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Sample records for dynamic stabilization device

  1. Investigation of biomechanical behavior of lumbar vertebral segments with dynamic stabilization device using finite element approach

    Science.gov (United States)

    Deoghare, Ashish B.; Kashyap, Siddharth; Padole, Pramod M.

    2013-03-01

    Degenerative disc disease is a major source of lower back pain and significantly alters the biomechanics of the lumbar spine. Dynamic stabilization device is a remedial technique which uses flexible materials to stabilize the affected lumbar region while preserving the natural anatomy of the spine. The main objective of this research work is to investigate the stiffness variation of dynamic stabilization device under various loading conditions under compression, axial rotation and flexion. Three dimensional model of the two segment lumbar spine is developed using computed tomography (CT) scan images. The lumbar structure developed is analyzed in ANSYS workbench. Two types of dynamic stabilization are considered: one with stabilizing device as pedicle instrumentation and second with stabilization device inserted around the inter-vertebral disc. Analysis suggests that proper positioning of the dynamic stabilization device is of paramount significance prior to the surgery. Inserting the device in the posterior region indicates the adverse effects as it shows increase in the deformation of the inter-vertebral disc. Analysis executed by positioning stabilizing device around the inter-vertebral disc yields better result for various stiffness values under compression and other loadings. [Figure not available: see fulltext.

  2. Dynamic stabilization devices in the treatment of low back pain

    Directory of Open Access Journals (Sweden)

    Sengupta D

    2005-01-01

    Full Text Available Soft stabilization has an important role in the treatment of the degenerative lumbar spine. Fusion of one or two motion segments may not make a big difference in the total range of motion of the lumbar spine, but preserving flexibility of a motion segment may prevent adjacent segment disease and may permit disc replacement, even when facet joints need to be excised. A favourable environment is created in the motion segment by unloading the disc and permitting near normal motion, the disc may be able to repair itself or may supplement reparative potential of gene therapy.

  3. [The optimal insertion position of the lumbar interspinous dynamic stabilization device (Coflex): a biomechanical evaluation].

    Science.gov (United States)

    Zu, Dan; Hai, Yong; Lu, Shibao; Yang, Jincai; Liu, Yuzeng; Liu, Tie; Meng, Xianglong; Zhou, Lijin; Pang, Chuan

    2014-03-01

    To evaluate the optimal insertion position of the Coflex lumbar interspinous dynamic stabilization device. Six fresh adult human cadaveric lumbar spine specimens (L1-L5) were mounted in a materials testing machine by embedding to clamps with L1 and L5 vertebrae. L3-4 motion segment of each specimen was operated by selective decompression and Coflex interspinous device insertion. The L3 and L4 vertebrae was inserted one needle attached with four marker points respectively, which were used to record the range of motion (ROM). Each lumbar spine specimen was tested according to the loading sequence at 5 groups: intact (keeping lumbar ligamenta and facet joints intact) group, partial destabilized (resection of L3-4 interspinous ligamenta, ligamentum flavum, facet capsule, and bilateral resection 50% of L3 inferior facets) group, 10 mm insertion (distance between apex of U-shaped Coflex and dural sac was 10 mm)group, 5 mm insertion (distance was 5 mm)group, and 0 mm insertion (distance was 0 mm)group. Each lumbar spine specimen was tested repeatedly 3 times according to a loading sequence consisting of flexion, extension, left/right lateral bending, left/right axial rotation, loaded with pure moments of 8 N·m, and was recorded the ROM of operative segment at the third time. ROM of 5 groups in 6 directions respectively were analyzed with one-way ANOVA test and multiple comparisons were based on LSD method. The means ROM of 5 groups were not all equal in flexion, extension, left/right lateral bending, left/right axial rotation (F = 8.472, 18.301, 7.700, 12.473, 16.809, 6.624; all P 0.05). The ROM of the 5 mm and 0 mm insertion group were no significant differences comparing with the intact group in flexion, extension, left/right axial rotation (P > 0.05), but it were significant differences comparing with the partial destabilized group in the same directions (5 mm insertion group: t = 3.19, 6.34, 5.26, 3.43, all P bending between the 5mm/0mm insertion groups and the

  4. Clinical evaluation of a lumbar interspinous dynamic stabilization device (the Wallis system) with a 13-year mean follow-up.

    Science.gov (United States)

    Sénégas, Jacques; Vital, Jean-Marc; Pointillart, Vincent; Mangione, Paolo

    2009-07-01

    The authors determined current health status of patients who had been included in a long-term survivorship analysis of a lumbar dynamic stabilizer. Among 133 living patients, 107 (average age at surgery, 44.2 +/- 9.9 years) completed health questionnaires. All patients had initially been scheduled for decompression and fusion for canal stenosis, herniated disc, or both. In 20 patients, the implant was removed, and fusion was performed. The other 87 still had the dynamic stabilizer. Satisfaction, Oswestry disability index, visual analog scales for back and leg pain, short-form (SF-36) quality-of-life physical composite score, physical function, and social function were significantly better (p stabilization device. SF-36 scores of the fused subgroup were no worse than those reported elsewhere in patients who had primary pedicle-screw enhanced lumbar fusion. This anatomy-sparing device provided a good 13-year clinical outcome and obviated arthrodesis in 80% of patients.

  5. Analysis on Supporting Stability for Track Subgrade Dynamic Response In-situ Test Device Based on NSGA-II

    Directory of Open Access Journals (Sweden)

    Feilong Zheng

    2013-07-01

    Full Text Available The dynamic response test to the subgrade plays a very important role in railway construction and a new in-situ test system is proposed. This paper presents the application of non-dominated sorting genetic algorithm-II (NSGA-II to analyze the stability of the supporting equipment for track subgrade dynamic response in-situ test device. Its stability is related with the extension length of the hydraulic cylinders and the backward condition of the supporting equipment - the hydraulic excavator. The problem is formulated as a multi-objective optimization problem with the objective of maximizing  the supporting force for the test device. An 85 tons excavator is picked as the case to study. The first optimal results show the excavator may not support the test system successfully. After redesigning the boom and adding its weight and length as new parameters, the second optimize results indicate the test device can work normally.

  6. Dynamics of Fluctuations, Flows and Global Stability Under Electrode Biasing in a Linear Plasma Device

    Science.gov (United States)

    Desjardins, Tiffany

    2015-11-01

    Various bias electrodes have been inserted into the Helicon-Cathode (HelCat) device at the University of New Mexico, in order to affect intrinsic drift-wave turbulence and flows. The goal of the experiments was to suppress and effect the intrinsic turbulence and with detailed measurements, understand the changes that occur during biasing. The drift-mode in HelCat varies from coherent at low magnetic field (1kG). The first electrode consists of 6 concentric rings set in a ceramic substrate; these rings act as a boundary condition, sitting at the end of the plasma column 2-m away from the source. A negative bias has been found to have no effect on the fluctuations, but a positive bias (Vr>5Te) is required in order to suppress the drift-mode. Two molybdenum grids can also be inserted into the plasma and sit close to the source. Floating or grounding a grid results in suppressing the drift-mode of the system. A negative bias (>-5Te) is found to return the drift-mode, and it is possible to drive a once coherent mode into a broad-band turbulent one. From a bias voltage of -5Tenew mode, which is identified as a parallel-driven Kelvin-Helmholtz mode. At high positive bias, Vg>10Te, a new large-scale global mode is excited. This mode exhibits fluctuations in the ion saturation current, as well as in the potential, with a magnitude >50%. This mode has been identified as the potential relaxation instability (PRI). In order to better understand the modes and changes observed in the plasma, a linear stability code, LSS, was employed. As well, a 1D3V-PIC code utilizing Braginskii's equations was also utilized to understand the high-bias instability.

  7. Does the personal lift-assist device affect the local dynamic stability of the spine during lifting?

    Science.gov (United States)

    Graham, Ryan B; Sadler, Erin M; Stevenson, Joan M

    2011-02-03

    The personal lift-assist device (PLAD) is an on-body ergonomic aid that reduces low back physical demands through the restorative moment of an external spring element, which possesses a mechanical advantage over the erector spinae. Although the PLAD has proven effective at reducing low back muscular demand, spinal moments, and localized muscular fatigue during laboratory and industrial tasks, the effects of the device on the neuromuscular control of spinal stability during lifting have yet to be assessed. Thirty healthy subjects (15M, 15F) performed repetitive lifting for three minutes, at a rate of 10 lifts per minute, with and without the PLAD. Maximum finite-time Lyapunov exponents, representing short-term (λ(max-s)) and long-term (λ(max-l)) divergence were calculated from the measured trunk kinematics to estimate the local dynamic stability of the lumbar spine. Using a mixed-design repeated-measures ANOVA, it was determined that wearing the PLAD did not significantly change λ(max-s) (μ(NP)=0.335, μ(P)=0.321, p=0.225), but did significantly reduce λ(max-l) (μ(NP)=0.0024, μ(P)=-0.0011, p=0.014, η(2)=0.197). There were no between-subject effects of sex, or significant interactions (p>0.720). The present results indicated that λ(max-s) was not statistically different between the device conditions, but that the PLAD significantly reduced λ(max-l) to a negative (stable) value. This shows that subjects' neuromuscular systems were able to respond to local perturbations more effectively when wearing the device, reflecting a more stable control of spinal movements. These findings are important when recommending the PLAD for long-term industrial or clinical use. Copyright © 2010 Elsevier Ltd. All rights reserved.

  8. STATIC AND DYNAMIC LOCATION OF VARIABLE IMPEDANCE DEVICES FOR STABILITY STUDIES

    Directory of Open Access Journals (Sweden)

    N. Magaji

    2013-01-01

    Full Text Available This study used the concept of model controllability and observability in product form called residue factor to find the best location of Thyristor-Controlled based series and shunt devices called variable impedance devices. The success of this controller depends on its best possible location in busbar or line of power system network. The method is based on the relationship between the parameters of variable impedance devices to the vital modes. Linearization of non linear model of Power system and the thyristors based FACTS devices provide mens of computing residue factor and singular value factor. The location of variable impedance or thyristors based controllers have been calculated for the base case only. The usefulness of the these methods of placement considered 16 machines, 68 bus systems.

  9. Static and Dynamic Stability Analysis of Distributed Energy Resources Components with Storage Devices and Loads for Smart Grids

    DEFF Research Database (Denmark)

    Mihet-Popa, Lucian; Groza, V.

    2011-01-01

    of the Smart Grids (SGs). A SG can operate interconnected to the main distribution grid or in islanded mode. This paper presents experimental tests for static and dynamic stability analysis carried out in a dedicated laboratory for research in distributed control and smart grid with a high share of renewable...... are required under different operation modes and loads. The testing reporting here includes three modes of operation: stand alone, parallel/hybrid and grid connection....

  10. 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

  11. Stabilizing Semiconductor Devices With Hydrogen

    Science.gov (United States)

    Overhauser, Albert W.; Maserjian, Joseph

    1989-01-01

    Damage by radiation healed rapidly. Feature provides continuous, rapid recovery of devices from degradation caused by hot electrons, photons, and ionizing radiation. Several candidate sites for palladium film catalysts, inserted during manufacture as integral parts of devices. Paladium films made by evaporation, sputtering, or chemical-vapor deposition. If additional storage required, thick layer of palladium plated on inside of package surrounding device. Hydrogen stored by exposing palladium to hydrogen gas just before package sealed hermetically.

  12. A Short History of Posterior Dynamic Stabilization

    Directory of Open Access Journals (Sweden)

    Cengiz Gomleksiz

    2012-01-01

    Full Text Available Interspinous spacers were developed to treat local deformities such as degenerative spondylolisthesis. To treat patients with chronic instability, posterior pedicle fixation and rod-based dynamic stabilization systems were developed as alternatives to fusion surgeries. Dynamic stabilization is the future of spinal surgery, and in the near future, we will be able to see the development of new devices and surgical techniques to stabilize the spine. It is important to follow the development of these technologies and to gain experience using them. In this paper, we review the literature and discuss the dynamic systems, both past and present, used in the market to treat lumbar degeneration.

  13. Photochemical stability of electrochromic polymers and devices

    DEFF Research Database (Denmark)

    Jensen, Jacob; Madsen, Morten Vesterager; Krebs, Frederik C

    2013-01-01

    The stability of fully printed flexible organic electrochromics based on 11 different conjugated polymers is explored from the fundamental chemical degradation level to the operational device level. The photochemical stability of the electrochromic polymers (ECPs) is studied enabling an analysis...... operations for many years under indoor conditions and for a few years under outside conditions. Finally, functioning electrochromic devices (ECDs) were made and the effect of illumination on the response time and optical contrast was established. This report shows that encapsulated electrochromic devices...... based on flexible barrier substrates exhibit increased stability and are indeed viable in devices such as shading elements, light management systems, displays with low switching speed requirements and signage. © 2013 The Royal Society of Chemistry....

  14. Device Applications of Nonlinear Dynamics

    CERN Document Server

    Baglio, Salvatore

    2006-01-01

    This edited book is devoted specifically to the applications of complex nonlinear dynamic phenomena to real systems and device applications. While in the past decades there has been significant progress in the theory of nonlinear phenomena under an assortment of system boundary conditions and preparations, there exist comparatively few devices that actually take this rich behavior into account. "Device Applications of Nonlinear Dynamics" applies and exploits this knowledge to make devices which operate more efficiently and cheaply, while affording the promise of much better performance. Given the current explosion of ideas in areas as diverse as molecular motors, nonlinear filtering theory, noise-enhanced propagation, stochastic resonance and networked systems, the time is right to integrate the progress of complex systems research into real devices.

  15. Power System Stability Enhancement Using Fact Devices

    Directory of Open Access Journals (Sweden)

    Mr. B. T. Ramakrishna Rao

    2014-04-01

    Full Text Available The development of the modern power system has led to an increasing complexity in the study of power systems, and also presents new challenges to power system stability, and in particular, to the aspects of transient stability and small-signal stability. So Power system engineers are currently facing challenges to increase the power transfer capabilities of existing transmission system. This is where the Flexible AC Transmission Systems (FACTS technology comes into effect with relatively low investment, compared to new transmission or generation facilities. Flexible AC transmission system (FACTS devices use power electronics components to maintain controllability and capability of electrical power system. The paper aims towards the performance of UPFC is compared with other FACTS devices such as Static Synchronous Series Compensator (SSSC, Thyristor Controlled Series Capacitor (TCSC, and Static Var Compensator (SVC respectively. The simulation results demonstrate the effectiveness of the UPFC on transient stability of the system.

  16. The Dynamics of Stability

    DEFF Research Database (Denmark)

    Hedegaard, Troels Fage

    politiske aktører der greb disse muligheder. Disse historiske faktorer, der hjalp med at skabe opbakning til velfærdsstaten, er dog blevet svækket med tiden, mens støtten til modellen forbliver stabil. Denne umiddelbare modsætning er denne afhandlings omdrejningspunkt. Derfor vender jeg I denne afhandling...... trække på policy feedback teori, som den primære teoretiske ramme, og ud fra dette beskrive og teste sociale mekanismer der kan forklare den vedvarende opbakning til velfærdsmodellen. Disse social mekanismer eksisterer ikke kun i de nordiske lande, men skulle være mere udbredt her, og kan dermed hjælpe...

  17. Pedicle Screw-Based Posterior Dynamic Stabilization: Literature Review

    Directory of Open Access Journals (Sweden)

    Dilip K. Sengupta

    2012-01-01

    Full Text Available Posterior dynamic stabilization (PDS indicates motion preservation devices that are aimed for surgical treatment of activity related mechanical low back pain. A large number of such devices have been introduced during the last 2 decades, without biomechanical design rationale, or clinical evidence of efficacy to address back pain. Implant failure is the commonest complication, which has resulted in withdrawal of some of the PDS devices from the market. In this paper the authors presented the current understanding of clinical instability of lumbar motions segment, proposed a classification, and described the clinical experience of the pedicle screw-based posterior dynamic stabilization devices.

  18. The condition for dynamic stability

    NARCIS (Netherlands)

    Hof, AL; Gazendam, MGJ; Sinke, WE

    The well-known condition for standing stability in static situations is that the vertical projection of the centre of mass (CoM) should be within the base of support (BoS). On the basis of a simple inverted pendulum model, an extension of this rule is proposed for dynamical situations: the position

  19. Dynamical stability of Hamiltonian systems

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Dynamical stability has become the center of study on Hamiltonian system. In this article we intro-duce the recent development in some areas closely related to this topic, such as the KAM theory, Mather theory, Arnolddiffusion and non-singular collision of n-body problem.

  20. The condition for dynamic stability

    NARCIS (Netherlands)

    Hof, AL; Gazendam, MGJ; Sinke, WE

    2005-01-01

    The well-known condition for standing stability in static situations is that the vertical projection of the centre of mass (CoM) should be within the base of support (BoS). On the basis of a simple inverted pendulum model, an extension of this rule is proposed for dynamical situations: the position

  1. Optimal Coordinated Design of Multiple Damping Controllers Based on PSS and UPFC Device to Improve Dynamic Stability in the Power System

    Directory of Open Access Journals (Sweden)

    A. N. Hussain

    2013-01-01

    Full Text Available Unified Power Flow Controller (UPFC device is applied to control power flow in transmission lines. Supplementary damping controller can be installed on any control channel of the UPFC inputs to implement the task of Power Oscillation Damping (POD controller. In this paper, we have presented the simultaneous coordinated design of the multiple damping controllers between Power System Stabilizer (PSS and UPFC-based POD or between different multiple UPFC-based POD controllers without PSS in a single-machine infinite-bus power system in order to identify the design that provided the most effective damping performance. The parameters of the damping controllers are optimized utilizing a Chaotic Particle Swarm Optimization (CPSO algorithm based on eigenvalue objective function. The simulation results show that the coordinated design of the multiple damping controllers has high ability in damping oscillations compared to the individual damping controllers. Furthermore, the coordinated design of UPFC-based POD controllers demonstrates the superiority over the coordinated design of PSS and UPFC-based POD controllers for enhancing greatly the stability of the power system.

  2. Basin stability in delayed dynamics

    Science.gov (United States)

    Leng, Siyang; Lin, Wei; Kurths, Jürgen

    2016-02-01

    Basin stability (BS) is a universal concept for complex systems studies, which focuses on the volume of the basin of attraction instead of the traditional linearization-based approach. It has a lot of applications in real-world systems especially in dynamical systems with a phenomenon of multi-stability, which is even more ubiquitous in delayed dynamics such as the firing neurons, the climatological processes, and the power grids. Due to the infinite dimensional property of the space for the initial values, how to properly define the basin’s volume for delayed dynamics remains a fundamental problem. We propose here a technique which projects the infinite dimensional initial state space to a finite-dimensional Euclidean space by expanding the initial function along with different orthogonal or nonorthogonal basis. A generalized concept of basin’s volume in delayed dynamics and a highly practicable calculating algorithm with a cross-validation procedure are provided to numerically estimate the basin of attraction in delayed dynamics. We show potential applicabilities of this approach by applying it to study several representative systems of biological or/and physical significance, including the delayed Hopfield neuronal model with multistability and delayed complex networks with synchronization dynamics.

  3. Aging of dynamically stabilized microtubules

    CERN Document Server

    Ebbinghaus, M

    2009-01-01

    The microtubule network, an important part of the cytoskeleton, is constantly remodeled by alternating phases of growth and shrinkage of individual filaments. Plus-end tracking proteins (+TIPs) interact with the microtubule and in many cases alter its dynamics. While it is established that the prototypal CLIP-170 enhances microtubule stability by increasing rescues, the plus-end tracking mechanism is still under debate. We present a model for microtubule dynamics in which a rescue factor is dynamically added to the filament while growing. As a consequence, the filament shows aging behavior which should be experimentally accessible and thus allow one to exclude some hypothesized models of the inclusion of rescue factors at the microtubule plus end. Additionally, we show the strong influence of the cell geometry on the quantitative results.

  4. Stabilization strategies for unstable dynamics.

    Directory of Open Access Journals (Sweden)

    Devjani J Saha

    Full Text Available BACKGROUND: When humans are faced with an unstable task, two different stabilization mechanisms are possible: a high-stiffness strategy, based on the inherent elastic properties of muscles/tools/manipulated objects, or a low-stiffness strategy, based on an explicit positional feedback mechanism. Specific constraints related to the dynamics of the task and/or the neuromuscular system often force people to adopt one of these two strategies. METHODOLOGY/FINDINGS: This experiment was designed such that subjects could achieve stability using either strategy, with a marked difference in terms of effort and control requirements between the two strategies. The task was to balance a virtual mass in an unstable environment via two elastic linkages that connected the mass to each hand. The dynamics of the mass under the influence of the unstable force field and the forces applied through the linkages were simulated using a bimanual, planar robot. The two linkages were non-linear, with a stiffness that increased with the amount of stretch. The mass could be stabilized by stretching the linkages to achieve a stiffness that was greater than the instability coefficient of the unstable field (high-stiffness, or by balancing the mass with sequences of small force impulses (low-stiffness. The results showed that 62% of the subjects quickly adopted the high-stiffness strategy, with stiffness ellipses that were aligned along the direction of instability. The remaining subjects applied the low-stiffness strategy, with no clear preference for the orientation of the stiffness ellipse. CONCLUSIONS: The choice of a strategy was based on the bimanual coordination of the hands: high-stiffness subjects achieved stability quickly by separating the hands to stretch the linkages, while the low-stiffness subjects kept the hands close together and took longer to achieve stability but with lower effort. We suggest that the existence of multiple solutions leads to different types

  5. Dynamic and galvanic stability of stretchable supercapacitors.

    Science.gov (United States)

    Li, Xin; Gu, Taoli; Wei, Bingqing

    2012-12-12

    Stretchable electronics are emerging as a new technological advancement, since they can be reversibly stretched while maintaining functionality. To power stretchable electronics, rechargeable and stretchable energy storage devices become a necessity. Here, we demonstrate a facile and scalable fabrication of full stretchable supercapacitor, using buckled single-walled carbon nanotube macrofilms as the electrodes, an electrospun membrane of elastomeric polyurethane as the separator, and an organic electrolyte. We examine the electrochemical performance of the fully stretchable supercapacitors under dynamic stretching/releasing modes in different stretching strain rates, which reveal the true performance of the stretchable cells, compared to the conventional method of testing the cells under a statically stretched state. In addition, the self-discharge of the supercapacitor and the electrochemical behavior under bending mode are also examined. The stretchable supercapacitors show excellent cyclic stability under electrochemical charge/discharge during in situ dynamic stretching/releasing.

