rise. Increases in wholesale commodity prices can result in a situation where the amount of the IMO's invoice is greater than the LDC's ability to pay at the time of receipt. Secondly, the LDC bears a 100 per cent payment obligation to the IMO administrator of the wholesale market. The third problem is that LDCs bear payment default risk from all consumers in the Ontario market, including electricity retailers. This paper presents some specific policy solutions that can protect the market from this threat. It was suggested that in order to protect the integrity of Ontario's electricity market during high prices, a policy must be drafted to address the commodity price financing risk (CPFR) issue. The policy must also define what happens if prices increase past the LDCs financing obligation limit. tabs., figs
Risk analysis of alternative energy sources
International Nuclear Information System (INIS)
Kazmer, D.R.
1982-01-01
The author explores two points raised by Miller Spangler in a January 1981 issue: public perception of risks involving nuclear power plants relative to those of conventional plants and criteria for evaluating the way risk analyses are made. On the first point, he concludes that translating public attitudes into the experts' language of probability and risk could provide better information and understanding of both the attitudes and the risks. Viewing risk analysis methodologies as filters which help to test historical change, he suggests that the lack of information favors a lay jury approach for energy decisions. Spangler responds that Congress is an example of lay decision making, but that a lay jury, given public disinterest and polarization, would probably not improve social justice on the nuclear issue. 5 references, 4 figures
Risk analysis of industrial plants operation
International Nuclear Information System (INIS)
Hubert, Philippe
1989-12-01
This study examines the possibilities of systematic technology risk analysis in view of territorial management (city, urban community, region), including chronic and accidental risks. The objective was to relate this evaluation with those done for permanent water and air pollution. Risk management for pollution are done for a long time. A number of studies were done in urban communities and regions both for air and water pollution. The second objective is related to management of industrial risks: nuclear, petrochemical, transport of hazardous material, pipelines, etc. At the beginning, three possibilities of effects are taken into account: human health, economic aspect and water, and possibilities of evaluation are identified. Elements of risk identification are presented for quantification of results [fr
Risk Analysis at Work in Manufacturing Organization
Directory of Open Access Journals (Sweden)
Maroš Korenko
2015-01-01
Full Text Available Risk is virtually present everywhere around us. Nowadays, there is an increasing focus on safety at work; therefore, the organizations that want to be successful in the market try to eliminate risk factors to a minimum to avoid or prevent the health hazard of employees, damages to property or the environment. The work is focused on the risk assessment of a selected device, which is the most risky workplace according to the organization where the research was conducted. In the practical part, we became familiar with the equipment for welding and a thorough analysis of the current state of safety by a complex method was done. Consequently, corrective actions to reduce risk to an acceptable level were proposed. After that, we reassessed the risks of complex method, and the point method was used to verify the effectiveness of proposed remedial measures.
Stability Analysis of Spacecraft Motion in the Vicinity of Asteroids
National Aeronautics and Space Administration — The objective of my proposal is to determine the stability of a spacecraft when in the vicinity of an asteroid. Orbiting an asteroid is a difficult task. The unique...
Stability model and risk assessment for the Montescaglioso Landslide (Southern Italy)
Amanti, Marco; Chiessi, Vittorio; Guarino, Paolo Maria; Spizzichino, Daniele; Troccoli, Alessandro; Vizzini, Giorgio
2015-04-01
In this paper, we present the final results of a landslide risk assessment evaluation implemented for the recent Montescaglioso landslide emergency occurred on 3rd December 2013 when a large and rapid slope failure, triggered by prolonged and intense rainfall, affected a big portion of the SW slope of the village. The slope failure damaged a main road, private homes and commercial buildings. The Montescaglioso village (Basilicata Region, Italy) is located on the top of a conglomerate hill overlying a gentle slope constituted by Plio-Pleistocene clays. The area has been affected since ancient time by different landslide typologies and mechanism, as determined by a direct geomorphological survey and from mapping and available technical literature. Phenomena such as rock-falls and rock lateral spreading in the upper part of the hill, and rotational/translational slides and earth flows can be recognized in the area. Landslides are mainly promoted by the geological and structural setting of the area as well as by very low mechanical characteristics of sediments outcropping in the area. After the emergency phase, a detailed program of field survey and laboratory campaign has been implemented during the last year. A detailed topographical analysis has been developed by using the LIDAR survey in order to define morphometric conditions and geometry modifications of the slope affected by the landslide. Based on the studies carried out in the area, the research has been aimed to assessing the stability conditions (residual landslide risk) of the SW slope of the hill trough an extended geological, geomorphological and geotechnical campaign linked with numerical study of present instability mechanism. The geological and geotechnical model of the slope has been defined trough the analysis of the past and recent logs obtained from several boreholes and also through the results of many mechanical test performed on samples taken in the area. The numerical study has been carried out
Advanced nonlinear stability analysis of boiling water nuclear reactors
Lange, Carsten
2009-01-01
This thesis is concerned with nonlinear analyses of BWR stability behaviour, contributing to a deeper understanding in this field. Despite negative feedback-coefficients of a BWR, there are operational points (OP) at which oscillatory instabilities occur. So far, a comprehensive and an in-depth understanding of the nonlinear BWR stability behaviour are missing, even though the impact of the significant physical parameters is well known. In particular, this concerns parameter regions in whi...
Population Stabilization in India: A Sub-State level Analysis
Purohit C, Dr Brijesh
2007-01-01
The study aims at analyzing economic and policy factors impinging upon population stabilization measures at the district (sub-state level) in India. It reflects upon popularly debated notions, namely, that development is the best contraceptive or whether contraceptive is the best development. In order to reflect upon this notion, we hypothesize that the factors determining the success of population stabilization measures are likely to be different across rich and poor states. It is more likel...
Roos, Paulien E.; Dingwell, Jonathan B.
2011-01-01
Measures that can predict risk of falling are essential for enrollment of older adults into fall prevention programs. Local and orbital stability directly quantify responses to very small perturbations and are therefore putative candidates for predicting fall risk. However, research to date is not conclusive on whether and how these measures relate to fall risk. Testing this empirically would be time consuming or may require high risk tripping experiments. Simulation studies therefore provide...
A more general model for the analysis of the rock slope stability
Indian Academy of Sciences (India)
characteristics of intact rock have taken part in the analysis. The analysis presented here gives a better concept, view, and idea of understanding the physical nature of rock slopes and includes more parameters governing the stability of the potential failure zone. Keywords. Wedge failure; slope stability; trace length; joint set; ...
Kinematic Analysis of a Posterior-stabilized Knee Prosthesis
Zhao, Zhi-Xin; Wen, Liang; Qu, Tie-Bing; Hou, Li-Li; Xiang, Dong; Bin, Jia
2015-01-01
Background: The goal of total knee arthroplasty (TKA) is to restore knee kinematics. Knee prosthesis design plays a very important role in successful restoration. Here, kinematics models of normal and prosthetic knees were created and validated using previously published data. Methods: Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments. The data from the three-dimensional models of the normal knee joint and a posterior-stabilized (PS) knee prosthesis were imported into finite element analysis software to create the final kinematic model of the TKA prosthesis, which was then validated by comparison with a previous study. The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0–135° flexion. Results: Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses. The PS knee prosthesis underwent an abnormal forward displacement compared with the normal knee and has insufficient, or insufficiently aggressive, “rollback” compared with the lateral femur of the normal knee. In addition, a certain degree of reverse rotation occurs during flexion of the PS knee prosthesis. Conclusions: There were still several differences between the kinematics of the PS knee prosthesis and a normal knee, suggesting room for improving the design of the PS knee prosthesis. The abnormal kinematics during early flexion shows that the design of the articular surface played a vital role in improving the kinematics of the PS knee prosthesis. PMID:25591565
Kinematic Analysis of a Posterior-stabilized Knee Prosthesis
Directory of Open Access Journals (Sweden)
Zhi-Xin Zhao
2015-01-01
Full Text Available Background: The goal of total knee arthroplasty (TKA is to restore knee kinematics. Knee prosthesis design plays a very important role in successful restoration. Here, kinematics models of normal and prosthetic knees were created and validated using previously published data. Methods: Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments. The data from the three-dimensional models of the normal knee joint and a posterior-stabilized (PS knee prosthesis were imported into finite element analysis software to create the final kinematic model of the TKA prosthesis, which was then validated by comparison with a previous study. The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion. Results: Both the output data trends and the measured values derived from the normal knee′s kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses. The PS knee prosthesis underwent an abnormal forward displacement compared with the normal knee and has insufficient, or insufficiently aggressive, "rollback" compared with the lateral femur of the normal knee. In addition, a certain degree of reverse rotation occurs during flexion of the PS knee prosthesis. Conclusions: There were still several differences between the kinematics of the PS knee prosthesis and a normal knee, suggesting room for improving the design of the PS knee prosthesis. The abnormal kinematics during early flexion shows that the design of the articular surface played a vital role in improving the kinematics of the PS knee prosthesis.
Dynamic remedial action scheme using online transient stability analysis
Shrestha, Arun
Economic pressure and environmental factors have forced the modern power systems to operate closer to their stability limits. However, maintaining transient stability is a fundamental requirement for the operation of interconnected power systems. In North America, power systems are planned and operated to withstand the loss of any single or multiple elements without violating North American Electric Reliability Corporation (NERC) system performance criteria. For a contingency resulting in the loss of multiple elements (Category C), emergency transient stability controls may be necessary to stabilize the power system. Emergency control is designed to sense abnormal conditions and subsequently take pre-determined remedial actions to prevent instability. Commonly known as either Remedial Action Schemes (RAS) or as Special/System Protection Schemes (SPS), these emergency control approaches have been extensively adopted by utilities. RAS are designed to address specific problems, e.g. to increase power transfer, to provide reactive support, to address generator instability, to limit thermal overloads, etc. Possible remedial actions include generator tripping, load shedding, capacitor and reactor switching, static VAR control, etc. Among various RAS types, generation shedding is the most effective and widely used emergency control means for maintaining system stability. In this dissertation, an optimal power flow (OPF)-based generation-shedding RAS is proposed. This scheme uses online transient stability calculation and generator cost function to determine appropriate remedial actions. For transient stability calculation, SIngle Machine Equivalent (SIME) technique is used, which reduces the multimachine power system model to a One-Machine Infinite Bus (OMIB) equivalent and identifies critical machines. Unlike conventional RAS, which are designed using offline simulations, online stability calculations make the proposed RAS dynamic and adapting to any power system
Khan, Saad Jawaid; Khan, Soobia Saad; Usman, Juliana; Mokhtar, Abdul Halim; Abu Osman, Noor Azuan
2018-02-01
This study aims to investigate the effects of varying toe angles at different platform settings on Overall Stability Index of postural stability and fall risk using Biodex Balance System in healthy participants and medial knee osteoarthritis patients. Biodex Balance System was employed to measure postural stability and fall risk at different foot progression angles (ranging from -20° to 40°, with 10° increments) on 20 healthy (control group) and 20 knee osteoarthritis patients (osteoarthritis group) randomly (age: 59.50 ± 7.33 years and 61.50 ± 8.63 years; body mass: 69.95 ± 9.86 kg and 70.45 ± 8.80 kg). Platform settings used were (1) static, (2) postural stability dynamic level 8 (PS8), (3) fall risk levels 12 to 8 (FR12) and (4) fall risk levels 8 to 2 (FR8). Data from the tests were analysed using three-way mixed repeated measures analysis of variance. The participant group, platform settings and toe angles all had a significant main effect on balance ( p ≤ 0.02). Platform settings had a significant interaction effect with participant group F(3, 144) = 6.97, p fall risk as compared to the healthy group. Changing platform settings has a more pronounced effect on balance in knee osteoarthritis group than in healthy participants. Changing toe angles produced similar effects in both the participant groups, with decreased stability and increased fall risk at extreme toe-in and toe-out angles.
Phasor model of full scale converter wind turbine for small-signal stability analysis
DEFF Research Database (Denmark)
Ghiga, Radu; Wu, Qiuwei; Nielsen, Arne Hejde
2017-01-01
The small-signal stability analysis of power system electromechanical oscillations is a well-established field in control and stability assessment of power systems. The impact of large wind farms on small-signal stability of power systems has been a topic of high interest in recent years....... This study presents a phasor model of full scale converter wind turbines (WTs) implemented in MATLAB/SIMULINK for small-signal stability studies. The phasor method is typically used for dynamic studies of power systems consisting of large electric machines. It can also be applied to any linear system....... This represents an advantage in small-signal stability studies, which are based on modal analysis of the linearised model and are usually complemented with dynamic simulations. The proposed model can represent a single WT or an aggregated wind power plant. The implemented model for small-signal stability analysis...
Simon, Anne-Laure; Lugade, Vipul; Bernhardt, Kathie; Larson, A Noelle; Kaufman, Kenton
2017-06-01
Daily living activities are dynamic, requiring spinal motion through space. Current assessment of spinal deformities is based on static measurements from full-spine standing radiographs. Tools to assess dynamic stability during gait might be useful to enhance the standard evaluation. The aim of this study was to evaluate gait dynamic imbalance in patients with spinal deformity using the dynamic stability margin (DSM). Twelve normal subjects and 17 patients with spinal deformity were prospectively recruited. A kinematic 3D gait analysis was performed for the control group (CG) and the spinal deformity group (SDG). The DSM (distance between the extrapolated center of mass and the base of support) and time-distance parameters were calculated for the right and left side during gait. The relationship between DSM and step length was assessed using three variables: gait stability, symmetry, and consistency. Variables' accuracy was validated by a discriminant analysis. Patients with spinal deformity exhibited gait instability according to the DSM (0.25m versus 0.31m) with decreased velocity (1.1ms -1 versus 1.3ms -1 ) and decreased step length (0.32m versus 0.38m). According to the discriminant analysis, gait stability was the more accurate variable (area under the curve AUC=0.98) followed by gait symmetry and consistency. However, gait consistency showed 100% of specificity, sensitivity, and accuracy of precision. The DSM showed that patients with spinal malalignment exhibit decreased gait stability, symmetry, and consistency besides gait time-distance parameter changes. Additional work is required to determine how to apply the DSM for preoperative and postoperative spinal deformity management. Copyright © 2017. Published by Elsevier B.V.
International Nuclear Information System (INIS)
Suhwan, JI; Shirahama, H.; Koshizuka, S.; Oka, Y.
2001-01-01
The purpose of this study is to evaluate the thermal-hydraulic and the thermal-nuclear coupled stabilities of a supercritical pressure light water-cooled reactor. A stability analysis code at supercritical pressure is developed. Using this code, stabilities of full and partial-power reactor operating at supercritical pressure are investigated by the frequency-domain analysis. Two types of SCRs are analyzed; a supercritical light water reactor (SCLWR) and a supercritical water-cooled fast reactor (SCFR). The same stability criteria as Boiling Water Reactor are applied. The thermal-hydraulic stability of SCLWR and SCFR satisfies the criteria with a reasonable orifice loss coefficient. The decay ratio of the thermal-nuclear coupled stability in SCFR is almost zero because of a small coolant density coefficient of the fast reactor. The evaluated decay ratio of the thermal-nuclear coupled stability is 3,41 ∼ 10 -V at 100% power in SCFR and 0,028 at 100% power in SCLWR. The sensitivity is investigated. It is found that the thermal-hydraulic stability is sensitive to the mass flow rate strongly and the thermal-nuclear coupled stability to the coolant density coefficient. The bottom power peak distribution makes the thermal-nuclear stability worse and the thermal-nuclear stability better. (author)
Risk Assessment and Integration Team (RAIT) Portfolio Risk Analysis Strategy
Edwards, Michelle
2010-01-01
Impact at management level: Qualitative assessment of risk criticality in conjunction with risk consequence, likelihood, and severity enable development of an "investment policy" towards managing a portfolio of risks. Impact at research level: Quantitative risk assessments enable researchers to develop risk mitigation strategies with meaningful risk reduction results. Quantitative assessment approach provides useful risk mitigation information.
Fractal time series analysis of postural stability in elderly and control subjects
Directory of Open Access Journals (Sweden)
Doussot Michel
2007-05-01
Full Text Available Abstract Background The study of balance using stabilogram analysis is of particular interest in the study of falls. Although simple statistical parameters derived from the stabilogram have been shown to predict risk of falls, such measures offer little insight into the underlying control mechanisms responsible for degradation in balance. In contrast, fractal and non-linear time-series analysis of stabilograms, such as estimations of the Hurst exponent (H, may provide information related to the underlying motor control strategies governing postural stability. In order to be adapted for a home-based follow-up of balance, such methods need to be robust, regardless of the experimental protocol, while producing time-series that are as short as possible. The present study compares two methods of calculating H: Detrended Fluctuation Analysis (DFA and Stabilogram Diffusion Analysis (SDA for elderly and control subjects, as well as evaluating the effect of recording duration. Methods Centre of pressure signals were obtained from 90 young adult subjects and 10 elderly subjects. Data were sampled at 100 Hz for 30 s, including stepping onto and off the force plate. Estimations of H were made using sliding windows of 10, 5, and 2.5 s durations, with windows slid forward in 1-s increments. Multivariate analysis of variance was used to test for the effect of time, age and estimation method on the Hurst exponent, while the intra-class correlation coefficient (ICC was used as a measure of reliability. Results Both SDA and DFA methods were able to identify differences in postural stability between control and elderly subjects for time series as short as 5 s, with ICC values as high as 0.75 for DFA. Conclusion Both methods would be well-suited to non-invasive longitudinal assessment of balance. In addition, reliable estimations of H were obtained from time series as short as 5 s.
Strength Analysis of Coconut Fiber Stabilized Earth for Farm Structures
Enokela, O. S.; P. O, Alada
2012-07-01
Investigation of the strength characteristic of soil from alluvial deposit of River Benue in makurdi stabilized with coconut fiber as a stabilizer was carried as local building material for farm structure. Processed coconut fibers were mixed with the soil at four different mix ratios of 1% fiber, 2% fiber, 3% fiber and 4% fiber by percentage weight with 0% fiber as control. Compaction test and compressive strength were carried out on the various stabilizing ratio. From the compaction test, the correlation between the maximum dry density and optimum moisture content is a second order polynomial with a coefficient of 63% obtained at1.91kg/m3and 20.0% respectively while the compressive strength test shows an optimum failure load of 8.62N/mm2 at 2%fibre:100% soil mix ratio at 2.16 maximum dry density.
Stability analysis of machine tool spindle under uncertainty
Directory of Open Access Journals (Sweden)
Wei Dou
2016-05-01
Full Text Available Chatter is a harmful machining vibration that occurs between the workpiece and the cutting tool, usually resulting in irregular flaw streaks on the finished surface and severe tool wear. Stability lobe diagrams could predict chatter by providing graphical representations of the stable combinations of the axial depth of the cut and spindle speed. In this article, the analytical model of a spindle system is constructed, including a Timoshenko beam rotating shaft model and double sets of angular contact ball bearings with 5 degrees of freedom. Then, the stability lobe diagram of the model is developed according to its dynamic properties. The Monte Carlo method is applied to analyse the bearing preload influence on the system stability with uncertainty taken into account.
Stability analysis of two-dimensional digital recursive filters
Alexander, W. E.; Pruess, S. A.
1980-01-01
A new approach to the stability problem for the two-dimensional digital recursive filter is presented. The bivariate difference equation representation of the two-dimensional recursive digital filter is converted to a multiinput-multioutput (MIMO) system similar to the state-space representation of the one-dimensional digital recursive filter. In this paper, a pseudo-state representation is used and three coefficient matrices are obtained. A general theorem for stability of two-dimensional digital recursive filters is derived and a very useful theorem is presented which expresses sufficient requirements for instability in terms of the spectral radii of these matrices.
Power system transient stability analysis based on branch potential characteristics
Han, Huan; Wang, Zengping
2017-09-01
Branch potential function is proposed based on the power system network preserving model. The concept of thermodynamics-entropy, is introduced to describe spatial distribution characteristics of the branch potential energy. Branch potential energy was analysed in time and space domain., with transient stability index proposed accordingly. The larger disturbance energy line fault injected to grid is, the larger branch energy entropy will be, and the more energy accumulated on key branches is, the more prone to lose stability the system will be. Simulation results on IEEE system proved its feasibility.
