Stability of molecular dynamics simulations of classical systems

DEFF Research Database (Denmark)

Toxværd, Søren

2012-01-01

The existence of a shadow Hamiltonian for discrete classical dynamics, obtained by an asymptotic expansion for a discrete symplectic algorithm, is employed to determine the limit of stability for molecular dynamics (MD) simulations with respect to the time-increment h of the discrete dynamics....... The investigation is based on the stability of the shadow energy, obtained by including the first term in the asymptotic expansion, and on the exact solution of discrete dynamics for a single harmonic mode. The exact solution of discrete dynamics for a harmonic potential with frequency ω gives a criterion...... for the limit of stability h ⩽ 2/ω. Simulations of the Lennard-Jones system and the viscous Kob-Andersen system show that one can use the limit of stability of the shadow energy or the stability criterion for a harmonic mode on the spectrum of instantaneous frequencies to determine the limit of stability of MD...

No-scale D-term inflation with stabilized moduli

Energy Technology Data Exchange (ETDEWEB)

Buchmueller, Wilfried; Domcke, Valerie; Wieck, Clemens

2013-09-15

We study the consistency of hybrid inflation and moduli stabilization, using the Kallosh- Linde model as an example for the latter. We find that F-term hybrid inflation is not viable since inflationary trajectories are destabilized by tachyonic modes. On the other hand, D-term hybrid inflation is naturally compatible with moduli stabilization due to the absence of a large superpotential term during the inflationary phase. Our model turns out to be equivalent to superconformal D-term inflation and it therefore successfully accounts for the CMB data in the large-field regime. Supersymmetry breaking can be incorporated via an O'Raifeartaigh model. For GUT-scale inflation one obtains a stringent bound on the gravitino mass. A rough estimate yields m{sub 3/2}>or similar 10{sup 5} GeV, contrary to naive expectation.

No-scale D-term inflation with stabilized moduli

International Nuclear Information System (INIS)

Buchmueller, Wilfried; Domcke, Valerie; Wieck, Clemens

2013-09-01

We study the consistency of hybrid inflation and moduli stabilization, using the Kallosh- Linde model as an example for the latter. We find that F-term hybrid inflation is not viable since inflationary trajectories are destabilized by tachyonic modes. On the other hand, D-term hybrid inflation is naturally compatible with moduli stabilization due to the absence of a large superpotential term during the inflationary phase. Our model turns out to be equivalent to superconformal D-term inflation and it therefore successfully accounts for the CMB data in the large-field regime. Supersymmetry breaking can be incorporated via an O'Raifeartaigh model. For GUT-scale inflation one obtains a stringent bound on the gravitino mass. A rough estimate yields m 3/2 >or similar 10 5 GeV, contrary to naive expectation.

Preliminary long-term stability criteria for compressed air energy storage caverns in salt domes

Energy Technology Data Exchange (ETDEWEB)

Thoms, R.L.; Martinez, J.D.

1978-08-01

Air storage caverns, which are an essential and integral component of a CAES plant, should be designed and operated so as to perform satisfactorily over the intended life of the overall facility. It follows that the long-term ''stability'' of air storage caverns must be considered as a primary concern in projecting the satisfactory operation of CAES facilities. As used in the report, ''stability'' of a storage cavern implies the extent to which an acceptable amount of cavern storage volume can be utilized with routine maintenance for a specified time interval, e.g., 35 years. In this context, cavern stability is relative to both planned utilization and time interval of operation. The objective of the study was to review the existing literature and consult knowledgeable workers in the storage industry, and then report state-of-the-art findings relative to long-term stability of compressed air energy storage caverns in salt domes. Further, preliminary cavern stability criteria were to be presented in a form consistent with the amount of information available on cavern performance in salt domes. Another objective of the study was to outline a methodology for determining the long-term stability of site-specific CAES cavern systems in salt domes.

Stability of position control system in JIPP T-II

International Nuclear Information System (INIS)

Sakurai, Keiichi; Tanahashi, Shygo

1980-01-01

Computations and experiments on the stability of a feedback control system for maintaining a plasma column in equilibrium are described. The time response of the displacement of the plasma to the desired position is examined by solving the equation of motion of the plasma column. We show that the stability of the feedback control system is improved by using an additional term which represents the shift velocity of the plasma column. (author)

LMI-based stability and performance conditions for continuous-time nonlinear systems in Takagi-Sugeno's form.

Science.gov (United States)

Lam, H K; Leung, Frank H F

2007-10-01

This correspondence presents the stability analysis and performance design of the continuous-time fuzzy-model-based control systems. The idea of the nonparallel-distributed-compensation (non-PDC) control laws is extended to the continuous-time fuzzy-model-based control systems. A nonlinear controller with non-PDC control laws is proposed to stabilize the continuous-time nonlinear systems in Takagi-Sugeno's form. To produce the stability-analysis result, a parameter-dependent Lyapunov function (PDLF) is employed. However, two difficulties are usually encountered: 1) the time-derivative terms produced by the PDLF will complicate the stability analysis and 2) the stability conditions are not in the form of linear-matrix inequalities (LMIs) that aid the design of feedback gains. To tackle the first difficulty, the time-derivative terms are represented by some weighted-sum terms in some existing approaches, which will increase the number of stability conditions significantly. In view of the second difficulty, some positive-definitive terms are added in order to cast the stability conditions into LMIs. In this correspondence, the favorable properties of the membership functions and nonlinear control laws, which allow the introduction of some free matrices, are employed to alleviate the two difficulties while retaining the favorable properties of PDLF-based approach. LMI-based stability conditions are derived to ensure the system stability. Furthermore, based on a common scalar performance index, LMI-based performance conditions are derived to guarantee the system performance. Simulation examples are given to illustrate the effectiveness of the proposed approach.

Robust stabilization of nonlinear systems: The LMI approach

Directory of Open Access Journals (Sweden)

Šiljak D. D.

2000-01-01

Full Text Available This paper presents a new approach to robust quadratic stabilization of nonlinear systems within the framework of Linear Matrix Inequalities (LMI. The systems are composed of a linear constant part perturbed by an additive nonlinearity which depends discontinuously on both time and state. The only information about the nonlinearity is that it satisfies a quadratic constraint. Our major objective is to show how linear constant feedback laws can be formulated to stabilize this type of systems and, at the same time, maximize the bounds on the nonlinearity which the system can tolerate without going unstable. We shall broaden the new setting to include design of decentralized control laws for robust stabilization of interconnected systems. Again, the LMI methods will be used to maximize the class of uncertain interconnections which leave the overall system connectively stable. It is useful to learn that the proposed LMI formulation “recognizes” the matching conditions by returning a feedback gain matrix for any prescribed bound on the interconnection terms. More importantly, the new formulation provides a suitable setting for robust stabilization of nonlinear systems where the nonlinear perturbations satisfy the generalized matching conditions.

LMI optimization approach to stabilization of time-delay chaotic systems

International Nuclear Information System (INIS)

Park, Ju H.; Kwon, O.M.

2005-01-01

Based on the Lyapunov stability theory and linear matrix inequality (LMI) technique, this paper proposes a novel control method for stabilization of a class of time-delay chaotic systems. A stabilization criterion is derived in terms of LMIs which can be easily solved by efficient convex optimization algorithms. A numerical example is included to show the advantage of the result derived

Stabilization of periodic solutions in a tethered satellite system by damping injection

DEFF Research Database (Denmark)

Larsen, Martin Birkelund; Blanke, Mogens

2009-01-01

presents a control design for stabilizing these periodic solutions. The design consists of a control law for stabilizing the open-loop equilibrium and a bias term which forces the system trajectory away from the equilibrium. The tether needs to be positioned away from open-loop equilibrium for the tether...... to affect the orbit parameters. An approximation of the periodic solutions of the closed loop system is found as a series expansion in the parameter plane spanned by the controller gain and the bias term. The stability of the solutions is investigated using linear Floquet analysis of the variational...

Design of Simulation Product for Stability of Electric Power System Using Power System Stabilizer and Optimal Control

Science.gov (United States)

Junaidi, Agus; Hamid, K. Abdul

2018-03-01

This paper will discuss the use of optimal control and Power System Stabilizer (PSS) in improving the oscillation of electric power system. Oscillations in the electric power system can occur due to the sudden release of the load (Switcing-Off). The oscillation of an unstable system for a long time causes the equipment to work in an interruption. To overcome this problem, a control device is required that can work effectively in repairing the oscillation. The power system is modeled from the Single Machine Infinite Bus Model (SMIB). The state space equation is used to mathematically model SMIB. SMIB system which is a plant will be formed togetherness state variables (State-Space), using riccati equation then determined the optimal gain as controller plant. Plant is also controlled by Power Stabilizer System using phase compensation method. Using Matlab Software based simulation will be observed response of rotor speed change and rotor angle change for each of the two controlling methods. Simulation results using the Simulink-MATLAB 6.1 software will compare the analysis of the plant state in Open loop state and use the controller. The simulation response shows that the optimal control and PSS can improve the stability of the power system in terms of acceleration to achieve settling-time and Over Shoot improvement. From the results of both methods are able to improve system performance.

A digital intensity stabilization system for HeNe laser

Science.gov (United States)

Wei, Zhimeng; Lu, Guangfeng; Yang, Kaiyong; Long, Xingwu; Huang, Yun

2012-02-01

A digital intensity stabilization system for HeNe laser is developed. Based on a switching power IC to design laser power supply and a general purpose microcontroller to realize digital PID control, the system constructs a closed loop to stabilize the laser intensity by regulating its discharge current. The laser tube is made of glass ceramics and its integrated structure is steady enough to eliminate intensity fluctuations at high frequency and attenuates all intensity fluctuations, and this makes it easy to tune the control loop. The control loop between discharge current and photodiode voltage eliminates the long-term drifts. The intensity stability of the HeNe laser with this system is 0.014% over 12 h.

Bank, Banking System, Macroprudential Supervision, Stability of Banking System

Directory of Open Access Journals (Sweden)

Tetiana Vasilyeva

2016-10-01

assets to short term liabilities ratio and cost to income ratio. Empirical results of the research found out that grate damage to the stability of banking system has some parameters of banking activity, that’s why the main purpose of the regulation by the National Bank of Ukraine should be strengthening of macroprudential supervision and intensification of adaptation of Basel II and Basel III requirements

Short term outcome of posterior dynamic stabilization system in degenerative lumbar diseases

Directory of Open Access Journals (Sweden)

Mingyuan Yang

2014-01-01

Conclusion: Dynamic stabilization system treating lumbar degenerative disease showed clinical benefits with motion preservation of the operated segments, but does not have the significant advantage on motion preservation at adjacent segments, to avoid the degeneration of adjacent intervertebral disk.

Solving the stability-accuracy-diversity dilemma of recommender systems

Science.gov (United States)

Hou, Lei; Liu, Kecheng; Liu, Jianguo; Zhang, Runtong

2017-02-01

Recommender systems are of great significance in predicting the potential interesting items based on the target user's historical selections. However, the recommendation list for a specific user has been found changing vastly when the system changes, due to the unstable quantification of item similarities, which is defined as the recommendation stability problem. To improve the similarity stability and recommendation stability is crucial for the user experience enhancement and the better understanding of user interests. While the stability as well as accuracy of recommendation could be guaranteed by recommending only popular items, studies have been addressing the necessity of diversity which requires the system to recommend unpopular items. By ranking the similarities in terms of stability and considering only the most stable ones, we present a top- n-stability method based on the Heat Conduction algorithm (denoted as TNS-HC henceforth) for solving the stability-accuracy-diversity dilemma. Experiments on four benchmark data sets indicate that the TNS-HC algorithm could significantly improve the recommendation stability and accuracy simultaneously and still retain the high-diversity nature of the Heat Conduction algorithm. Furthermore, we compare the performance of the TNS-HC algorithm with a number of benchmark recommendation algorithms. The result suggests that the TNS-HC algorithm is more efficient in solving the stability-accuracy-diversity triple dilemma of recommender systems.

Stabilization of soil hydraulic properties under a long term no-till system

Directory of Open Access Journals (Sweden)

Luis Alberto Lozano

2014-08-01

Full Text Available The area under the no-tillage system (NT has been increasing over the last few years. Some authors indicate that stabilization of soil physical properties is reached after some years under NT while other authors debate this. The objective of this study was to determine the effect of the last crop in the rotation sequence (1st year: maize, 2nd year: soybean, 3rd year: wheat/soybean on soil pore configuration and hydraulic properties in two different soils (site 1: loam, site 2: sandy loam from the Argentinean Pampas region under long-term NT treatments in order to determine if stabilization of soil physical properties is reached apart from a specific time in the crop sequence. In addition, we compared two procedures for evaluating water-conducting macroporosities, and evaluated the efficiency of the pedotransfer function ROSETTA in estimating the parameters of the van Genuchten-Mualem (VGM model in these soils. Soil pore configuration and hydraulic properties were not stable and changed according to the crop sequence and the last crop grown in both sites. For both sites, saturated hydraulic conductivity, K0, water-conducting macroporosity, εma, and flow-weighted mean pore radius, R0ma, increased from the 1st to the 2nd year of the crop sequence, and this was attributed to the creation of water-conducting macropores by the maize roots. The VGM model adequately described the water retention curve (WRC for these soils, but not the hydraulic conductivity (K vs tension (h curve. The ROSETTA function failed in the estimation of these parameters. In summary, mean values of K0 ranged from 0.74 to 3.88 cm h-1. In studies on NT effects on soil physical properties, the crop effect must be considered.

Preparation of Astaxanthin Nanodispersions Using Gelatin-Based Stabilizer Systems

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Navideh Anarjan

2014-09-01

Full Text Available The incorporation of lipophilic nutrients, such as astaxanthin (a fat soluble carotenoid in nanodispersion systems can either increase the water solubility, stability and bioavailability or widen their applications in aqueous food and pharmaceutical formulations. In this research, gelatin and its combinations with sucrose oleate as a small molecular emulsifier, sodium caseinate (SC as a protein and gum Arabic as a polysaccharide were used as stabilizer systems in the formation of astaxanthin nanodispersions via an emulsification-evaporation process. The results indicated that the addition of SC to gelatin in the stabilizer system could increase the chemical stability of astaxanthin nanodispersions significantly, while using a mixture of gelatin and sucrose oleate as a stabilizer led to production of nanodispersions with the smallest particle size (121.4 ± 8.6 nm. It was also shown that a combination of gelatin and gum Arabic could produce optimal astaxanthin nanodispersions in terms of physical stability (minimum polydispersity index (PDI and maximum zeta-potential. This study demonstrated that the mixture of surface active compounds showed higher emulsifying and stabilizing functionality compared to using them individually in the preparation of astaxanthin nanodispersions.

Long-term stability scintillation tiles for LHCb detector

CERN Document Server

Grinyov, B V; Khlapova, N P; Lebedev, V N; Melnychuk, S V; Senchyshyn, V G

2004-01-01

Accelerated thermal aging tests of materials-UPS-923A, UPS-96G, UPS-96GM and their analogues, SCSN-81 (Kuraray) and BC-408 (Bicron)- were made. A forecast of tile lifetime was made for normal conditions of usage (20% reduction of light output and 50% reduction of the bulk attenuation length (BAL) and technical attenuation length (TAL). Scintillator UPS-96GM has the most long-term stability of parameters- more than 11 yr. BC-408 samples have the minimum lifetime ~7 yr. The long-term stability, calculated by light yield reduction, of UPS-96G, UPS-923A and SCSN-81 is 10, 9 and 8 yr, respectively.

Long-term stability scintillation tiles for LHCb detector

International Nuclear Information System (INIS)

Grinyov, B.V.; Khlapova, N.P.; Senchyshyn, V.G.; Lebedev, V.N.; Adadurov, A.F.; Melnychuk, S.V.

2004-01-01

Accelerated thermal aging tests of materials - UPS-923A, UPS-96G, UPS-96GM and their analogues, SCSN-81 (Kuraray) and BC-408 (Bicron) - were made. A forecast of tile lifetime was made for normal conditions of usage (20% reduction of light output and 50% reduction of the bulk attenuation length (BAL) and technical attenuation length (TAL). Scintillator UPS-96GM has the most long-term stability of parameters--more than 11 yr. BC-408 samples have the minimum lifetime ∼7 yr. The long-term stability, calculated by light yield reduction, of UPS-96G, UPS-923A and SCSN-81 is 10, 9 and 8 yr, respectively

Differential algebras with remainder and rigorous proofs of long-term stability

International Nuclear Information System (INIS)

Berz, Martin

1997-01-01

It is shown how in addition to determining Taylor maps of general optical systems, it is possible to obtain rigorous interval bounds for the remainder term of the n-th order Taylor expansion. To this end, the three elementary operations of addition, multiplication, and differentiation in the Differential Algebraic approach are augmented by suitable interval operations in such a way that a remainder bound of the sum, product, and derivative is obtained from the Taylor polynomial and remainder bound of the operands. The method can be used to obtain bounds for the accuracy with which a Taylor map represents the true map of the particle optical system. In a more general sense, it is also useful for a variety of other numerical problems, including rigorous global optimization of highly complex functions. Combined with methods to obtain pseudo-invariants of repetitive motion and extensions of the Lyapunov- and Nekhoroshev stability theory, the latter can be used to guarantee stability for storage rings and other weakly nonlinear systems

Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments

Directory of Open Access Journals (Sweden)

Martin Čížek

2014-01-01

Full Text Available A passive optical resonator is a special sensor used for measurement of lengths on the nanometer and sub-nanometer scale. A stabilized optical frequency comb can provide an ultimate reference for measuring the wavelength of a tunable laser locked to the optical resonator. If we lock the repetition and offset frequencies of the comb to a high-grade radiofrequency (RF oscillator its relative frequency stability is transferred from the RF to the optical frequency domain. Experiments in the field of precise length metrology of low-expansion materials are usually of long-term nature so it is required that the optical frequency comb stay in operation for an extended period of time. The optoelectronic closed-loop systems used for stabilization of combs are usually based on traditional analog electronic circuits processing signals from photodetectors. From an experimental point of view, these setups are very complicated and sensitive to ambient conditions, especially in the optical part, therefore maintaining long-time operation is not easy. The research presented in this paper deals with a novel approach based on digital signal processing and a software-defined radio. We describe digital signal processing algorithms intended for keeping the femtosecond optical comb in a long-time stable operation. This need arose during specialized experiments involving measurements of optical frequencies of tunable continuous-wave lasers. The resulting system is capable of keeping the comb in lock for an extensive period of time (8 days or more with the relative stability better than 1.6 × 10−11.

Wind Turbine and Wind Power Plant Modelling Aspects for Power System Stability Studies

DEFF Research Database (Denmark)

Altin, Müfit; Hansen, Anca Daniela; Göksu, Ömer

2014-01-01

Large amount of wind power installations introduce modeling challenges for power system operators at both the planning and operational stages of power systems. Depending on the scope of the study, the modeling details of the wind turbine or the wind power plant are required to be different. A wind...... turbine model which is developed for the short-term voltage stability studies can be inaccurate and sufficient for the frequency stability studies. Accordingly, a complete and detailed wind power plant model for every kind of study is not feasible in terms of the computational time and also...... and wind power plants are reviewed for power system stability studies. Important remarks of the models are presented by means of simulations to emphasize the impact of these modelling details on the power system....

Chest wall stabilization and reconstruction: short and long-term results 5 years after the introduction of a new titanium plates system.

Science.gov (United States)

De Palma, Angela; Sollitto, Francesco; Loizzi, Domenico; Di Gennaro, Francesco; Scarascia, Daniele; Carlucci, Annalisa; Giudice, Giuseppe; Armenio, Andrea; Ludovico, Rossana; Loizzi, Michele

2016-03-01

We report short and long-term results with the dedicated Synthes(®) titanium plates system, introduced 5 years ago, for chest wall stabilization and reconstruction. We retrospectively analyzed (January 2010 to December 2014) 27 consecutive patients (22 males, 5 females; range 16-83 years, median age 60 years), treated with this system: primary [3] and secondary [8] chest wall tumor; flail chest [5]; multiple ribs fractures [5]; sternal dehiscence-diastasis [3]; sternal fracture [1]; sternoclavicular joint dislocation [1]; Poland syndrome [1]. Short-term results were evaluated as: operating time, post-operative morbidity, mortality, hospital stay; long-term results as: survival, plates-related morbidity, spirometric values, chest pain [measured with Verbal Rating Scale (VRS) and SF12 standard V1 questionnaire]. Each patient received from 1 to 10 (median 2) titanium plates/splints; median operating time was 150 min (range: 115-430 min). Post-operative course: 15 patients (55.6%) uneventful, 10 (37%) minor complications, 2 (7.4%) major complications; no post-operative mortality. Median post-operative hospital stay was 13 days (range: 5-129 days). At a median follow-up of 20 months (range: 1-59 months), 21 patients (78%) were alive, 6 (22%) died. Three patients presented long-term plates-related morbidity: plates rupture [2], pin plate dislodgment [1]; two required a second surgical look. One-year from surgery median spirometric values were: FVC 3.31 L (90%), FEV1 2.46 L (78%), DLCO 20.9 mL/mmHg/min (76%). On 21 alive patients, 7 (33.3%) reported no pain (VRS score 0), 10 (47.6%) mild (score 2), 4 (19.1%) moderate (score 4), no-one severe (score >4); 15 (71.5%) reported none or mild, 6 (28.5%) moderate pain influencing quality of life. An optimal chest wall stabilization and reconstruction was achieved with the Synthes(®) titanium plates system, with minimal morbidity, no post-operative mortality, acceptable operating time and post-operative hospital stay. Long-term

Comparison of long-term stability of containment systems for residues and wastes contaminated with naturally occurring radionuclides at an arid site and two humid sites

International Nuclear Information System (INIS)

Winters, M.; Merry-Libby, P.; Hinchman, R.

1985-01-01

The long-term stability of near-surface containment systems designed for the management of radioactive wastes and residues contaminated with naturally occurring radionuclides are compared at the three different sites. The containment designs are: (1) a diked 8.9-m high mound, including a 3.2-m layered cap at a site (humid) near Lewiston, New York, (2) a 6.8-m-high mound, including a similar 3.2-m cap at a site (humid) near Oak Ridge, Tennessee, and (3) 4.8-m deep trenches with 3.0-m backfilled caps at a site (arid) near Hanford, Washington. Geological, hydrological, and biological factors affecting the long-term (1000-year) integrity of the containment systems at each site are examined, including: erosion, flooding, drought, wildfire, slope and cover failure, plant root penetration, burrowing animals, other soil-forming processes, and land-use changes. For the containment designs evaluated, releases of radon-222 at the arid site are predicted to be several orders of magnitude higher than at the two humid sites - upon initial burial and at 1000 years (after severe erosion). Transfer of wastes containing naturally occurring radionuclides from a humid to an arid environment offers little or no advantage relative to long-term stability of the containment system and has a definite disadvantage in terms of gaseous radioactive releases. 26 references, 3 figures, 4 tables

Stability Analysis of Periodic Systems by Truncated Point Mappings

Science.gov (United States)

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.

Long-term stability of oxidative stress biomarkers in human serum.

NARCIS (Netherlands)

Jansen, Eugène H J M; Beekhof, Piet K; Viezeliene, Dale; Muzakova, Vladimira; Skalicky, Jiri

2017-01-01

The storage time and storage temperature might affect stability of oxidative stress biomarkers, therefore, they have to be analyzed after long-term storage of serum samples. The stability of three biomarkers reflecting oxidative stress: reactive oxygen metabolites (ROM) for hydroperoxides, total

The long term stability of lidar calibrations

DEFF Research Database (Denmark)

Courtney, Michael; Gayle Nygaard, Nicolai

Wind lidars are now used extensively for wind resource measurements. One of the requirements for the data to be accepted in support of project financing (so-called ‘banka-bility’) is to demonstrate the long-term stability of lidar cali-brations. Calibration results for six Leosphere WindCube li...

Impact of PSS and SVC on the Power System Transient Stability

Directory of Open Access Journals (Sweden)

Mohammed Omar Benaissa

2017-06-01

Full Text Available The Static Var Compensator (SVC is used to improve the stability of the power system because of its role in injecting or absorbing the reactive power in the electrical transmission lines. The Power System Stabilizer (PSS is also a control device which ensures maximum power transfer and thus the stability of the power system enhancement. The PSS has been widely used to damp electromechanical oscillations occur in power systems. If no adequate damping is available, the oscillations will increase leading to instability. The present work is an original contribution to the problem of transient stability in the electrical power system, the authors have made some efforts to illustrate the flexibility and the importance of inserting the SVC alone or with the PSS the fact that maintain the characteristics of the system within acceptable limits in a very short time. The results show that the system has been developed successfully in terms of transient stability in a bi-machine transmission system only with the presence of PSS when a single-phase fault has been occurred, while the presence of SVC is more than essential when a three-phase fault is occurred.

DESCRIBING FUNCTION METHOD FOR PI-FUZZY CONTROLLED SYSTEMS STABILITY ANALYSIS

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Stefan PREITL

2004-12-01

Full Text Available The paper proposes a global stability analysis method dedicated to fuzzy control systems containing Mamdani PI-fuzzy controllers with output integration to control SISO linear / linearized plants. The method is expressed in terms of relatively simple steps, and it is based on: the generalization of the describing function method for the considered fuzzy control systems to the MIMO case, the approximation of the describing functions by applying the least squares method. The method is applied to the stability analysis of a class of PI-fuzzy controlled servo-systems, and validated by considering a case study.

Adaptive Integral Sliding Mode Stabilization of Nonholonomic Drift-Free Systems

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Waseem Abbasi

2016-01-01

Full Text Available This article presents adaptive integral sliding mode control algorithm for the stabilization of nonholonomic drift-free systems. First the system is transformed, by using input transform, into a special structure containing a nominal part and some unknown terms which are computed adaptively. The transformed system is then stabilized using adaptive integral sliding mode control. The stabilizing controller for the transformed system is constructed that consists of the nominal control plus a compensator control. The compensator control and the adaptive laws are derived on the basis of Lyapunov stability theory. The proposed control algorithm is applied to three different nonholonomic drift-free systems: the unicycle model, the front wheel car model, and the mobile robot with trailer model. The controllability Lie algebra of the unicycle model contains Lie brackets of depth one, the model of a front wheel car contains Lie brackets of depths one and two, and the model of a mobile robot with trailer contains Lie brackets of depths one, two, and three. The effectiveness of the proposed control algorithm is verified through numerical simulations.

Interval stability for complex systems

Science.gov (United States)

Klinshov, Vladimir V.; Kirillov, Sergey; Kurths, Jürgen; Nekorkin, Vladimir I.

2018-04-01

Stability of dynamical systems against strong perturbations is an important problem of nonlinear dynamics relevant to many applications in various areas. Here, we develop a novel concept of interval stability, referring to the behavior of the perturbed system during a finite time interval. Based on this concept, we suggest new measures of stability, namely interval basin stability (IBS) and interval stability threshold (IST). IBS characterizes the likelihood that the perturbed system returns to the stable regime (attractor) in a given time. IST provides the minimal magnitude of the perturbation capable to disrupt the stable regime for a given interval of time. The suggested measures provide important information about the system susceptibility to external perturbations which may be useful for practical applications. Moreover, from a theoretical viewpoint the interval stability measures are shown to bridge the gap between linear and asymptotic stability. We also suggest numerical algorithms for quantification of the interval stability characteristics and demonstrate their potential for several dynamical systems of various nature, such as power grids and neural networks.

THE IMPACT OF THE FOREIGN CAPITAL BANKS ON ENSURING FINANCIAL STABILITY ON LONG TERM

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Isac\tBORS

2015-06-01

Full Text Available The present study is focusing on analysing the role played by the foreign banks within the national and international banking system as well the impact the foreign banks have on the autochthon banking system, on the financial activity, on the real economy and on the financial stability on long terms. The research conducted highlights the fact that along the positive impact on the banking system and on the economy of the host country, generated by their quality as vectors of mobilizing and directioning the international financial flows towards the host country, there can also be considered a negative impact. The study shows that the impact of the negative effects, that have as main cause the reversibility of the international financial flows, depends, on a great extent, on the specific conditions of the host country, on the characteristics of the foreign banks, but mostly, by the share held by the foreign countries within the framework of the host banking system. Starting from the role played by the capitalization of the banking system to ensure financial stability, the research made on Romania’s case shows both, the positive effects generated by the presence of the foreign banks and also, their vulnerability in front of this excessive dependence on the foreign capital induced by this presence. The solution to reduce this dependence can only come from the autochthon capital direction whose mobilization may countervail the gap made by the foreign banks and, by surceasing the process of financial disintermediation, to ensure the maintenance of the financial stability on long term.

New image-stabilizing system

Science.gov (United States)

Zhao, Yuejin

1996-06-01

In this paper, a new method for image stabilization with a three-axis image- stabilizing reflecting prism assembly is presented, and the principle of image stabilization in this prism assembly, formulae for image stabilization and working formulae with an approximation up to the third power are given in detail. In this image-stabilizing system, a single chip microcomputer is used to calculate value of compensating angles and thus to control the prism assembly. Two gyroscopes act as sensors from which information of angular perturbation is obtained, three stepping motors drive the prism assembly to compensate for the movement of image produced by angular perturbation. The image-stabilizing device so established is a multifold system which involves optics, mechanics, electronics and computer.

A survey of short-term and long-term stability of tube parameters in a mammography unit

Directory of Open Access Journals (Sweden)

Praskalo Jovica Ž.

2014-01-01

Full Text Available In order to set up a successful mammography screening program in the Republic of Srpska, a Siemens Mammomat 1000 X-ray machine was selected for analysis as the said mammography system is widely used in clinical practice. The variations in tube parameters (specific air kerma, high-voltage accuracy and reproducibility, linearity between exposure and dose exposure time were monitored over a five-year period, from 2008 to 2012. In addition, due to observed daily fluctuations for chosen parameters, a series of measurements were performed three times a day within a single-month period (mainly October 2012. The goal of such an experimental set up is to assess short-term and long-term stability of tube parameters in the given mammography unit and to make a comparison between them. The present paper shows how an early detection of significant parameter fluctuations can help eliminate irregularities and optimize the performance of mammography systems. [Projekat Ministarstva nauke Republike Srbije, br. 171007

Modeling flood events for long-term stability

International Nuclear Information System (INIS)

Schruben, T.; Portillo, R.

1985-01-01

The primary objective for the disposal of uranium mill tailings in the Uranium Mill Tailings Remedial Action (UMTRA) Project is isolation and stabilization to prevent their misuse by man and dispersal by natural forces such as wind, rain, and flood waters (40 CFR-192). Stabilization of sites that are located in or near flood plains presents unique problems in design for long-term performance. This paper discusses the process involved with the selection and hydrologic modeling of the design flood event; and hydraulic modeling with geomorphic considerations of the design flood event. The Gunnison, Colorado, and Riverton, Wyoming, sites will be used as examples in describing the process

Algorithm for Stabilizing a POD-Based Dynamical System

Science.gov (United States)

Kalb, Virginia L.

2010-01-01

This algorithm provides a new way to improve the accuracy and asymptotic behavior of a low-dimensional system based on the proper orthogonal decomposition (POD). Given a data set representing the evolution of a system of partial differential equations (PDEs), such as the Navier-Stokes equations for incompressible flow, one may obtain a low-dimensional model in the form of ordinary differential equations (ODEs) that should model the dynamics of the flow. Temporal sampling of the direct numerical simulation of the PDEs produces a spatial time series. The POD extracts the temporal and spatial eigenfunctions of this data set. Truncated to retain only the most energetic modes followed by Galerkin projection of these modes onto the PDEs obtains a dynamical system of ordinary differential equations for the time-dependent behavior of the flow. In practice, the steps leading to this system of ODEs entail numerically computing first-order derivatives of the mean data field and the eigenfunctions, and the computation of many inner products. This is far from a perfect process, and often results in the lack of long-term stability of the system and incorrect asymptotic behavior of the model. This algorithm describes a new stabilization method that utilizes the temporal eigenfunctions to derive correction terms for the coefficients of the dynamical system to significantly reduce these errors.

Long-term stability of orbits in storage rings

International Nuclear Information System (INIS)

Warnock, R.L.; Ruth, R.D.

1990-06-01

We describe a numerical method to establish long-term bounds on nonlinear Hamiltonian motion. By bounding the change in a nearly constant action variable, uniformly in initial condition, one can predict stability for N turns by tracking many orbits for a member of turns of N 0 much less than N. In a first application to a model sextupole lattice in a region of strong nonlinearity, we predict stability of betatron motion in two degrees of freedom for 10 8 turns. 5 refs., 3 figs

Finite-Time Stability Analysis of Discrete-Time Linear Singular Systems

Directory of Open Access Journals (Sweden)

Songlin Wo

2014-01-01

Full Text Available The finite-time stability (FTS problem of discrete-time linear singular systems (DTLSS is considered in this paper. A necessary and sufficient condition for FTS is obtained, which can be expressed in terms of matrix inequalities. Then, another form of the necessary and sufficient condition for FTS is also given by using matrix-null space technology. In order to solve the stability problem expediently, a sufficient condition for FTS is given via linear matrix inequality (LMI approach; this condition can be expressed in terms of LMIs. Finally, an illustrating example is also given to show the effectiveness of the proposed method.

FINANCIAL STABILITY OF THE UKRAINE NATIONAL SYSTEM OF PENSION INSURANCE

Directory of Open Access Journals (Sweden)

A. Khemii

2014-03-01

Full Text Available The system of pension insurance is a combination of created by the state legal, economic and organizational institutions and norms, providing financial support to citizens in the form of pensions. In the article analyzing the demographic situation and the condition of pension payments in the country today. In the terms of economic and social reforms, the level of financial stability the pension system is low. Therefore important is the analysis and exploring new methods to ensure financial stability of the Ukraine national system of pension insurance. The main institution of the national pension insurance is the National Pension Fund of Ukraine.

Stabilization and tracking controller for a class of nonlinear discrete-time systems

International Nuclear Information System (INIS)

Sharma, B.B.; Kar, I.N.

2011-01-01

Highlights: → We present recursive design of stabilizing controller for nonlinear discrete-time systems. → Problem of stabilizing and tracking control of single link manipulator system is addressed. → We extend the proposed results to output tracking problems. → The proposed methodology is applied satisfactorily to discrete-time chaotic maps. - Abstract: In this paper, stabilization and tracking control problem for parametric strict feedback class of discrete time systems is addressed. Recursive design of control function based on contraction theory framework is proposed instead of traditional Lyapunov based method. Explicit structure of controller is derived for the addressed class of nonlinear discrete-time systems. Conditions for exponential stability of system states are derived in terms of controller parameters. At each stage of recursive procedure a specific structure of Jacobian matrix is ensured so as to satisfy conditions of stability. The closed loop dynamics in this case remains nonlinear in nature. The proposed algorithm establishes global stability results in quite a simple manner as it does not require formulation of error dynamics. Problem of stabilization and output tracking control in case of single link manipulator system with actuator dynamics is analyzed using the proposed strategy. The proposed results are further extended to stabilization of discrete time chaotic systems. Numerical simulations presented in the end show the effectiveness of the proposed approach.

Development of Technique for Testing the Long-Term Stability of Silicon Microstrip Detectors

International Nuclear Information System (INIS)

Kosinov, A.V.; Maslov, N.I.; Naumov, S.V.; Ovchinnik, V.D.; Starodubtsev, A.F.; Vasiliev, G.P.; Yalovenko, V.I.; Bosisio, L.

2006-01-01

An automatic multi-channel set-up prototype for simultaneous testing of the Long-Term Stability (LTS) of more than ten detectors is described. The Inner Tracking System of the ALICE experiment will include about two thousand Double-sided Microstrip Detectors (DSMD). Efficient automatic measurement techniques are crucial for the LTS test, because the corresponding test procedure should be performed on each detector and requires long time, at least two days. By using special adapters for supporting and connecting the bare DSMDs, failing detectors can be screened out before module assembly, thus minimizing the cost. Automated probe stations developed for a special purpose or for microelectronics industry are used for measuring physical static DSMD characteristics and check good-to-bad elements ratio for DSMD. However, automated (or semi-automatic)test benches for studying LTS or testing DSMD long-term stability before developing a detecting module are absent

Endogenous, reactive and neurotic depression -- diagnostic stability and long-term outcome

DEFF Research Database (Denmark)

Kessing, Lars Vedel

2004-01-01

with a diagnosis of endogenous, reactive or neurotic depression according to ICD-8 were identified in a nationwide register of admissions to psychiatric wards. Patients were followed up to 1999 and the long-term diagnostic stability, the risk of relapse leading to readmission and the risk of suicide was analysed...... with reactive depression had less risk of relapse. No differences were found in the risk of completed suicide between the three groups of patients during long-term follow-up. CONCLUSIONS: The study does not provide evidence for re-establishing prior diagnostic systems of depressive disorders based......BACKGROUND: No larger long-term study has been conducted of outcomes of patients diagnosed with endogenous, reactive or neurotic depression and using survival methods in the analyses. SAMPLING AND METHODS: All patients who had had their first-ever discharge in the period from 1970 to 1994...

Predictive tools and data needs for long term performance of in-situ stabilization and containment systems: DOE/OST stabilization workshop, June 26-27, Park City, Utah

International Nuclear Information System (INIS)

Borns, D.J.

1997-01-01

This paper summarizes the discussion within the Predictive Tools and Data Needs for Long Term Performance Assessment Subgroup. This subgroup formed at the DOE Office of Science and Technology workshop to address long-term performance of in situ stabilization and containment systems. The workshop was held in Park City, Utah, 26 and 27 June, 1996. All projects, engineering and environmental, have built-in decision processes that involve varying risk/reward scenarios. Such decision-processes maybe awkward to describe but are utilized every day following approaches that range from intuitive to advanced mathematical and numerical. Examples are the selection of components of home sound system, the members of a sports team, investments in a portfolio, and the members of a committee. Inherent in the decision method are an understanding of the function or process of the system requiring a decision or prediction, an understanding of the criteria on which decisions are made such as cost, performance, durability and verifiability. Finally, this process requires a means to judge or predict how the objects, activities, people and processes being analyzed will perform relative to the operations and functions of the system and relative to the decision criteria posed for the problem. These risk and decision analyses are proactive and iterative throughout the life of a remediation project. Prediction inherent to the analyses are based on intuition, experience, trial and error, and system analysis often using numerical approaches

Long term physical and chemical stability of polyelectrolyte multilayer membranes

NARCIS (Netherlands)

de Grooth, Joris; Haakmeester, Brian; Wever, Carlos; Potreck, Jens; de Vos, Wiebe Matthijs; Nijmeijer, Dorothea C.

2015-01-01

This work presents a detailed investigation into the long term stability of polyelectrolyte multilayer (PEM) modified membranes, a key factor for the application of these membranes in water purification processes. Although PEM modified membranes have been frequently investigated, their long term

Power system stabilizer control for wind power to enhance power system stability

OpenAIRE

Domínguez García, José Luís; Gomis Bellmunt, Oriol; Bianchi, Fernando Daniel; Sumper, Andreas

2011-01-01

The paper presents a small signal stability analysis for power systems with wind farm interaction. Power systems have damping oscillation modes that can be excited by disturbance or fault in the grid. The power converters of the wind farms can be used to reduce these oscillations and make the system more stable. These ideas are explored to design a power system stabilized (PSS) for a network with conventional generators and a wind farm in order to increase the damping of the oscillation...

Long-Term Stability of Oxide Nanowire Sensors via Heavily Doped Oxide Contact.

Science.gov (United States)

Zeng, Hao; Takahashi, Tsunaki; Kanai, Masaki; Zhang, Guozhu; He, Yong; Nagashima, Kazuki; Yanagida, Takeshi

2017-12-22

Long-term stability of a chemical sensor is an essential quality for long-term collection of data related to exhaled breath, environmental air, and other sources in the Internet of things (IoT) era. Although an oxide nanowire sensor has shown great potential as a chemical sensor, the long-term stability of sensitivity has not been realized yet due to electrical degradation under harsh sensing conditions. Here, we report a rational concept to accomplish long-term electrical stability of metal oxide nanowire sensors via introduction of a heavily doped metal oxide contact layer. Antimony-doped SnO 2 (ATO) contacts on SnO 2 nanowires show much more stable and lower electrical contact resistance than conventional Ti contacts for high temperature (200 °C) conditions, which are required to operate chemical sensors. The stable and low contact resistance of ATO was confirmed for at least 1960 h under 200 °C in open air. This heavily doped oxide contact enables us to realize the long-term stability of SnO 2 nanowire sensors while maintaining the sensitivity for both NO 2 gas and light (photo) detections. The applicability of our method is confirmed for sensors on a flexible polyethylene naphthalate (PEN) substrate. Since the proposed fundamental concept can be applied to various oxide nanostructures, it will give a foundation for designing long-term stable oxide nanomaterial-based IoT sensors.