  6. CIGS Material and Device Stability: A Processing Perspective (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Ramanathan, K.

    2012-03-01

    This is a general overview of CIGS material and device fundamentals. In the first part, the basic features of high efficiency CIGS absorbers and devices are described. In the second part, some examples of previous collaboration with Shell Solar CIGSS graded absorbers and devices are shown to illustrate how process information was used to correct deviations and improve the performance and stability.

  7. Stability Analysis of MEMS Gyroscope Dynamic Systems

    OpenAIRE

    M. Naser-Moghadasi; S. A. Olamaei; F. Setoudeh

    2013-01-01

    In this paper, the existence of a common quadratic Lyapunov function for stability analysis of MEMS Gyroscope dynamic systems has been studied then a new method based on stochastic stability of MEMS Gyroscope system has been proposed.

  8. Stability in dynamical systems I

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Stability, Nonlinearity and Reliability of Electrostatically Actuated MEMS Devices

    Directory of Open Access Journals (Sweden)

    Di Chen

    2007-05-01

    Full Text Available Electrostatic micro-electro-mechanical system (MEMS is a special branch with a wide range of applications in sensing and actuating devices in MEMS. This paper provides a survey and analysis of the electrostatic force of importance in MEMS, its physical model, scaling effect, stability, nonlinearity and reliability in detail. It is necessary to understand the effects of electrostatic forces in MEMS and then many phenomena of practical importance, such as pull-in instability and the effects of effective stiffness, dielectric charging, stress gradient, temperature on the pull-in voltage, nonlinear dynamic effects and reliability due to electrostatic forces occurred in MEMS can be explained scientifically, and consequently the great potential of MEMS technology could be explored effectively and utilized optimally. A simplified parallel-plate capacitor model is proposed to investigate the resonance response, inherent nonlinearity, stiffness softened effect and coupled nonlinear effect of the typical electrostatically actuated MEMS devices. Many failure modes and mechanisms and various methods and techniques, including materials selection, reasonable design and extending the controllable travel range used to analyze and reduce the failures are discussed in the electrostatically actuated MEMS devices. Numerical simulations and discussions indicate that the effects of instability, nonlinear characteristics and reliability subjected to electrostatic forces cannot be ignored and are in need of further investigation.

  10. Local Dynamic Stability Associated with Load Carrying

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2013-03-01

    Conclusion: Current study confirmed the sensitivity of local dynamic stability measure in load carrying situation. It was concluded that load carrying tasks were associated with declined local dynamic stability, which may result in increased risk of fall accident. This finding has implications in preventing fall accidents associated with occupational load carrying.

  11. Trait diversity promotes stability of community dynamics

    DEFF Research Database (Denmark)

    Zhang, Lai; Thygesen, Uffe Høgsbro; Knudsen, Kim;

    2013-01-01

    The theoretical exploration of how diversity influences stability has traditionally been approached by species-centric methods. Here we offer an alternative approach to the diversity–stability problem by examining the stability and dynamics of size and trait distributions of individuals. The anal...

  12. Material and Device Stability in Perovskite Solar Cells.

    Science.gov (United States)

    Kim, Hui-Seon; Seo, Ja-Young; Park, Nam-Gyu

    2016-09-22

    Organic-inorganic halide perovskite solar cells have attracted great attention because of their superb efficiency reaching 22 % and low-cost, facile fabrication processing. Nevertheless, stability issues in perovskite solar cells seem to block further advancements toward commercialization. Thus, device stability is one of the important topics in perovskite solar cell research. In the beginning, the poor moisture resistivity of the perovskite layer was considered as a main problem that hindered further development of perovskite solar cells, which encouraged engineering of the perovskite or protection of the perovskite by a buffer layer. Soon after, other parameters affecting long-term stability were sequentially found and various attempts have been made to enhance intrinsic and extrinsic stability. Here we review the recent progresses addressing stability issues in perovskite solar cells. In this report, we investigated factors affecting stability from material and device points of view. To gain a better understanding of the stability of the bulk perovskite material, decomposition mechanisms were investigated in relation to moisture, photons, and heat. Stability of full device should also be carefully examined because its stability is dependent not only on bulk perovskite but also on the interfaces and selective contacts. In addition, ion migration and current-voltage hysteresis were found to be closely related to stability.

  13. Dynamic Analysis of Power System Voltage Stability.

    Science.gov (United States)

    Gebreselassie, Assefa

    This thesis investigates the effects of loads and voltage regulators on the dynamic voltage stability of power systems. The analysis focuses on the interactions of machine flux dynamics with loads and voltage control devices. The results are based on eigenvalue analysis of the linearized models and time simulation of the nonlinear models, using models from the Power System Toolbox, a Matlab -based package for the simulation and small signal analysis of nonlinear power systems. The voltage stability analysis results are developed using a single machine single load system with typical machine and network parameters and the NPCC 10-machine system. Dynamic models for generators, exciters and loads are used. The generator is modeled with a pair of poles and one damper circuit in both the d-axis and the q-axis. Saturation effects are included in the model. The IEEE Type DC1 DC commutator exciter model is used for all the exciters. Five different types of loads: constant impedance, constant current, constant power, a first order induction motor model (slip model) and a third order induction motor model (slip-flux model) are considered. The modes of instability and the stability limits of the different representation of loads are examined for two different operating modes of the exciters. The first, when all the exciters are on automatic control and the second when some exciters are on manual control. Modal participation factors are used to determine the characteristics of the critical modes. The characteristics of the unstable modes are verified by performing time simulation of the nonlinear models. Oscillatory and non-oscillatory instabilities are experienced by load buses when all the exciters are on automatic control and some exciters are on manual control respectively, for loads which are predominantly constant power and induction motors. It is concluded that the mode of instability does not depend on the type of loads but on the operating condition of the exciters

  14. Consensus stability testing protocols for organic photovoltaic materials and devices

    DEFF Research Database (Denmark)

    Reese, Matthew O.; Gevorgyan, Suren; Jørgensen, Mikkel

    2011-01-01

    Procedures for testing organic solar cell devices and modules with respect to stability and operational lifetime are described. The descriptions represent a consensus of the discussion and conclusions reached during the first 3 years of the international summit on OPV stability (ISOS). The proced...

  15. Consensus stability testing protocols for organic photovoltaic materials and devices

    NARCIS (Netherlands)

    Reese, M.O.; Gevorgyan, S.A.; Jørgensen, M.; Bundgaard, E.; Kurtz, S.R.; Ginley, D.S.; Olson, D.C.; Lloyd, M.T.; Morvillo, P.; Katz, E.A.; Elschner, A.; Haillant, O.; Currier, T.R.; Shrotriya, V.; Hermenau, M.; Riede, M.; Kirov, K.R.; Trimmel, G.; Rath, T.; Inganäs, O.; Zhang, F.; Andersson, M.; Tvingstedt, K.; Lira-Cantu, M.; Laird, D.; McGuiness, C.; Gowrisanker, S.; Pannone, M.; Xiao, M.; Hauch, J.; Steim, R.; Delongchamp, D.M.; Rösch, R.; Hoppe, H.; Espinosa, N.; Urbina, A.; Yaman-Uzunoglu, G.; Bonekamp, J.-B.; Breemen, A.J.J.M. van; Girotto, C.; Voroshazi, E.; Krebs, F.C.

    2011-01-01

    Procedures for testing organic solar cell devices and modules with respect to stability and operational lifetime are described. The descriptions represent a consensus of the discussion and conclusions reached during the first 3 years of the international summit on OPV stability (ISOS). The procedure

  16. Biomechanics of Posterior Dynamic Stabilization Systems

    Directory of Open Access Journals (Sweden)

    D. U. Erbulut

    2013-01-01

    Full Text Available Spinal rigid instrumentations have been used to fuse and stabilize spinal segments as a surgical treatment for various spinal disorders to date. This technology provides immediate stability after surgery until the natural fusion mass develops. At present, rigid fixation is the current gold standard in surgical treatment of chronic back pain spinal disorders. However, such systems have several drawbacks such as higher mechanical stress on the adjacent segment, leading to long-term degenerative changes and hypermobility that often necessitate additional fusion surgery. Dynamic stabilization systems have been suggested to address adjacent segment degeneration, which is considered to be a fusion-associated phenomenon. Dynamic stabilization systems are designed to preserve segmental stability, to keep the treated segment mobile, and to reduce or eliminate degenerative effects on adjacent segments. This paper aimed to describe the biomechanical aspect of dynamic stabilization systems as an alternative treatment to fusion for certain patients.

  17. Geometry and stability of dynamical systems

    CERN Document Server

    Punzi, Raffaele

    2008-01-01

    We reconsider both the global and local stability of solutions of continuously evolving dynamical systems from a geometric perspective. We clarify that an unambiguous definition of stability generally requires the choice of additional geometric structure that is not intrinsic to the dynamical system itself. While global Lyapunov stability is based on the choice of seminorms on the vector bundle of perturbations, we propose a definition of local stability based on the choice of a linear connection. We show how this definition reproduces known stability criteria for second order dynamical systems. In contrast to the general case, the special geometry of Lagrangian systems provides completely intrinsic notions of global and local stability. We demonstrate that these do not suffer from the limitations occurring in the analysis of the Maupertuis-Jacobi geodesics associated to natural Lagrangian systems.

  18. Dynesys dynamic stabilization-related facet arthrodesis.

    Science.gov (United States)

    Fay, Li-Yu; Chang, Peng-Yuan; Wu, Jau-Ching; Huang, Wen-Cheng; Wang, Chun-Hao; Tsai, Tzu-Yun; Tu, Tsung-Hsi; Chang, Hsuan-Kan; Wu, Ching-Lan; Cheng, Henrich

    2016-01-01

    OBJECTIVE Dynamic stabilization devices are designed to stabilize the spine while preserving some motion. However, there have been reports demonstrating limited motion at the instrumented level of the lumbar spine after Dynesys dynamic stabilization (DDS). The causes of this limited motion and its actual effects on outcomes after DDS remain elusive. In this study, the authors investigate the incidence of unintended facet arthrodesis after DDS and clinical outcomes. METHODS This retrospective study included 80 consecutive patients with 1- or 2-level lumbar spinal stenosis who underwent laminectomy and DDS. All medical records, radiological data, and clinical evaluations were analyzed. Imaging studies included pre- and postoperative radiographs, MR images, and CT scans. Clinical outcomes were measured by a visual analog scale (VAS) for back and leg pain, the Oswestry Disability Index (ODI), and Japanese Orthopaedic Association (JOA) scores. Furthermore, all patients had undergone postoperative CT for the detection of unintended arthrodesis of the facets at the indexed level, and range of motion was measured on standing dynamic radiographs. RESULTS A total of 70 patients (87.5%) with a mean age of 64.0 years completed the minimum 24-month postoperative follow-up (mean duration 29.9 months). Unintended facet arthrodesis at the DDS instrumented level was demonstrated by CT in 38 (54.3%) of the 70 patients. The mean age of patients who had facet arthrodesis was 9.8 years greater than that of the patients who did not (68.3 vs 58.5 years, p = 0.009). There were no significant differences in clinical outcomes, including VAS back and leg pain, ODI, and JOA scores between patients with and without the unintended facet arthrodesis. Furthermore, those patients older than 60 years were more likely to have unintended facet arthrodesis (OR 12.42) and immobile spinal segments (OR 2.96) after DDS. Regardless of whether unintended facet arthrodesis was present or not, clinical

  19. Production, characterization and stability of organic solar cell devices

    Energy Technology Data Exchange (ETDEWEB)

    Gevorgyan, S.A.

    2010-01-15

    Despite the fact that the field of organic photovoltaics (OPVs) is in a rapid progress, organic solar cells continue taking backstage roll in the growing markets of various solar technologies. The main challenge of the field is to develop devices that would possess all the optimal properties required for efficient, stable and cheap solar cells, i.e. devices that can deliver high photoconversion efficiencies and long lifetimes and can be efficiently produced in large scales using roll-to-roll coating technologies. This dissertation is primarily devoted to the issues of photoconversion efficiency and device lifetimes. In particular, descriptions of some practical approaches for different device designs and processing of active layer for typical small scale OPV devices were presented. The emphasis was put on some optimizing techniques for processing of active layer that can significantly improve the device photoconversion efficiency. The techniques were further applied for manufacturing and characterization of solar cell devices based on various materials. In particular, a number of thermocleavable polymers were studied and devices based on such materials were produced and characterized. The applicability of such materials in photovoltaic devices was shown and further challenges were discussed. Another task of this work was to manufacture and study inverted device structures and compare their properties with normal structure based devices. Device based on both structure were successfully produced with same level of performance in terms of photoconversion efficiency, yet with totally different stability performance. As another task, metal oxides, such as MoO{sub 3} or V{sub 2}O{sub 5} were studied in solar cell devices as buffer layers instead of PEDOT:PSS. Although the device efficiencies obtained with metal oxides were inferior to PEDOT based device, it was shown that such materials can possibly improve the device efficiency if the processing of the layers is

  20. Dynamic Circuit Model for Spintronic Devices

    KAUST Repository

    Alawein, Meshal

    2017-01-09

    In this work we propose a finite-difference scheme based circuit model of a general spintronic device and benchmark it with other models proposed for spintronic switching devices. Our model is based on the four-component spin circuit theory and utilizes the widely used coupled stochastic magnetization dynamics/spin transport framework. In addition to the steady-state analysis, this work offers a transient analysis of carrier transport. By discretizing the temporal and spatial derivatives to generate a linear system of equations, we derive new and simple finite-difference conductance matrices that can, to the first order, capture both static and dynamic behaviors of a spintronic device. We also discuss an extension of the spin modified nodal analysis (SMNA) for time-dependent situations based on the proposed scheme.

  1. Dynamic Analysis of Mobile Device Applications

    Energy Technology Data Exchange (ETDEWEB)

    Corey Thuen

    2013-01-01

    The On-Device Dynamic Analysis of Mobile Applications (ODAMA) project was started in an effort to protect mobile devices used in Industrial Control Systems (ICS) from cyber attack. Because mobile devices hide as much of the “computer” as possible, the user’s ability to assess the software running on their system is limited. The research team chose Google’s Android platform for this initial research because it is open source and it would give us freedom in our approach, including the ability to modify the mobile device’s operating system itself. The research team concluded that a Privileged Application was the right approach, and the result was ODAMA. This project is an important piece of the work to secure the expanding use of mobile devices with our nation’s critical infrastructure.

  2. Stabilization of LCD devices via geometric alteration.

    Science.gov (United States)

    Jeon, Il; Yoon, MinSung; Lee, Je-Hoon

    2013-02-20

    Glass bending in LCD displays is an inherent problem that has challenged many engineers. As a solution to this problem, we propose a methodology that can tackle the root of the phenomenon in terms of linear elastic beam theory. Using this hypothesis, we devised a background theory and a solution. In this paper, we present a glass panel to which geometrical changes, such as furrow, groove, and curb have been applied. These geometrical changes are applied to the nonactive area of the glass panel. To confirm the validity of our approach, we conducted simulation tests as well as hands-on experiments to observe the thermo-mechanical behavior of the device under various conditions. The simulation results using the Ansys simulator show that the proposed technique can reduce the deformation level of panel bending by 40%. In the experiment using a bare cell with polarizer films attached and with performing the high temperature reliability test, the deformation level of panel bending is reduced by half compared to the reference glass panel without any geometric alteration.

  3. Reliability Analysis of Dynamic Stability in Waves

    DEFF Research Database (Denmark)

    Søborg, Anders Veldt

    2004-01-01

    exhibit sufficient characteristics with respect to slope at zero heel (GM value), maximum leverarm, positive range of stability and area below the leverarm curve. The rule-based requirements to calm water leverarm curves are entirely based on experience obtained from vessels in operation and recorded......The assessment of a ship's intact stability is traditionally based on a semi-empirical deterministic concept that evaluates the characteristics of ship's calm water restoring leverarm curves. Today the ship is considered safe with respect to dynamic stability if its calm water leverarm curves...... accidents in the past. The rules therefore only leaves little room for evaluation and improvement of safety of a ship's dynamic stability. A few studies have evaluated the probability of ship stability loss in waves using Monte Carlo simulations. However, since this probability may be in the order of 10...

  4. Improved stability of solution processed photovoltaic devices using PQT-12

    Energy Technology Data Exchange (ETDEWEB)

    Yuen, Avery P.; Jovanovic, Stephen M.; Preston, John S.; Bamsey, Nathan M. [Department of Engineering Physics, McMaster University, 1280 Main Street West, Hamilton, Ontario (Canada); Hor, Ah-Mee; Klenkler, Richard A. [Xerox Research Centre of (Canada); Loutfy, Rafik O. [Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario (Canada)

    2010-12-15

    Photovoltaic devices made from blends of electron donating poly(3,3'''-didodecylquaterthiophene) (PQT-12) and electron accepting [6,6]-phenyl C{sub 61} butyric acid methyl ester (PCBM) are fabricated, and the device performance is measured over a period of 88 h to determine device stability. Results are compared against similar devices incorporating P3HT as the electron donor. Devices based on PQT-12 demonstrate a significant improvement in device stability, with a calculated half-life of 190,000 h when operated in an inert environment. A fluorescence study is also conducted on bare films of PQT-12 and P3HT and shows that the PQT-12 films are significantly more stable in air than P3HT. In addition, given the slower decay of bare films stored in vacuum, the results indicate that the exposure of the active layer to air is a significant contributor to performance decay of completed devices. (author)

  5. Dynamic stability experiment of Maglev systems

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Y.; Mulcahy, T.M.; Chen, S.S. [and others

    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 documents magnetic-force data obtained from both measurements and calculations. Because dynamic instability is not acceptable for any commercial 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 electrodynamic system (EDS)-type vehicle model were obtained from both experimental observations and computer simulations for a five-degree-of-freedom Maglev vehicle moving on a guideway consisting of double L-shaped aluminum segments attached to a rotating wheel. The experimental and theoretical analyses developed in this study identify basic stability characteristics and future research needs of Maglev systems.

  6. Stability Analysis of a Repairable System with Warning Device and Repairman Vacation

    Directory of Open Access Journals (Sweden)

    Yangli Ren

    2013-01-01

    probability analysis method, the system is first transformed into a group of integrodifferential equations. Then, the existence and uniqueness as well as regularity of the system dynamic solution are discussed with the functional analysis method. Further, the asymptotic stability, especially the exponential stability of the system dynamic solution, is studied by using the strongly continuous semigroup theory or C0 semigroup theory. The reliability indices and some applications (such as the comparisons of indices and profit of systems with and without warning device, as well as numerical examples, are presented at the end of the paper.

  7. Unifying dynamical and structural stability of equilibria

    Science.gov (United States)

    Arnoldi, Jean-François; Haegeman, Bart

    2016-09-01

    We exhibit a fundamental relationship between measures of dynamical and structural stability of linear dynamical systems-e.g. linearized models in the vicinity of equilibria. We show that dynamical stability, quantified via the response to external perturbations (i.e. perturbation of dynamical variables), coincides with the minimal internal perturbation (i.e. perturbations of interactions between variables) able to render the system unstable. First, by reformulating a result of control theory, we explain that harmonic external perturbations reflect the spectral sensitivity of the Jacobian matrix at the equilibrium, with respect to constant changes of its coefficients. However, for this equivalence to hold, imaginary changes of the Jacobian's coefficients have to be allowed. The connection with dynamical stability is thus lost for real dynamical systems. We show that this issue can be avoided, thus recovering the fundamental link between dynamical and structural stability, by considering stochastic noise as external and internal perturbations. More precisely, we demonstrate that a linear system's response to white-noise perturbations directly reflects the intensity of internal white-noise disturbance that it can accommodate before becoming stochastically unstable.

  8. Hybrid Dynamical Systems Modeling, Stability, and Robustness

    CERN Document Server

    Goebel, Rafal; Teel, Andrew R

    2012-01-01

    Hybrid dynamical systems exhibit continuous and instantaneous changes, having features of continuous-time and discrete-time dynamical systems. Filled with a wealth of examples to illustrate concepts, this book presents a complete theory of robust asymptotic stability for hybrid dynamical systems that is applicable to the design of hybrid control algorithms--algorithms that feature logic, timers, or combinations of digital and analog components. With the tools of modern mathematical analysis, Hybrid Dynamical Systems unifies and generalizes earlier developments in continuous-time and discret

  9. Vehicle lateral dynamics stabilization using active suspension

    Directory of Open Access Journals (Sweden)

    Drobný V.

    2008-12-01

    Full Text Available The paper deals with the investigation of active nonlinear suspension control in order to stabilize the lateral vehicle motion in similar way as systems like ESP do. The lateral stabilization of vehicle based on braking forces can be alternatively provided by the different setting of suspension forces. The basis of this control is the nonlinear property of the tyres. The vehicle has at least four wheels and it gives one or more redundant vertical forces that can be used for the different distribution of vertical suspension forces in such a way that resulting lateral and/or longitudinal forces create the required correction moment for lateral dynamic vehicle stabilization.

  10. Molecular Dynamics Studies of Nanofluidic Devices

    DEFF Research Database (Denmark)

    Zambrano Rodriguez, Harvey Alexander

    in opposite direction to the imposed thermal gradient also we measure higher velocities as higher thermal gradients are imposed. Secondly, we present an atomistic analysis of a molecular linear motor fabricated of coaxial carbon nanotubes and powered by thermal gradients. The MD simulation results indicate...... in transport caused by the walls become more dominant and the fluid consists of fewer molecules. Carbon nanotubes are tubular graphite molecules which can be imagined to function as nanoscale pipes or conduits. Another important material for nanofluidics applications is silica. Nowadays, silica nanochannels...... of such devices. Computational nanofluidics complements experimental studies by providing detailed spatial and temporal information of the nanosystem. In this thesis, we conduct molecular dynamics simulations to study basic nanoscale devices. We focus our studies on the understanding of transport mechanism...