Implementing the Bayesian paradigm in risk analysis
International Nuclear Information System (INIS)
Aven, T.; Kvaloey, J.T.
2002-01-01
The Bayesian paradigm comprises a unified and consistent framework for analyzing and expressing risk. Yet, we see rather few examples of applications where the full Bayesian setting has been adopted with specifications of priors of unknown parameters. In this paper, we discuss some of the practical challenges of implementing Bayesian thinking and methods in risk analysis, emphasizing the introduction of probability models and parameters and associated uncertainty assessments. We conclude that there is a need for a pragmatic view in order to 'successfully' apply the Bayesian approach, such that we can do the assignments of some of the probabilities without adopting the somewhat sophisticated procedure of specifying prior distributions of parameters. A simple risk analysis example is presented to illustrate ideas
Bornstein, Marc H.; Hahn, Chun-Shin; Putnick, Diane L.
2016-01-01
Background: Command of language is a fundamental skill, a cornerstone of multiple cognitive and socioemotional aspects of development, and a necessary ingredient of successful adjustment and functioning in society. Little is known about the developmental stability of language in at-risk youth or which biological and social risk factors moderate…
Economic impact assessment in pest risk analysis
Soliman, T.A.A.; Mourits, M.C.M.; Oude Lansink, A.G.J.M.; Werf, van der W.
2010-01-01
According to international treaties, phytosanitary measures against introduction and spread of invasive plant pests must be justified by a science-based pest risk analysis (PRA). Part of the PRA consists of an assessment of potential economic consequences. This paper evaluates the main available
YILDIRIM, Burak
2017-01-01
This paper shows the effects of high PVintegration on the power system voltage stability. PV power plant was appliedto the IEEE 30 bus test system. Modal analysis method is used to show theeffect of PV integration on power system voltage stability. The power rate ofsynchronous generator in the IEEE 30 bus system is increased to show the powersystem stability effect of high PV penetration and then the PV generation withthe same power rate is connected appropriate bus in power system. The modal...
International Nuclear Information System (INIS)
Park, Ju H.
2007-01-01
This paper considers the robust stability analysis of cellular neural networks with discrete and distributed delays. Based on the Lyapunov stability theory and linear matrix inequality (LMI) technique, a novel stability criterion guaranteeing the global robust convergence of the equilibrium point is derived. The criterion can be solved easily by various convex optimization algorithms. An example is given to illustrate the usefulness of our results
Advanced techniques for the analysis of crisis stability, deterrence, and latency
Energy Technology Data Exchange (ETDEWEB)
Canavan, G.H.
1997-12-01
Studies on crisis stability, deterrence, and latency are presented in chronological order, which also reflects their logical order of development, captures the main features of stability analysis; relates first strike, crisis, and arms control stability as seen from US and Russian perspective; and addresses questions such as whether uncertainty in damage preference or defense deployment can be destabilizing. It illustrates the problems with alternative metrics, latency and reconstitution, and deep unilateral and proportional force reductions.
Stability analysis of multipoint tool equipped with metal cutting ceramics
Maksarov, V. V.; Khalimonenko, A. D.; Matrenichev, K. G.
2017-10-01
The article highlights the issues of determining the stability of the cutting process by a multipoint cutting tool equipped with cutting ceramics. There were some recommendations offered on the choice of parameters of replaceable cutting ceramic plates for milling based of the conducted researches. Ceramic plates for milling are proposed to be selected on the basis of value of their electrical volume resistivity.
Experimental analysis of aerodynamic stability of stress-ribbon footbridges
Czech Academy of Sciences Publication Activity Database
Pirner, Miroš; Fischer, Ondřej
1999-01-01
Roč. 2, č. 2 (1999), s. 95-104 ISSN 1226-6116 Institutional support: RVO:68378297 Keywords : footbridges * aerodynamic stability * bending-torsional vibrations * wind-excited vibrations * wind-tunnel in civil engineering Subject RIV: JM - Building Engineering http://koreascience.or.kr/article/ArticleFullRecord.jsp?cn=KJKHCF_1999_v2n2_95&ordernum=5
Analysis of Deformation Characteristics and Stability Mechanisms of ...
Indian Academy of Sciences (India)
21
deformation and inclinometer monitoring of internal deformation over 7 years, we find that the displacement of a typical ... Stability mechanisms; The field monitoring. 1. Introduction. Completed in 2009, the Three ..... rainfall infiltrates into the landslide mass, which increases the self-weight of the landslide mass and forms the ...
Stress determination and geomechanical stability analysis of an oil ...
Indian Academy of Sciences (India)
In this paper, a numerical model using three-dimensional finite difference code FLAC3D is proposed for analysing the stability of an oil well drilled in four formations. Normalized Yielded Zone Area (NYZA, i.e., the ratio of surrounding yielded cross-sectional area to initial area of well) has been determined for different mud ...
Studies of iso-alpha-acids : analysis, purification, and stability.
Khatib, Alfi
2006-01-01
The female cones of hop (Humulus lupulus L.) are added to beer, providing taste and flavour and contributing to the stability of foam. The main constituents of hop related to these properties are generically known as alpha-acids. During the brewing process, these acids are isomerized, resulting in
Harmonics and voltage stability analysis in power systems including ...
Indian Academy of Sciences (India)
These non-sinusoidal quantities can create serious harmonic distortions in transmission and distribution systems. In this paper, harmonic generation of a static VAR compensator with thyristor-controlled reactor and effects of the harmonics on steady-state voltage stability are examined for various operational conditions.
Dynamics, stability analysis and quantization of β-Fermi–Pasta ...
Indian Academy of Sciences (India)
We study the well-known one-dimensional problem of particles with nonlinear interaction. The -Fermi–Pasta–Ulam model is the special case of quadratic and quartic interaction potential among nearest neighbours. We enumerate and classify the simple periodic orbits for this system and find the stability zones, ...
Analysis and Optimization of Entry Stability in Underground Longwall Mining
Directory of Open Access Journals (Sweden)
Yubing Gao
2017-11-01
Full Text Available For sustainable utilization of limited coal resources, it is important to increase the coal recovery rate and reduce mine accidents, especially those occurring in the entry (gateroad. Entry stabilities are vital for ventilation, transportation and other essential services in underground coal mining. In the present study, a finite difference model was built to investigate stress evolutions around the entry, and true triaxial tests were carried out at the laboratory to explore entry wall stabilities under different mining conditions. The modeling and experimental results indicated that a wide coal pillar was favorable for entry stabilities, but oversize pillars caused a serious waste of coal resources. As the width of the entry wall decreased, the integrated vertical stress, induced by two adjacent mining panels, coupled with each other and experienced an increase on the entry wall, which inevitably weakened the stability of the entry. Therefore, mining with coal pillars always involves a tradeoff between economy and safety. To address this problem, an innovative non-pillar mining technique by optimizing the entry surrounding structures was proposed. Numerical simulation showed that the deformation of the entry roof decreased by approximately 66% after adopting the new approach, compared with that using the conventional mining method. Field monitoring indicated that the stress condition of the entry was signiﬁcantly improved and the average roof pressure decreased by appropriately 60.33% after adopting the new technique. This work provides an economical and effective approach to achieve sustainable exploitation of underground coal resources.
On the numerical stability analysis of pipelined Krylov subspace methods
Czech Academy of Sciences Publication Activity Database
Carson, E.T.; Rozložník, Miroslav; Strakoš, Z.; Tichý, P.; Tůma, M.
submitted 2017 (2018) R&D Projects: GA ČR GA13-06684S Grant - others:GA MŠk(CZ) LL1202 Institutional support: RVO:67985807 Keywords : Krylov subspace methods * the conjugate gradient method * numerical stability * inexact computations * delay of convergence * maximal attainable accuracy * pipelined Krylov subspace methods * exascale computations
Robust Stability Analysis of Nonlinear Switched Systems with Filippov Solutions
DEFF Research Database (Denmark)
Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal
2012-01-01
This paper addresses the stability problem of a class of nonlinear switched systems with partitioned state-space and state-dependent switching. In lieu of the Caratheodory solutions, the general Filippov solutions are considered. This encapsulates solutions with infinite switching in finite time....... which provides sufficient means to construct the corresponding Lyapunov functions via available semi-definite programming techniques....
Stability analysis of peer-to-peer networks against churn
Indian Academy of Sciences (India)
Developing analytical framework using generating function formalism. In this section, we use generating function formalism to derive the general formula for measuring the stability of overlay structures undergoing any kind of distur- bances in the network. We explain the basic concept behind the development of.
Post Earthquack Slope Stability Analysis of Rubble Mound Breakwater
Amin Moradi; Amir Mahmoudzadeh; Yahya Rahim Safavi
2017-01-01
Rubble mound breakwaters are structures built mainly of quarried rock. Generally armourstone or artificial concrete armour units are used for the outer armour layer,which should protect the structure againist wave attack. Armour stones and concrete armoure unites in this outer layer are usually placed with care to obtain effective interlocking and consequently better stability .
Stability analysis of direct current control in current source rectifier
DEFF Research Database (Denmark)
Lu, Dapeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
Current source rectifier with high switching frequency has a great potential for improving the power efficiency and power density in ac-dc power conversion. This paper analyzes the stability of direct current control based on the time delay effect. Small signal model including dynamic behaviors...
Stability Analysis of Equilibrium States of an SEIR Tuberculosis Model
African Journals Online (AJOL)
We examine the stability and equilibrium states of the extended model with respect to the basic reproduction number R0. We show that the disease-free equilibrium (DFE) is globally asymptotically stable if R0 ≤ 1 and that there exists at least one endemic equilibrium which is globally asymptotically stable if R0 > 1. Finally ...
Punctuality of railway operations and timetable stability analysis
Goverde, R.M.P.
2005-01-01
Reliability of railway operations becomes more and more demanding with increasing train traffic, which asks for stable and robust timetables capable of neutralizing deviations from scheduled time-distance paths and stabilizing delay propagation. Timetable performance evaluation is thus a crucial
Genotype x environment interaction and stability analysis for yield ...
African Journals Online (AJOL)
Chickpea is the major pulse crop cultivated in Ethiopia. However, its production is constrained due to genotype instability and environmental variability. This research was carried out to examine the magnitude of environmental effect on yield of chickpea genotypes and to investigate the stability and adaptability of genotypes ...
Consumption management in the Nord Pool region: A stability analysis
DEFF Research Database (Denmark)
Lindström, Erik; Madsen, Henrik; Norén, Vicke
2015-01-01
Integration of fluctuating renewables like wind and solar power is nowadays a hot topic, but this comes at a cost of decreased stability of the power system. The deterioration often translates into so-called spikes and drops in the electricity spot price, very large (even extreme) deviations from...
Harmonics and voltage stability analysis in power systems including
Indian Academy of Sciences (India)
In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of signiﬁcant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious harmonic ...
Harmonics and voltage stability analysis in power systems including ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
Abstract. In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of significant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious har-.
Dynamical behavior and Jacobi stability analysis of wound strings
Energy Technology Data Exchange (ETDEWEB)
Lake, Matthew J. [Naresuan University, The Institute for Fundamental Study, ' ' The Tah Poe Academia Institute' ' , Phitsanulok (Thailand); Thailand Center of Excellence in Physics, Ministry of Education, Bangkok (Thailand); Harko, Tiberiu [Babes-Bolyai University, Department of Physics, Cluj-Napoca (Romania); University College London, Department of Mathematics, London (United Kingdom)
2016-06-15
We numerically solve the equations of motion (EOM) for two models of circular cosmic string loops with windings in a simply connected internal space. Since the windings cannot be topologically stabilized, stability must be achieved (if at all) dynamically. As toy models for realistic compactifications, we consider windings on a small section of R{sup 2}, which is valid as an approximation to any simply connected internal manifold if the winding radius is sufficiently small, and windings on an S{sup 2} of constant radius R. We then use Kosambi-Cartan-Chern (KCC) theory to analyze the Jacobi stability of the string equations and determine bounds on the physical parameters that ensure dynamical stability of the windings. We find that, for the same initial conditions, the curvature and topology of the internal space have nontrivial effects on the microscopic behavior of the string in the higher dimensions, but that the macroscopic behavior is remarkably insensitive to the details of the motion in the compact space. This suggests that higher-dimensional signatures may be extremely difficult to detect in the effective (3+1)-dimensional dynamics of strings compactified on an internal space, even if configurations with nontrivial windings persist over long time periods. (orig.)
stability analysis of food barley genotypes in northern ethiopia
African Journals Online (AJOL)
ACSS
Barley (Hordeum vulgare L.) is one of the founder crops of the old world agriculture and was one of the first domesticated cereals. The objective of this study was to estimate the magnitude of genotype x environment interaction and stability for barley grain yield and yield related traits in the growing areas of Tigray. Eight.
Stability analysis of peer-to-peer networks against churn
Indian Academy of Sciences (India)
like Internet. In [14], researchers have addressed a more realistic scenario in which a network is subjected to simultaneous targeted and random attacks. The rest of the paper is organized as follows. In §2 we extend the analytical framework [5] to analyse the stability of peer-to-peer networks. Section 3 defines and models ...
Risk analysis to optimise safety during basic tunnel design
Molag, M.; Jansen, C.M.A.
1998-01-01
The risk analysis to select the preferred basic tunnel design for the tunnels in the High Speed Train Link South from Amsterdam to Antwerp is described. The risk analysis has been split up in two stages: a broad qualitative risk analysis and a quantitative risk analysis. The results of the
De Blaiser, Cedric; Roosen, Philip; Willems, Tine; Danneels, Lieven; Bossche, Luc Vanden; De Ridder, Roel
2018-03-01
To research and summarize the literature regarding the role of core stability as a risk factor in the development of lower extremity injuries in an athletic population. Pubmed, Web of Science and Embase were searched in August 2016 to systematically review studies, which related core muscle functioning and core stability to lower extremity injuries. Nine articles were included in the systematic review. Various components of core stability were found to be related to lower extremity musculoskeletal injuries in healthy athletic populations. Core strength, core proprioception and neuromuscular control of the core were found to be a risk factor in the development of lower extremity injuries. However, conflicting evidence was found for core endurance as a risk factor for lower extremity injuries. This systematic review provides preliminary evidence for the association between impaired core stability and the development of lower extremity injuries in healthy athletes. Deficits in various aspects of core stability were identified as potential risk factors for lower extremity injuries. As such, core stability needs to be considered when screening athletes. Copyright © 2017 Elsevier Ltd. All rights reserved.
Goto, Tomoko; Zheng, Xiaodong; Klyce, Stephen D; Kataoka, Hisashi; Uno, Toshihiko; Yamaguchi, Masahiko; Karon, Mike; Hirano, Sumie; Okamoto, Shigeki; Ohashi, Yuichi
2004-01-01
To evaluate the tear film stability of patients before and after laser in situ keratomileusis (LASIK) using the tear film stability analysis system (TSAS). Prospective observational case series. New videokeratography software for a topographic modeling system (TMS-2N) was developed that can automatically capture consecutive corneal surface images every second for 10 seconds. Thirty-four subjects (64 eyes) who underwent myopia LASIK were enrolled in this study. All subjects were examined with the new system before LASIK and at 1 week, 1 month, 3 months, and 6 months after the surgery. Corneal topographs were analyzed for tear breakup time (TMS breakup time) and breakup area (TMS breakup area). Based on pre-LASIK TSAS analysis, subjects were separated into normal and abnormal TSAS value groups. The criteria for the normal group were either TMS breakup time more than 5 seconds or TMS breakup area less than 0.2. The percentage of the occurrence of superficial punctuate keratitis was compared between the two groups with regard to subject's dry eye signs and symptoms. Tear film stability decreased significantly during the early period after LASIK, as indexed by decreased TMS breakup time and increased TMS breakup area. Tear film instability resolved at 6 months after surgery. Before LASIK, 22 subjects (43 eyes) had normal TSAS evaluation and 12 subjects (21 eyes) were abnormal. After LASIK, among normal TSAS value eyes, 8 of 43 (18.6%) eyes developed superficial punctuate keratitis. In sharp contrast, 14 of 21 (66.7%) eyes in the abnormal group displayed superficial punctuate keratitis, correlating well with the patients' dry eye symptoms. The difference in the presence of superficial punctuate keratitis after LASIK between normal and abnormal TSAS value groups was statistically significant (P <.001). Subjects with abnormal TSAS evaluation also displayed resistance to dry eye treatment and had extended period of recovery. Tear film stability analysis can be a useful
Multivariate survival analysis and competing risks
Crowder, Martin J
2012-01-01
Multivariate Survival Analysis and Competing Risks introduces univariate survival analysis and extends it to the multivariate case. It covers competing risks and counting processes and provides many real-world examples, exercises, and R code. The text discusses survival data, survival distributions, frailty models, parametric methods, multivariate data and distributions, copulas, continuous failure, parametric likelihood inference, and non- and semi-parametric methods. There are many books covering survival analysis, but very few that cover the multivariate case in any depth. Written for a graduate-level audience in statistics/biostatistics, this book includes practical exercises and R code for the examples. The author is renowned for his clear writing style, and this book continues that trend. It is an excellent reference for graduate students and researchers looking for grounding in this burgeoning field of research.
Supplemental Hazard Analysis and Risk Assessment - Hydrotreater
Energy Technology Data Exchange (ETDEWEB)
Lowry, Peter P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wagner, Katie A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2015-04-01
A supplemental hazard analysis was conducted and quantitative risk assessment performed in response to an independent review comment received by the Pacific Northwest National Laboratory (PNNL) from the U.S. Department of Energy Pacific Northwest Field Office (PNSO) against the Hydrotreater/Distillation Column Hazard Analysis Report issued in April 2013. The supplemental analysis used the hazardous conditions documented by the previous April 2013 report as a basis. The conditions were screened and grouped for the purpose of identifying whether additional prudent, practical hazard controls could be identified, using a quantitative risk evaluation to assess the adequacy of the controls and establish a lower level of concern for the likelihood of potential serious accidents. Calculations were performed to support conclusions where necessary.
Frequency scanning-based stability analysis method for grid-connected inverter system
DEFF Research Database (Denmark)
Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion with conside......This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion...... with consideration of the inverter nonlinearities. Small current disturbance is injected into grid-connected inverter system in a particular frequency range, and the impedance is computed according to the harmonic-frequency response using Fourier analysis, and then the stability is predicted on the basis...... of the impedance stability criterion. The stability issues of grid-connected inverters with grid-current feedback and the converter-current feedback are addressed using the proposed method. The results obtained from simulation and experiments validate the effectiveness of the method. The frequency scanning...
Risk and safety analysis of nuclear systems
Lee, John C
2011-01-01
The book has been developed in conjunction with NERS 462, a course offered every year to seniors and graduate students in the University of Michigan NERS program. The first half of the book covers the principles of risk analysis, the techniques used to develop and update a reliability data base, the reliability of multi-component systems, Markov methods used to analyze the unavailability of systems with repairs, fault trees and event trees used in probabilistic risk assessments (PRAs), and failure modes of systems. All of this material is general enough that it could be used in non-nuclear a
Terminological Ontologies for Risk and Vulnerability Analysis
DEFF Research Database (Denmark)
Madsen, Bodil Nistrup; Erdman Thomsen, Hanne
2014-01-01
Risk and vulnerability analyses are an important preliminary stage in civil contingency planning. The Danish Emergency Management Agency has developed a generic model and a set of tools that may be used in the preparedness planning, i.e. for identifying and describing society’s critical functions......, for formulating threat scenarios and for assessing consequences. Terminological ontologies, which are systems of domain specific concepts comprising concept relations and characteristics, are useful, both when describing the central concepts of risk and vulnerability analysis (meta concepts), and for further...
Rapid Pest Risk Analysis Xyleborinus attenuatus
Björklund Niklas; Boberg Johanna
2017-01-01
This rapid pest risk analysis (PRA) provides a quick assessment of the risks posed by the pest to Sweden, which is the PRA area being assessed. The format is an adapted version of the EPPO Express PRA scheme (EPPO 2012). Definition of terms used as well as the rating scheme and assessments are done in line with the guidance given in the EPPO CAPRA system (EPPO 2011). The likelihood of entry and establishment are assessed considering the current phytosanitary regulation in place with respect t...