Stability Analysis and H∞ Model Reduction for Switched Discrete-Time Time-Delay Systems

Directory of Open Access Journals (Sweden)

Zheng-Fan Liu

2014-01-01

Full Text Available This paper is concerned with the problem of exponential stability and H∞ model reduction of a class of switched discrete-time systems with state time-varying delay. Some subsystems can be unstable. Based on the average dwell time technique and Lyapunov-Krasovskii functional (LKF approach, sufficient conditions for exponential stability with H∞ performance of such systems are derived in terms of linear matrix inequalities (LMIs. For the high-order systems, sufficient conditions for the existence of reduced-order model are derived in terms of LMIs. Moreover, the error system is guaranteed to be exponentially stable and an H∞ error performance is guaranteed. Numerical examples are also given to demonstrate the effectiveness and reduced conservatism of the obtained results.

Convergent systems vs. incremental stability

NARCIS (Netherlands)

Rüffer, B.S.; Wouw, van de N.; Mueller, M.

2013-01-01

Two similar stability notions are considered; one is the long established notion of convergent systems, the other is the younger notion of incremental stability. Both notions require that any two solutions of a system converge to each other. Yet these stability concepts are different, in the sense

Research plan on geosphere stability for long-term isolation of radioactive waste. Scientific programme for fiscal years 2011

International Nuclear Information System (INIS)

Yasue, Ken-ichi; Asamori, Koichi; Kusano, Tomohiro; Saito-Kokubu, Yoko; Tanikawa, Shin-ichi; Niwa, Masakazu; Hanamuro, Takahiro; Yamasaki, Seiko; Yamada, Kunimi; Ishimaru, Tsuneari; Umeda, Koji

2011-07-01

The concept of geological disposal of HLW in Japan is based on a multi-barrier system which combines a stable geological environment with a robust barrier system. Potential geological host formations and their surroundings are chosen, in particular, for their long-term stability, taking into account the fact that Japan is located in a tectonically active zone. This report is a plan of research and development (R and D) on geosphere stability for long-term isolation of HLW in JAEA, in fiscal year 2011. The objectives and contents in fiscal year 2011 are described in detail based on the outline of 5 years plan (fiscal years 2010-2014). In addition, the planed framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. (author)

Research plan on geosphere stability for long-term isolation of radioactive waste. Scientific programme for fiscal years 2012

International Nuclear Information System (INIS)

Asamori, Koichi; Niwa, Masakazu; Hanamuro, Takahiro; Yamada, Kunimi; Kusano, Tomohiro; Makuuchi, Ayumu; Takatori, Ryoichi; Saito-Kokubu, Yoko; Ishimaru, Tsuneari; Umeda, Koji

2012-07-01

The concept of geological disposal of HLW in Japan is based on a multi-barrier system which combines a stable geological environment with a robust barrier system. Potential geological host formations and their surroundings are chosen, in particular, for their long-term stability, taking into account the fact that Japan is located in a tectonically active zone. This report is a plan of research and development (R and D) on geosphere stability for long-term isolation of HLW in JAEA, in fiscal year 2012. The objectives and contents in fiscal year 2012 are described in detail based on the outline of 5 years plan (fiscal years 2010-2014). In addition, the planned framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. (author)

Research plan on geosphere stability for long-term isolation of radioactive waste. Scientific programme for fiscal years 2010

International Nuclear Information System (INIS)

Yasue, Ken-ichi; Asamori, Koichi; Yamada, Kunimi; Saito-Kokubu, Yoko; Yamasaki, Seiko; Kurosawa, Hideki; Tanikawa, Shin-ichi; Negi, Tateyuki; Kusano, Tomohiro; Hanamuro, Takahiro; Ishimaru, Tsuneari; Umeda, Koji

2010-09-01

The concept of geological disposal of HLW in Japan is based on a multibarrier system which combines a stable geological environment with an engineered barrier system. Potential geological host formations and their surroundings are chosen, in particular, for their long-term stability, taking into account the fact that Japan is located in a tectonically active zone. This report is a plan of research and development (R and D) for geosphere stability for long-term isolation of HLW in JAEA, in fiscal year 2010. The objectives and contents in fiscal year 2010 are described in detail based on the outline of 5 years plan (fiscal years 2010-2014). In addition, the plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. (author)

Finite-Time Stability of Large-Scale Systems with Interval Time-Varying Delay in Interconnection

Directory of Open Access Journals (Sweden)

T. La-inchua

2017-01-01

Full Text Available We investigate finite-time stability of a class of nonlinear large-scale systems with interval time-varying delays in interconnection. Time-delay functions are continuous but not necessarily differentiable. Based on Lyapunov stability theory and new integral bounding technique, finite-time stability of large-scale systems with interval time-varying delays in interconnection is derived. The finite-time stability criteria are delays-dependent and are given in terms of linear matrix inequalities which can be solved by various available algorithms. Numerical examples are given to illustrate effectiveness of the proposed method.

Long-term stability of diurnal salivary cortisol and alpha-amylase secretion patterns.

Science.gov (United States)

Skoluda, Nadine; La Marca, Roberto; Gollwitzer, Mario; Müller, Andreas; Limm, Heribert; Marten-Mittag, Birgitt; Gündel, Harald; Angerer, Peter; Nater, Urs M

2017-06-01

This study aimed to investigate long-term stability and variability of diurnal cortisol and alpha-amylase patterns. Diurnal cortisol and alpha-amylase secretion patterns were assessed on a single workday with three waves of measurement across a total time period of 24months in 189 participants. Separate hierarchical linear models were analyzed, with and without a number of potential predictor variables (age, BMI, smoking, chronic stress, stress reactivity). While low long-term stability was found in diurnal cortisol, the stability of diurnal alpha-amylase was moderate across the time period of 24months. Several predictor variables had a positive impact on diurnal cortisol and alpha-amylase secretion patterns averaged across waves. Our findings underpin the notion that long-term stability is not necessarily warranted in longitudinal studies. It is important to choose an appropriate study design when attempting to disentangle clinically and biologically relevant changes from naturally occurring variations in diurnal cortisol and alpha-amylase. Copyright © 2017 Elsevier Inc. All rights reserved.

A study about the long-term stability of sedimentary rock

International Nuclear Information System (INIS)

Yoshino, Naoto; Miyanomae, Shun-ichi; Inoue, Hiroyuki; Nashimoto, Yutaka

2005-02-01

In this paper, following two issues were examined and estimated, (1) the influence of near field condition factor to the dynamical behavior of sedimentary soft rock, (2) the long term estimation of the dynamical behavior considering the condition of Horonobe area. As the study about the influence of near field condition factor to the dynamical behavior of sedimentary soft rock, the thermal factor was focused on and the laboratory tests using test pieces which were sampled in Horonobe area were carried out under the water temperature were 20 degrees and 80 degrees. As a result, the time dependence parameter in variable-compliance-type constitutive-equation could be obtained. And comparison between creep property under 20 degrees and 80 degrees was conducted. In addition, the general properties of sedimentary soft rock under several conditions were identified by the survey of the literature. And the way how to confirm the dynamical properties of sedimentary soft rock with in-situ test were presented. For the study on the short-term and long-term stability of rock surrounding buffer materials, numerical simulations were carried out assuming several conditions. The direction of disposal tunnels and the ratio of rock strength by initial stress were estimated to be the main factor affecting the short-term stability of rock. Time dependency of rock and the stiffness of buffer material were estimated to be the main factor affecting the long-term stability of rock. (author)

A Recursive Fuzzy System for Efficient Digital Image Stabilization

Directory of Open Access Journals (Sweden)

Nikolaos Kyriakoulis

2008-01-01

Full Text Available A novel digital image stabilization technique is proposed in this paper. It is based on a fuzzy Kalman compensation of the global motion vector (GMV, which is estimated in the log-polar plane. The GMV is extracted using four local motion vectors (LMVs computed on respective subimages in the logpolar plane. The fuzzy Kalman system consists of a fuzzy system with the Kalman filter's discrete time-invariant definition. Due to this inherited recursiveness, the output results into smoothed image sequences. The proposed stabilization system aims to compensate any oscillations of the frame absolute positions, based on the motion estimation in the log-polar domain, filtered by the fuzzy Kalman system, and thus the advantages of both the fuzzy Kalman system and the log-polar transformation are exploited. The described technique produces optimal results in terms of the output quality and the level of compensation.

Long term stability of nanowire nanoelectronics in physiological environments.

Science.gov (United States)

Zhou, Wei; Dai, Xiaochuan; Fu, Tian-Ming; Xie, Chong; Liu, Jia; Lieber, Charles M

2014-03-12

Nanowire nanoelectronic devices have been exploited as highly sensitive subcellular resolution detectors for recording extracellular and intracellular signals from cells, as well as from natural and engineered/cyborg tissues, and in this capacity open many opportunities for fundamental biological research and biomedical applications. Here we demonstrate the capability to take full advantage of the attractive capabilities of nanowire nanoelectronic devices for long term physiological studies by passivating the nanowire elements with ultrathin metal oxide shells. Studies of Si and Si/aluminum oxide (Al2O3) core/shell nanowires in physiological solutions at 37 °C demonstrate long-term stability extending for at least 100 days in samples coated with 10 nm thick Al2O3 shells. In addition, investigations of nanowires configured as field-effect transistors (FETs) demonstrate that the Si/Al2O3 core/shell nanowire FETs exhibit good device performance for at least 4 months in physiological model solutions at 37 °C. The generality of this approach was also tested with in studies of Ge/Si and InAs nanowires, where Ge/Si/Al2O3 and InAs/Al2O3 core/shell materials exhibited stability for at least 100 days in physiological model solutions at 37 °C. In addition, investigations of hafnium oxide-Al2O3 nanolaminated shells indicate the potential to extend nanowire stability well beyond 1 year time scale in vivo. These studies demonstrate that straightforward core/shell nanowire nanoelectronic devices can exhibit the long term stability needed for a range of chronic in vivo studies in animals as well as powerful biomedical implants that could improve monitoring and treatment of disease.

Stability problems for linear hyperbolic systems

International Nuclear Information System (INIS)

Eckhoff, K.S.

1975-05-01

The stability properties for the trivial solution of a general linear hyperbolic system of partial differential equations of the first order are studied. It is shown that results may be obtained by studying the stability properties of certain systems of ordinary differential equations which can be constructed from the hyperbolic system (the so-called transport equations). In some cases the associated stability problem for the transport equations can in fact be shown to be equivalent to the stability problem for the hyperbolic system, but in general the transport equations will only give the necessary conditions for stability. (Auth.)

A study to assess the long-term stability of the ionization chamber reference system in the LNMRI

Science.gov (United States)

Trindade Filho, O. L.; Conceição, D. A.; da Silva, C. J.; Delgado, J. U.; de Oliveira, A. E.; Iwahara, A.; Tauhata, L.

2018-03-01

Ionization chambers are used as secondary standard in order to maintain the calibration factors of radionuclides in the activity measurements in metrology laboratories. Used as radionuclide calibrator in nuclear medicine clinics to control dose in patients, its long-term performance is not evaluated systematically. A methodology for long-term evaluation for its stability is monitored and checked. Historical data produced monthly of 2012 until 2017, by an ionization chamber, electrometer and 226Ra, were analyzed via control chart, aiming to follow the long-term performance. Monitoring systematic errors were consistent within the limits of control, demonstrating the quality of measurements in compliance with ISO17025.

A study to assess the long-term stability of the ionization chamber reference system in the LNMRI

Energy Technology Data Exchange (ETDEWEB)

Filho, Octavio L.T.; Conceição, Dayana A. da; Silva, Carlos J. da; Delgado, José U.; Oliveira, Antônio E. de; Iwahara, Akira; Tauhata, Luiz, E-mail: octavio@ird.gov.br [Instituto de Radioproteção e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2017-07-01

Ionization chambers are used as secondary standard in order to maintain the calibration factors of radionuclides in the activity measurements in metrology laboratories. Used as radionuclide calibrator in nuclear medicine clinics to control dose in patients, its long-term performance is not evaluated systematically. A methodology for long-term evaluation for its stability is monitored and checked. Historical data were analyzed via control chart, produced between 2012-2017 by an ionization chamber, electrometer and {sup 226}Ra, aiming to follow the long-term performance. The results for monitoring systematic errors were consistent within the limits of control, demonstrating the quality of measurements in compliance with ISO17025. (author)

Mean Square Exponential Stability of Stochastic Switched System with Interval Time-Varying Delays

Directory of Open Access Journals (Sweden)

Manlika Rajchakit

2012-01-01

Full Text Available This paper is concerned with mean square exponential stability of switched stochastic system with interval time-varying delays. The time delay is any continuous function belonging to a given interval, but not necessary to be differentiable. By constructing a suitable augmented Lyapunov-Krasovskii functional combined with Leibniz-Newton’s formula, a switching rule for the mean square exponential stability of switched stochastic system with interval time-varying delays and new delay-dependent sufficient conditions for the mean square exponential stability of the switched stochastic system are first established in terms of LMIs. Numerical example is given to show the effectiveness of the obtained result.

Stability considerations of packed multi-planet systems

Science.gov (United States)

Gratia, Pierre; Lissauer, Jack

2018-04-01

I will present our first results of the outcomes of five packed, Earth-mass planetary simulations around a Sun-like star, whose initial separations in terms of their semi-major axes is determined by a multiple of their mutual Hill radius, the parameter beta. In our simulations, we will vary beta between 3.5 and and 9, with a special emphasis on the region around 8.5, where stability times are wildly different for small increments of beta. While the zero initial eccentricity case has been investigated before, we expand on it by allowing for initial nonzero eccentricities of one or more planets. Furthermore, we increase the simulated time by up to one order of magnitude reaching billions of orbits. This of course will determine more accurately the fate of systems that take a long time to go unstable. Both of these investigations have not been done before, thus our findings improve our understanding of the stabilities of closely-spaced planetary systems.

Ceramics in engines - Long term stability of transformation toughened zirconia

International Nuclear Information System (INIS)

Marmach, M.; Swain, M.V.

1985-01-01

The long term thermal stability of two types of magnesia partially stabilized zirconia at temperatures below 1000 0 C has been determined. The effect on mechanical properties and phase stability of isothermal heating at 800 0 C and 900 0 C for up to 2000 hours, and with thermal cycling for a similar period between R.T. and 800 0 C in air, was measured. it was found that peak-aged (MS) type Mg-PSZ was much more stable than the thermal shock resistant (TS) type in both tests and showed minimal degradation

Evaluation of long-term mechanical stability of near field

International Nuclear Information System (INIS)

Takaji, Kazuhiko; Sugino, Hiroyuki; Okutsu, Kazuo; Miura, Kazuhiko; Tabei, Kazuto; Noda, Masaru; Takahashi, Shinichi; Sugie, Shigehiko

1999-11-01

In the near field, as tunnels and pits are excavated, a redistribution of stresses in the surrounding rock will occur. For a long period of time after the emplacement of waste packages various events will take place, such as the swelling of the buffer, sinking of the overpack under its own weight, deformation arising from expansion of overpack corrosion products and the creep deformation of the rock mass. The evaluation of what effects these changes in the stress-state will have on the buffer and rock mass is a major issue from the viewpoint of safety assessment. Therefore, rock creep analysis, overpack corrosion expansion analysis and overpack sinking analysis have been made in order to examine the long-term mechanical stability of the near field and the interaction of various events that may affect the stability of the near field over a long period of time. As the results, rock creep behavior, the variations of the stress-state and the range of the influence zone differ from the rock strength, strength of buffer in the tunnel and side pressure coefficient etc. about the hard rock system and soft rock system established as basic cases. And the magnitude of the stress variations for buffer by the overpack sinking and rock creep deformation is negligible compared with it by the overpack corrosion expansion. Furthermore, though very limited zone of buffer around the overpack is close to the critical state by the overpack corrosion expansion, the engineered barrier system attains a comparatively stable state for a long period of time. (author)

Long-term stability and properties of zirconia ceramics for heavy duty diesel engine components

Science.gov (United States)

Larsen, D. C.; Adams, J. W.

1985-01-01

Physical, mechanical, and thermal properties of commercially available transformation-toughened zirconia are measured. Behavior is related to the material microstructure and phase assemblage. The stability of the materials is assessed after long-term exposure appropriate for diesel engine application. Properties measured included flexure strength, elastic modulus, fracture toughness, creep, thermal shock, thermal expansion, internal friction, and thermal diffusivity. Stability is assessed by measuring the residual property after 1000 hr/1000C static exposure. Additionally static fatigue and thermal fatigue testing is performed. Both yttria-stabilized and magnesia-stabilized materials are compared and contrasted. The major limitations of these materials are short term loss of properties with increasing temperature as the metastable tetragonal phase becomes more stable. Fine grain yttria-stabilized material (TZP) is higher strength and has a more stable microstructure with respect to overaging phenomena. The long-term limitation of Y-TZP is excessive creep deformation. Magnesia-stabilized PSZ has relatively poor stability at elevated temperature. Overaging, decomposition, and/or destabilization effects are observed. The major limitation of Mg-PSZ is controlling unwanted phase changes at elevated temperature.

New stability and stabilization for switched neutral control systems

International Nuclear Information System (INIS)

Xiong Lianglin; Zhong Shouming; Ye Mao; Wu Shiliang

2009-01-01

This paper concerns stability and stabilization issues for switched neutral systems and presents new classes of piecewise Lyapunov functionals and multiple Lyapunov functionals, based on which, two new switching rules are introduced to stabilize the neutral systems. One switching rule is designed from the solution of the so-called Lyapunov-Metzler linear matrix inequalities. The other is based on the determination of average dwell time computed from a new class of linear matrix inequalities (LMIs). And then, state-feedback control is derived for the switched neutral control system mainly based on the state switching rules. Finally, three examples are given to demonstrate the effectiveness of the proposed method.

The long-term hydrological effect of forest stands on the stability of slopes

Science.gov (United States)

Bogaard, T. A.; Meng, W.; van Beek, L. P. H.

2012-04-01

Forest is widely known to improve slope stability as a result of mechanical and hydrological effects. While the mechanics underlying the stabilizing process of root reinforcement are well understood and quantified, the influence of forest on the occurrence of critical hydrological conditions in terms of suction or pore pressure remains uncertain. Due to seasonal and inter-annual fluctuations, the stabilizing influence of evaporation and transpiration is difficult to isolate from the overall noise of the hydrological signal. More long-term effects of forest stands on soil development are highly variable and thus difficult to observe and quantify. Often these effects are ambivalent, having potentially a stabilizing or destabilizing influence on a slope under particular conditions (e.g., more structured soils leading to both rapid infiltration and drainage). Consequently, it can be postulated that forests will hydrologically influence the magnitude-frequency distribution of landsliding, not only at the stand level but also on a regional scale through the groundwater system. The overall aim of this research is to understand and quantify the stabilizing hydrological effect of forests on potentially unstable slopes. To this end, we focus on the changes in the magnitude-frequency distribution of landsliding that arise as a result of variations in evapotranspiration losses over the life cycle of stands. Temporal variations in evapotranspiration comprise first of all the interception that can account for an important amount of evaporation from a forest, and that changes with seasonal and annual variations in the interception capacity of the canopy and forest floor. Transpiration also represents an important loss that varies over the various growth stages of a forest stand. Based on a literature review of water consumption by tree species and water balance studies of forested catchments we defined the potential transpiration for different growth stages. This information we

Long-term stability investigation of o/w cosmetic creams stabilized by mixed emulsifier

Directory of Open Access Journals (Sweden)

Đekić Ljiljana M.

2012-01-01

Full Text Available Polyglyceryl-3 Methylglucose Distearate (PMD, TEGO® Care 450, Evonik, Germanyis natural (vegetable, non-ionic, PEG-free emulsifier, suitable for the formulation of oil-in-water (o/w cosmetic creams and lotions. The oil phase components can be selected from mineral oils, vegetable oils and synthetic esters, which enable different variety of application profile of these emulsions. It is possible to prepare stable emulsions using low-level concentration of the PMD (2-3% if lotions contain 10-25%, and creams 20-40 % of oil phase. PMD forms liquid crystal structure in the presence of stearic acid, glyceryl stearate, fatty alcohols, or their combinations. The o/w type creams, stabilized by these mixed emulsifiers are complex, multiphase systems. The aim of this work was to formulate, prepare and investigate long-term stability of the o/w creams stabilized by mixed emulsifier polyglyceryl-3 methylglucose distearate/glyceryl stearate/stearyl alcohol, depending on concentration levels of PMD (2% or 3% and oil:water phase ratio (20:80 and 30:70. The samples were prepared using hot/hot procedure. Organoleptic inspection, centrifugation test, rheological measurements, electric conductivity and pH value measurements were performed 72 h, 1, 3, 12 and 30 months after preparation. The prepared samples were apparently white and homogenous creams. The consistency and homogeneity were preserved after centrifugation of the creams after 72 h, 1, 3, 12 and 30 months storage, and no phase separation could be detected. The pH values obtained are suitable for skin application. Conductivity values (25.2-63.7 μS cm1, 72 h after preparation were attributed to the multiple phase o/w emulsions with high percentages of fixed water. Results of the rheological measurements have shown that the investigated creams exhibited non-Newtonian thyxotropic behavior. The concentration of emulsifier PMD and oil phase content had an influence on the rheological parameters of investigated

Long-term stability of the Leksell Gamma Knife® Perfexion™ patient positioning system (PPS)

International Nuclear Information System (INIS)

Novotny, J.; Bhatnagar, J. P.; Xu, Y.; Huq, M. S.

2014-01-01

Purpose: To assess the long-term mechanical stability and accuracy of the patient positioning system (PPS) of the Leksell Gamma Knife ® Perfexion™ (LGK PFX). Methods: The mechanical stability of the PPS of the LGK PFX was evaluated using measurements obtained between September 2007 and June 2011. Three methods were employed to measure the deviation of the coincidence of the radiological focus point (RFP) and the PPS calibration center point (CCP). In the first method, the onsite diode test tool with single diode detector was used together with the 4 mm collimator on a daily basis. In the second method, a service diode test tool with three diode detectors was used biannually at the time of the routine preventive maintenance. The test performed with the service diode test tool measured the deviations for all three collimators 4, 8, and 16 mm and also for three different positions of the PPS. The third method employed the conventional film pin-prick method. This test was performed annually for the 4 mm collimator at the time of the routine annual QA. To estimate the effect of the patient weight on the performance of the PPS, the focus precision tests were also conducted with varying weights on the PPS using a set of lead bricks. Results: The average deviations measured from the 641 daily focus precision tests were 0.1 ± 0.1, 0.0 ± 0.0, and 0.0 ± 0.0 mm, respectively, for the 4 mm collimator in the X (left/right of the patient), Y (anterior/posterior of the patient), and Z (superior/inferior of the patient) directions. The average of the total radial deviations as measured during ten semiannual measurements with the service diode test tool were 0.070 ± 0.029, 0.060 ± 0.022, and 0.103 ± 0.028 mm, respectively for the central, long, and short diodes for the 4 mm collimator. Similarly, the average total radial deviations measured during the semiannual measurements for the 4, 8, and 16 mm collimators and using the central diode were 0.070 ± 0.029, 0.097 ± 0

Long-term stability of high-level waste forms

International Nuclear Information System (INIS)

Vernaz, E.; Loida, A.; Malow, G.; Marples, J.A.C.; Matzke, H.J.

1990-01-01

The long-term stability of HLW forms is reviewed with regard to temperature, irradiation and aqueous corrosion in a geological environment. The paper focuses on borosilicate glasses, but the radiation stability results are compared with some HLW ceramics. Thermal stability: most nuclear waste glass compositions have been adjusted to ensure a low final crystallized fraction. The crystallization of highly active Pamela glass samples was similar to that of nonradioactive glass. Radiation stability: No adverse effect of irradiation damage was found in glasses doped with short-lived actinides: volume changes were small, no significant change in the leach rate was observed, and the fracture toughness increased. For most ceramics investigated, volume changes of up to 9%, amorphization and higher leach rates were observed as a consequence of high α decay doses. For the KAB 78 ceramic, however, none of these effects were detected since the matrix was not subject to α recoil damage. Chemical stability: It has been demonstrated that alteration by water depends largely on the repository conditions. Most clay act as silica sinks, and increase the glass corrosion rate. It is possible, however, to specify realistic temperature, pressure and environmental conditions to ensure glass integrity for more than 10 000 years

Identification of long-term containment/stabilization technology performance issues

International Nuclear Information System (INIS)

Matthern, G.E.; Nickelson, D.F.

1997-01-01

U.S. Department of Energy (DOE) faces a somewhat unique challenge when addressing in situ remedial alternatives that leave long-lived radionuclides and hazardous contaminants onsite. These contaminants will remain a potential hazard for thousands of years. However, the risks, costs, and uncertainties associated with removal and offsite disposal are leading many sites to select in situ disposal alternatives. Improvements in containment, stabilization, and monitoring technologies will enhance the viability of such alternatives for implementation. DOE's Office of Science and Technology sponsored a two day workshop designed to investigate issues associated with the long-term in situ stabilization and containment of buried, long-lived hazardous and radioactive contaminants. The workshop facilitated communication among end users representing most sites within the DOE, regulators, and technologists to define long-term performance issues for in situ stabilization and containment alternatives. Participants were divided into groups to identify issues and a strategy to address priority issues. This paper presents the results of the working groups and summarizes the conclusions. A common issue identified by the work groups is communication. Effective communication between technologists, risk assessors, end users, regulators, and other stakeholders would contribute greatly to resolution of both technical and programmatic issues

Stability of dynamical systems

CERN Document Server

Liao, Xiaoxin; Yu, P 0

2007-01-01

The main purpose of developing stability theory is to examine dynamic responses of a system to disturbances as the time approaches infinity. It has been and still is the object of intense investigations due to its intrinsic interest and its relevance to all practical systems in engineering, finance, natural science and social science. This monograph provides some state-of-the-art expositions of major advances in fundamental stability theories and methods for dynamic systems of ODE and DDE types and in limit cycle, normal form and Hopf bifurcation control of nonlinear dynamic systems.ʺ Presents

Long term stability of yttria-stabilized zirconia waste forms. Stability for secular change of partitioned TRU waste composition by disintegration

International Nuclear Information System (INIS)

Kuramoto, Ken-ichi; Banba, Tsunetaka; Mitamura, Hisayoshi; Sakai, Etsuro; Uno, Masayoshi; Kinoshita, H.; Yamanaka, Shinsuke

1999-01-01

In this study, the stability of YSZ waste forms for secular change of partitioned TRU waste composition by disintegration, one of important terms in long-term stability, is the special concern. Designed amount of waste and YSZ powder were mixed and sintered. These TRU waste forms were submitted to tests of phase stability, chemical durability, mechanical property and compactness. The results were compared with those of another YSZ waste forms, non-radioactive Ce and/or Nd doped YSZ samples, and glass and Synroc waste forms. Experimental results show following: (1) Phase stability of (Np+Am)-, (Np+U)-, and (Np+U+Bi)-doped YSZ waste forms could be maintained of that of the initial Np+Am-doped YSZ waste form permanently even when the composition of partitioned TRU waste were changed by disintegration. (2) Secular change also accelerated volume increase of YSZ waste forms as well as alpha-decay damage. (3) Hv, E and K IC of (Np+U)- and (Np+U+Bi)-doped YSZ waste forms were independent of the secular change of the partitioned TRU waste composition by disintegration. (4) Mechanical properties of YSZ waste forms were more than those of a glass and Synroc waste forms. (5) Compactness of YSZ waste forms was good as waste forms for the partitioned TRU wastes. (J.P.N.)

Stability in dynamical systems I

International Nuclear Information System (INIS)

Courant, E.D.; Ruth, R.D.; Weng, W.T.

1984-08-01

We have reviewed some of the basic techniques which can be used to analyze stability in nonlinear dynamical systems, particularly in circular particle accelerators. We have concentrated on one-dimensional systems in the examples in order to simply illustrate the general techniques. We began with a review of Hamiltonian dynamics and canonical transformations. We then reviewed linear equations with periodic coefficients using the basic techniques from accelerator theory. To handle nonlinear terms we developed a canonical perturbation theory. From this we calculated invariants and the amplitude dependence of the frequency. This led us to resonances. We studied the cubic resonance in detail by using a rotating coordinate system in phase space. We then considered a general isolated nonlinear resonance. In this case we calculated the width of the resonance and estimated the spacing of resonances in order to use the Chirikov criterion to restrict the validity of the analysis. Finally the resonance equation was reduced to the pendulum equation, and we examined the motion on a separatrix. This brought us to the beginnings of stochastic behavior in the neighborhood of the separatrix. It is this complex behavior in the neighborhood of the separatrix which causes the perturbation theory used here to diverge in many cases. In spite of this the methods developed here have been and are used quite successfully to study nonlinear effects in nearly integrable systems. When used with caution and in conjunction with numerical work they give tremendous insight into the nature of the phase space structure and the stability of nonlinear differential equations. 14 references

Research on geosphere stability for long-term isolation of radioactive waste. Scientific programme for fiscal years 2010-2014

International Nuclear Information System (INIS)

Umeda, Koji; Ishimaru, Tsuneari; Yasue, Ken-ichi; Asamori, Koichi; Yamada, Kunimi; Saito-Kokubu, Yoko; Hanamuro, Takahiro; Tanikawa, Shin-ichi; Kusano, Tomohiro

2010-09-01

The concept of geological disposal of HLW in Japan is based on a multibarrier system which combines a stable geological environment with an engineered barrier system. Potential geological host formations and their surroundings are chosen, in particular, for their long-term stability, taking into account the fact that Japan is located in a tectonically active zone. This report is to outline 5 years plan (fiscal years 2010-2014) of research and development (R and D) for geosphere stability for long-term isolation of the high-level radioactive waste in JAEA. Background of this research are clarified with the necessity and the significance, and the past progresses in this report. The objectives, outline, contents and schedule during the next 5 years are described in detail. In addition, the plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. (author)

Methodologies for evaluating long-term stabilization designs of uranium mill tailings impoundments

International Nuclear Information System (INIS)

Nelson, J.D.; Abt, S.R.; Volpe, R.L.; Van Zye, D.; Hinkle, N.E.; Staub, W.P.

1986-06-01

Uranium mill tailings impoundments require long-term (200 to 1000 years) stabilization. This report reviews currently available methodologies for evaluating factors that can have a significant influence on tailings stabilization and develops methodologies in technical areas where none presently exist. Mill operators can use these methodologies to assist with (1) the selection of sites for mill tailings impoundments, (2) the design of stable impoundments, and (3) the development of reclamation plans for existing impoundments. These methodologies would also be useful for regulatory agency evaluations of proposals in permit or license applications. Methodologies were reviewed or developed in the following technical areas: (1) prediction of the Probable Maximum Precipitation (PMP) and an accompanying Probable Maximum Flood (PMF); (2) prediction of the stability of local and regional fluvial systems; (3) design of impoundment surfaces resistant to gully erosion; (4) evaluation of the potential for surface sheet erosion; (5) design of riprap for protecting embankments from channel flood flow and overland flow; (6) selection of riprap with appropriate durability for its intended use; and (7) evaluation of oversizing required for marginal quality riprap

Dynamic Stability of Maglev Systems,

Science.gov (United States)

1992-04-01

AD-A259 178 ANL-92/21 Materials and Components Dynamic Stability of Technology Division Materials and Components Maglev Systems Technology Division...of Maglev Systems Y. Cai, S. S. Chen, and T. M. Mulcahy Materials and Components Technology Division D. M. Rote Center for Transportation Research...of Maglev System with L-Shaped Guideway ......................................... 6 3 Stability of M aglev System s

Short term outcome of posterior dynamic stabilization system in degenerative lumbar diseases.

Science.gov (United States)

Yang, Mingyuan; Li, Chao; Chen, Ziqiang; Bai, Yushu; Li, Ming

2014-11-01

Decompression and fusion is considered as the 'gold standard' for the treatment of degenerative lumbar diseases, however, many disadvantages have been reported in several studies, recently like donor site pain, pseudoarthrosis, nonunion, screw loosening, instrumentation failure, infection, adjacent segment disease (ASDis) and degeneration. Dynamic neutralization system (Dynesys) avoids many of these disadvantages. This system is made up of pedicle screws, polyethylene terephthalate cords, and polycarbonate urethane spacers to stabilize the functional spinal unit and preserve the adjacent motion after surgeries. This was a retrospective cohort study to compare the effect of Dynesys for treating degenerative lumbar diseases with posterior lumbar interbody fusion (PLIF) based on short term followup. Seventy five consecutive patients of lumbar degenerative disease operated between October 2010 and November 2012 were studied with a minimum followup of 2 years. Patients were divided into two groups according to the different surgeries. 30 patients underwent decompression and implantation of Dynesys in two levels (n = 29) or three levels (n = 1) and 45 patients underwent PLIF in two levels (n = 39) or three levels (n = 6). Clinical and radiographic outcomes between two groups were reviewed. Thirty patients (male:17, female:13) with a mean age of 55.96 ± 7.68 years were included in Dynesys group and the PLIF group included 45 patients (male:21, female:24) with a mean age of 54.69 ± 3.26 years. The average followup in Dynesys group and PLIF group was 2.22 ± 0.43 year (range 2-3.5 year) and 2.17 ± 0.76 year (range 2-3 year), respectively. Dynesys group showed a shorter operation time (141.06 ± 11.36 min vs. 176.98 ± 6.72 min, P degenerative disease showed clinical benefits with motion preservation of the operated segments, but does not have the significant advantage on motion preservation at adjacent segments, to avoid the degeneration of adjacent intervertebral disk.

Long-Term Stability Evaluation and Pillar Design Criterion for Room-and-Pillar Mines

Directory of Open Access Journals (Sweden)

Yang Yu

2017-10-01

Full Text Available The collapse of abandoned room-and-pillar mines is often violent and unpredictable. Safety concerns often resulted in mine closures with no post-mining stability evaluations. As a result, large amounts of land resources over room-and-pillar mines are wasted. This paper attempts to establish an understanding of the long-term stability issues of goafs (abandoned mines. Considering progressive pillar failures and the effect of single pillar failure on surrounding pillars, this paper proposes a pillar peeling model to evaluate the long-term stability of coal mines and the associated criteria for evaluating the long-term stability of room-and-pillar mines. The validity of the peeling model was verified by numerical simulation, and field data from 500 pillar cases from China, South Africa, and India. It is found that the damage level of pillar peeling is affected by the peel angle and pillar height and is controlled by the pillar width–height ratio.

Long-term Stabilization of Disturbed Slopes Resulting from Construction Operations

Science.gov (United States)

2018-01-01

Highway construction disturbs soil, which must be stabilized to prevent migration of soil particles into water bodies. Stabilization is enforced by law, regulation, and a permit system. Stabilization is most efficiently attained by reestablishment of...

Modelling, stability and control of voltage behaviour in power supply systems

Energy Technology Data Exchange (ETDEWEB)

Hill, David J [Sydney Univ., NSW (Australia). Dept. of Electrical Engineering; Hisken, Ian A [Newcastle Univ., NSW (Australia). Dept. of Electrical and Computer Engineering

1994-12-31

This paper gives an overview of a line of work on mid to long term voltages stability analysis and control in power systems. The results are based on use of a novel approach to dynamic load modelling using aggregate nonlinear structures. In general, the model for the transmission network and supply end dynamics is of the hybrid differential - algebraic - discrete kind. Various stability questions are precisely formulated and analysed in terms of network and load characteristics (steady-state and transient). The results are shown to be a useful framework for deriving criteria of the where, when and how much kind for various control actions such as load Thedding and tap-blocking. (author) 47 refs., 15 figs., 1 tab.

Long-term stability of surfactant-free gold nanostars

Science.gov (United States)

Vega, Marienette Morales; Bonifacio, Alois; Lughi, Vanni; Marsi, Stefano; Carrato, Sergio; Sergo, Valter

2014-11-01

This work investigates the long-term stability of suspensions of surfactant-free gold nanostars with mean diameter of 78 ± 13 nm (measured from tip to tip across the nanostar).We monitored the optical and morphological properties of the nanostars over the course of several days after synthesis by observing the changes in the UV-visible absorption spectra and mean radius of curvature of the nanostar tips. An aging process can be observed, evident in the blunting of the nanostar tips, leading to a blue shift in the absorption maximum. Stability is greatly improved by depositing on the nanostars a monolayer of mercaptopropionic acid (MPA), possibly because of the formation of the gold-sulfur (Au-S) bond that limits the mobility of the Au atoms. Capping the nanostars with MPA is an easy additional step for extending the stability of the nanostars in suspension without significantly affecting the original plasmonic resonance band.

Fast simulation of wind generation for frequency stability analysis in island power systems

Energy Technology Data Exchange (ETDEWEB)

Conroy, James [EirGrid, Dublin (Ireland)

2010-07-01

Frequency stability is a major issue for power system planning and operation in an island power system such as Ireland. As increasing amounts of variable speed wind generation are added to the system, this issue becomes more prominent, as variable speed wind generation does not provide an inherent inertial response. This lack of an inertial response means that simplified models for variable speed wind farms can be used for investigating frequency stability. EirGrid uses DIgSILENT Power Factory (as well as other software tools) to investigate frequency stability. In PowerFactory, an automation program has been created to convert detailed wind farm representation (as necessary for other types of analysis) to negative load models for frequency stability analysis. The advantage of this approach is much-improved simulation speed without loss of accuracy. This approach can also be to study future wind energy targets, and long-term simulation of voltage stability. (orig.)

A novel high pressure, high temperature vessel used to conduct long-term stability measurements of silicon MEMS pressure transducers

Science.gov (United States)

Wisniewiski, David

2014-03-01

The need to quantify and to improve long-term stability of pressure transducers is a persistent requirement from the aerospace sector. Specifically, the incorporation of real-time pressure monitoring in aircraft landing gear, as exemplified in Tire Pressure Monitoring Systems (TPMS), has placed greater demand on the pressure transducer for improved performance and increased reliability which is manifested in low lifecycle cost and minimal maintenance downtime through fuel savings and increased life of the tire. Piezoresistive (PR) silicon MEMS pressure transducers are the primary choice as a transduction method for this measurement owing to their ability to be designed for the harsh environment seen in aircraft landing gear. However, these pressure transducers are only as valuable as the long-term stability they possess to ensure reliable, real-time monitoring over tens of years. The "heart" of the pressure transducer is the silicon MEMS element, and it is at this basic level where the long-term stability is established and needs to be quantified. A novel High Pressure, High Temperature (HPHT) vessel has been designed and constructed to facilitate this critical measurement of the silicon MEMS element directly through a process of mechanically "floating" the silicon MEMS element while being subjected to the extreme environments of pressure and temperature, simultaneously. Furthermore, the HPHT vessel is scalable to permit up to fifty specimens to be tested at one time to provide a statistically significant data population on which to draw reasonable conclusions on long-term stability. With the knowledge gained on the silicon MEMS element, higher level assembly to the pressure transducer envelope package can also be quantified as to the build-effects contribution to long-term stability in the same HPHT vessel due to its accommodating size. Accordingly, a HPHT vessel offering multiple levels of configurability and robustness in data measurement is presented, along

Asymptotic stability of discrete-time systems with time-varying delay subject to saturation nonlinearities

International Nuclear Information System (INIS)

Chen, S.-F.

2009-01-01

The asymptotic stability problem for discrete-time systems with time-varying delay subject to saturation nonlinearities is addressed in this paper. In terms of linear matrix inequalities (LMIs), a delay-dependent sufficient condition is derived to ensure the asymptotic stability. A numerical example is given to demonstrate the theoretical results.