  11. Stability and dynamics of magnetocapillary interactions

    CERN Document Server

    Chinomona, Rujeko; Mitchell, William H; Yao, Yao; Spagnolie, Saverio E

    2014-01-01

    Recent experiments have shown that floating ferromagnetic beads, under the influence of an oscillating background magnetic field, can move along a liquid-air interface in a sustained periodic locomotion [Lumay et al., Soft Matter, 2013, 9, 2420]. Dynamic activity arises from a periodically induced dipole-dipole repulsion between the beads acting in concert with capillary attraction. We investigate analytically and numerically the stability and dynamics of this magnetocapillary swimming, and explore other related topics including the steady and periodic equilibrium configurations of two and three beads. The swimming speed and system stability depend on a dimensionless measure of the relative repulsive and attractive forces which we term the magnetocapillary number. An oscillatory magnetic field may stabilize an otherwise unstable collinear configuration, and striking behaviors are observed in fast transitions to and from locomotory states, offering insight into the behavior and self-assembly of interface-bound...

  12. Organic thin film devices with stabilized threshold voltage and mobility, and method for preparing the devices

    Science.gov (United States)

    Nastasi, Michael Anthony; Wang, Yongqiang; Fraboni, Beatrice; Cosseddu, Piero; Bonfiglio, Annalisa

    2013-06-11

    Organic thin film devices that included an organic thin film subjected to a selected dose of a selected energy of ions exhibited a stabilized mobility (.mu.) and threshold voltage (VT), a decrease in contact resistance R.sub.C, and an extended operational lifetime that did not degrade after 2000 hours of operation in the air.

  13. Experimental Testing for Stability Analysis of Distributed Energy Resources Components with Storage Devices and Loads

    DEFF Research Database (Denmark)

    Mihet-Popa, Lucian; Groza, Voicu; Isleifsson, Fridrik Rafn

    2012-01-01

    Experimental Testing for Stability Analysis of Distributed Energy Resources Components with Storage Devices and Loads......Experimental Testing for Stability Analysis of Distributed Energy Resources Components with Storage Devices and Loads...

  14. Liquid Self-Balancing Device Effects on Flexible Rotor Stability

    Directory of Open Access Journals (Sweden)

    Leonardo Urbiola-Soto

    2013-01-01

    Full Text Available Nearly a century ago, the liquid self-balancing device was first introduced by M. LeBlanc for passive balancing of turbine rotors. Although of common use in many types or rotating machines nowadays, little information is available on the unbalance response and stability characteristics of this device. Experimental fluid flow visualization evidences that radial and traverse circulatory waves arise due to the interaction of the fluid backward rotation and the baffle boards within the self-balancer annular cavity. The otherwise destabilizing force induced by trapped fluids in hollow rotors, becomes a stabilizing mechanism when the cavity is equipped with adequate baffle boards. Further experiments using Particle Image Velocimetry (PIV enable to assess the active fluid mass fraction to be one-third of the total fluid mass. An analytical model is introduced to study the effects of the active fluid mass fraction on a flexible rotor supported by flexible supports excited by bwo different destabilizing mechanisms; rotor internal friction damping and aerodynamic cross-coupling. It is found that the fluid radial and traverse forces contribute to the balancing action and to improve the rotor stability, respectively.

  15. Linear Stability Analysis of Dynamical Quadratic Gravity

    CERN Document Server

    Ayzenberg, Dimitry; Yunes, Nicolas

    2013-01-01

    We perform a linear stability analysis of dynamical, quadratic gravity in the high-frequency, geometric optics approximation. This analysis is based on a study of gravitational and scalar modes propagating on spherically-symmetric and axially-symmetric, vacuum solutions of the theory. We find dispersion relations that do no lead to exponential growth of the propagating modes, suggesting the theory is linearly stable on these backgrounds. The modes are found to propagate at subluminal and superluminal speeds, depending on the propagating modes' direction relative to the background geometry, just as in dynamical Chern-Simons gravity.

  16. Topological stabilization for synchronized dynamics on networks

    Science.gov (United States)

    Cencetti, Giulia; Bagnoli, Franco; Battistelli, Giorgio; Chisci, Luigi; Di Patti, Francesca; Fanelli, Duccio

    2017-01-01

    A general scheme is proposed and tested to control the symmetry breaking instability of a homogeneous solution of a spatially extended multispecies model, defined on a network. The inherent discreteness of the space makes it possible to act on the topology of the inter-nodes contacts to achieve the desired degree of stabilization, without altering the dynamical parameters of the model. Both symmetric and asymmetric couplings are considered. In this latter setting the web of contacts is assumed to be balanced, for the homogeneous equilibrium to exist. The performance of the proposed method are assessed, assuming the Complex Ginzburg-Landau equation as a reference model. In this case, the implemented control allows one to stabilize the synchronous limit cycle, hence time-dependent, uniform solution. A system of coupled real Ginzburg-Landau equations is also investigated to obtain the topological stabilization of a homogeneous and constant fixed point.

  17. Voltage stability analysis considering the load dynamic characteristics and the voltage control devices; Analisis de estabilidad de voltaje considerando las caracteristicas dinamicas de la carga y dispositivos de control de voltaje

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez Alvarez, Enrique

    2001-09-15

    The research work presented in this thesis, is centered in the voltage stability analysis of medium term considering the effect of the load characteristics and its interaction with the voltage control device models in the transmission network. More concretely, a type of load model is defined and studied with desirable characteristics for the study of the voltage stability, the generic load models derived from field tests and from the application of identification techniques and it is analyzed the influence of the application of control systems to improve the system stability margins. Also, alternatives to the power system modeling for the voltage stability study in complex systems are reviewed. In the first place a fundamental analysis of the voltage characteristics and stability in a simplified power system is presented and the method of adopted analysis is introduced. It is shown that the instability phenomenon is manifested as a singular type bifurcation induced from the critical way of voltage when the system is operated under stress conditions. Next, the contribution of the action of the control devices to the stability margin is analyzed and criteria of the stability analyses are deducted based on the study of such mode. Following a linear model of the power system with desirable characteristics for the study of the voltage stability of medium term is proposed and the characteristics of stability in the context of the study of complex systems are interpreted. The proposed analysis tool is based on the physical notion that the behavior of the voltage control systems in the generators is very rapid with regard to the behavior of the load and has its main application in the preliminary study of the voltage stability of medium and long term. From this model, an analytical tool based on the application of techniques of linear analysis is proposed to approach the problem of determination of critical voltage areas and the contribution of control devices to the

  18. Transient Stability Performance Analysis of Power System Using Facts Devices

    Directory of Open Access Journals (Sweden)

    M. Srinivasa Rao

    2014-02-01

    Full Text Available Transient stability is increasingly important for secure loading. Transient stability evaluation of large scale power systems is an extremely intricate and highly non linear problem. An important function of transient evaluation is to appraise the capability of the power system to with stand serious contingency in time, so that some emergencies or preventive control can be carried out to prevent system breakdown, the fault current so produced is diverted to the capacitor by using dual-STATCOM controller, results proved that voltage is maintained nearly constant, surge currents decreased and oscillations in generator have damped and hence system stability and continuity of supply are enhanced. If for UPFC, replacing series controller with shunt controller, it works as dual STATCOM. It has advantages as series pulse controller is not required and same pulses can be given to both STATCOMs. The shunt controller is so designed to act as low impedance path for short circuit current, thereby surge currents can be diverted to VSC. A general program for transient stability studies to incorporate FACTS devices is developed using MATLAB/SIMULINK.

  19. Longitudinal dynamic stability of a shuttle vehicle.

    Science.gov (United States)

    Vinh, N. X.; Laitone, E. V.

    1972-01-01

    Analytical study of the longitudinal dynamic stability of a nonrolling, lifting vehicle gliding at hypersonic speeds. The analysis applies to shuttle vehicles designed for operating up to the rim of a planetary atmosphere. A general nondimensional time transformation is introduced to derive a unified second-order linear differential equation for the angle of attack, valid for all types of reentry of a general type of vehicle. The stability of motion is discussed for two fundamental regimes of flight that are based on widely different assumptions. For near ballistic entry along a straight line trajectory, the equation reduces to a confluent hypergeometric equation, the solution of which can be expressed in terms of Whittaker's function. Using a theorem in the theory of stability of differential equations, criteria for damped oscillations are derived. It is shown that the aerodynamic criteria for stability are the same as for the case of ballistic entry. In addition, for each vehicle configuration, and specified planetary atmosphere, there exists an altitude range where the angle of attack frequency is nearly equal to the orbital frequency causing instability in pitch. This resonance instability is due to the ellipticity of the orbit. Criteria for eccentricity instability are derived.

  20. Stability studies of Solar Optical Telescope dynamics

    Science.gov (United States)

    Gullapalli, Sarma N.; Pal, Parimal K.; Ruthven, Gregory P.

    1987-01-01

    The Solar Optical Telescope (SOT) is designed to operate as an attached payload mounted on the Instrument Pointing System (IPS) in the cargo bay of the Shuttle Orbiter. Pointing and control of SOT is accomplished by an active Articulated Primary Mirror (APM), an active Tertiary Mirror (TM), an elaborate set of optical sensors, electromechanical actuators and programmable controllers. The structural interactions of this complex control system are significant factors in the stability of the SOT. The preliminary stability study results of the SOT dynamical system are presented. Structural transfer functions obtained from the NASTRAN model of the structure were used. These studies apply to a single degree of freedom (elevation). Fully integrated model studies will be conducted in the future.

  1. Reliability Analysis of Dynamic Stability in Waves

    DEFF Research Database (Denmark)

    Søborg, Anders Veldt

    2004-01-01

    exhibit sufficient characteristics with respect to slope at zero heel (GM value), maximum leverarm, positive range of stability and area below the leverarm curve. The rule-based requirements to calm water leverarm curves are entirely based on experience obtained from vessels in operation and recorded......-4 per ship year such brute force Monte-Carlo simulations are not always feasible due to the required computational resources. Previous studies of dynamic stability of ships in waves typically focused on the capsizing event. In this study the objective is to establish a procedure that can identify...... the distribution of the exceedance probability may be established by an estimation of the out-crossing rate of the "safe set" defined by the utility function. This out-crossing rate will be established using the so-called Madsen's Formula. A bi-product of this analysis is a set of short wave time series...

  2. The Comprehensive Biomechanics and Load-Sharing of Semirigid PEEK and Semirigid Posterior Dynamic Stabilization Systems

    Directory of Open Access Journals (Sweden)

    D. K. Sengupta

    2013-01-01

    Full Text Available Alternatives to conventional rigid fusion have been proposed for several conditions related to degenerative disc disease when nonoperative treatment has failed. Semirigid fixation, in the form of dynamic stabilization or PEEK rods, is expected to provide compression under loading as well as an intermediate level of stabilization. This study systematically examines both the load-sharing characteristics and kinematics of these two devices compared to the standard of internal rigid fixators. Load-sharing was studied by using digital pressure films inserted between an artificially machined disc and two loading fixtures. Rigid rods, PEEK rods, and the dynamic stabilization system were inserted posteriorly for stabilization. The kinematics were quantified on ten, human, cadaver lumbosacral spines (L3-S1 which were tested under a pure bending moment, in flexion-extension, lateral bending, and axial rotation. The magnitude of load transmission through the anterior column was significantly greater with the dynamic device compared to PEEK rods and rigid rods. The contact pressures were distributed more uniformly, throughout the disc with the dynamic stabilization devices, and had smaller maximum point-loading (pressures on any particular point within the disc. Kinematically, the motion was reduced by both semirigid devices similarly in all directions, with slight rigidity imparted by a lateral interbody device.

  3. Beam stability & nonlinear dynamics. Formal report

    Energy Technology Data Exchange (ETDEWEB)

    Parsa, Z. [ed.

    1996-12-31

    his Report includes copies of transparencies and notes from the presentations made at the Symposium on Beam Stability and Nonlinear Dynamics, December 3-5, 1996 at the Institute for Theoretical Physics, University of California, Santa Barbara California, that was made available by the authors. Editing, reduction and changes to the authors contributions were made only to fulfill the printing and publication requirements. We would like to take this opportunity and thank the speakers for their informative presentations and for providing copies of their transparencies and notes for inclusion in this Report.

  4. Dynamical Stability of Slip-stacking Particles

    CERN Document Server

    Eldred, Jeffrey

    2014-01-01

    We study the stability of particles in slip-stacking configuration, used to nearly double proton beam intensity at Fermilab. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We find perturbative solutions for stable particle trajectories. We establish Booster beam quality requirements to achieve 97\\% slip-stacking efficiency. We show that slip-stacking dynamics directly correspond to the driven pendulum and to the system of two standing-wave traps moving with respect to each other.

  5. Dynamical stability of slip-stacking particles

    Energy Technology Data Exchange (ETDEWEB)

    Eldred, Jeffrey; Zwaska, Robert

    2014-09-01

    We study the stability of particles in slip-stacking configuration, used to nearly double proton beam intensity at Fermilab. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We find perturbative solutions for stable particle trajectories. We establish Booster beam quality requirements to achieve 97% slip-stacking efficiency. We show that slip-stacking dynamics directly correspond to the driven pendulum and to the system of two standing-wave traps moving with respect to each other.

  6. Dynamical Stability of Slip-stacking Particles

    Energy Technology Data Exchange (ETDEWEB)

    Eldred, Jeffrey [Fermilab; Zwaska, Robert [Fermilab

    2014-09-04

    We study the stability of particles in slip-stacking configuration, used to nearly double proton beam intensity at Fermilab. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We find perturbative solutions for stable particle trajectories. We establish Booster beam quality requirements to achieve 97% slip-stacking efficiency. We show that slip-stacking dynamics directly correspond to the driven pendulum and to the system of two standing-wave traps moving with respect to each other.

  7. Stability precision dynamic testing system on artillery

    Science.gov (United States)

    Wang, Chunyan; Li, Bo

    2014-12-01

    Dynamic feature of Weapon equipments is one of important performance index for evaluating the performance of the whole weapon system. The construction of target range in our country in fire control dynamic testing is relatively backward; therefore, it has greatly influenced the evaluation on the fire control system. In order to solve this problem, it's urgent to develop a new testing instrument so as to adjust to the armament research process and promote weapon system working more efficiently and thereby meeting the needs of modernization in national defense. This paper proposes a new measure which is used to test the stability precision of the fire control system, and it is installed on the moving base. Using the method, we develop a testing system which can test the stability precision of the fire control system and achieve a high precision results after testing. The innovation of the system is we can receive the image not only by CCD, but our eyes. It also adopts digital image-forming and image processing technique for real-time measurement and storing of the target information; it simultaneously adopts the method adjusting the platform and the corresponding fixture mounted on a sample to measure the stable precision and the precision of corner of stabilizator. In this paper, we make a description on the construction of the system and the idea of the designing of the optical system. Finally, we introduce the actual application of the system and testing results.

  8. ANALYSIS AND OPTIMISATION OF DYNAMIC STABILITY OF MOBILE WORKING MACHINES

    Directory of Open Access Journals (Sweden)

    Peter BIGOŠ

    2014-09-01

    Full Text Available This paper describes an investigation of the dynamic stability, which is specified for the mobile working machines. There are presented the basic theoretical principles of the stability theory together with an introduction of two illustrative examples of the dynamic stability analysis.

  9. SEMICONDUCTOR DEVICES Design consideration of the thermal and electro stability of multi-finger HBTs based on different device structures

    Science.gov (United States)

    Yanhu, Chen; Huajun, Shen; Xinyu, Liu; Hui, Xu; Ling, Li; Huijun, Li

    2010-10-01

    The thermal and electro stability of multi-finger heterojunction bipolar transistors (HBTs) with different structures were analyzed and discussed simultaneously. The thermal stability of the devices with different layout structures was assessed by the DC-IV test and thermal resistance calculation. Their electro stability was assessed by the calculation of the stability factor K based on the S parameter of the HBT. It is found that HBTs with higher thermal stability are prone to lower electro stability. The trade-off relationship between the two types of stability was explained and discussed by using a compact K-factor analytic formula which is derived from the small signal equivalent circuit model of HBT. The electro stability of the device with a thermal ballasting resistor was also discussed, based on the analytic formula.

  10. Device for separation of vortex gas-dynamic energy

    Science.gov (United States)

    Leontiev, A. I.; Burtsev, S. A.

    2015-10-01

    A device for separation of vortex gas-dynamic energy, which combines the mechanism of separation of vortex energy used in the Ranque-Hilsch tubes and the mechanism of separation of gas-dynamic energy, is proposed for supersonic flows. A method of calculation of this device is developed. A comparison is made that showed that, when working with natural gas, the cooling depth of half of the mass flow rate proves to be 1.3 times higher than that for the vortex tube and three times higher than that for the device for separation of the gas-dynamic energy.

  11. Effects of pelvic stabilization on lumbar muscle activity during dynamic exercise.

    Science.gov (United States)

    San Juan, Jun G; Yaggie, James A; Levy, Susan S; Mooney, Vert; Udermann, Brian E; Mayer, John M

    2005-11-01

    Many commonly utilized low-back exercise devices offer mechanisms to stabilize the pelvis and to isolate the lumbar spine, but the value of these mechanisms remains unclear. The purpose of this study was to examine the effect of pelvic stabilization on the activity of the lumbar and hip extensor muscles during dynamic back extension exercise. Fifteen volunteers in good general health performed dynamic extension exercise in a seated upright position on a lumbar extension machine with and without pelvic stabilization. During exercise, surface electromyographic activity of the lumbar multifidus and biceps femoris was recorded. The activity of the multifidus was 51% greater during the stabilized condition, whereas there was no difference in the activity of the biceps femoris between conditions. This study demonstrates that pelvic stabilization enhances lumbar muscle recruitment during dynamic exercise on machines. Exercise specialists can use these data when designing exercise programs to develop low back strength.

  12. Dynamic mapping of EDDL device descriptions to OPC UA

    Science.gov (United States)

    Atta Nsiah, Kofi; Schappacher, Manuel; Sikora, Axel

    2017-07-01

    OPC UA (Open Platform Communications Unified Architecture) is already a well-known concept used widely in the automation industry. In the area of factory automation, OPC UA models the underlying field devices such as sensors and actuators in an OPC UA server to allow connecting OPC UA clients to access device-specific information via a standardized information model. One of the requirements of the OPC UA server to represent field device data using its information model is to have advanced knowledge about the properties of the field devices in the form of device descriptions. The international standard IEC 61804 specifies EDDL (Electronic Device Description Language) as a generic language for describing the properties of field devices. In this paper, the authors describe a possibility to dynamically map and integrate field device descriptions based on EDDL into OPCUA.

  13. Methodological approach to assess tractor stability in normal operation in field using a commercial warning device

    Directory of Open Access Journals (Sweden)

    V. Rondelli

    2013-09-01

    Full Text Available Since Roll-Over Protective Structures (ROPS are mandatory on tractors, the number of fatalities caused in the event of an upset is definitely reduced. Nevertheless, fatal accidents caused by machine loss of stability are still of great concern. In fact, despite ROPS have reduced injury to agricultural operators, tractor stability is still a complex issue due to its high versatility in use, especially considering normal operations in field, when interactions with the environment such as soil morphology and climatic conditions are involved, as well as interactions with operator skills and experience. With the aim of collecting data on different variables influencing the dynamics of tractors in field, a commercial device that allows the continuous monitoring of working conditions and the active configuration of the machines was fitted on standard tractors in normal operation at the experimental farm of the Bologna University. The device consists of accelerometers, gyroscope, GSM/GPRS, GPS for geo-referencing and a transceiver for the automatic recognition of tractor-connected equipment. A microprocessor processes data and provides information, through a dedicated algorithm requiring data on the geometry of the tested tractor, on the level of risk for the operator in terms of probable loss of stability and suggests corrective measures to reduce the potential instability of the tractor.

  14. Dynamic Stabilization for Challenging Lumbar Degenerative Diseases of the Spine: A Review of the Literature

    Directory of Open Access Journals (Sweden)

    Tuncay Kaner

    2013-01-01

    Full Text Available Fusion and rigid instrumentation have been currently the mainstay for the surgical treatment of degenerative diseases of the spine over the last 4 decades. In all over the world the common experience was formed about fusion surgery. Satisfactory results of lumbar spinal fusion appeared completely incompatible and unfavorable within years. Rigid spinal implants along with fusion cause increased stresses of the adjacent segments and have some important disadvantages such as donor site morbidity including pain, wound problems, infections because of longer operating time, pseudarthrosis, and fatigue failure of implants. Alternative spinal implants were developed with time on unsatisfactory outcomes of rigid internal fixation along with fusion. Motion preservation devices which include both anterior and posterior dynamic stabilization are designed and used especially in the last two decades. This paper evaluates the dynamic stabilization of the lumbar spine and talks about chronologically some novel dynamic stabilization devices and thier efficacies.

  15. Investigation on shock waves stability in relativistic gas dynamics

    Directory of Open Access Journals (Sweden)

    Alexander Blokhin

    1993-05-01

    Full Text Available This paper is devoted to investigation of the linearized mixed problem of shock waves stability in relativistic gas dynamics. The problem of symmetrization of relativistic gas dynamics equations is also discussed.

  16. Device and method for measuring the dynamic interaction between bodies

    NARCIS (Netherlands)

    Veltink, Petrus H.

    2008-01-01

    The invention relates to a device for measuring the dynamic interaction, in particular power transfer and work performed, between a first and a second body, in particular during relatively random movements. The device comprises a housing in which at least one kinematic sensor and at least one

  17. On the Dynamic Stability of a Missile

    Directory of Open Access Journals (Sweden)

    K.C. Sharma

    1977-01-01

    Full Text Available The P-method given by Parks and Pritchard has been used to discuss the stability behaviour of a missile in free flight. General stability criteria for aerodynamic stabilisation have been obtained for slowly varying coefficients. The effect of pressure gradient on the stability of a coasting rocket has been explicitly examined. It is observed that the positive Magnus moment parameter ensures stability whereas a negative moment parameter would enhance the requirements of a larger stability margin.