Effects of Outlets on Cracking Risk and Integral Stability of Super-High Arch Dams
Directory of Open Access Journals (Sweden)
Peng Lin
2014-01-01
Full Text Available In this paper, case study on outlet cracking is first conducted for the Goupitan and Xiaowan arch dams. A nonlinear FEM method is then implemented to study effects of the outlets on integral stability of the Xiluodu arch dam under two loading conditions, i.e., normal loading and overloading conditions. On the basis of the case study and the numerical modelling, the outlet cracking mechanism, risk, and corresponding reinforcement measures are discussed. Furthermore, the numerical simulation reveals that (1 under the normal loading conditions, the optimal distribution of the outlets will contribute to the tensile stress release in the local zone of the dam stream surface and decrease the outlet cracking risk during the operation period. (2 Under the overloading conditions, the cracks initiate around the outlets, then propagate along the horizontal direction, and finally coalesce with those in adjacent outlets, where the yield zone of the dam has a shape of butterfly. Throughout this study, a dam outlet cracking risk control and reinforcement principle is proposed to optimize the outlet design, select the appropriate concrete material, strengthen the temperature control during construction period, design reasonable impounding scheme, and repair the cracks according to their classification.
Effects of outlets on cracking risk and integral stability of super-high arch dams.
Lin, Peng; Liu, Hongyuan; Li, Qingbin; Hu, Hang
2014-01-01
In this paper, case study on outlet cracking is first conducted for the Goupitan and Xiaowan arch dams. A nonlinear FEM method is then implemented to study effects of the outlets on integral stability of the Xiluodu arch dam under two loading conditions, i.e., normal loading and overloading conditions. On the basis of the case study and the numerical modelling, the outlet cracking mechanism, risk, and corresponding reinforcement measures are discussed. Furthermore, the numerical simulation reveals that (1) under the normal loading conditions, the optimal distribution of the outlets will contribute to the tensile stress release in the local zone of the dam stream surface and decrease the outlet cracking risk during the operation period. (2) Under the overloading conditions, the cracks initiate around the outlets, then propagate along the horizontal direction, and finally coalesce with those in adjacent outlets, where the yield zone of the dam has a shape of butterfly. Throughout this study, a dam outlet cracking risk control and reinforcement principle is proposed to optimize the outlet design, select the appropriate concrete material, strengthen the temperature control during construction period, design reasonable impounding scheme, and repair the cracks according to their classification.
Stability and Change in Work Values: A Meta-Analysis of Longitudinal Studies
Jin, Jing; Rounds, James
2012-01-01
A meta-analysis of longitudinal studies was conducted to investigate stability and change in work values across the life span. Both rank-order stability and mean-level change were investigated using an integrative classification for intrinsic, extrinsic, social and status work values (Ross, Schwartz, & Surkis, 1999). Results of rank-order…
International Nuclear Information System (INIS)
Hennig, D.
1997-01-01
In boiling water reactors, there is a region in the operating map for which the reactor exhibits stable or unstable power oscillations. This oscillatory behaviour had to be understood in detail, in order to estimate, in a reliable way, the stability limits. This paper describes the BWR stability analysis methodology used at PSI and presents some recent results. (author) figs., tab., 38 refs
Stability and Robustness Analysis Tools for Marine Robot Localization and Mapping Applications
2009-06-01
control process. Stability of the linear Kalman filter in the specialized case of a one degree-of-freedom monobot was assessed by Vidal- Calleja , Andrade...2), 2008, pp. 175-196. [35] T. Vidal- Calleja , J. Andrade-Cetto, and A. Sanfeliu, “Estimator Stability Analysis in SLAM,” Proc. 5th IFAC/EURON Symp
Jose, Anita; O'Leary, K. Daniel; Moyer, Anne
2010-01-01
Cohabitation with a romantic partner has become common in recent decades. This meta-analysis examined the link between premarital cohabitation and marital stability (k = 16) and marital quality (k = 12). Cohabitation had a significant negative association with both marital stability and marital quality. The negative predictive effect on marital…
Stability analysis of natural convection in superposed fluid and porous layers
International Nuclear Information System (INIS)
Hirata, S.C.; Goyeau, B.; Gobin, D.; Cotta, R.M.
2005-01-01
A linear stability analysis of the onset of thermal natural convection in superposed fluid and porous layers is called out. The resulting eigenvalue problem is solved using a integral transformation technique. The effect of the variation of the Darcy number on the stability of the system is analyzed. (authors)
Stability analysis of natural convection in superposed fluid and porous layers
Energy Technology Data Exchange (ETDEWEB)
Hirata, S.C.; Goyeau, B.; Gobin, D. [Paris-11 Univ. - Paris-6, FAST - UMR CNRS 7608, 91 - Orsay (France); Cotta, R.M. [Rio de Janeiro Univ. (LTTC/PEM/EE/COPPE/UFRJ), RJ (Brazil)
2005-07-01
A linear stability analysis of the onset of thermal natural convection in superposed fluid and porous layers is called out. The resulting eigenvalue problem is solved using a integral transformation technique. The effect of the variation of the Darcy number on the stability of the system is analyzed. (authors)
Stability analysis of f(R)-AdS black holes
Energy Technology Data Exchange (ETDEWEB)
Moon, Taeyoon; Son, Edwin J. [Sogang University, Center for Quantum Space-time, Seoul (Korea, Republic of); Myung, Yun Soo [Inje University, Institute of Basic Sciences and School of Computer Aided Science, Gimhae (Korea, Republic of)
2011-10-15
We study the stability of the f(R)-AdS (Schwarzschild-AdS) black hole obtained from f(R) gravity. In order to resolve the difficulty of solving fourth-order linearized equations, we transform f(R) gravity into scalar-tensor theory by introducing two auxiliary scalars. In this case, the linearized curvature scalar becomes a dynamical scalaron, showing that all linearized equations are second order. Using the positivity of gravitational potentials and S-deformed technique allows us to guarantee the stability of f(R)-AdS black hole if the scalaron mass squared satisfies the Breitenlohner-Freedman bound. This is confirmed by computing quasinormal frequencies of the scalaron for the f(R)-AdS black hole. (orig.)
Stability analysis of a dike constructed of anthropogenic materials
Directory of Open Access Journals (Sweden)
Danilewicz Andrzej
2017-01-01
Full Text Available Numerical analyses of stability are presented for a hypothetical dikes constructed of dredged materials and bottom ash, in varying proportions. The paper is related to the international research project DredgDikes, which focused on the use of anthropogenic materials in dikes construction and flood protection. The aim of this project was to investigate the possibility of using anthropogenic materials from rivers and sea dredging and coal combustion products in dikes construction. The influence of different proportions of ash and dredged materials on the stability of dike is discussed. Mechanical and hydraulic parameters of various dredged material-ash mixtures are based on the results of laboratory and field tests performed in DredgDikes project. Numerical calculations are carried out using geotechnical software Plaxis. Cementation phenomenon and its effect on the performance of ash and dredged material mixtures is discussed.
Stability analysis of rough surfaces in adhesive normal contact
Rey, Valentine; Bleyer, Jeremy
2018-03-01
This paper deals with adhesive frictionless normal contact between one elastic flat solid and one stiff solid with rough surface. After computation of the equilibrium solution of the energy minimization principle and respecting the contact constraints, we aim at studying the stability of this equilibrium solution. This study of stability implies solving an eigenvalue problem with inequality constraints. To achieve this goal, we propose a proximal algorithm which enables qualifying the solution as stable or unstable and that gives the instability modes. This method has a low computational cost since no linear system inversion is required and is also suitable for parallel implementation. Illustrations are given for the Hertzian contact and for rough contact.
Ballooning stability analysis of JET H-mode discharges
International Nuclear Information System (INIS)
O'Brien, D.P.; Galvao, R.; Keilhacker, M.; Lazzaro, E.; Watkins, M.L.
1989-01-01
Previous studies of the stability of a large aspect ratio model equilibrium to ideal MHD ballooning modes have shown that across the bulk of the plasma there exist two marginally stable values of the pressure gradient parameter α. These define an unstable zone which separates the first (small α) stable region from the second (large α) stable region. Close to the separatrix, however, the first and second regions can coalesce when the surface averaged current density, Λ, exceeds a critical value. The plasma in this region is then stable to ballooning modes at all values of the pressure gradient. In this paper we extend these results to JET H-mode equilibria using a finite aspect ratio ballooning formalism, and assess the relevance of ideal ballooning stability in these discharges. In particular we analyse shot 15894 at time 56 sec. which is 1.3 s into the H-phase. (author) 4 refs., 4 figs
Harmonics and voltage stability analysis in power systems including ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
1. Introduction. It is not only required to meet the demand for electrical energy but also to improve its quality. .... It is necessary to pay attention to energy system stability in the planning, management, and control of electrical ... where k ∈ {m, m + 1,... ,n} and n is total number of the buses in the system. F(h) r,k and F(h) i,k.
Stability and bifurcation analysis in a delayed SIR model
International Nuclear Information System (INIS)
Jiang Zhichao; Wei Junjie
2008-01-01
In this paper, a time-delayed SIR model with a nonlinear incidence rate is considered. The existence of Hopf bifurcations at the endemic equilibrium is established by analyzing the distribution of the characteristic values. A explicit algorithm for determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions are derived by using the normal form and the center manifold theory. Numerical simulations to support the analytical conclusions are carried out
The asymptotic stability analysis in stochastic logistic model with Poisson growth coefficient
Directory of Open Access Journals (Sweden)
Shaojuan Ma
2014-01-01
Full Text Available The asymptotic stability of a discrete logistic model with random growth coefficient is studied in this paper. Firstly, the discrete logistic model with random growth coefficient is built and reduced into its deterministic equivalent system by orthogonal polynomial approximation. Then, the linear stability theory and the Jury criterion of nonlinear deterministic discrete systems are applied to the equivalent one. At last, by mathematical analysis, we find that the parameter interval for asymptotic stability of nontrivial equilibrium in stochastic logistic system gets smaller as the random intensity or statistical parameters of random variable is increased and the random parameter's influence on asymptotic stability in stochastic logistic system becomes prominent.
Advanced techniques for the analysis of crisis stability, deterrence, and latency
Energy Technology Data Exchange (ETDEWEB)
Canavan, G.H.
1998-12-31
This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The principal results of studies on crisis stability, deterrence, and latency are presented in their order of development. They capture the main features of stability analysis; relate first strike, crisis, and arms control stability as seen from US and Russian perspective; and address whether different metrics, uncertain damage preferences, or the deployment of defenses can be destabilizing. The report explores differences between unilateral and proportional force reductions in the region of deep reductions where concern shifts from stability to latency.
Phasor model of full scale converter wind turbine for small-signal stability analysis
Gihga, Radu; Wu, Qiuwei; Nielsen, Arne Hejde
2017-01-01
The small-signal stability analysis of power system electromechanical oscillations is a well-established field in control and stability assessment of power systems. The impact of large wind farms on small-signal stability of power systems has been a topic of high interest in recent years. This study presents a phasor model of full scale converter wind turbines (WTs) implemented in MATLAB/SIMULINK for small-signal stability studies. The phasor method is typically used for dynamic studies of po...
Seismic stability analysis of concrete gravity dams with penetrated cracks
Directory of Open Access Journals (Sweden)
Shou-yan Jiang
2012-03-01
Full Text Available The seismic stability of a cracked dam was examined in this study. Geometric nonlinearity and large deformations, as well as the contact condition at the crack site, were taken into consideration. The location of penetrated cracks was first identified using the concrete plastic-damage model based on the nonlinear finite element method (FEM. Then, the hard contact algorithm was used to simulate the crack interaction in the normal direction, and the Coloumb friction model was used to simulate the crack interaction in the tangential direction. After verification of numerical models through a case study, the seismic stability of the Koyna Dam with two types of penetrated cracks is discussed in detail with different seismic peak accelerations, and the collapse processes of the cracked dam are also presented. The results show that the stability of the dam with two types of penetrated cracks can be ensured in an earthquake with a magnitude of the original Koyna earthquake, and the cracked dam has a large earthquake-resistant margin. The failure processes of the cracked dam in strong earthquakes can be divided into two stages: the sliding stage and the overturning stage. The sliding stage ends near the peak acceleration, and the top block slides a long distance along the crack before the collapse occurs. The maximum sliding displacement of the top block will decrease with an increasing friction coefficient at the crack site.
Stability Analysis of Learning Algorithms for Ontology Similarity Computation
Directory of Open Access Journals (Sweden)
Wei Gao
2013-01-01
Full Text Available Ontology, as a useful tool, is widely applied in lots of areas such as social science, computer science, and medical science. Ontology concept similarity calculation is the key part of the algorithms in these applications. A recent approach is to make use of similarity between vertices on ontology graphs. It is, instead of pairwise computations, based on a function that maps the vertex set of an ontology graph to real numbers. In order to obtain this, the ranking learning problem plays an important and essential role, especially k-partite ranking algorithm, which is suitable for solving some ontology problems. A ranking function is usually used to map the vertices of an ontology graph to numbers and assign ranks of the vertices through their scores. Through studying a training sample, such a function can be learned. It contains a subset of vertices of the ontology graph. A good ranking function means small ranking mistakes and good stability. For ranking algorithms, which are in a well-stable state, we study generalization bounds via some concepts of algorithmic stability. We also find that kernel-based ranking algorithms stated as regularization schemes in reproducing kernel Hilbert spaces satisfy stability conditions and have great generalization abilities.
Numerical Analysis on the Stability of Hydraulic Fracture Propagation
Directory of Open Access Journals (Sweden)
Zhaobin Zhang
2015-09-01
Full Text Available The formation of dense spacing fracture network is crucial to the hydraulic fracturing treatment of unconventional reservoir. However, one difficulty for fracturing treatment is the lack of clear understanding on the nature of fracture complexity created during the treatment. In this paper, fracture propagation is numerically investigated to find the conditions needed for the stable propagation of complex fracture network. Firstly, starting from a parallel fracture system, the stability of fracture propagation is analyzed and a dimensionless number M is obtained. Then, by developing a hydraulic fracturing simulation model based on displacement discontinuity method, the propagation of parallel fractures is simulated and a clear relation between M and the stability of parallel fractures is obtained. Finally, the investigation on parallel fractures is extended to complex fracture networks. The propagation of complex fracture networks is simulated and the results show that the effects of M on complex fracture networks is the same to that of parallel fractures. The clear relation between M and fracture propagation stability is important for the optimization of hydraulic fracturing operation.
Stability analysis of underground mining openings with complex geometry
Directory of Open Access Journals (Sweden)
Cała Marek
2016-03-01
Full Text Available Stability of mining openings requires consideration of a number of factors, such as: geological structure, the geometry of the underground mining workings, mechanical properties of the rock mass, changes in stress caused by the influence of neighbouring workings. Long-term prediction and estimation of workings state can be analysed with the use of numerical methods. Application of 3D numerical modelling in stability estimation of workings with complex geometry was described with the example of Crystal Caves in Wieliczka Salt Mine. Preservation of the Crystal Caves reserve is particularly important in view of their unique character and the protection of adjacent galleries which are a part of tourist attraction included in UNESCO list. A detailed 3D model of Crystal Caves and neighbouring workings was built. Application of FLAC3D modelling techniques enabled indication of the areas which are in danger of stability loss. Moreover, the area in which protective actions should be taken as well as recommendations concerning the convergence monitoring were proposed.
Housing stability over two years and HIV risk among newly homeless youth.
Rosenthal, Doreen; Rotheram-Borus, Mary Jane; Batterham, Philip; Mallett, Shelley; Rice, Eric; Milburn, Norweeta G
2007-11-01
The stability of living situation was examined as a predictor of young people's HIV-related sexual and drug use acts two years after leaving home for the first time. Newly homeless youth aged 12-20 years were recruited in Los Angeles County, California, U.S.A. (n = 261) and Melbourne, Australia (n = 165) and followed longitudinally at 3, 6, 12, 18, and 24 months. Their family history of moves and the type and frequency of moves over the two years following becoming newly homeless were examined. Regression analyses indicated that recent sexual risk two years after becoming newly homeless was not related to the instability of youths' living situations; condom use was higher among youth with more placements in institutional settings and among males. Drug use was significantly related to having moved more often over two years and Melbourne youth used drugs significantly more than youth in Los Angeles.
Risk analysis for earth dam overtopping
Directory of Open Access Journals (Sweden)
Mo Chongxun
2008-06-01
Full Text Available In this paper, a model of overtopping risk under the joint effects of floods and wind waves, which is based on risk analysis theory and takes into account the uncertainties of floods, wind waves, reservoir capacity and discharge capacity of the spillway, is proposed and applied to the Chengbihe Reservoir in Baise City in Guangxi Zhuang Autonomous Region. The simulated results indicate that the flood control limiting level can be raised by 0.40 m under the condition that the reservoir overtopping risk is controlled within a mean variance of 5×10−6. As a result, the reservoir storage will increase to 16 million m3 and electrical energy generation and other functions of the reservoir will also increase greatly.
Quantitative Risk Analysis: Method And Process
Directory of Open Access Journals (Sweden)
Anass BAYAGA
2010-03-01
Full Text Available Recent and past studies (King III report, 2009: 73-75; Stoney 2007;Committee of Sponsoring Organisation-COSO, 2004, Bartell, 2003; Liebenberg and Hoyt, 2003; Reason, 2000; Markowitz 1957 lament that although, the introduction of quantifying risk to enhance degree of objectivity in finance for instance was quite parallel to its development in the manufacturing industry, it is not the same in Higher Education Institution (HEI. In this regard, the objective of the paper was to demonstrate the methods and process of Quantitative Risk Analysis (QRA through likelihood of occurrence of risk (phase I. This paper serves as first of a two-phased study, which sampled hundred (100 risk analysts in a University in the greater Eastern Cape Province of South Africa.The analysis of likelihood of occurrence of risk by logistic regression and percentages were conducted to investigate whether there were a significant difference or not between groups (analyst in respect of QRA.The Hosmer and Lemeshow test was non-significant with a chi-square(X2 =8.181; p = 0.300, which indicated that there was a good model fit, since the data did not significantly deviate from the model. The study concluded that to derive an overall likelihood rating that indicated the probability that a potential risk may be exercised within the construct of an associated threat environment, the following governing factors must be considered: (1 threat source motivation and capability (2 nature of the vulnerability (3 existence and effectiveness of current controls (methods and process.
Long term stability analysis of cast iron shaft linings after Coal Mine closure and flooding
International Nuclear Information System (INIS)
Hadj-Hassen, F.; Bienvenu, Y.; Noirel, J.F.; Metz, M.
2005-01-01
This paper presents the results of a study conducted to analyse the long term stability of the cast iron shaft lining after coal mine closure and flooding. The attention is mainly focused on the behaviour during the critical phase of flooding as well as the phase corresponding to the disappearance of the water pressure and the stabilization of the environment. This pluri-disciplinary study was conducted by a team combining specialists in rock mechanics who identified the main risks and the conditions of stability of the lining and specialists in metallurgy who studied the composition of the cast iron and its corrosion behaviour after exposure to mine water. (authors)
Risk analysis as a decision tool
International Nuclear Information System (INIS)
Yadigaroglu, G.; Chakraborty, S.
1985-01-01
From 1983 - 1985 a lecture series entitled ''Risk-benefit analysis'' was held at the Swiss Federal Institute of Technology (ETH), Zurich, in cooperation with the Central Department for the Safety of Nuclear Installations of the Swiss Federal Agency of Energy Economy. In that setting the value of risk-oriented evaluation models as a decision tool in safety questions was discussed on a broad basis. Experts of international reputation from the Federal Republic of Germany, France, Canada, the United States and Switzerland have contributed to report in this joint volume on the uses of such models. Following an introductory synopsis on risk analysis and risk assessment the book deals with practical examples in the fields of medicine, nuclear power, chemistry, transport and civil engineering. Particular attention is paid to the dialogue between analysts and decision makers taking into account the economic-technical aspects and social values. The recent chemical disaster in the Indian city of Bhopal again signals the necessity of such analyses. All the lectures were recorded individually. (orig./HP) [de
Risk analysis in oil spill response planning
International Nuclear Information System (INIS)
Chernoplekov, A.N.; Alexandrov, A.A.