System identification on two-phase flow stability

International Nuclear Information System (INIS)

Wu Shaorong; Zhang Youjie; Wang Dazhong; Bo Jinghai; Wang Fei

1996-01-01

The theoretical principle, experimental method and results of interrelation analysis identification for the instability of two-phase flow are described. A completely new concept of test technology and method on two-phase flow stability was developed by using he theory of information science on system stability and system identification for two-phase flow stability in thermo-physics field. Application of this method would make it possible to identify instability boundary of two-phase flow under stable operation conditions of two-phase flow system. The experiment was carried out on the thermohydraulic test system HRTL-5. Using reverse repeated pseudo-random sequences of heating power as input signal sources and flow rate as response function in the test, the two-phase flow stability and stability margin of the natural circulation system are investigated. The effectiveness and feasibility of identifying two-phase flow stability by using this system identification method were experimentally demonstrated. Basic data required for mathematics modeling of two-phase flow and analysis of two-phase flow stability were obtained, which are useful for analyzing, monitoring of the system operation condition, and forecasting of two-phase flow stability in engineering system

Delay-dependent asymptotic stability of mobile ad-hoc networks: A descriptor system approach

International Nuclear Information System (INIS)

Yang Juan; Yang Dan; Zhang Xiao-Hong; Huang Bin; Luo Jian-Lu

2014-01-01

In order to analyze the capacity stability of the time-varying-propagation and delay-dependent of mobile ad-hoc networks (MANETs), in this paper, a novel approach is proposed to explore the capacity asymptotic stability for the delay-dependent of MANETs based on non-cooperative game theory, where the delay-dependent conditions are explicitly taken into consideration. This approach is based on the Lyapunov—Krasovskii stability theory for functional differential equations and the linear matrix inequality (LMI) technique. A corresponding Lyapunov—Krasovskii functional is introduced for the stability analysis of this system with use of the descriptor and “neutral-type” model transformation without producing any additional dynamics. The delay-dependent stability criteria are derived for this system. Conditions are given in terms of linear matrix inequalities, and for the first time referred to neutral systems with the time-varying propagation and delay-dependent stability for capacity analysis of MANETs. The proposed criteria are less conservative since they are based on an equivalent model transformation. Furthermore, we also provide an effective and efficient iterative algorithm to solve the constrained stability control model. Simulation experiments have verified the effectiveness and efficiency of our algorithm. (general)

Stability improvement of wind turbine penetrated using power system stabilizer (PSS) on South Sulawesi transmission system

Science.gov (United States)

Siswanto, Agus; Gunadin, Indar Chaerah; Said, Sri Mawar; Suyuti, Ansar

2018-03-01

The purpose of this research is to improve the stability of interconnection of South Sulawesi system caused by penetration new wind turbine in Sidrap area on bus 2 and in Jeniponto area on bus 34. The method used in this research was via software Power System analysis Toolbox (PSAT) under MATLAB. In this research, there are two problems that are evaluated, the stability of the system before and after penetration wind turbine into the system South Sulawesi system. From the simulation result shows that penetration of wind turbine on bus 2 Sidrap, bus 37 Jeniponto give effect oscillation on the system. The oscillation was damped by installation of Power System Stabilizer (PSS) on bus 29 area Sungguminasa, that South Sulawesi system stable according to normal condition.

Stability analysis of impulsive fuzzy cellular neural networks with distributed delays and reaction-diffusion terms

International Nuclear Information System (INIS)

Li Zuoan; Li Kelin

2009-01-01

In this paper, we investigate a class of impulsive fuzzy cellular neural networks with distributed delays and reaction-diffusion terms. By employing the delay differential inequality with impulsive initial conditions and M-matrix theory, we find some sufficient conditions ensuring the existence, uniqueness and global exponential stability of equilibrium point for impulsive fuzzy cellular neural networks with distributed delays and reaction-diffusion terms. In particular, the estimate of the exponential converging index is also provided, which depends on the system parameters. An example is given to show the effectiveness of the results obtained here.

Plutonium stabilization and packaging system

International Nuclear Information System (INIS)

1996-01-01

This document describes the functional design of the Plutonium Stabilization and Packaging System (Pu SPS). The objective of this system is to stabilize and package plutonium metals and oxides of greater than 50% wt, as well as other selected isotopes, in accordance with the requirements of the DOE standard for safe storage of these materials for 50 years. This system will support completion of stabilization and packaging campaigns of the inventory at a number of affected sites before the year 2002. The package will be standard for all sites and will provide a minimum of two uncontaminated, organics free confinement barriers for the packaged material

Probabilistic stability analysis: the way forward for stability analysis of sustainable power systems.

Science.gov (United States)

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).

Impacts of Wind Power on Power System Stability

NARCIS (Netherlands)

Vittal, E.; Keane, A.; Slootweg, J.G.; Kling, W.L.; Ackermann, T.

2012-01-01

This chapter examines how wind power will impact the stability of power systems. It focuses on the three aspects of power system stability: voltage stability, rotor angle stability and frequency stability. It completes a detailed analysis as to how wind power in power systems will impact the

Investigation and technical reviews on the long term stability of buffer. Document prepared by other institute, based on the contract

International Nuclear Information System (INIS)

Takasu, Aki

2003-03-01

The main objectives of future research and development of geological disposal are to confirm that previous investigation and assessment method which have been arranged for generic geological environment will apply to real geological disposal environment, and the margin of system performance, which was assessed under simple and conservative viewpoint in the past, with assessment and recognition long term behavior of realistic system. Under present condition, we organized clay science specialist committee in Nuclear Safety Research Association and considered following themes comprehensively. To confirm the assessment methods for log term stability of the buffer in H12: Project to establish the scientific and technical basis for HLW disposal in Japan' and in other performance assessment reports, and to pick up subjects from them. Review on the research for long term stability assessment in Japan Nuclear Cycle Development Institute and in other researchers. This report is summarized the result of investigation. (author)

Limitations and possibilities of green synthesis and long-term stability of colloidal Ag nanoparticles

Science.gov (United States)

Velgosová, Oksana; Mražíková, Anna

2017-12-01

In this paper the influence of algae life cycle and the solutions pH on the green synthesis of colloidal Ag nanoparticles (AgNPs) as well as effect of different storage conditions on AgNPs long-term stability was investigated. Silver nanoparticles were biologically synthesized using extracts of Parachlorella kessleri algae cultivated 1, 2, 3 and 4 weeks. The formation of AgNPs was monitored using a UV-vis spectrophotometer and verified by TEM observation. The results confirmed formation of polyhedron and/or near polyhedron AgNPs, ranging between 5 and 60 nm in diameter. The age of algae influenced the synthesis rate and an amount of AgNPs in solution. The best results were obtained using tree weeks old algae. UV-vis analysis and TEM observation also revealed that the size and the stability of AgNPs depend on the pH of solution. AgNPs formed in solutions of higher pH (8 and 10) are polyhedron, fine, with narrow size interval and stabile. Nanoparticles formed in solutions of low pH (2, 4 and 6) started to lose their stability on 10th day of experiment, and the particle size interval was wide. The long-term stability of AgNPs can be influenced by light and temperature conditions. The most significant stability loss was observed at day light and room temperature (21°C). After 200-days significant amount of agglomerated particles settled on the bottom of the Erlenmeyer flask. AgNPs stored at dark and room temperature showed better long-term stability, weak particles agglomeration was observed. AgNPs stored at dark and at temperature 5°C showed the best long-term stability. Such AgNPs remained spherical, fine (5-20 nm), with narrow size interval and stable (no agglomeration) even after more than six months.

Methods for safe and economical design of components of ABS/ABR braking systems in terms of operating stability; Methodik zur sicheren und wirtschaftlichen betriebsfesten Auslegung von Komponenten in ABS/ASR-Bremssystemen

Energy Technology Data Exchange (ETDEWEB)

Bacher-Hoechst, M. [Robert Bosch GmbH, Technisches Zentrum Schwieberdingen (Germany); Sonsino, C.M. [Fraunhofer-Institut fuer Betriebsfestigkeit (LBF), Darmstadt (Germany)

1997-05-01

The combination of hardware-in-the-loop simulators with stress calculation in terms of operating stability at Robert Bosch GmbH, as well as experience gathered at LBF Darmstadt with component in terms of operating stability, result in optimized design of hydraulic units for antilock systems (ABS) and acceleration skid control systems (ASC). Thus, both safety demands and economic demands are met. (orig./AKF) [Deutsch] Die kombinierte Anwendung von Hardware-In-The-Loop-Simulatoren mit betriebsfestigkeitsgerechter Belastungserfassung bei der Robert Bosch GmbH und die beim LBF Darmstadt vorliegenden Erfahrungen bei der betriebsfesten Bauteilauslegung fuehren zu einer optimierten Auslegung und Absicherung von Hydraulikaggregaten fuer Antiblockier- und Antriebsschlupfregelungssyteme (ABS,ASR). Die wesentlichen Schritte dieses Vorgehens wurden gezeigt. Auf diese Weise ist es moeglich, den Sicherheitsanforderungen derartiger Bauteile einerseits und den wirtschaftlich-technischen Rahmenbedingungen andererseits zu entsprechen. (orig./AKF)

Stability of periodic steady-state solutions to a non-isentropic Euler-Poisson system

Science.gov (United States)

Liu, Cunming; Peng, Yue-Jun

2017-06-01

We study the stability of periodic smooth solutions near non-constant steady-states for a non-isentropic Euler-Poisson system without temperature damping term. The system arises in the theory of semiconductors for which the doping profile is a given smooth function. In this stability problem, there are no special restrictions on the size of the doping profile, but only on the size of the perturbation. We prove that small perturbations of periodic steady-states are exponentially stable for large time. For this purpose, we introduce new variables and choose a non-diagonal symmetrizer of the full Euler equations to recover dissipation estimates. This also allows to make the proof of the stability result very simple and concise.

New delay-dependent absolute stability criteria for Lur'e systems with time-varying delay

Science.gov (United States)

Chen, Yonggang; Bi, Weiping; Li, Wenlin

2011-07-01

In this article, the absolute stability problem is investigated for Lur'e systems with time-varying delay and sector-bounded nonlinearity. By employing the delay fractioning idea, the new augmented Lyapunov functional is first constructed. Then, by introducing some slack matrices and by reserving the useful term when estimating the upper bound of the derivative of Lyapunov functional, the new delay-dependent absolute stability criteria are derived in terms of linear matrix inequalities. Several numerical examples are presented to show the effectiveness and the less conservativeness of the proposed method.

Stabilizing intermediate-term medium-range earthquake predictions

International Nuclear Information System (INIS)

Kossobokov, V.G.; Romashkova, L.L.; Panza, G.F.; Peresan, A.

2001-12-01

A new scheme for the application of the intermediate-term medium-range earthquake prediction algorithm M8 is proposed. The scheme accounts for the natural distribution of seismic activity, eliminates the subjectivity in the positioning of the areas of investigation and provides additional stability of the predictions with respect to the original variant. According to the retroactive testing in Italy and adjacent regions, this improvement is achieved without any significant change of the alarm volume in comparison with the results published so far. (author)

Examining the long-term stability of overgeneral autobiographical memory.

Science.gov (United States)

Sumner, Jennifer A; Mineka, Susan; Zinbarg, Richard E; Craske, Michelle G; Vrshek-Schallhorn, Suzanne; Epstein, Alyssa

2014-01-01

Overgeneral autobiographical memory (OGM) is a proposed trait-marker for vulnerability to depression, but relatively little work has examined its long-term stability. This study investigated the stability of OGM over several years in 271 late adolescents and young adults participating in a larger longitudinal study of risk for emotional disorders. The Autobiographical Memory Test (AMT) was administered twice, with test-retest intervals ranging from approximately 3 to 6 years. There was evidence of significant but modest stability in OGM over several years. Specifically, Spearman rank correlations (ρs) between the proportions of specific and categoric memories generated on the two AMTs were .31 and .32, respectively. We did not find evidence that the stability of OGM was moderated by the length of the test-retest interval. Furthermore, the stability coefficients for OGM for individuals with and without a lifetime history of major depressive disorder (MDD) were relatively similar in magnitude and not significantly different from one another (ρs=.34 and .42 for the proportions of specific and categoric memories for those with a history of MDD; ρs=.31 for both the proportions of specific and categoric memories for those without a history of MDD). Implications for the conceptualisation of OGM are discussed.

Evaluation of the Long-Term Stability and Temperature Coefficient of Dew-Point Hygrometers

Science.gov (United States)

Benyon, R.; Vicente, T.; Hernández, P.; De Rivas, L.; Conde, F.

2012-09-01

The continuous quest for improved specifications of optical dew-point hygrometers has raised customer expectations on the performance of these devices. In the absence of a long calibration history, users with a limited prior experience in the measurement of humidity, place reliance on manufacturer specifications to estimate long-term stability. While this might be reasonable in the case of measurement of electrical quantities, in humidity it can lead to optimistic estimations of uncertainty. This article reports a study of the long-term stability of some hygrometers and the analysis of their performance as monitored through regular calibration. The results of the investigations provide some typical, realistic uncertainties associated with the long-term stability of instruments used in calibration and testing laboratories. Together, these uncertainties can help in establishing initial contributions in uncertainty budgets, as well as in setting the minimum calibration requirements, based on the evaluation of dominant influence quantities.

Influence of Previous Crop on Durum Wheat Yield and Yield Stability in a Long-term Experiment

Directory of Open Access Journals (Sweden)

Anna Maria Stellacci

2011-02-01

Full Text Available Long-term experiments are leading indicators of sustainability and serve as an early warning system to detect problems that may compromise future productivity. So the stability of yield is an important parameter to be considered when judging the value of a cropping system relative to others. In a long-term rotation experiment set up in 1972 the influence of different crop sequences on the yields and on yield stability of durum wheat (Triticum durum Desf. was studied. The complete field experiment is a split-split plot in a randomized complete block design with two replications; the whole experiment considers three crop sequences: 1 three-year crop rotation: sugar-beet, wheat + catch crop, wheat; 2 one-year crop rotation: wheat + catch crop; 3 wheat continuous crop; the split treatments are two different crop residue managements; the split-split plot treatments are 18 different fertilization formulas. Each phase of every crop rotation occurred every year. In this paper only one crop residue management and only one fertilization treatment have been analized. Wheat crops in different rotations are coded as follows: F1: wheat after sugar-beet in three-year crop rotation; F2: wheat after wheat in three-year crop rotation; Fc+i: wheat in wheat + catch crop rotation; Fc: continuous wheat. The following two variables were analysed: grain yield and hectolitre weight. Repeated measures analyses of variance and stability analyses have been perfomed for the two variables. The stability analysis was conducted using: three variance methods, namely the coefficient of variability of Francis and Kannenberg, the ecovalence index of Wricke and the stability variance index of Shukla; the regression method of Eberhart and Russell; a method, proposed by Piepho, that computes the probability of one system outperforming another system. It has turned out that each of the stability methods used has enriched of information the simple variance analysis. The Piepho�

Global stability results for a generalized Lotka-Volterra system with distributed delays. Applications to predator-prey and to epidemic systems.

Science.gov (United States)

Beretta, E; Capasso, V; Rinaldi, F

1988-01-01

The paper contains an extension of the general ODE system proposed in previous papers by the same authors, to include distributed time delays in the interaction terms. The new system describes a large class of Lotka-Volterra like population models and epidemic models with continuous time delays. Sufficient conditions for the boundedness of solutions and for the global asymptotic stability of nontrivial equilibrium solutions are given. A detailed analysis of the epidemic system is given with respect to the conditions for global stability. For a relevant subclass of these systems an existence criterion for steady states is also given.

Recent Progress in Stability and Stabilization of Systems with Time-Delays

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Magdi S. Mahmoud

2017-01-01

Full Text Available This paper overviews the research investigations pertaining to stability and stabilization of control systems with time-delays. The prime focus is the fundamental results and recent progress in theory and applications. The overview sheds light on the contemporary development on the linear matrix inequality (LMI techniques in deriving both delay-independent and delay-dependent stability results for time-delay systems. Particular emphases will be placed on issues concerned with the conservatism and the computational complexity of the results. Key technical bounding lemmas and slack variable introduction approaches will be presented. The results will be compared and connections of certain delay-dependent stability results are also discussed.

Parenteral emulsions stabilized with a mixture of phospholipids and PEG-660-12-hydroxy-stearate: evaluation of accelerated and long-term stability.

Science.gov (United States)

Jumaa, Muhannad; Müller, Bernd W

2002-09-01

Different emulsion formulations were prepared using phospholipids (Lipoid S57) and PEG-660-12-hydroxy-stearate (Solutol HS15) as single emulsifiers or in mixtures. The accelerated stability after autoclaving, freezing and centrifugation was investigated. The long-term stability was also studied at different temperatures (4, 20, and 37 degrees C) for 8 months. Emulsion stabilized with phospholipids displayed a stable behavior after the autoclaving and centrifugation, but it broke down after the freezing process. In mixture with Solutol HS15, however, the emulsion showed appropriate shelf stability at different temperatures for 8 months. A change in the particle size of the emulsion prepared only with Solutol HS15 was observed after centrifugation (slight) and after autoclaving (marked). In contrast to phospholipid emulsion, this emulsion (with only Solutol HS15) was less prone to breaking down after the freezing, as no complete phase separation was observed. The results obtained using an emulsifier mixture revealed that a combination of an anionic surfactant (phospholipids) and non-ionic surfactant (PEG-660-12-hydroxy-stearate) improves the emulsion's stability, compared to the emulsion's stability prepared using only a single emulsifier. However, no direct correlation could be found between the accelerated and the long-term stability data.

Role of water balance in the long-term stability of hazardous waste site cover treatments

International Nuclear Information System (INIS)

Barnes, F.J.; Rodgers, J.C.; Trujillo, G.

1986-01-01

After the 30-year post-closure maintenance period at hazardous waste landfills, long-term stability must be assured without continued intervention. Understanding water balance in the established vegetative cover system is central to predicting such stability. A Los Alamos National Laboratory research project has established a series of experimental cover treatment plots on a closed waste disposal site which will permit the determination of the effects of such critical parameters as soil cover design, leaf area index, and rooting characteristics on water balance under varied conditions. Data from these experiments are being analyzed by water balance modeling and other means. The results show consistent differences in soil moisture storage between soil profiles and between vegetation cover treatments

Financial stability of banking system in China

OpenAIRE

Jiang, B

2014-01-01

This thesis aims at investigating the financial stability of China's banking system. Since the banking system is one of the most important financial intermediaries in the financial systems, the financial soundness of banks could secure the stability of the whole financial system. Two of the factors that may significantly increase imbalance of the banking system, and hence affect financial stability of an economy is the accumulated non-performing loans of banks and the macro-economic turbulenc...

Long-term performance of aged waste forms treated by stabilization/solidification.

Science.gov (United States)

Antemir, Aurora; Hills, Colin D; Carey, Paula J; Gardner, Kevin H; Bates, Edward R; Crumbie, Alison K

2010-09-15

Current regulatory testing of stabilized/solidified (S/S) soils is based on short-term performance tests and is insufficient to determine their long-term stability or expected service life. In view of this, and the significant lack of data on long-term field performance in the literature, S/S material has been extracted from full-scale remedial operations and examined using a variety of analytical techniques to evaluate field performance. The results, including those from X-ray analytical techniques, optical and electron microscopy and leaching tests are presented and discussed. The microstructure of retrieved samples was found to be analogous to other cement-based materials, but varied according to the soil type, the contaminants present, the treatment applied and the field exposure conditions. Summary of the key microstructural features in the USA and UK is presented in this work. The work has shown that during 16 years of service the S/S wastes investigated performed satisfactorily. Copyright 2010 Elsevier B.V. All rights reserved.

Long-term performance of aged waste forms treated by stabilization/solidification

International Nuclear Information System (INIS)

Antemir, Aurora; Hills, Colin D.; Carey, Paula J.; Gardner, Kevin H.; Bates, Edward R.; Crumbie, Alison K.

2010-01-01

Current regulatory testing of stabilized/solidified (S/S) soils is based on short-term performance tests and is insufficient to determine their long-term stability or expected service life. In view of this, and the significant lack of data on long-term field performance in the literature, S/S material has been extracted from full-scale remedial operations and examined using a variety of analytical techniques to evaluate field performance. The results, including those from X-ray analytical techniques, optical and electron microscopy and leaching tests are presented and discussed. The microstructure of retrieved samples was found to be analogous to other cement-based materials, but varied according to the soil type, the contaminants present, the treatment applied and the field exposure conditions. Summary of the key microstructural features in the USA and UK is presented in this work. The work has shown that during 16 years of service the S/S wastes investigated performed satisfactorily.

System and method for determining stability of a neural system

Science.gov (United States)

Curtis, Steven A. (Inventor)

2011-01-01

Disclosed are methods, systems, and computer-readable media for determining stability of a neural system. The method includes tracking a function world line of an N element neural system within at least one behavioral space, determining whether the tracking function world line is approaching a psychological stability surface, and implementing a quantitative solution that corrects instability if the tracked function world line is approaching the psychological stability surface.

Stability Analysis on Sparsely Encoded Associative Memory with Short-Term Synaptic Dynamics

Science.gov (United States)

Xu, Muyuan; Katori, Yuichi; Aihara, Kazuyuki

This study investigates the stability of sparsely encoded associative memory in a network composed of stochastic neurons. The incorporation of short-term synaptic dynamics significantly changes the stability with respect to synaptic properties. Various states including static and oscillatory states are found in the network dynamics. Specifically, the sparseness of memory patterns raises the problem of spurious states. A mean field model is used to analyze the detailed structure in the stability and show that the performance of memory retrieval is recovered by appropriate feedback.

STABILITY OF LINEAR SYSTEMS WITH MARKOVIAN JUMPS

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Jorge Enrique Mayta Guillermo

2016-12-01

Full Text Available In this work we will analyze the stability of linear systems governed by a Markov chain, this family is known in the specialized literature as linear systems with Markov jumps or by its acronyms in English MJLS as it is denoted in [1]. Linear systems governed by a Markov chain are dynamic systems with abrupt changes. We give some denitions of stability for the MJLS system, where these types of stability are equivalent as long as the state space of the Markov chain is nite. Finally we present a theorem that characterizes the stochastic stability by means of an equation of the Lyapunov type. The result is a generalization of a theorem in classical theory.

Long-term stability of the BDNPF/BDNPA nitroplaticizer system: an MMR analysis. Progress report, October--December 1975

International Nuclear Information System (INIS)

Clink, G.L.

1976-01-01

NMR analysis of the BDNPF/BDNPA eutectic system reaffirms the molecular integrity of the constituents, the stability of their molar ratios, and the effective retardant effect of the phenyl-beta-napthylamine antioxidant. Additional work on the analysis of the PBX 9501 system is underway at the present time

Moduli stabilization and uplifting with dynamically generated F-terms

International Nuclear Information System (INIS)

Dudas, Emilian; Papineau, Chloe; Pokorski, Stefan

2007-01-01

We use the F-term dynamical supersymmetry breaking models with metastable vacua in order to uplift the vacuum energy in the KKLT moduli stabilization scenario. The main advantage compared to earlier proposals is the manifest supersymmetric treatment and the natural coexistence of a TeV gravitino mass with a zero cosmological constant. We argue that it is generically difficult to avoid anti de-Sitter supersymmetric minima, however the tunneling rate from the metastable vacuum with zero vacuum energy towards them can be very suppressed. We briefly comment on the properties of the induced soft terms in the observable sector

Moduli stabilization and uplifting with dynamically generated F-terms

Energy Technology Data Exchange (ETDEWEB)

Dudas, Emilian [CERN Theory Division, CH-1211, Geneva 23 (Switzerland); Papineau, Chloe [CPhT, Ecole Polytechnique, F-91128 Palaiseau Cedex (France); Pokorski, Stefan [Institute of Theoretical Physics, Univ. of Warsaw, 00-681 Warsaw (Poland)

2007-02-15

We use the F-term dynamical supersymmetry breaking models with metastable vacua in order to uplift the vacuum energy in the KKLT moduli stabilization scenario. The main advantage compared to earlier proposals is the manifest supersymmetric treatment and the natural coexistence of a TeV gravitino mass with a zero cosmological constant. We argue that it is generically difficult to avoid anti de-Sitter supersymmetric minima, however the tunneling rate from the metastable vacuum with zero vacuum energy towards them can be very suppressed. We briefly comment on the properties of the induced soft terms in the observable sector.

Tritium systems test assembly stabilization

International Nuclear Information System (INIS)

Jasen, William G.; Michelotti, Roy A.; Anast, Kurt R.; Tesch, Charles

2004-01-01

The Tritium Systems Test Assembly (TSTA) was a facility dedicated to tritium technology Research and Development (R and D) primarily for future fusion power reactors. The facility was conceived in mid 1970's, operations commenced in early 1980's, stabilization and deactivation began in 2000 and were completed in 2003. The facility will remain in a Surveillance and Maintenance (S and M) mode until the Department of Energy (DOE) funds demolition of the facility, tentatively in 2009. A safe and stable end state was achieved by the TSTA Facility Stabilization Project (TFSP) in anticipation of long term S and M. At the start of the stabilization project, with an inventory of approximately 140 grams of tritium, the facility was designated a Hazard Category (HC) 2 Non-Reactor Nuclear facility as defined by US Department of Energy standard DOE-STD-1027-92 (1997). The TSTA facility comprises a laboratory area, supporting rooms, offices and associated laboratory space that included more than 20 major tritium handling systems. The project's focus was to reduce the tritium inventory by removing bulk tritium, tritiated water wastes, and tritium-contaminated high-inventory components. Any equipment that remained in the facility was stabilized in place. All of the gloveboxes and piping were rendered inoperative and vented to atmosphere. All equipment, and inventoried tritium contamination, remaining in the facility was left in a safe-and-stable state. The project used the End Points process as defined by the DOE Office of Environmental Management (web page http://www.em.doe.- gov/deact/epman.htmtlo) document and define the end state required for the stabilization of TSTA Facility. The End Points process added structure that was beneficial through virtually all phases of the project. At completion of the facility stabilization project the residual tritium inventory was approximately 3,000 curies, considerably less than the 1.6-gram threshold for a HC 3 facility. TSTA is now

Improved Robust Stability Criterion of Networked Control Systems with Transmission Delays and Packet Loss

Directory of Open Access Journals (Sweden)

Shenping Xiao

2014-01-01

Full Text Available The problem of stability analysis for a class of networked control systems (NCSs with network-induced delay and packet dropout is investigated in this paper. Based on the working mechanism of zero-order holder, the closed-loop NCS is modeled as a continuous-time linear system with input delay. By introducing a novel Lyapunov-Krasovskii functional which splits both the lower and upper bounds of the delay into two subintervals, respectively, and utilizes reciprocally convex combination technique, a new stability criterion is derived in terms of linear matrix inequalities. Compared with previous results in the literature, the obtained stability criterion is less conservative. Numerical examples demonstrate the validity and feasibility of the proposed method.

LMI-based stability analysis of fuzzy-model-based control systems using approximated polynomial membership functions.

Science.gov (United States)

Narimani, Mohammand; Lam, H K; Dilmaghani, R; Wolfe, Charles

2011-06-01

Relaxed linear-matrix-inequality-based stability conditions for fuzzy-model-based control systems with imperfect premise matching are proposed. First, the derivative of the Lyapunov function, containing the product terms of the fuzzy model and fuzzy controller membership functions, is derived. Then, in the partitioned operating domain of the membership functions, the relations between the state variables and the mentioned product terms are represented by approximated polynomials in each subregion. Next, the stability conditions containing the information of all subsystems and the approximated polynomials are derived. In addition, the concept of the S-procedure is utilized to release the conservativeness caused by considering the whole operating region for approximated polynomials. It is shown that the well-known stability conditions can be special cases of the proposed stability conditions. Simulation examples are given to illustrate the validity of the proposed approach.

Stability Criterion of Linear Stochastic Systems Subject to Mixed H2/Passivity Performance

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Cheung-Chieh Ku

2015-01-01

Full Text Available The H2 control scheme and passivity theory are applied to investigate the stability criterion of continuous-time linear stochastic system subject to mixed performance. Based on the stochastic differential equation, the stochastic behaviors can be described as multiplicative noise terms. For the considered system, the H2 control scheme is applied to deal with the problem on minimizing output energy. And the asymptotical stability of the system can be guaranteed under desired initial conditions. Besides, the passivity theory is employed to constrain the effect of external disturbance on the system. Moreover, the Itô formula and Lyapunov function are used to derive the sufficient conditions which are converted into linear matrix inequality (LMI form for applying convex optimization algorithm. Via solving the sufficient conditions, the state feedback controller can be established such that the asymptotical stability and mixed performance of the system are achieved in the mean square. Finally, the synchronous generator system is used to verify the effectiveness and applicability of the proposed design method.

On the long-term stability of calibration standards in different matrices

International Nuclear Information System (INIS)

Kandić, A.; Vukanac, I.; Djurašević, M.; Novković, D.; Šešlak, B.; Milošević, Z.

2012-01-01

In order to assure Quality Control in accordance with ISO/IEC 17025, it was important, from metrological point of view, to examine the long-term stability of calibration standards previously prepared. Comprehensive reconsideration on efficiency curves with respect to the ageing of calibration standards is presented in this paper. The calibration standards were re-used after a period of 5 years and analysis of the results showed discrepancies in efficiency values. - Highlights: ► Long-term stability of calibration standards (ISO 17025 Quality Control) was analyzed. ► Calibration standards covered the wide range of densities and chemical composition. ► Mineralized grass, powdered milk, surface soil and sand were used as standard matrices. ► Calibration standards were re-evaluated after 5 years. ► Results showed discrepancies of efficiency values.

Fuzzy stability and synchronization of hyperchaos systems

International Nuclear Information System (INIS)

Wang Junwei; Xiong Xiaohua; Zhao Meichun; Zhang Yanbin

2008-01-01

This paper studies stability and synchronization of hyperchaos systems via a fuzzy-model-based control design methodology. First, we utilize a Takagi-Sugeno fuzzy model to represent a hyperchaos system. Second, we design fuzzy-model-based controllers for stability and synchronization of the system, based on so-called 'parallel distributed compensation (PDC)'. Third, we reduce a question of stabilizing and synchronizing hyperchaos systems to linear matrix inequalities (LMI) so that convex programming techniques can solve these LMIs efficiently. Finally, the generalized Lorenz hyperchaos system is employed to illustrate the effectiveness of our designing controller

Screening of anionic-modified polymers in terms of stability, disintegration, and swelling behavior.

Science.gov (United States)

Laffleur, Flavia; Ijaz, Muhammad; Menzel, Claudia

2017-11-01

This study aimed to screen the stability, disintegration, and swelling behavior of chemically modified anionic polymers. Investigated polymers were well-known and widely used staples of the pharmaceutical and medical field, namely, alginate (AL), carboxymethyl cellulose (CMC), polycarbophil (PC), and hyaluronic acid (HA). On the basis of amide bond formation between the carboxylic acid moieties of anionic polymers and the primary amino group of the modification ligand cysteine (CYS), the modified polymers were obtained. Unmodified polymers served as controls throughout all studies. With the Ellman's assay, modification degrees were determined of synthesized polymeric excipients. Stability assay in terms of erosion study at physiological conditions were performed. Moreover, water uptake of compressed polymeric discs were evaluated and further disintegration studies according to the USP were carried out to define the potential ranking. Results ranking figured out PCCYS > CMCCYS > HACYS > ALCYS in terms of water uptake capacity compared to respective controls. Cell viability assays on Caco-2 cell line as well as on RPMI 2650 (ATTC CCL30) proved modification not being harmful to those. Due to the results of this study, an intense screening of prominent anionic polymer derivate was performed in order to help the pharmaceutical research for the best choice of polymeric excipients for developments of controlled drug release systems.

Optimization of scintillator loading with the tellurium-130 isotope for long-term stability

Science.gov (United States)

Duhamel, Lauren; Song, Xiaoya; Goutnik, Michael; Kaptanoglu, Tanner; Klein, Joshua; SNO+ Collaboration

2017-09-01

Tellurium-130 was selected as the isotope for the SNO + neutrinoless double beta decay search, as 130Te decays to 130Xe via double beta decay. Linear alkyl benzene(LAB) is the liquid scintillator for the SNO + experiment. To load tellurium into scintillator, it is combined with 1,2-butanediol to form an organometallic complex, commonly called tellurium butanediol (TeBD). This study focuses on maximizing the percentage of tellurium loaded into scintillator and evaluates the complex's long-term stability. Studies on the effect of nucleation due to imperfections in the detector's surface and external particulates were employed by filtration and induced nucleation. The impact of water on the stability of TeBD complex was evaluated by liquid-nitrogen sparging, variability in pH and induced humidity. Alternative loading methods were evaluated, including the addition of stability-inducing organic compounds. Samples of tellurium-loaded scintillator were synthesized, treated, and consistently monitored in a controlled environment. It was found that the hydronium ions cause precipitation in the loaded scintillator, demonstrating that water has a detrimental effect on long-term stability. Optimization of loaded scintillator stability can contribute to the SNO + double beta decay search.

Infant temperament: stability by age, gender, birth order, term status, and socioeconomic status.

Science.gov (United States)

Bornstein, Marc H; Putnick, Diane L; Gartstein, Maria A; Hahn, Chun-Shin; Auestad, Nancy; O'Connor, Deborah L

2015-01-01

Two complementary studies focused on stability of infant temperament across the 1st year and considered infant age, gender, birth order, term status, and socioeconomic status (SES) as moderators. Study 1 consisted of 73 mothers of firstborn term girls and boys queried at 2, 5, and 13 months of age. Study 2 consisted of 335 mothers of infants of different gender, birth order, term status, and SES queried at 6 and 12 months. Consistent positive and negative affectivity factors emerged at all time points across both studies. Infant temperament proved stable and robust across gender, birth order, term status, and SES. Stability coefficients for temperament factors and scales were medium to large for shorter ( 10 months) intervals. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Long-term stabilization of uranium mill tailings

International Nuclear Information System (INIS)

Voorhees, L.D.; Sale, M.J.; Webb, J.W.; Mulholland, P.J.

1984-01-01

The primary hazard associated with uranium mill tailings is exposure to a radioactive gas, radon-222, the concentration of which has been correlated with the occurrence of lung cancer. Previous studies on radon attenuation conclude that the placement of earthen cover materials over the tailings is the most effective technique for reducing radioactive emissions and dispersal of tailings. The success of such a plan, however, is dependent on ensuring the long-term integrity of these cover materials. Soil erosion from water and wind is the major natural cause of destabilizing earthen cover materials. Field data related to the control of soil loss are limited and only indirectly apply to the problem of isolation of uranium mill tailings over very long time periods (up to 80,000 a). However, sufficient information is available to determine benefits that will result from changes in specific design variables and to evaluate the need for different design strategies among potential disposal sites. The three major options available for stabilization of uranium mill tailings are (1) rock cover, (2) soil and revegetation, or (3) a combination of both on different portions of the tailings cover. The optimal choice among these alternatives depends on site-specific characteristics such as climate and local geomorphology and soils, and on design variables such as embankment heights and slopes, modification of upstream drainage, and revegetation practices. Generally, geomorphic evidence suggests that use of soil and vegetation alone will not be adequate to reduce erosion on slopes greater than about 5 to 9%. For these steeper slopes, the use of rock talus or riprap will be necessary to maximize the probability of long-term stability. The use of vegetation to control erosion on the flatter portions of the site may be practicable in regions of the USA with sufficient rainfall and suitable soil types, but revegetation practices must be carefully evaluated to ensure that long-term

MHD stability properties of a system of reduced toroidal MHD equations

International Nuclear Information System (INIS)

Maschke, E.K.; Morros Tosas, J.; Urquijo, G.

1993-01-01

A system of reduced toroidal magneto-hydrodynamic (MHD) equations is derived from a general scalar representation of the complete MHD system, using an ordering in terms of the inverse aspect ratio ε of a toroidal plasma. It is shown that the energy principle for the reduced equations is identical with the usual energy principle of the complete MHD system, to the appropriate order in ε. Thus, the reduced equations have the same ideal MHD stability limits as the full MHD equations. (authors). 6 refs

A Lie algebraic condition for exponential stability of discrete hybrid systems and application to hybrid synchronization.

Science.gov (United States)

Zhao, Shouwei

2011-06-01

A Lie algebraic condition for global exponential stability of linear discrete switched impulsive systems is presented in this paper. By considering a Lie algebra generated by all subsystem matrices and impulsive matrices, when not all of these matrices are Schur stable, we derive new criteria for global exponential stability of linear discrete switched impulsive systems. Moreover, simple sufficient conditions in terms of Lie algebra are established for the synchronization of nonlinear discrete systems using a hybrid switching and impulsive control. As an application, discrete chaotic system's synchronization is investigated by the proposed method.

Stability Analysis of Nonlinear Time–Delayed Systems with Application to Biological Models

Directory of Open Access Journals (Sweden)

Kruthika H.A.

2017-03-01

Full Text Available In this paper, we analyse the local stability of a gene-regulatory network and immunotherapy for cancer modelled as nonlinear time-delay systems. A numerically generated kernel, using the sum-of-squares decomposition of multivariate polynomials, is used in the construction of an appropriate Lyapunov–Krasovskii functional for stability analysis of the networks around an equilibrium point. This analysis translates to verifying equivalent LMI conditions. A delay-independent asymptotic stability of a second-order model of a gene regulatory network, taking into consideration multiple commensurate delays, is established. In the case of cancer immunotherapy, a predator–prey type model is adopted to describe the dynamics with cancer cells and immune cells contributing to the predator–prey population, respectively. A delay-dependent asymptotic stability of the cancer-free equilibrium point is proved. Apart from the system and control point of view, in the case of gene-regulatory networks such stability analysis of dynamics aids mimicking gene networks synthetically using integrated circuits like neurochips learnt from biological neural networks, and in the case of cancer immunotherapy it helps determine the long-term outcome of therapy and thus aids oncologists in deciding upon the right approach.

Stability of digital feedback control systems

Directory of Open Access Journals (Sweden)

Larkin Eugene

2018-01-01

Lag time characteristics are used for investigation of stability of linear systems. Digital PID controller is divided onto linear part, which is realized with a soft and pure lag unit, which is realized with both hardware and software. With use notions amplitude and phase margins, condition for stability of system functioning are obtained. Theoretical results are confirm with computer experiment carried out on the third-order system.

Dynamic Stability Experiment of Maglev Systems,

Science.gov (United States)

1995-04-01

This report summarizes the research performed on maglev vehicle dynamic stability at Argonne National Laboratory during the past few years. It also... maglev system, it is important to consider this phenomenon in the development of all maglev systems. This report presents dynamic stability experiments...on maglev systems and compares their numerical simulation with predictions calculated by a nonlinear dynamic computer code. Instabilities of an

Robust Stability Analysis of the Space Launch System Control Design: A Singular Value Approach

Science.gov (United States)

Pei, Jing; Newsome, Jerry R.

2015-01-01

Classical stability analysis consists of breaking the feedback loops one at a time and determining separately how much gain or phase variations would destabilize the stable nominal feedback system. For typical launch vehicle control design, classical control techniques are generally employed. In addition to stability margins, frequency domain Monte Carlo methods are used to evaluate the robustness of the design. However, such techniques were developed for Single-Input-Single-Output (SISO) systems and do not take into consideration the off-diagonal terms in the transfer function matrix of Multi-Input-Multi-Output (MIMO) systems. Robust stability analysis techniques such as H(sub infinity) and mu are applicable to MIMO systems but have not been adopted as standard practices within the launch vehicle controls community. This paper took advantage of a simple singular-value-based MIMO stability margin evaluation method based on work done by Mukhopadhyay and Newsom and applied it to the SLS high-fidelity dynamics model. The method computes a simultaneous multi-loop gain and phase margin that could be related back to classical margins. The results presented in this paper suggest that for the SLS system, traditional SISO stability margins are similar to the MIMO margins. This additional level of verification provides confidence in the robustness of the control design.

The Nature and Assessment of Systemic Risk in Terms of Liquidity of the Banking System

Directory of Open Access Journals (Sweden)

Lavreniuk Vladyslav V.

2016-11-01

Full Text Available The aim of the article is to determine the nature of systemic risk as a threat to the financial stability of the banking system and develop analytical tools to assess its impact on the banking system in terms of its liquidity. To solve the tasks assigned, there used general scientific and specific methods, such as: logical and dialectical method, mathematical and graphical one. Based on the generalization, analysis and comparison of different interpretations, there clarified the concept of «systemic risk» as a risk generated by financial institutions or individual sectors through the implementation of the mechanism of risk transmission, achieving significant scale of distribution and adversely affecting the stability of the financial system and the real sector of economy. There identified key aspects of systemic risk: a systemic risk is not a sum of all individual risks of financial institutions; b spreads through the channels of interconnectedness between financial institutions; c is a result of accumulated structural imbalances; d affects the stability of the financial/banking system, public confidence and the real sector of economy. Analytical tools for estimation of the bank’s contribution to the systemic liquidity risk on the basis of which it is determined that the first place in terms of the effect on the aggregate systemic risk of liquidity of the Ukrainian banking system is occupied by banks of Group I, the second place — by Privatbank, the third, fourth, fifth places — by banks in Group II — Oschadbank, Ukreximbank. It is found that it is systemically important state-owned banks that have a significant impact on systemic liquidity risk. It is determined that the probability of default of a leading systemically important bank could result in considerable cumulative losses for the entire banking system and real economy. The prospects of further research are the development of tools for systemic risk assessment with respect to

Aggregate Stability of Tropical Soils Under Long-Term Eucalyptus Cultivation

Science.gov (United States)

Eucalyptus cultivation has increased in all Brazilian regions. Despite the large amount of cultivated area, little is known about how this kind of management system affects soil properties, mainly the aggregate stability. Aggregate stability analyses have proved to be a sensitive tool to measure soi...

Advanced nonlinear theory: Long-term stability at the SSC

International Nuclear Information System (INIS)

Heifets, S.