  18. Dynamic stability of deformable elements of one class of aeroelastic constructions

    Science.gov (United States)

    Velmisov, Petr A.; Ankilov, Andrey V.; Semenova, Elizaveta P.

    2016-12-01

    At designing of the constructions and the devices interacting with the flow of gas or liquid, it is necessary to solve the problems associated with the investigation of the stability required for their functioning and operational reliability. The definition of stability of an elastic body corresponds to the Lyapunov's concept of stability of dynamical system. A mathematical model of the device relating to the vibration technique, which is intended for intensification of technological processes, for example, the process of mixing, is considered. The action of these devices is based on the oscillations of elastic elements at the flowing around gas or liquid flow. The dynamic stability of the elastic element, located inside of the flow channel with the subsonic flow of gas or liquid (in an ideal model of a compressible environment) is investigated. The model is described by coupled system of partial differential equations for the unknown functions - the potential of the gas velocity and deformation of the elastic element. On the basis of the construction of functional, the sufficient conditions of the dynamical stability, imposing restrictions on the free-stream velocity of the gas, the flexural stiffness of the elastic element, and other parameters of the mechanical system are obtained. The examples of construction of the stability regions for particular parameters of the mechanical system are presented.

  19. Dynamic training devices in CRM training

    Science.gov (United States)

    Lawver, J.

    1984-01-01

    Pilot training effectiveness and flying safety of a seasonal tour flight company are described. The change from single pilot to two pilot operated twin otters is examined. The use of the ATC 810 training device, its possibilities and training capacity is outlined. Problem areas which may arise, emergency system and pilot/passenger interaction are analyzed.

  20. Dynamic flight stability of hovering insects

    Institute of Scientific and Technical Information of China (English)

    Mao Sun; Jikang Wang; Yan Xiong

    2007-01-01

    The equations of motion of an insect with flapping wings are derived and then simplified to that of a flying body using the "rigid body" assumption. On the basis of the simplified equations of motion, the longitudinal dynamic flight stability of four insects (hoverfly, cranefly, dronefly and hawkmoth) in hovering flight is studied (the mass of the insects ranging from 11 to 1,648 mg and wingbeat frequency from 26 to 157Hz). The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis are used to solve the equations of motion. The validity of the "rigid body" assumption is tested and how differencesin size and wing kinematics influence the applicability of the "rigid body" assumption is investigated. The primary findings are: (1) For insects considered in the present study and those with relatively high wingbeat frequency (hover-fly, drone fly and bumblebee), the "rigid body" assumptionis reasonable, and for those with relatively low wingbeatfrequency (cranefly and howkmoth), the applicability of the"rigid body" assumption is questionable. (2) The same three natural modes of motion as those reported recently for a bumblebee are identified, i.e., one unstable oscillatory mode,one stable fast subsidence mode and one stable slow subsidence mode. (3) Approximate analytical expressions of the eigenvalues, which give physical insight into the genesis of the natural modes of motion, are derived. The expressions identify the speed derivative Mu (pitching moment produced by unit horizontal speed) as the primary source of the unstable oscillatory mode and the stable fast subsidence mode and Zw (vertical force produced by unit vertical speed) as the primary source of the stable slow subsidence mode.

  1. Dynamic Optical Grating Device and Associated Method for Modulating Light

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Chu, Sang-Hyon (Inventor)

    2012-01-01

    A dynamic optical grating device and associated method for modulating light is provided that is capable of controlling the spectral properties and propagation of light without moving mechanical components by the use of a dynamic electric and/or magnetic field. By changing the electric field and/or magnetic field, the index of refraction, the extinction coefficient, the transmittivity, and the reflectivity fo the optical grating device may be controlled in order to control the spectral properties of the light reflected or transmitted by the device.

  2. Fluid dynamics of heart assist device

    Science.gov (United States)

    Jones, R. T.

    1976-01-01

    Certain hemodynamic phenomena that arise in connection with the use of artificial blood pumping devices are reviewed. Among these are: (1) Flows produced by collapsing bulbs; (2) the impedance presented by the aorta; (3) limiting velocities and instability of flow in elastic vessels; (4) effectiveness of valveless arterio-arterial pumps, and (5) wave reflection phenomena and instabilities associated with the intra-aortic balloon pump.

  3. Research on Optimization, Dynamics and Stability of Stairclimbing Wheelchair

    Directory of Open Access Journals (Sweden)

    Shashank Shekhar Sahoo

    2016-03-01

    Full Text Available Since the invention of the wheel, man has always sought to reduce effort to get things done easily. Ultimately, it has resulted in the invention of the Robot, an Engineering Marvel. Up until now, the major factor that hampers widespread usage of robots is locomotion and maneuverability. They are not fit enough to conform even to the most commonplace terrain such as stairs. To overcome this, we are proposing a stair climbing wheelchair robot that looks a lot like a normal wheelchair but with additional stair-climbing functionality to adjust itself according to the height of the step The primarily goal of the prescribed manuscript herewith is to analyze the functional requirements, optimization methods, dynamics and stability during a tracked robotic wheelchair’s climbing of stairs mechanism. At first, the mechanical structure of the wheelchair is designed and the hardware composition of its full control system is devised. Secondly, based on the analysis of its stairs‐climbing process, the dynamical model of stairs‐climbing is established by using the classical mechanics method. Next, through simulation and experiments, the effectiveness of the dynamical model, its stability evaluation and performance parameters is verified. Such procedures will help in establishing a strong fundamental foundation steps to design and develop a standalone semi-autonomous wheelchair that will help and enable a physically challenged person by leg to climb difficult terrains like staircase and speed-breakers with ease and comfort. This design encompasses Renesas’s Arduino compatible GR-KAEDE boards, servo motors, high torque DC motors and various peripheral devices as incorporated in design diagram. We have also extended the application of wheelchair by integrating collision avoidance mechanism.

  4. An atomic magnetometer with autonomous frequency stabilization and large dynamic range.

    Science.gov (United States)

    Pradhan, S; Mishra, S; Behera, R; Poornima; Dasgupta, K

    2015-06-01

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz(1/2) @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.

  5. An atomic magnetometer with autonomous frequency stabilization and large dynamic range

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, S., E-mail: spradhan@barc.gov.in, E-mail: pradhans75@gmail.com; Poornima,; Dasgupta, K. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 85 (India); Homi Bhabha National Institute, Department of Atomic Energy, Mumbai 85 (India); Mishra, S.; Behera, R. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 85 (India)

    2015-06-15

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz{sup 1/2} @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.

  6. THE STABILIZATION SYSTEM ON PAYLOAD BUILT ON A DYNAMICALLY TUNED GYROSCOPE

    Directory of Open Access Journals (Sweden)

    D. M. Malyutin

    2016-01-01

    Full Text Available It is now widely distributed systems stabilization based on gyroscopes with three-degree-freedom and based on gyroscopes with ball suspension. The accuracy and resource of operation of such systems requires an increase. The problem of improving the accuracy and increasing the service life of information – measuring systems of stabilization can be solved by using as a sensitive element of a dynamically tuned gyroscope. Today the issue of achieving the potential of the metrological characteristics of information-measuring systems stabilization on dynamically tuned gyroscope is not fully resolved. It requires the development of mathematical models, different from the known, detailed description of the perturbations acting on a device. In addition, it is necessary to develop structures amplifying-transforming paths of the contours stabilization of information-measuring systems of stabilization on dynamically tuned gyroscopes, assuring higher accuracy and noise immunity of the system, what is the purpose of the work. In using the Euler equations obtained a complete mathematical model of functioning system with three motion bases, in detail taking into account the disturbances acting on the device. Considered are the peculiarities of mathematical description of dynamically tuned gyroscope. Dominant frequencies of components noise is identified in the output signal of the gyroscope. The original scheme of the contours stabilization is presented, that help increase the accuracy of stabilization at low frequencies and of providing the absence of systematic drift of the gyrostabilizer from the action of the permanent disturbing moment along the axis of stabilization. The dynamic calculations show the possibility of providing error of stabilization on payload not more than 0,0042 degree. 

  7. Impulsive Stabilization of Uncertain Dynamical Systems and Chaos Control

    Institute of Scientific and Technical Information of China (English)

    LIUBin; YAOJian; FANGJinqing; LIUXinzhi

    2004-01-01

    In this paper, a general impulsive control problem for uncertain dynamical systems is investigated.By utilizing the method of Lyapunov functions, a set of stability criteria for uncertain impulsive dynamical systems are established. These obtained results are then appliedto derive conditions under which an uncertain dynamical system can be robustly stabilized by an impulsive control law. Finally, we demonstrate our method by controlling the famous Lorenz system with uncertain perturbation.

  8. Walking in simulated Martian gravity: influence of the portable life support system's design on dynamic stability.

    Science.gov (United States)

    Scott-Pandorf, Melissa M; O'Connor, Daniel P; Layne, Charles S; Josić, Kresimir; Kurz, Max J

    2009-09-01

    With human exploration of the moon and Mars on the horizon, research considerations for space suit redesign have surfaced. The portable life support system (PLSS) used in conjunction with the space suit during the Apollo missions may have influenced the dynamic balance of the gait pattern. This investigation explored potential issues with the PLSS design that may arise during the Mars exploration. A better understanding of how the location of the PLSS load influences the dynamic stability of the gait pattern may provide insight, such that space missions may have more productive missions with a smaller risk of injury and damaging equipment while falling. We explored the influence the PLSS load position had on the dynamic stability of the walking pattern. While walking, participants wore a device built to simulate possible PLSS load configurations. Floquet and Lyapunov analysis techniques were used to quantify the dynamic stability of the gait pattern. The dynamic stability of the gait pattern was influenced by the position of load. PLSS loads that are placed high and forward on the torso resulted in less dynamically stable walking patterns than loads placed evenly and low on the torso. Furthermore, the kinematic results demonstrated that all joints of the lower extremity may be important for adjusting to different load placements and maintaining dynamic stability. Space scientists and engineers may want to consider PLSS designs that distribute loads evenly and low, and space suit designs that will not limit the sagittal plane range of motion at the lower extremity joints.

  9. Dynamic Stabilization in The Double-Well Duffing Oscillator

    CERN Document Server

    Kim, S Y; Kim, Sang-Yoon; Kim, Youngtae

    1999-01-01

    Bifurcations associated with stability of the saddle fixed point of the Poincaré map, arising from the unstable equilibrium point of the potential, are investigated in a forced Duffing oscillator with a double-well potential. One interesting behavior is the dynamic stabilization of the saddle fixed point. When the driving amplitude is increased through a threshold value, the saddle fixed point becomes stabilized via a pitchfork bifurcation. We note that this dynamic stabilization is similar to that of the inverted pendulum with a vertically oscillating suspension point. After the dynamic stabilization, the double-well Duffing oscillator behaves as the single-well Duffing oscillator, because the effect of the central potential barrier on the dynamics of the system becomes negligible.

  10. Dynamics of microresonator frequency comb generation: models and stability

    Directory of Open Access Journals (Sweden)

    Hansson Tobias

    2016-06-01

    Full Text Available Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons.

  11. Dynamics of microresonator frequency comb generation: models and stability

    Science.gov (United States)

    Hansson, Tobias; Wabnitz, Stefan

    2016-06-01

    Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons.

  12. Device and method for measuring the dynamic interaction between bodies

    OpenAIRE

    Veltink, Petrus H.

    2008-01-01

    The invention relates to a device for measuring the dynamic interaction, in particular power transfer and work performed, between a first and a second body, in particular during relatively random movements. The device comprises a housing in which at least one kinematic sensor and at least one kinetic sensor is arranged, in addition to processing means for processing the signals from the sensors, and communication means for data exchange with the outside world. The invention also relates to a ...

  13. Enhanced thermal stability of RuO2/polyimide interface for flexible device applications

    Science.gov (United States)

    Music, Denis; Schmidt, Paul; Chang, Keke

    2017-09-01

    We have studied the thermal stability of RuO2/polyimide (Kapton) interface using experimental and theoretical methods. Based on calorimetric and spectroscopic analyses, this inorganic–organic system does not exhibit any enthalpic peaks as well as all bonds in RuO2 and Kapton are preserved up to 500 °C. In addition, large-scale density functional theory based molecular dynamics, carried out in the same temperature range, validates the electronic structure and points out that numerous Ru–C and a few Ru–O covalent/ionic bonds form across the RuO2/Kapton interface. This indicates strong adhesion, but there is no evidence of Kapton degradation upon thermal excitation. Furthermore, RuO2 does not exhibit any interfacial bonds with N and H in Kapton, providing additional evidence for the thermal stability notion. It is suggested that the RuO2/Kapton interface is stable due to aromatic architecture of Kapton. This enhanced thermal stability renders Kapton an appropriate polymeric substrate for RuO2 containing systems in various applications, especially for flexible microelectronic and energy devices.

  14. NONLINEAR THEORY OF DYNAMIC STABILITY FOR LAMINATED COMPOSITE CYLINDRICAL SHELLS

    Institute of Scientific and Technical Information of China (English)

    周承倜; 王列东

    2001-01-01

    Hamilton Principle was uaed to derive the general governing equations of nonlinear dynamic stability for laminated cylindrical shells in which, factors of nonlinear large deflection, transverse shear and longitudinal inertia force were concluded. Equations were solved by variational method. Analysis reveals that under the action of dynamic load,laminated cylindrical shells will fall into a state of parametric resonance and enter into the dynamic unstable region that causes dynamic instability of shells. Laminated shells of three typical composites were computed: i.e. T300/5 208 graphite epoxy E-glass epoxy, and ARALL shells. Results show that all factors will induce important influence for dynamic stability of laminated shells. So, in research of dynamic stability for laminated shells, to consider these factors is important.

  15. 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...... an improved stability with a factor of , but the overhead of computer time is a factor of at least two. The conclusion is that the second-order “Verlet”-algorithm, most commonly used in MD, is superior. It gives the exact dynamics within the limit of the asymptotic expansion and this limit can be estimated...

  16. New steps to improve a-Si:H device stability by design of the interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Martins, R.; Ferreira, I.; Cabrita, A.; Aguas, H.; Silva, V.; Fortunato, E. [New Univ. of Lisbon and CEMOP-UNINOVA, Caparica (Portugal). Faculty of Sciences and Technology

    2001-03-01

    One of the main problems with a-Si:H ''pin'' solar cell devices concerns their stability because of light-soaking effects that degrade device performance. In this communication a method is proposed for improving the performance and stability of devices produced in single-chamber systems. It consists of the controlled ablation of a deposited sacrificial interlayer that functions to absorb or to trap impurities diffused from the doped layer or coming from electrodes or chamber walls. The results achieved lead to an increase of the device efficiency of more than 30% compared with conventional solar cells. (orig.)

  17. SEMICONDUCTOR DEVICES Intrinsic stability of an HBT based on a small signal equivalent circuit model

    Science.gov (United States)

    Yanhu, Chen; Huajun, Shen; Xinyu, Liu; Huijun, Li; Hui, Xu; Ling, Li

    2010-12-01

    Intrinsic stability of the heterojunction bipolar transistor (HBT) was analyzed and discussed based on a small signal equivalent circuit model. The stability factor of the HBT device was derived based on a compact T-type small signal equivalent circuit model of the HBT. The effect of the mainly small signal model parameters of the HBT on the stability of the HBT was thoroughly examined. The discipline of parameter optimum to improve the intrinsic stability of the HBT was achieved. The theoretic analysis results of the stability were also used to explain the experimental results of the stability of the HBT and they were verified by the experimental results.

  18. Dynamics of Electrowetting Droplet Motion in Digital Microfluidics Systems: From Dynamic Saturation to Device Physics

    OpenAIRE

    Weiwei Cui; Menglun Zhang; Xuexin Duan; Wei Pang; Daihua Zhang; Hao Zhang

    2015-01-01

    A quantitative description of the dynamics of droplet motion has been a long-standing concern in electrowetting research. Although many static and dynamic models focusing on droplet motion induced by electrowetting-on-dielectric (EWOD) already exist, some dynamic features do not fit these models well, especially the dynamic saturation phenomenon. In this paper, a dynamic saturation model of droplet motion on the single-plate EWOD device is presented. The phenomenon that droplet velocity is l...

  19. STABILITY ANALYSIS OF THE DYNAMIC INPUT-OUTPUT SYSTEM

    Institute of Scientific and Technical Information of China (English)

    GuoChonghui; TangHuanwen

    2002-01-01

    The dynamic input-output model is well known in economic theory and practice. In this paper, the asymptotic stability and balanced growth solutions of the dynamic input-output system are considered. Under some natural assumptions which do not require the technical coefficient matrix to be indecomposable,it has been proved that the dynamic input-output system is not asymptotically stable and the closed dynamic input-output model has a balanced growth solution.

  20. The stability and dynamic behaviour of fluid-loaded structures

    CSIR Research Space (South Africa)

    Suliman, Ridhwaan

    2015-07-01

    Full Text Available ECCOMAS Young Investigators Conference 6th GACM Colloquium, July 20–23, 2015, Aachen, Germany The stability and dynamic behaviour of fluid-loaded structures R. Suliman, N. Peake Abstract. The deformation of slender elastic structures due...

  1. Development of a novel lung-stabilizing device for VATS procedures.

    Science.gov (United States)

    Muranishi, Yusuke; Sato, Toshihiko; Yutaka, Yojiro; Sakaguchi, Yasuto; Komatsu, Teruya; Yoshizawa, Akihiko; Hirata, Masahiro; Nakamura, Tatsuo; Date, Hiroshi

    2017-03-08

    The use of video-assisted thoracoscopic surgery (VATS) has substantially increased in recent years. These procedures involve the insertion of specialized devices into the thoracic cavity via access ports. However, conventional devices such as cotton-tipped applicators and graspers can limit the field of view and injure the fragile lung tissue. The aim of this study was to develop a novel lung-stabilizing device for VATS that provides a good surgical field of view without causing lung injury. We developed a novel suction-based lung-stabilizing device equipped with three hemispheric 20-mm-diameter silicon suction cups. The utility and safety of the novel device were evaluated using a resected pig lung and canine models. In order to assess potential organ damage arising from the use of the novel device, canine lung parenchyma and pleura were macroscopically and microscopically examined after the device had been continuously applied under negative pressure conditions of -400 or -540 mmHg for 1 h. To assess the utility of the novel device, we performed lobectomies in the resected pig lung and VATS in canine models. The device demonstrated sufficient power to stabilize the lungs and provided a clear field of view during surgery, which enabled us to perform VATS lobectomies more easily than conventional stabilizing forceps. Assessment of the dogs' lungs immediately after detaching the suction-based device revealed no complications such as hemorrhage, air leaks, and bullae formation. Pathological examination after 7 days also showed no substantial damage, except for a small impression in the parenchyma and pleura of the surface layer where the device had contacted the lung tissue. Although further validation studies in clinical settings are required, our study indicates that the novel lung-stabilizing device has potentially useful applications in VATS procedures.

  2. The intrauterine device and its dynamics.

    Science.gov (United States)

    van Os, W A

    1999-01-01

    cancers, such as cervical cancer. (j) Attention to and treatment of dysmenorhea, which in some cases is the first sign of other problems, such as pelvic inflammatory disease, endometriosis, fibroids, endometrial cancer and ectopic pregnancy. (k) Nutritional supplementation to meet the special needs of adolescents, pregnant or lactating women, and women older than 50 years. (1) Services for menopause and other health problems that women encounter as they grow older. (m) Services for adolescents, including family planning and STD prevention and treatment. It shall be clear that many institutions delivering reproductive health services operate significantly below their physical capacity to see clients, and that much of the equipment required for expanding reproductive health services may already be available for use in family planning and other health services. In this context, we would therefore like to discuss the dynamics of IUDs.

  3. A unified proof of dynamic stability of interior ESS for projection dynamics

    NARCIS (Netherlands)

    Joosten, Reinoud A.M.G.; Roorda, Berend

    2011-01-01

    We present a unified proof of dynamic stability for interior evolutionarily stable strategies for two recently introduced projection dynamics using the angle between certain vectors as a Lyapunov function.

  4. Photo-degradation and stabilization effects in operating organic photovoltaic devices by joint photo-current and morphological monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Paci, B.; Generosi, A.; Rossi Albertini, V.; Perfetti, P. [ISM-C.N.R., Area di Ricerca di Tor Vergata, Via del Fosso del Cavaliere 100, 00133 Roma (Italy); de Bettignies, R. [Laboratoire Composants Solaires, CEA INES-RDI, Savoie Technolac, BP 332, 50 avenue du lac Leman, 73377 Le Bourget du Lac (France); Sentein, C. [CEA Saclay, DRT-LITEN-DSEN-GENEC-L2C, F91191 Gif-sur-Yvette (France)

    2008-07-15

    We report on a joint morphological/photoelectrical study of polymer-based photovoltaic (PV) cells in working conditions. The bulk heterojunction devices investigated are based on an active layer of poly(3-hexyl thiophene) blended with methano-fullerene, combining good PV performances with promising stability. The set-up adopted allowed the electrical properties of the device to be directly correlated to the modification of the electrode morphological parameters (thickness and roughness), which were obtained by in situ energy dispersive X-ray reflectometry (EDXR). The results of this joint time-dependent characterization demonstrated how the observed photo-induced oxidation process, limited to the buried electrode interface, is responsible for a fast decrease in the photo-current. The time-resolved measurements allowed to rule out the dynamics of the morphological changes and showed that the interface morphology may be stabilized by annealing treatments, with a significant improvement of the cell efficiency. (author)

  5. Dynamic stabilization of Rayleigh-Taylor instability in ablation fronts

    Directory of Open Access Journals (Sweden)

    Piriz A.R.

    2013-11-01

    Full Text Available Dynamic stabilization of Rayleigh-Taylor instability in an ablation front is studied by considering the simplest possible modulations in the acceleration. Explicit analytical expressions for the instability growth rate and for the boundaries of the stability region are obtained by considering a sequence of Dirac deltas. Besides, general square waves allow for studying the effect of the driving asymmetries on the stability region as well as the optimization process. The essential role of compressibility is phenomenologically addressed in order to find the constraints it imposes on the stability region.