2005-01-01
Tiered response is a basic approach to emergency plans, including oil spill response (OSR). This paper delineates a huge set of accidental scenarios within a certain tier of response generated by a computer during risk assessment. Parameters such as the amount of oil spilled, duration of discharge and types of losses should be provided in OSR scenarios. Examples of applications include offshore installations, sub sea or onshore pipelines, and localized onshore facilities. The paper demonstrates how to use risk analysis results for delineating all likely spills into groups that need a specific tier response. The best world practices and Russian regulatory approaches were outlined and compared. Corresponding algorithms were developed and their application in pipelines was presented. The algorithm combines expert's skills and spill trajectory modeling with the net environmental benefit analysis principle into the incident specific emergency response planning. 9 refs., 13 tabs., 2 figs
Integrated Reliability and Risk Analysis System (IRRAS)
International Nuclear Information System (INIS)
Russell, K.D.; McKay, M.K.; Sattison, M.B.; Skinner, N.L.; Wood, S.T.; Rasmuson, D.M.
1992-01-01
The Integrated Reliability and Risk Analysis System (IRRAS) is a state-of-the-art, microcomputer-based probabilistic risk assessment (PRA) model development and analysis tool to address key nuclear plant safety issues. IRRAS is an integrated software tool that gives the user the ability to create and analyze fault trees and accident sequences using a microcomputer. This program provides functions that range from graphical fault tree construction to cut set generation and quantification. Version 1.0 of the IRRAS program was released in February of 1987. Since that time, many user comments and enhancements have been incorporated into the program providing a much more powerful and user-friendly system. This version has been designated IRRAS 4.0 and is the subject of this Reference Manual. Version 4.0 of IRRAS provides the same capabilities as Version 1.0 and adds a relational data base facility for managing the data, improved functionality, and improved algorithm performance
Risk analysis of external radiation therapy
International Nuclear Information System (INIS)
Arvidsson, Marcus
2011-09-01
External radiation therapy is carried out via a complex treatment process in which many different groups of staff work together. Much of the work is dependent on and in collaboration with advanced technical equipment. The purpose of the research task has been to identify a process for external radiation therapy and to identify, test and analyze a suitable method for performing risk analysis of external radiation therapy
Risk Analysis of Accounting Information System Infrastructure
MIHALACHE, Arsenie-Samoil
2011-01-01
National economy and security are fully dependent on information technology and infrastructure. At the core of the information infrastructure society relies on, we have the Internet, a system designed initially as a scientists’ forum for unclassified research. The use of communication networks and systems may lead to hazardous situations that generate undesirable effects such as communication systems breakdown, loss of data or taking the wrong decisions. The paper studies the risk analysis of...
Risk and value analysis of SETI
Billingham, J.
1990-01-01
This paper attempts to apply a traditional risk and value analysis to the Search for Extraterrestrial Intelligence--SETI. In view of the difficulties of assessing the probability of success, a comparison is made between SETI and a previous search for extraterrestrial life, the biological component of Project Viking. Our application of simple Utility Theory, given some reasonable assumptions, suggests that SETI is at least as worthwhile as the biological experiment on Viking.
14 CFR Appendix C to Part 420 - Risk Analysis
2010-01-01
... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Risk Analysis C Appendix C to Part 420... TRANSPORTATION LICENSING LICENSE TO OPERATE A LAUNCH SITE Pt. 420, App. C Appendix C to Part 420—Risk Analysis (a... risk is minimal. (2) An applicant shall perform a risk analysis when a populated area is located within...
Pest Risk Analysis - a Way to Counter Attack Losses Caused
FLEŞERIU A.; I. OROIAN; Oana VIMAN; I. BRAŞOVEAN
2010-01-01
Risk analysis against pathogens is a process of investigation, assessment and decision-making information on apest that begins when it is known or determined that it is a quarantine pest. Pest risk analysis is meaningful only inrelation to an area considered to be at risk. The annual losses are about 35% but can be greatly reduced after applicationof pest risk analysis.
Analysis of a Major Electric Grid -- Stability and Adaptive Protection
Alanzi, Sultan
system conditions. This dissertation introduces a combination of quadrilateral and mho characteristics to create a distance relay with a mushroom shape in R-X diagrams. This new relay offers larger protective reach with a lower limitation on loadability. When major disturbances occur, the power balance between load and generation might be disturbed causing the generators to lose synchronism (to be out-of-step) with each other. Out-of-step protection against power swings is essential to provide supervising signals for distance relays to mitigate the effects of the disturbance. A new R-X criterion is proposed to identify out-of-step conditions for large and complex power systems, such as KEG. A proposed Adaptive Out-of-Step Relay (AOSR) will monitor power system conditions and adjust the relay reach accordingly for better power swing classification. When unstable swings are detected, controllable tripping signals are initiated and system separation will create small subsystems or islands of the power system. These smaller systems will be created to achieve a balance of load and available generation. The electric power system chosen to study and to illustrate the criteria for the proposed adaptive relays was that of the country of Kuwait. The small oil-rich country of Kuwait has been dealing with an electric energy crisis that started summer 2006. With a dry dessert climate and intensely hot summers, the 3.6 million residents of Kuwait depend on continuously operated A/C units for living. This is the major reason why the peak load in a summer month reaches almost 11,000 MW while the peak load in a winter month does not exceed 5,000 MW. The Kuwait Electric Grid (KEG) is modelled and analyzed using Power Analytics' software known as PaladinRTM DesignBase(TM). Performance studies produce data to examine distance and out-of-step protection. Power Flow (PF), Short Circuit Analysis (SCA), and Transient Stability Analysis (TSA) are used to verify the model of KEG. These studies
LANDSAFE: LANDING SITE RISK ANALYSIS SOFTWARE FRAMEWORK
Directory of Open Access Journals (Sweden)
R. Schmidt
2012-08-01
Full Text Available The European Space Agency (ESA is planning a Lunar Lander mission in the 2018 timeframe that will demonstrate precise soft landing at the polar regions of the Moon. To ensure a safe and successful landing a careful risk analysis has to be carried out. This is comprised of identifying favorable target areas and evaluating the surface conditions in these areas. Features like craters, boulders, steep slopes, rough surfaces and shadow areas have to be identified in order to assess the risk associated to a landing site in terms of a successful touchdown and subsequent surface operation of the lander. In addition, global illumination conditions at the landing site have to be simulated and analyzed. The Landing Site Risk Analysis software framework (LandSAfe is a system for the analysis, selection and certification of safe landing sites on the lunar surface. LandSAfe generates several data products including high resolution digital terrain models (DTMs, hazard maps, illumination maps, temperature maps and surface reflectance maps which assist the user in evaluating potential landing site candidates. This paper presents the LandSAfe system and describes the methods and products of the different modules. For one candidate landing site on the rim of Shackleton crater at the south pole of the Moon a high resolution DTM is showcased.
This Applications Analysis Report evaluates the solidification/stabilization treatment process of Silicate Technology Corporation (STC) for the on-site treatment of hazardous waste. The STC immobilization technology utilizes a proprietary product (FMS Silicate) to chemically stab...
Color stability of esthetic restorative materials: a spectrophotometric analysis.
Poggio, Claudio; Ceci, Matteo; Beltrami, Riccardo; Mirando, Maria; Wassim, Jaffal; Colombo, Marco
2016-12-01
Objective: The aim of this in vitro study was to evaluate the color stability of different restorative materials (one microfilled composite, one nanofilled composite, one nanohybrid composite and one Ormocer-based composite) after exposure to different staining solutions (coffee, coca-cola and red wine). Material and methods: All materials were polymerized into silicon rings (2 mm ×6 mm ×8 mm) to obtain specimens identical in size. Thirty cylindrical specimens of each material were prepared. They were immersed in staining solutions over a 28-day test period. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. The Shapiro-Wilk test and Kruskal-Wallis ANOVA were applied to assess significant differences among restorative materials. The paired t -test was applied to test which CIE L*a*b* parameters significantly changed after immersion in staining solutions. Results: All restorative materials showed clinically perceptible color differences after immersion in coffee. L* and b* values showed the highest variability. Coca cola and red wine did not influence the color stability for all restorative materials except for Filtek Supreme XTE. Conclusions: Coffee caused a significant color change in all types of tested composite resins. Filtek Supreme XTE demonstrated alone a staining susceptibility to red wine; no other significant differences among the materials were demonstrated. Long-term exposure to some food dyes (coffee in particular) can significantly affect the color stability of modern esthetic restorative materials regardless of materials' different composition.
Local Stability Analysis of an SVIR Epidemic Model
Directory of Open Access Journals (Sweden)
Joko Harianto
2017-11-01
Full Text Available In this paper, we present an SVIR epidemic model with deadly deseases. Initially the basic formulation of the model is presented. Two equilibrium point exists for the system; disease free and endemic equilibrium. The local stability of the disease free and endemic equilibrium exists when the basic reproduction number less or greater than unity, respectively. If the value of R0 less than one then the desease free equilibrium is locally stable, and if its exceeds, the endemic equilibrium is locally stable. The numerical results are presented for illustration.
Stability analysis of a class of fractional delay differential equations
Indian Academy of Sciences (India)
equation (8) satisfy. Re(λi ) < 0, ∀i. (9). Let λ = u + ıv, u,v ∈ . A change in stability can occur only when the value of λ crosses the imaginary axis at λ = ıv and the characteristic equation becomes. (ıv)α + b = af (y. ∗) exp(−ıvτ). (10). Using ıv = v exp(ıπ/2), v ∈ and separating real and imaginary parts in (10) we get b + vα cos. (.
Adaptive Central Force Optimization Algorithm Based on the Stability Analysis
Directory of Open Access Journals (Sweden)
Weiyi Qian
2015-01-01
Full Text Available In order to enhance the convergence capability of the central force optimization (CFO algorithm, an adaptive central force optimization (ACFO algorithm is presented by introducing an adaptive weight and defining an adaptive gravitational constant. The adaptive weight and gravitational constant are selected based on the stability theory of discrete time-varying dynamic systems. The convergence capability of ACFO algorithm is compared with the other improved CFO algorithm and evolutionary-based algorithm using 23 unimodal and multimodal benchmark functions. Experiments results show that ACFO substantially enhances the performance of CFO in terms of global optimality and solution accuracy.
Bifurcation and stability analysis of a nonlinear milling process
Weremczuk, Andrzej; Rusinek, Rafal; Warminski, Jerzy
2018-01-01
Numerical investigations of milling operations dynamics are presented in this paper. A two degree of freedom nonlinear model is used to study workpiece-tool vibrations. The analyzed model takes into account both flexibility of the tool and the workpiece. The dynamics of the milling process is described by the discontinuous ordinary differential equation with time delay, which can cause process instability. First, stability lobes diagrams are created on the basis of the parameters determined in impact test of an end mill and workpiece. Next, the bifurcations diagrams are performed for different values of rotational speeds.
Analysis of Energy Stabilization inside the Hydrophobic Core of Rubredoxin
Czech Academy of Sciences Publication Activity Database
Berka, Karel; Hobza, Pavel; Vondrášek, Jiří
2009-01-01
Roč. 10, č. 3 (2009), s. 543-548 ISSN 1439-4235 R&D Projects: GA ČR GA203/05/0009; GA ČR GA203/06/1727; GA ČR(CZ) GD203/05/H001; GA AV ČR IAA400550510; GA MŠk LC512 Institutional research plan: CEZ:AV0Z40550506 Keywords : hydrophobic core * protein stability * SAPT method Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.453, year: 2009
Analysis of smoke trailers at individual classes of atmosphere stability
International Nuclear Information System (INIS)
Carach, V.; Macala, J.
2007-01-01
At the present most endangered element of the environment is currently atmosphere and its pollution that rapidly accrue. Pollutants are emitted from air pollution sources. The output of pollutant from air pollution source is creating so-called smoke screen. Smoke screens can be observed from point sources of air pollution - smokestacks, up-cast. The purpose of this article was to build theoretical models of smoke screens rise from point source at different meteorological conditions characterized with fifth classes of atmosphere stability. (authors)
An Impedance-Based Stability Analysis Method for Paralleled Voltage Source Converters
DEFF Research Database (Denmark)
Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang
2014-01-01
This paper analyses the stability of paralleled voltage source converters in AC distributed power systems. An impedance-based stability analysis method is presented based on the Nyquist criterion for multiloop system. Instead of deriving the impedance ratio as usual, the system stability...... of converter and the passive network can also be predicted by the Nyquist diagrams. This method is applied to evaluate the current and voltage controller interactions of converters in both grid-connected and islanded operations. Simulations and experimental results verify the effectiveness of theoretical...... analysis....
Can posterior dynamic stabilization reduce the risk of adjacent segment deterioration?
Zhou, Zhi-Jie; Xia, Ping; Zhao, Xing; Fang, Xiang-Qian; Zhao, Feng-Dong; Fan, Shun-Wu
2013-01-01
The aim of this study was to systematically review the relevant literature to develop a benchmark for the incidence of adjacent segment degeneration (ASDeg) and adjacent segment disease (ASDis) following the posterior dynamic stabilization (PDS) procedure and to investigate whether conclusions can be made with regard to the isolated PDS procedure in reducing the risk of ASDeg and ASDis compared with fusion, and with regard to the role of additional PDS devices implanted adjacent to fusion in protecting from ASDeg and ASDis caused by the neighboring fusion. We retrieved electronic databases of Medline, Ovid and Cochrane Central Registry of Controlled Trials, combined with a supplemental hand search. Thirty-one articles met our inclusion criteria. The pooled incidence of ASDeg and ASDis following PDS procedure was 16.4% and 5.5% respectively. Data from comparative studies showed a significantly lower incidence of ASDeg and nonsignificantly lower incidence of ASDis following PDS than following fusion surgery. Further, the additional PDS devices implanted adjacent to fusion could significantly reduce the risk of ASDeg and nonsignificantly decrease that of ASDis caused by fusion. These results suggested relative success of the PDS procedure in protecting against ASDeg and ASDis.
A new approach on the stability analysis in ELKO cosmology
Energy Technology Data Exchange (ETDEWEB)
Santos Souza, A.P. dos; Pereira, S.H. [UNESP-Univ. Estadual Paulista ' ' Julio de Mesquita Filho' ' , Departamento de Fisica e Quimica, Faculdade de Engenharia de Guaratingueta, Guaratingueta, SP (Brazil); Jesus, J.F. [Universidade Estadual Paulista ' ' Julio de Mesquita Filho' ' , Itapeva, SP (Brazil)
2015-01-01
In this work it has been developed a new approach to study the stability of a system composed by an ELKO field interacting with dark matter, which could give some contribution in order to alleviate the cosmic coincidence problem. It is assumed that the potential which characterizes the ELKO field is not specified, but it is related to a constant parameter δ. The strength of the interaction between matter and ELKO field is characterized by a constant parameter β and it is also assumed that both ELKO field and matter energy density are related to their pressures by equations of state parameters ω{sub φ} and ω{sub m}, respectively. The system of equations is analyzed by a dynamical system approach. It has been found the conditions of stability between the parameters δ and β in order to have stable fixed points for the system for different values of the equation of state parameters ω{sub φ} and ω{sub m}, and the results are presented in form of tables. The possibility of decay of the ELKO field into dark matter or vice versa can be read directly from the tables, since the parameters δ and β satisfy some inequalities. It allows us to constrain the potential assuming that we have a stable system for different interactions terms between the ELKO field and dark matter. The cosmic coincidence problem can be alleviated for some specific relations between the parameters of the model. (orig.)
State stability analysis for the fermionic projector in the continuum
Energy Technology Data Exchange (ETDEWEB)
Hoch, Stefan Ludwig
2008-07-01
The principle of the fermionic projector in the continuum gives an indication that there might be a deeper reason why elementary particles only appear with a few definite masses. In this thesis the existence of approximately state-stable configurations is shown. In order to achieve that, we make use of a variational principle for the fermionic projector in the continuum which contains certain contributions supported on the light cone. In a certain sense, these extra terms contain the structure of the underlying discrete spacetime. Lorentz invariant distributions and their convolutions are studied. Some of these are well-defined because the convolution integrals have compactly supported integrands. Other convolutions can be regularized such that the property of being ill-defined only plays a role on the light cone. These results are used to analyze the variational principle and to give criteria for state stability, which can be numerically analyzed. Some plots are presented to allow a decision about state stability and to show how possible configurations could look like. (orig.)
Electricity Market Stochastic Dynamic Model and Its Mean Stability Analysis
Directory of Open Access Journals (Sweden)
Zhanhui Lu
2014-01-01
Full Text Available Based on the deterministic dynamic model of electricity market proposed by Alvarado, a stochastic electricity market model, considering the random nature of demand sides, is presented in this paper on the assumption that generator cost function and consumer utility function are quadratic functions. The stochastic electricity market model is a generalization of the deterministic dynamic model. Using the theory of stochastic differential equations, stochastic process theory, and eigenvalue techniques, the determining conditions of the mean stability for this electricity market model under small Gauss type random excitation are provided and testified theoretically. That is, if the demand elasticity of suppliers is nonnegative and the demand elasticity of consumers is negative, then the stochastic electricity market model is mean stable. It implies that the stability can be judged directly by initial data without any computation. Taking deterministic electricity market data combined with small Gauss type random excitation as numerical samples to interpret random phenomena from a statistical perspective, the results indicate the conclusions above are correct, valid, and practical.
BWR stability analysis with the BNL Engineering Plant Analyzer
International Nuclear Information System (INIS)
Wulff, W.; Cheng, H.S.; Mallen, A.N.; Rohatgi, U.S.
1992-10-01
March 9, 1989 instability at the LaSalle-2 Power Plant and more than ninety related BWR transients have been simulated on the BNL Engineering Plant Analyzer (EPA). Power peaks were found to be potentially seventeen times greater than the rated power, flow reversal occurs momentarily during large power oscillations, the fuel centerline temperature oscillates between 1,030 and 2,090 K, while the cladding temperature oscillates between 560 and 570 K. The Suppression Pool reaches its specified temperature limit either never or in as little as 4.3 minutes, depending on operator actions and transient scenario. Thermohydraulic oscillations occur at low core coolant flow (both Recirculation Pumps tripped), with sharp axial or redial fission power peaking and with partial loss of feedwater preheating while the feedwater is flow kept high to maintain coolant inventory in the vessel. Effects from BOP system were shown to influence reactor stability strongly through dosed-loop resonance feedback. High feedwater flow and low temperature destabilize the reactor. Low feedwater flow restabilizes the reactor, because of steam condensation and feedwater preheating in the downcomer, which reduces effectively the destabilizing core inlet subcooling. The EPA has been found to be capable of analyzing BWR stability '' shown to be effective for scoping calculations and for supporting accident management
State stability analysis for the fermionic projector in the continuum
International Nuclear Information System (INIS)
Hoch, Stefan Ludwig
2008-01-01
The principle of the fermionic projector in the continuum gives an indication that there might be a deeper reason why elementary particles only appear with a few definite masses. In this thesis the existence of approximately state-stable configurations is shown. In order to achieve that, we make use of a variational principle for the fermionic projector in the continuum which contains certain contributions supported on the light cone. In a certain sense, these extra terms contain the structure of the underlying discrete spacetime. Lorentz invariant distributions and their convolutions are studied. Some of these are well-defined because the convolution integrals have compactly supported integrands. Other convolutions can be regularized such that the property of being ill-defined only plays a role on the light cone. These results are used to analyze the variational principle and to give criteria for state stability, which can be numerically analyzed. Some plots are presented to allow a decision about state stability and to show how possible configurations could look like. (orig.)
Color Stability of New Esthetic Restorative Materials: A Spectrophotometric Analysis.