1987-01-01

This paper discussed the long-term stability of the particle beams in the Superconducting Super Collider. In particular the dynamics of a single particle beam is considered in depth. The topics of this paper include: the Hamiltonian of this particle approach, perturbation theory, canonical transformations, interaction of the resonances, structure of the phase space, synchro-Betatron oscillations, modulation diffusion and noise-resonance interaction. 36 refs

Very high stability systems: LMJ target alignment system and MTG imager test setup

Science.gov (United States)

Compain, Eric; Maquet, Philippe; Kunc, Thierry; Marque, Julien; Lauer-Solelhac, Maxime; Delage, Laurent; Lanternier, Catherine

2015-09-01

Most of space instruments and research facilities require test equipment with demanding opto-mechanical stability. In some specific cases, when the stability performance directly drives the final performance of the scientific mission and when feasibility is questionable, specific methods must be implemented for the associated technical risk management. In present paper, we will present our heritage in terms of methodology, design, test and the associated results for two specific systems : the SOPAC-POS and the MOTA, generating new references for future developments. From a performance point of view, we will emphasis on following key parameters : design symmetry, thermal load management, and material and structural choices. From a method point of view the difficulties arise first during design, from the strong coupling between the thermal, mechanical and optical performance models, and then during testing, from the difficulty of conceiving test setup having appropriate performance level. We will present how these limitations have been overcome. SOPAC-POS is the target alignment system of the LMJ, Laser Mega Joule, the French inertial confinement fusion research center. Its stability has been demonstrated by tests in 2014 after 10 years of research and development activities, achieving 1μm stability @ 6m during one hour periods. MOTA is an Optical Ground Support Equipment aiming at qualifying by tests the Flexible Combined Imager (FCI). FCI is an instrument for the meteorological satellite MTG-I, a program of and funded by the European Space Agency and under prime contractorship of Thales Alenia Space. Optimized design will allow to get better than 0.2 μrad stability for one hour periods, as required for MTF measurement.

Long-term prospects for oil market stability

Energy Technology Data Exchange (ETDEWEB)

Subroto, Dr [OPEC, Vienna (AT)

1989-10-01

OPEC recognize that energy consumption has its social costs and benefits, and that some energy sources impose fewer costs on society. We must consider the environmental implications of oil extraction. Our policies today should enable future generations to secure their energy needs, and OPEC is well-positioned to supply them. An inward-looking OPEC, distracted by internal wranglings and inconsistencies, cannot expect to be a stabilizing force in the oil markets. We have sought, therefore, to put our own house in order. Aside from the debate on depletion policy, a major strain on OPEC stability is the growing tendency towards regionalization in the world oil market. And the absence of universally acceptable quota allocation criteria means that OPEC may have to live with instability for some time to come, but this will be manageable in the short run. In the medium term, however, the call on OPEC oil in the 1990s is predicted to rise to a level commensurate with the sustainable capacities of member states. Producers and consumers have a common interest and should share a similar perspective on the inter-dependence between energy, the environment and economic development. (author).

A novel stabilization condition for T-S polynomial fuzzy system with time-delay:A sum-of-squares approach

OpenAIRE

Tsai, Shun Hung; Chen, Yu-An; Chen, Yu-Wen; Lo, Ji-Chang; Lam, Hak-Keung

2017-01-01

A novel stabilization problem for T-S polynomial fuzzy system with time-delay is investigated in this paper. Firstly, a polynomial fuzzy controller for T-S polynomial fuzzy system with time-delay is proposed. In addition, based on polynomial Lyapunov-Krasovskii function and the developed polynomial slack variable matrices, a novel stabilization condition for T-S polynomial fuzzy system with time-delay is presented in terms of sum-of-square (SOS) form. Lastly, nonlinear system with time-delay ...

Stability of power systems coupled with market dynamics

Science.gov (United States)

Meng, Jianping

This Ph.D. thesis presented here spans two relatively independent topics. The first part, Chapter 2 is self-contained, and is dedicated to studies of new algorithms for power system state estimation. The second part, encompassing the remaining chapters, is dedicated to stability analysis of power system coupled with market dynamics. The first part of this thesis presents improved Newton's methods employing efficient vectorized calculations of higher order derivatives in power system state estimation problems. The improved algorithms are proposed based on an exact Newton's method using the second order terms. By efficiently computing an exact gain matrix, combined with a special optimal multiplier method, the new algorithms show more reliable convergence compared with the existing methods of normal equations, orthogonal decomposition, and Hachtel's sparse tableau. Our methods are able to handle ill-conditioned problems, yet show minimal penalty in computational cost for well-conditioned cases. These claims are illustrated through the standard IEEE 118 and 300 bus test examples. The second part of the thesis focuses on stability analysis of market/power systems. The work presented is motivated by an emerging problem. As the frequency of market based dispatch updates increases, there will inevitably be interaction between the dynamics of markets determining the generator dispatch commands, and the physical response of generators and network interconnections, necessitating the development of stability analysis for such coupled systems. We begin with numeric tests using different market models, with detailed machine/exciter/turbine/governor dynamics, in the New England 39 bus test system. A progression of modeling refinements are introduced, including such non-ideal effects as time delays. Electricity market parameter identification algorithms are also studied based on real time data from the PJM electricity market. Finally our power market model is augmented by optimal

Stability of a mobile electron linear accelerator system for intraoperative radiation therapy

International Nuclear Information System (INIS)

Beddar, A. Sam

2005-01-01

The flexibility of mobile electron accelerators, which are designed to be transported to an operating room and plugged into a normal 3-phase outlet, make them ideal for use in intraoperative radiation therapy. However, their transportability may cause trepidation among potential users, who may question the stability of such an accelerator over a period of use. In order to address this issue, we have studied the short-term stability of the Mobetron system over 20 daily quality assurance trials. Variations in output generally varied within ±2% for the four energies produced by the unit (4, 6, 9, and 12 MeV) and changes in energy produced an equivalent shift of less than 1 mm on the depth-dose curve. Hours of inactivity, with the Mobetron powered on for use either throughout the day or overnight, led to variations in output of about 1%. Finally, we have tested the long-term stability of the absolute dose output of the Mobetron, which showed a change of about 1% per year

A hybrid superconducting fault current limiter for enhancing transient stability in Korean power systems

Science.gov (United States)

Seo, Sangsoo; Kim, Seog-Joo; Moon, Young-Hwan; Lee, Byongjun

2013-11-01

Additional power generation sites have been limited in Korea, despite the fact load demands are gradually increasing. In order to meet these increasing demands, Korea’s power system company has begun constructing new generators at existing sites. Thus, multi-unit plants can create problems in terms of transient stability when a large disturbance occurs. This paper proposes a hybrid superconducting fault current limiter (SFCL) application to enhance the transient stability of multi-unit power plants. SFCLs reduce fault currents, and limitation currents decrease the imbalance of the mechanical and electrical torque of the generators, resulting in an improvement in transient stability.

Stability analysis of fuzzy parametric uncertain systems.

Science.gov (United States)

Bhiwani, R J; Patre, B M

2011-10-01

In this paper, the determination of stability margin, gain and phase margin aspects of fuzzy parametric uncertain systems are dealt. The stability analysis of uncertain linear systems with coefficients described by fuzzy functions is studied. A complexity reduced technique for determining the stability margin for FPUS is proposed. The method suggested is dependent on the order of the characteristic polynomial. In order to find the stability margin of interval polynomials of order less than 5, it is not always necessary to determine and check all four Kharitonov's polynomials. It has been shown that, for determining stability margin of FPUS of order five, four, and three we require only 3, 2, and 1 Kharitonov's polynomials respectively. Only for sixth and higher order polynomials, a complete set of Kharitonov's polynomials are needed to determine the stability margin. Thus for lower order systems, the calculations are reduced to a large extent. This idea has been extended to determine the stability margin of fuzzy interval polynomials. It is also shown that the gain and phase margin of FPUS can be determined analytically without using graphical techniques. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

Stability analysis of distributed order fractional chen system.

Science.gov (United States)

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

Science.gov (United States)

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

Solar Dynamic Power System Stability Analysis and Control

Science.gov (United States)

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.

Stabilization of classic and quantum systems

International Nuclear Information System (INIS)

Buts, V.A.

2012-01-01

It is shown that the mechanism of quantum whirligig can be successfully used for stabilization of classical systems. In particular, the conditions for stabilization of charged particles and radiation fluxes in plasma are found.

Performance Comparison of Adaptive Estimation Techniques for Power System Small-Signal Stability Assessment

Directory of Open Access Journals (Sweden)

E. A. Feilat

2010-12-01

Full Text Available This paper demonstrates the assessment of the small-signal stability of a single-machine infinite- bus power system under widely varying loading conditions using the concept of synchronizing and damping torques coefficients. The coefficients are calculated from the time responses of the rotor angle, speed, and torque of the synchronous generator. Three adaptive computation algorithms including Kalman filtering, Adaline, and recursive least squares have been compared to estimate the synchronizing and damping torque coefficients. The steady-state performance of the three adaptive techniques is compared with the conventional static least squares technique by conducting computer simulations at different loading conditions. The algorithms are compared to each other in terms of speed of convergence and accuracy. The recursive least squares estimation offers several advantages including significant reduction in computing time and computational complexity. The tendency of an unsupplemented static exciter to degrade the system damping for medium and heavy loading is verified. Consequently, a power system stabilizer whose parameters are adjusted to compensate for variations in the system loading is designed using phase compensation method. The effectiveness of the stabilizer in enhancing the dynamic stability over wide range of operating conditions is verified through the calculation of the synchronizing and damping torque coefficients using recursive least square technique.

Nonlinear physical systems spectral analysis, stability and bifurcations

CERN Document Server

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

Short-term stability test for thorium soil candidate a reference material

Energy Technology Data Exchange (ETDEWEB)

Clain, Almir F.; Fonseca, Adelaide M.G.; Dantas, Vanessa V.D.B.; Braganca, Maura J.C.; Souza, Poliana S., E-mail: almir@ird.gov.br, E-mail: adelaide@ird.gov.br, E-mail: vanessa@ird.gov.br, E-mail: maura@ird.gov.br, E-mail: poliana@bolsista.ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2015-07-01

This work describes a methodology to determine the soil short-term stability after the steps of production in laboratory. The short-term stability of the soil is an essential property to be determined in order to producing a reference material. The soil is a candidate of reference material for chemical analysis of thorium with metrological traceability to be used in environmental analysis, equipment calibration, validation methods, and quality control. A material is considered stable in a certain temperature if the property of interest does not change with time, considering the analytical random fluctuations. Due to this, the angular coefficient from the graphic of Th concentration versus elapsed time must be near to zero. The analytical determinations of thorium concentration were performed by Instrumental Neutron activation Analysis. The slopes and their uncertainties were obtained from the regression lines at temperatures of 20 deg C and 60 deg C, with control temperature of -20 deg C. From the obtained data a t-test was applied. In both temperatures the calculated t-value was lower than the critical value, so we can conclude with 95% confidence level that no significant changes happened during the period studied concerning thorium concentration in soil at temperatures of 20 deg C and 60 deg C, showing stability at these temperatures. (author)

Short-term stability test for thorium soil candidate a reference material

International Nuclear Information System (INIS)

Clain, Almir F.; Fonseca, Adelaide M.G.; Dantas, Vanessa V.D.B.; Braganca, Maura J.C.; Souza, Poliana S.

2015-01-01

This work describes a methodology to determine the soil short-term stability after the steps of production in laboratory. The short-term stability of the soil is an essential property to be determined in order to producing a reference material. The soil is a candidate of reference material for chemical analysis of thorium with metrological traceability to be used in environmental analysis, equipment calibration, validation methods, and quality control. A material is considered stable in a certain temperature if the property of interest does not change with time, considering the analytical random fluctuations. Due to this, the angular coefficient from the graphic of Th concentration versus elapsed time must be near to zero. The analytical determinations of thorium concentration were performed by Instrumental Neutron activation Analysis. The slopes and their uncertainties were obtained from the regression lines at temperatures of 20 deg C and 60 deg C, with control temperature of -20 deg C. From the obtained data a t-test was applied. In both temperatures the calculated t-value was lower than the critical value, so we can conclude with 95% confidence level that no significant changes happened during the period studied concerning thorium concentration in soil at temperatures of 20 deg C and 60 deg C, showing stability at these temperatures. (author)

Exponential Stability of Switched Positive Homogeneous Systems

Directory of Open Access Journals (Sweden)

Dadong Tian

2017-01-01

Full Text Available This paper studies the exponential stability of switched positive nonlinear systems defined by cooperative and homogeneous vector fields. In order to capture the decay rate of such systems, we first consider the subsystems. A sufficient condition for exponential stability of subsystems with time-varying delays is derived. In particular, for the corresponding delay-free systems, we prove that this sufficient condition is also necessary. Then, we present a sufficient condition of exponential stability under minimum dwell time switching for the switched positive nonlinear systems. Some results in the previous literature are extended. Finally, a numerical example is given to demonstrate the effectiveness of the obtained results.

Global exponential stability of BAM neural networks with time-varying delays and diffusion terms

International Nuclear Information System (INIS)

Wan Li; Zhou Qinghua

2007-01-01

The stability property of bidirectional associate memory (BAM) neural networks with time-varying delays and diffusion terms are considered. By using the method of variation parameter and inequality technique, the delay-independent sufficient conditions to guarantee the uniqueness and global exponential stability of the equilibrium solution of such networks are established

Global exponential stability of BAM neural networks with time-varying delays and diffusion terms

Science.gov (United States)

Wan, Li; Zhou, Qinghua

2007-11-01

The stability property of bidirectional associate memory (BAM) neural networks with time-varying delays and diffusion terms are considered. By using the method of variation parameter and inequality technique, the delay-independent sufficient conditions to guarantee the uniqueness and global exponential stability of the equilibrium solution of such networks are established.

Stability analysis of roadway embankments supported by stone columns with the presence of water table under short-term and long-term conditions

Directory of Open Access Journals (Sweden)

Kadhim Shaymaa Tareq

2018-01-01

Full Text Available Use of stone column technique to improve soft foundation soils under roadway embankments has proven to increase the bearing capacity and reduce the potential settlement. The potential contribution of stone columns to the stability of roadway embankments against general (i.e. deep-seated failure needs to be thoroughly investigated. Therefore, a two-dimensional finite difference model implemented by FLAC/SLOPE 7.0 software, was employed in this study to assess the stability of a roadway embankment fill built on a soft soil deposit improved by stone column technique. The stability factor of safety was obtained numerically under both short-term and long-term conditions with the presence of water table. Two methods were adopted to convert the three-dimensional model into plane strain condition: column wall and equivalent improved ground methods. The effect of various parameters was studied to evaluate their influence on the factor of safety against embankment instability. For instance, the column diameter, columns’ spacing, soft soil properties for short-term and long-term conditions, and the height and friction angle of the embankment fill. The results of this study are developed in several design charts.

The interplay among prey preference, nutrient enrichment and stability in an omnivory system

Directory of Open Access Journals (Sweden)

LDB. Faria

Full Text Available Food webs usually display an intricate mix of trophic interactions where multiple prey are common. In this context omnivory has been the subject of intensive analysis regarding food web stability and structure. In a three species omnivory setting it is shown that the modeling of prey preference by the top predator may exert a strong influence on the short as well as on the long term dynamics of the respective food web. Clearly, this has implications concerning the stability and the structure of omnivory systems under disturbances such as nutrient enrichment.

Functional stability of cerebral circulatory system

Science.gov (United States)

Moskalenko, Y. Y.

1980-01-01

The functional stability of the cerebral circulation system seems to be based on the active mechanisms and on those stemming from specific of the biophysical structure of the system under study. This latter parameter has some relevant criteria for its quantitative estimation. The data obtained suggest that the essential part of the mechanism for active responses of cerebral vessels which maintains the functional stability of this portion of the vascular system, consists of a neurogenic component involving central nervous structures localized, for instance, in the medulla oblongata.

Bundle Adjustment-Based Stability Analysis Method with a Case Study of a Dual Fluoroscopy Imaging System

Science.gov (United States)

Al-Durgham, K.; Lichti, D. D.; Detchev, I.; Kuntze, G.; Ronsky, J. L.

2018-05-01

A fundamental task in photogrammetry is the temporal stability analysis of a camera/imaging-system's calibration parameters. This is essential to validate the repeatability of the parameters' estimation, to detect any behavioural changes in the camera/imaging system and to ensure precise photogrammetric products. Many stability analysis methods exist in the photogrammetric literature; each one has different methodological bases, and advantages and disadvantages. This paper presents a simple and rigorous stability analysis method that can be straightforwardly implemented for a single camera or an imaging system with multiple cameras. The basic collinearity model is used to capture differences between two calibration datasets, and to establish the stability analysis methodology. Geometric simulation is used as a tool to derive image and object space scenarios. Experiments were performed on real calibration datasets from a dual fluoroscopy (DF; X-ray-based) imaging system. The calibration data consisted of hundreds of images and thousands of image observations from six temporal points over a two-day period for a precise evaluation of the DF system stability. The stability of the DF system - for a single camera analysis - was found to be within a range of 0.01 to 0.66 mm in terms of 3D coordinates root-mean-square-error (RMSE), and 0.07 to 0.19 mm for dual cameras analysis. It is to the authors' best knowledge that this work is the first to address the topic of DF stability analysis.

System evaluation of improved thermal stability jet fuels

Energy Technology Data Exchange (ETDEWEB)

Binns, K.E.; Dieterle, G.L.; Williams, T. [Univ. of Dayton Research Institute, OH (United States)

1995-05-01

A single-pass, single-tube heat exchanger device called the Phoenix rig and a single-pass, dual-heat exchanger system called the Extended Duration Thermal Stability Test system are specific devices/systems developed for evaluating jet fuel thermal stability. They have been used extensively in the evaluation of various jet fuels and thermal stability additives. The test results have indicated that additives can substantially improve the thermal stability of conventional jet fuels. Relationships of oxygen consumption, residence time, bulk, and wetted wall temperatures on coking deposits that form in the heated tubes have also been investigated.

Comment on the Long-Term Chemical and Mineralogical Stability of the Buffer

International Nuclear Information System (INIS)

Arthur, Randy; Apted, Mick; Stenhouse, Mike

2005-03-01

This report examines concepts and data that SKB may use to assess the long-term chemical and mineralogical evolution of bentonite barriers in a KBS-3 repository for spent nuclear fuel. Three interrelated topics are considered: mineral chemistry of the smectite clays; thermodynamic stability of the smectite clays; and bentonite-water interactions during the early thermal period of repository evolution. Smectites are complex solid solutions having variable compositions resulting from ionic substitutions on exchange, octahedral and tetrahedral sites in the crystalline lattice. Although little is known about the mechanisms and rates of reactions involving the latter two sites, abundant observational evidence from natural systems suggests that such reactions could occur to an appreciable extent in the buffer over the million year time frame being considered for an intact canister. We are not aware of any efforts in SKB's current modeling strategy to account for such reactions, and therefore question whether the strategy is appropriate for modeling the long-term chemical evolution of the buffer and associated potential effects on the desirable physical and rheological properties of this barrier material. The variable chemistry of smectites affects their thermodynamic stability. Models of smectite-water equilibria use either a fixed stoichiometric composition to approximate representative smectite varieties, or account for compositional variations using solid solution models and ideal mixing relations among thermodynamic components. In either case the thermodynamic properties of a specific smectite composition or of individual solid-solution components must usually be estimated. Recent reports suggest that SKB will not account explicitly for the thermodynamic properties of smectite in its models of bentonite-water interactions. Rather, the models will assume that this clay mineral has a fixed, though unspecified, composition representing an ion-exchanger phase. This phase

Global exponential stability of fuzzy cellular neural networks with delays and reaction-diffusion terms

International Nuclear Information System (INIS)

Wang Jian; Lu Junguo

2008-01-01

In this paper, we study the global exponential stability of fuzzy cellular neural networks with delays and reaction-diffusion terms. By constructing a suitable Lyapunov functional and utilizing some inequality techniques, we obtain a sufficient condition for the uniqueness and global exponential stability of the equilibrium solution for a class of fuzzy cellular neural networks with delays and reaction-diffusion terms. The result imposes constraint conditions on the network parameters independently of the delay parameter. The result is also easy to check and plays an important role in the design and application of globally exponentially stable fuzzy neural circuits

Stability and response bounds of non-conservative linear systems

DEFF Research Database (Denmark)

Pommer, Christian

2003-01-01

For a linear system of second order differential equations the stability is studied by Lyapunov's direct method. The Lyapunov matrix equation is solved and a sufficient condition for stability is expressed by the system matrices. For a system which satisfies the condition for stability the Lyapunov...

Stability of discrete memory states to stochastic fluctuations in neuronal systems

Science.gov (United States)

Miller, Paul; Wang, Xiao-Jing

2014-01-01

Noise can degrade memories by causing transitions from one memory state to another. For any biological memory system to be useful, the time scale of such noise-induced transitions must be much longer than the required duration for memory retention. Using biophysically-realistic modeling, we consider two types of memory in the brain: short-term memories maintained by reverberating neuronal activity for a few seconds, and long-term memories maintained by a molecular switch for years. Both systems require persistence of (neuronal or molecular) activity self-sustained by an autocatalytic process and, we argue, that both have limited memory lifetimes because of significant fluctuations. We will first discuss a strongly recurrent cortical network model endowed with feedback loops, for short-term memory. Fluctuations are due to highly irregular spike firing, a salient characteristic of cortical neurons. Then, we will analyze a model for long-term memory, based on an autophosphorylation mechanism of calcium/calmodulin-dependent protein kinase II (CaMKII) molecules. There, fluctuations arise from the fact that there are only a small number of CaMKII molecules at each postsynaptic density (putative synaptic memory unit). Our results are twofold. First, we demonstrate analytically and computationally the exponential dependence of stability on the number of neurons in a self-excitatory network, and on the number of CaMKII proteins in a molecular switch. Second, for each of the two systems, we implement graded memory consisting of a group of bistable switches. For the neuronal network we report interesting ramping temporal dynamics as a result of sequentially switching an increasing number of discrete, bistable, units. The general observation of an exponential increase in memory stability with the system size leads to a trade-off between the robustness of memories (which increases with the size of each bistable unit) and the total amount of information storage (which decreases

On the stability of non-linear systems

International Nuclear Information System (INIS)

Guelman, M.

1968-09-01

A study is made of the absolute stability of nonlinear systems, using Liapounov's second method and taking into account the results obtained from V.M. Popov's work. The results already established are first presented, in particular concerning the frequency domain criterions for absolute stability of automatic control systems containing one single non linearity. The results have been extended to show the existence of a limiting parabola. New use is then made of the methods studied for deriving absolute stability criterions for a system containing a different type of non linearity. Finally, the results obtained are considered from the point of view of Aizerman's conjecture. (author) [fr

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)

On-line tuning of a fuzzy-logic power system stabilizer

International Nuclear Information System (INIS)

Hossein-Zadeh, N.; Kalam, A.

2002-01-01

A scheme for on-line tuning of a fuzzy-logic power system stabilizer is presented. firstly, a fuzzy-logic power system stabilizer is developed using speed deviation and accelerating power as the controller input variables. The inference mechanism of fuzzy-logic controller is represented by a decision table, constructed of linguistic IF-THEN rules. The Linguistic rules are available from experts and the design procedure is based on these rules. It assumed that an exact model of the plant is not available and it is difficult to extract the exact parameters of the power plant. Thus, the design procedure can not be based on an exact model. This is an advantage of fuzzy logic that makes the design of a controller possible without knowing the exact model of the plant. Secondly, two scaling parameters are introduced to tune the fuzzy-logic power system stabilizer. These scaling parameters are the outputs of another fuzzy-logic system, which gets the operating conditions of power system as inputs. These mechanism of tuning the fuzzy-logic power system stabilizer makes the fuzzy-logic power system stabilizer adaptive to changes in the operating conditions. Therefore, the degradation of the system response, under a wide range of operating conditions, is less compared to the system response with a fixed-parameter fuzzy-logic power system stabilizer and a conventional (linear) power system stabilizer. The tuned stabilizer has been tested by performing nonlinear simulations using a synchronous machine-infinite bus model. The responses are compared with a fixed parameters fuzzy-logic power system stabilizer and a conventional (linear) power system stabilizer. It is shown that the tuned fuzzy-logic power system stabilizer is superior to both of them

Dynamic postural stability in blind athletes using the biodex stability system.

Science.gov (United States)

Aydoğ, E; Aydoğ, S T; Cakci, A; Doral, M N

2006-05-01

Three systems affect the upright standing posture in humans - visual, vestibular, and somatosensory. It is well known that the visually impaired individuals have bad postural balance. On the other hand, it is a well documented fact that some sports can improve postural balance. Therefore, it is aimed in this study to evaluate the dynamic postural stability in goal-ball athletes. Twenty blind goal-ball players, 20 sighted and 20 sedentary blind controls were evaluated using the Biodex Stability System. Three adaptation trials and three test evaluations (a 20-second balance test at a platform stability of 8) were applied to the blind people, and to the sighted with eyes open and closed. Dynamic postural stability was measured on the basis of three indices: overall, anteroposterior, and mediolateral. Means of each test score were calculated. The tests results were compared for the blind athletes, sighted (with eyes open and closed) subjects, and sedentary blind people. There were significant differences between the results of the blind people and the sighted subjects with regards to all of the three indices. Although the stability of goal-ball players was better than sedentary blinds', only ML index values were statistically different (4.47 +/- 1.24 in the goal-ball players; 6.46 +/- 3.42 in the sedentary blind, p = 0.04). Dynamic postural stability was demonstrated to be affected by vision; and it was found that blind people playing goal-ball 1 - 2 days per week have higher ML stability than the sedentary sighted people.

A support vector machine (SVM) based voltage stability classifier

Energy Technology Data Exchange (ETDEWEB)

Dosano, R.D.; Song, H. [Kunsan National Univ., Kunsan, Jeonbuk (Korea, Republic of); Lee, B. [Korea Univ., Seoul (Korea, Republic of)

2007-07-01

Power system stability has become even more complex and critical with the advent of deregulated energy markets and the growing desire to completely employ existing transmission and infrastructure. The economic pressure on electricity markets forces the operation of power systems and components to their limit of capacity and performance. System conditions can be more exposed to instability due to greater uncertainty in day to day system operations and increase in the number of potential components for system disturbances potentially resulting in voltage stability. This paper proposed a support vector machine (SVM) based power system voltage stability classifier using local measurements of voltage and active power of load. It described the procedure for fast classification of long-term voltage stability using the SVM algorithm. The application of the SVM based voltage stability classifier was presented with reference to the choice of input parameters; input data preconditioning; moving window for feature vector; determination of learning samples; and other considerations in SVM applications. The paper presented a case study with numerical examples of an 11-bus test system. The test results for the feasibility study demonstrated that the classifier could offer an excellent performance in classification with time-series measurements in terms of long-term voltage stability. 9 refs., 14 figs.

F-term stabilization of odd axions in LARGE volume scenario

International Nuclear Information System (INIS)

Gao, Xin; Shukla, Pramod

2014-01-01

In the context of the LARGE volume scenario, stabilization of axionic moduli is revisited. This includes both even and odd axions with their scalar potential being generated by F-term contributions via various tree-level and non-perturbative effects like fluxed E3-brane instantons and fluxed poly-instantons. In all the cases, we estimate the decay constants and masses of the axions involved

Exponential Stability for Impulsive BAM Neural Networks with Time-Varying Delays and Reaction-Diffusion Terms

Directory of Open Access Journals (Sweden)

Qiankun Song

2007-06-01

Full Text Available Impulsive bidirectional associative memory neural network model with time-varying delays and reaction-diffusion terms is considered. Several sufficient conditions ensuring the existence, uniqueness, and global exponential stability of equilibrium point for the addressed neural network are derived by M-matrix theory, analytic methods, and inequality techniques. Moreover, the exponential convergence rate index is estimated, which depends on the system parameters. The obtained results in this paper are less restrictive than previously known criteria. Two examples are given to show the effectiveness of the obtained results.

Exponential Stability for Impulsive BAM Neural Networks with Time-Varying Delays and Reaction-Diffusion Terms

Directory of Open Access Journals (Sweden)

Cao Jinde

2007-01-01

Full Text Available Impulsive bidirectional associative memory neural network model with time-varying delays and reaction-diffusion terms is considered. Several sufficient conditions ensuring the existence, uniqueness, and global exponential stability of equilibrium point for the addressed neural network are derived by M-matrix theory, analytic methods, and inequality techniques. Moreover, the exponential convergence rate index is estimated, which depends on the system parameters. The obtained results in this paper are less restrictive than previously known criteria. Two examples are given to show the effectiveness of the obtained results.

Early short-term management of control-actuator failures in a linear dynamic system

International Nuclear Information System (INIS)

Ben-Haim, Y.

1989-01-01

Early short-term management of malfunction attempts to maintain system stability during the early development stages of a failure. This is achieved in two stages. First, the failure is partially diagnosed by comparing observed system behavior against the performance expected for each of the selected set of hypothesized malfunctions. Second, the normal controller is replaced by a compensatory controller whose aim is to maintain system stability while compensating for the failure. Malfunctions involving control actuators are studied here. The aim of this study is to develop a technique for choosing the set of hypothesized failures and compensatory controllers which assure that the state of the system remains within specified bounds for a given duration after initiation of failure, regardless of the precise temporal development of the failure

On Stabilization of Nonautonomous Nonlinear Systems

International Nuclear Information System (INIS)

Bogdanov, A. Yu.

2008-01-01

The procedures to obtain the sufficient conditions of asymptotic stability for nonlinear nonstationary continuous-time systems are discussed. We consider different types of the following general controlled system: x = X(t,x,u) = F(t,x)+B(t,x)u, x(t 0 ) = x 0 . (*) The basis of investigation is limiting equations, limiting Lyapunov functions, etc. The improved concept of observability of the pair of functional matrices is presented. By these results the problem of synthesis of asymptotically stable control nonlinear nonautonomous systems (with linear parts) involving the quadratic time-dependent Lyapunov functions is solved as well as stabilizing a given unstable system with nonlinear control law.

Decomposition of heterogeneous organic matterand its long-term stabilization in soils

Science.gov (United States)

Sierra, Carlos A.; Harmon, Mark E.; Perakis, Steven S.

2011-01-01

Soil organic matter is a complex mixture of material with heterogeneous biological, physical, and chemical properties. Decomposition models represent this heterogeneity either as a set of discrete pools with different residence times or as a continuum of qualities. It is unclear though, whether these two different approaches yield comparable predictions of organic matter dynamics. Here, we compare predictions from these two different approaches and propose an intermediate approach to study organic matter decomposition based on concepts from continuous models implemented numerically. We found that the disagreement between discrete and continuous approaches can be considerable depending on the degree of nonlinearity of the model and simulation time. The two approaches can diverge substantially for predicting long-term processes in soils. Based on our alternative approach, which is a modification of the continuous quality theory, we explored the temporal patterns that emerge by treating substrate heterogeneity explicitly. The analysis suggests that the pattern of carbon mineralization over time is highly dependent on the degree and form of nonlinearity in the model, mostly expressed as differences in microbial growth and efficiency for different substrates. Moreover, short-term stabilization and destabilization mechanisms operating simultaneously result in long-term accumulation of carbon characterized by low decomposition rates, independent of the characteristics of the incoming litter. We show that representation of heterogeneity in the decomposition process can lead to substantial improvements in our understanding of carbon mineralization and its long-term stability in soils.

Probabilistic assessment of power system transient stability incorporating SMES

Energy Technology Data Exchange (ETDEWEB)

Fang, Jiakun, E-mail: Jiakun.Fang@gmail.com [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074 (China); Yao, Wei [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074 (China); Wen, Jinyu, E-mail: jinyu.wen@hust.edu.cn [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074 (China); Cheng, Shijie; Tang, Yuejin; Cheng, Zhuo [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074 (China)

2013-01-15

Highlights: ► Probabilistic study of power system with wind farm and SMES is proposed. ► Quantitative relationship between system stability and SMES capacity is given. ► System stability increases with the capacity of the SMES. ► System stability decreases with the penetration of wind power. ► Together with the cost function, the coil size is optimized. -- Abstract: This paper presents a stochastic-based approach to evaluate the probabilistic transient stability index of the power system incorporating the wind farm and the SMES. Uncertain factors include both sequence of disturbance in power grid and stochastic generation of the wind farm. The spectrums of disturbance in the grid as the fault type, the fault location, the fault clearing time and the automatic reclosing process with their probabilities of occurrence are used to calculate the probability indices, while the wind speed statistics and parameters of the wind generator are used in a Monte Carlo simulation to generate samples for the studies. With the proposed method, system stability is ”measured”. Quantitative relationship of penetration level, SMES coil size and system stability is established. Considering the stability versus coil size to be the production curve, together with the cost function, the coil size is optimized economically.

Probabilistic assessment of power system transient stability incorporating SMES

International Nuclear Information System (INIS)

Fang, Jiakun; Yao, Wei; Wen, Jinyu; Cheng, Shijie; Tang, Yuejin; Cheng, Zhuo

2013-01-01

Highlights: ► Probabilistic study of power system with wind farm and SMES is proposed. ► Quantitative relationship between system stability and SMES capacity is given. ► System stability increases with the capacity of the SMES. ► System stability decreases with the penetration of wind power. ► Together with the cost function, the coil size is optimized. -- Abstract: This paper presents a stochastic-based approach to evaluate the probabilistic transient stability index of the power system incorporating the wind farm and the SMES. Uncertain factors include both sequence of disturbance in power grid and stochastic generation of the wind farm. The spectrums of disturbance in the grid as the fault type, the fault location, the fault clearing time and the automatic reclosing process with their probabilities of occurrence are used to calculate the probability indices, while the wind speed statistics and parameters of the wind generator are used in a Monte Carlo simulation to generate samples for the studies. With the proposed method, system stability is ”measured”. Quantitative relationship of penetration level, SMES coil size and system stability is established. Considering the stability versus coil size to be the production curve, together with the cost function, the coil size is optimized economically

Some results on stability of difference systems

Directory of Open Access Journals (Sweden)

Xiao-Song Yang

2002-01-01

Full Text Available This paper presents some new results on existence and stability of equilibrium or periodic points for difference systems. First sufficient conditions of existence of asymptotically stable equilibrium point as well as the asymptotic stability of given equilibrium point are given for second order or delay difference systems. Then some similar results on existence of asymptotically stable periodic (equilibrium points to general difference systems are presented.

Enhanced stability of car-following model upon incorporation of short-term driving memory

Science.gov (United States)

Liu, Da-Wei; Shi, Zhong-Ke; Ai, Wen-Huan

2017-06-01

Based on the full velocity difference model, a new car-following model is developed to investigate the effect of short-term driving memory on traffic flow in this paper. Short-term driving memory is introduced as the influence factor of driver's anticipation behavior. The stability condition of the newly developed model is derived and the modified Korteweg-de Vries (mKdV) equation is constructed to describe the traffic behavior near the critical point. Via numerical method, evolution of a small perturbation is investigated firstly. The results show that the improvement of this new car-following model over the previous ones lies in the fact that the new model can improve the traffic stability. Starting and breaking processes of vehicles in the signalized intersection are also investigated. The numerical simulations illustrate that the new model can successfully describe the driver's anticipation behavior, and that the efficiency and safety of the vehicles passing through the signalized intersection are improved by considering short-term driving memory.

Verifying Stability of Dynamic Soft-Computing Systems

Science.gov (United States)

Wen, Wu; Napolitano, Marcello; Callahan, John

1997-01-01

Soft computing is a general term for algorithms that learn from human knowledge and mimic human skills. Example of such algorithms are fuzzy inference systems and neural networks. Many applications, especially in control engineering, have demonstrated their appropriateness in building intelligent systems that are flexible and robust. Although recent research have shown that certain class of neuro-fuzzy controllers can be proven bounded and stable, they are implementation dependent and difficult to apply to the design and validation process. Many practitioners adopt the trial and error approach for system validation or resort to exhaustive testing using prototypes. In this paper, we describe our on-going research towards establishing necessary theoretic foundation as well as building practical tools for the verification and validation of soft-computing systems. A unified model for general neuro-fuzzy system is adopted. Classic non-linear system control theory and recent results of its applications to neuro-fuzzy systems are incorporated and applied to the unified model. It is hoped that general tools can be developed to help the designer to visualize and manipulate the regions of stability and boundedness, much the same way Bode plots and Root locus plots have helped conventional control design and validation.

Groundwater flow system stability in shield settings a multi-disciplinary approach

International Nuclear Information System (INIS)

Jensen, M.R.; Goodwin, B.W.

2004-01-01

Within the Deep Geologic Repository Technology Program (DGRTP) several Geoscience activities are focused on advancing the understanding of groundwater flow system evolution and geochemical stability in a Shield setting as affected by long-term climate change. A key aspect is developing confidence in predictions of groundwater flow patterns and residence times as they relate to the safety of a Deep Geologic Repository for used nuclear fuel waste. A specific focus in this regard has been placed on constraining redox stability and groundwater flow system dynamics during the Pleistocene. Attempts are being made to achieve this through a coordinated multi-disciplinary approach intent on; i) demonstrating coincidence between independent geo-scientific data; ii) improving the traceability of geo-scientific data and its interpretation within a conceptual descriptive model(s); iii) improving upon methods to assess and demonstrate robustness in flow domain prediction(s) given inherent flow domain uncertainties (i.e. spatial chemical/physical property distributions; boundary conditions) in time and space; and iv) improving awareness amongst geo-scientists as to the utility various geo-scientific data in supporting a repository safety case. Coordinated by the DGRTP, elements of this program include the development of a climate driven Laurentide ice-sheet model to constrain the understanding of time rate of change in boundary conditions most affecting the groundwater flow domain and its evolution. Further work has involved supporting WRA Paleo-hydrogeologic studies in which constrained thermodynamic analyses coupled with field studies to characterize the paragenesis of fracture infill mineralogy are providing evidence to premise understandings of possible depth of penetration by oxygenated glacial recharge. In parallel. numerical simulations have been undertaken to illustrate aspect of groundwater flow system stability and evolution in a Shield setting. Such simulations

Potential and flux field landscape theory. I. Global stability and dynamics of spatially dependent non-equilibrium systems.

Science.gov (United States)

Wu, Wei; Wang, Jin

2013-09-28

We established a potential and flux field landscape theory to quantify the global stability and dynamics of general spatially dependent non-equilibrium deterministic and stochastic systems. We extended our potential and flux landscape theory for spatially independent non-equilibrium stochastic systems described by Fokker-Planck equations to spatially dependent stochastic systems governed by general functional Fokker-Planck equations as well as functional Kramers-Moyal equations derived from master equations. Our general theory is applied to reaction-diffusion systems. For equilibrium spatially dependent systems with detailed balance, the potential field landscape alone, defined in terms of the steady state probability distribution functional, determines the global stability and dynamics of the system. The global stability of the system is closely related to the topography of the potential field landscape in terms of the basins of attraction and barrier heights in the field configuration state space. The effective driving force of the system is generated by the functional gradient of the potential field alone. For non-equilibrium spatially dependent systems, the curl probability flux field is indispensable in breaking detailed balance and creating non-equilibrium condition for the system. A complete characterization of the non-equilibrium dynamics of the spatially dependent system requires both the potential field and the curl probability flux field. While the non-equilibrium potential field landscape attracts the system down along the functional gradient similar to an electron moving in an electric field, the non-equilibrium flux field drives the system in a curly way similar to an electron moving in a magnetic field. In the small fluctuation limit, the intrinsic potential field as the small fluctuation limit of the potential field for spatially dependent non-equilibrium systems, which is closely related to the steady state probability distribution functional, is

Engineered Barrier System - Long-term Stability of Buffer and Backfill. Synthesis and extended abstracts

Energy Technology Data Exchange (ETDEWEB)

Apted, Mick; Arthur, Randy [Monitor Scientific LLC, Denver, CO (United States); Savage, Dave [Quintessa Ltd., Nottingham (GB)] (eds.)

2005-09-15

SKI is preparing to review the license applications being developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) for an encapsulation plant and a deep repository for the geological disposal of spent nuclear fuel. As part of its preparation, SKI is conducting a series of technical workshops on key aspects of the Engineered Barrier System (EBS) of the repository. This workshop concerns the longterm stability of the buffer and the backfill. Previous workshops have addressed the overall concept for long-term integrity of the EBS, the manufacturing, testing and QA of the EBS and the performance confirmation for the EBS. The goal of this work is to achieve a comprehensive overview of all aspects of SKB's EBS work prior to the handling of forthcoming license applications. The reports from the EBS workshops will be used as one important basis in future review work. The workshops involve the gathering of a sufficient number of independent experts in different subjects of relevance to the particular aspect of EBS. A workshop starts with presentations and discussions among these experts. Following this, SKB presents recent results and responds to questions as part of an informal hearing. Finally, the independent experts and the SKI staff examine the SKB responses from different viewpoints. This report aims to summarise the issues discussed at the buffer and backfill workshop and to extract the essential viewpoints that have been expressed. The report is not a comprehensive record of the discussions and individual statements made by workshop participants should be regarded as opinions rather than proven facts. This reports includes apart from the workshop synthesis, questions to SKB identified prior or during the workshop, and extended abstracts for introductory presentations.