  6. Stabilization of structure-preserving power networks with market dynamics

    CERN Document Server

    Stegink, Tjerk W; van der Schaft, Arjan J

    2016-01-01

    This paper studies the problem of maximizing the social welfare while stabilizing both the physical power network as well as the market dynamics. For the physical power grid a third-order structure-preserving model is considered involving both frequency and voltage dynamics. By applying the primal-dual gradient method to the social welfare problem, a distributed dynamic pricing algorithm in port-Hamiltonian form is obtained. After interconnection with the physical system a closed-loop port-Hamiltonian system of differential-algebraic equations is obtained, whose properties are exploited to prove local asymptotic stability of the optimal points.

  7. Dynamic stability of repulsive-force maglev suspension systems

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Y.; Rote, D.M.; Mulcahy, T.M.; Wang, Z. [and others

    1996-11-01

    This report summarizes the research performed on maglev vehicle dynamic stability at Argonne National Laboratory during the past few years. It also documents both measured and calculated magnetic-force data. Because dynamic instability is not acceptable for any commercial 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 the results with predictions calculated by a nonlinear-dynamics computer code. Instabilities of an electrodynamic-suspension system type vehicle model were obtained by experimental observation and computer simulation of a five-degree-of-freedom maglev vehicle moving on a guideway that consists of a pair of L-shaped aluminum conductors attached to a rotating wheel. The experimental and theoretical analyses developed in this study identify basic stability characteristics and future research needs of maglev systems.

  8. ANALYSIS OF NONLINEAR DYNAMIC STABILITY OF LIQUID-CONVEYING PIPES

    Institute of Scientific and Technical Information of China (English)

    张立翔; 黄文虎

    2002-01-01

    Nonlinearly dynamic stability of flexible liquid-conveying pipe in fluid structure interaction was analyzed by using modal disassembling technique. The effects of Poisson,Junction and Friction couplings in the wave-flowing-vibration system on the pipe dynamic stability were included in the analytical model constituted by four nonlinear differential equations. An analyzing example of cantilevered pipe was done to illustrate the dynamic stability characteristics of the pipe in the full coupling mechanisms, and the phase curves related to the first four modal motions were drawn. The results show that the dynamic stable characteristics of the pipe are very complicated in the complete coupling mechanisms, and the kinds of the singularity points corresponding to the various modal motions are different.

  9. Reduced Order Models for Dynamic Behavior of Elastomer Damping Devices

    Science.gov (United States)

    Morin, B.; Legay, A.; Deü, J.-F.

    2016-09-01

    In the context of passive damping, various mechanical systems from the space industry use elastomer components (shock absorbers, silent blocks, flexible joints...). The material of these devices has frequency, temperature and amplitude dependent characteristics. The associated numerical models, using viscoelastic and hyperelastic constitutive behaviour, may become computationally too expensive during a design process. The aim of this work is to propose efficient reduced viscoelastic models of rubber devices. The first step is to choose an accurate material model that represent the viscoelasticity. The second step is to reduce the rubber device finite element model to a super-element that keeps the frequency dependence. This reduced model is first built by taking into account the fact that the device's interfaces are much more rigid than the rubber core. To make use of this difference, kinematical constraints enforce the rigid body motion of these interfaces reducing the rubber device model to twelve dofs only on the interfaces (three rotations and three translations per face). Then, the superelement is built by using a component mode synthesis method. As an application, the dynamic behavior of a structure supported by four hourglass shaped rubber devices under harmonic loads is analysed to show the efficiency of the proposed approach.

  10. Dielectric Coating Thermal Stabilization During GaAs-Based Laser Fabrication for Improved Device Yield

    Science.gov (United States)

    Connors, Michael K.; Millsapp, Jamal E.; Turner, George W.

    2016-06-01

    The quality and yield of GaAs-based ridge waveguide devices fabricated at MIT Lincoln Laboratory were negatively impacted by the random lot-to-lot appearance of blisters in the front-side contact metal. The blisters signaled compromised adhesion between the front-side contact metal, underlying SiO2 dielectric coating, and semiconductor surface. A thermal-anneal procedure developed for the fabrication of GaAs slab coupled optical waveguide (SCOW) ridge waveguide devices stabilizes the SiO2 dielectric coating by means of outgassing and stress reduction. This process eliminates a primary source of adhesion loss, as well as blister generation, and thereby significantly improves device yield. Stoney's equation was used to analyze stress-induced bow in device wafers fabricated using this stabilization procedure. This analysis suggests that changes in wafer bow contribute to the incidence of metal blisters in SCOW devices.

  11. Dynamic stability of passive dynamic walking on an irregular surface.

    Science.gov (United States)

    Su, Jimmy Li-Shin; Dingwell, Jonathan B

    2007-12-01

    Falls that occur during walking are a significant health problem. One of the greatest impediments to solve this problem is that there is no single obviously "correct" way to quantify walking stability. While many people use variability as a proxy for stability, measures of variability do not quantify how the locomotor system responds to perturbations. The purpose of this study was to determine how changes in walking surface variability affect changes in both locomotor variability and stability. We modified an irreducibly simple model of walking to apply random perturbations that simulated walking over an irregular surface. Because the model's global basin of attraction remained fixed, increasing the amplitude of the applied perturbations directly increased the risk of falling in the model. We generated ten simulations of 300 consecutive strides of walking at each of six perturbation amplitudes ranging from zero (i.e., a smooth continuous surface) up to the maximum level the model could tolerate without falling over. Orbital stability defines how a system responds to small (i.e., "local") perturbations from one cycle to the next and was quantified by calculating the maximum Floquet multipliers for the model. Local stability defines how a system responds to similar perturbations in real time and was quantified by calculating short-term and long-term local exponential rates of divergence for the model. As perturbation amplitudes increased, no changes were seen in orbital stability (r(2)=2.43%; p=0.280) or long-term local instability (r(2)=1.0%; p=0.441). These measures essentially reflected the fact that the model never actually "fell" during any of our simulations. Conversely, the variability of the walker's kinematics increased exponentially (r(2)>or=99.6%; pwalking stability are related to each other and to risk of falling.

  12. Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Joanna Ptasinski

    2014-03-01

    Full Text Available In this work we explore the negative thermo-optic properties of liquid crystal claddings for passive temperature stabilization of silicon photonic integrated circuits. Photonic circuits are playing an increasing role in communications and computing, but they suffer from temperature dependent performance variation. Most existing techniques aimed at compensation of thermal effects rely on power hungry Joule heating. We show that integrating a liquid crystal cladding helps to minimize the effects of a temperature dependent drift. The advantage of liquid crystals lies in their high negative thermo-optic coefficients in addition to low absorption at the infrared wavelengths.

  13. Stability of dynamic response of suspension bridges

    Science.gov (United States)

    Capsoni, Antonio; Ardito, Raffaele; Guerrieri, Andrea

    2017-04-01

    The potential occurrence of internal parametric resonance phenomena has been recently indicated as a potential contributory cause of the appearance of critical dynamic states in long-span suspension bridges. At the same time, suspension bridges, in view of their flexibility, are prone to aeroelastic response, such as vortex shedding, torsional divergence and flutter. In this paper, a non-linear dynamic model of a suspension bridge is devised, with the purpose of providing a first attempt toward a unified framework for the study of aeroelastic and internal resonance instabilities. Inspired by the pioneering work of Herrmann and Hauger, the analyses have been based on a linearized formulation that is able to represent the main structural non-linear effects and the coupling given by aerodynamic forces. The results confirm that the interaction between aeroelastic effects and non-linear internal resonance leads to unstable conditions for wind speeds which can be lower than the critical threshold for standard aeroelastic predictions.

  14. Power system dynamics stability and control

    CERN Document Server

    Padiyar, K R

    2008-01-01

    Modern power systems tend to be very Complex not only due to increasing Demand for quality power, but also on Account of extensive interconnections and increasing dependence on control for optimum utilization for existing resources. A good Knowledge of system dynamics and control is Essential for secure operation of the system. This book is intended to serve the needs of the Student and practicing engineers. A Large number of illustrative examples are included to provide an insight into the application of the theory.

  15. Dynamics of Electrowetting Droplet Motion in Digital Microfluidics Systems: From Dynamic Saturation to Device Physics

    Directory of Open Access Journals (Sweden)

    Weiwei Cui

    2015-06-01

    Full Text Available A quantitative description of the dynamics of droplet motion has been a long-standing concern in electrowetting research. Although many static and dynamic models focusing on droplet motion induced by electrowetting-on-dielectric (EWOD already exist, some dynamic features do not fit these models well, especially the dynamic saturation phenomenon. In this paper, a dynamic saturation model of droplet motion on the single-plate EWOD device is presented. The phenomenon that droplet velocity is limited by a dynamic saturation effect is precisely predicted. Based on this model, the relationship between droplet motion and device physics is extensively discussed. The static saturation phenomenon is treated with a double-layer capacitance electric model, and it is demonstrated as one critical factor determining the dynamics of droplet motion. This work presents the relationship between dynamics of electrowetting induced droplet motion and device physics including device structure, surface material and interface electronics, which helps to better understand electrowetting induced droplet motions and physics of digital microfluidics systems.

  16. Generic Dynamic Environment Perception Using Smart Mobile Devices.

    Science.gov (United States)

    Danescu, Radu; Itu, Razvan; Petrovai, Andra

    2016-10-17

    The driving environment is complex and dynamic, and the attention of the driver is continuously challenged, therefore computer based assistance achieved by processing image and sensor data may increase traffic safety. While active sensors and stereovision have the advantage of obtaining 3D data directly, monocular vision is easy to set up, and can benefit from the increasing computational power of smart mobile devices, and from the fact that almost all of them come with an embedded camera. Several driving assistance application are available for mobile devices, but they are mostly targeted for simple scenarios and a limited range of obstacle shapes and poses. This paper presents a technique for generic, shape independent real-time obstacle detection for mobile devices, based on a dynamic, free form 3D representation of the environment: the particle based occupancy grid. Images acquired in real time from the smart mobile device's camera are processed by removing the perspective effect and segmenting the resulted bird-eye view image to identify candidate obstacle areas, which are then used to update the occupancy grid. The occupancy grid tracked cells are grouped into obstacles depicted as cuboids having position, size, orientation and speed. The easy to set up system is able to reliably detect most obstacles in urban traffic, and its measurement accuracy is comparable to a stereovision system.

  17. Dynamical stability of the Holographic System with Two Competing Orders

    CERN Document Server

    Du, Yiqiang; Tian, Yu; Zhang, Hongbao

    2016-01-01

    We investigate the dynamical stability of the holographic system with two order parameters, which exhibits competition and coexistence of condensations. In the linear regime, we have developed the gauge dependent formalism to calculate the quasi-normal modes by gauge fixing, which turns out be considerably convenient. Furthermore, by giving different Gaussian wave packets as perturbations at the initial time, we numerically evolve the full nonlinear system until it arrives at the final equilibrium state. Our results show that the dynamical stability is consistent with the thermodynamical stability. Interestingly, the dynamical evolution, as well as the quasi-normal modes, shows that the relaxation time of this model is generically much longer than the simplest holographic system. We also find that the late time behavior can be well captured by the lowest lying quasi-normal modes except for the non-vanishing order towards the single ordered phase. To our knowledge, this exception is the first counter example t...

  18. Handbook of electrical power system dynamics modeling, stability, and control

    CERN Document Server

    Eremia, Mircea

    2013-01-01

    Complete guidance for understanding electrical power system dynamics and blackouts This handbook offers a comprehensive and up-to-date treatment of power system dynamics. Addressing the full range of topics, from the fundamentals to the latest technologies in modeling, stability, and control, Handbook of Electrical Power System Dynamics provides engineers with hands-on guidance for understanding the phenomena leading to blackouts so they can design the most appropriate solutions for a cost-effective and reliable operation. Focusing on system dynamics, the book details

  19. Nanodomain stabilization dynamics in plasma membranes of biological cells

    Science.gov (United States)

    Das, Tamal; Maiti, Tapas K.; Chakraborty, Suman

    2011-02-01

    We discover that a synergistically amplifying role of stabilizing membrane proteins and continuous lipid recycling can explain the physics governing the stability, polydispersity, and dynamics of lipid raft domains in plasma membranes of biological cells. We establish the conjecture using a generalized order parameter based on theoretical formalism, endorsed by detailed scaling arguments and domain mapping. Quantitative agreements with morphological distributions of raft complexes, as obtained from Förster resonance energy transfer based visualization, support the present theoretical conjecture.

  20. 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.

  1. Generalized Extreme Value distribution parameters as dynamical indicators of Stability

    CERN Document Server

    Faranda, Davide; Turchetti, Giorgio; Vaienti, Sandro

    2011-01-01

    We introduce a new dynamical indicator of stability based on the Extreme Value statistics showing that it provides an insight on the local stability properties of dynamical systems. The indicator perform faster than other based on the iteration of the tangent map since it requires only the evolution of the original systems and, in the chaotic regions, gives further information about the information dimension of the attractor. A numerical validation of the method is presented through the analysis of the motions in a Standard map.

  2. Impulsive dynamics and stabilization of a single wheel robot

    Institute of Scientific and Technical Information of China (English)

    Ou Yongsheng; Wu Xinyu; Xu Yangsheng

    2011-01-01

    The impulsive motion of a dynamically stabilized robot-Gyrover, which is a single-wheel gyroscopically stabilized robot is studied. A method based on the D' Alembert-Lagrange principle is proposed to develop the impulsive dynamic model of the single wheel robot. This method that can be used to find ways to investigate a single wheel mobile robot rolling on a rough terrain is tested using the experimental platform Gyrover. The conditions of falling over without actuators are addressed. Simulations that validate the analysis are provided as well.

  3. DYNAMICAL STABILITY OF VISCOELASTIC COLUMN WITH FRACTIONAL DERIVATIVE CONSTITUTIVE RELATION

    Institute of Scientific and Technical Information of China (English)

    李根国; 朱正佑; 程昌钧

    2001-01-01

    The dynamic stability of simple supported viscoelastic column, subjected to a periodic axial force, is investigated. The viscoelastic material was assumed to obey the fractional derivative constitutive relation. The governing equation of motion was derived as a weakly singular Volterra integro-partial-differential equation, and it was simplified into a weakly singular Volterra integro-ordinary-differential equation by the Galerkin method. In terms of the averaging method, the dynamical stability was analyzed. A new numerical method is proposed to avoid storing all history data. Numerical examples are presented and the numerical results agree with the analytical ones.

  4. ISO 12189 standard for the preclinical evaluation of posterior spinal stabilization devices--II: A parametric comparative study.

    Science.gov (United States)

    La Barbera, Luigi; Costa, Francesco; Villa, Tomaso

    2016-02-01

    The International Standardization Organization (ISO) 12189 standard was recently introduced to preclinically evaluate and compare the mechanical properties of posterior stabilization devices. This scenario presents some new significant steps ahead over the vertebrectomy model recommended by American Society for Testing and Materials (ASTM) F1717 standard: the modular anterior support allows for describing a closer scenario to the effective clinical use as well as to test very flexible and dynamic posterior stabilization devices. Despite these significant advantages, ISO 12189 received little attention in the literature. Anatomical parameters depending on the spinal level were compared to the published data or original measurements on biplanar stereoradiography on 13 patients. Other mechanical variables, describing the test set-up design, were considered and all parameters were investigated using a numerical parametric finite element model. Stress values were calculated by also considering their worst-case combination. The standard set-up represents quite well the anatomy of an instrumented average thoracolumbar segment. The parametric comparative analysis demonstrates a significant (even beyond +350%) maximum increase in the stress on the device, compared to the standard currently in use. The anterior support stiffness plays the most detrimental effect (maximum stress increases up to 396%). The initial precompression step has an important role in determining the final stress values achieved at peak load (up to +76%). Moreover, when combining these two contributions, an even higher stress increase may be achieved (up to 473%). Despite the other anatomical parameters playing a secondary role, their worst-case combination demonstrates that a device could potentially undergo higher stresses than those reached according to standard suggestions (maximum increase of 22.4% at L1). Any user/designer should be aware of these effects when using ISO 12189 standard for the

  5. Design and Analyze a New Measuring Lift Device for Fin Stabilizers Using Stiffness Matrix of Euler-Bernoulli Beam.

    Science.gov (United States)

    Liang, Lihua; Sun, Mingxiao; Shi, Hongyu; Luan, Tiantian

    2017-01-01

    Fin-angle feedback control is usually used in conventional fin stabilizers, and its actual anti-rolling effect is difficult to reach theoretical design requirements. Primarily, lift of control torque is a theoretical value calculated by static hydrodynamic characteristics of fin. However, hydrodynamic characteristics of fin are dynamic while fin is moving in waves. As a result, there is a large deviation between actual value and theoretical value of lift. Firstly, the reasons of deviation are analyzed theoretically, which could avoid a variety of interference factors and complex theoretical derivations. Secondly, a new device is designed for direct measurement of actual lift, which is composed of fin-shaft combined mechanism and sensors. This new device can make fin-shaft not only be the basic function of rotating fin, but also detect actual lift. Through analysis using stiffness matrix of Euler-Bernoulli beam, displacement of shaft-core end is measured instead of lift which is difficult to measure. Then quantitative relationship between lift and displacement is defined. Three main factors are analyzed with quantitative relationship. What is more, two installation modes of sensors and a removable shaft-end cover are proposed according to hydrodynamic characteristics of fin. Thus the new device contributes to maintenance and measurement. Lastly, the effectiveness and accuracy of device are verified by contrasting calculation and simulation on the basis of actual design parameters. And the new measuring lift method can be proved to be effective through experiments. The new device is achieved from conventional fin stabilizers. Accordingly, the reliability of original equipment is inherited. The alteration of fin stabilizers is minor, which is suitable for engineering application. In addition, the flexural properties of fin-shaft are digitized with analysis of stiffness matrix. This method provides theoretical support for engineering application by carrying out finite

  6. Design and Analyze a New Measuring Lift Device for Fin Stabilizers Using Stiffness Matrix of Euler-Bernoulli Beam

    Science.gov (United States)

    Liang, Lihua; Sun, Mingxiao; Shi, Hongyu; Luan, Tiantian

    2017-01-01

    Fin-angle feedback control is usually used in conventional fin stabilizers, and its actual anti-rolling effect is difficult to reach theoretical design requirements. Primarily, lift of control torque is a theoretical value calculated by static hydrodynamic characteristics of fin. However, hydrodynamic characteristics of fin are dynamic while fin is moving in waves. As a result, there is a large deviation between actual value and theoretical value of lift. Firstly, the reasons of deviation are analyzed theoretically, which could avoid a variety of interference factors and complex theoretical derivations. Secondly, a new device is designed for direct measurement of actual lift, which is composed of fin-shaft combined mechanism and sensors. This new device can make fin-shaft not only be the basic function of rotating fin, but also detect actual lift. Through analysis using stiffness matrix of Euler-Bernoulli beam, displacement of shaft-core end is measured instead of lift which is difficult to measure. Then quantitative relationship between lift and displacement is defined. Three main factors are analyzed with quantitative relationship. What is more, two installation modes of sensors and a removable shaft-end cover are proposed according to hydrodynamic characteristics of fin. Thus the new device contributes to maintenance and measurement. Lastly, the effectiveness and accuracy of device are verified by contrasting calculation and simulation on the basis of actual design parameters. And the new measuring lift method can be proved to be effective through experiments. The new device is achieved from conventional fin stabilizers. Accordingly, the reliability of original equipment is inherited. The alteration of fin stabilizers is minor, which is suitable for engineering application. In addition, the flexural properties of fin-shaft are digitized with analysis of stiffness matrix. This method provides theoretical support for engineering application by carrying out finite

  7. Computational Methods for Dynamic Stability and Control Derivatives

    Science.gov (United States)

    Green, Lawrence L.; Spence, Angela M.; Murphy, Patrick C.

    2004-01-01

    Force and moment measurements from an F-16XL during forced pitch oscillation tests result in dynamic stability derivatives, which are measured in combinations. Initial computational simulations of the motions and combined derivatives are attempted via a low-order, time-dependent panel method computational fluid dynamics code. The code dynamics are shown to be highly questionable for this application and the chosen configuration. However, three methods to computationally separate such combined dynamic stability derivatives are proposed. One of the separation techniques is demonstrated on the measured forced pitch oscillation data. Extensions of the separation techniques to yawing and rolling motions are discussed. In addition, the possibility of considering the angles of attack and sideslip state vector elements as distributed quantities, rather than point quantities, is introduced.

  8. Innovation networking between stability and political dynamics

    DEFF Research Database (Denmark)

    Koch, Christian

    2004-01-01

    of the contribution is to challenge and transcend these notions and develop an understanding of innovation networks as an interplay between stable and dynamic elements, where political processes in innovation are much more than a disruptive and even a counterproductive feature. It reviews the growing number......This contribution views innovation as a social activity of building networks, using software product development in multicompany alliances and networks as example. Innovation networks are frequently understood as quite stable arrangements characterised by high trust among the participants. The aim...... of studies that highlight the political aspect of innovation. The paper reports on a study of innovation processes conducted within the EU—TSER-programme and a study made under the banner of management of technology. Intensive field studies in two constellations of enterprises were carried out. One...

  9. Role of reflex dynamics in spinal stability: intrinsic muscle stiffness alone is insufficient for stability.

    Science.gov (United States)

    Moorhouse, Kevin M; Granata, Kevin P

    2007-01-01

    Spinal stability is related to both the intrinsic stiffness of active muscle as well as neuromuscular reflex response. However, existing analyses of spinal stability ignore the role of the reflex response, focusing solely on the intrinsic muscle stiffness associated with voluntary activation patterns in the torso musculature. The goal of this study was to empirically characterize the role of reflex components of spinal stability during voluntary trunk extension exertions. Pseudorandom position perturbations of the torso and associated driving forces were recorded in 11 healthy adults. Nonlinear systems-identification analyses of the measured data provided an estimate of total systems dynamics that explained 81% of the movement variability. Proportional intrinsic response was less than zero in more than 60% of the trials, e.g. mean value of P(INT) during the 20% maximum voluntary exertion trunk extension exertions -415+/-354N/m. The negative value indicated that the intrinsic muscle stiffness was not sufficient to stabilize the spine without reflex response. Reflexes accounted for 42% of the total stabilizing trunk stiffness. Both intrinsic and reflex components of stiffness increased significantly with trunk extension effort. Results reveal that reflex dynamics are a necessary component in the stabilizing control of spinal stability.