Poggio, Claudio; Vialba, Lodovico; Berardengo, Anna; Federico, Ricaldone; Colombo, Marco; Beltrami, Riccardo; Scribante, Andrea
2017-07-06
The aim of this in vitro study was to evaluate and compare the color stability of different esthetic restorative materials (one microfilled composite, one nanofilled composite, one nanoceramic composite, one microfilled hybrid composite, one microfilled hybrid composite, one nanohybrid Ormocer based composite and one supra-nano spherical hybrid composite) after exposure to different staining solutions (physiological saline, red wine, coffee). All materials were prepared and polymerized into silicon rings (2 mm × 6 mm × 8 mm) to obtain specimens identical in size. Thirty cylindrical specimens of each material were prepared. Specimens were immersed in staining solutions (physiological saline, coffee and red wine) over a 28-day test period. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. The Shapiro-Wilk test and ANOVA were applied to assess significant differences among restorative materials. A paired t -test was applied to test which CIE L*a*b* parameters significantly changed after immersion in staining solutions. All restorative materials showed significant color differences after immersion in coffee. Coffee caused a significant color change in all types of tested composite resins. Only Filtek Supreme XTE demonstrated a staining susceptibility to red wine; no other significant differences among the materials were demonstrated. Long-term exposure to some food dyes (coffee in particular) can significantly affect the color stability of modern esthetic restorative materials regardless of materials' different compositions.
Safety analysis and risk assessment handbook
International Nuclear Information System (INIS)
Peterson, V.L.; Colwell, R.G.; Dickey, R.L.
1997-01-01
This Safety Analysis and Risk Assessment Handbook (SARAH) provides guidance to the safety analyst at the Rocky Flats Environmental Technology Site (RFETS) in the preparation of safety analyses and risk assessments. Although the older guidance (the Rocky Flats Risk Assessment Guide) continues to be used for updating the Final Safety Analysis Reports developed in the mid-1980s, this new guidance is used with all new authorization basis documents. With the mission change at RFETS came the need to establish new authorization basis documents for its facilities, whose functions had changed. The methodology and databases for performing the evaluations that support the new authorization basis documents had to be standardized, to avoid the use of different approaches and/or databases for similar accidents in different facilities. This handbook presents this new standardized approach. The handbook begins with a discussion of the requirements of the different types of authorization basis documents and how to choose the one appropriate for the facility to be evaluated. It then walks the analyst through the process of identifying all the potential hazards in the facility, classifying them, and choosing the ones that need to be analyzed further. It then discusses the methods for evaluating accident initiation and progression and covers the basic steps in a safety analysis, including consequence and frequency binning and risk ranking. The handbook lays out standardized approaches for determining the source terms of the various accidents (including airborne release fractions, leakpath factors, etc.), the atmospheric dispersion factors appropriate for Rocky Flats, and the methods for radiological and chemical consequence assessments. The radiological assessments use a radiological open-quotes templateclose quotes, a spreadsheet that incorporates the standard values of parameters, whereas the chemical assessments use the standard codes ARCHIE and ALOHA
Directory of Open Access Journals (Sweden)
Xiaoguang Deng
2015-01-01
Full Text Available Based on the nonlinear stability analysis method, the 3D nonlinear finite element model of a composite girder cable-stayed bridge with three pylons is established to research the effect of factors including geometric nonlinearity, material nonlinearity, static wind load, and unbalanced construction load on the structural stability during construction. Besides, the structural nonlinear stability in different construction schemes and the determination of temporary pier position are also studied. The nonlinear stability safety factors are calculated to demonstrate the rationality and safety of construction schemes. The results show that the nonlinear stability safety factors of this bridge during construction meet the design requirement and the minimum value occurs in the maximum double cantilever stage. Besides, the nonlinear stability of the structure in the side of edge-pylon meets the design requirement in the two construction schemes. Furthermore, the temporary pier can improve the structure stability, effectively, and the actual position is reasonable. In addition, the local buckling of steel girder occurs earlier than overall instability under load in some cable tension stages. Finally, static wind load and the unbalanced construction load should be considered in the stability analysis for the adverse impact.
Conceptual issues with risk analysis in Switzerland
Nicolet, Pierrick; Jaboyedoff, Michel; Lévy, Sébastien
2015-04-01
Risk analysis is a tricky procedure, where one can easily make mistakes. Indeed, although risk equations are rather general, transferring a methodology to another context or hazard type can often lead to inaccuracies or even significant errors. To illustrate this, common mistakes made with the Swiss methodology are presented, together with possible solutions. This includes the following: Risk analysis for moving objects only takes the process dimension into account (e.g. the length of a road section potentially affected by a landslide), but not the object dimension (e.g. the cars length). This is a fair simplification as long as the object dimension is considerably smaller than the process dimension. However, when the object is large compared to the process (e.g. rockfalls on a train), the results will be wrong. This problem can be illustrated by considering two blocs. According to this methodology a 1 m diameter bloc will be twice more susceptible to reach a train than a 50 cm bloc. This is obviously not correct. When it comes to rockfalls risk analysis on roads or railway found in the literature, the bloc dimension is usually neglected, in favour of the object dimension, which is a fair assumption in this context. However, it is possible to include both dimensions by using the sum of the lengths instead of one of them. Risk analysis is usually performed using 3 different scenarios, for 3 different ranges of return periods, namely 1-30, 30-100 and 100-300 years. In order to be conservative, the operator commonly considers the magnitude of the worst event that happens with a return period included between the class bounds, which means that the operator evaluates the magnitude reached or overpassed with a return period of 30, 100 and 300 years respectively. Then, since the magnitude corresponds to the upper bounds of the classes, risk is calculated using the frequency corresponding to these return periods and not to the middle of the class (and also subtracting the
14 CFR 417.225 - Debris risk analysis.
2010-01-01
... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Debris risk analysis. 417.225 Section 417... OF TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.225 Debris risk analysis. A flight safety analysis must demonstrate that the risk to the public potentially exposed to inert and...
Radiation risks: critical analysis and commentary.
Barrett, Bruce; Stiles, Melissa; Patterson, Jeff
2012-01-01
1) To review and summarize what is known about the health risks of radiation. 2) To compare risks from medical imaging to background radiation and to exposure from nuclear accidents. Literature review and summative critical analysis. Over the past several years, physicians and patients have become increasingly aware of the potential risks of radiation exposure from medical imaging. The Fukushima disaster further heightened public awareness of hazards associated with radiation and radioactivity. In the case of medical imaging, small but real risks of cancer and other radiation-induced disease must be balanced against potential benefits of improved diagnostic accuracy. The ethical principle of autonomy tells us that patients should be informed of potential benefits and harms of radiation imaging, and should participate in shared decision making. In the case of nuclear power, benefits and especially harms are exceptionally difficult to estimate accurately. Nevertheless, we know that hazards from today's nuclear power plants will persist for many years, affecting future generations not benefiting from electrical power generated today. A deeper and more widespread understanding of potential benefits and harms of personal and societal choices relating to radiation exposure may lead to improved medical and societal decision-making. Copyright © 2012 Elsevier Inc. All rights reserved.
Analysis of Operational Risks in Shipbuilding Industry
Directory of Open Access Journals (Sweden)
Daniela MATEI
2012-11-01
Full Text Available Our paper emphasizes the opportunities provided both for the academic research and companies by using a proposed model of analyzing the operational risks within business in general and shipbuilding industry in particular. The model aims to display the loss distribution from the operational risk for each business line/ type of event, based on frequency and severity estimation of the events. These estimations are derived mainly from the history logs of internal loss events. The calculations extend over a certain period of time in the future with a certain level of confidence. It should also be mentioned that the proposed model estimates unexpected losses, without making any suppositions concerning the values of the expected and unexpected losses. Several ideas could be extracted by analyzing and synthesizing the theoretical models from available literature. These ideas were analyzed in order to develop a model for operational risk analysis that is adapted to shipbuilding. This paper describes a new model, which can be applied to the naval industry to quantify operational risks.
Analysis of cavern stability at the Bryan Mound SPR site.
Energy Technology Data Exchange (ETDEWEB)
Ehgartner, Brian L.; Sobolik, Steven Ronald
2009-04-01
This report presents computational analyses that simulate the structural response of caverns at the Strategic Petroleum Reserve Bryan Mound site. The cavern field comprises 20 caverns. Five caverns (1, 2, 4, and 5; 3 was later plugged and abandoned) were acquired from industry and have unusual shapes and a history dating back to 1946. The other 16 caverns (101-116) were leached according to SPR standards in the mid-1980s and have tall cylindrical shapes. The history of the caverns and their shapes are simulated in a 3-D geomechanics model of the site that predicts deformations, strains, and stresses. Future leaching scenarios due to oil drawdowns using fresh water are also simulated by increasing the volume of the caverns. Cavern pressures are varied in the model to capture operational practices in the field. The results of the finite element model are interpreted to provide information on the current and future status of subsidence, well integrity, and cavern stability. The most significant result in this report is relevant to caverns 1, 2, and 5. The caverns have non-cylindrical shapes and have potential regions where the surrounding salt may be damaged during workover procedures. During a workover the normal cavern operating pressure is lowered to service a well. At this point the wellhead pressures are atmospheric. When the workover is complete, the cavern is repressurized. The resulting elastic stresses are sufficient to cause tension and large deviatoric stresses at several locations. With time, these stresses relax to a compressive state due to salt creep. However, the potential for salt damage and fracturing exists. The analyses predict tensile stresses at locations with sharp-edges in the wall geometry, or in the case of cavern 5, in the neck region between the upper and lower lobes of the cavern. The effects do not appear to be large-scale, however, so the only major impact is the potential for stress-induced salt falls in cavern 5, potentially leading to
Approach to uncertainty in risk analysis
Energy Technology Data Exchange (ETDEWEB)
Rish, W.R.
1988-08-01
In the Fall of 1985 EPA's Office of Radiation Programs (ORP) initiated a project to develop a formal approach to dealing with uncertainties encountered when estimating and evaluating risks to human health and the environment. Based on a literature review of modeling uncertainty, interviews with ORP technical and management staff, and input from experts on uncertainty analysis, a comprehensive approach was developed. This approach recognizes by design the constraints on budget, time, manpower, expertise, and availability of information often encountered in ''real world'' modeling. It is based on the observation that in practice risk modeling is usually done to support a decision process. As such, the approach focuses on how to frame a given risk modeling problem, how to use that framing to select an appropriate mixture of uncertainty analyses techniques, and how to integrate the techniques into an uncertainty assessment that effectively communicates important information and insight to decision-makers. The approach is presented in this report. Practical guidance on characterizing and analyzing uncertainties about model form and quantities and on effectively communicating uncertainty analysis results is included. Examples from actual applications are presented.
Zelic, Gregory; Varoqui, Deborah; Kim, Jeesun; Davis, Chris
2018-02-01
Patterns of coordination result from the interaction between (at least) two oscillatory components. This interaction is typically understood by means of two variables: the mode that expresses the shape of the interaction, and the stability that is the robustness of the interaction in this mode. A potent method of investigating coordinated behaviors is to examine the extent to which patterns of coordination arise spontaneously. However, a prominent issue faced by researchers is that, to date, no standard methods exist to fairly assess the stability of spontaneous coordination. In the present study, we introduce a new method called the index-of-stability (IS) analysis. We developed this method from the phase-coupling (PC) analysis that has been traditionally used for examining locomotion-respiration coordinated systems. We compared the extents to which both methods estimate the stability of simulated coordinated behaviors. Computer-generated time series were used to simulate the coordination of two rhythmic components according to a selected mode m:n and a selected degree of stability. The IS analysis was superior to the PC analysis in estimating the stability of spontaneous coordinated behaviors, in three ways: First, the estimation of stability itself was found to be more accurate and more reliable with the IS analysis. Second, the IS analysis is not constrained by the limitations of the PC analysis. Third and last, the IS analysis offers more flexibility, and so can be adapted according to the user's needs.
Stability analysis and support study on surroundings of finishing cut
Energy Technology Data Exchange (ETDEWEB)
Xu, J.; Miao, X.; Lu, A.; Xing, C. [CUMT, Jiangsu (China). College of Mineral and Energy Resources
2003-09-01
By means of finishing cut the trackless rubber-tried vehicle can directly go to the working face to remove the equipment. It can promote the efficiency in removing the equipment. Because of the finishing cut continuously affected by the dynamic pressure of face, it is important to find the reasonable position of the finishing cut and the proportion support. Based on the study of the ground pressure and the moving law of overlying strata during the terminal mining in sublevel caving face, the optimal position and the proportion support way of finishing cut were obtained using experiment with analog simulation and numerical simulation. This method can keep the stability for the surroundings of the finishing cut and lay the foundation for finishing the face quickly and safely. The engineering practice shows this technique is efficient and the significant social and economy benefit is obtained. 7 refs.,11 figs.
Resolving the 'time lag' debate in dam stability analysis
International Nuclear Information System (INIS)
Grenoble, B.A.; Harris, C.W.; Morris, D.I.
1993-01-01
The significance of delays in uplift pressure increases during floods is a subject of ongoing debate among dam owners and regulators. Current regulatory standards do not recognize these delays, known as time lag. One recent study concludes that the regulatory approach, indeed, is reasonable. In the complete study, Stone ampersand Webster researchers evaluated uplift pressures from 17 large concrete gravity dams. Data from eight of the dams were used to study time lag. Uplift was measured as frequently as every 15 minutes at one dam, two times per day at another dam during a flood, and three times per week at six other dams. The study showed that, although there is always a small time lag, the duration of the time lag is generally not sufficient to justify reducing the uplift pressures used in stability calculations
Snoring: Linear Stability Analysis and In-Vitroexperiments
Aurégan, Y.; Depollier, C.
1995-11-01
A theoretical and experimental study is presented of the aeroelastic instability of the human soft palate, which can explain the occurrence of snoring. The soft palate is modelled by a beam clamped at its leading edge and free at its trailing edge. The continuous and discrete cases are investigated. Only the two first modes of vibration of the soft palate are taken into account. The flow is incompressible, inviscid and one dimensional. Structural damping and flow nonstationarities can be considered. Theory shows that the soft palate loses its stability by flutter and that this instability is mainly controlled by a single dimensionless parameter which can be easily interpreted from a medical point of view. An experimental apparatus which produces sounds very close to human snoring is described. Agreement between theory and experiments is good.
Univariate and Bivariate Empirical Mode Decomposition for Postural Stability Analysis
Directory of Open Access Journals (Sweden)
Jacques Duchêne
2008-05-01
Full Text Available The aim of this paper was to compare empirical mode decomposition (EMD and two new extended methods of Ã¢Â€Â‰EMD named complex empirical mode decomposition (complex-EMD and bivariate empirical mode decomposition (bivariate-EMD. All methods were used to analyze stabilogram center of pressure (COP time series. The two new methods are suitable to be applied to complex time series to extract complex intrinsic mode functions (IMFs before the Hilbert transform is subsequently applied on the IMFs. The trace of the analytic IMF in the complex plane has a circular form, with each IMF having its own rotation frequency. The area of the circle and the average rotation frequency of IMFs represent efficient indicators of the postural stability status of subjects. Experimental results show the effectiveness of these indicators to identify differences in standing posture between groups.
Risk analysis: assessing uncertainties beyond expected values and probabilities
National Research Council Canada - National Science Library
Aven, T. (Terje)
2008-01-01
... . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Selectionofanalysismethod ... 3.2.1 Checklist-basedapproach... 3.2.2 Risk-basedapproach ... 29 29 34 35 36 4 The risk analysis process: risk a...
Alagoz, Baris Baykant
2017-09-01
With power mapping (conformal mapping), stability analyses of fractional order linear time invariant (LTI) systems are carried out by consideration of the root locus of expanded degree integer order polynomials in the principal Riemann sheet. However, it is essential to show the left half plane (LHP) stability analysis of fractional order characteristic polynomials in the s plane in order to close the gap emerging in stability analyses of fractional order and integer order systems. In this study, after briefly discussing the relation between the characteristic root orientations and the system stability, the author presents a methodology to establish principal characteristic polynomials to perform the LHP stability analysis of fractional order systems. The principal characteristic polynomials are formed by factorizing principal characteristic roots. Then, the LHP stability analysis of fractional order systems can be carried out by using the root equivalency of fractional order principal characteristic polynomials. Illustrative examples are presented to explain how to find equivalent roots of fractional order principal characteristic polynomials in order to carry out the LHP stability analyses of fractional order nominal and interval systems. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Methodologies for risk analysis in slope instability
International Nuclear Information System (INIS)
Bernabeu Garcia, M.; Diaz Torres, J. A.
2014-01-01
This paper is an approach to the different methodologies used in conducting landslide risk maps so that the reader can get a basic knowledge about how to proceed in its development. The landslide hazard maps are increasingly demanded by governments. This is because due to climate change, deforestation and the pressure exerted by the growth of urban centers, damage caused by natural phenomena is increasing each year, making this area of work a field of study with increasing importance. To explain the process of mapping a journey through each of the phases of which it is composed is made: from the study of the types of slope movements and the necessary management of geographic information systems (GIS) inventories and landslide susceptibility analysis, threat, vulnerability and risk. (Author)
Nuclear risk analysis of the Ulysses mission
International Nuclear Information System (INIS)
Bartram, B.W.; Vaughan, F.R.; Englehart, D.R.W.
1991-01-01
The use of a radioisotope thermoelectric generator fueled with plutonium-238 dioxide on the Space Shuttle-launched Ulysses mission implies some level of risk due to potential accidents. This paper describes the method used to quantify risks in the Ulysses mission Final Safety Analysis Report prepared for the U.S. Department of Energy. The starting point for the analysis described herein is following input of source term probability distributions from the General Electric Company. A Monte Carlo technique is used to develop probability distributions of radiological consequences for a range of accident scenarios thoughout the mission. Factors affecting radiological consequences are identified, the probability distribution of the effect of each factor determined, and the functional relationship among all the factors established. The probability distributions of all the factor effects are then combined using a Monte Carlo technique. The results of the analysis are presented in terms of complementary cumulative distribution functions (CCDF) by mission sub-phase, phase, and the overall mission. The CCDFs show the total probability that consequences (calculated health effects) would be equal to or greater than a given value
Stability analysis of a simplified model of supercritical water-cooled system
International Nuclear Information System (INIS)
Xue Aijun; Cheng Xu
2009-01-01
This paper presents the stability analysis of a simplified model of supercritical water-cooled system. Based on the perturbation linearization and Laplace transformation, transfer function of the simplified system model is established. A stability map is generated using both dimensionless parameters, i.e. sub-pseudo-critical number and trans-pseudo-critical number. An unstable region nearby the pseudo-critical point is determined. The effect of some important parameters on the stability behavior is investigated. It is found that the system is stabilized with a higher hydraulic resistance of the inlet, fluid inlet velocity. It is also found that a longer heating zone or a bigger acceleration of gravity leads to a larger stability margin of the system. (authors)
Model risk analysis for risk management and option pricing
Kerkhof, F.L.J.
2003-01-01
Due to the growing complexity of products in financial markets, market participants rely more and more on quantitative models for trading and risk management decisions. This introduces a fairly new type of risk, namely, model risk. In the first part of this thesis we investigate the quantitative
A tutorial on incremental stability analysis using contraction theory
DEFF Research Database (Denmark)
Jouffroy, Jerome; Fossen, Thor I.
2010-01-01
analysis, the plant and the controller in the case of tracking controller analysis), the denition of an abstract system common to the two systems and denoted as the \\virtual system", and the convergence study of the virtual system using its virtual dynamics representation. The approach is illustrated...
Analysis of cavern stability at the West Hackberry SPR site.