Engineered Barrier System - Long-term Stability of Buffer and Backfill. Synthesis and extended abstracts

International Nuclear Information System (INIS)

Apted, Mick; Arthur, Randy; Savage, Dave

2005-09-01

SKI is preparing to review the license applications being developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) for an encapsulation plant and a deep repository for the geological disposal of spent nuclear fuel. As part of its preparation, SKI is conducting a series of technical workshops on key aspects of the Engineered Barrier System (EBS) of the repository. This workshop concerns the longterm stability of the buffer and the backfill. Previous workshops have addressed the overall concept for long-term integrity of the EBS, the manufacturing, testing and QA of the EBS and the performance confirmation for the EBS. The goal of this work is to achieve a comprehensive overview of all aspects of SKB's EBS work prior to the handling of forthcoming license applications. The reports from the EBS workshops will be used as one important basis in future review work. The workshops involve the gathering of a sufficient number of independent experts in different subjects of relevance to the particular aspect of EBS. A workshop starts with presentations and discussions among these experts. Following this, SKB presents recent results and responds to questions as part of an informal hearing. Finally, the independent experts and the SKI staff examine the SKB responses from different viewpoints. This report aims to summarise the issues discussed at the buffer and backfill workshop and to extract the essential viewpoints that have been expressed. The report is not a comprehensive record of the discussions and individual statements made by workshop participants should be regarded as opinions rather than proven facts. This reports includes apart from the workshop synthesis, questions to SKB identified prior or during the workshop, and extended abstracts for introductory presentations

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.

Long Term Evaluation of Yield Stability Trend for Cereal Crops in Iran

Directory of Open Access Journals (Sweden)

mehdi nassiri mahalati

2016-05-01

Full Text Available During the last few decades cereals yield have increased drastically at the national level however, information about yield stability and its resistance to annual environmental variability are scare. In this study long term stability of grin yield of wheat, barley, rice, corn and overall cereals in Iran were evaluated during a 40-year period (1971-2011. Stability analysis was conducted using two different methods. In the first method the residuals of regression between crop yield and time (years were calculated as stability index. For this different segmented regression models including linear, bi-linear and tri-linear were fitted to yield trend data and the best model for each crop was selected based on statistical measures. Absolute residuals (the difference between actual and predicted yields for each year as well as relative residuals (absolute residuals as percent of predicted yield were estimated. In the second method yield stability was estimated from the slope of the regression line between average annual yield of all cereals (environmental index and the yield of each crop in the same year. Results indicted that in wheat and barley absolute and relative residuals were increased during the study period leading to reduction of stability despite considerable yield increment. However, for rice and corn residuals followed a decreasing trend and therefore yield stability of these crops was increased during the last 40 years. The same result was obtained with the environmental index but in this method reduction of yield stability in barley was lower than wheat. Based on the results, yield and yield stability of cereals crops in Iran increased during the last 40 years. However, the percentage increase in stability is lower than that of yield. Application of nitrogen fertilizers was led to reduction in stability. Yield stability of wheat, barley, rice, corn and overall cereals was improved with increasing their cultivated area.

Stability improvement of induction generator-based wind turbine systems

DEFF Research Database (Denmark)

Chen, Zhe; Hu, Y.; Blaabjerg, Frede

2007-01-01

The stability improvement of induction-generator-based wind turbine systems under power system fault conditions has been studied. Two types of generators are considered, namely rotor short-circuited induction generators and dynamic slip-controlled wound rotor induction generators. The factors...... affecting the stability are analysed. The characteristics of the induction-generator-based wind turbines are described, and possible methods of improving stability of the wind generators are discussed. The system modelling is presented, and then the discussed methods of improving stability are investigated...

Power system stabilizers based on modern control techniques

Energy Technology Data Exchange (ETDEWEB)

Malik, O P; Chen, G P; Zhang, Y; El-Metwally, K [Calgary Univ., AB (Canada). Dept. of Electrical and Computer Engineering

1994-12-31

Developments in digital technology have made it feasible to develop and implement improved controllers based on sophisticated control techniques. Power system stabilizers based on adaptive control, fuzzy logic and artificial networks are being developed. Each of these control techniques possesses unique features and strengths. In this paper, the relative performance of power systems stabilizers based on adaptive control, fuzzy logic and neural network, both in simulation studies and real time tests on a physical model of a power system, is presented and compared to that of a fixed parameter conventional power system stabilizer. (author) 16 refs., 45 figs., 3 tabs.

Effects of SMES units on power system stability

International Nuclear Information System (INIS)

Byerly, R.T.; Juves, J.A.

1980-01-01

A mathematical model suitable for representing SMES units in power system stability studies has been developed and incorporated into an existing large-scale stability program. Demonstration studies have been performed which emphasize the use of SMES units to improve the damping of oscillations associated with synchronizing power flow among generators. The capability exists to conduct stability studies of large systems which include SMES units

Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments

Czech Academy of Sciences Publication Activity Database

Čížek, Martin; Hucl, Václav; Hrabina, Jan; Šmíd, Radek; Mikel, Břetislav; Lazar, Josef; Číp, Ondřej

2014-01-01

Roč. 14, č. 1 (2014), s. 1757-1770 ISSN 1424-8220 R&D Projects: GA ČR GPP102/11/P819; GA ČR GAP102/10/1813; GA MŠk ED0017/01/01; GA MŠk EE2.4.31.0016 Institutional support: RVO:68081731 Keywords : optical frequency combs * digital signal processing * software-defined radio * beat note * stabilization * long-term operation Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.245, year: 2014

Delay-Dependent Stability Analysis of Uncertain Fuzzy Systems with State and Input Delays under Imperfect Premise Matching

Directory of Open Access Journals (Sweden)

Zejian Zhang

2013-01-01

Full Text Available This paper discusses the stability and stabilization problem for uncertain T-S fuzzy systems with time-varying state and input delays. A new augmented Lyapunov function with an additional triple-integral term and different membership functions of the fuzzy models and fuzzy controllers are introduced to derive the stability criterion, which is less conservative than the existing results. Moreover, a new flexibility design method is also provided. Some numerical examples are given to demonstrate the effectiveness and less conservativeness of the proposed method.

Ecotoxicological evaluation of the short term effects of fresh and stabilized textile sludges before application in forest soil restoration

International Nuclear Information System (INIS)

Rosa, Edson V.C.; Giuradelli, Thayse M.; Correa, Albertina X.R.; Roerig, Leonardo R.; Schwingel, Paulo R.; Resgalla, Charrid; Radetski, Claudemir M.

2007-01-01

The short term (eco)toxicity potential of fresh and stabilized textile sludges, as well as the short term (eco)toxicity of leachates obtained from both fresh and stabilized textile sludges, was evaluated by a battery of toxicity tests carried out with bacteria, algae, daphnids, fish, earthworms, and higher plants. The (eco)toxicological results showed that, after 120 d of stabilization, the experimental loading ratio of 25% sludge:75% soil (v/v) (equivalent to 64.4 ton/ha) did not significantly increase toxicity effects and increased significantly the biomass yield for earthworms and higher plants. The rank of biological sensitivity endpoints was: Algae ∼ Plant biomass > Plant germination ∼ Daphnids > Bacteria ∼ Fish > Annelids. The lack of short term toxicity effects and the stimulant effect observed with higher plants and earthworms are good indications of the fertilizer/conditioner potential of this industrial waste, which after stabilization can be used in the restoration of a non-productive forest soil. - Short term ecotoxicity evaluation of textile sludge showed that stabilized sludge can be used in the restoration of a non-productive forest soil

Stabilization at almost arbitrary points for chaotic systems

International Nuclear Information System (INIS)

Huang, C.-S.; Lian, K.-Y.; Su, C.-H.; Wu, J.-W.

2008-01-01

We consider how to design a feasible control input for chaotic systems via a suitable input channel to achieve the stabilization at arbitrary points. Regarding the nonlinear systems without naturally defined input vectors, we propose a local stabilization controller which works for almost arbitrary points. Subsequently, according to topologically transitive property for chaotic systems, the feedback control force is activated only when the trajectory passes through the neighboring region of the regulated point. Hence the global stabilization is achieved whereas the control effort of the hybrid controller is extremely low

Global asymptotic stability of bistable traveling fronts in reaction-diffusion systems and their applications to biological models

International Nuclear Information System (INIS)

Wu Shiliang; Li Wantong

2009-01-01

This paper deals with the global asymptotic stability and uniqueness (up to translation) of bistable traveling fronts in a class of reaction-diffusion systems. The known results do not apply in solving these problems because the reaction terms do not satisfy the required monotone condition. To overcome the difficulty, a weak monotone condition is proposed for the reaction terms, which is called interval monotone condition. Under such a weak monotone condition, the existence and comparison theorem of solutions is first established for reaction-diffusion systems on R by appealing to the theory of abstract differential equations. The global asymptotic stability and uniqueness (up to translation) of bistable traveling fronts are then proved by the elementary super- and sub-solution comparison and squeezing methods for nonlinear evolution equations. Finally, these abstract results are applied to a two species competition-diffusion model and a system modeling man-environment-man epidemics.

Long-term stability of bentonite. A literature review

International Nuclear Information System (INIS)

Laine, H.; Karttunen, P.

2010-07-01

The long-term thermodynamic stability of the bentonite buffer in the evolving chemical, thermal and hydrological conditions at Olkiluoto has been evaluated by reviewing the relevant experimental data and natural occurrences of bentonite that could serve as analogues for the long-term bentonite stability in the expected repository conditions, especially focussing on mineral transformations due, among others, to thermal effects including cementation. Natural occurrences with stable smectite have been reviewed and compared with Olkiluoto groundwater compositions at present and during the expected hydrogeochemical evolution of the repository. Alteration of the bentonite buffer is expected to be insignificant for natural groundwater conditions at present and for the evolving groundwater conditions at the expected thermal boundary conditions caused by the heat induced from the fuel canisters ( + and SiO 2 and elevated pH due to degradation and dissolution processes. These may alter the conditions in the repository that may favour alteration and cementation processes. The amounts of foreign materials to be used in the repository will be updated along with the progress of the construction. Also the information on their impact on the barriers needs to be evaluated in more detail, including the degradation rate, mobility or dilution of the foreign materials in the repository environment. The exchangeable cation composition of the buffer bentonite is expected to equilibrate with the surrounding groundwater during and after saturation. This process is expected to lead towards Ca-dominant exchangeable cation composition within the montmorillonite interlayer spaces in the buffer. In general it seems that the transformation towards Ca-dominated composition would favour the long-term stability of the buffer as Ca-dominated smectite (compared to Na-dominated type) has larger water retention capacity and anion incorporation to the interlayer space of montmorillonite is more

Neural Network Based Finite-Time Stabilization for Discrete-Time Markov Jump Nonlinear Systems with Time Delays

Directory of Open Access Journals (Sweden)

Fei Chen

2013-01-01

Full Text Available This paper deals with the finite-time stabilization problem for discrete-time Markov jump nonlinear systems with time delays and norm-bounded exogenous disturbance. The nonlinearities in different jump modes are parameterized by neural networks. Subsequently, a linear difference inclusion state space representation for a class of neural networks is established. Based on this, sufficient conditions are derived in terms of linear matrix inequalities to guarantee stochastic finite-time boundedness and stochastic finite-time stabilization of the closed-loop system. A numerical example is illustrated to verify the efficiency of the proposed technique.

Long-Term Stability of New Co-Amorphous Drug Binary Systems: Study of Glass Transitions as a Function of Composition and Shelf Time

Directory of Open Access Journals (Sweden)

Luz María Martínez

2016-12-01

Full Text Available The amorphous state is of particular interest in the pharmaceutical industry due to the higher solubility that amorphous active pharmaceutical ingredients show compared to their respective crystalline forms. Due to their thermodynamic instability, drugs in the amorphous state tend to recrystallize; in order to avoid crystallization, it has been a common strategy to add a second component to hinder the crystalline state and form a thermally stable co-amorphous system, that is to say, an amorphous binary system which retains its amorphous structure. The second component can be a small molecule excipient (such as a sugar or an aminoacid or a second drug, with the advantage that a second active pharmaceutical ingredient could be used for complementary or combined therapeutic purposes. In most cases, the compositions studied are limited to 1:1, 2:1 and 1:2 molar ratios, leaving a gap of information about phase transitions and stability on the amorphous state in a wider range of compositions. In the present work, a study of novel co–amorphous formulations in which the selection of the active pharmaceutical ingredients was made according to the therapeutic effect is presented. Resistance against crystallization and behavior of glass transition temperature ( T g were studied through calorimetric measurements as a function of composition and shelf time. It was found that binary formulations with T g temperatures higher than those of pure components presented long-term thermal stability. In addition, significant increments of T g values, of as much as 15 ∘ C, were detected as a result of glass relaxation at room temperature during storage time; this behavior of glass transition has not been previously reported for co-amorphous drugs. Based on these results, it can be concluded that monitoring behavior of T g and relaxation processes during the first weeks of storage leads to a more objective evaluation of the thermomechanical stability of an amorphous

Long term stability of cannabis resin and cannabis extracts

DEFF Research Database (Denmark)

Lindholst, Christian

2010-01-01

  The aim of the present study was to investigate the stability of cannabinoids in cannabis resin slabs and cannabis extracts upon long-term storage. The levels of tetrahydrocannabinol (THC), cannabinol (CBN), cannabidiol (CBD) and cannabigerol (CBG) on both neutral and acidic form were measured...... stored in extracted form at room temperature the degradation rate of acidic THC increased significantly relative to resin material with concentration halve-lives of 35 and 91 days in daylight and darkness, respectively. Once cannabis material is extracted into organic solvents, care should be taken...

The driving forces of stability. Exploring the nature of long-term bureaucracy-interest group interactions

NARCIS (Netherlands)

Braun, C.H.J.M.

2013-01-01

This article explores the nature of long-term interactions between bureaucrats and interest groups by examining two behavioral logics associated with stability in public policy making. In addition to the implicit short-term strategic choices that usually feature in resource-exchange explanations of

Stability of impulsive systems driven by renewal processes

NARCIS (Netherlands)

Guerreiro Tome Antunes, D.J.; Hespanha, J.P.; Silvestre, C.J.

2009-01-01

Necessary and sufficient conditions are provided for stochastic stability and mean exponential stability of impulsive systems with jumps triggered by a renewal process, that is, the intervals between jumps are independent and identically distributed. The conditions for stochastic stability can be

The Nature of Stability in Replicating Systems

Directory of Open Access Journals (Sweden)

Addy Pross

2011-02-01

Full Text Available We review the concept of dynamic kinetic stability, a type of stability associated specifically with replicating entities, and show how it differs from the well-known and established (static kinetic and thermodynamic stabilities associated with regular chemical systems. In the process we demonstrate how the concept can help bridge the conceptual chasm that continues to separate the physical and biological sciences by relating the nature of stability in the animate and inanimate worlds, and by providing additional insights into the physicochemical nature of abiogenesis.

Stabilization of model-based networked control systems

Energy Technology Data Exchange (ETDEWEB)

Miranda, Francisco [CIDMA, Universidade de Aveiro, Aveiro (Portugal); Instituto Politécnico de Viana do Castelo, Viana do Castelo (Portugal); Abreu, Carlos [Instituto Politécnico de Viana do Castelo, Viana do Castelo (Portugal); CMEMS-UMINHO, Universidade do Minho, Braga (Portugal); Mendes, Paulo M. [CMEMS-UMINHO, Universidade do Minho, Braga (Portugal)

2016-06-08

A class of networked control systems called Model-Based Networked Control Systems (MB-NCSs) is considered. Stabilization of MB-NCSs is studied using feedback controls and simulation of stabilization for different feedbacks is made with the purpose to reduce the network trafic. The feedback control input is applied in a compensated model of the plant that approximates the plant dynamics and stabilizes the plant even under slow network conditions. Conditions for global exponential stabilizability and for the choosing of a feedback control input for a given constant time between the information moments of the network are derived. An optimal control problem to obtain an optimal feedback control is also presented.

Long-term impact of reduced tillage and residue management on soil carbon stabilization: Implications for conservation agriculture on contrasting soils

OpenAIRE

Chivenge, P.P.; Murwira, H.K.; Giller, K.E.; Mapfumo, P.; Six, J.

2007-01-01

Metadata only record The long-term effects of tillage system and residue management on soil organic carbon stabilization are studied in two tropical soils in Zimbabwe, a red clay and a sandy soil. The four tillage systems evaluated were conventional tillage (CT), mulch ripping (MR), clean ripping (CR) and tied ridging (TR). Soil organic carbon (SOC) content was measured for each size fraction as well as total SOC. Based on the findings, the authors conclude that residue management - mainta...

An investigation on the chemical stability and a novel strategy for long-term stabilization of diphenylalanine nanostructures in aqueous solution

Directory of Open Access Journals (Sweden)

H. Nezammahalleh

2015-01-01

Full Text Available The stability of diphenylalanine (FF microwires and microtubes in phosphate buffer solution was investigated and a novel strategy was developed for their chemical stabilization. This stability investigation was carried out by optical microscopy and by high performance liquid chromatography (HPLC. These microstructures dissolve in the solution depending upon their degree of FF saturation. The dissolution mechanisms of the structures in kinetically limited processes were found by accurately fitting the experimental dissolution data to a theoretical kinetic equation. The dissolution data were well fitted to the particular Avrami-Erofe’ev kinetic expression (R2 > 0.98. These findings suggest that the structures can be stabilized by a decrease in the hydration of the constituent molecules thorough a chemical conformational induced transition upon heat treatment. The stable microtubes were fabricated in a novel three step procedure consisting of the reduction of silver ions in unstable FF microtubes by a citrate reductant, the stabilization by chemical conformational induced transition upon heat treatment, and the consequent oxidation of the reduced silver by a persulfate oxidant. These materials were characterized by electron microscopy and powder X-ray diffraction techniques. The long-term stability of both structures was also confirmed by optical microscopy and HPLC.

Stability analysis of coupled torsional vibration and pressure in oilwell drillstring system

Science.gov (United States)

Toumi, S.; Beji, L.; Mlayeh, R.; Abichou, A.

2018-01-01

To address security issues in oilwell drillstring system, the drilling operation handling which is in generally not autonomous but ensured by an operator may be drill bit destructive or fatal for the machine. To control of stick-slip phenomenon, the drillstring control at the right speed taking only the drillstring vibration is not sufficient as the mud dynamics and the pressure change around the drill pipes cannot be neglected. A coupled torsional vibration and pressure model is presented, and the well-posedness problem is addressed. As a Partial Differential Equation-Ordinary Differential Equation (PDE-ODE) coupled system, and in order to maintain a non destructive downhole pressure, we investigate the control stability with and without the damping term in the wave PDE. In terms of, the torsional variable, the downhole pressure, and the annulus pressure, the coupled system equilibrium is shown to be exponentially stable.

Third-order least squares modelling of milling state term for improved computation of stability boundaries

Directory of Open Access Journals (Sweden)

C.G. Ozoegwu

2016-01-01

Full Text Available The general least squares model for milling process state term is presented. A discrete map for milling stability analysis that is based on the third-order case of the presented general least squares milling state term model is first studied and compared with its third-order counterpart that is based on the interpolation theory. Both numerical rate of convergence and chatter stability results of the two maps are compared using the single degree of freedom (1DOF milling model. The numerical rate of convergence of the presented third-order model is also studied using the two degree of freedom (2DOF milling process model. Comparison gave that stability results from the two maps agree closely but the presented map demonstrated reduction in number of needed calculations leading to about 30% savings in computational time (CT. It is seen in earlier works that accuracy of milling stability analysis using the full-discretization method rises from first-order theory to second-order theory and continues to rise to the third-order theory. The present work confirms this trend. In conclusion, the method presented in this work will enable fast and accurate computation of stability diagrams for use by machinists.

Functional Trait Changes, Productivity Shifts and Vegetation Stability in Mountain Grasslands during a Short-Term Warming.

Science.gov (United States)

Debouk, Haifa; de Bello, Francesco; Sebastià, Maria-Teresa

2015-01-01

Plant functional traits underlie vegetation responses to environmental changes such as global warming, and consequently influence ecosystem processes. While most of the existing studies focus on the effect of warming only on species diversity and productivity, we further investigated (i) how the structure of community plant functional traits in temperate grasslands respond to experimental warming, and (ii) whether species and functional diversity contribute to a greater stability of grasslands, in terms of vegetation composition and productivity. Intact vegetation turves were extracted from temperate subalpine grassland (highland) in the Eastern Pyrenees and transplanted into a warm continental, experimental site in Lleida, in Western Catalonia (lowland). The impacts of simulated warming on plant production and diversity, functional trait structure, and vegetation compositional stability were assessed. We observed an increase in biomass and a reduction in species and functional diversity under short-term warming. The functional structure of the grassland communities changed significantly, in terms of functional diversity and community-weighted means (CWM) for several traits. Acquisitive and fast-growing species with higher SLA, early flowering, erect growth habit, and rhizomatous strategy became dominant in the lowland. Productivity was significantly positively related to species, and to a lower extent, functional diversity, but productivity and stability after warming were more dependent on trait composition (CWM) than on diversity. The turves with more acquisitive species before warming changed less in composition after warming. Results suggest that (i) the short-term warming can lead to the dominance of acquisitive fast growing species over conservative species, thus reducing species richness, and (ii) the functional traits structure in grassland communities had a greater influence on the productivity and stability of the community under short-term warming

Functional Trait Changes, Productivity Shifts and Vegetation Stability in Mountain Grasslands during a Short-Term Warming.

Directory of Open Access Journals (Sweden)

Haifa Debouk

Full Text Available Plant functional traits underlie vegetation responses to environmental changes such as global warming, and consequently influence ecosystem processes. While most of the existing studies focus on the effect of warming only on species diversity and productivity, we further investigated (i how the structure of community plant functional traits in temperate grasslands respond to experimental warming, and (ii whether species and functional diversity contribute to a greater stability of grasslands, in terms of vegetation composition and productivity. Intact vegetation turves were extracted from temperate subalpine grassland (highland in the Eastern Pyrenees and transplanted into a warm continental, experimental site in Lleida, in Western Catalonia (lowland. The impacts of simulated warming on plant production and diversity, functional trait structure, and vegetation compositional stability were assessed. We observed an increase in biomass and a reduction in species and functional diversity under short-term warming. The functional structure of the grassland communities changed significantly, in terms of functional diversity and community-weighted means (CWM for several traits. Acquisitive and fast-growing species with higher SLA, early flowering, erect growth habit, and rhizomatous strategy became dominant in the lowland. Productivity was significantly positively related to species, and to a lower extent, functional diversity, but productivity and stability after warming were more dependent on trait composition (CWM than on diversity. The turves with more acquisitive species before warming changed less in composition after warming. Results suggest that (i the short-term warming can lead to the dominance of acquisitive fast growing species over conservative species, thus reducing species richness, and (ii the functional traits structure in grassland communities had a greater influence on the productivity and stability of the community under short-term

Boundary feedback stabilization of distributed parameter systems

DEFF Research Database (Denmark)

Pedersen, Michael

1988-01-01

The author introduces the method of pseudo-differential stabilization. He notes that the theory of pseudo-differential boundary operators is a fruitful approach to problems arising in control and stabilization theory of distributed-parameter systems. The basic pseudo-differential calculus can...

Study plan for research on long-term stability of geological environments in FY2009

International Nuclear Information System (INIS)

Yasue, Ken-ichi; Hanamuro, Takahiro; Kokubu, Yoko; Ishimaru, Tsuneari; Umeda, Koji

2009-09-01

The Japanese islands lie in a region of the Circum-Pacific orogenic belt characterized by active tectonics such as volcanism and earthquakes. The concept of geological disposal of HLW in Japan is based on a multi-barrier system which consists of the engineered barrier in the stable geological environments and the natural barrier. The natural phenomena which potentially affect the geological environments in tectonically active Japan are volcanism, faulting, uplift, denudation, climatic change, and sea-level change. Investigation technologies to evaluate their long-term stability of the geological environments have been developed. In fiscal year 2009, we continue researches to develop technologies for detecting latent geotectonic events in preliminary investigation. With regard to modelling technology, we plan to develop prediction models for evaluating the changes of geological environment (e.g., thermal, hydraulic, mechanical, and geochemical conditions) for long term. In addition to these, the development of dating techniques prerequisite for these studies is also carried out. (author)

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...

Australia; Financial System Stability Assessment, including Reports on the Observance of Standards and Codes on the following topics: Banking Supervision, Insurance Regulation, Securities Regulation, and Payment Systems

OpenAIRE

International Monetary Fund

2006-01-01

The Australian banking system, which holds approximately half of total financial systems assets, and is dominated by four major banks, is sound with high earnings, high asset growth, and low levels of problem assets. Stress tests did not reveal near-term stability concerns, suggesting the banking system is likely to be resilient to adverse shocks. Australia’s financial supervisory structure of prudential authority and market conduct authority is sound overall. The medium-term challenges facin...

Stochastic Stability for Time-Delay Markovian Jump Systems with Sector-Bounded Nonlinearities and More General Transition Probabilities

Directory of Open Access Journals (Sweden)

Dan Ye

2013-01-01

Full Text Available This paper is concerned with delay-dependent stochastic stability for time-delay Markovian jump systems (MJSs with sector-bounded nonlinearities and more general transition probabilities. Different from the previous results where the transition probability matrix is completely known, a more general transition probability matrix is considered which includes completely known elements, boundary known elements, and completely unknown ones. In order to get less conservative criterion, the state and transition probability information is used as much as possible to construct the Lyapunov-Krasovskii functional and deal with stability analysis. The delay-dependent sufficient conditions are derived in terms of linear matrix inequalities to guarantee the stability of systems. Finally, numerical examples are exploited to demonstrate the effectiveness of the proposed method.

Stability Analysis of Fractional-Order Nonlinear Systems with Delay

Directory of Open Access Journals (Sweden)

Yu Wang

2014-01-01

Full Text Available Stability analysis of fractional-order nonlinear systems with delay is studied. We propose the definition of Mittag-Leffler stability of time-delay system and introduce the fractional Lyapunov direct method by using properties of Mittag-Leffler function and Laplace transform. Then some new sufficient conditions ensuring asymptotical stability of fractional-order nonlinear system with delay are proposed firstly. And the application of Riemann-Liouville fractional-order systems is extended by the fractional comparison principle and the Caputo fractional-order systems. Numerical simulations of an example demonstrate the universality and the effectiveness of the proposed method.

Model predictive control of hybrid systems : stability and robustness

NARCIS (Netherlands)

Lazar, M.

2006-01-01

This thesis considers the stabilization and the robust stabilization of certain classes of hybrid systems using model predictive control. Hybrid systems represent a broad class of dynamical systems in which discrete behavior (usually described by a finite state machine) and continuous behavior

Global exponential stability of impulsive fuzzy cellular neural networks with mixed delays and reaction-diffusion terms

International Nuclear Information System (INIS)

Wang Xiaohu; Xu Daoyi

2009-01-01

In this paper, the global exponential stability of impulsive fuzzy cellular neural networks with mixed delays and reaction-diffusion terms is considered. By establishing an integro-differential inequality with impulsive initial condition and using the properties of M-cone and eigenspace of the spectral radius of nonnegative matrices, several new sufficient conditions are obtained to ensure the global exponential stability of the equilibrium point for fuzzy cellular neural networks with delays and reaction-diffusion terms. These results extend and improve the earlier publications. Two examples are given to illustrate the efficiency of the obtained results.

An equivalent condition for stability properties of Lotka-Volterra systems

International Nuclear Information System (INIS)

Chu Tianguang

2007-01-01

We give a solvable Lie algebraic condition for the equivalence of four typical stability notions (asymptotic stability, D-stability, total stability, and Volterra-Lyapunov stability) concerning Lotka-Volterra systems. Our approach makes use of the decomposition of the interaction matrix into symmetric and skew-symmetric parts, which may be related to the cooperative and competitive interaction pattern of a Lotka-Volterra system. The present result covers a known condition and can yield a larger set of interaction matrices for equivalence of the stability properties

Interplay between black carbon and minerals contributes to long term carbon stabilization and mineral transformation

Science.gov (United States)

Liang, B.; Weng, Y. T.; Wang, C. C.; Chiang, C. C.; Liu, C. C.; Lehmann, J.

2017-12-01

Black carbon receives increasing global wide research attention due to its role in carbon sequestration, soil fertility enhancement and remediation application. Generally considered chemically stable in bulk, the reactive surface of BC can interplays with minerals and form strong chemical bondage, which renders physical protection of BC and contributes to its long term stabilization. Using historical BC-rich Amazonian Dark Earth (ADE), we probe the in-situ organo-mineral association and transformation of BC and minerals over a millennium scale using various synchrotron-based spectroscopic (XANES, FTIR) and microscopic (TXM) methods. Higher content of SRO minerals was found in BC-rich ADE compare to adjacent tropical soils. The iron signature found in BC-rich ADE was mainly ferrihydrite/lepidocrocite, a more reactive form of Fe compared to goethite, which was dominant in adjacent soil. Abundant nano minerals particles were observed in-situ associated with BC surface, in clusters and layers. The organo-mineral interaction lowers BC bioavailability and enhances its long-term stabilization in environment, while at the same time, transforms associated minerals into more reactive forms under rapid redox/weathering environment. The results suggest that mineral physical protection for BC sequestration may be more important than previous understanding. The scale up application of BC/biochar into agricultural systems and natural environments have long lasting impact on the in-situ transformation of associated minerals.

Robust design of decentralized power system stabilizers using meta-heuristic optimization techniques for multimachine systems

Directory of Open Access Journals (Sweden)

Jeevanandham Arumugam

2009-01-01

Full Text Available In this paper a classical lead-lag power system stabilizer is used for demonstration. The stabilizer parameters are selected in such a manner to damp the rotor oscillations. The problem of selecting the stabilizer parameters is converted to a simple optimization problem with an eigen value based objective function and it is proposed to employ simulated annealing and particle swarm optimization for solving the optimization problem. The objective function allows the selection of the stabilizer parameters to optimally place the closed-loop eigen values in the left hand side of the complex s-plane. The single machine connected to infinite bus system and 10-machine 39-bus system are considered for this study. The effectiveness of the stabilizer tuned using the best technique, in enhancing the stability of power system. Stability is confirmed through eigen value analysis and simulation results and suitable heuristic technique will be selected for the best performance of the system.

Power system small signal stability analysis and control

CERN Document Server

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

Stabilization of switched nonlinear systems with unstable modes

CERN Document Server

Yang, Hao; Cocquempot, Vincent

2014-01-01

This book provides its reader with a good understanding of the stabilization of switched nonlinear systems (SNS), systems that are of practical use in diverse situations: design of fault-tolerant systems in space- and aircraft; traffic control; and heat propagation control of semiconductor power chips. The practical background is emphasized throughout the book; interesting practical examples frequently illustrate the theoretical results with aircraft and spacecraft given particular prominence. Stabilization of Switched Nonlinear Systems with Unstable Modes treats several different subclasses of SNS according to the characteristics of the individual system (time-varying and distributed parameters, for example), the state composition of individual modes and the degree and distribution of instability in its various modes. Achievement and maintenance of stability across the system as a whole is bolstered by trading off between individual modes which may be either stable or unstable, or by exploiting areas of part...

On a program manifold's stability of one contour automatic control systems

Science.gov (United States)

Zumatov, S. S.

2017-12-01

Methodology of analysis of stability is expounded to the one contour systems automatic control feedback in the presence of non-linearities. The methodology is based on the use of the simplest mathematical models of the nonlinear controllable systems. Stability of program manifolds of one contour automatic control systems is investigated. The sufficient conditions of program manifold's absolute stability of one contour automatic control systems are obtained. The Hurwitz's angle of absolute stability was determined. The sufficient conditions of program manifold's absolute stability of control systems by the course of plane in the mode of autopilot are obtained by means Lyapunov's second method.

Wind energy systems solutions for power quality and stabilization

CERN Document Server

Ali, Mohd Hasan

2012-01-01

Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases--and wind energy is a free, renewable resource. However, the induction machines commonly used as wind generators have stability problems similar to the transient stability of synchronous machines. To minimize power, frequency, and voltage fluctuations caused by network faults or random wind speed variations, control mechanisms are necessary. Wind Energy Systems: Solutions for Power Quality and Stabilization clearly explains how to solve stability and power quality issues of wind generator systems. Covering

Power stability methods for parallel systems

International Nuclear Information System (INIS)

Wallach, Y.

1988-01-01

Parallel-Processing Systems are already commercially available. This paper shows that if one of them - the Alternating Sequential Parallel, or ASP system - is applied to network stability calculations it will lead to a higher speed of solution. The ASP system is first described and is then shown to be cheaper, more reliable and available than other parallel systems. Also, no deadlock need be feared and the speedup is normally very high. A number of ASP systems were already assembled (the SMS systems, Topps, DIRMU etc.). At present, an IBM Local Area Network is being modified so that it too can work in the ASP mode. Existing ASP systems were programmed in Fortran or assembly language. Since newer systems (e.g. DIRMU) are programmed in Modula-2, this language can be used. Stability analysis is based on solving nonlinear differential and algebraic equations. The algorithm for solving the nonlinear differential equations on ASP, is described and programmed in Modula-2. The speedup is computed and is shown to be almost optimal

Stability and delay sensitivity of neutral fractional-delay systems.

Science.gov (United States)

Xu, Qi; Shi, Min; Wang, Zaihua

2016-08-01

This paper generalizes the stability test method via integral estimation for integer-order neutral time-delay systems to neutral fractional-delay systems. The key step in stability test is the calculation of the number of unstable characteristic roots that is described by a definite integral over an interval from zero to a sufficient large upper limit. Algorithms for correctly estimating the upper limits of the integral are given in two concise ways, parameter dependent or independent. A special feature of the proposed method is that it judges the stability of fractional-delay systems simply by using rough integral estimation. Meanwhile, the paper shows that for some neutral fractional-delay systems, the stability is extremely sensitive to the change of time delays. Examples are given for demonstrating the proposed method as well as the delay sensitivity.

Formulation, physicochemical characterization and stability study of lithium-loaded microemulsion system.

Science.gov (United States)

Mouri, Abdelkader; Legrand, Philippe; El Ghzaoui, Abdeslam; Dorandeu, Christophe; Maurel, Jean Claude; Devoisselle, Jean-Marie

2016-04-11

Lithium biocompatible microemulsion based on Peceol(®), lecithin, ethanol and water was studied in attempt to identify the optimal compositions in term of drug content, physicochemical properties and stability. Lithium solubilization in microemulsion was found to be compatible with a drug-surfactant binding model. Lithium ions were predominantly solubilized within lecithin head group altering significantly the interfacial properties of the system. Pseudo-ternary phase diagrams of drug free and drug loaded microemulsions were built at constant ethanol/lecithin weight ratio (40/60). Lithium loaded microemulsion has totally disappeared in the Peceol(®) rich part of phase diagram; critical fractions of lecithin and ethanol were required for the formation of stable microemulsion. The effect of lithium concentration on the properties and physical stability of microemulsions were studied using microscopy, Karl Fischer titrations, rheology analyses, conductivity measurements and centrifugation tests. The investigated microemulsions were found to be stable under accelerated storage conditions. The systems exhibited low viscosity and behaved as Newtonian fluid and no structural transition was shown. Copyright © 2016 Elsevier B.V. All rights reserved.

Stability Tests of Positive Fractional Continuous-time Linear Systems with Delays

Directory of Open Access Journals (Sweden)

Tadeusz Kaczorek

2013-06-01

Full Text Available Necessary and sufficient conditions for the asymptotic stability of positive fractional continuous-time linear systems with many delays are established. It is shown that: 1 the asymptotic stability of the positive fractional system is independent of their delays, 2 the checking of the asymptotic stability of the positive fractional systems with delays can be reduced to checking of the asymptotic stability of positive standard linear systems without delays.

Morocco; Financial System Stability Assessment

OpenAIRE

International Monetary Fund

2003-01-01

The Financial System Stability Assessment of Morocco reviews the reform program that is aimed at establishing a modern, market-oriented financial system that optimizes the mobilization of savings and the allocation of financial resources. It reviews the modernization of the banking sector and the development of competition within the sector, development of financial markets, and removal of constraints on financial system activity. It also provides reports on the Observance of Standards and Co...

A MARTe based simulator for the JET Vertical Stabilization system

Energy Technology Data Exchange (ETDEWEB)

Bellizio, Teresa, E-mail: teresa.bellizio@unina.it [Associazione EURATOM-ENEA-CREATE, University di Napoli Federico II, Via Claudio 21, 80125 Napoli (Italy); De Tommasi, Gianmaria; Risoli, Nicola; Albanese, Raffaele [Associazione EURATOM-ENEA-CREATE, University di Napoli Federico II, Via Claudio 21, 80125 Napoli (Italy); Neto, Andre [Associacao EURATOM/IST, Inst. de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior, Tecnico, P-1049-001 Lisboa (Portugal)

2011-10-15

Validation by means of simulation is a crucial step when developing real-time control systems. Modeling and simulation are an essential tool since the early design phase, when the control algorithms are designed and tested. This phase is commonly carried out in off-line environments such as Matlab and Simulink. A MARTe-based simulator has been recently developed to validate the new JET Vertical Stabilization (VS) system. MARTe is the multi-thread framework used at JET to deploy hard real-time control systems. This paper presents the software architecture of the MARTe-based simulator and it shows how this tool has been effectively used to evaluate the effects of Edge Localized Modes (ELMs) on the VS system. By using the simulator it is possible to analyze different plasma configurations, extrapolating the limit of the new vertical amplifier in terms of the energy of the largest rejectable ELM.

Review of Power System Stability with High Wind Power Penetration

DEFF Research Database (Denmark)

Hu, Rui; Hu, Weihao; Chen, Zhe

2015-01-01

analyzing methods and stability improvement approaches. With increasing wind power penetration, system balancing and the reduced inertia may cause a big threaten for stable operation of power systems. To mitigate or eliminate the wind impacts for high wind penetration systems, although the practical......This paper presents an overview of researches on power system stability with high wind power penetration including analyzing methods and improvement approaches. Power system stability issues can be classified diversely according to different considerations. Each classified issue has special...... and reliable choices currently are the strong outside connections or sufficient reserve capacity constructions, many novel theories and approaches are invented to investigate the stability issues, looking forward to an extra-high penetration or totally renewable resource based power systems. These analyzing...

Stabilization of Teleoperation Systems with Communication Delays: An IMC Approach

Directory of Open Access Journals (Sweden)

Yuling Li

2018-01-01

Full Text Available The presence of time delays in communication introduces a limitation to the stability of bilateral teleoperation systems. This paper considers internal model control (IMC design of linear teleoperation system with time delays, and the stability of the closed-loop system is analyzed. It is shown that the stability is guaranteed delay-independently. The passivity assumption for external forces is removed for the proposed design of teleoperation systems. The behavior of the resulting teleoperation system is illustrated by simulations.

Asymptotic stabilization of nonlinear systems using state feedback

International Nuclear Information System (INIS)

D'Attellis, Carlos

1990-01-01

This paper studies the design of state-feedback controllers for the stabilization of single-input single-output nonlinear systems x = f(x) + g(x)u, y = h(x). Two approaches for the stabilization problem are given; the asymptotic stability is achieved by means of: a) nonlinear state feedback: two nonlinear feedbacks are used; the first separates the system in a controllable linear part and in the zeros-dynamic part. The second feedback generates an asymptotically stable equilibrium on the manifold where this dynamics evolves; b) nonlinear dynamic feedback: conditions are established under which the system can follow the output of a completely controllable bilinear system which uses bounded controls. This fact enables the system to reach, using bounded controls too, a desired output value in finite time. As this value corresponds to a state that lays in the attraction basin of a stable equilibrium with the same output, the system evolves to that point. The two methods are illustrated by examples. (Author) [es

A study of offshore wind HVDC system stability and control

Energy Technology Data Exchange (ETDEWEB)

Liu, Hanchao; Sun, Jian [Rensselaer Polytechnic Institute, Troy, NY (United States). Dept. of Electrical, Computer and Systems Engineering

2011-07-01

This work is concerned with the stability and control of ac power collection buses in offshore wind farms with high-voltage dc (HVDC) transmission connection to onshore power grid. The focus of the work is high-frequency interactions among the wind turbines, the ac collection bus and the filters, as well as the HVDC rectifier. Both voltage-source converter and line-commutated converter based HVDC systems are considered. To study high-frequency stability, particularly harmonic resonance in the ac bus, small-signal impedance models are developed for the wind inverters and the HVDC rectifier by using harmonic linearization techniques. An impedance-based stability criterion is applied to assess system stability in both positive- and negative-sequence domain. Small-signal stability conditions and requirements are developed from analytical impedance models. Detailed system-level simulation is used to validated the small-signal analysis. The goal of the study is to develop system design and control techniques that minimize the cost of the offshore infrastructure while guaranteeing system stability and power quality. (orig.)