  10. Dynamic flight stability of a hovering model dragonfly.

    Science.gov (United States)

    Liang, Bin; Sun, Mao

    2014-05-07

    The longitudinal dynamic flight stability of a model dragonfly at hovering flight is studied, using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigenvector analysis for solving the equations of motion. Three natural modes of motion are identified for the hovering flight: one unstable oscillatory mode, one stable fast subsidence mode and one stable slow subsidence mode. The flight is dynamically unstable owing to the unstable oscillatory mode. The instability is caused by a pitch-moment derivative with respect to horizontal velocity. The damping force and moment derivatives (with respect to horizontal and vertical velocities and pitch-rotational velocity, respectively) weaken the instability considerably. The aerodynamic interaction between the forewing and the hindwing does not have significant effect on the stability properties. The dragonfly has similar stability derivatives, hence stability properties, to that of a one-wing-pair insect at normal hovering, but there are differences in how the derivatives are produced because of the highly inclined stroke plane of the dragonfly.

  11. Stability of Surface Nanobubbles: A Molecular Dynamics Study

    NARCIS (Netherlands)

    Maheshwari, Shantanu; Hoef, van der Martin; Zhang, Xuehua; Lohse, Detlef

    2016-01-01

    The stability and growth or dissolution of a single surface nanobubble on a chemically patterned surface are studied by molecular dynamics simulations of binary mixtures consisting of Lennard-Jones (LJ) particles. Our simulations reveal how pinning of the three-phase contact line on the surface can

  12. EXPONENTIAL STABILITY OF INTERVAL DYNAMICAL SYSTEM WITH MULTIDELAY

    Institute of Scientific and Technical Information of China (English)

    孙继涛; 张银萍; 刘永清; 邓飞其

    2002-01-01

    Using the matrix measure and delay differential inequality, the sufficient conditions were obtained for exponential stability of interval dynamical system with multidelay. These conditions are an improvement and extension of the results achieved in earlier papers presented by LIAO, LIU, ZHANG, SUN, et al.

  13. Dynamic Transfer Schemes and Stability of International Climate Coalitions

    NARCIS (Netherlands)

    Nagashima, M.N.; Dellink, R.B.; Ierland, van E.C.

    2006-01-01

    This paper examines the formation and stability of coalitions in international climate agreements with a combined game-theoretic and integrated assessment model. The empirical model comprises twelve regions and investigates partial coalition formation in a one-shot cartel game. We argue that a dynam

  14. Exponential stability of dynamic equations on time scales

    Directory of Open Access Journals (Sweden)

    Raffoul Youssef N

    2005-01-01

    Full Text Available We investigate the exponential stability of the zero solution to a system of dynamic equations on time scales. We do this by defining appropriate Lyapunov-type functions and then formulate certain inequalities on these functions. Several examples are given.

  15. Differentiable dynamical systems an introduction to structural stability and hyperbolicity

    CERN Document Server

    Wen, Lan

    2016-01-01

    This is a graduate text in differentiable dynamical systems. It focuses on structural stability and hyperbolicity, a topic that is central to the field. Starting with the basic concepts of dynamical systems, analyzing the historic systems of the Smale horseshoe, Anosov toral automorphisms, and the solenoid attractor, the book develops the hyperbolic theory first for hyperbolic fixed points and then for general hyperbolic sets. The problems of stable manifolds, structural stability, and shadowing property are investigated, which lead to a highlight of the book, the \\Omega-stability theorem of Smale. While the content is rather standard, a key objective of the book is to present a thorough treatment for some tough material that has remained an obstacle to teaching and learning the subject matter. The treatment is straightforward and hence could be particularly suitable for self-study. Selected solutions are available electronically for instructors only. Please send email to textbooks@ams.org for more informatio...

  16. Adaptive steady-state stabilization for nonlinear dynamical systems

    Science.gov (United States)

    Braun, David J.

    2008-07-01

    By means of LaSalle’s invariance principle, we propose an adaptive controller with the aim of stabilizing an unstable steady state for a wide class of nonlinear dynamical systems. The control technique does not require analytical knowledge of the system dynamics and operates without any explicit knowledge of the desired steady-state position. The control input is achieved using only system states with no computer analysis of the dynamics. The proposed strategy is tested on Lorentz, van der Pol, and pendulum equations.

  17. Multiple-node basin stability in complex dynamical networks

    Science.gov (United States)

    Mitra, Chiranjit; Choudhary, Anshul; Sinha, Sudeshna; Kurths, Jürgen; Donner, Reik V.

    2017-03-01

    Dynamical entities interacting with each other on complex networks often exhibit multistability. The stability of a desired steady regime (e.g., a synchronized state) to large perturbations is critical in the operation of many real-world networked dynamical systems such as ecosystems, power grids, the human brain, etc. This necessitates the development of appropriate quantifiers of stability of multiple stable states of such systems. Motivated by the concept of basin stability (BS) [P. J. Menck et al., Nat. Phys. 9, 89 (2013), 10.1038/nphys2516], we propose here the general framework of multiple-node basin stability for gauging the global stability and robustness of networked dynamical systems in response to nonlocal perturbations simultaneously affecting multiple nodes of a system. The framework of multiple-node BS provides an estimate of the critical number of nodes that, when simultaneously perturbed, significantly reduce the capacity of the system to return to the desired stable state. Further, this methodology can be applied to estimate the minimum number of nodes of the network to be controlled or safeguarded from external perturbations to ensure proper operation of the system. Multiple-node BS can also be utilized for probing the influence of spatially localized perturbations or targeted attacks to specific parts of a network. We demonstrate the potential of multiple-node BS in assessing the stability of the synchronized state in a deterministic scale-free network of Rössler oscillators and a conceptual model of the power grid of the United Kingdom with second-order Kuramoto-type nodal dynamics.

  18. Comparison of the load-sharing characteristics between pedicle-based dynamic and rigid rod devices

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Yoon-Ho [Korea Orthopedics and Rehabilitation Engineering Center, Incheon 403712 (Korea, Republic of); Chen, W-M [Division of Bioengineering, National University of Singapore, Singapore 117576 (Singapore); Lee, Kwon-Yong [Department of Mechanical Engineering, Sejong University, Seoul 143747 (Korea, Republic of); Park, Kyung-Woo [Department of Neurosurgery, Kwang-Hye Spine Hospital, Seoul 135280 (Korea, Republic of); Lee, Sung-Jae [Department of Biomedical Engineering, Inje University, Gimhae 621749 (Korea, Republic of)], E-mail: sjl@bme.inje.ac.kr

    2008-12-01

    Recently, numerous types of posterior dynamic stabilization (PDS) devices have been introduced as an alternative to the fusion devices for the surgical treatment of degenerative lumbar spine. It is hypothesized that the use of 'compliant' materials such as Nitinol (Ni-Ti alloy, elastic modulus = 75 GPa) or polyether-etherketone (PEEK, elastic modulus = 3.2 GPa) in PDS can restore stability of the lumbar spine without adverse stress-shielding effects that have often been found with 'rigid' fusion devices made of 'rigid' Ti alloys (elastic modulus = 114 GPa). Previous studies have shown that suitably designed PDS devices made of more compliant material may be able to help retain kinematic behavior of the normal spine with optimal load sharing between the anterior and posterior spinal elements. However, only a few studies on their biomechanical efficacies are available. In this study, we conducted a finite-element (FE) study to investigate changes in load-sharing characteristics of PDS devices. The implanted models were constructed after modifying the previously validated intact model of L3-4 spine. Posterior lumbar fusion with three different types of pedicle screw systems was simulated: a conventional rigid fixation system (Ti6Al4V, {phi} = 6.0 mm) and two kinds of PDS devices (one with Nitinol rod with a three-coiled turn manner, {phi} = 4.0 mm; the other with PEEK rod with a uniform cylindrical shape, {phi} = 6.0 mm). To simulate the load on the lumbar spine in a neutral posture, an axial compressive load (400 N) was applied. Subsequently, the changes in load-sharing characteristics and stresses were investigated. When the compressive load was applied on the implanted models (Nitinol rod, PEEK rod, Ti-alloy rod), the predicted axial compressive loads transmitted through the devices were 141.8 N, 109.8 N and 266.8 N, respectively. Axial forces across the PDS devices (Nitinol rod, PEEK rod) and rigid system (Ti-alloy rod) with facet

  19. The validity and reliability of a dynamic neuromuscular stabilization-heel sliding test for core stability.

    Science.gov (United States)

    Cha, Young Joo; Lee, Jae Jin; Kim, Do Hyun; You, Joshua Sung H

    2017-07-21

    Core stabilization plays an important role in the regulation of postural stability. To overcome shortcomings associated with pain and severe core instability during conventional core stabilization tests, we recently developed the dynamic neuromuscular stabilization-based heel sliding (DNS-HS) test. The purpose of this study was to establish the criterion validity and test-retest reliability of the novel DNS-HS test. Twenty young adults with core instability completed both the bilateral straight leg lowering test (BSLLT) and DNS-HS test for the criterion validity study and repeated the DNS-HS test for the test-retest reliability study. Criterion validity was determined by comparing hip joint angle data that were obtained from BSLLT and DNS-HS measures. The test-retest reliability was determined by comparing hip joint angle data. Criterion validity was (ICC2,3) = 0.700 (pcore stability measures. Test-retest reliability was (ICC3,3) = 0.953 (pcore stability measures. Test-retest reliability data suggests that DNS-HS core stability was a reliable test for core stability. Clinically, the DNS-HS test is useful to objectively quantify core instability and allow early detection and evaluation.

  20. Augmenting retention and stability of an occlusal device for a partially dentate patient using existing extracoronal attachments: a clinical report.

    Science.gov (United States)

    Al-Rowaieh, Saleh A

    2011-04-01

    Occlusal devices are a valid treatment modality in certain clinical situations. For an occlusal device to be effective, sufficient retention and stability should be derived from coverage of the occlusal and incisal surfaces of the teeth. In the absence of most or all of the posterior teeth, the effectiveness of the device could become compromised as the incisal portions of the anterior teeth are typically not conducive to adequately retaining and stabilizing the device. This clinical report describes an approach to improving the retention and stability of an occlusal device for a patient with shortened dental arches by use of the patient's existing extracoronal attachments.

  1. Robust adaptive output stabilization using dynamic normalizing signal

    Institute of Scientific and Technical Information of China (English)

    Haixia SU; Xuejun XIE; Haikuan LIU

    2007-01-01

    For a class of nonlinear systems with dynamic uncertainties,robust adaptive stabilization problem is considered in this paper.Firstly,by introducing an observer,an augmented system is obtained.Based on the system,we construct an exp-ISpS Lyapunov function for the unmodeled dynamics,prove that the unmodeled dynamics is exp-ISpS,and then obtain a dynamic normalizing signal to counteract the dynamic disturbances.By the backstepping technique,an adaptive controller is given,it is proved that all the signals in the adaptive control system are globally uniformly ultimately bounded,and the output can be regulated to the origin with any prescribed accuracy.A simulation example further demonstrates the efficiency of the control scheme.

  2. Stability theory for dynamic equations on time scales

    CERN Document Server

    Martynyuk, Anatoly A

    2016-01-01

    This monograph is a first in the world to present three approaches for stability analysis of solutions of dynamic equations. The first approach is based on the application of dynamic integral inequalities and the fundamental matrix of solutions of linear approximation of dynamic equations. The second is based on the generalization of the direct Lyapunovs method for equations on time scales, using scalar, vector and matrix-valued auxiliary functions. The third approach is the application of auxiliary functions (scalar, vector, or matrix-valued ones) in combination with differential dynamic inequalities. This is an alternative comparison method, developed for time continuous and time discrete systems. In recent decades, automatic control theory in the study of air- and spacecraft dynamics and in other areas of modern applied mathematics has encountered problems in the analysis of the behavior of solutions of time continuous-discrete linear and/or nonlinear equations of perturbed motion. In the book “Men of Ma...

  3. Dynamical stability and evolution of the discs of Sc galaxies

    CERN Document Server

    Fuchs, B

    1997-01-01

    We examine the local stability of galactic discs against axisymmetric density perturbations with special attention to the different dynamics of the stellar and gaseous components. In particular the discs of the Milky Way and of NGC 6946 are studied. The Milky Way is shown to be stable, whereas the inner parts of NGC 6946, a typical Sc galaxy from the Kennicutt (1989) sample, are dynamically unstable. The ensuing dynamical evolution of the composite disc is studied by numerical simulations. The evolution is so fierce that the stellar disc heats up dynamically on a short time scale to such a degree, which seems to contradict the morphological appearance of the galaxy. The star formation rate required to cool the disc dynamically is estimated. Even if the star formation rate in NGC 6946 is at present high enough to meet this requirement, it is argued that the discs of Sc galaxies cannot sustain such a high star formation rate for longer periods.

  4. Design and Validation of a Low-Cost Portable Device to Quantify Postural Stability

    Science.gov (United States)

    Zhu, Yong

    2017-01-01

    Measurement of the displacement of the center-of-pressure (COP) is an important tool used in biomechanics to assess postural stability and human balance. The goal of this research was to design and validate a low-cost portable device that can offer a quick indication of the state of postural stability and human balance related conditions. Approximate entropy (ApEn) values reflecting the amount of irregularity hiding in COP oscillations were used to calculate the index. The prototype adopted a portable design using the measurements of the load cells located at the four corners of a low-cost force platform. The test subject was asked to stand on the device in a quiet, normal, upright stance for 30 s with eyes open and subsequently for 30 s with eyes closed. Based on the COP displacement signals, the ApEn values were calculated. The results indicated that the prototype device was capable of capturing the increase in regularity of postural control in the visual-deprivation conditions. It was also able to decipher the subtle postural control differences along anterior–posterior and medial–lateral directions. The data analysis demonstrated that the prototype would enable the quantification of postural stability and thus provide a low-cost portable device to assess many conditions related to postural stability and human balance such as aging and pathologies. PMID:28335461

  5. Design and Validation of a Low-Cost Portable Device to Quantify Postural Stability

    Directory of Open Access Journals (Sweden)

    Yong Zhu

    2017-03-01

    Full Text Available Measurement of the displacement of the center-of-pressure (COP is an important tool used in biomechanics to assess postural stability and human balance. The goal of this research was to design and validate a low-cost portable device that can offer a quick indication of the state of postural stability and human balance related conditions. Approximate entropy (ApEn values reflecting the amount of irregularity hiding in COP oscillations were used to calculate the index. The prototype adopted a portable design using the measurements of the load cells located at the four corners of a low-cost force platform. The test subject was asked to stand on the device in a quiet, normal, upright stance for 30 s with eyes open and subsequently for 30 s with eyes closed. Based on the COP displacement signals, the ApEn values were calculated. The results indicated that the prototype device was capable of capturing the increase in regularity of postural control in the visual-deprivation conditions. It was also able to decipher the subtle postural control differences along anterior–posterior and medial–lateral directions. The data analysis demonstrated that the prototype would enable the quantification of postural stability and thus provide a low-cost portable device to assess many conditions related to postural stability and human balance such as aging and pathologies.

  6. Optical Stabilizer Based on Optical Bistable Devices with All-Fibre Construction

    Institute of Scientific and Technical Information of China (English)

    LI Cheng; YE Hong-An; ZHAO Xue-Zeng; YANG Jiu-Ru; ZHANG Xin-Ming; LU Guo-Hui

    2004-01-01

    @@ We propose a fibre optical stabilizer constituted by a photoelectric-hybrid optical bistable device in which fibre Bragg grating is used as a light intensity modulator. The intensity noise-reducing ability is well improved through the method by employing two feed signals. As a result, the light intensity variation can be reduced to ~ 1/64.

  7. Influence of caster diameter on the static and dynamic forward stability of occupied wheelchairs.

    Science.gov (United States)

    Kirby, R L; McLean, A D; Eastwood, B J

    1992-01-01

    The hypothesis that the static and dynamic forward stability of an occupied wheelchair would increase as a function of the caster diameter was tested in 20 able-bodied subjects. A device was attached to the wheelchair frame so that casters with different diameters could be used. With platform testing of static stability, the occupied wheelchair equipped with casters with diameters of 10.2, 20.3, 25.4, and 33.0cm, tipped at mean (+/- 1SD) angles of 23.8 degrees (+/- 1.3 degrees), 25.2 degrees (+/- 1.4 degrees), 26.1 degrees (+/- 1.4 degrees), and 28.2 degrees (+/- 1.9 degrees), respectively. The relationship between static stability (y, in degrees) and caster diameter (x, in cm) can be expressed by the equation y = 23.5-.0196 chi + .00484 x2 (p = .0001). Dynamic stability was tested by having subjects descend a 5 degree ramp, by gravity alone, from progressively farther up the ramp until a full forward tip occurred (footrests contacted the floor) when the wheelchair struck a 5-cm-high obstruction with sufficient speed. The mean tipping speeds for the dynamic tests were .85 (+/- .08), .85 (+/- .08), .89 (+/-.07), and 1.04 (+/- .14) m/sec for the wheelchair fitted with the caster diameters ranging from smallest to largest, respectively. The relationship between dynamic stability (y, tipping speed in m/sec) and caster diameter (chi, in cm) can be expressed by the equation y = .788 + .0139 chi-.00110 chi 2 + .0000276 chi 3 (p = .0001). The relationship between caster diameter and forward wheelchair stability should be considered in wheelchair design and prescription.

  8. Note: Optical trigger device with sub-picosecond timing jitter and stability

    Science.gov (United States)

    Kodet, Jan; Prochazka, Ivan

    2012-03-01

    We are presenting the design, construction, and overall performance of the optical trigger device. This device generates an electrical signal synchronously to the detected ultra-short optical pulse. The device was designed for application in satellite laser ranging and laser time transfer experiments, time correlated photon counting and similar experiments, where picosecond timing resolution and detection delay stability are required. It consists of the ultrafast optical detector, signal discriminator, output pulse forming circuit, and output driver circuits. It was constructed as a single compact device to optimize their matching and maintain stability. The detector consists of an avalanche photodiode--both silicon and germanium types may be used to cover the wavelength range of 350-1550 nm. The analogue signal of this photodiode is sensed by the ultrafast comparator with 8 GHz bandwidth. The ps clock distribution circuit is used to generate the fast rise/fall time output pulses of pre-set length. The trigger device timing performance is excellent: the random component of the timing jitter is typically 880 fs, the temperature dependence of the detection delay was measured to be 370 fs/K. The systematic error contribution depends on the laser used and its stability. The sub-ps values have been obtained for various laser sources.

  9. Dynamical behavior and Jacobi stability analysis of wound strings

    Energy Technology Data Exchange (ETDEWEB)

    Lake, Matthew J. [Naresuan University, The Institute for Fundamental Study, ' ' The Tah Poe Academia Institute' ' , Phitsanulok (Thailand); Thailand Center of Excellence in Physics, Ministry of Education, Bangkok (Thailand); Harko, Tiberiu [Babes-Bolyai University, Department of Physics, Cluj-Napoca (Romania); University College London, Department of Mathematics, London (United Kingdom)

    2016-06-15

    We numerically solve the equations of motion (EOM) for two models of circular cosmic string loops with windings in a simply connected internal space. Since the windings cannot be topologically stabilized, stability must be achieved (if at all) dynamically. As toy models for realistic compactifications, we consider windings on a small section of R{sup 2}, which is valid as an approximation to any simply connected internal manifold if the winding radius is sufficiently small, and windings on an S{sup 2} of constant radius R. We then use Kosambi-Cartan-Chern (KCC) theory to analyze the Jacobi stability of the string equations and determine bounds on the physical parameters that ensure dynamical stability of the windings. We find that, for the same initial conditions, the curvature and topology of the internal space have nontrivial effects on the microscopic behavior of the string in the higher dimensions, but that the macroscopic behavior is remarkably insensitive to the details of the motion in the compact space. This suggests that higher-dimensional signatures may be extremely difficult to detect in the effective (3+1)-dimensional dynamics of strings compactified on an internal space, even if configurations with nontrivial windings persist over long time periods. (orig.)

  10. Maximum Allowable Dynamic Load of Mobile Manipulators with Stability Consideration

    Directory of Open Access Journals (Sweden)

    Heidary H. R.

    2015-09-01

    Full Text Available High payload to mass ratio is one of the advantages of mobile robot manipulators. In this paper, a general formula for finding the maximum allowable dynamic load (MADL of wheeled mobile robot is presented. Mobile manipulators operating in field environments will be required to manipulate large loads, and to perform such tasks on uneven terrain, which may cause the system to reach dangerous tip-over instability. Therefore, the method is expanded for finding the MADL of mobile manipulators with stability consideration. Moment-Height Stability (MHS criterion is used as an index for the system stability. Full dynamic model of wheeled mobile base and mounted manipulator is considered with respect to the dynamic of non-holonomic constraint. Then, a method for determination of the maximum allowable loads is described, subject to actuator constraints and by imposing the stability limitation as a new constraint. The actuator torque constraint is applied by using a speed-torque characteristics curve of a typical DC motor. In order to verify the effectiveness of the presented algorithm, several simulation studies considering a two-link planar manipulator, mounted on a mobile base are presented and the results are discussed.