Energy Technology Data Exchange (ETDEWEB)
Ehgartner, Brian L.; Sobolik, Steven Ronald
2009-05-01
This report presents computational analyses that simulate the structural response of caverns at the Strategic Petroleum Reserve (SPR) West Hackberry site. The cavern field comprises 22 caverns. Five caverns (6, 7, 8, 9, 11) were acquired from industry and have unusual shapes and a history dating back to 1946. The other 17 caverns (101-117) were leached according to SPR standards in the mid-1980s and have tall cylindrical shapes. The history of the caverns and their shapes are simulated in a three-dimensional geomechanics model of the site that predicts deformations, strains, and stresses. Future leaching scenarios corresponding to oil drawdowns using fresh water are also simulated by increasing the volume of the caverns. Cavern pressures are varied in the model to capture operational practices in the field. The results of the finite element model are interpreted to provide information on the current and future status of subsidence, well integrity, and cavern stability. The most significant results in this report are relevant to Cavern 6. The cavern is shaped like a bowl with a large ceiling span and is in close proximity to Cavern 9. The analyses predict tensile stresses at the edge of the ceiling during repressuization of Cavern 6 following workover conditions. During a workover the cavern is at low pressure to service a well. The wellhead pressures are atmospheric. When the workover is complete, the cavern is repressurized. The resulting elastic stresses are sufficient to cause tension around the edge of the large ceiling span. With time, these stresses relax to a compressive state because of salt creep. However, the potential for salt fracture and propagation exists, particularly towards Cavern 9. With only 200 ft of salt between the caverns, the operational consequences must be examined if the two caverns become connected. A critical time may be during a workover of Cavern 9 in part because of the operational vulnerabilities, but also because dilatant damage is
Floquet stability analysis of the longitudinal dynamics of two hovering model insects
Wu, Jiang Hao; Sun, Mao
2012-01-01
Because of the periodically varying aerodynamic and inertial forces of the flapping wings, a hovering or constant-speed flying insect is a cyclically forcing system, and, generally, the flight is not in a fixed-point equilibrium, but in a cyclic-motion equilibrium. Current stability theory of insect flight is based on the averaged model and treats the flight as a fixed-point equilibrium. In the present study, we treated the flight as a cyclic-motion equilibrium and used the Floquet theory to analyse the longitudinal stability of insect flight. Two hovering model insects were considered—a dronefly and a hawkmoth. The former had relatively high wingbeat frequency and small wing-mass to body-mass ratio, and hence very small amplitude of body oscillation; while the latter had relatively low wingbeat frequency and large wing-mass to body-mass ratio, and hence relatively large amplitude of body oscillation. For comparison, analysis using the averaged-model theory (fixed-point stability analysis) was also made. Results of both the cyclic-motion stability analysis and the fixed-point stability analysis were tested by numerical simulation using complete equations of motion coupled with the Navier–Stokes equations. The Floquet theory (cyclic-motion stability analysis) agreed well with the simulation for both the model dronefly and the model hawkmoth; but the averaged-model theory gave good results only for the dronefly. Thus, for an insect with relatively large body oscillation at wingbeat frequency, cyclic-motion stability analysis is required, and for their control analysis, the existing well-developed control theories for systems of fixed-point equilibrium are no longer applicable and new methods that take the cyclic variation of the flight dynamics into account are needed. PMID:22491980
International Nuclear Information System (INIS)
Merdan, H.; Duman, O.
2009-01-01
This paper presents the stability analysis of equilibrium points of a general discrete-time population dynamics involving predation with and without Allee effects which occur at low population density. The mathematical analysis and numerical simulations show that the Allee effect has a stabilizing role on the local stability of the positive equilibrium points of this model.
Investigations of blood ammonia analysis: Test matrices, storage, and stability.
Goldstein, Brittany N; Wesler, Jordan; Nowacki, Amy S; Reineks, Edmunds; Natowicz, Marvin R
2017-06-01
An assessment of blood ammonia concentration is common medical practice in the evaluation of an individual with an unexplained mental status change or coma. The determination of a blood ammonia level is most commonly done using a glutamate dehydrogenase (GLDH)-based assay, although there are many potential sources of artifact and the literature is inconsistent regarding key preanalytic issues. Using a GLDH-based assay, we first investigated matrix effects using three anticoagulants: heparin, EDTA and oxalate. Heparin-anticoagulated plasma was substantially less precise than EDTA- and oxalate-anticoagulated plasma. Oxalate-anticoagulated plasma showed a greater baseline of apparent ammonia than either heparin- or EDTA-derived plasma, presumably due to interferants. We then evaluated the stability of EDTA-anticoagulated plasma for assessment of ammonia when stored at 4°C,-14°C or -70°C. There was a linear increase of ammonia with storage at both 4°C and -14°C. Plasma kept at -70°C for up to three weeks showed no change in measured ammonia relative to the baseline determination. This work clarifies preanalytic conditions for which a precise determination of ammonia can be accomplished using a GLDH-based assay. Copyright © 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.
Stability analysis of multiple-robot control systems
Wen, John T.; Kreutz, Kenneth
1989-01-01
In a space telerobotic service scenario, cooperative motion and force control of multiple robot arms are of fundamental importance. Three paradigms to study this problem are proposed. They are distinguished by the set of variables used for control design. They are joint torques, arm tip force vectors, and an accelerated generalized coordinate set. Control issues related to each case are discussed. The latter two choices require complete model information, which presents practical modeling, computational, and robustness problems. Therefore, focus is on the joint torque control case to develop relatively model independent motion and internal force control laws. The rigid body assumption allows the motion and force control problems to be independently addressed. By using an energy motivated Lyapunov function, a simple proportional derivative plus gravity compensation type of motion control law is always shown to be stabilizing. The asymptotic convergence of the tracing error to zero requires the use of a generalized coordinate with the contact constraints taken into account. If a non-generalized coordinate is used, only convergence to a steady state manifold can be concluded. For the force control, both feedforward and feedback schemes are analyzed. The feedback control, if proper care has been taken, exhibits better robustness and transient performance.
Heat transfer modelling and stability analysis of selective laser melting
International Nuclear Information System (INIS)
Gusarov, A.V.; Yadroitsev, I.; Bertrand, Ph.; Smurov, I.
2007-01-01
The process of direct manufacturing by selective laser melting basically consists of laser beam scanning over a thin powder layer deposited on a dense substrate. Complete remelting of the powder in the scanned zone and its good adhesion to the substrate ensure obtaining functional parts with improved mechanical properties. Experiments with single-line scanning indicate, that an interval of scanning velocities exists where the remelted tracks are uniform. The tracks become broken if the scanning velocity is outside this interval. This is extremely undesirable and referred to as the 'balling' effect. A numerical model of coupled radiation and heat transfer is proposed to analyse the observed instability. The 'balling' effect at high scanning velocities (above ∼20 cm/s for the present conditions) can be explained by the Plateau-Rayleigh capillary instability of the melt pool. Two factors stabilize the process with decreasing the scanning velocity: reducing the length-to-width ratio of the melt pool and increasing the width of its contact with the substrate
Roos, Paulien E; Dingwell, Jonathan B
2013-06-21
Older adults and those with increased fall risk tend to walk slower. They may do this voluntarily to reduce their fall risk. However, both slower and faster walking speeds can predict increased risk of different types of falls. The mechanisms that contribute to fall risk across speeds are not well known. Faster walking requires greater forward propulsion, generated by larger muscle forces. However, greater muscle activation induces increased signal-dependent neuromuscular noise. These speed-related increases in neuromuscular noise may contribute to the increased fall risk observed at faster walking speeds. Using a 3D dynamic walking model, we systematically varied walking speed without and with physiologically-appropriate neuromuscular noise. We quantified how actual fall risk changed with gait speed, how neuromuscular noise affected speed-related changes in fall risk, and how well orbital and local dynamic stability measures predicted changes in fall risk across speeds. When we included physiologically-appropriate noise to the 'push-off' force in our model, fall risk increased with increasing walking speed. Changes in kinematic variability, orbital, and local dynamic stability did not predict these speed-related changes in fall risk. Thus, the increased neuromuscular variability that results from increased signal-dependent noise that is necessitated by the greater muscular force requirements of faster walking may contribute to the increased fall risk observed at faster walking speeds. The lower fall risk observed at slower speeds supports experimental evidence that slowing down can be an effective strategy to reduce fall risk. This may help explain the slower walking speeds observed in older adults and others. Copyright © 2013 Elsevier Ltd. All rights reserved.
Risk analysis methodology designed for small and medium enterprises
Ladislav Beránek; Radim Remeš
2009-01-01
The aim of this paper is to present risk analysis procedures successfully applied by several Czech small and medium enterprises. The paper presents in detail the individual steps we use in risk analysis of small and medium enterprises in the Czech Republic. Suggested method to risk analysis is based on the modification of the FRAP methodology and the BITS recommendation. Modifications of both methodologies are described in detail. We propose modified risk analysis methodology which is quick a...
Linear stability analysis of a nuclear reactor using the lumped model
Directory of Open Access Journals (Sweden)
Kale Vivek A.
2016-01-01
Full Text Available The stability analysis of a nuclear reactor is an important aspect in the design and operation of the reactor. A stable neutronic response to perturbations is essential from the safety point of view. In this paper, a general methodology has been developed for the linear stability analysis of nuclear reactors using the lumped reactor model. The reactor kinetics has been modelled using the point kinetics equations and the reactivity feedbacks from fuel, coolant and xenon have been modelled through the appropriate time dependent equations. These governing equations are linearized considering small perturbations in the reactor state around a steady operating point. The characteristic equation of the system is used to establish the stability zone of the reactor considering the reactivity coefficients as parameters. This methodology has been used to identify the stability region of a typical pressurized heavy water reactor. It is shown that the positive reactivity feedback from xenon narrows down the stability region. Further, it is observed that the neutron kinetics parameters (such as the number of delayed neutron precursor groups considered, the neutron generation time, the delayed neutron fractions, etc. do not have a significant influence on the location of the stability boundary. The stability boundary is largely influenced by the parameters governing the evolution of the fuel and coolant temperature and xenon concentration.
Flexible Launch Vehicle Stability Analysis Using Steady and Unsteady Computational Fluid Dynamics
Bartels, Robert E.
2012-01-01
Launch vehicles frequently experience a reduced stability margin through the transonic Mach number range. This reduced stability margin can be caused by the aerodynamic undamping one of the lower-frequency flexible or rigid body modes. Analysis of the behavior of a flexible vehicle is routinely performed with quasi-steady aerodynamic line loads derived from steady rigid aerodynamics. However, a quasi-steady aeroelastic stability analysis can be unconservative at the critical Mach numbers, where experiment or unsteady computational aeroelastic analysis show a reduced or even negative aerodynamic damping.Amethod of enhancing the quasi-steady aeroelastic stability analysis of a launch vehicle with unsteady aerodynamics is developed that uses unsteady computational fluid dynamics to compute the response of selected lower-frequency modes. The response is contained in a time history of the vehicle line loads. A proper orthogonal decomposition of the unsteady aerodynamic line-load response is used to reduce the scale of data volume and system identification is used to derive the aerodynamic stiffness, damping, and mass matrices. The results are compared with the damping and frequency computed from unsteady computational aeroelasticity and from a quasi-steady analysis. The results show that incorporating unsteady aerodynamics in this way brings the enhanced quasi-steady aeroelastic stability analysis into close agreement with the unsteady computational aeroelastic results.
Risk Analysis Approach to Rainwater Harvesting Systems
Directory of Open Access Journals (Sweden)
Nadia Ursino
2016-08-01
Full Text Available Urban rainwater reuse preserves water resources and promotes sustainable development in rapidly growing urban areas. The efficiency of a large number of urban water reuse systems, operating under different climate and demand conditions, is evaluated here on the base of a new risk analysis approach. Results obtained by probability analysis (PA indicate that maximum efficiency in low demanding scenarios is above 0.5 and a threshold, distinguishing low from high demanding scenarios, indicates that in low demanding scenarios no significant improvement in performance may be attained by increasing the storage capacity of rainwater harvesting tanks. Threshold behaviour is displayed when tank storage capacity is designed to match both the average collected volume and the average reuse volume. The low demand limit cannot be achieved under climate and operating conditions characterized by a disproportion between harvesting and demand volume.
Cortes, Nelson; Porter, Larissa D; Ambegaonkar, Jatin P; Caswell, Shane V
2014-12-01
Dancers have a lower incidence of anterior cruciate ligament (ACL) injury compared to athletes in sports that involve cutting and landing motions. Balance can impact ACL injury risk and is related to neuromuscular control during movement. The purpose of this study was to investigate whether balance differences exist among female dancers and female soccer and basketball athletes. Fifty-eight female dancers, soccer, and basketball athletes (16.5 ± 1.6 yrs, 1.6 ± 0.2 m, 60.2 ± 14.1 kg) completed the Stability Evaluation Test (SET) on the NeuroCom VSR Sport (NeuroCom International, Clackamas, OR) to measure sway velocity. Video records of the SET test were used for Balance Error Scoring System (BESS) test scoring. A oneway ANCOVA compared composite sway velocity and BESS scores among sports. There was no statistically significant difference for sway velocity or BESS among sports (sway velocity soccer 2.3 ± 0.4, dance 2.2 ± 0.4, and basketball 2.4 ± 0.4; BESS soccer 13.6 ± 5.0, dance 11.9 ± 5.5, and basketball 14.9 ± 5.1, p>0.05). Balance was similar among athletes participating in different sports (dance, basketball, and soccer). Quasi-static balance may not play a significant role in neuromuscular control during movement and not be a significant risk factor to explain the disparity in ACL injury incidence among sports. Future research should examine the effects of dynamic balance and limb asymmetries among sports to elucidate on the existing differences on ACL injury incidence rates.
Langford, Katherine H; Reid, Malcolm J; Fjeld, Eirik; Øxnevad, Sigurd; Thomas, Kevin V
2015-07-01
Eight organic UV filters and stabilizers were quantitatively determined in wastewater sludge and effluent, landfill leachate, sediments, and marine and freshwater biota. Crab, prawn and cod from Oslofjord, and perch, whitefish and burbot from Lake Mjøsa were selected in order to evaluate the potential for trophic accumulation. All of the cod livers analysed were contaminated with at least 1 UV filter, and a maximum concentration of almost 12 μg/g wet weight for octocrylene (OC) was measured in one individual. 80% of the cod livers contained OC, and approximately 50% of cod liver and prawn samples contained benzophenone (BP3). Lower concentrations and detection frequencies were observed in freshwater species and the data of most interest is the 4 individual whitefish that contained both BP3 and ethylhexylmethoxycinnamate (EHMC) with maximum concentrations of almost 200 ng/g wet weight. The data shows a difference in the loads of UV filters entering receiving water dependent on the extent of wastewater treatment. Primary screening alone is insufficient for the removal of selected UV filters (BP3, Padimate, EHMC, OC, UV-234, UV-327, UV-328, UV-329). Likely due in part to the hydrophobic nature of the majority of the UV filters studied, particulate loading and organic carbon content appear to be related to concentrations of UV filters in landfill leachate and an order of magnitude difference in these parameters correlates with an order of magnitude difference in the effluent concentrations of selected UV filters (Fig. 2). From the data, it is possible that under certain low flow conditions selected organic UV filters may pose a risk to surface waters but under the present conditions the risk is low, but some UV filters will potentially accumulate through the trophic food chain. Copyright © 2015. Published by Elsevier Ltd.
Transient Stability Analysis of Induction Generator Using Time Domain Torque Characteristic
Senjyu, Tomonobu; Sueyoshi, Norihide; Uezato, Katsumi; Fujita, Hideki; Funabashi, Toshihisa
Transient stability assessment of the wind power generator is one of main issue in power system security and operation. The transient stability of the wind power generator is determine by its corresponding Critical Clearing Time(CCT). In this paper, we present the formulae to the transient behavior analysis and the transient stability analysis technique of induction generator used in wind power generating system at the three-phase fault condition. In the proposed method, the transient stability of the induction generator is analyzed using well known torque-slip and generator speed-time characteristics. The validity of the developed technique is confirmed with the results obtained from trials and error method using MATLAB/SIMULINK.
Stability analysis of concrete gravity dam on complicated foundation with multiple slide planes
Directory of Open Access Journals (Sweden)
Ren Xuhua
2008-09-01
Full Text Available A key problem in gravity dam design is providing enough stability to prevent slide, and the difficulty increases if there are several weak structural planes in the dam foundation. Overload and material weakening were taken into account, and a finite difference strength reserve method with partial safety factors based on the reliability method was developed and used to study the anti-slide stability of a concrete gravity dam on a complicated foundation with multiple slide planes. Possible slide paths were obtained, and the stability of the foundation with possible failure planes was evaluated through analysis of the stress distribution characteristics. The results reveal the mechanism and process of sliding due to weak structural planes and their deformations, and provide a reference for anti-slide stability analysis of gravity dams in complicated geological conditions.
Langley Stability and Transition Analysis Code (LASTRAC) Version 1.2 User Manual
Chang, Chau-Lyan
2004-01-01
LASTRAC is a general-purposed, physics-based transition prediction code released by NASA for Laminar Flow Control studies and transition research. The design and development of the LASTRAC code is aimed at providing an engineering tool that is easy to use and yet capable of dealing with a broad range of transition related issues. It was written from scratch based on the state-of-the-art numerical methods for stability analysis and modern software technologies. At low fidelity, it allows users to perform linear stability analysis and N-factor transition correlation for a broad range of flow regimes and configurations by using either the linear stability theory or linear parabolized stability equations method. At high fidelity, users may use nonlinear PSE to track finite-amplitude disturbances until the skin friction rise. This document describes the governing equations, numerical methods, code development, detailed description of input/output parameters, and case studies for the current release of LASTRAC.
EHPS Handling Stability Analysis of Electric Bus Based on System Identification Method
Zhang, Ni; Liu, Hai-mei; Bei, Shao-yi; Li, Bo; Zhao, Jing-bo
2017-09-01
Electric hydraulic assist force steering system (EHPS system) is the steering system of electric bus, this paper presents a method of EHPS handling stability analysis based on system identification method according to the handling stability of EHPS system for electric bus. The simulation model of electro-hydraulic assist force steering system EHPS is established by using the software AMESim, and making a quantitative analysis on the characteristics of the electric assist force assisted steering system, the assist force response and stability. At the same time, we study the stability of vehicle, including hunting, transient response, return experiment, the results show that the HPS and EHPS by comparing the simulation: It improves the portability, road sense, transient response and return performance after loading the system, which verifiy the effectiveness of the control strategy that improves vehicle steering performance, and it provides the basis for the optimization of control methods in the future.
Stability and bifurcation analysis of a generalized scalar delay differential equation.
Bhalekar, Sachin
2016-08-01
This paper deals with the stability and bifurcation analysis of a general form of equation D(α)x(t)=g(x(t),x(t-τ)) involving the derivative of order α ∈ (0, 1] and a constant delay τ ≥ 0. The stability of equilibrium points is presented in terms of the stability regions and critical surfaces. We provide a necessary condition to exist chaos in the system also. A wide range of delay differential equations involving a constant delay can be analyzed using the results proposed in this paper. The illustrative examples are provided to explain the theory.
Integral equation based stability analysis of short wavelength drift modes in tokamaks
International Nuclear Information System (INIS)
Hirose, A.; Elia, M.
2003-01-01
Linear stability of electron skin-size drift modes in collisionless tokamak discharges has been investigated in terms of electromagnetic, kinetic integral equations in which neither ions nor electrons are assumed to be adiabatic. A slab-like ion temperature gradient mode persists in such a short wavelength regime. However, toroidicity has a strong stabilizing influence on this mode. In the electron branch, the toroidicity induced skin-size drift mode previously predicted in terms of local kinetic analysis has been recovered. The mode is driven by positive magnetic shear and strongly stabilized for negative shear. The corresponding mixing length anomalous thermal diffusivity exhibits favourable isotope dependence. (author)
Global asymptotic stability analysis for neutral stochastic neural networks with time-varying delays
Su, Weiwei; Chen, Yiming
2009-04-01
In this paper, the global asymptotic stability is investigated for a class of neutral stochastic neural networks with time-varying delays and norm-bounded uncertainties. Based on Lyapunov stability theory and stochastic analysis approaches, delay-dependent criteria are derived to ensure the global, robust, asymptotic stability of the addressed system in the mean square for all admissible parameter uncertainties. The criteria can be checked easily by the LMI Control Toolbox in Matlab. A numerical example is given to illustrate the feasibility and effectiveness of the results.
Detecting long-range correlation with detrended fluctuation analysis: Application to BWR stability
Energy Technology Data Exchange (ETDEWEB)
Espinosa-Paredes, Gilberto [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico, DF 09340 (Mexico)]. E-mail: gepe@xanum.uam.mx; Alvarez-Ramirez, Jose [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico, DF 09340 (Mexico); Vazquez, Alejandro [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico, DF 09340 (Mexico)
2006-11-15
The aim of this paper is to explore the application of detrended fluctuation analysis (DFA) to study boiling water reactor stability. DFA is a scaling method commonly used for detecting long-range correlations in non-stationary time series. This method is based on the random walk theory and was applied to neutronic power signal of Forsmark stability benchmark. Our results shows that the scaling properties breakdown during unstable oscillations.