Long-term stability of a one-dimensional current-driven double layer

International Nuclear Information System (INIS)

Hori, N.; Yamamoto, T.

1988-01-01

Long-term (>an electron transit time over the system) stability of a one-dimensional current-driven double layer is studied by numerical experiments using particles. In these experiments, the potential difference across the system is self-consistently determined by the space charge distributions inside the system. Each boundary of the system supplies a nondrifting half-Maxwellian plasma. The current density is increased by increasing the number density of the source plasma at the injection (right) boundary. A double layer can be developed by injection of a sufficiently high current density. For a fixed level of current injection, plasmas carrying no current with various densities (n/sup ts/ 0 ) are loaded on the left side of the system. Whether or not the generated double layer can maintain its potential drop for a long period depends on the density (n/sup ts/ 0 ) relative to the initial density (n/sup */ 0 ) near the injection boundary: (1) the double layer is found to grow when n/sup ts/ 0 = n/sup */ 0 ; (2) the steady double layer is seen for a long period when n/sup ts/ 0 approx. >n/sup */ 0 ; (3) the double layer is found to decay when n/sup ts/ 0 is even higher than n/sup */ 0 . A new concept of the current polarizability P/sub c/ = J/n/sup number/ is introduced for understanding these results, where J is the current density flowing through the double layer and n/sup number/ is the plasma density at the injection front, i.e., the low-potential edge of the double layer

Congestion management enhancing transient stability of power systems

International Nuclear Information System (INIS)

Esmaili, Masoud; Shayanfar, Heidar Ali; Amjady, Nima

2010-01-01

In a competitive electricity market, where market parties try to maximize their profits, it is necessary to keep an acceptable level of power system security to retain the continuity of electricity services to customers at a reasonable cost. Congestion in a power system is turned up due to network limits. After relieving congestion, the network may be operated with a reduced transient stability margin because of increasing the contribution of risky participants. In this paper, a novel congestion management method based on a new transient stability criterion is introduced. Using the sensitivity of corrected transient stability margin with respect to generations and demands, the proposed method so alleviates the congestion that the network can more retain its transient security compared with earlier methods. The proposed transient stability index is constructed considering the likelihood of credible faults. Indeed, market parties participate by their security-effective bids rather than raw bids. Results of testing the proposed method along with the earlier ones on the New-England test system elaborate the efficiency of the proposed method from the viewpoint of providing a better transient stability margin with a lower security cost. (author)

The algebraic criteria for the stability of control systems

Science.gov (United States)

Cremer, H.; Effertz, F. H.

1986-01-01

This paper critically examines the standard algebraic criteria for the stability of linear control systems and their proofs, reveals important previously unnoticed connections, and presents new representations. Algebraic stability criteria have also acquired significance for stability studies of non-linear differential equation systems by the Krylov-Bogoljubov-Magnus Method, and allow realization conditions to be determined for classes of broken rational functions as frequency characteristics of electrical network.

Film Grain-Size Related Long-Term Stability of Inverted Perovskite Solar Cells.

Science.gov (United States)

Chiang, Chien-Hung; Wu, Chun-Guey

2016-09-22

The power conversion efficiency (PCE) of the perovskite solar cell is high enough to be commercially viable. The next important issue is the stability of the device. This article discusses the effect of the perovskite grain-size on the long-term stability of inverted perovskite solar cells. Perovskite films composed of various sizes of grains were prepared by controlling the solvent annealing time. The grain-size related stability of the inverted cells was investigated both in ambient atmosphere at relative humidity of approximately 30-40 % and in a nitrogen filled glove box (H 2 Operovskite film having the grain size larger than 1 μm (D-10) decreases less than 10 % with storage in a glove box and less than 15 % when it was stored under an ambient atmosphere for 30 days. However, the cell using the perovskite film composed of small (∼100 nm) perovskite grains (D-0) exhibits complete loss of PCE after storage under the ambient atmosphere for only 15 days and a PCE loss of up to 70 % with storage in the glove box for 30 days. These results suggest that, even under H 2 O-free conditions, the chemical- and thermal-induced production of pin holes at the grain boundaries of the perovskite film could be the reason for long-term instability of inverted perovskite solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Short-term influences and long-term fundamentals: stabilizing and destabilizing effects in the energy industries

Energy Technology Data Exchange (ETDEWEB)

Robinson, Silvan [Royal Inst. of International Affairs, London (United Kingdom)

1992-10-01

The ideology of the market economy has become dominant in all walks of economic life and the energy industries are no exception. In the oil business, the stabilizing structures of the international majors and of long-term prices have been replaced by industrial fragmentation and market price mechanisms. Monopolies in other energy industries are being progressively dismantled. This live experiment is being conducted on an industry which historically has suffered from feast and famine economics and has tried to protect itself through various forms of cartelization. The short-term effects of this open market have so far tended to improve flexibility and consumer choice. The price instability has proved manageable. The danger is that cash flow compression will reduced investments in the future and an ability to make very long lead time shifts in the energy mix. For this some government intervention in markets is necessary. (author).

Wavelength stabilized multi-kW diode laser systems

Science.gov (United States)

Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens

2015-03-01

We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.

Sharp conditions for global stability of Lotka-Volterra systems with distributed delays

Science.gov (United States)

Faria, Teresa

We give a criterion for the global attractivity of a positive equilibrium of n-dimensional non-autonomous Lotka-Volterra systems with distributed delays. For a class of autonomous Lotka-Volterra systems, we show that such a criterion is sharp, in the sense that it provides necessary and sufficient conditions for the global asymptotic stability independently of the choice of the delay functions. The global attractivity of positive equilibria is established by imposing a diagonal dominance of the instantaneous negative feedback terms, and relies on auxiliary results showing the boundedness of all positive solutions. The paper improves and generalizes known results in the literature, namely by considering systems with distributed delays rather than discrete delays.

Interfacial, mechanical properties of Al{sub 2}O{sub 3}-NiAl composites respective to long term thermal stability

Energy Technology Data Exchange (ETDEWEB)

Song, Jia; Hu, Weiping; Gottstein, Guenter [RWTH Aachen Univ. (Germany). Inst. of Physical Metallurgy and Metal Physics

2010-07-01

The long term thermal stability of NiAl-Al{sub 2}O{sub 3} composites was investigated. During annealing of the composites at 973 K and 1373 K for 2000 hours, the NiAl-Al{sub 2}O{sub 3} system showed excellent chemical stability. However, grain growth and embrittlement progressed in the polycrystalline NiAl matrix. The interfacial shear strength decreased from 222{+-}50 MPa for the as-fabricated sample to 197{+-}48 MPa and 150{+-}38 MPa for the samples annealed at 973 K and 1373 K, respectively. The microstructure change during annealing at 973K and 1373 K affected the tensile strength differently. The potential causes of microstructure and interface structure change and their impact on mechanical properties are discussed. (orig.)

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

two parameters affecting power quality – harmonics and voltage stability. ... is necessary to pay attention to energy system stability in the planning, management, and ... where k ∈ {m, m + 1,... ,n} and n is total number of the buses in the system.

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.

Long-term memory stabilized by noise-induced rehearsal.

Science.gov (United States)

Wei, Yi; Koulakov, Alexei A

2014-11-19

Cortical networks can maintain memories for decades despite the short lifetime of synaptic strengths. Can a neural network store long-lasting memories in unstable synapses? Here, we study the effects of ongoing spike-timing-dependent plasticity (STDP) on the stability of memory patterns stored in synapses of an attractor neural network. We show that certain classes of STDP rules can stabilize all stored memory patterns despite a short lifetime of synapses. In our model, unstructured neural noise, after passing through the recurrent network connections, carries the imprint of all memory patterns in temporal correlations. STDP, combined with these correlations, leads to reinforcement of all stored patterns, even those that are never explicitly visited. Our findings may provide the functional reason for irregular spiking displayed by cortical neurons and justify models of system memory consolidation. Therefore, we propose that irregular neural activity is the feature that helps cortical networks maintain stable connections. Copyright © 2014 the authors 0270-6474/14/3415804-12$15.00/0.

Performance of the PBX-M passive plate stabilization system

International Nuclear Information System (INIS)

Kugel, H.W.; Bell, R.; Bernabei, S.

1994-02-01

The PBX-M passive plate stabilization system provides significant stabilization of long-wavelength external kink modes, the slowing of vertical instability growth rates, and the amelioration of disruption characteristics. The passive plate stabilization system has allowed the use of LHCD and IBW to induce current density and pressure profile modifications, and m = 1 divertor biasing for modifying edge plasma transport. Improvements in the passive plate system insulators and support structures have provided reliable operation. Impurity influxes with the close-fitting passive plates are low. Solid target boronization is applied routinely to reduce conditioning time and maintain clean conditions

Stability and stabilization of linear systems with saturating actuators

CERN Document Server

Tarbouriech, Sophie; Gomes da Silva Jr, João Manoel; Queinnec, Isabelle

2011-01-01

Gives the reader an in-depth understanding of the phenomena caused by the more-or-less ubiquitous problem of actuator saturation. Proposes methods and algorithms designed to avoid, manage or overcome the effects of actuator saturation. Uses a state-space approach to ensure local and global stability of the systems considered. Compilation of fifteen years' worth of research results.

Improved Power System Stability Using Backtracking Search Algorithm for Coordination Design of PSS and TCSC Damping Controller.

Science.gov (United States)

Niamul Islam, Naz; Hannan, M A; Mohamed, Azah; Shareef, Hussain

2016-01-01

Power system oscillation is a serious threat to the stability of multimachine power systems. The coordinated control of power system stabilizers (PSS) and thyristor-controlled series compensation (TCSC) damping controllers is a commonly used technique to provide the required damping over different modes of growing oscillations. However, their coordinated design is a complex multimodal optimization problem that is very hard to solve using traditional tuning techniques. In addition, several limitations of traditionally used techniques prevent the optimum design of coordinated controllers. In this paper, an alternate technique for robust damping over oscillation is presented using backtracking search algorithm (BSA). A 5-area 16-machine benchmark power system is considered to evaluate the design efficiency. The complete design process is conducted in a linear time-invariant (LTI) model of a power system. It includes the design formulation into a multi-objective function from the system eigenvalues. Later on, nonlinear time-domain simulations are used to compare the damping performances for different local and inter-area modes of power system oscillations. The performance of the BSA technique is compared against that of the popular particle swarm optimization (PSO) for coordinated design efficiency. Damping performances using different design techniques are compared in term of settling time and overshoot of oscillations. The results obtained verify that the BSA-based design improves the system stability significantly. The stability of the multimachine power system is improved by up to 74.47% and 79.93% for an inter-area mode and a local mode of oscillation, respectively. Thus, the proposed technique for coordinated design has great potential to improve power system stability and to maintain its secure operation.

Improved Power System Stability Using Backtracking Search Algorithm for Coordination Design of PSS and TCSC Damping Controller.

Directory of Open Access Journals (Sweden)

Naz Niamul Islam

Full Text Available Power system oscillation is a serious threat to the stability of multimachine power systems. The coordinated control of power system stabilizers (PSS and thyristor-controlled series compensation (TCSC damping controllers is a commonly used technique to provide the required damping over different modes of growing oscillations. However, their coordinated design is a complex multimodal optimization problem that is very hard to solve using traditional tuning techniques. In addition, several limitations of traditionally used techniques prevent the optimum design of coordinated controllers. In this paper, an alternate technique for robust damping over oscillation is presented using backtracking search algorithm (BSA. A 5-area 16-machine benchmark power system is considered to evaluate the design efficiency. The complete design process is conducted in a linear time-invariant (LTI model of a power system. It includes the design formulation into a multi-objective function from the system eigenvalues. Later on, nonlinear time-domain simulations are used to compare the damping performances for different local and inter-area modes of power system oscillations. The performance of the BSA technique is compared against that of the popular particle swarm optimization (PSO for coordinated design efficiency. Damping performances using different design techniques are compared in term of settling time and overshoot of oscillations. The results obtained verify that the BSA-based design improves the system stability significantly. The stability of the multimachine power system is improved by up to 74.47% and 79.93% for an inter-area mode and a local mode of oscillation, respectively. Thus, the proposed technique for coordinated design has great potential to improve power system stability and to maintain its secure operation.

Research on Design of MUH Attitude Stability Augmentation Control System

Science.gov (United States)

Fan, Shigang

2017-09-01

Attitude stability augmentation control system with a lower cost need to be designed so that MUH (Mini Unmanned Helicopter) can adapt to different types of geographic environment and fly steadily although the weather may be bad. Attitude feedback was calculated mainly by filtering estimation within attitude acquisition module in this system. Stability augmentation can be improved mainly by PI. This paper will depict running principle and designing process of MUH attitude stability augmentation control system and algorithm that is considered as an important part in this system.

Stabilization of Networked Control Systems with Variable Delays and Saturating Inputs

Directory of Open Access Journals (Sweden)

M. Mahmodi Kaleybar

2014-06-01

Full Text Available In this paper, improved conditions for the synthesis of static state-feedback controller are derived to stabilize networked control systems (NCSs subject to actuator saturation. Both of the data packet latency and dropout which deteriorate the performance of the closed-loop system are considered in the NCS model via variable delays. Two different techniques are employed to incorporate actuator saturation in the system description. Utilizing Lyapunov-Krasovskii Theorem, delay-dependent conditions are obtained in terms of linear matrix inequalities (LMIs to determine the static feedback gain. Moreover, an optimization problem is formulated in order to find the less conservative estimate for the region of attraction corresponding to different maximum allowable delays. Numerical examples are introduced to demonstrate the effectiveness and advantages of the proposed schemes.

NSRL 200 MeV linac beam energy stabilization system

International Nuclear Information System (INIS)

Huang Guirong; Pei Yuanji; Dong Sai

2001-01-01

By using the computer image processing technology and RF phase auto-shifting system, the ESS (Energy Stabilization System) was applied to 200 MeV Linac. the ESS adjusts beam energy automatically in a range of +-4 MeV. After adjustment beam energy stability is improved to +-6%

On Robust Stability of Systems of Differential-Algebraic Equations

Directory of Open Access Journals (Sweden)

A. Shcheglova

2016-06-01

The sufficient conditions of robust stability for index-one and index-two systems are obtained. We use the values of real and complex stability radii obtained for system of ordinary differential equations solved with respect to the derivatives. We consider the example illustrating the obtained results.

Electrostatic stabilizer for a passive magnetic bearing system

Science.gov (United States)

Post, Richard F.

2015-11-24

Electrostatic stabilizers are provided for passive bearing systems composed of annular magnets having a net positive stiffness against radial displacements and that have a negative stiffness for vertical displacements, resulting in a vertical instability. Further embodiments are shown of a radial electrostatic stabilizer geometry (using circuitry similar to that employed in the vertical stabilizer). This version is suitable for stabilizing radial (lateral) displacements of a rotor that is levitated by annular permanent magnets that are stable against vertical displacements but are unstable against radial displacements.

Simplified Stability Criteria for Delayed Neutral Systems

Directory of Open Access Journals (Sweden)

Xinghua Zhang

2014-01-01

Full Text Available For a class of linear time-invariant neutral systems with neutral and discrete constant delays, several existing asymptotic stability criteria in the form of linear matrix inequalities (LMIs are simplified by using matrix analysis techniques. Compared with the original stability criteria, the simplified ones include fewer LMI variables, which can obviously reduce computational complexity. Simultaneously, it is theoretically shown that the simplified stability criteria and original ones are equivalent; that is, they have the same conservativeness. Finally, a numerical example is employed to verify the theoretic results investigated in this paper.

Synchrophasor-Assisted Prediction of Stability/Instability of a Power System

Science.gov (United States)

Saha Roy, Biman Kumar; Sinha, Avinash Kumar; Pradhan, Ashok Kumar

2013-05-01

This paper presents a technique for real-time prediction of stability/instability of a power system based on synchrophasor measurements obtained from phasor measurement units (PMUs) at generator buses. For stability assessment the technique makes use of system severity indices developed using bus voltage magnitude obtained from PMUs and generator electrical power. Generator power is computed using system information and PMU information like voltage and current phasors obtained from PMU. System stability/instability is predicted when the indices exceeds a threshold value. A case study is carried out on New England 10-generator, 39-bus system to validate the performance of the technique.

On the long-term stability of calibration standards in different matrices.

Science.gov (United States)

Kandić, A; Vukanac, I; Djurašević, M; Novković, D; Šešlak, B; Milošević, Z

2012-09-01

In order to assure Quality Control in accordance with ISO/IEC 17025, it was important, from metrological point of view, to examine the long-term stability of calibration standards previously prepared. Comprehensive reconsideration on efficiency curves with respect to the ageing of calibration standards is presented in this paper. The calibration standards were re-used after a period of 5 years and analysis of the results showed discrepancies in efficiency values. Copyright © 2012 Elsevier Ltd. All rights reserved.

Long term stability analysis of cast iron shaft linings after Coal Mine closure and flooding

Energy Technology Data Exchange (ETDEWEB)

Hadj-Hassen, F. [Ecole des Mines de Paris - CGES, 77 - Fontainebleau (France); Bienvenu, Y. [Ecole des Mines de Paris, CM, 91 - Evry (France); Noirel, J.F. [Charbonnages de France, DTN, 57 - Freyming Merlebach (France); Metz, M. [charbonnages de France, ESA, 57 - Freyming Merlebach (France)

2005-07-01

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)

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)

A mathematical model of the hypothalamo-pituitary-adrenocortical system and its stability analysis

Energy Technology Data Exchange (ETDEWEB)

Savic, Danka [Vinca Institute of Nuclear Sciences, Laboratory for Theoretical and Condensed Matter Physics, P.O. Box 522, Belgrade 11001 (Serbia and Montenegro)] e-mail: dankasav@eunet.yu; Jelic, Smiljana [Vinca Institute of Nuclear Sciences, Laboratory for Theoretical and Condensed Matter Physics, P.O. Box 522, Belgrade 11001 (Serbia and Montenegro)

2005-10-01

It is commonly assumed that the hypothalamo-pituitary-adrenocortical (HPA) axis generates oscillations, because a regular daily rhythm of its component hormones is observed. We offer another plausible explanation of the origin of its circadian oscillations: HPA just responds to an independent external pacemaker (from the suprachiazmatic nucleus, SCN). Five versions (with and without time delay) of a qualitative non-phenomenological mathematical model of the HPA axis as a feedback mechanism are constructed wherein all the terms in the equations are introduced according to the rules of chemical kinetics, i.e. are physicochemically interpretable. The dynamics of the HPA axis model was examined using linear stability analysis. The results show stability of this system, meaning that it does not generate diurnal oscillations. Computer simulation based on this model shows oscillations that are system's response to an external pulsing activator (SCN) implying that the observed time-periodic pattern does not have to be an intrinsic property of the HPA axis.

A mathematical model of the hypothalamo-pituitary-adrenocortical system and its stability analysis

International Nuclear Information System (INIS)

Savic, Danka; Jelic, Smiljana

2005-01-01

It is commonly assumed that the hypothalamo-pituitary-adrenocortical (HPA) axis generates oscillations, because a regular daily rhythm of its component hormones is observed. We offer another plausible explanation of the origin of its circadian oscillations: HPA just responds to an independent external pacemaker (from the suprachiazmatic nucleus, SCN). Five versions (with and without time delay) of a qualitative non-phenomenological mathematical model of the HPA axis as a feedback mechanism are constructed wherein all the terms in the equations are introduced according to the rules of chemical kinetics, i.e. are physicochemically interpretable. The dynamics of the HPA axis model was examined using linear stability analysis. The results show stability of this system, meaning that it does not generate diurnal oscillations. Computer simulation based on this model shows oscillations that are system's response to an external pulsing activator (SCN) implying that the observed time-periodic pattern does not have to be an intrinsic property of the HPA axis

Real time computer control of a nonlinear Multivariable System via Linearization and Stability Analysis

International Nuclear Information System (INIS)

Raza, K.S.M.

2004-01-01

This paper demonstrates that if a complicated nonlinear, non-square, state-coupled multi variable system is smartly linearized and subjected to a thorough stability analysis then we can achieve our design objectives via a controller which will be quite simple (in term of resource usage and execution time) and very efficient (in terms of robustness). Further the aim is to implement this controller via computer in a real time environment. Therefore first a nonlinear mathematical model of the system is achieved. An intelligent work is done to decouple the multivariable system. Linearization and stability analysis techniques are employed for the development of a linearized and mathematically sound control law. Nonlinearities like the saturation in actuators are also been catered. The controller is then discretized using Runge-Kutta integration. Finally the discretized control law is programmed in a computer in a real time environment. The programme is done in RT -Linux using GNU C for the real time realization of the control scheme. The real time processes, like sampling and controlled actuation, and the non real time processes, like graphical user interface and display, are programmed as different tasks. The issue of inter process communication, between real time and non real time task is addressed quite carefully. The results of this research pursuit are presented graphically. (author)

Power system stabilization by SMES using current-fed pwm power conditioner

International Nuclear Information System (INIS)

Ishikawa, T.; Akita, S.; Taniguchi, H.; Kosho, S.; Tanaka, T.

1988-01-01

A superconducting magnetic energy storage (SMES) unit, consisted of superconducting coil and AC/DC power conditioner, can be used to suppress various kinds of instability that may cause service interruption in electric power system as it has high controllability of input/output electric power. Power system stabilizing ability of SMES has been examined experimentally by using model power system and small SMES unit. Current-fed PWM power conditioner was used to obtain maximum stabilizing effect by controlling active and reactive power simultaneously and independently. Power conditioner configuration, operating characteristics and control scheme for power system stabilization are also described. Results from experiments show the effectiveness of SMES on power system stabilization

Improvement of the transient stability using SFCL in Korean power systems

International Nuclear Information System (INIS)

Hwang, Intae; Lee, Seung Ryul; Seo, Sangsoo; Yoon, Jaeyoung; Kim, Chul-Hwan

2013-01-01

Highlights: •In Korea, the Special Protection System is applied for protecting the power system. •Hybrid SFCL is protecting the power system from viewpoint of the transient stability. •Basic hybrid SFCL system cannot recover during the auto-reclosing operation. •This paper performs analysis of transient stability using the novel hybrid SFCL. -- Abstract: This paper proposed a novel hybrid SFCL system for the enhancement of the transient stability in Korean power transmission system with auto-reclosing operation. The proposed SFCL system has an operation mechanism that the current limiting impedance is eliminated from the power system in a fault clearing time for the enhancement of the transient stability. Also, the system can cover the auto-reclosing operation of the transmission power system. This study analyzed an improvement of the special protection system by applying the proposed SFCL system to real power system in Korea

Stabilization of third-order bilinear systems using constant controls

Directory of Open Access Journals (Sweden)

A. E. Golubev

2014-01-01

Full Text Available This paper deals with the zero equilibrium stabilization for dynamical systems that have control input singularities. A dynamical system with scalar control input is called nonregular if the coefficient of input becomes null on a subset of the phase space that contains the origin. One of the classes of nonregular dynamical systems is represented by bilinear systems. In case of second-order bilinear systems the necessary and sufficient conditions for the zero equilibrium stabilizability are known in the literature. However, in general case the stabilization problem in the presence of control input singularities has not been solved yet.In this note we solve the problem of the zero equilibrium stabilization for the third-order bilinear dynamical systems given in a canonical form. The solution is found in the class of constant controls. The necessary and sufficient conditions are obtained for the zero equilibrium stabilizability of the bilinear systems in question.The dependence of the zero equilibrium stabilizability on system parameter values is analyzed. The general criteria of stabilizability by means of constant controls are given for the bilinear systems in question. In case when all the system parameters have nonzero values the necessary and sufficient stabilizability conditions are proved. The case when some of the parameters are equal to zero is also considered.Further research can be focused on extending the obtained results to a higher-order case of bilinear and affine dynamical systems. The solution of the considered stabilization problem should also be found not only within constant controls but also in a class of state feedbacks, particularly, in the case when stabilizing constant control does not exist.One of the potential application areas for the obtained theoretical results is automatic control of technical plants like unmanned aerial vehicles and mobile robots.

Robust stability bounds for multi-delay networked control systems

Science.gov (United States)

Seitz, Timothy; Yedavalli, Rama K.; Behbahani, Alireza

2018-04-01

In this paper, the robust stability of a perturbed linear continuous-time system is examined when controlled using a sampled-data networked control system (NCS) framework. Three new robust stability bounds on the time-invariant perturbations to the original continuous-time plant matrix are presented guaranteeing stability for the corresponding discrete closed-loop augmented delay-free system (ADFS) with multiple time-varying sensor and actuator delays. The bounds are differentiated from previous work by accounting for the sampled-data nature of the NCS and for separate communication delays for each sensor and actuator, not a single delay. Therefore, this paper expands the knowledge base in multiple inputs multiple outputs (MIMO) sampled-data time delay systems. Bounds are presented for unstructured, semi-structured, and structured perturbations.

Characterizing short-term stability for Boolean networks over any distribution of transfer functions

International Nuclear Information System (INIS)

Seshadhri, C.; Smith, Andrew M.; Vorobeychik, Yevgeniy; Mayo, Jackson R.; Armstrong, Robert C.

2016-01-01

Here we present a characterization of short-term stability of random Boolean networks under arbitrary distributions of transfer functions. Given any distribution of transfer functions for a random Boolean network, we present a formula that decides whether short-term chaos (damage spreading) will happen. We provide a formal proof for this formula, and empirically show that its predictions are accurate. Previous work only works for special cases of balanced families. Finally, it has been observed that these characterizations fail for unbalanced families, yet such families are widespread in real biological networks.

Power system stability enhancement using facts controllers: a review

International Nuclear Information System (INIS)

Abido, M. A

2009-01-01

In recent years, power demand has increased substantially while the expansion of power generation and transmission has been severely limited due to limited resources and environmental restrictions. As a consequence, some transmission lines are heavily loaded and the system stability becomes a power transfer-limiting factor. Flexible AC transmission systems (FACTS) controllers have been mainly used for solving various power system steady state control problems. However, recent studies reveal that FACTS controllers could be employed to enhance power system stability in addition to their main function of power flow control. The literature shows an increasing interest in this subject for the last two decades, where the enhancement of system stability using FACTS controllers has been extensively investigated. This paper presents a comprehensive review on the research and developments in the power system stability enhancement using FACTS damping controllers. Several technical issues related to FACTS installations have been highlighted and performance comparison of different FACTS controllers has been discussed. In addition, some of the utility experience, real-world installations, and semiconductor technology development have been reviewed and summarized. Applications of FACTS to other power system studies have also been discussed. About two hundred twenty seven research publications have been classified and appended for a quick reference. (author)

Improved Delay-Dependent Robust Stability Criteria for a Class of Uncertain Neutral Type Lur’e Systems with Discrete and Distributed Delays

Directory of Open Access Journals (Sweden)

Kaibo Shi

2014-01-01

Full Text Available This paper is concerned with the problem of delay-dependent robust stability analysis for a class of uncertain neutral type Lur’e systems with mixed time-varying delays. The system has not only time-varying uncertainties and sector-bounded nonlinearity, but also discrete and distributed delays, which has never been discussed in the previous literature. Firstly, by employing one effective mathematical technique, some less conservative delay-dependent stability results are established without employing the bounding technique and the mode transformation approach. Secondly, by constructing an appropriate new type of Lyapunov-Krasovskii functional with triple terms, improved delay-dependent stability criteria in terms of linear matrix inequalities (LMIs derived in this paper are much brief and valid. Furthermore, both nonlinearities located in finite sector and infinite one have been also fully taken into account. Finally, three numerical examples are presented to illustrate lesser conservatism and the advantage of the proposed main results.

Clinical characteristics and long-term response to mood stabilizers in patients with bipolar disorder and different age at onset

Science.gov (United States)

Dell’Osso, Bernardo; Buoli, Massimiliano; Riundi, Riccardo; D’Urso, Nazario; Pozzoli, Sara; Bassetti, Roberta; Mundo, Emanuela; Altamura, A Carlo

2009-01-01

Introduction Bipolar disorder (BD) is a prevalent, comorbid, and impairing condition. Potential predictors of response to pharmacological treatment are object of continuous investigation in patients with BD. The present naturalistic study was aimed to assess clinical features and long-term response to mood stabilizers in a sample of bipolar subjects with different ages at onset. Methods The study sample included 108 euthymic patients, diagnosed as affected by BD, either type I or II, according to the DSM-IV-TR, who were started on mood stabilizer treatment. Patients were followed-up for 24 months and the occurrence of any mood episode collected. At the end of the follow-up, patients were divided in 3 subgroups according to the age at onset (early-onset ≤30 years, middle-onset >30–≤45 years, and late-onset >45 years, respectively) and the long-term response to mood stabilizers was compared between them along with other clinical features. Results The three subgroups showed significant differences in terms of clinical and demographic features and, with respect to long-term response to mood stabilizers, the early-onset subgroup showed a better outcome in terms of reduction of major depressive episodes during the 24-month follow-up compared to the other subgroups (one way ANOVA, F = 3.57, p = 0.032). Conclusions Even though further controlled studies are needed to clarify the relationship between age at onset and outcome in BD, the present follow-up study suggests clinical peculiarities and different patterns of response to mood stabilizers across distinct subgroups of patients with BD and different ages at onset. PMID:19649214

On a program manifold’s stability of one contour automatic control systems

Directory of Open Access Journals (Sweden)

Zumatov S. S.

2017-12-01

Full Text Available Methodology of analysis of stability is expounded to the one contour systems automatic control feedback in the presence of non-linearities. The methodology is based on the use of the simplest mathematical models of the nonlinear controllable systems. Stability of program manifolds of one contour automatic control systems is investigated. The sufficient conditions of program manifold’s absolute stability of one contour automatic control systems are obtained. The Hurwitz’s angle of absolute stability was determined. The sufficient conditions of program manifold’s absolute stability of control systems by the course of plane in the mode of autopilot are obtained by means Lyapunov’s second method.

The Derivation of the Stability Bound of the Feedback ANC System That Has an Error in the Estimated Secondary Path Model

Directory of Open Access Journals (Sweden)

Seong-Pil Moon

2018-01-01

Full Text Available This paper investigates the stability problem of the feedback active noise control (ANC system, which can be caused by the modeling error of the electro-acoustic path estimation in its feedback mechanism. A stability analysis method is proposed to obtain the stability bound as a form of a closed-form equation in terms of the delay error length of the secondary path, the ANC filter length, and the primary noise frequency. In the proposed method, the system’s open loop magnitude and phase response equations are separately exploited and approximated within the Nyquist stability criterion. The stability bound of the proposed method is verified by comparing both the original Nyquist stability condition and the simulation results.

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.

A Methodology to Efficiently Compare Operating System Stability

NARCIS (Netherlands)

van der Kouwe, E.; Giuffrida, C.; Ghitulete, R.; Tanenbaum, A.S.

2015-01-01

Despite decades of advances in software engineering, operating systems (OSes) are still plagued by crashes due to software faults, calling for techniques to improve OS stability when faults occur. Evaluating such techniques requires a way to compare the stability of different OSes that is both

New Delay-Dependent Stability Criteria for Uncertain Neutral Systems with Mixed Time-Varying Delays and Nonlinear Perturbations

Directory of Open Access Journals (Sweden)

Hamid Reza Karimi

2009-01-01

Full Text Available The problem of stability analysis for a class of neutral systems with mixed time-varying neutral, discrete and distributed delays and nonlinear parameter perturbations is addressed. By introducing a novel Lyapunov-Krasovskii functional and combining the descriptor model transformation, the Leibniz-Newton formula, some free-weighting matrices, and a suitable change of variables, new sufficient conditions are established for the stability of the considered system, which are neutral-delay-dependent, discrete-delay-range-dependent, and distributed-delay-dependent. The conditions are presented in terms of linear matrix inequalities (LMIs and can be efficiently solved using convex programming techniques. Two numerical examples are given to illustrate the efficiency of the proposed method.

Adaptive fuzzy observer-based stabilization of a class of uncertain time-delayed chaotic systems with actuator nonlinearities

International Nuclear Information System (INIS)

Shahnazi, Reza; Haghani, Adel; Jeinsch, Torsten

2015-01-01

An observer-based output feedback adaptive fuzzy controller is proposed to stabilize a class of uncertain chaotic systems with unknown time-varying time delays, unknown actuator nonlinearities and unknown external disturbances. The actuator nonlinearity can be backlash-like hysteresis or dead-zone. Based on universal approximation property of fuzzy systems the unknown nonlinear functions are approximated by fuzzy systems, where the consequent parts of fuzzy rules are tuned with adaptive schemes. The proposed method does not need the availability of the states and an observer based output feedback approach is proposed to estimate the states. To have more robustness and at the same time to alleviate chattering an adaptive discontinuous structure is suggested. Semi-global asymptotic stability of the overall system is ensured by proposing a suitable Lyapunov–Krasovskii functional candidate. The approach is applied to stabilize the time-delayed Lorenz chaotic system with uncertain dynamics amid significant disturbances. Analysis of simulations reveals the effectiveness of the proposed method in terms of coping well with the modeling uncertainties, nonlinearities in actuators, unknown time-varying time-delays and unknown external disturbances while maintaining asymptotic convergence

Stability Analysis of Interconnected Fuzzy Systems Using the Fuzzy Lyapunov Method

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Ken Yeh

2010-01-01

Full Text Available The fuzzy Lyapunov method is investigated for use with a class of interconnected fuzzy systems. The interconnected fuzzy systems consist of J interconnected fuzzy subsystems, and the stability analysis is based on Lyapunov functions. Based on traditional Lyapunov stability theory, we further propose a fuzzy Lyapunov method for the stability analysis of interconnected fuzzy systems. The fuzzy Lyapunov function is defined in fuzzy blending quadratic Lyapunov functions. Some stability conditions are derived through the use of fuzzy Lyapunov functions to ensure that the interconnected fuzzy systems are asymptotically stable. Common solutions can be obtained by solving a set of linear matrix inequalities (LMIs that are numerically feasible. Finally, simulations are performed in order to verify the effectiveness of the proposed stability conditions in this paper.

Decentralized linear quadratic power system stabilizers for multi ...

Indian Academy of Sciences (India)

Linear quadratic stabilizers are well-known for their superior control capabilities when compared to the conventional lead–lag power system stabilizers. However, they have not seen much of practical importance as the state variables are generally not measurable; especially the generator rotor angle measurement is not ...

INERTIAL TECHNOLOGIES IN SYSTEMS FOR STABILIZATION OF GROUND VEHICLES EQUIPMENT

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Olha Sushchenko

2016-12-01

Full Text Available Purpose: The vibratory inertial technology is a recent modern inertial technology. It represents the most perspective approach to design of inertial sensors, which can be used in stabilization and tracking systems operated on vehicles of the wide class. The purpose of the research is to consider advantages of this technology in comparison with laser and fiber-optic ones. Operation of the inertial sensors on the ground vehicles requires some improvement of the Coriolis vibratory gyroscope with the goal to simplify information processing, increase reliability, and compensate bias. Methods: Improvement of the Coriolis vibratory gyroscope includes introducing of the phase detector and additional excitation unit. The possibility to use the improved Coriolis vibratory gyroscope in the stabilization systems operated on the ground vehicles is shown by means of analysis of gyroscope output signal. To prove efficiency of the Coriolis vibratory gyroscope in stabilization system the simulation technique is used. Results: The scheme of the improved Coriolis vibratory gyroscope including the phase detector and additional excitation unit is developed and analyzed. The way to compensate bias is determined. Simulation of the stabilization system with the improved Coriolis vibratory gyroscope is carried out. Expressions for the output signals of the improved Coriolis vibratory gyroscope are derived. The error of the output signal is estimated and the possibility to use the modified Coriolis vibratory gyroscope in stabilization systems is proved. The results of stabilization system simulation are given. Their analysis is carried out. Conclusions: The represented results prove efficiency of the proposed technical decisions. They can be useful for design of stabilization platform with instrumental equipment operated on moving vehicles of the wide class.

Robust Stability and Stabilization of Interval Uncertain Descriptor Fractional-Order Systems with the Fractional-Order α: The 1≤α<2 Case

Directory of Open Access Journals (Sweden)

Yuanhua Li

2015-01-01

Full Text Available Stability and stabilization of fractional-order interval system is investigated. By adding parameters to linear matrix inequalities, necessary and sufficient conditions for stability and stabilization of the system are obtained. The results on stability check for uncertain FO-LTI systems with interval coefficients of dimension n only need to solve one 4n-by-4n LMI. Numerical examples are presented to shown the effectiveness of our results.

On the stability of some systems of exponential difference equations

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N. Psarros

2018-01-01

Full Text Available In this paper we prove the stability of the zero equilibria of two systems of difference equations of exponential type, which are some extensions of an one-dimensional biological model. The stability of these systems is investigated in the special case when one of the eigenvalues is equal to -1 and the other eigenvalue has absolute value less than 1, using centre manifold theory. In addition, we study the existence and uniqueness of positive equilibria, the attractivity and the global asymptotic stability of these equilibria of some related systems of difference equations.

Long-term stability of TES satellite radiance measurements

Directory of Open Access Journals (Sweden)

T. C. Connor

2011-07-01

Full Text Available The utilization of Tropospheric Emission Spectrometer (TES Level 2 (L2 retrieval products for the purpose of assessing long term changes in atmospheric trace gas composition requires knowledge of the overall radiometric stability of the Level 1B (L1B radiances. The purpose of this study is to evaluate the stability of the radiometric calibration of the TES instrument by analyzing the difference between measured and calculated brightness temperatures in selected window regions of the spectrum. The Global Modeling and Assimilation Office (GMAO profiles for temperature and water vapor and the Real-Time Global Sea Surface Temperature (RTGSST are used as input to the Optimal Spectral Sampling (OSS radiative transfer model to calculate the simulated spectra. The TES reference measurements selected cover a 4-year period of time from mid 2005 through mid 2009 with the selection criteria being; observation latitudes greater than −30° and less than 30°, over ocean, Global Survey mode (nadir view and retrieved cloud optical depth of less than or equal to 0.01. The TES cloud optical depth retrievals are used only for screening purposes and no effects of clouds on the radiances are included in the forward model. This initial screening results in over 55 000 potential reference spectra spanning the four year period. Presented is a trend analysis of the time series of the residuals (observation minus calculations in the TES 2B1, 1B2, 2A1, and 1A1 bands, with the standard deviation of the residuals being approximately equal to 0.6 K for bands 2B1, 1B2, 2A1, and 0.9 K for band 1A1. The analysis demonstrates that the trend in the residuals is not significantly different from zero over the 4-year period. This is one method used to demonstrate that the relative radiometric calibration is stable over time, which is very important for any longer term analysis of TES retrieved products (L2, particularly well-mixed species such as carbon dioxide and methane.

Optimal boundary control and boundary stabilization of hyperbolic systems

CERN Document Server

Gugat, Martin

2015-01-01

This brief considers recent results on optimal control and stabilization of systems governed by hyperbolic partial differential equations, specifically those in which the control action takes place at the boundary.  The wave equation is used as a typical example of a linear system, through which the author explores initial boundary value problems, concepts of exact controllability, optimal exact control, and boundary stabilization.  Nonlinear systems are also covered, with the Korteweg-de Vries and Burgers Equations serving as standard examples.  To keep the presentation as accessible as possible, the author uses the case of a system with a state that is defined on a finite space interval, so that there are only two boundary points where the system can be controlled.  Graduate and post-graduate students as well as researchers in the field will find this to be an accessible introduction to problems of optimal control and stabilization.

Long-Term Charge/Discharge Cycling Stability of MnO2 Aqueous Supercapacitor under Positive Polarization

KAUST Repository

Ataherian, Fatemeh; Wu, Nae-Lih

2011-01-01

The long-term charge/discharge cycling stability of MnO 2 electrode under positive polarization in aqueous KCl electrolyte has been studied over different potential windows spanning from the open circuit potential to varied higher-end potential

The effect of the virtual mass force term on the stability of transient two-phase flow analysis

International Nuclear Information System (INIS)

Watanabe, Tadashi; Hirano, Masashi; Tanabe, Fumiya

1989-08-01

The effect of the virtual mass force term on the stability of transient two-phase flow analysis is studied. The objective form of the virtual mass acceleration is used. The virtual mass coefficient is determined from the stability condition of basic equations against infinitesimal high wave-number perturbations. The parameter is chosen so that a reasonable agreement between the analytical and experimental sound speed in two-phase flows can be obtained. A one-dimensional sedimentation problem is simulated by the MINCS code which is a tool for transient two-phase flow analysis. The stability analysis is performed for the numerical procedure. It is shown that calculated results are stabilized so long as the virtual mass coefficient satisfies the stability condition of differential equations. (author)

Stability of large scale interconnected dynamical systems

International Nuclear Information System (INIS)

Akpan, E.P.