  11. Physical phenomena in efficiency and stability of organic light-emitting devices

    Science.gov (United States)

    Luo, Yichun

    2007-12-01

    Operational stability and luminescence efficiency of organic light-emitting devices (OLEDs) continue to be the most important issues for a wide commercialization of this technology. Thus, the main theme of this sandwich-style thesis is to investigate physical phenomena related to the operational stability and luminescence efficiency of OLEDs, and to eventually improve device performances by using various device structures and power driving schemes. Operational stability of OLEDs is generally governed by intrinsic degradation. Aimed at a comprehensive description of intrinsic degradation mechanism, a number of degradation models have been reported in literature. In these models, the intrinsic degradation is generally attributed to the role of positive charges (holes) in decreasing the luminescence efficiency during device operation. In this thesis, we report a further investigation that leads to the discovery that excessive injection of negative charges (electrons) can also induce significant degradation of devices. The rate of degradation is found to be determined primarily by the density of excessive charges (whether they are holes or electrons) in the vicinity of the emitting layer, where the higher the density, the faster the device degradation. In view of the above understanding of degradation mechanism, we developed a hole-injection-tunable-anode-buffer-layer (HITABL) at the anode contact of the devices to improve device stability. By using the HITABL, one can make the necessary diminutive adjustments to the hole injection of a device and achieve a proper charge balance, and thus significantly improve the operational stability of the devices. In terms of luminescence efficiency, the effects of electric field and electric current (hole current or electron current) on luminescence efficiency of a fluorescent dye doped emitting layer are studied, respectively. Results show that a doped emitting layer demonstrates a smaller decrease in luminescence efficiency than

  12. On the dynamics of turbulent transport near marginal stability

    Energy Technology Data Exchange (ETDEWEB)

    Diamond, P.H. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics]|[General Atomics, San Diego, CA (United States); Hahm, T.S. [Princeton Univ., NJ (United States). Plasma Physics Lab.

    1995-03-01

    A general methodology for describing the dynamics of transport near marginal stability is formulated. Marginal stability is a special case of the more general phenomenon of self-organized criticality. Simple, one field models of the dynamics of tokamak plasma self-organized criticality have been constructed, and include relevant features such as sheared mean flow and transport bifurcations. In such models, slow mode (i.e. large scale, low frequency transport events) correlation times determine the behavior of transport dynamics near marginal stability. To illustrate this, impulse response scaling exponents (z) and turbulent diffusivities (D) have been calculated for the minimal (Burgers) and sheared flow models. For the minimal model, z = 1 (indicating ballastic propagation) and D {approximately}(S{sub 0}{sup 2}){sup 1/3}, where S{sub 0}{sup 2} is the noise strength. With an identically structured noise spectrum and flow with shearing rate exceeding the ambient decorrelation rate for the largest scale transport events, diffusion is recovered with z = 2 and D {approximately} (S{sub 0}{sup 2}){sup 3/5}. This indicates a qualitative change in the dynamics, as well as a reduction in losses. These results are consistent with recent findings from {rho} scaling scans. Several tokamak transport experiments are suggested.

  13. Stabilization of computational procedures for constrained dynamical systems

    Science.gov (United States)

    Park, K. C.; Chiou, J. C.

    1988-01-01

    A new stabilization method of treating constraints in multibody dynamical systems is presented. By tailoring a penalty form of the constraint equations, the method achieves stabilization without artificial damping and yields a companion matrix differential equation for the constraint forces; hence, the constraint forces are obtained by integrating the companion differential equation for the constraint forces in time. A principal feature of the method is that the errors committed in each constraint condition decay with its corresponding characteristic time scale associated with its constraint force. Numerical experiments indicate that the method yields a marked improvement over existing techniques.

  14. Dynamics and Adaptive Control for Stability Recovery of Damaged Aircraft

    Science.gov (United States)

    Nguyen, Nhan; Krishnakumar, Kalmanje; Kaneshige, John; Nespeca, Pascal

    2006-01-01

    This paper presents a recent study of a damaged generic transport model as part of a NASA research project to investigate adaptive control methods for stability recovery of damaged aircraft operating in off-nominal flight conditions under damage and or failures. Aerodynamic modeling of damage effects is performed using an aerodynamic code to assess changes in the stability and control derivatives of a generic transport aircraft. Certain types of damage such as damage to one of the wings or horizontal stabilizers can cause the aircraft to become asymmetric, thus resulting in a coupling between the longitudinal and lateral motions. Flight dynamics for a general asymmetric aircraft is derived to account for changes in the center of gravity that can compromise the stability of the damaged aircraft. An iterative trim analysis for the translational motion is developed to refine the trim procedure by accounting for the effects of the control surface deflection. A hybrid direct-indirect neural network, adaptive flight control is proposed as an adaptive law for stabilizing the rotational motion of the damaged aircraft. The indirect adaptation is designed to estimate the plant dynamics of the damaged aircraft in conjunction with the direct adaptation that computes the control augmentation. Two approaches are presented 1) an adaptive law derived from the Lyapunov stability theory to ensure that the signals are bounded, and 2) a recursive least-square method for parameter identification. A hardware-in-the-loop simulation is conducted and demonstrates the effectiveness of the direct neural network adaptive flight control in the stability recovery of the damaged aircraft. A preliminary simulation of the hybrid adaptive flight control has been performed and initial data have shown the effectiveness of the proposed hybrid approach. Future work will include further investigations and high-fidelity simulations of the proposed hybrid adaptive Bight control approach.

  15. Computational analysis of noise reduction devices in axial fans with stabilized finite element formulations

    Science.gov (United States)

    Corsini, A.; Rispoli, F.; Sheard, A. G.; Tezduyar, T. E.

    2012-12-01

    The paper illustrates how a computational fluid mechanic technique, based on stabilized finite element formulations, can be used in analysis of noise reduction devices in axial fans. Among the noise control alternatives, the study focuses on the use of end-plates fitted at the blade tips to control the leakage flow and the related aeroacoustic sources. The end-plate shape is configured to govern the momentum transfer to the swirling flow at the blade tip. This flow control mechanism has been found to have a positive link to the fan aeroacoustics. The complex physics of the swirling flow at the tip, developing under the influence of the end-plate, is governed by the rolling up of the jet-like leakage flow. The RANS modelling used in the computations is based on the streamline-upwind/Petrov-Galerkin and pressure-stabilizing/Petrov-Galerkin methods, supplemented with the DRDJ stabilization. Judicious determination of the stabilization parameters involved is also a part of our computational technique and is described for each component of the stabilized formulation. We describe the flow physics underlying the design of the noise control device and illustrate the aerodynamic performance. Then we investigate the numerical performance of the formulation by analysing the inner workings of the stabilization operators and of their interaction with the turbulence model.

  16. Dynamic Stability of Euler Beams under Axial Unsteady Wind Force

    Directory of Open Access Journals (Sweden)

    You-Qin Huang

    2014-01-01

    Full Text Available Dynamic instability of beams in complex structures caused by unsteady wind load has occurred more frequently. However, studies on the parametric resonance of beams are generally limited to harmonic loads, while arbitrary dynamic load is rarely involved. The critical frequency equation for simply supported Euler beams with uniform section under arbitrary axial dynamic forces is firstly derived in this paper based on the Mathieu-Hill equation. Dynamic instability regions with high precision are then calculated by a presented eigenvalue method. Further, the dynamically unstable state of beams under the wind force with any mean or fluctuating component is determined by load normalization, and the wind-induced parametric resonant response is computed by the Runge-Kutta approach. Finally, a measured wind load time-history is input into the dynamic system to indicate that the proposed methods are effective. This study presents a new method to determine the wind-induced dynamic stability of Euler beams. The beam would become dynamically unstable provided that the parametric point, denoting the relation between load properties and structural frequency, is located in the instability region, no matter whether the wind load component is large or not.

  17. Classical and quantum stability of higher-derivative dynamics

    CERN Document Server

    Kaparulin, D S; Sharapov, A A

    2014-01-01

    We observe that a wide class of higher-derivative systems admits a bounded integral of motion that ensures the classical stability of dynamics, while the canonical energy is unbounded. We use the concept of a Lagrange anchor to demonstrate that the bounded integral of motion is connected with the time-translation invariance. A procedure is suggested for switching on interactions in free higher-derivative systems without breaking their stability. We also demonstrate the quantization technique that keeps the higher-derivative dynamics stable at quantum level. The general construction is illustrated by the examples of the Pais-Uhlenbeck oscillator, higher-derivative scalar field model, and the Podolsky electrodynamics. For all these models, the positive integrals of motion are explicitly constructed and the interactions are included such that keep the system stable.

  18. Development of a transfer function method for dynamic stability measurement

    Science.gov (United States)

    Johnson, W.

    1977-01-01

    Flutter testing method based on transfer function measurements is developed. The error statistics of several dynamic stability measurement methods are reviewed. It is shown that the transfer function measurement controls the error level by averaging the data and correlating the input and output. The method also gives a direct estimate of the error in the response measurement. An algorithm is developed for obtaining the natural frequency and damping ratio of low damped modes of the system, using integrals of the transfer function in the vicinity of a resonant peak. Guidelines are given for selecting the parameters in the transfer function measurement. Finally, the dynamic stability measurement technique is applied to data from a wind tunnel test of a proprotor and wing model.

  19. Adaptive Dynamic Programming for Control Algorithms and Stability

    CERN Document Server

    Zhang, Huaguang; Luo, Yanhong; Wang, Ding

    2013-01-01

    There are many methods of stable controller design for nonlinear systems. In seeking to go beyond the minimum requirement of stability, Adaptive Dynamic Programming for Control approaches the challenging topic of optimal control for nonlinear systems using the tools of  adaptive dynamic programming (ADP). The range of systems treated is extensive; affine, switched, singularly perturbed and time-delay nonlinear systems are discussed as are the uses of neural networks and techniques of value and policy iteration. The text features three main aspects of ADP in which the methods proposed for stabilization and for tracking and games benefit from the incorporation of optimal control methods: • infinite-horizon control for which the difficulty of solving partial differential Hamilton–Jacobi–Bellman equations directly is overcome, and  proof provided that the iterative value function updating sequence converges to the infimum of all the value functions obtained by admissible control law sequences; • finite-...

  20. Exponential Stability of Stochastic Nonlinear Dynamical Price System with Delay

    Directory of Open Access Journals (Sweden)

    Wenli Zhu

    2013-01-01

    Full Text Available Based on Lyapunov stability theory, Itô formula, stochastic analysis, and matrix theory, we study the exponential stability of the stochastic nonlinear dynamical price system. Using Taylor's theorem, the stochastic nonlinear system with delay is reduced to an n-dimensional semilinear stochastic differential equation with delay. Some sufficient conditions of exponential stability and corollaries for such price system are established by virtue of Lyapunov function. The time delay upper limit is solved by using our theoretical results when the system is exponentially stable. Our theoretical results show that if the classical price Rayleigh equation is exponentially stable, so is its perturbed system with delay provided that both the time delay and the intensity of perturbations are small enough. Two examples are presented to illustrate our results.

  1. Experimental Study on the Dynamic Stability of the IXV Configuration

    OpenAIRE

    Gülhan, Ali; Klevanski, Josef; Gawehn, Thomas

    2015-01-01

    Dynamic stability of the IXV configuration has been investigated using free oscillation measurement technique in the Trisonic Windtunnel (TMK). In the transonic Mach number range an escalating behavior of the pitching moment damping derivative has been observed, although the vehicle is statically stable. At Mach 0.8 the vehicle showed the most unstable behavior. The instability becomes weaker with increasing Mach number. At Mach number 1.1 the vehicle is only slight...

  2. Structural Optimization of Machine Gun Based on Dynamic Stability Concept

    Institute of Scientific and Technical Information of China (English)

    LI Yong-jian; WANG Rui-lin; ZHANG Ben-jun

    2008-01-01

    Improving the firing accuracy is a final goal of structural optimization of machine guns. The main factors which affect the dispersion accuracy of machine gun are analyzed. Based on the concept of dynamic stability, a structural optimization model is built up, and the sensitivity of dispersion accuracy to design variables is analyzed. The optimization results of a type of machine gun show that the method is valid, feasible, and can be used as a guide to the structural optimization of other automatic weapons.

  3. Dynamic stabilization for degenerative spondylolisthesis and lumbar spinal instability.

    Science.gov (United States)

    Ohtonari, Tatsuya; Nishihara, Nobuharu; Suwa, Katsuyasu; Ota, Taisei; Koyama, Tsunemaro

    2014-01-01

    Lumbar interbody fusion is a widely accepted surgical procedure for patients with lumbar degenerative spondylolisthesis and lumbar spinal instability in the active age group. However, in elderly patients, it is often questionable whether it is truly necessary to construct rigid fixation for a short period of time. In recent years, we have been occasionally performing posterior dynamic stabilization in elderly patients with such lumbar disorders. Posterior dynamic stabilization was performed in 12 patients (6 women, 70.9 ± 5.6 years old at the time of operation) with lumbar degenerative spondylolisthesis in whom % slip was less than 20% or instability associated with lumbar disc herniation between March 2011 and March 2013. Movement occurs through the connector linked to the pedicle screw. In practice, 9 pairs of D connector system where the rod moves in the perpendicular direction alone and 8 pairs of Dynamic connector system where the connector linked to the pedicle screw rotates in the sagittal direction were installed. The observation period was 77-479 days, and the mean recovery rate of lumbar Japanese Orthopedic Association (JOA) score was 65.6 ± 20.8%. There was progression of slippage due to slight loosening in a case with lumbar degenerative spondylolisthesis, but this did not lead to exacerbation of the symptoms. Although follow-up was short, there were no symptomatic adjacent vertebral and disc disorders during this period. Posterior dynamic stabilization may diminish the development of adjacent vertebral or disc disorders due to lumbar interbody fusion, especially in elderly patients, and it may be a useful procedure that facilitates decompression and ensures a certain degree of spinal stabilization.

  4. Facet joint changes after application of lumbar nonfusion dynamic stabilization.

    Science.gov (United States)

    Lee, Soo Eon; Jahng, Tae-Ahn; Kim, Hyun Jib

    2016-01-01

    OBJECTIVE The long-term effects on adjacent-segment pathology after nonfusion dynamic stabilization is unclear, and, in particular, changes at the adjacent facet joints have not been reported in a clinical study. This study aims to compare changes in the adjacent facet joints after lumbar spinal surgery. METHODS Patients who underwent monosegmental surgery at L4-5 with nonfusion dynamic stabilization using the Dynesys system (Dynesys group) or transforaminal lumbar interbody fusion with pedicle screw fixation (fusion group) were retrospectively compared. Facet joint degeneration was evaluated at each segment using the CT grading system. RESULTS The Dynesys group included 15 patients, while the fusion group included 22 patients. The preoperative facet joint degeneration CT grades were not different between the 2 groups. Compared with the preoperative CT grades, 1 side of the facet joints at L3-4 and L4-5 had significantly more degeneration in the Dynesys group. In the fusion group, significant facet joint degeneration developed on both sides at L2-3, L3-4, and L5-S1. The subjective back and leg pain scores were not different between the 2 groups during follow-up, but functional outcome based on the Oswestry Disability Index improved less in the fusion group than in the Dynesys group. CONCLUSIONS Nonfusion dynamic stabilization using the Dynesys system had a greater preventative effect on facet joint degeneration in comparison with that obtained using fusion surgery. The Dynesys system, however, resulted in facet joint degeneration at the instrumented segments and above. An improved physiological nonfusion dynamic stabilization system for lumbar spinal surgery should be developed.

  5. Dynamic stability and phase resetting during biped gait

    Science.gov (United States)

    Nomura, Taishin; Kawa, Kazuyoshi; Suzuki, Yasuyuki; Nakanishi, Masao; Yamasaki, Taiga

    2009-06-01

    Dynamic stability during periodic biped gait in humans and in a humanoid robot is considered. Here gait systems of human neuromusculoskeletal system and a humanoid are simply modeled while keeping their mechanical properties plausible. We prescribe periodic gait trajectories in terms of joint angles of the models as a function of time. The equations of motion of the models are then constrained by one of the prescribed gait trajectories to obtain types of periodically forced nonlinear dynamical systems. Simulated gait of the models may or may not fall down during gait, since the constraints are made only for joint angles of limbs but not for the motion of the body trunk. The equations of motion can exhibit a limit cycle solution (or an oscillatory solution that can be considered as a limit cycle practically) for each selected gait trajectory, if an initial condition is set appropriately. We analyze the stability of the limit cycle in terms of Poincaré maps and the basin of attraction of the limit cycle in order to examine how the stability depends on the prescribed trajectory. Moreover, the phase resetting of gait rhythm in response to external force perturbation is modeled. Since we always prescribe a gait trajectory in this study, reacting gait trajectories during the phase resetting are also prescribed. We show that an optimally prescribed reacting gait trajectory with an appropriate amount of the phase resetting can increase the gait stability. Neural mechanisms for generation and modulation of the gait trajectories are discussed.

  6. Dynamical behavior and Jacobi stability analysis of wound strings

    CERN Document Server

    Lake, Matthew J

    2016-01-01

    We numerically solve the equations of motion (EOM) for two models of circular cosmic string loops with windings in a simply connected internal space. Since the windings cannot be topologically stabilized, stability must be achieved (if at all) dynamically. As toy models for realistic compactifications, we consider windings on a small section of $\\mathbb{R}^2$, which is valid as an approximation to any simply connected internal manifold if the winding radius is sufficiently small, and windings on an $S^2$ of constant radius $\\mathcal{R}$. We then use Kosambi-Cartan-Chern (KCC) theory to analyze the Jacobi stability of the string equations and determine bounds on the physical parameters that ensure dynamical stability of the windings. We find that, for the same initial conditions, the curvature and topology of the internal space have nontrivial effects on the microscopic behavior of the string in the higher dimensions, but that the macroscopic behavior is remarkably insensitive to the details of the motion in t...

  7. A Point Dynamic Model for Stability Analysis of the PGSFR

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Pham Nhu Viet; Choi, Sun Rock; Lee, Min Jae; Kang, Chang Moo; Kim, Sang Ji [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    To ensure the enhanced safety criteria for an advanced reactor system, the PGSFR design is highly based on the inherent safety mechanisms, i.e., passive responses to abnormal and emergency conditions, and thereby minimizes the need for active or engineered safety systems. In this regard, various inherent reactivity feedbacks in the PGSFR including thermal expansion of the sodium coolant, fuel temperature change, thermal bowing of the fuel, thermal expansion of the core and structure, and thermal expansion of the control rod drive line should be carefully evaluated in the design process. Of primary importance is to clarify the influence of the inherent reactivity feedbacks on the reactor dynamics and stability against small reactivity disturbances under power operating conditions. The reactor response to such small reactivity disturbances is determined by the interaction of the various reactivity coefficients, magnitude of the initial reactivity insertion, and nature of the heat removal system. It was shown that the stability property of the PGSFR is the same for all the three considered forcing functions. Furthermore, the PGSFR was found to be inherently stable thanks to the inherent negative reactivity coefficients and its stability is even more enhanced with fuel burnup in the equilibrium cycle. Especially, the conditions under which the PGSFR can become unstable in the presence of one or more positive reactivity coefficients were revealed. As a result, this study can provide designers useful information about the reactor dynamics along with the impacts of positive reactivity coefficients for further improvements of the reactor stability under power operating conditions.

  8. Dynamic remedial action scheme using online transient stability analysis

    Science.gov (United States)

    Shrestha, Arun

    Economic pressure and environmental factors have forced the modern power systems to operate closer to their stability limits. However, maintaining transient stability is a fundamental requirement for the operation of interconnected power systems. In North America, power systems are planned and operated to withstand the loss of any single or multiple elements without violating North American Electric Reliability Corporation (NERC) system performance criteria. For a contingency resulting in the loss of multiple elements (Category C), emergency transient stability controls may be necessary to stabilize the power system. Emergency control is designed to sense abnormal conditions and subsequently take pre-determined remedial actions to prevent instability. Commonly known as either Remedial Action Schemes (RAS) or as Special/System Protection Schemes (SPS), these emergency control approaches have been extensively adopted by utilities. RAS are designed to address specific problems, e.g. to increase power transfer, to provide reactive support, to address generator instability, to limit thermal overloads, etc. Possible remedial actions include generator tripping, load shedding, capacitor and reactor switching, static VAR control, etc. Among various RAS types, generation shedding is the most effective and widely used emergency control means for maintaining system stability. In this dissertation, an optimal power flow (OPF)-based generation-shedding RAS is proposed. This scheme uses online transient stability calculation and generator cost function to determine appropriate remedial actions. For transient stability calculation, SIngle Machine Equivalent (SIME) technique is used, which reduces the multimachine power system model to a One-Machine Infinite Bus (OMIB) equivalent and identifies critical machines. Unlike conventional RAS, which are designed using offline simulations, online stability calculations make the proposed RAS dynamic and adapting to any power system

  9. Dynamical stability of the holographic system with two competing orders

    Energy Technology Data Exchange (ETDEWEB)

    Du, Yiqiang [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); Lan, Shan-Quan [Department of Physics, Beijing Normal University,Beijing 100875 (China); Tian, Yu [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); State Key Laboratory of Theoretical Physics,Institute of Theoretical Physics, Chinese Academy of Science,Beijing 100190 (China); Zhang, Hongbao [Department of Physics, Beijing Normal University,Beijing 100875 (China); Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes,Pleinlaan 2, B-1050 Brussels (Belgium)

    2016-01-04

    We investigate the dynamical stability of the holographic system with two order parameters, which exhibits competition and coexistence of condensations. In the linear regime, we have developed the gauge dependent formalism to calculate the quasi-normal modes by gauge fixing, which turns out be considerably convenient. Furthermore, by giving different Gaussian wave packets as perturbations at the initial time, we numerically evolve the full nonlinear system until it arrives at the final equilibrium state. Our results show that the dynamical stability is consistent with the thermodynamical stability. Interestingly, the dynamical evolution, as well as the quasi-normal modes, shows that the relaxation time of this model is generically much longer than the simplest holographic system. We also find that the late time behavior can be well captured by the lowest lying quasi-normal modes except for the non-vanishing order towards the single ordered phase. To our knowledge, this exception is the first counter example to the general belief that the late time behavior towards a final stable state can be captured by the lowest lying quasi-normal modes. In particular, a double relation is found for this exception in certain cases.