Robust Stability Clearance of Flight Control Law Based on Global Sensitivity Analysis
Ou, Liuli; Liu, Lei; Dong, Shuai; Wang, Yongji
2014-01-01
To validate the robust stability of the flight control system of hypersonic flight vehicle, which suffers from a large number of parametrical uncertainties, a new clearance framework based on structural singular value ( $\\mu $ ) theory and global uncertainty sensitivity analysis (SA) is proposed. In this framework, SA serves as the preprocess of uncertain model to be analysed to help engineers to determine which uncertainties affect the stability of the closed loop system more slightly. By ig...
Small-angle stability analysis of a linear control system for a high power communication satellite
Omalley, T. A.
1972-01-01
A small angle stability analysis is presented for one particular configuration of a high power communication satellite having a linear control system. Both the central body and the solar array are treated as rigid bodies. The control system studied consists of three-axis control of the central body and one-axis control of the solar array rotation relative to the central body. The results yield preliminary indications of the relation of stability to satellite inertias and control gains.
Exponential stability analysis for delayed stochastic Cohen-Grossberg neural network
Directory of Open Access Journals (Sweden)
Guanjun Wang
2010-04-01
Full Text Available In this paper, the exponential stability problems are addressed for a class of delayed Cohen-Grossberg neural networks which are also perturbed by some stochastic noises. By employing the Lyapunov method, stochastic analysis and some inequality techniques, sufficient conditions are acquired for checking the pth(p g 1 and the 1st moment exponential stability of the network. Finally, One example is given to show the effectiveness of the proposed results.
ANALYSIS OF PERTURBED MOTION STABILITY OF WHEELER VEHICLES BRAKES CONTROL SYSTEM
Directory of Open Access Journals (Sweden)
V. Verbytskiyi
2011-01-01
Full Text Available The analysis of the perturbed motion stability of the brake automatic control system on the basis of Lyapunov’s second method is carried out. Using transformations of Lurie there has been ob-tained the canonical form of the system of equations of automatic control. It allowed determining the necessary and sufficient conditions of the asymptotic stability of the system irrespective of its initial condition and a definite choice of the admissible characteristic of the regulator.
Probabilistic methods in fire-risk analysis
International Nuclear Information System (INIS)
Brandyberry, M.D.
1989-01-01
The first part of this work outlines a method for assessing the frequency of ignition of a consumer product in a building and shows how the method would be used in an example scenario utilizing upholstered furniture as the product and radiant auxiliary heating devices (electric heaters, wood stoves) as the ignition source. Deterministic thermal models of the heat-transport processes are coupled with parameter uncertainty analysis of the models and with a probabilistic analysis of the events involved in a typical scenario. This leads to a distribution for the frequency of ignition for the product. In second part, fire-risk analysis as currently used in nuclear plants is outlines along with a discussion of the relevant uncertainties. The use of the computer code COMPBRN is discussed for use in the fire-growth analysis along with the use of response-surface methodology to quantify uncertainties in the code's use. Generalized response surfaces are developed for temperature versus time for a cable tray, as well as a surface for the hot gas layer temperature and depth for a room of arbitrary geometry within a typical nuclear power plant compartment. These surfaces are then used to simulate the cable tray damage time in a compartment fire experiment
Liu, Yong; Qin, Zhimeng; Hu, Baodan; Feng, Shuai
2018-04-01
Stability analysis is of great significance to landslide hazard prevention, especially the dynamic stability. However, many existing stability analysis methods are difficult to analyse the continuous landslide stability and its changing regularities in a uniform criterion due to the unique landslide geological conditions. Based on the relationship between displacement monitoring data, deformation states and landslide stability, a state fusion entropy method is herein proposed to derive landslide instability through a comprehensive multi-attribute entropy analysis of deformation states, which are defined by a proposed joint clustering method combining K-means and a cloud model. Taking Xintan landslide as the detailed case study, cumulative state fusion entropy presents an obvious increasing trend after the landslide entered accelerative deformation stage and historical maxima match highly with landslide macroscopic deformation behaviours in key time nodes. Reasonable results are also obtained in its application to several other landslides in the Three Gorges Reservoir in China. Combined with field survey, state fusion entropy may serve for assessing landslide stability and judging landslide evolutionary stages.
Pizzigalli, Luisa; Filippini, Alberto; Ahmaidi, Said; Jullien, Hugues; Rainoldi, Alberto
2011-02-01
Falls are one of the major health problems affecting the quality of life among older adults. The aging process is associated with decreasing muscle strength and an increasing risk of falling. The variables and techniques adopted to quantify muscular strength and postural stability were different in each protocol; a great number of reports analyzed the risk factors and predictors of falls, but the results appear still uncertain. To date, there is no clear, definitive statement or review that has examined the effect of the quadriceps strength on static balance performances in different sensory conditions. This contribution aims to provide an overview of experimental works to increase the comprehension and prevention of falls and fall-related injuries in the elderly. Based on a review of the literature, this work was designed to explore the relationship among risk of falls, postural stability, and muscular strength of lower limbs in older adults.
A more general model for the analysis of the rock slope stability
Indian Academy of Sciences (India)
Because of the numerous problems related to the rock slope stability the above assumption is satisﬁed and the shear strength characteristics of intact rock have taken part in the analysis. The analysis presented here gives a better concept, view, and idea of understanding the physical nature of rock slopes and includes ...
DEFF Research Database (Denmark)
Fuhrmann, David R.; Bingham, Harry B.; Madsen, Per A.
2004-01-01
This paper considers a method of lines stability analysis for finite difference discretizations of a recently published Boussinesq method for the study of highly nonlinear and extremely dispersive water waves. The analysis demonstrates the near-equivalence of classical linear Fourier (von Neumann...
Analysis of Thermal Stability of Different Counter on 28nm FPGA
DEFF Research Database (Denmark)
Gupta, Daizy; Yadav, Amit; Hussain, Dil muhammed Akbar
2016-01-01
In this paper we are presenting the power analysis for thermal awareness of different counters. The technique we are using to do the analysis is based on 28 nm FPGA tech-nique. In this work during implementation on FPGA, we are going to analyze thermal stability of different counters in temperature...
Integrated analysis software for bulk power system stability
Energy Technology Data Exchange (ETDEWEB)
Tanaka, T.; Nagao, T.; Takahashi, K. [Central Research Inst. of Electric Power Industry, Tokyo (Japan)
1994-12-31
This paper presents Central Research Inst.of Electric Power Industry - CRIEPI`s - own developed three softwares for bulk power network analysis and the user support system which arranges tremendous data necessary for these softwares with easy and high reliability. (author) 3 refs., 7 figs., 2 tabs.
ORIGINAL ARTICLE Stability Analysis of Delayed Cournot Model in ...
African Journals Online (AJOL)
HP
Elsadany, A.A. (2010).Dynamics of a delayed duopoly game with bounded rationality. Mathematical and computer modeling, 52(9-10), 1479-1489. Kopel, M. (1996). Simple and complex adjustment dynamics in court. Duopoly model. Chaos, Solitons and Fractal, 7(12), 2013-2048. Peters, E. (1994). Fractal Market Analysis:.
ANALYSIS OF THE TRANSIENT STABILITY LIMIT OF NIGERIA'S ...
African Journals Online (AJOL)
This choice is influenced by the fact that the Ikeja-West sub-network is the hub of power transmission arteries in Nigeria. Thus the Electrical Transient and Analysis Program (ETAP) software is deployed to operate on the ensuing model. This then leads to generating a series of results that demonstrates the different scenarios ...
Stress determination and geomechanical stability analysis of an oil ...
Indian Academy of Sciences (India)
Practical data including geomechanical parameters along with drilling data from one of Iranian oilfields, Mansouri-54 well have been utilized in this analysis. in situ stress was determined using stress polygon method and conducting hydraulic fracturing data in the field. Analytical solution using the Mogi–Coulomb and the ...
Structural analysis of pole assignment and stabilization in dynamic systems
Şefik, Ayla
1989-01-01
Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Sciences of Bilkent Univ. , 1989. Thesis (Ph.D.) -- Bilkent University, 1989. Includes bibliographical references leaves 127-132. Motivated by the need for qualitative investigation of general system properties such as controllability, obser\\^bility, existence of fixed modes, etc. as the complement of the quantitative approach in analysis, especially of large-scale systems,...
The Contribution of Particle Swarm Optimization to Three-Dimensional Slope Stability Analysis
Directory of Open Access Journals (Sweden)
Roohollah Kalatehjari
2014-01-01
Full Text Available Over the last few years, particle swarm optimization (PSO has been extensively applied in various geotechnical engineering including slope stability analysis. However, this contribution was limited to two-dimensional (2D slope stability analysis. This paper applied PSO in three-dimensional (3D slope stability problem to determine the critical slip surface (CSS of soil slopes. A detailed description of adopted PSO was presented to provide a good basis for more contribution of this technique to the field of 3D slope stability problems. A general rotating ellipsoid shape was introduced as the specific particle for 3D slope stability analysis. A detailed sensitivity analysis was designed and performed to find the optimum values of parameters of PSO. Example problems were used to evaluate the applicability of PSO in determining the CSS of 3D slopes. The first example presented a comparison between the results of PSO and PLAXI-3D finite element software and the second example compared the ability of PSO to determine the CSS of 3D slopes with other optimization methods from the literature. The results demonstrated the efficiency and effectiveness of PSO in determining the CSS of 3D soil slopes.
A stability analysis method for the fuzzy controller and its application
International Nuclear Information System (INIS)
Han, Suk Gyu
1994-02-01
A method is proposed to analyze the stability of a fuzzy controller and the method is applied to a fuzzy controller developed in this work to automatically control the steam generator water level in the pressurized water reactor (PWR). The stability analysis method is devised from the relationships between the fuzzy controller and the conventional PI (Proportional and Integral) controller. The relationships are derived from the theoretical analysis and modeling of the widely used fuzzy controller having two inputs (Error, Rate) and one output with triangular type membership functions. In addition, an analyzable 9-Rule fuzzy controller is designed and computer-simulated for the automatic control of the steam generator water level in the PWR to employ the developed stability analysis method. This study shows that the stability analysis method based on the comparison of the equivalent PI gain ranges of the fuzzy controller with that of a linear PI controller provides very meaningful ideas for the design of stable fuzzy controller through the computer simulations. Therefore, the method suggested in this work can be used in a confirmatory process to check the stability of a fuzzy controller designed with two inputs (error, rate) and also the method would be used as an useful guidance to efficiently design and tune the fuzzy controller
The Contribution of Particle Swarm Optimization to Three-Dimensional Slope Stability Analysis
A Rashid, Ahmad Safuan; Ali, Nazri
2014-01-01
Over the last few years, particle swarm optimization (PSO) has been extensively applied in various geotechnical engineering including slope stability analysis. However, this contribution was limited to two-dimensional (2D) slope stability analysis. This paper applied PSO in three-dimensional (3D) slope stability problem to determine the critical slip surface (CSS) of soil slopes. A detailed description of adopted PSO was presented to provide a good basis for more contribution of this technique to the field of 3D slope stability problems. A general rotating ellipsoid shape was introduced as the specific particle for 3D slope stability analysis. A detailed sensitivity analysis was designed and performed to find the optimum values of parameters of PSO. Example problems were used to evaluate the applicability of PSO in determining the CSS of 3D slopes. The first example presented a comparison between the results of PSO and PLAXI-3D finite element software and the second example compared the ability of PSO to determine the CSS of 3D slopes with other optimization methods from the literature. The results demonstrated the efficiency and effectiveness of PSO in determining the CSS of 3D soil slopes. PMID:24991652
Overcoming barriers to integrating economic analysis into risk assessment.
Hoffmann, Sandra
2011-09-01
Regulatory risk analysis is designed to provide decisionmakers with a clearer understanding of how policies are likely to affect risk. The systems that produce risk are biological, physical, and social and economic. As a result, risk analysis is an inherently interdisciplinary task. Yet in practice, risk analysis has been interdisciplinary in only limited ways. Risk analysis could provide more accurate assessments of risk if there were better integration of economics and other social sciences into risk assessment itself. This essay examines how discussions about risk analysis policy have influenced the roles of various disciplines in risk analysis. It explores ways in which integrated bio/physical-economic modeling could contribute to more accurate assessments of risk. It reviews examples of the kind of integrated economics-bio/physical modeling that could be used to enhance risk assessment. The essay ends with a discussion of institutional barriers to greater integration of economic modeling into risk assessment and provides suggestions on how these might be overcome. © 2011 Society for Risk Analysis.
Two-Year Trajectory of Fall Risk in People With Parkinson Disease: A Latent Class Analysis.
Paul, Serene S; Thackeray, Anne; Duncan, Ryan P; Cavanaugh, James T; Ellis, Theresa D; Earhart, Gammon M; Ford, Matthew P; Foreman, K Bo; Dibble, Leland E
2016-03-01
To examine fall risk trajectories occurring naturally in a sample of individuals with early to middle stage Parkinson disease (PD). Latent class analysis, specifically growth mixture modeling (GMM), of longitudinal fall risk trajectories. Assessments were conducted at 1 of 4 universities. Community-dwelling participants with PD of a longitudinal cohort study who attended at least 2 of 5 assessments over a 2-year follow-up period (N=230). Not applicable. Fall risk trajectory (low, medium, or high risk) and stability of fall risk trajectory (stable or fluctuating). Fall risk was determined at 6 monthly intervals using a simple clinical tool based on fall history, freezing of gait, and gait speed. The GMM optimally grouped participants into 3 fall risk trajectories that closely mirrored baseline fall risk status (P=.001). The high fall risk trajectory was most common (42.6%) and included participants with longer and more severe disease and with higher postural instability and gait disability (PIGD) scores than the low and medium fall risk trajectories (Pfall risk (posterior probability fall risk trajectories over 2 years. Further investigation is required to determine whether interventions to improve gait and balance may improve fall risk trajectories in people with PD. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
Analysis of stability boundaries of satellite's equilibrium attitude in a circular orbit
Novikov, M. A.
2016-03-01
An asymmetric satellite equipped with control momentum gyroscopes (CMGs) with the center of mass of the system moving uniformly in a circular orbit was considered. The stability of a relative equilibrium attitude of the satellite was analyzed using Lyapunov's direct method. The Lyapunov function V is a positive definite integral of the total energy of the perturbed motion of the system. The asymptotic stability analysis of the stationary motion of the conservative system was based on the Barbashin-Krasovskii theorem on the nonexistence of integer trajectories of the set dot V, which was obtained using the differential equations of motion of the satellite with CMGs. By analyzing the sign definiteness of the quadratic part of V, it was found earlier by V.V. Sazonov that the stability region is described by four strict inequalities. The asymptotic stability at the stability boundary was analyzed by sequentially turning these inequalities into equalities with terms of orders higher than the second taken into account in V. The sign definiteness analysis of the inhomogeneous function V at the stability boundary involved a huge amount of computations related to the multiplication, expansion, substitution, and factorization of symbolic expressions. The computations were performed by applying a computer algebra system on a personal computer.
An Emerging New Risk Analysis Science: Foundations and Implications.
Aven, Terje
2017-09-07
To solve real-life problems-such as those related to technology, health, security, or climate change-and make suitable decisions, risk is nearly always a main issue. Different types of sciences are often supporting the work, for example, statistics, natural sciences, and social sciences. Risk analysis approaches and methods are also commonly used, but risk analysis is not broadly accepted as a science in itself. A key problem is the lack of explanatory power and large uncertainties when assessing risk. This article presents an emerging new risk analysis science based on novel ideas and theories on risk analysis developed in recent years by the risk analysis community. It builds on a fundamental change in thinking, from the search for accurate predictions and risk estimates, to knowledge generation related to concepts, theories, frameworks, approaches, principles, methods, and models to understand, assess, characterize, communicate, and (in a broad sense) manage risk. Examples are used to illustrate the importance of this distinct/separate risk analysis science for solving risk problems, supporting science in general and other disciplines in particular. © 2016 The Authors Risk Analysis published by Wiley Periodicals, Inc. on behalf of Society for Risk Analysis.
Linear stability analysis of collective neutrino oscillations without spurious modes
Morinaga, Taiki; Yamada, Shoichi
2018-01-01
Collective neutrino oscillations are induced by the presence of neutrinos themselves. As such, they are intrinsically nonlinear phenomena and are much more complex than linear counterparts such as the vacuum or Mikheyev-Smirnov-Wolfenstein oscillations. They obey integro-differential equations, for which it is also very challenging to obtain numerical solutions. If one focuses on the onset of collective oscillations, on the other hand, the equations can be linearized and the technique of linear analysis can be employed. Unfortunately, however, it is well known that such an analysis, when applied with discretizations of continuous angular distributions, suffers from the appearance of so-called spurious modes: unphysical eigenmodes of the discretized linear equations. In this paper, we analyze in detail the origin of these unphysical modes and present a simple solution to this annoying problem. We find that the spurious modes originate from the artificial production of pole singularities instead of a branch cut on the Riemann surface by the discretizations. The branching point singularities on the Riemann surface for the original nondiscretized equations can be recovered by approximating the angular distributions with polynomials and then performing the integrals analytically. We demonstrate for some examples that this simple prescription does remove the spurious modes. We also propose an even simpler method: a piecewise linear approximation to the angular distribution. It is shown that the same methodology is applicable to the multienergy case as well as to the dispersion relation approach that was proposed very recently.
Development of probabilistic risk analysis library
International Nuclear Information System (INIS)
Soga, Shota; Kirimoto, Yukihiro; Kanda, Kenichi
2015-01-01
We developed a library that is designed to perform level 1 Probabilistic Risk Analysis using Binary Decision Diagram (BDD). In particular, our goal is to develop a library that will allow Japanese electric utilities to take the advantages of BDD that can solve Event Tree (ET) and Fault Tree (FT) models analytically. Using BDD, the library supports negation in FT which allows more flexible modeling of ET/FT. The library is written by C++ within an object-oriented framework using open source software. The library itself is a header-only library so that Japanese electric utilities can take advantages of its transparency to speed up development and to build their own software for their specific needs. In this report, the basic capabilities of the library is briefly described. In addition, several applications of the library are demonstrated including validation of MCS evaluation of PRA model and evaluation of corrective and preventive maintenance considering common cause failure. (author)
Riva, F; Toebes, M J P; Pijnappels, M; Stagni, R; van Dieën, J H
2013-06-01
Falls have major consequences both at societal (health-care and economy) and individual (physical and psychological) levels. Questionnaires to assess fall risk are commonly used in the clinic, but their predictive value is limited. Objective methods, suitable for clinical application, are hence needed to obtain a quantitative assessment of individual fall risk. Falls in older adults often occur during walking and trunk position is known to play a critical role in balance control. Therefore, analysis of trunk kinematics during gait could present a viable approach to the development of such methods. In this study, nonlinear measures such as harmonic ratio (HR), index of harmonicity (IH), multiscale entropy (MSE) and recurrence quantification analysis (RQA) of trunk accelerations were calculated. These measures are not dependent on step detection, a potentially critical source of error. The aim of the present study was to investigate the association between the aforementioned measures and fall history in a large sample of subjects (42 fallers and 89 non - fallers) aged 50 or older. Univariate associations with fall history were found for MSE and RQA parameters in the AP direction; the best classification results were obtained for MSE with scale factor τ = 2 and for maximum length of diagonals in RQA (72.5% and 71% correct classifications, respectively). MSE and RQA were found to be positively associated with fall history and could hence represent useful tools in the identification of subjects for fall prevention programs. Copyright © 2013 Elsevier B.V. All rights reserved.