1993-07-01

Large scale systems modelled by a system of ordinary differential equations are considered and necessary and sufficient conditions are obtained for the uniform asymptotic connective stability of the systems using the method of cone-valued Lyapunov functions. It is shown that this model significantly improves the existing models. (author). 9 refs

14 CFR 29.672 - Stability augmentation, automatic, and power-operated systems.

Science.gov (United States)

2010-01-01

... power-operated systems. 29.672 Section 29.672 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Construction Control Systems § 29.672 Stability augmentation, automatic, and power-operated systems. If the functioning of stability augmentation or other automatic or power-operated system is necessary to show...

14 CFR 27.672 - Stability augmentation, automatic, and power-operated systems.

Science.gov (United States)

2010-01-01

... power-operated systems. 27.672 Section 27.672 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Construction Control Systems § 27.672 Stability augmentation, automatic, and power-operated systems. If the functioning of stability augmentation or other automatic or power-operated systems is necessary to show...

Theoretical bases on thermal stability of layered metallic systems

International Nuclear Information System (INIS)

Kadyrzhanov, K.K.; Rusakov, V.S.; Turkebaev, T.Eh.; Zhankadamova, A.M.; Ensebaeva, M.Z.

2003-01-01

The paper is dedicated to implementation of the theoretical bases for layered metallic systems thermal stabilization. The theory is based on the stabilization mechanism expense of the intermediate two-phase field formation. As parameters of calculated model are coefficients of mutual diffusion and inclusions sizes of generated phases in two-phase fields. The stabilization time dependence for beryllium-iron (Be (1.1 μm)-Fe(5.5 μm)) layered system from iron and beryllium diffusion coefficients, and inclusions sizes is shown as an example. Conclusion about possible mechanisms change at transition from microscopic consideration to the nano-crystal physics level is given

Stability of a slotted ALOHA system with capture effect

Science.gov (United States)

Onozato, Yoshikuni; Liu, Jin; Noguchi, Shoichi

1989-02-01

The stability of a slotted ALOHA system with capture effect is investigated under a general communication environment where terminals are divided into two groups (low-power and high-power) and the capture effect is modeled by capture probabilities. An approximate analysis is developed using catastrophe theory, in which the effects of system and user parameters on the stability are characterized by the cusp catastrophe. Particular attention is given to the low-power group, since it must bear the strain under the capture effect. The stability conditions of the two groups are given explicitly by bifurcation sets.

Modeling and power system stability of VSC-HVDC systems for grid-connection of large offshore windfarms

Energy Technology Data Exchange (ETDEWEB)

Xue Yijing [Vestas China, Beijing (China); Akhmatov, Vladislav [Technical Univ. of Denmark, Lyngby (Denmark). Centre for Electric Technology

2009-07-01

Utilization of Voltage Source Converter (VSC) - High Voltage Direct Current (HVDC) systems for grid-connection of large offshore windfarms becomes relevant as installed power capacities as well as distances to the connection points of on-land transmission systems increase. At the same time, the grid code requirements of the Transmission System Operators (TSO), including ancillary system services and Low-Voltage Fault-Ride-Through (LVFRT) capability of large offshore windfarms, become more demanding. This paper presents a general-level model of and a LVFRT solution for a VSC-HVDC system for grid-connection of large offshore windfarms. The VSC-HVDC model is implemented using a general approach of independent control of active and reactive power in normal operations. The on-land VSC inverter, i.e. a grid-side inverter, provides voltage support to the transmission system and comprises a LVFRT solution in short-circuit faults. The presented model, LVFRT solution and impact on the system stability are investigated as a case study of a 1,000 MW offshore windfarm grid-connected through a VSC-HVDC system. The investigation is carried out on a model of the west Danish, with some elements of the north German, 400 kV, 220 kV and 150 kV transmission systems stage 2005-2006 using the DIgSILENT PowerFactory simulation program. In the investigation, a thermal power plant just south to the Danish border has been substituted by this 1,000 MW offshore windfarm utilizing the VSC-HVDC system. The investigation has shown that the substitution of a thermal power plant by a VSC-HVDC connected offshore windfarm should not have any negative impact on the short-term stability of the west Danish transmission system. The investigation should be repeated applying updated system model stages and offshore wind power commissioning schedules in the North and Baltic Seas. (orig.)

Delay-dependent stability of neural networks of neutral type with time delay in the leakage term

International Nuclear Information System (INIS)

Li, Xiaodi; Cao, Jinde

2010-01-01

This paper studies the global asymptotic stability of neural networks of neutral type with mixed delays. The mixed delays include constant delay in the leakage term (i.e. 'leakage delay'), time-varying delays and continuously distributed delays. Based on the topological degree theory, Lyapunov method and linear matrix inequality (LMI) approach, some sufficient conditions are derived ensuring the existence, uniqueness and global asymptotic stability of the equilibrium point, which are dependent on both the discrete and distributed time delays. These conditions are expressed in terms of LMI and can be easily checked by the MATLAB LMI toolbox. Even if there is no leakage delay, the obtained results are less restrictive than some recent works. It can be applied to neural networks of neutral type with activation functions without assuming their boundedness, monotonicity or differentiability. Moreover, the differentiability of the time-varying delay in the non-neutral term is removed. Finally, two numerical examples are given to show the effectiveness of the proposed method

STABILITY SYSTEMS VIA HURWITZ POLYNOMIALS

Directory of Open Access Journals (Sweden)

BALTAZAR AGUIRRE HERNÁNDEZ

2017-01-01

Full Text Available To analyze the stability of a linear system of differential equations  ẋ = Ax we can study the location of the roots of the characteristic polynomial pA(t associated with the matrix A. We present various criteria - algebraic and geometric - that help us to determine where the roots are located without calculating them directly.

Using DCM pitch modulation and feedback to improve long term X-ray beam stability

International Nuclear Information System (INIS)

Bloomer, C; Dent, A; Diaz-Moreno, S; Dolbnya, I; Pedersen, U; Rehm, G; Tang, C; Thomas, C

2013-01-01

In this paper we demonstrate significant improvements to the stability of the monochromatic X-ray beam intensity on several beamlines at Diamond, using a modulation of the pitch axis of the DCM with a piezoelectric actuator. The modulation is detected on an intensity diagnostic (e.g. an ion chamber) using a software lock-in technique. The detected amplitude and phase are used in a feedback to keep the DCM at the peak of the rocking curve, or any arbitrary position 'off-peak' which might be desired to detune the DCM and reject unwanted harmonics. A major advantage of this software based system is the great flexibility offered, using standard, readily available instrumentation. Measurements of the short and long-term performance of the feedback on several beamlines are presented, and the limitations of such a feedback are discussed.

Transient stability risk assessment of power systems incorporating wind farms

DEFF Research Database (Denmark)

Miao, Lu; Fang, Jiakun; Wen, Jinyu

2013-01-01

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......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....... 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....

Stability analysis of transmission system with high penetration of distributed generation

Energy Technology Data Exchange (ETDEWEB)

Reza, M.

2006-12-21

Nowadays, interest in generating electricity using decentralized generators of relatively small scale ('distributed generation', DG) is increasing. This work deals with the impact of implementing DG on the transmission system transient stability, with the emphasis on a potential transition from a 'vertical power system' to a 'horizontal power system. A problem in power systems is maintaining synchronous operation of all (centralized) synchronous machines. This stability problem associated is called rotor angle stability. In this work, the impact of the DG implementation on this is investigated. The impact of DG levels on the system transient stability when the increasing DG level is followed by a reduction of centralized generators in service resulting in a 'vertical to horizontal' transformation of the power system is also investigated. Furthermore, a stochastic analysis is used to study the transient stability of the power systems. The results show that including the stochastic behavior of DG leads to a more complete and detailed view of the system performance. Finally, the situation when the power system is pushed towards a scenario, where DG penetration reaches a level that covers the total load of the original power system (100% DG level) is investigated. The research performed in this work indicates that from the transmission system stability point of view, if higher DG penetration levels are coming up, sufficient inertia and voltage support must be installed. Furthermore, one should be aware of the fact that the system behaves stochastically, especially with DG. To a certain extent regional balancing of power can be performed by local voltage control.

Global stability and tumor clearance conditions for a cancer chemotherapy system

Science.gov (United States)

Valle, Paul A.; Starkov, Konstantin E.; Coria, Luis N.

2016-11-01

In this paper we study the global dynamics of a cancer chemotherapy system presented by de Pillis et al. (2007). This mathematical model describes the interaction between tumor cells, effector-immune cells, circulating lymphocytes and chemotherapy treatment. By applying the localization method of compact invariant sets, we find lower and upper bounds for these three cells populations. Further, we define a bounded domain in R+,04 where all compact invariant sets of the system are located and provide conditions under which this domain is positively invariant. We apply LaSalle's invariance principle and one result concerning two-dimensional competitive systems in order to derive sufficient conditions for tumor clearance and global asymptotic stability of the tumor-free equilibrium point. These conditions are computed by using bounds of the localization domain and they are given in terms of the chemotherapy treatment. Finally, we perform numerical simulations in order to illustrate our results.

THE IMPORTANCE OF BANKING SUPERVISION IN ENSURING FINANCIAL STABILITY

Directory of Open Access Journals (Sweden)

CĂRUNTU GENU ALEXANDRU

2014-12-01

Full Text Available Financial stability plays a vital role in terms of the financial system and the economy as a whole. Analysis and management of risks in the banking sector in order to achieve the financial stability of the whole banking system requires the use of established methods in modern management of risk. The financial crisis has demonstrated certain limits in terms of efficient management of risk. In this respect supervisory authorities have developed a number of methods and techniques to detect, monitor and amount of risk. In the present context, to enhance the stability of the banking system and prevent systemic risk, it is proposed to revise the Basel II Agreement. It was necessary to review the existing prudential regulations defining, embodied in Basel III. This new agreement brings more clarity in the financial and banking sector, addresses a wider range of risks, providing a better regulator

Development of a terminal voltage stabilization system for the FOTIA ...

Indian Academy of Sciences (India)

Abstract. A terminal voltage stabilization system for the folded tandem ion accelerator (FOTIA) was developed and is in continuous use. The system achieves good voltage stabilization, eliminates ground loops and noise interference. It incorporates a correcting circuit for compensating the mains frequency variations in the ...

Assessing Power System Stability Following Load Changes and Considering Uncertainty

Directory of Open Access Journals (Sweden)

D. V. Ngo

2018-04-01

Full Text Available An increase in load capacity during the operation of a power system usually causes voltage drop and leads to system instability, so it is necessary to monitor the effect of load changes. This article presents a method of assessing the power system stability according to the load node capacity considering uncertainty factors in the system. The proposed approach can be applied to large-scale power systems for voltage stability assessment in real-time.

Uniform stability for time-varying infinite-dimensional discrete linear systems

International Nuclear Information System (INIS)

Kubrusly, C.S.

1988-09-01

Stability for time-varying discrete linear systems in a Banach space is investigated. On the one hand, it established a fairly complete collection of necessary and sufficient conditions for uniform asymptotic equistability for input-free systems. This includes uniform and strong power equistability, and uniform and strong l p -equistability, among other technical conditions which also play essential role in stability theory. On other hand, it is shown that uniform asymptotic equistability for input-free systems is equivalent to each of the following concepts of uniform stability for forced systems: l p -input l p -state, c o -input c o -state, bounded-input bounded-state, l p>1 -input bounded-state, c sub (o)-input bounded-state, and convergent-input bounded-state; which are also equivalent to their nonuniform counterparts. For time-varying convergent systems, the above is also equivalent to convergent-input convergent-state stability. The proofs presented here are all ''elementary'' in the sense that they are based essentially only on the Banach-Steinhaus theorem. (autor) [pt

Stability design considerations for mirror support systems in ICF lasers

International Nuclear Information System (INIS)

Tietbohl, G.L.; Sommer, S.C.

1996-10-01

Some of the major components of laser systems used for Inertial Confinement Fusion (ICF) are the large aperture mirrors which direct the path of the laser. These mirrors are typically supported by systems which consist of mirror mounts, mirror enclosures, superstructures, and foundations. Stability design considerations for the support systems of large aperture mirrors have been developed based on the experience of designing and evaluating similar systems at the Lawrence Livermore National Laboratory (LLNL). Examples of the systems developed at LLNL include Nova, the Petawatt laser, Beamlet, and the National Ignition Facility (NIF). The structural design of support systems of large aperture mirrors has typically been controlled by stability considerations in order for the large laser system to meet its performance requirements for alignment and positioning. This paper will discuss the influence of stability considerations and will provide guidance on the structural design and evaluation of mirror support systems in ICF lasers so that this information can be used on similar systems

Microprocessor system for temperature regulation and stabilization

International Nuclear Information System (INIS)

Nguyen Nhi Dien; Rodionov, K.G.

1989-01-01

Microprocessor based system for temperature regulation and stabilization of an operation external object is described. The system has the direct current amplifier working according to modulator-demodulator principle. The overal gain is 100, 1000, 2000. The maximum output signal is ±10 V. The power amplifier is a thyristor one and its line voltage is 220 V, 50 Hz. The output power is 0-2 kVA. The microcontroller has a remote display terminal. Data input is 8 and data output is one. Input and output voltage is ±(0-10) V. The preselection time for stabilization is within 1 s - 18 h. The program algorithm is given. 5 figs.; 1 tab

System specification for the plutonium stabilization and packaging system

International Nuclear Information System (INIS)

1996-01-01

This document describes functional design requirements for the Plutonium Stabilization and Packaging System (Pu SPS), as required by DOE contract DE-AC03-96SF20948 through contract modification 9 for equipment in Building 707 at Rocky Flats Environmental Technology Site (RFETS)

Indefinite damping in mechanical systems and gyroscopic stabilization

DEFF Research Database (Denmark)

Kliem, Wolfhard; Pommer, Christian

2009-01-01

This paper deals with gyroscopic stabilization of the unstable system Mx + D(x) over dot + K-x = 0, with positive definite mass and stiffness matrices M and K, respectively, and an indefinite damping matrix D. The main question if for which skew-symmetric matrices G the system Mx (D+ G)(x) over dot...... + K-x = 0 can become stable? After investigating special cases we find an appropriat solution of the Lyapunov matrix equation for the general case. Examples show the deviation of the stability limit found by the Lyapunov method from the exact value....

Transient stability probability evaluation of power system incorporating with wind farm and SMES

DEFF Research Database (Denmark)

Fang, Jiakun; Miao, Lu; Wen, Jinyu

2013-01-01

Large scale renewable power generation brings great challenges to the power system operation and stabilization. Energy storage is one of the most important technologies to face the challenges. This paper proposes a method for transient stability probability evaluation of power system with wind farm...... and SMES. Firstly, a modified 11-bus test system with both wind farm and SMES has been implemented. The wind farm is represented as a doubly fed induction generator (DFIG). Then a stochastic-based approach to evaluate the probabilistic transient stability index of the power system is presented. Uncertain...... the probability indices. With the proposed method based on Monte-Carlo simulation and bisection method, system stability is "measured". Quantitative relationship of penetration level, SMES coil size and system stability is established. Considering the stability versus coil size to be the production curve...

Simulation for transient stability study of the Taiwan power system - a nuclear majority system

International Nuclear Information System (INIS)

Huang, J.C.C.

1984-01-01

A transient stability program was developed for the Taiwan Power Company, which has a high proportion of nuclear generation in its power system. This program offers a new territory to investigate nuclear plant effects on the power system transient stability. This program also provides a high speed tool for the Taipower system operational planning. A generalized procedure of synchronous machine modeling for a large-scale stability study is presented. The merits and weaknesses of machine modeling can be comprehended through each item of this procedure. Three types of nonlinear synchronous machine modeling implemented into this stability program are derived by following this procedure. A robust subroutine was derived to perform the fourth order Runge-Kutta integration method, making the software programming neat and systematical. For simulating the nuclear plant influence on the system, this program implemented an additional four functions: load-limit operation simulated by a low-value gate in the governor model, bypass valve capacity monitored by sending out a warning message, rotor overspeed protection relay, and generator anti-motoring relay

Quantifying Stability in Complex Networks: From Linear to Basin Stability

Science.gov (United States)

Kurths, Jürgen

The human brain, power grids, arrays of coupled lasers and the Amazon rainforest are all characterized by multistability. The likelihood that these systems will remain in the most desirable of their many stable states depends on their stability against significant perturbations, particularly in a state space populated by undesirable states. Here we claim that the traditional linearization-based approach to stability is in several cases too local to adequately assess how stable a state is. Instead, we quantify it in terms of basin stability, a new measure related to the volume of the basin of attraction. Basin stability is non-local, nonlinear and easily applicable, even to high-dimensional systems. It provides a long-sought-after explanation for the surprisingly regular topologies of neural networks and power grids, which have eluded theoretical description based solely on linear stability. Specifically, we employ a component-wise version of basin stability, a nonlinear inspection scheme, to investigate how a grid's degree of stability is influenced by certain patterns in the wiring topology. Various statistics from our ensemble simulations all support one main finding: The widespread and cheapest of all connection schemes, namely dead ends and dead trees, strongly diminish stability. For the Northern European power system we demonstrate that the inverse is also true: `Healing' dead ends by addition of transmission lines substantially enhances stability. This indicates a crucial smart-design principle for tomorrow's sustainable power grids: add just a few more lines to avoid dead ends. Further, we analyse the particular function of certain network motifs to promote the stability of the system. Here we uncover the impact of so-called detour motifs on the appearance of nodes with a poor stability score and discuss the implications for power grid design. Moreover, it will be shown that basin stability enables uncovering the mechanism for explosive synchronization and

Learning and Understanding System Stability Using Illustrative Dynamic Texture Examples

Science.gov (United States)

Liu, Huaping; Xiao, Wei; Zhao, Hongyan; Sun, Fuchun

2014-01-01

System stability is a basic concept in courses on dynamic system analysis and control for undergraduate students with computer science backgrounds. Typically, this was taught using a simple simulation example of an inverted pendulum. Unfortunately, many difficult issues arise in the learning and understanding of the concepts of stability,…

Stability and boundary stabilization of 1-D hyperbolic systems

CERN Document Server

Bastin, Georges

2016-01-01

This monograph explores the modeling of conservation and balance laws of one-dimensional hyperbolic systems using partial differential equations. It presents typical examples of hyperbolic systems for a wide range of physical engineering applications, allowing readers to understand the concepts in whichever setting is most familiar to them. With these examples, it also illustrates how control boundary conditions may be defined for the most commonly used control devices. The authors begin with the simple case of systems of two linear conservation laws and then consider the stability of systems under more general boundary conditions that may be differential, nonlinear, or switching. They then extend their discussion to the case of nonlinear conservation laws and demonstrate the use of Lyapunov functions in this type of analysis. Systems of balance laws are considered next, starting with the linear variety before they move on to more general cases of nonlinear ones. They go on to show how the problem of boundary...

Epicardial clip occlusion of the left atrial appendage during cardiac surgery provides optimal surgical results and long-term stability.

Science.gov (United States)

Kurfirst, Vojtech; Mokrácek, Aleš; Canádyová, Júlia; Frána, Radim; Zeman, Petr

2017-07-01

Occlusion of the left atrial appendage (LAA) has become an integral and important part of the surgical treatment of atrial fibrillation. Different methods of surgical occlusion of the LAA have been associated with varying levels of short- and long-term success for closure. The purpose of this study was to evaluate long-term results of epicardial placement and endocardial occlusion in patients undergoing cardiac operative procedures. A total of 101 patients (average age 65.7 years) undergoing cardiac operative procedures with the epicardial AtriClip Exclusion System of the LAA were enrolled in the study. The AtriClip was placed via a sternotomy or a thoracotomy or from a thoracoscopic approach. Postoperative variables, such as thromboembolic events, clip stability and endocardial leakage around the device, were examined by transoesophageal echocardiography (TEE) and/or computed tomography. Perioperative clip implantation was achieved in 98% of patients. TEE and/or computed tomography conducted during the follow-up period, comprising 1873 patient-months with a mean duration of 18 ± 11 months, revealed no clip migration, no leakage around the device and no clot formation near the remnant cul-de-sac. During the follow-up period, 4 of the cardiac patients experienced transitory ischaemic attacks, whereas no patient experienced a cerebrovascular attack. The Epicardial AtriClip Exclusion System of the LAA appears to be a feasable and safe operative method with a high success rate. Long-term follow-up confirmed clip stability, complete occlussion of the LAA and absence of any atrial fibrilation-related thromboembolic events. These results need to be confirmed by a larger, multicentre study. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

General Output Feedback Stabilization for Fractional Order Systems: An LMI Approach

Directory of Open Access Journals (Sweden)

Yiheng Wei

2014-01-01

Full Text Available This paper is concerned with the problem of general output feedback stabilization for fractional order linear time-invariant (FO-LTI systems with the fractional commensurate order 0<α<2. The objective is to design suitable output feedback controllers that guarantee the stability of the resulting closed-loop systems. Based on the slack variable method and our previous stability criteria, some new results in the form of linear matrix inequality (LMI are developed to the static and dynamic output feedback controllers synthesis for the FO-LTI system with 0<α<1. Furthermore, the results are extended to stabilize the FO-LTI systems with 1≤α<2. Finally, robust output feedback control is discussed. Numerical examples are given to illustrate the effectiveness of the proposed design methods.

Predictor-based stabilization for chained form systems with input time delay

Directory of Open Access Journals (Sweden)

Mnif Faïçal

2016-12-01

Full Text Available This note addresses the stabilization problem of nonlinear chained-form systems with input time delay. We first employ the so-called σ-process transformation that renders the feedback system under a linear form. We introduce a particular transformation to convert the original system into a delay-free system. Finally, we apply a state feedback control, which guarantees a quasi-exponential stabilization to all the system states, which in turn converge exponentially to zero. Then we employ the so-called -type control to achieve a quasi-exponential stabilization of the subsequent system. A simulation example illustrated on the model of a wheeled mobile robot is provided to demonstrate the effectiveness of the proposed approach.

Morocco; Financial System Stability Assessment: Update

OpenAIRE

International Monetary Fund

2008-01-01

This paper presents an update to the Financial System Stability Assessment on Morocco. Major reforms have been achieved since the 2002 Financial Sector Assessment Program (FSAP) within a policy of actively promoting economic and financial sector opening. The 2002 FSAP recommendations have been largely implemented. Although the financial system is stable and considerably more robust than in the past, the liberalization of capital flows and increased exchange rate flexibility present challenges...

Stability Analysis and Stabilization of T-S Fuzzy Delta Operator Systems with Time-Varying Delay via an Input-Output Approach

Directory of Open Access Journals (Sweden)

Zhixiong Zhong

2013-01-01

Full Text Available The stability analysis and stabilization of Takagi-Sugeno (T-S fuzzy delta operator systems with time-varying delay are investigated via an input-output approach. A model transformation method is employed to approximate the time-varying delay. The original system is transformed into a feedback interconnection form which has a forward subsystem with constant delays and a feedback one with uncertainties. By applying the scaled small gain (SSG theorem to deal with this new system, and based on a Lyapunov Krasovskii functional (LKF in delta operator domain, less conservative stability analysis and stabilization conditions are obtained. Numerical examples are provided to illustrate the advantages of the proposed method.

The rhetoric of organizational stability and creativity: an analysis of the term ‘platform’

Directory of Open Access Journals (Sweden)

Larry D. Browning

2013-11-01

Full Text Available This article analyses the term platform as it surfaced in interview data from Norway and the United States that was collected in a field research project on organizational technology use. Through an inductive analysis of the term’s use in six interviews, a conceptualization of the term reveals it to be rhetorical in nature, expressing the interplay between stability and creativity. In order to explain the rhetorical aspects we describe, the authors turn to the rhetorical critic Kenneth Burke’s work to aid in conceptualizing the term, specifically his understanding of scene and agency. The authors present the conceptualization to help researchers on two levels. On the micro-level, we offer an analysis of the term platform. On the macro-level, we illustrate how grounded theory can help locate other terms that have unacknowledged salience to researchers, consultants, and interviewees. 

Competition and system stability -- The reward and the penalty

International Nuclear Information System (INIS)

Mansour, Y.

2000-01-01

The business protocols and rules of the competitive electricity market are resulting in fragmentation of the historical vertically integrated structures. Electric services are offered at either cost or market-based prices depending on their type and the level of competition in a particular product. System stabilizing measures are essential for maintaining system security, yet their value is either underestimated or not understood. This paper describes practical methods to quantify the value of some of the stabilizing measures and ways to ensure maintaining the dynamic security of the power systems through business procedures and monetary sanctions

Transient Stability Improvement of IEEE 9 Bus System Using Power World Simulator

Directory of Open Access Journals (Sweden)

Kaur Ramandeep

2016-01-01

Full Text Available The improvement of transient stability of power system was one of the most challenging research areas in power engineer.The main aim of this paper was transient stability analysis and improvement of IEEE 9 bus system. These studies were computed using POWER WORLD SIMULATOR. The IEEE 9 bus system was modelled in power world simulator and load flow studies were performed to determine pre-fault conditions in the system using Newton-Raphson method. The transient stability analysis was carried out using Runga method during three-phase balanced fault. For the improvement transient stability, the general methods adopted were fast acting exciters, FACT devices and addition of parallel transmission line. These techniques play an important role in improving the transient stability, increasing transmission capacity and damping low frequency oscillations.

A real-time BWR stability measurement system

International Nuclear Information System (INIS)

March-Leuba, J.; King, W.T.

1988-01-01

This paper describes the characteristics of a portable, real-time system used for nonperturbational measurements of stability in boiling water reactors. The algorithm used in this system estimates the closed-loop asymptotic decay ratio using only the naturally occurring neutron noise and it is based on the univariate autoregressive methodology. (author)

Mittag-Leffler Stability Theorem for Fractional Nonlinear Systems with Delay

Directory of Open Access Journals (Sweden)

S. J. Sadati

2010-01-01

Full Text Available Fractional calculus started to play an important role for analysis of the evolution of the nonlinear dynamical systems which are important in various branches of science and engineering. In this line of taught in this paper we studied the stability of fractional order nonlinear time-delay systems for Caputo's derivative, and we proved two theorems for Mittag-Leffler stability of the fractional nonlinear time delay systems.

Sensitivity of system stability to model structure

Science.gov (United States)

Hosack, G.R.; Li, H.W.; Rossignol, P.A.

2009-01-01

A community is stable, and resilient, if the levels of all community variables can return to the original steady state following a perturbation. The stability properties of a community depend on its structure, which is the network of direct effects (interactions) among the variables within the community. These direct effects form feedback cycles (loops) that determine community stability. Although feedback cycles have an intuitive interpretation, identifying how they form the feedback properties of a particular community can be intractable. Furthermore, determining the role that any specific direct effect plays in the stability of a system is even more daunting. Such information, however, would identify important direct effects for targeted experimental and management manipulation even in complex communities for which quantitative information is lacking. We therefore provide a method that determines the sensitivity of community stability to model structure, and identifies the relative role of particular direct effects, indirect effects, and feedback cycles in determining stability. Structural sensitivities summarize the degree to which each direct effect contributes to stabilizing feedback or destabilizing feedback or both. Structural sensitivities prove useful in identifying ecologically important feedback cycles within the community structure and for detecting direct effects that have strong, or weak, influences on community stability. The approach may guide the development of management intervention and research design. We demonstrate its value with two theoretical models and two empirical examples of different levels of complexity. ?? 2009 Elsevier B.V. All rights reserved.

Stabilization challenges and formulation strategies associated with oral biologic drug delivery systems.

Science.gov (United States)

Truong-Le, Vu; Lovalenti, Phillip M; Abdul-Fattah, Ahmad M

2015-10-01

Delivery of proteins to mucosal tissues of GI tract typically utilize formulations which protect against proteolysis and target the mucosal tissues. Using case studies from literature and the authors' own work, the in-process stability and solid state storage stability of biopharmaceuticals formulated in delivery systems designed for oral delivery to the GI tract will be reviewed. Among the range of delivery systems, biodegradable polymer systems for protection and controlled release of proteins have been the most studied; hence these systems will be covered in greater depth. These delivery systems include polymeric biodegradable microspheres or nanospheres that contain proteins or vaccines, which are designed to reduce the number of administrations/inoculations and the total protein dose required to achieve the desired biological effect. Specifically, this review will include a landscape survey of the systems that have been studied, the manufacturing processes involved, stability through the manufacturing process, key pharmaceutical formulation parameters that impact stability of the encased proteins, and storage stability of the encapsulated proteins in these delivery systems. Copyright © 2015 Elsevier B.V. All rights reserved.

On stabilization of linear systems with stochastic disturbances and input saturation

NARCIS (Netherlands)

Stoorvogel, A.A.; Weiland, S.; Saberi, A.

2004-01-01

It is well-known that for linear systems internal asymptotic stability implies external stability in the sense that when the external input is in Lp then also the state will be in Lp. However, for the control of linear systems with saturation where the controlled system is nonlinear this implication

Computation of robustly stabilizing PID controllers for interval systems.

Science.gov (United States)

Matušů, Radek; Prokop, Roman

2016-01-01

The paper is focused on the computation of all possible robustly stabilizing Proportional-Integral-Derivative (PID) controllers for plants with interval uncertainty. The main idea of the proposed method is based on Tan's (et al.) technique for calculation of (nominally) stabilizing PI and PID controllers or robustly stabilizing PI controllers by means of plotting the stability boundary locus in either P-I plane or P-I-D space. Refinement of the existing method by consideration of 16 segment plants instead of 16 Kharitonov plants provides an elegant and efficient tool for finding all robustly stabilizing PID controllers for an interval system. The validity and relatively effortless application of presented theoretical concepts are demonstrated through a computation and simulation example in which the uncertain mathematical model of an experimental oblique wing aircraft is robustly stabilized.

Performance of Power System Stabilizer (UNITROL D) in Benghazi North Power Plant

OpenAIRE

T. Hussein

2011-01-01

The use of power system stabilizers (PSSs) to damp power system swing mode of oscillations is practical important. Our purpose is to retune the power system stabilizer (PSS1A) parameters in Unitrol D produced by ABB– was installed in 1995in Benghazi North Power Plants (BNPPs) at General Electricity Company of Libya (GECOL). The optimal values of the power system stabilizer (PSS1A) parameters are determined off-line by a particle swarm optimization technique (PSO). The obj...

System Design Description PFP Thermal Stabilization

International Nuclear Information System (INIS)

RISENMAY, H.R.

2000-01-01

The purpose of this document is to provide a system design description (SDD) and design basis for the Plutonium Finishing Plant (PFP) Thermal Stabilization project. The chief objective of the SDD is to document the Structures, Systems, and Components (SSCs) that establish and maintain the facility Safety Envelope necessary for normal safe operation of the facility; as identified in the FSAR, the OSRs, and Safety Assessment Documents (SADs). This safety equipment documentation should satisfy guidelines for the SDD given in WHC-SD-CP-TI-18 1, Criteria for Identification and Control of Equipment Necessary for Preservation of the Safety Envelope and Safe Operation of PFP. The basis for operational, alarm response, maintenance, and surveillance procedures are also identified and justified in this document. This document and its appendices address the following elements of the PFP Thermal Stabilization project: Functional and design requirements; Design description; Safety Envelope Analysis; Safety Equipment Class; and Operational, maintenance and surveillance procedures

The electric power engineering handbook power system stability and control

CERN Document Server

Grisby, Leonard L

2012-01-01

With contributions from worldwide leaders in the field, Power System Stability and Control, Third Edition (part of the five-volume set, The Electric Power Engineering Handbook) updates coverage of recent developments and rapid technological growth in essential aspects of power systems. Edited by L.L. Grigsby, a respected and accomplished authority in power engineering, and section editors Miroslav Begovic, Prabha Kundur, and Bruce Wollenberg, this reference presents substantially new and revised content. Topics covered include: * Power System Protection * Power System Dynamics and Stability *

Stabilization and regulation of nonlinear systems a robust and adaptive approach

CERN Document Server

Chen, Zhiyong

2015-01-01

The core of this textbook is a systematic and self-contained treatment of the nonlinear stabilization and output regulation problems. Its coverage embraces both fundamental concepts and advanced research outcomes and includes many numerical and practical examples. Several classes of important uncertain nonlinear systems are discussed. The state-of-the art solution presented uses robust and adaptive control design ideas in an integrated approach which demonstrates connections between global stabilization and global output regulation allowing both to be treated as stabilization problems. Stabilization and Regulation of Nonlinear Systems takes advantage of rich new results to give students up-to-date instruction in the central design problems of nonlinear control, problems which are a driving force behind the furtherance of modern control theory and its application. The diversity of systems in which stabilization and output regulation become significant concerns in the mathematical formulation of practical contr...

Long-Term Stability of Scores on the Wechsler Intelligence Scale for Children-Fourth Edition in Children with Learning Disabilities

Science.gov (United States)

Lander, Jenny

2010-01-01

The present investigation explored the stability of scores on the Wechsler Intelligence Scale for Children-IV (WISC-IV) over approximately a three-year period. Previous research has suggested that some children with Learning Disabilities (LD) do not demonstrate long-term stability of intelligence. Legally, school districts are no longer required…

Stability and Bifurcation Analysis in a Maglev System with Multiple Delays

Science.gov (United States)

Zhang, Lingling; Huang, Jianhua; Huang, Lihong; Zhang, Zhizhou

This paper considers the time-delayed feedback control for Maglev system with two discrete time delays. We determine constraints on the feedback time delays which ensure the stability of the Maglev system. An algorithm is developed for drawing a two-parametric bifurcation diagram with respect to two delays τ1 and τ2. Direction and stability of periodic solutions are also determined using the normal form method and center manifold theory by Hassard. The complex dynamical behavior of the Maglev system near the domain of stability is confirmed by exhaustive numerical simulation.

Dynamic analysis and electronic circuit implementation of a novel 3D autonomous system without linear terms

Science.gov (United States)

Kengne, J.; Jafari, S.; Njitacke, Z. T.; Yousefi Azar Khanian, M.; Cheukem, A.

2017-11-01

Mathematical models (ODEs) describing the dynamics of almost all continuous time chaotic nonlinear systems (e.g. Lorenz, Rossler, Chua, or Chen system) involve at least a nonlinear term in addition to linear terms. In this contribution, a novel (and singular) 3D autonomous chaotic system without linear terms is introduced. This system has an especial feature of having two twin strange attractors: one ordinary and one symmetric strange attractor when the time is reversed. The complex behavior of the model is investigated in terms of equilibria and stability, bifurcation diagrams, Lyapunov exponent plots, time series and Poincaré sections. Some interesting phenomena are found including for instance, period-doubling bifurcation, antimonotonicity (i.e. the concurrent creation and annihilation of periodic orbits) and chaos while monitoring the system parameters. Compared to the (unique) case previously reported by Xu and Wang (2014) [31], the system considered in this work displays a more 'elegant' mathematical expression and experiences richer dynamical behaviors. A suitable electronic circuit (i.e. the analog simulator) is designed and used for the investigations. Pspice based simulation results show a very good agreement with the theoretical analysis.

Dynamic Voltage Stability Studies using a Modified IEEE 30-Bus System

Directory of Open Access Journals (Sweden)

Oluwafemi Emmanuel Oni

2016-09-01

Full Text Available Power System stability is an essential study in the planning and operation of an efficient, economic, reliable and secure electric power system because it encompasses all the facet of power systems operations, from planning, to conceptual design stages of the project as well as during the systems operating life span. This paper presents different scenario of power system stability studies on a modified IEEE 30-bus system which is subjected to different faults conditions. A scenario whereby the longest high voltage alternating current (HVAC line is replaced with a high voltage direct current (HVDC line was implemented. The results obtained show that the HVDC line enhances system stability more compared to the contemporary HVAC line. Dynamic analysis using RMS simulation tool was used on DigSILENT PowerFactory.

Design of rapid prototype of UAV line-of-sight stabilized control system

Science.gov (United States)

Huang, Gang; Zhao, Liting; Li, Yinlong; Yu, Fei; Lin, Zhe

2018-01-01

The line-of-sight (LOS) stable platform is the most important technology of UAV (unmanned aerial vehicle), which can reduce the effect to imaging quality from vibration and maneuvering of the aircraft. According to the requirement of LOS stability system (inertial and optical-mechanical combined method) and UAV's structure, a rapid prototype is designed using based on industrial computer using Peripheral Component Interconnect (PCI) and Windows RTX to exchange information. The paper shows the control structure, and circuit system including the inertial stability control circuit with gyro and voice coil motor driven circuit, the optical-mechanical stability control circuit with fast-steering-mirror (FSM) driven circuit and image-deviation-obtained system, outer frame rotary follower, and information-exchange system on PC. Test results show the stability accuracy reaches 5μrad, and prove the effectiveness of the combined line-of-sight stabilization control system, and the real-time rapid prototype runs stable.

Effect Mechanism of Penstock on Stability and Regulation Quality of Turbine Regulating System

Directory of Open Access Journals (Sweden)

Wencheng Guo

2014-01-01

Full Text Available This paper studies the effect mechanism of water inertia and head loss of penstock on stability and regulation quality of turbine regulating system with surge tank or not and proposes the construction method of equivalent model of regulating system. Firstly, the complete linear mathematical model of regulating system is established. Then, the free oscillation equation and time response of the frequency that describe stability and regulation quality, respectively, are obtained. Finally, the effects of penstock are analysed by using stability region and response curves. The results indicate that the stability and regulation quality of system without surge tank are determined by time response of frequency which only depends on water hammer wave in penstock, while, for system with surge tank, the time response of frequency depending on water hammer wave in penstock and water-level fluctuation in surge tank jointly determines the stability and regulation quality. Water inertia of penstock mainly affects the stability and time response of frequency of system without surge tank as well as the stability and head wave of time response of frequency with surge tank. Head loss of penstock mainly affects the stability and tail wave of time response of frequency with surge tank.

14 CFR 25.672 - Stability augmentation and automatic and power-operated systems.

Science.gov (United States)

2010-01-01

... power-operated systems. 25.672 Section 25.672 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Construction Control Systems § 25.672 Stability augmentation and automatic and power-operated systems. If the functioning of stability augmentation or other automatic or power-operated systems is necessary to show...

Finite-Time Stability and Controller Design of Continuous-Time Polynomial Fuzzy Systems

Directory of Open Access Journals (Sweden)

Xiaoxing Chen

2017-01-01

Full Text Available Finite-time stability and stabilization problem is first investigated for continuous-time polynomial fuzzy systems. The concept of finite-time stability and stabilization is given for polynomial fuzzy systems based on the idea of classical references. A sum-of-squares- (SOS- based approach is used to obtain the finite-time stability and stabilization conditions, which include some classical results as special cases. The proposed conditions can be solved with the help of powerful Matlab toolbox SOSTOOLS and a semidefinite-program (SDP solver. Finally, two numerical examples and one practical example are employed to illustrate the validity and effectiveness of the provided conditions.

On the stability of boundary layers in gas mantle systems

International Nuclear Information System (INIS)

Ohlsson, D.

1978-10-01

In this thesis a systematic investigation of the stability properties of the partially ionized boundary regions of gas mantle systems for a large class of dissipative magneto-hydrodynamic modes is presented. In the partially ionized boundary regions of gas mantle systems several strong stabilizing mechanisms arise due to coupling between various dissipative effects in certain parameter regions. The presence of neutral gas strongly enhances the stabilizing effects in a dual fashion. First in an indirect way by cooling the edge region and second in a direct way by enhancing viscous and heat conduction effects. It has, however, to be pointed out that exceptions from this general picture may be found. The stabilizing influence of neutral gas on a large class of electrostatic as well as electromagnetic modes in the boundary regions of gas blanket systems is contrary to what has been found in low density weakly ionized plasmas. In these latter cases presence of neutral gas has even been found to be responsible for the onset of entirely new classes of instabilities. Thus there is no universal stabilizing or destabilizing effect associated with plasma-neutral gas interaction effects. (author)

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)

Decentralized linear quadratic power system stabilizers for multi ...

Indian Academy of Sciences (India)

Introduction. Modern excitation systems considerably enhance the overall transient stability of power systems ..... to the local bus rather than the angle δ measured with respect to the remote bus. ... With this in view, the linear and nonlinear per-.