Stability Analysis of a Predecessor-Following Platoon of Vehicles With Two Time Delays
Directory of Open Access Journals (Sweden)
Ali Ghasemi
2015-03-01
Full Text Available The problem of controlling a platoon of vehicles moving in one dimension is considered so that they all follow a lead vehicle with constant spacing between successive vehicles. The stability and the string stability of a platoon of vehicles with two independent and uncertain delays, one in the inter-vehicle distance and the other in the relative velocity information channels, are considered. The main objectives of this paper are: (1 using a simplifying factorization procedure and deploying the cluster treatment of characteristic roots (CTCR paradigm to obtain exact stability boundaries in the domain of the delays, and (2 for the purpose of disturbance attenuation, the string stability analysis is examined. Finally, a simulation example of multiple vehicle platoon control is used to demonstrate the effectiveness of the proposed method.
Energy Technology Data Exchange (ETDEWEB)
Hennig, D.; Nechvatal, L. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)
1996-09-01
The report describes the PSI stability analysis methodology and the validation of this methodology based on the international OECD/NEA BWR stability benchmark task. In the frame of this work, the stability properties of some operation points of the NPP Ringhals 1 have been analysed and compared with the experimental results. (author) figs., tabs., 45 refs.
Frequency domain stability analysis of nonlinear active disturbance rejection control system.
Li, Jie; Qi, Xiaohui; Xia, Yuanqing; Pu, Fan; Chang, Kai
2015-05-01
This paper applies three methods (i.e., root locus analysis, describing function method and extended circle criterion) to approach the frequency domain stability analysis of the fast tool servo system using nonlinear active disturbance rejection control (ADRC) algorithm. Root locus qualitative analysis shows that limit cycle is generated because the gain of the nonlinear function used in ADRC varies with its input. The parameters in the nonlinear function are adjustable to suppress limit cycle. In the process of root locus analysis, the nonlinear function is transformed based on the concept of equivalent gain. Then, frequency domain description of the nonlinear function via describing function is presented and limit cycle quantitative analysis including estimating prediction error is presented, which virtually and theoretically demonstrates that the describing function method cannot guarantee enough precision in this case. Furthermore, absolute stability analysis based on extended circle criterion is investigated as a complement. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.
Stokes, Ian A F; Gardner-Morse, Mack G; Henry, Sharon M
2011-10-01
Antagonistic activation of abdominal muscles and increased intra-abdominal pressure are associated with both spinal unloading and spinal stabilization. Rehabilitation regimens have been proposed to improve spinal stability via selective recruitment of certain trunk muscle groups. This biomechanical analytical study addressed whether lumbar spinal stability is increased by such selective activation. The biomechanical model included anatomically realistic three-layers of curved abdominal musculature, rectus abdominis and 77 symmetrical pairs of dorsal muscles. The muscle activations were calculated with the model loaded with either flexion, extension, lateral bending or axial rotation moments up to 60 Nm, along with intra-abdominal pressure up to 5 or 10 kPa (37.5 or 75 mm Hg) and partial bodyweight. After solving for muscle forces, a buckling analysis quantified spinal stability. Subsequently, different patterns of muscle activation were studied by forcing activation of selected abdominal muscles to at least 10% or 20% of maximum. Spinal stability increased by an average factor of 1.8 with doubling of intra-abdominal pressure. Forcing at least 10% activation of obliques or transversus abdominis muscles increased stability slightly for efforts other than flexion, but forcing at least 20% activation generally did not produce further increase in stability. Forced activation of rectus abdominis did not increase stability. Based on analytical predictions, the degree of stability was not substantially influenced by selective forcing of muscle activation. This casts doubt on the supposed mechanism of action of specific abdominal muscle exercise regimens that have been proposed for low back pain rehabilitation. Copyright © 2011 Elsevier Ltd. All rights reserved.
The analysis of thermal stability of detonation nanodiamond
Efremov, V. P.; Zakatilova, E. I.
2016-11-01
The detonation nanodiamond is a new perspective material. Ammunition recycling with use of high explosives and obtaining nanodiamond as the result of the detonation synthesis have given a new motivation for searching of their application areas. In this work nanodiamond powder has been investigated by the method of synchronous thermal analysis. Experiments have been carried out at atmospheric pressure in the environment of argon. Nanodiamond powder has been heated in the closed corundum crucible at the temperature range of 30-1500 °C. The heating rates were varied from 2 K/min to 20 K/min. After the heat treatment, the samples have been studied by the x-ray diffraction and the electron microscopy. As one of the results of this work, it has been found that the detonation nanodiamond has not started the transition into graphite at the temperature below 800 °C.
The analysis of thermal stability of detonation nanodiamond
International Nuclear Information System (INIS)
Efremov, V P; Zakatilova, E I
2016-01-01
The detonation nanodiamond is a new perspective material. Ammunition recycling with use of high explosives and obtaining nanodiamond as the result of the detonation synthesis have given a new motivation for searching of their application areas. In this work nanodiamond powder has been investigated by the method of synchronous thermal analysis. Experiments have been carried out at atmospheric pressure in the environment of argon. Nanodiamond powder has been heated in the closed corundum crucible at the temperature range of 30-1500 °C. The heating rates were varied from 2 K/min to 20 K/min. After the heat treatment, the samples have been studied by the x-ray diffraction and the electron microscopy. As one of the results of this work, it has been found that the detonation nanodiamond has not started the transition into graphite at the temperature below 800 °C. (paper)
Analysis of the CoIE1 stability determinant Rcd.
Sharpe, M E; Chatwin, H M; Macpherson, C; Withers, H L; Summers, D K
1999-08-01
Multimer formation is an important cause of instability for many multicopy plasmids. Plasmid CoIE1 is maintained stably because multimers are converted to monomers by Xer-mediated site-specific recombination at the cer site. However, multimer resolution is not the whole story; inactivation of a promoter (Pcer) within cer causes plasmid instability even though recombination is unaffected. The promoter directs the synthesis of a short transcript (Rcd) which is proposed to delay the division of multimer-containing cells. Mapping of the 5' terminus of Rcd confirms that transcription initiates from Pcer. The 3' terminus shows considerable heterogeneity, consistent with a primary transcript of 95 nt being degraded via intermediates of 79 and 70 nt. Secondary structure predictions for Rcd are presented. Of four mutations which abolish Rcd-mediated growth inhibition, one reduces the activity of Pcer while the other three map to the rcd coding sequence and reduce the steady-state level of the transcript. RNA folding analysis suggests that these three mutant transcripts adopt a common secondary structure in which the major stem-loop differs from that of wild-type Rcd. A survey of 24 cer-like multimer resolution sites revealed six which contain Pcer-like sequences. The putative transcripts from these sites have similar predicted secondary structures to Rcd and contain a highly conserved 15 base sequence. To test the hypothesis that Rcd acts as an anti-sense RNA, interacting with its target gene(s) through the 15 nt sequence, we used DNA hybridization and sequence analysis to find matches to this sequence in the Escherichia coli chromosome. Our failure to find plausible anti-sense targets has led to the suggestion that Rcd may interact directly with a protein target.
Mathematical Model and Stability Analysis of Inverter-Based Distributed Generator
Directory of Open Access Journals (Sweden)
Alireza Khadem Abbasi
2013-01-01
Full Text Available This paper presents a mathematical (small-signal model of an electronically interfaced distributed generator (DG by considering the effect of voltage and frequency variations of the prime source. Dynamic equations are found by linearization about an operating point. In this study, the dynamic of DC part of the interface is included in the model. The stability analysis shows with proper selection of system parameters; the system is stable during steady-state and dynamic situations, and oscillatory modes are well damped. The proposed model is useful to study stability analysis of a standalone DG or a Microgrid.
Linear stability analysis of detonations via numerical computation and dynamic mode decomposition
Kabanov, Dmitry
2018-03-20
We introduce a new method to investigate linear stability of gaseous detonations that is based on an accurate shock-fitting numerical integration of the linearized reactive Euler equations with a subsequent analysis of the computed solution via the dynamic mode decomposition. The method is applied to the detonation models based on both the standard one-step Arrhenius kinetics and two-step exothermic-endothermic reaction kinetics. Stability spectra for all cases are computed and analyzed. The new approach is shown to be a viable alternative to the traditional normal-mode analysis used in detonation theory.
Linear stability analysis of detonations via numerical computation and dynamic mode decomposition
Kabanov, Dmitry I.
2017-12-08
We introduce a new method to investigate linear stability of gaseous detonations that is based on an accurate shock-fitting numerical integration of the linearized reactive Euler equations with a subsequent analysis of the computed solution via the dynamic mode decomposition. The method is applied to the detonation models based on both the standard one-step Arrhenius kinetics and two-step exothermic-endothermic reaction kinetics. Stability spectra for all cases are computed and analyzed. The new approach is shown to be a viable alternative to the traditional normal-mode analysis used in detonation theory.
Classical linear-control analysis applied to business-cycle dynamics and stability
Wingrove, R. C.
1983-01-01
Linear control analysis is applied as an aid in understanding the fluctuations of business cycles in the past, and to examine monetary policies that might improve stabilization. The analysis shows how different policies change the frequency and damping of the economic system dynamics, and how they modify the amplitude of the fluctuations that are caused by random disturbances. Examples are used to show how policy feedbacks and policy lags can be incorporated, and how different monetary strategies for stabilization can be analytically compared. Representative numerical results are used to illustrate the main points.
Stability boundary analysis in single-phase grid-connected inverters with PLL by LTP theory
Salis, Valerio; Costabeber, Alessando; Cox, Stephen M.; Zanchetta, Pericle; Formentini, Andrea
2017-01-01
Stability analysis of power converters in AC net¬works is complex due to the non-linear nature of the conversion systems. Whereas interactions of converters in DC networks can be studied by linearising about the operating point, the extension of the same approach to AC systems poses serious challenges, especially for single-phase or unbalanced three-phase systems. A general method for stability analysis of power converters suitable for single-phase or unbalanced AC networks is presented in th...
Environmental risk analysis for nanomaterials: Review and evaluation of frameworks
DEFF Research Database (Denmark)
Grieger, Khara Deanne; Linkov, Igor; Hansen, Steffen Foss
2012-01-01
In response to the challenges of conducting traditional human health and ecological risk assessment for nanomaterials (NM), a number of alternative frameworks have been proposed for NM risk analysis. This paper evaluates various risk analysis frameworks proposed for NM based on a number of criteria...... to occupational settings with minor environmental considerations, and most have not been thoroughly tested on a wide range of NM. Care should also be taken when selecting the most appropriate risk analysis strategy for a given risk context. Given this, we recommend a multi-faceted approach to assess...... the environmental risks of NM as well as increased applications and testing of the proposed frameworks for different NM....
HANFORD SAFETY ANALYSIS & RISK ASSESSMENT HANDBOOK (SARAH)
Energy Technology Data Exchange (ETDEWEB)
EVANS, C B
2004-12-21
The purpose of the Hanford Safety Analysis and Risk Assessment Handbook (SARAH) is to support the development of safety basis documentation for Hazard Category 2 and 3 (HC-2 and 3) U.S. Department of Energy (DOE) nuclear facilities to meet the requirements of 10 CFR 830, ''Nuclear Safety Management''. Subpart B, ''Safety Basis Requirements.'' Consistent with DOE-STD-3009-94, Change Notice 2, ''Preparation Guide for U.S. Department of Energy Nonreactor Nuclear Facility Documented Safety Analyses'' (STD-3009), and DOE-STD-3011-2002, ''Guidance for Preparation of Basis for Interim Operation (BIO) Documents'' (STD-3011), the Hanford SARAH describes methodology for performing a safety analysis leading to development of a Documented Safety Analysis (DSA) and derivation of Technical Safety Requirements (TSR), and provides the information necessary to ensure a consistently rigorous approach that meets DOE expectations. The DSA and TSR documents, together with the DOE-issued Safety Evaluation Report (SER), are the basic components of facility safety basis documentation. For HC-2 or 3 nuclear facilities in long-term surveillance and maintenance (S&M), for decommissioning activities, where source term has been eliminated to the point that only low-level, residual fixed contamination is present, or for environmental remediation activities outside of a facility structure, DOE-STD-1120-98, ''Integration of Environment, Safety, and Health into Facility Disposition Activities'' (STD-1120), may serve as the basis for the DSA. HC-2 and 3 environmental remediation sites also are subject to the hazard analysis methodologies of this standard.
Stability and Bifurcation Analysis of a Modified Epidemic Model for Computer Viruses
Directory of Open Access Journals (Sweden)
Chuandong Li
2014-01-01
Full Text Available We extend the three-dimensional SIR model to four-dimensional case and then analyze its dynamical behavior including stability and bifurcation. It is shown that the new model makes a significant improvement to the epidemic model for computer viruses, which is more reasonable than the most existing SIR models. Furthermore, we investigate the stability of the possible equilibrium point and the existence of the Hopf bifurcation with respect to the delay. By analyzing the associated characteristic equation, it is found that Hopf bifurcation occurs when the delay passes through a sequence of critical values. An analytical condition for determining the direction, stability, and other properties of bifurcating periodic solutions is obtained by using the normal form theory and center manifold argument. The obtained results may provide a theoretical foundation to understand the spread of computer viruses and then to minimize virus risks.
Insurability of Cyber Risk: An Empirical Analysis
Biener, Christian; Eling, Martin; Wirfs, Jan Hendrik
2015-01-01
This paper discusses the adequacy of insurance for managing cyber risk. To this end, we extract 994 cases of cyber losses from an operational risk database and analyse their statistical properties. Based on the empirical results and recent literature, we investigate the insurability of cyber risk by systematically reviewing the set of criteria introduced by Berliner (1982). Our findings emphasise the distinct characteristics of cyber risks compared with other operational risks and bring to li...
A nonlinear two-species oscillatory system: bifurcation and stability analysis
Directory of Open Access Journals (Sweden)
C. G. Chakrabarti
2003-06-01
Full Text Available The present paper dealing with the nonlinear bifurcation analysis of two-species oscillatory system consists of three parts. The first part deals with Hopf-bifurcation and limit cycle analysis of the homogeneous system. The second consists of travelling wave train solution and its linear stability analysis of the system in presence of diffusion. The last deals with an oscillatory chemical system as an illustrative example.
Edwards, Ellen P; Eiden, Rina D; Leonard, Kenneth E
2004-11-01
This study examined short-term attachment stability and sought to identify predictors of stability and change within a sample characterized by fathers' alcoholism. Results suggest moderate stability of attachment classifications (60% for mothers, 53% for fathers) from 12 to 18 months. Higher paternal and maternal alcohol symptoms, maternal depression, and maternal antisocial behavior were found in families with stable insecure mother-infant attachment compared to those who were stable secure. Mother-infant stable insecurity was associated with higher levels of maternal negative affect expression during play. Father-infant stable insecurity was associated with lower levels of paternal positive affect expression and decreased sensitivity during play. Stable insecure children also had higher levels of negative affect during parent-infant interactions and higher negative emotionality during other episodes compared to stable secure children. Results indicate that infants who were insecure at both time points had the highest constellation of family risk characteristics.
Analysis and improvement of digital control stability for master-slave manipulator system
International Nuclear Information System (INIS)
Yoshida, Koichi; Yabuta, Tetsuro
1992-01-01
Some bilateral controls of master-slave system have been designed, which can realize high-fidelity telemanipulation as if the operator were manipulating the object directly. While usual robot systems are controlled by software-servo system using digital computer, little work has been published on design and analysis for digital control of these systems, which must consider time-delay of sensor signals and zero order hold effect of command signals on actuators. This paper presents a digital control analysis for single degree of freedom master-slave system including impedance models of both the human operator and the task object, which clarifies some index for the stability. The stability result shows a virtual master-slave system concepts, which improve the digital control stability. We first analyze a dynamic control method of master-slave system in discrete-time system for the stability problem, which can realize high-fidelity telemanipulation in the continuous-time. Secondly, using the results of the stability analysis, the robust control scheme for master-slave system is proposed, and the validity of this scheme is finally confirmed by the simulation. Consequently, it would be considered that any combination of master and slave modules with dynamic model of these manipulators is possible to construct the stable master-slave system. (author)
International Nuclear Information System (INIS)
Zhang Tie-Yan; Zhao Yan; Xie Xiang-Peng
2012-01-01
This paper is concerned with the problem of stability analysis of nonlinear Roesser-type two-dimensional (2D) systems. Firstly, the fuzzy modeling method for the usual one-dimensional (1D) systems is extended to the 2D case so that the underlying nonlinear 2D system can be represented by the 2D Takagi—Sugeno (TS) fuzzy model, which is convenient for implementing the stability analysis. Secondly, a new kind of fuzzy Lyapunov function, which is a homogeneous polynomially parameter dependent on fuzzy membership functions, is developed to conceive less conservative stability conditions for the TS Roesser-type 2D system. In the process of stability analysis, the obtained stability conditions approach exactness in the sense of convergence by applying some novel relaxed techniques. Moreover, the obtained result is formulated in the form of linear matrix inequalities, which can be easily solved via standard numerical software. Finally, a numerical example is also given to demonstrate the effectiveness of the proposed approach. (general)
Shell stability analysis in a computer aided engineering (CAE) environment
Arbocz, J.; Hol, J. M. A. M.
1993-01-01
The development of 'DISDECO', the Delft Interactive Shell DEsign COde is described. The purpose of this project is to make the accumulated theoretical, numerical and practical knowledge of the last 25 years or so readily accessible to users interested in the analysis of buckling sensitive structures. With this open ended, hierarchical, interactive computer code the user can access from his workstation successively programs of increasing complexity. The computational modules currently operational in DISDECO provide the prospective user with facilities to calculate the critical buckling loads of stiffened anisotropic shells under combined loading, to investigate the effects the various types of boundary conditions will have on the critical load, and to get a complete picture of the degrading effects the different shapes of possible initial imperfections might cause, all in one interactive session. Once a design is finalized, its collapse load can be verified by running a large refined model remotely from behind the workstation with one of the current generation 2-dimensional codes, with advanced capabilities to handle both geometric and material nonlinearities.
Static stability analysis of embedded flexoelectric nanoplates considering surface effects
Ebrahimi, Farzad; Barati, Mohammad Reza
2017-10-01
In this paper, electromechanical buckling behavior of size-dependent flexoelectric nanoplates is investigated based on nonlocal and surface elasticity theories. Flexoelectricity represents the coupling between strain gradients and electrical polarizations. Flexoelectric nanoplates can tolerate higher buckling loads compared with conventional piezoelectric nanoplates, especially at lower thicknesses. The flexoelectric nanoplate is in contact with a two-parameter elastic foundation, which consists of infinite linear springs and a shear layer. Nonlocal elasticity theory of Eringen is applied in the analysis of flexoelectric nanoplates for the first time. The residual surface stresses which are usually neglected in the modeling of flexoelectric nanoplates are incorporated into nonlocal elasticity to provide better understanding of the physics of the problem. Applying an analytical solution which satisfies various boundary conditions, the governing equations obtained from Hamilton's principle are solved. The reliability of the present approach is verified by comparing the obtained results with those provided in literature. Finally, the influences of nonlocal parameter, surface effect, plate geometrical parameters, elastic foundation and boundary conditions on the buckling characteristics of flexoelectric nanoplates are explored.
49 CFR 260.17 - Credit risk premium analysis.
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Credit risk premium analysis. 260.17 Section 260... Financial Assistance § 260.17 Credit risk premium analysis. (a) When Federal appropriations are not available to cover the total subsidy cost, the Administrator will determine the Credit Risk Premium...
Risk Analysis Methods for Deepwater Port Oil Transfer Systems
1976-06-01
This report deals with the risk analysis methodology for oil spills from the oil transfer systems in deepwater ports. Failure mode and effect analysis in combination with fault tree analysis are identified as the methods best suited for the assessmen...
Risk uncertainty analysis methods for NUREG-1150
International Nuclear Information System (INIS)
Benjamin, A.S.; Boyd, G.J.
1987-01-01
Evaluation and display of risk uncertainties for NUREG-1150 constitute a principal focus of the Severe Accident Risk Rebaselining/Risk Reduction Program (SARRP). Some of the principal objectives of the uncertainty evaluation are: (1) to provide a quantitative estimate that reflects, for those areas considered, a credible and realistic range of uncertainty in risk; (2) to rank the various sources of uncertainty with respect to their importance for various measures of risk; and (3) to characterize the state of understanding of each aspect of the risk assessment for which major uncertainties exist. This paper describes the methods developed to fulfill these objectives