Stability of Folate and Vitamin B 12 in Human Serum after Long-Term Storage: A Follow-Up after 13 Years

NARCIS (Netherlands)

Jansen, Eugène H. J. M.; Beekhof, Piet K.; Centre for Health Protection, National Institute of Public Health and the Environment, P.O. Box 1, 3720 BA Bilthoven, Netherlands; Centre for Health Protection, National Institute of Public Health and the Environment, P.O. Box 1, 3720 BA Bilthoven, Netherlands

2018-01-01

In epidemiological and nutrition research, it is very important to evaluate the stability of biomarkers as function of both storage time and temperature. In this study, the stability of folate and vitamin B 12 in human serum samples has been tested after long-term

Self-organizing dynamic stability of far-from-equilibrium biological systems

Science.gov (United States)

Ivanitskii, G. R.

2017-10-01

One indication of the stability of a living system is the variation of the system’s characteristic time scales. Underlying the stability mechanism are the structural hierarchy and self-organization of systems, factors that give rise to a positive (accelerating) feedback and a negative (braking) feedback. Information processing in the brain cortex plays a special role in highly organized living organisms.

Stabilization and synchronization of Genesio-Tesi system via single variable feedback controller

International Nuclear Information System (INIS)

Wang Guangming

2010-01-01

This Letter investigates the stabilization and synchronization of Genesio-Tesi systems. Firstly, modifying the previous method, we stabilize the Genesio-Tesi system. Then, we synchronize two identical Genesio chaotic system by extending the obtained stabilization results. To the best of our knowledge, the above controllers obtained in this Letter are simpler than those obtained in the existing results. Finally, numerical simulations verify the effectiveness and the validity of the above theoretical results.

ON THE STABILIZATION OF THE LINEAR HYBRID SYSTEM STRUCTURE

Directory of Open Access Journals (Sweden)

Kirillov

2014-11-01

Full Text Available The linear control hybrid system, consisting of a fi- nite set of subsystems (modes having different dimensions, is considered. The moments of reset time are determined by some complementary function – evolutionary time. This function satisfies the special complementary ordinary differential equation. The mode stabilization problem is solved for some class of piecewise linear controls. The method of stabilization relies on the set of invariant planes, the existence of which is due to the special form of the hybrid system.

Evaluating the Financial Stability of Banking System, Considering the Emergence Property

Directory of Open Access Journals (Sweden)

Lesik Vitaliy O.

2017-03-01

Full Text Available The article is concerned with analyzing the existing approaches to evaluation of the financial stability of banking system, substantiating the expedience of accounting, and generalizing the characteristics of the emergence property to determine its level. The article considers the interrelation of concepts of «financial stability» and «financial sustainability», the necessity of their correlation, taking account of the time factor, has been substantiated. A critical analysis of the approaches to evaluating the financial stability of banking system has been carried out, their eligibility according to the criteria of accounting of the identification attributes of systemacity and the analytical data aggregation has been examined. To determine the status of banking system as a system phenomenon, the necessity of carrying out an evaluation of its financial stability on the basis of the emergence approach has been substantiated, including the following directions: intensity of credit and financial interaction in the interbank market; functional load of the banking system as to ensuring the macroeconomic development; structural changes and financial disparities in the banking system; scale effects that arise as a consequence of change in the main financial parameters of the system banks.

Achievement of high availability in long-term operation and upgrading plan of the LHD superconducting system

International Nuclear Information System (INIS)

Imagawa, S.; Yanagi, N.; Hamaguchi, S.

2006-10-01

The Large Helical Device (LHD) that has been demonstrating high performance of heliotron plasma is the world's largest superconducting system. Availability higher than 98% has been achieved in a long-term continuous operation both in the cryogenic system and in the power supply system. It will be owing not only to the robustness of the systems but also to efforts of maintenance and operation. One big problem is shortage of cryogenic stability of a pair of pool-cooled helical coils. Composite conductors had been developed to attain the sufficient stability at high current density. However, it was revealed that a normal-zone could propagate below the cold-end recovery current by additional heat generation due to the slow current diffusion into a thick pure aluminium stabilizer. Besides, a novel detection system with pick-up coils along the helical coils revealed that normal-zones were initiated near the bottom of the coil where the field is not the highest. Therefore, the cooling condition around the innermost layers, the high field area, will be deteriorated at the bottom of the coil by bubbles gathered by buoyancy. In order to raise the operating currents, methods for improving the cryogenic stability have been examined, and stability tests have been carried out with a model coil and small coil samples. The coil temperature is planned to be lowered from 4.4 K to 3.5 K, and the operating current is expected to be increased from 11.0 kA to 12.0 kA that corresponds to 3.0 T at the major radius of 3.6 m. (author)

One-step transversal palatal distraction and maxillary repositioning: technical considerations, advantages, and long-term stability.

Science.gov (United States)

Cortese, Antonio; Savastano, Mauro; Savastano, Germano; Claudio, Pier Paolo

2011-09-01

Transversal maxillary hypoplasia in adolescence is a frequently seen pathology, which can be treated with a combination of surgery and orthodontic treatment to widen the maxilla in skeletally matured patients.We evaluated the advantages of a new surgical technique: Le Fort I distraction osteogenesis using a bone-borne device. Because relapse is one of the main problems in surgical maxillary expansion, long-term stability of this new technique was evaluated. Data from 4 adult patients with maxillary restriction, class III malocclusion, or maxillary malposition were collected preoperatively, 4 months after distraction, and 5 years after distraction. Measurements were recorded on dental models to detect palatal expansion at dental level; cephalograms by lateral and posteroanterior plane were analyzed to detect maxillary movements. Maxillary measurements were substantially stable 5 years after distractions. Only minor dental movements occurred at the dental analysis after 5 years related to a lack of orthodontic contention without any compromise of the dental result (no crossbite relapse and class I stability). Le Fort I with down-fracture for expansion and repositioning by bone-borne distractor device can [corrected] be used to simultaneously widen, advance, and vertically reposition the maxilla without causing healing problems, particularly using a rigid distraction device. Long-term stability can be achieved; however, further studies with a larger number of patients will be necessary for better evaluation.

Frequency Stability Improvement of Low Inertia Systems Using Synchronous Condensers

DEFF Research Database (Denmark)

Nguyen, Ha Thi; Yang, Guangya; Nielsen, Arne Hejde

2016-01-01

of converter interfaced components (wind turbine, HVDC, and Photovoltaic) may have negative effects on the stability of the power system. These components do not have enough inertia response to control frequency excursion, so the power grid can depend on few synchronous machines for frequency regulation...... and reduce the system inertia. Consequently, the frequency stability of the system will be easily jeopardized. To address these issues, the paper studies frequency characteristics of future Western Danish renewable-based system that uses a majority of wind turbine generators. Different scenarios of wind...

Stability properties of nonlinear dynamical systems and evolutionary stable states

Energy Technology Data Exchange (ETDEWEB)

Gleria, Iram, E-mail: iram@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-AL (Brazil); Brenig, Leon [Faculté des Sciences, Université Libre de Bruxelles, 1050 Brussels (Belgium); Rocha Filho, Tarcísio M.; Figueiredo, Annibal [Instituto de Física and International Center for Condensed Matter Physics, Universidade de Brasília, 70919-970 Brasília-DF (Brazil)

2017-03-18

Highlights: • We address the problem of equilibrium stability in a general class of non-linear systems. • We link Evolutionary Stable States (ESS) to stable fixed points of square quasi-polynomial (QP) systems. • We show that an interior ES point may be related to stable interior fixed points of QP systems. - Abstract: In this paper we address the problem of stability in a general class of non-linear systems. We establish a link between the concepts of asymptotic stable interior fixed points of square Quasi-Polynomial systems and evolutionary stable states, a property of some payoff matrices arising from evolutionary games.

Short-term facilitation may stabilize parametric working memory trace

Directory of Open Access Journals (Sweden)

Vladimir eItskov

2011-10-01

Full Text Available Networks with continuous set of attractors are considered to be a paradigmatic model for parametric working memory, but require fine-tuning of connections and are thus structurally unstable. Here we analyzed the network with ring attractor, where connections are not perfectly tuned and the activity state therefore drifts in the absence of the stabilizing stimulus. We derive an analytical expression for the drift dynamics and conclude that the network cannot function as working memory for a period of several seconds, a typical delay time in monkey memory experiments. We propose that short-term synaptic facilitation in recurrent connections significantly improves the robustness of the model by slowing down the drift of activity bump. Extending the calculation of the drift velocity to network with synaptic facilitation, we conclude that facilitation can slow down the drift by a large factor, rendering the network suitable as a model of working memory.

Stability of detecting system using NaI(Tl)

International Nuclear Information System (INIS)

Zhuo Yunshang; Lei Zhangyun; Zen Yu; Gong Hua

1996-01-01

A detecting system using NaI(Tl) is widely used in research and industry of nuclear science and other fields. For providing the high accuracy and working well under inclement environment, the stability of detecting system using NaI(Tl) is very important. The variation of environment temperature, the change of counting rate and long time continuous working of detector will cause un-negligible effect on the measurement. Three approaches were used. They are: 1) temperature control (It makes the effect of the variation of environment temperature on the measurement negligible.); 2) spectrum stabilizing (It adjust the peak position of the spectrum when the counting rate changes.); and 3) auto-checking and adjusting (It adjusts the drift of the NaI(Tl) detecting system when it works continuously)

Annual stability evaluation of Waste Isolation Pilot Plant

International Nuclear Information System (INIS)

1993-06-01

A stability evaluation of the underground workings of the Waste Isolation Pilot Plant (WIPP) was completed by the US Bureau of Mines' WIPP evaluation committee. This work included a critical evaluation of the processes employed at WIPP to ensure stability, an extensive review of available deformation measurements, a 3-day site visit, and interviews with the Department of Energy (DOE) and Westinghouse staff. General ground control processes are in place at WIPP to minimize the likelihood that major stability problems will go undetected. To increase confidence in both short- and long-term stability throughout the site (underground openings and shafts), ground stability monitoring systems, mine layout design, support systems and data analyses must be continuously improved. Such processes appear to be in place at WIPP and are discussed in this paper

Study of the effect of aggressive media on the long-term stability of reinforced plates

International Nuclear Information System (INIS)

Zelentsov, D.G.; Pochtman, Yu.M.

1995-01-01

Many important load-bearing structural elements that operate in agressive media are subjected to simultaneous mechanical and chemical attack. The current status of the problem of designing such members is adequately reflected. It follows from that only a few studies have been devoted to the long-term stability of reinforced plates in aggressive media, and most of them were based on structurally orthotropic theory. Such an approach makes it impossible to construct an adequate model of the deformation process. In particular, it precludes allowance for the effect of the discreteness of the reinforcement on plate stability and determination of changes in the character of deformation of the plate during service

Byzantine-fault tolerant self-stabilizing protocol for distributed clock synchronization systems

Science.gov (United States)

Malekpour, Mahyar R. (Inventor)

2010-01-01

A rapid Byzantine self-stabilizing clock synchronization protocol that self-stabilizes from any state, tolerates bursts of transient failures, and deterministically converges within a linear convergence time with respect to the self-stabilization period. Upon self-stabilization, all good clocks proceed synchronously. The Byzantine self-stabilizing clock synchronization protocol does not rely on any assumptions about the initial state of the clocks. Furthermore, there is neither a central clock nor an externally generated pulse system. The protocol converges deterministically, is scalable, and self-stabilizes in a short amount of time. The convergence time is linear with respect to the self-stabilization period.

Asymptotic stability estimates near an equilibrium point

Science.gov (United States)

Dumas, H. Scott; Meyer, Kenneth R.; Palacián, Jesús F.; Yanguas, Patricia

2017-07-01

We use the error bounds for adiabatic invariants found in the work of Chartier, Murua and Sanz-Serna [3] to bound the solutions of a Hamiltonian system near an equilibrium over exponentially long times. Our estimates depend only on the linearized system and not on the higher order terms as in KAM theory, nor do we require any steepness or convexity conditions as in Nekhoroshev theory. We require that the equilibrium point where our estimate applies satisfy a type of formal stability called Lie stability.

Space experiments with high stability clocks

International Nuclear Information System (INIS)

Vessot, R.F.C.

1993-01-01

Modern metrology depends increasingly on the accuracy and frequency stability of atomic clocks. Applications of such high-stability oscillators (or clocks) to experiments performed in space are described and estimates of the precision of these experiments are made in terms of clock performance. Methods using time-correlation to cancel localized disturbances in very long signal paths and a proposed space borne four station VLBI system are described. (TEC). 30 refs., 14 figs., 1 tab

Long-term monitoring of stream bank stability under different vegetation cover

Science.gov (United States)

Krzeminska, Dominika; Skaalsveen, Kamilla; Kerkhof, Tjibbe

2017-04-01

Vegetated buffer zones are common environmental measures in many countries, including Norway. The presence of riparian vegetation on stream banks not only provides ecological benefits but also influence bank slope stability, through several complex interactions between riparian vegetation and hydro - mechanical processes. The hydrological processes associated with slope stability are complex and yet difficult to quantify, especially because their transient effects (e.g. changes throughout the vegetation life cycle). Additionally, there is very limited amount of field scale research focusing on investigation of coupled hydrological and mechanical influence of vegetation on stream bank behavior, accounting for both seasonal time scale and different vegetation type, and none dedicated to marine clay soils (typically soil for Norway). In order to fill this gap we established continues, long term hydrogeological monitoring o selected cross - section within stream bank, covered with different types of vegetation, typical for Norwegian agriculture areas (grass, shrubs, and trees). The monitoring involves methods such as spatial and temporal monitoring of soil moisture conditions, ground water level and fluctuation of water level in the stream. Herein we will present first 10 months of monitoring data: observed hydrological trends and differences between three cross - sections. Moreover, we will present first modelling exercises that aims to estimate stream banks stability with accounting on presence of different vegetation types using BSTEM and HYDRUS models. With this presentation, we would like to stimulate the discussion and get feedback that could help us to improve both, our experimental set up and analysis approach.

Research on geosphere stability for long-term isolation of radioactive waste. Scientific programme for fiscal years 2015-2021

International Nuclear Information System (INIS)

Umeda, Koji; Yasue, Ken-ichi; Saito-Kokubu, Yoko; Niwa, Masakazu; Asamori, Koichi; Fujita, Natsuko; Shimizu, Mayuko; Shimada, Akiomi; Matsubara, Akihiro; Tamura, Hajimu; Yokoyama, Tatsunori; Watanabe, Takahiro; Tokuyasu, Kayoko; Hama, Yuki

2015-08-01

The study on long-term geological stability has three objectives, namely, (1) development of technologies for determining the past and present conditions of the geological environment, (2) development of technologies for long-term prediction and evaluation of impacts and (3) development of dating techniques using advanced equipment on isotope geology and geochronology, in order to make contribution to site investigation and safety assessment for the geological disposal of high-level radioactive waste (HLW). This report is to outline 7 years plan (fiscal years 2015-2021) of research and development (R and D) for geosphere stability for long-term isolation of the HLW in Japan Atomic Energy Agency. Background of this research is clarified with the necessity and the significance for site investigation and safety assessment, and the past progress in this report. The objectives, outline, contents and schedule during the next 7 years are described in detail. In addition, the plan framework is structured into the following categories: (1) Development and Systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. (author)

Transient Stability Assessment of Power System with Large Amount of Wind Power Penetration

DEFF Research Database (Denmark)

Liu, Leo; Chen, Zhe; Bak, Claus Leth

2012-01-01

Recently, the security and stability of power system with large amount of wind power are the concerned issues, especially the transient stability. In Denmark, the onshore and offshore wind farms are connected to distribution system and transmission system respectively. The control and protection...... methodologies of onshore and offshore wind farms definitely affect the transient stability of power system. In this paper, the onshore and offshore wind farms are modeled in detail in order to assess the transient stability of western Danish power system. Further, the computation of critical clearing time (CCT...... plants, load consumption level and high voltage direct current (HVDC) transmission links are taken into account. The results presented in this paper are able to provide an early awareness of power system security condition of the western Danish power system....

Stability Analysis for Fractional-Order Linear Singular Delay Differential Systems

Directory of Open Access Journals (Sweden)

Hai Zhang

2014-01-01

Full Text Available We investigate the delay-independently asymptotic stability of fractional-order linear singular delay differential systems. Based on the algebraic approach, the sufficient conditions are presented to ensure the asymptotic stability for any delay parameter. By applying the stability criteria, one can avoid solving the roots of transcendental equations. An example is also provided to illustrate the effectiveness and applicability of the theoretical results.

Stability of Switched Feedback Time-Varying Dynamic Systems Based on the Properties of the Gap Metric for Operators

Directory of Open Access Journals (Sweden)

M. De la Sen

2012-01-01

Full Text Available The stabilization of dynamic switched control systems is focused on and based on an operator-based formulation. It is assumed that the controlled object and the controller are described by sequences of closed operator pairs (L,C on a Hilbert space H of the input and output spaces and it is related to the existence of the inverse of the resulting input-output operator being admissible and bounded. The technical mechanism addressed to get the results is the appropriate use of the fact that closed operators being sufficiently close to bounded operators, in terms of the gap metric, are also bounded. That philosophy is followed for the operators describing the input-output relations in switched feedback control systems so as to guarantee the closed-loop stabilization.

Analysis of the gyroscopic stabilization of a system of rigid bodies

DEFF Research Database (Denmark)

Kliem, Wolfhard; Seyranian, Alexander P.

1997-01-01

We study the gyroscopic stability of a three-body system. A new method of finding stability regions, based on mechanism and criteria for gyroscopic stabilization, is presented. Of particular interest in this connection is the theory of interaction of eigenvalues. This leads to a complete 3......-dimensional analysis, which shows the regions of stability, divergence, and flutter of a simple model of a rotating spaceship....

Stability and predictability in younger crystalline rock system: Japanese Islands case

International Nuclear Information System (INIS)

Yoshida, S.

2009-01-01

The Japanese Islands consist of igneous, sedimentary, and metamorphic rocks ranging in age from Paleozoic to Cenozoic. Among these, Carboniferous to Paleogene rocks occupy about 60% of the total area of the Japanese Islands. It should be noted that Quaternary volcanic rocks occupy only about 9% of the total area, although Quaternary volcanoes occur throughout the Japanese Islands. Long-term stability and predictability in the rock system are discussed in terms of volcanic activity, active faulting, and plate motion. Volcanic activity in the Japanese Islands is intimately related to subduction of the Pacific Plate and the Philippine Sea Plate. The volcanic front related to the Pacific and the Philippine Sea plates has been essentially fixed since about 6 Ma. The main active faults, which are distributed sporadically throughout the Japanese Islands, number about 150 and have been extensively investigated. The modes of the Pacific Plate and the Philippine Sea Plate have been essentially invariable since 10 Ma and 6 Ma, respectively. These lines of evidence imply that volcanism and tectonism in the Japanese Islands will scarcely change for hundreds of thousands of years into the future. It is clear that many places suitable for geological disposal will be present in this rock system. (author)

Combined analytical and numerical approaches in Dynamic Stability analyses of engineering systems

Science.gov (United States)

Náprstek, Jiří

2015-03-01

Dynamic Stability is a widely studied area that has attracted many researchers from various disciplines. Although Dynamic Stability is usually associated with mechanics, theoretical physics or other natural and technical disciplines, it is also relevant to social, economic, and philosophical areas of our lives. Therefore, it is useful to occasionally highlight the general aspects of this amazing area, to present some relevant examples and to evaluate its position among the various branches of Rational Mechanics. From this perspective, the aim of this study is to present a brief review concerning the Dynamic Stability problem, its basic definitions and principles, important phenomena, research motivations and applications in engineering. The relationships with relevant systems that are prone to stability loss (encountered in other areas such as physics, other natural sciences and engineering) are also noted. The theoretical background, which is applicable to many disciplines, is presented. In this paper, the most frequently used Dynamic Stability analysis methods are presented in relation to individual dynamic systems that are widely discussed in various engineering branches. In particular, the Lyapunov function and exponent procedures, Routh-Hurwitz, Liénard, and other theorems are outlined together with demonstrations. The possibilities for analytical and numerical procedures are mentioned together with possible feedback from experimental research and testing. The strengths and shortcomings of these approaches are evaluated together with examples of their effective complementing of each other. The systems that are widely encountered in engineering are presented in the form of mathematical models. The analyses of their Dynamic Stability and post-critical behaviour are also presented. The stability limits, bifurcation points, quasi-periodic response processes and chaotic regimes are discussed. The limit cycle existence and stability are examined together with their

Long term carrier envelope phase stabilization of a grating based high power femtosecond laser using the direct locking method

International Nuclear Information System (INIS)

Lee, Jae Hwan; Lee, Youg Soo; Park, Juyun; Nam, Chang Hee; Yu, Tae Jun

2008-01-01

The carrier envelope phase (CEP)stabilization of femtosecond laser pulses has been intensively investigated for ultrafast science as well as for frequency metrology. In the case of few cycle pulses stabilization and control of the CEP is an important issue, since the electric field profile changes with CEP variation. We have developed the direct locking method to stabilize the CEP for the investigation of attosecond physics. The direct locking method uses the beating signal itself, measured using an f to 2f interferometer, as an error signal to a feedback loop. The direct locking method quenches the beating signal so that the CEP variation between successive pulses become zero and every pulses from the oscillator ts identical. Due to the direct use of the beating signal, the signal processing is simple and complex equipment, used in the case of the phase locked loop (PLL)method operating in the frequency domain, are not required. For long term stability, we have proposed and implemented a double feedback technique, and achieved CEP stabilization of the oscillator for 24 hours, as shown in Fig. 1. This long term CEP stabilization was achieved without realignment of any optical components. The CEP stabilization for a whole day is a clear demonstration of the robustness of the direct locking method. The amplification of CEP stabilized laser pulses induces additional CEP variation. Even though the CEP of an oscillator is stabilized, the CEP drift is generated again during amplification due to external perturbations, such as pumping power fluctuation and beam pointing fluctuation. To measure the CEP drift of the amplified pulses, a spectral interferometer (SI)was employed. The CEP drift obtained from SI was used as the error signal of another feedback loop installed in the amplifier chain. To compensate for the large CEP drift induced during amplification, the grating separation of the pulse compressor was adjusted. Figure 2 shows the result of CEP stabilization of

Optimal Parameter Selection of Power System Stabilizer using Genetic Algorithm

Energy Technology Data Exchange (ETDEWEB)

Chung, Hyeng Hwan; Chung, Dong Il; Chung, Mun Kyu [Dong-AUniversity (Korea); Wang, Yong Peel [Canterbury Univeristy (New Zealand)

1999-06-01

In this paper, it is suggested that the selection method of optimal parameter of power system stabilizer (PSS) with robustness in low frequency oscillation for power system using real variable elitism genetic algorithm (RVEGA). The optimal parameters were selected in the case of power system stabilizer with one lead compensator, and two lead compensator. Also, the frequency responses characteristics of PSS, the system eigenvalues criterion and the dynamic characteristics were considered in the normal load and the heavy load, which proved usefulness of RVEGA compare with Yu's compensator design theory. (author). 20 refs., 15 figs., 8 tabs.

Advances in power system modelling, control and stability analysis

CERN Document Server

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.

Stability analysis of switched linear systems defined by graphs

NARCIS (Netherlands)

Athanasopoulos, N.; Lazar, M.

2014-01-01

We present necessary and sufficient conditions for global exponential stability for switched discrete-time linear systems, under arbitrary switching, which is constrained within a set of admissible transitions. The class of systems studied includes the family of systems under arbitrary switching,

Stabilization of discrete-time LTI positive systems

Directory of Open Access Journals (Sweden)

Krokavec Dušan

2017-12-01

Full Text Available The paper mitigates the existing conditions reported in the previous literature for control design of discrete-time linear positive systems. Incorporating an associated structure of linear matrix inequalities, combined with the Lyapunov inequality guaranteing asymptotic stability of discrete-time positive system structures, new conditions are presented with which the state-feedback controllers and the system state observers can be designed. Associated solutions of the proposed design conditions are illustrated by numerical illustrative examples.

[Study on mechanism of SOM stabilization of paddy soils under long-term fertilizations].

Science.gov (United States)

Luo, Lu; Zhou, Ping; Tong, Cheng-Li; Shi, Hui; Wu, Jin-Shui; Huang, Tie-Ping

2013-02-01

Fourier transform infrared spectroscopy (FTIR) was applied to study the structure of soil organic matter (SOM) of paddy soils under long-term different fertilization treatments. The aim was to clarify the different distribution of SOM between different fertilization methods and between topsoil and subsoil, and to explore the stability mechanism of SOM under different fertilization treatments. The results showed that the content of topsoil organic carbon (SOC) was the highest under organic-inorganic fertilizations, with the increment of SOC by 18.5%, 12.9% and 18.4% under high organic manure (HOM), low organic manure (LOM) and straw returning (STW) respectively compared with no fertilization treatment (CK). The long-term fertilizations also changed the chemical structure of SOM. As compared with CK, different fertilization treatments increased the functional group absorbing intensity of chemical resistance compounds (aliphatic, aromaticity), carbohydrate and organo-silicon compounds, which was the most distinctive under treatments of HOM, LOM and STW. For example, the absorbing intensity of alkyl was 0.30, 0.25 and 0.29 under HOM, LOM and STW, respectively. These values were increased by 87% , 56% and 81% as compared with that under CK treatment. The functional group absorbing intensity of SOM in the topsoil was stronger than that in the subsoil, with the most distinctive difference under HOM, LOM and STW treatments. The present research indicated that the enhanced chemical resistance of functional group of SOM may contribute to the high contents of SOC in the paddy soils under long-term organic-inorganic fertilizations, which also suggested a chemical stabilization mechanism of SOM in the paddy soils.

New Results of Global Exponential Stabilization for BLDCMs System

OpenAIRE

Fengxia Tian; Fangchao Zhen; Guopeng Zhou; Xiaoxin Liao

2015-01-01

The global exponential stabilization for brushless direct current motor (BLDCM) system is studied. Four linear and simple feedback controllers are proposed to realize the global stabilization of BLDCM with exponential convergence rate; the control law used in each theorem is less conservative and more concise. Finally, an example is given to demonstrate the correctness of the proposed results.

Evaluation of Laser Stabilization and Imaging Systems for LCLS-II - Final Paper

Energy Technology Data Exchange (ETDEWEB)

Barry, Matthew [Auburn Univ., AL (United States)

2015-08-20

By combining the top performing commercial laser beam stabilization system with the most ideal optical imaging configuration, the beamline for the Linear Accelerator Coherent Light Source II (LCLS-II) will deliver the highest quality and most stable beam to the cathode. To determine the optimal combination, LCLS-II beamline conditions were replicated and the systems tested with a He-Ne laser. The Guidestar-II and MRC active laser beam stabilization systems were evaluated for their ideal positioning and stability. Both a two and four lens optical imaging configuration was then evaluated for beam imaging quality, magnification properties, and natural stability. In their best performances when tested over fifteen hours, Guidestar-II kept the beam stable over approximately 70-110um while the MRC system kept it stable over approximately 90-100um. During short periods of time, Guidestar-II kept the beam stable between 10-20um, but was more susceptible to drift over time, while the MRC system maintained the beam between 30-50um with less overall drift. The best optical imaging configuration proved to be a four lens system that images to the iris located in the cathode room and from there, imaged to the cathode. The magnification from the iris to the cathode was 2:1, within an acceptable tolerance to the expected 2.1:1 magnification. The two lens configuration was slightly more stable in small periods of time (less than 10 minutes) without the assistance of a stability system, approximately 55um compared to approximately 70um, but the four lens configurations beam image had a significantly flatter intensity distribution compared to the two lens configuration which had a Gaussian distribution. A final test still needs to be run with both stability systems running at the same time through the four lens system. With this data, the optimal laser beam stabilization system can be determined for the beamline of LCLS-II.

Fully Implantable Deep Brain Stimulation System with Wireless Power Transmission for Long-term Use in Rodent Models of Parkinson's Disease.

Science.gov (United States)

Heo, Man Seung; Moon, Hyun Seok; Kim, Hee Chan; Park, Hyung Woo; Lim, Young Hoon; Paek, Sun Ha

2015-03-01

The purpose of this study to develop new deep-brain stimulation system for long-term use in animals, in order to develop a variety of neural prostheses. Our system has two distinguished features, which are the fully implanted system having wearable wireless power transfer and ability to change the parameter of stimulus parameter. It is useful for obtaining a variety of data from a long-term experiment. To validate our system, we performed pre-clinical test in Parkinson's disease-rat models for 4 weeks. Through the in vivo test, we observed the possibility of not only long-term implantation and stability, but also free movement of animals. We confirmed that the electrical stimulation neither caused any side effect nor damaged the electrodes. We proved possibility of our system to conduct the long-term pre-clinical test in variety of parameter, which is available for development of neural prostheses.

Evaluation of postural stability of people with Parkinson's disease with Biodex Balance System device

Directory of Open Access Journals (Sweden)

Jacek Wilczyński

2016-10-01

Summary Parkinson's disease is an incurable disease of the CNS of progressive and chronic course. Postural Stability of people with Parkinson's is hindered what predisposes to falls. In a person standing seemingly motionless body performs small oscillatory movements caused by differences in antigravity muscle tension. This mechanism is called postural rocking and mobility associated with it is referred to as postural sway. The parameters of rocking are very sensitive indicator of balance control, and can be used to evaluate and detect pathological changes. The aim of the study was to evaluate the stability of posture of people with Parkinson's disease on the basis of posturographic examination.The age range of the patients was from 52 to 85 years (mean 71.8 years. In terms of age the patients were divided into two groups. The first group consisted of 9 people to 75 years old, while the other of 8 people over 75 years old. The postural stability was assessed with Biodex Balance System. The study was performed at the Laboratory of Posturology at the Institute of Physiotherapy at UJK in Kielce. Although Mann-Whitney U test showed no significant differences in postural stability between the sexes, its lower values are reported for men. A standing position of the subjects was characterized by greater deviation in the sagittal plane than in the frontal plane (A/P>M/L with a tendency to tilt backwards. There were better postural stability results in the younger group (group 1, up to 75 years old. The subjects in this group obtained significantly lower values of postural stability (t°=2.2744, pM/L z tendencją do odchylania się do tyłu. Zaobserwowano lepsze wyniki stabilności posturalnej w grupie osób młodszych (grupa 1 do 75 roku życia. Badani tej grupy uzyskali istotnie niższe wartości stabilności posturalnej (t°= 2,2744, p<0,05.   Słowa kluczowe: stabilność posturalna, choroba Parkinsona, platforma Biodex Balance System

Application of matrix singular value properties for evaluating gain and phase margins of multiloop systems. [stability margins for wing flutter suppression and drone lateral attitude control

Science.gov (United States)

Mukhopadhyay, V.; Newsom, J. R.

1982-01-01

A stability margin evaluation method in terms of simultaneous gain and phase changes in all loops of a multiloop system is presented. A universal gain-phase margin evaluation diagram is constructed by generalizing an existing method using matrix singular value properties. Using this diagram and computing the minimum singular value of the system return difference matrix over the operating frequency range, regions of guaranteed stability margins can be obtained. Singular values are computed for a wing flutter suppression and a drone lateral attitude control problem. The numerical results indicate that this method predicts quite conservative stability margins. In the second example if the eigenvalue magnitude is used instead of the singular value, as a measure of nearness to singularity, more realistic stability margins are obtained. However, this relaxed measure generally cannot guarantee global stability.

A Study of Strong Stability of Distributed Systems. Ph.D. Thesis

Science.gov (United States)

Cataltepe, Tayfun

1989-01-01

The strong stability of distributed systems is studied and the problem of characterizing strongly stable semigroups of operators associated with distributed systems is addressed. Main emphasis is on contractive systems. Three different approaches to characterization of strongly stable contractive semigroups are developed. The first one is an operator theoretical approach. Using the theory of dilations, it is shown that every strongly stable contractive semigroup is related to the left shift semigroup on an L(exp 2) space. Then, a decomposition for the state space which identifies strongly stable and unstable states is introduced. Based on this decomposition, conditions for a contractive semigroup to be strongly stable are obtained. Finally, extensions of Lyapunov's equation for distributed parameter systems are investigated. Sufficient conditions for weak and strong stabilities of uniformly bounded semigroups are obtained by relaxing the equivalent norm condition on the right hand side of the Lyanupov equation. These characterizations are then applied to the problem of feedback stabilization. First, it is shown via the state space decomposition that under certain conditions a contractive system (A,B) can be strongly stabilized by the feedback -B(*). Then, application of the extensions of the Lyapunov equation results in sufficient conditions for weak, strong, and exponential stabilizations of contractive systems by the feedback -B(*). Finally, it is shown that for a contractive system, the first derivative of x with respect to time = Ax + Bu (where B is any linear bounded operator), there is a related linear quadratic regulator problem and a corresponding steady state Riccati equation which always has a bounded nonnegative solution.

The armenian power system operation stability investigation accounting putting new power systems into operation

International Nuclear Information System (INIS)

Yeghiazaryan, L.V.; Hakobyan, S.G.; Gharibyan, G.V.; Harutyunyan, G.S.; Galstyan, G.H.

2010-01-01

The description of the power systems operation stability failure caused by the system significant emergency states occurred during the last working period in Armenian and USA power systems is performed. With the use of PSSTME-31 software portfolio of Siemens Firm a design model is developed and transient electromechanical process calculations for Armenian power system are performed. The accuracy of the model is checked by comparing real-time transient state parameters and their reproduction calculation results.The Armenia - Iran current power transmission lines permissible limit under the condition of the static and dynamic stability requirements and in case of the new thermal power units maintenance are defined

Experimental study of flame stability in biogas premix system

International Nuclear Information System (INIS)

Diaz G, Carlos A; Amell A Andres; Cardona Luis F

2008-01-01

Utilization of new renewable energy sources have had a special interest in last years looking for decrease the dependence of fossil fuels and the environmental impact generated for them. This work studies experimentally the flame stability of a simulated biogas with a volumetric composition of 60% methane and 40% carbon dioxide. The objective of this study is to obtain information about design and interchangeability of gases in premixed combustion systems that operate with different fuel gases. The critical velocity gradient was the stability criteria used. Utilization of this criteria and the experimental method followed, using a partial premixed burner, stability flame diagram of biogas studied had been obtained. Presence of carbon dioxide has a negative effect in flame stability, decreasing significantly the laminar flame speed and consequently, the stability range of biogas burners because of apparition of blow off.

Mobile Phenotyping System Using an Aeromotively Stabilized Cable-Driven Robot

Science.gov (United States)

Newman, M. B.; Zygielbaum, A. I.

2017-12-01

Agricultural researchers are constantly attempting to generate superior agricultural crops. Whether this means creating crops with greater yield, crops that are more resilient to disease, or crops that can tolerate harsh environments with fewer failures, test plots of these experimental crops must be studied in real-world environments with minimal invasion to determine how they will perform in full-scale agricultural settings. To monitor these crops without interfering with their natural growth, a noninvasive sensor system has been implemented. This system, instituted by the College of Agricultural Sciences and Natural Resources at the University of Nebraska - Lincoln (UNL), uses a system of poles, cables, and winches to support and maneuver a sensor platform above the crops at an outdoor phenotyping site. In this work, we improve upon the UNL outdoor phenotyping system presenting the concept design for a mobile, cable-driven phenotyping system as opposed to a permanent phenotyping facility. One major challenge in large-scale, cable-driven robots is stability of the end-effector. As a result, this mobile system seeks to use a novel method of end-effector stabilization using an onboard rotor drive system, herein referred to as the Instrument Platform Aeromotive Stabilization System (IPASS). A prototype system is developed and analyzed to determine the viability of IPASS.

Midterm Stability Evaluation of Wide-area Power System by using Synchronized Phasor Measurements

Science.gov (United States)

Ota, Yutaka; Ukai, Hiroyuki; Nakamura, Koichi; Fujita, Hideki

In recent years, the PMU (Phasor Measurement Unit) receives a great deal of attention as a synchronized measurement system of power systems. Synchronized phasor angles obtained by the PMU provide the effective information for evaluating the stability of a bulk power system. The aspect of instability phenomena during midterm tends to be more complicated, and the stability analysis using the synchronized phasor measurements is significant in order to keep a complicated power system stable. This paper proposes a midterm stability evaluation method of the wide-area power system by using the synchronized phasor measurements. By clustering and aggregating the power system to some coherent groups, the step-out is effectively predicted on the basis of the two-machine equivalent power system model. The midterm stability of a longitudinal power system model of Japanese 60Hz systems constructed by the PSA, which is a hybrid-type power system simulator, is practically evaluated using the proposed method.

New Delay-Dependent Robust Exponential Stability Criteria of LPD Neutral Systems with Mixed Time-Varying Delays and Nonlinear Perturbations

Directory of Open Access Journals (Sweden)

Sirada Pinjai

2013-01-01

Full Text Available This paper is concerned with the problem of robust exponential stability for linear parameter-dependent (LPD neutral systems with mixed time-varying delays and nonlinear perturbations. Based on a new parameter-dependent Lyapunov-Krasovskii functional, Leibniz-Newton formula, decomposition technique of coefficient matrix, free-weighting matrices, Cauchy’s inequality, modified version of Jensen’s inequality, model transformation, and linear matrix inequality technique, new delay-dependent robust exponential stability criteria are established in terms of linear matrix inequalities (LMIs. Numerical examples are given to show the effectiveness and less conservativeness of the proposed methods.

Fixed-Time Stability of the Hydraulic Turbine Governing System

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Caoyuan Ma

2018-01-01

Full Text Available This paper studies the problem of fixed-time stability of hydraulic turbine governing system with the elastic water hammer nonlinear model. To control and improve the quality of hydraulic turbine governing system, a new fixed-time control strategy is proposed, which can stabilize the water turbine governing system within a fixed time. Compared with the finite-time control strategy where the convergence rate depends on the initial state, the settling time of the fixed-time control scheme can be adjusted to the required value regardless of the initial conditions. Finally, we numerically show that the fixed-time control is more effective than and superior to the finite-time control.

Long-term manure amendments reduced soil aggregate stability via redistribution of the glomalin-related soil protein in macroaggregates

Science.gov (United States)

Xie, Hongtu; Li, Jianwei; Zhang, Bin; Wang, Lianfeng; Wang, Jingkuan; He, Hongbo; Zhang, Xudong

2015-01-01

Glomalin-related soil protein (GRSP) contributes to the formation and maintenance of soil aggregates, it is however remains unclear whether long-term intensive manure amendments alter soil aggregates stability and whether GRSP regulates these changes. Based on a three-decade long fertilization experiment in northeast China, this study examined the impact of long-term manure input on soil organic carbon (SOC), total and easily extractable GRSP (GRSPt and GRSPe) and their respective allocations in four soil aggregates (>2000 μm; 2000–250 μm; 250–53 μm; and soil and SOC in each aggregate generally increased with increasing manure input, GRSPt and GRSPe in each aggregate showed varying changes with manure input. Both GRSP in macroaggregates (2000–250 μm) were significantly higher under low manure input, a pattern consistent with changes in soil aggregate stability. Constituting 38~49% of soil mass, macroaggregates likely contributed to the nonlinear changes of aggregate stability under manure amendments. The regulatory process of GRSP allocations in soil aggregates has important implications for manure management under intensive agriculture. PMID:26423355

Stochastic stability of four-wheel-steering system

International Nuclear Information System (INIS)

Huang Dongwei; Wang Hongli; Zhu Zhiwen; Feng Zhang

2007-01-01

A four-wheel-steering system subjected to white noise excitations was reduced to a two-degree-of-freedom quasi-non-integrable-Hamiltonian system. Subsequently we obtained an one-dimensional Ito stochastic differential equation for the averaged Hamiltonian of the system by using the stochastic averaging method for quasi-non-integrable-Hamiltonian systems. Thus, the stochastic stability of four-wheel-steering system was analyzed by analyzing the sample behaviors of the averaged Hamiltonian at the boundary H = 0 and calculating its Lyapunov exponent. An example given at the end demonstrated that the conclusion obtained is of considerable significance

Integral φ0-Stability in terms of Two Measures for Impulsive Differential Equations with “Supremum”

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Peiguang Wang

2014-01-01

Full Text Available This paper establishes a criterion on integral φ0-stability in terms of two measures for impulsive differential equations with “supremum” by using the cone-valued piecewise continuous Lyapunov functions, Razumikhin method, and comparative method. Meantime, an example is given to illustrate our result.

An equilibrium point stabilization strategy for the Chen system

International Nuclear Information System (INIS)

Alvarez-Ramirez, Jose; Cevantes, Ilse; Femat, Ricardo

2004-01-01

The aim of this Letter is to address the equilibrium point stabilization problem of the Chen system by employing a simple linear feedback controller derived from time-scaling the dynamics of a single variable. The controller has the advantage of being easy to implement and a rigorous stability proof is provided based on singular perturbation arguments. Results are illustrated via numerical simulations

Stabilizing periodic orbits of chaotic systems using fuzzy adaptive sliding mode control