  10. Stationary Stability for Evolutionary Dynamics in Finite Populations

    Directory of Open Access Journals (Sweden)

    Marc Harper

    2016-08-01

    Full Text Available We demonstrate a vast expansion of the theory of evolutionary stability to finite populations with mutation, connecting the theory of the stationary distribution of the Moran process with the Lyapunov theory of evolutionary stability. We define the notion of stationary stability for the Moran process with mutation and generalizations, as well as a generalized notion of evolutionary stability that includes mutation called an incentive stable state (ISS candidate. For sufficiently large populations, extrema of the stationary distribution are ISS candidates and we give a family of Lyapunov quantities that are locally minimized at the stationary extrema and at ISS candidates. In various examples, including for the Moran and Wright–Fisher processes, we show that the local maxima of the stationary distribution capture the traditionally-defined evolutionarily stable states. The classical stability theory of the replicator dynamic is recovered in the large population limit. Finally we include descriptions of possible extensions to populations of variable size and populations evolving on graphs.

  11. Dynamic flight stability of a bumblebee in forward flight

    Institute of Scientific and Technical Information of China (English)

    Yan Xiong; Mao Sun

    2008-01-01

    The longitudinal dynamic flight stability of a bumblebee in forward flight is studied.The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis are employed for solving the equations of motion.The primary findings are as the following.The forward flight of the bumblebee is not dynamically stable due to the existence of one(or two)unstable or approximately neutrally stable natural modes of motion.At hovering to medium flight speed[flight speed ue=(0-3.5)m s-1;advance ratio J=0-0.44],the flight is weakly unstable or approximately neutrally stable;at high speed(ue=4.5 m s-1;J=0.57),the flight becomes strongly unstable(initial disturbance double its value in only 3.5 wingbeats).

  12. Dynamics and stability of a vertical water bridge

    CERN Document Server

    Namin, Reza Montazeri

    2013-01-01

    A vertical connection of water is formed when a high voltage electrode is dipped in and pulled out of a container of deionized water. We considered the formation, stability and dynamical characteristics of this vertical water bridge. For the first time in this field, we observed instabilities in the bridge that led to an oscillatory behaviour which is categorized in three dynamical regimes and supplied explanations on the physics behind these varied motions. We report the formation of macroscopic droplets during this motion, which their dynamics revealed that they are electrically charged. In some cases the droplets would be levitating when the electric force opposes the gravity. Also the steady bridge is thoroughly studied regarding its geometry and a set of quantitative data is presented using dimensionless numbers, which brings the possibility of direct quantitative comparison between theory and experiments. Our results shed light on the physics behind this phenomenon and the horizontal water bridge, which...

  13. Improved multiple-shot gun for use as a combustion stability rating device

    Science.gov (United States)

    Sokolowski, D. E.

    1973-01-01

    A program was conducted to develop and experimentally evaluate an improved version of a modified machine gun for use as a device for rating the relative combustion stability of various rocket combustors. Following the results of a previous study involving a caliber .30 machine gun, a caliber .50 machine gun was modified in order to extend the charge-size range of the device. Nitrocellulose charge sizes ranging from 1.004 to 9.720 grams were fired at rates up to four shots per second. Shock pressures up to 25,512 kN/sq m were measured near the end of a shortened gun barrel. A minimal resistance type of check valve permitted the gun to fire into pressurized regions; back pressures up to 3448 kN/sq m abs were tested. The final modified assembly was evaluated during combustion stability tests on rocket combustors burning a FLOX-methane propellant combination.

  14. Fast Dynamic Simulation-Based Small Signal Stability Assessment and Control

    Energy Technology Data Exchange (ETDEWEB)

    Acharya, Naresh [General Electric Company, Fairfield, CT (United States); Baone, Chaitanya [General Electric Company, Fairfield, CT (United States); Veda, Santosh [General Electric Company, Fairfield, CT (United States); Dai, Jing [General Electric Company, Fairfield, CT (United States); Chaudhuri, Nilanjan [General Electric Company, Fairfield, CT (United States); Leonardi, Bruno [General Electric Company, Fairfield, CT (United States); Sanches-Gasca, Juan [General Electric Company, Fairfield, CT (United States); Diao, Ruisheng [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wu, Di [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Huang, Zhenyu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhang, Yu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jin, Shuangshuang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zheng, Bin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chen, Yousu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-12-31

    Power grid planning and operation decisions are made based on simulation of the dynamic behavior of the system. Enabling substantial energy savings while increasing the reliability of the aging North American power grid through improved utilization of existing transmission assets hinges on the adoption of wide-area measurement systems (WAMS) for power system stabilization. However, adoption of WAMS alone will not suffice if the power system is to reach its full entitlement in stability and reliability. It is necessary to enhance predictability with "faster than real-time" dynamic simulations that will enable the dynamic stability margins, proactive real-time control, and improve grid resiliency to fast time-scale phenomena such as cascading network failures. Present-day dynamic simulations are performed only during offline planning studies, considering only worst case conditions such as summer peak, winter peak days, etc. With widespread deployment of renewable generation, controllable loads, energy storage devices and plug-in hybrid electric vehicles expected in the near future and greater integration of cyber infrastructure (communications, computation and control), monitoring and controlling the dynamic performance of the grid in real-time would become increasingly important. The state-of-the-art dynamic simulation tools have limited computational speed and are not suitable for real-time applications, given the large set of contingency conditions to be evaluated. These tools are optimized for best performance of single-processor computers, but the simulation is still several times slower than real-time due to its computational complexity. With recent significant advances in numerical methods and computational hardware, the expectations have been rising towards more efficient and faster techniques to be implemented in power system simulators. This is a natural expectation, given that the core solution algorithms of most commercial simulators were developed

  15. Dynamic stability of spine using stability-based optimization and muscle spindle reflex.

    Science.gov (United States)

    Zeinali-Davarani, Shahrokh; Hemami, Hooshang; Barin, Kamran; Shirazi-Adl, Aboulfazl; Parnianpour, Mohamad

    2008-02-01

    A computational method for simulation of 3-D movement of the trunk under the control of 48 anatomically oriented muscle actions was developed. Neural excitation of muscles was set based on inverse dynamics approach along with the stability-based optimization. The effect of muscle spindle reflex response on the trunk movement stability was evaluated upon the application of a perturbation moment. The method was used to simulate the trunk movement from the upright standing to 60 degrees of flexion. Incorporation of the stability condition as an additional constraint in the optimization resulted in an increase in antagonistic activities demonstrating that the antagonistic co-activation acts to increase the trunk stability in response to self-induced postural internal perturbation. In presence of a 30 Nm flexion perturbation moment, muscle spindles decreased the induced deviation of the position and velocity profiles from the desired ones. The stability-generated co-activation decreased the reflexive response of muscle spindles to the perturbation demonstrating that the rise in muscle co-activation can ameliorate the corruption of afferent neural sensory system at the expense of higher loading of the spine.

  16. Optimal setting of FACTS devices for voltage stability improvement using PSO adaptive GSA hybrid algorithm

    Directory of Open Access Journals (Sweden)

    Sai Ram Inkollu

    2016-09-01

    Full Text Available This paper presents a novel technique for optimizing the FACTS devices, so as to maintain the voltage stability in the power transmission systems. Here, the particle swarm optimization algorithm (PSO and the adaptive gravitational search algorithm (GSA technique are proposed for improving the voltage stability of the power transmission systems. In the proposed approach, the PSO algorithm is used for optimizing the gravitational constant and to improve the searching performance of the GSA. Using the proposed technique, the optimal settings of the FACTS devices are determined. The proposed algorithm is an effective method for finding out the optimal location and the sizing of the FACTS controllers. The optimal locations and the power ratings of the FACTS devices are determined based on the voltage collapse rating as well as the power loss of the system. Here, two FACTS devices are used to evaluate the performance of the proposed algorithm, namely, the unified power flow controller (UPFC and the interline power flow controller (IPFC. The Newton–Raphson load flow study is used for analyzing the power flow in the transmission system. From the power flow analysis, bus voltages, active power, reactive power, and power loss of the transmission systems are determined. Then, the voltage stability is enhanced while satisfying a given set of operating and physical constraints. The proposed technique is implemented in the MATLAB platform and consequently, its performance is evaluated and compared with the existing GA based GSA hybrid technique. The performance of the proposed technique is tested with the benchmark system of IEEE 30 bus using two FACTS devices such as, the UPFC and the IPFC.

  17. Tunable Ultrafast Photon Source and Imaging System for Studying Carrier Dynamics in Graphene Devices

    Science.gov (United States)

    2015-07-23

    Tunable ultrafast photon source and imaging system for studying carrier dynamics in graphene devices This project enabled the acquisition of a...and imaging system for studying carrier dynamics in graphene devices Report Title This project enabled the acquisition of a optical parametric...carrier dynamics in graphene devices As discussed below the focus of this DURIP project was on understanding the interaction between electrons, holes

  18. High mobility and high stability glassy metal-oxynitride materials and devices

    Science.gov (United States)

    Lee, Eunha; Kim, Taeho; Benayad, Anass; Hur, Jihyun; Park, Gyeong-Su; Jeon, Sanghun

    2016-04-01

    In thin film technology, future semiconductor and display products with high performance, high density, large area, and ultra high definition with three-dimensional functionalities require high performance thin film transistors (TFTs) with high stability. Zinc oxynitride, a composite of zinc oxide and zinc nitride, has been conceded as a strong substitute to conventional semiconductor film such as silicon and indium gallium zinc oxide due to high mobility value. However, zinc oxynitride has been suffered from poor reproducibility due to relatively low binding energy of nitrogen with zinc, resulting in the instability of composition and its device performance. Here we performed post argon plasma process on zinc oxynitride film, forming nano-crystalline structure in stable amorphous matrix which hampers the reaction of oxygen with zinc. Therefore, material properties and device performance of zinc oxynitride are greatly enhanced, exhibiting robust compositional stability even exposure to air, uniform phase, high electron mobility, negligible fast transient charging and low noise characteristics. Furthermore, We expect high mobility and high stability zinc oxynitride customized by plasma process to be applicable to a broad range of semiconductor and display devices.

  19. Coracoclavicular stabilization using a suture button device for Neer type IIB lateral clavicle fractures.

    Science.gov (United States)

    Cho, Chul-Hyun; Jung, Jae-Hoon; Kim, Beom-Soo

    2017-05-01

    The purpose of this study was to evaluate the radiologic and clinical outcomes of coracoclavicular (CC) stabilization using a suture button device for Neer type IIB lateral clavicle fractures. Eighteen consecutive patients with Neer type IIB fractures were treated with CC stabilization using a TightRope device (Arthrex, Naples, FL, USA). The mean follow-up period was 46.6 months (range, 24-75 months). Radiologic outcomes were assessed using serial plain radiographs. Clinical outcomes were evaluated using the visual analog scale pain score; University of California, Los Angeles score; American Shoulder and Elbow Surgeons score; and subjective shoulder value. Intraoperative and postoperative complications were also evaluated. Of the 18 cases, 17 (94.4%) showed complete bony union. The mean final visual analog scale pain score was 1.1; University of California, Los Angeles score, 31.3; American Shoulder and Elbow Surgeons score, 88.6; and subjective shoulder value, 88.5%. Four complications were observed: (1) intraoperative coracoid process fracture, (2) nonunion, (3) delayed union, and (4) shoulder stiffness. The case with a coracoid process fracture during coracoid tunnel generation was converted to the K-wire tension band technique. CC stabilization using a suture button device for Neer type IIB lateral clavicle fractures yielded satisfactory radiologic and clinical outcomes. The major advantage of this technique is that implant removal is not required. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  20. Predator interference and stability of predator-prey dynamics.

    Science.gov (United States)

    Přibylová, Lenka; Berec, Luděk

    2015-08-01

    Predator interference, that is, a decline in the per predator consumption rate as predator density increases, is generally thought to promote predator-prey stability. Indeed, this has been demonstrated in many theoretical studies on predator-prey dynamics. In virtually all of these studies, the stabilization role is demonstrated as a weakening of the paradox of enrichment. With predator interference, stable limit cycles that appear as a result of environmental enrichment occur for higher values of the environmental carrying capacity of prey, and even a complete absence of the limit cycles can happen. Here we study predator-prey dynamics using the Rosenzweig-MacArthur-like model in which the Holling type II functional response has been replaced by a predator-dependent family which generalizes many of the commonly used descriptions of predator interference. By means of a bifurcation analysis we show that sufficiently strong predator interference may bring about another stabilizing mechanism. In particular, hysteresis combined with (dis)appearance of stable limit cycles imply abrupt increases in both the prey and predator densities and enhanced persistence and resilience of the predator-prey system. We encourage refitting the previously collected data on predator consumption rates as well as for conducting further predation experiments to see what functional response from the explored family is the most appropriate.

  1. Assessment of current criteria for dynamic stability of container vessels

    Science.gov (United States)

    Stanca, C.; Ancuta, C.; Acomi, N.; Andrei, C.

    2016-08-01

    Container vessels sailing through heavy weather are exposed to a significant variation of stability due to specific shape of the hull combined with the action of the waves. Even if the weather forecast is transmitted to vessels, the way of acting it is a matter of officers’ experience. The Maritime Safety Committee, under the International Maritime Organization, has approved the Guidance to the master for avoiding dangerous situations in adverse weather and sea conditions. Adverse weather conditions include wind induced waves or heavy swell. The development of dangerous phenomena such as surf-riding and broaching to, syncronious and parametric rollings is a result of a these adverse conditions which has to be encountered by the vessels. Understanding the dynamic stability of the vessel in the waves and ship's behaviour based on mathematical and physical rules is a difficult task, any effort in order to assess these components are salutary. To avoid excessive acceleration and forces which can damage the hull of the vessel, lashing and integrity of containers, course and speed may need to be changed for the vessel's motion in heavy seas. Specific software have been developed as aids for evaluating the response of the vessel in heavy seas according to parameters variations. The paper aims at assessing of current criteria for dynamic stability of a container vessel model ship in order to determine the ways for avoiding dangerous conditions. The results should be regarded as a supporting tool during the decision making process.

  2. Strategy switching in the stabilization of unstable dynamics.

    Directory of Open Access Journals (Sweden)

    Jacopo Zenzeri

    Full Text Available In order to understand mechanisms of strategy switching in the stabilization of unstable dynamics, this work investigates how human subjects learn to become skilled users of an underactuated bimanual tool in an unstable environment. The tool, which consists of a mass and two hand-held non-linear springs, is affected by a saddle-like force-field. The non-linearity of the springs allows the users to determine size and orientation of the tool stiffness ellipse, by using different patterns of bimanual coordination: minimal stiffness occurs when the two spring terminals are aligned and stiffness size grows by stretching them apart. Tool parameters were set such that minimal stiffness is insufficient to provide stable equilibrium whereas asymptotic stability can be achieved with sufficient stretching, although at the expense of greater effort. As a consequence, tool users have two possible strategies for stabilizing the mass in different regions of the workspace: 1 high stiffness feedforward strategy, aiming at asymptotic stability and 2 low stiffness positional feedback strategy aiming at bounded stability. The tool was simulated by a bimanual haptic robot with direct torque control of the motors. In a previous study we analyzed the behavior of naïve users and we found that they spontaneously clustered into two groups of approximately equal size. In this study we trained subjects to become expert users of both strategies in a discrete reaching task. Then we tested generalization capabilities and mechanism of strategy-switching by means of stabilization tasks which consist of tracking moving targets in the workspace. The uniqueness of the experimental setup is that it addresses the general problem of strategy-switching in an unstable environment, suggesting that complex behaviors cannot be explained in terms of a global optimization criterion but rather require the ability to switch between different sub-optimal mechanisms.

  3. Nanoalloy Printed and Pulse-Laser Sintered Flexible Sensor Devices with Enhanced Stability and Materials Compatibility

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Wei; Rovore, Thomas; Weerawarne, Darshana; Osterhoudt, Gavin; Kang, Ning; Joseph, Pharrah; Luo, Jin; Shim, Bonggu; Poliks, Mark; Zhong, Chuan-Jian

    2015-06-02

    While conformal and wearable devices have become one of the most desired formats for printable electronics, it is challenging to establish a scalable process that produces stable conductive patterns but also uses substrates compatible with widely available wearable materials. Here, we describe findings of an investigation of a nanoalloy ink printed and pulsed laser sintered conductive patterns as flexible functional devices with enhanced stability and materials compatibility. While nanoparticle inks are desired for printable electronics, almost all existing nanoparticle inks are based on single-metal component, which, as an electronic element, is limited by its inherent stabilities of the metal such as propensity of metal oxidation and mobility of metal ions, especially in sintering processes. The work here has demonstrated the first example in exploiting plasmonic coupling of nanoalloys and pulsed-laser energy with controllable thermal penetration. The experimental and theoretical results have revealed clear correlation between the pulsed laser parameters and the nanoalloy structural characteristics. The superior performance of the resulting flexible sensor device, upon imparting nanostructured sensing materials, for detecting volatile organic compounds has significant implications to developing stable and wearable sensors for monitoring environmental pollutants and breath biomarkers. This simple “nanoalloy printing 'laser sintering' nanostructure printing” process is entirely general to many different sensor devices and nanostructured sensing materials, enabling the ability to easily construct sophisticated sensor array.

  4. Kinematic variability, fractal dynamics and local dynamic stability of treadmill walking

    Directory of Open Access Journals (Sweden)

    Terrier Philippe

    2011-02-01

    Full Text Available Abstract Background Motorized treadmills are widely used in research or in clinical therapy. Small kinematics, kinetics and energetics changes induced by Treadmill Walking (TW as compared to Overground Walking (OW have been reported in literature. The purpose of the present study was to characterize the differences between OW and TW in terms of stride-to-stride variability. Classical (Standard Deviation, SD and non-linear (fractal dynamics, local dynamic stability methods were used. In addition, the correlations between the different variability indexes were analyzed. Methods Twenty healthy subjects performed 10 min TW and OW in a random sequence. A triaxial accelerometer recorded trunk accelerations. Kinematic variability was computed as the average SD (MeanSD of acceleration patterns among standardized strides. Fractal dynamics (scaling exponent α was assessed by Detrended Fluctuation Analysis (DFA of stride intervals. Short-term and long-term dynamic stability were estimated by computing the maximal Lyapunov exponents of acceleration signals. Results TW did not modify kinematic gait variability as compared to OW (multivariate T2, p = 0.87. Conversely, TW significantly modified fractal dynamics (t-test, p = 0.01, and both short and long term local dynamic stability (T2 p = 0.0002. No relationship was observed between variability indexes with the exception of significant negative correlation between MeanSD and dynamic stability in TW (3 × 6 canonical correlation, r = 0.94. Conclusions Treadmill induced a less correlated pattern in the stride intervals and increased gait stability, but did not modify kinematic variability in healthy subjects. This could be due to changes in perceptual information induced by treadmill walking that would affect locomotor control of the gait and hence specifically alter non-linear dependencies among consecutive strides. Consequently, the type of walking (i.e. treadmill or overground is important to consider in

  5. Pre-analytical stability of selected benzodiazepines on a polymeric oral fluid sampling device.

    Science.gov (United States)

    Kempf, Jürgen; Wuske, Thomas; Schubert, Rolf; Weinmann, Wolfgang

    2009-04-15

    Oral fluid field tests are designed to provide preliminary results with a high grade of reliability in order to meet analytical and forensic standards. Some test systems additionally offer the possibility of an independent confirmatory analysis of a test sample. The pre-analytical stability of 11 frequently abused benzodiazepines on an oral fluid collecting device (Dräger DCD 5000) has been investigated. The collection device was designed to complement a special mobile testing system (Dräger DrugTest 5000) to be sent to a laboratory for further confirmatory analysis. Blank oral fluid pool was spiked with a mixture of eleven frequently abused benzodiazepines and given onto a collection device. To simulate possible sample shipping, the collection devices were stored in the dark up to 14 days at ambient temperature in a plastic tube. The collection device was simultaneously stored without further treatment after oral fluid collection ('native') and with addition of 950muL of methanol, respectively. At different storage intervals repeat determination was carried out for every sample using a modified version of our standard LC-MS/MS method for the detection of benzodiazepines in serum. Different recoveries of benzodiazepines due to degradation and/or adsorption to the collection device during the 14 days of 'native' storage were found. Major loss of analytes was found for benzodiazepines containing a nitro-group such as flunitrazepam and clonazepam. This could be prevented almost completely by methanolic storage of the collection device after sampling. Therefore, we recommend the centrifugation of the collection device and separation from the polymer unit prior to sample shipping. If this should not be possible, addition of methanol immediately after sample collection can be used to avoid degradation of benzodiazepines during shipment.

  6. Dynamic Modeling, Testing, and Stability Analysis of an Ornithoptic Blimp

    Institute of Scientific and Technical Information of China (English)

    John Dietl; Thomas Herrmann; Gregory Reich; Ephrahim Garcia

    2011-01-01

    In order to study omithopter flight and to improve a dynamic model of flapping propulsion,a series of tests are conducted on a flapping-wing blimp.The blimp is designed and constructed from mylar plastic and balsa wood as a test platform for aerodynamics and flight dynamics.The blimp,2.3 meters long and 420 gram mass,is propelled by its flapping wings.Due to buoyancy the wings have no lift requirement so that the distinction between lift and propulsion can be analyzed in a flight platform at low flight speeds.The blimp is tested using a Vicon motion tracking system and various initial conditions are tested including accelerating flight from standstill,decelerating from an initial speed higher than its steady state,and from its steady-state speed but disturbed in pitch angle.Test results are used to estimate parameters in a coupled quasi-steady aerodynamics/Newtonian flight dynamics model.This model is then analyzed using Floquet theory to determine local dynamic modes and stability.It is concluded that the dynamic model adequately describes the vehicle's nonlinear behavior near the steady-state velocity and that the vehicle's linearized modes are akin to those of a fixed-wing aircraft.

  7. Magnetic Dynamics of Single-Domain Planar Spin-Transfer Devices

    Science.gov (United States)

    Bazaliy, Ya. B.

    2008-03-01

    We study spin-transfer devices with dynamic magnets characterized by large easy-plane anisotropy. This situation is standard for planar devices where it arises due to the shape anisotropy. Dominating easy-plane anisotropy keeps the motion of the magnetic moment close to the easy plane, with small out-of-plane deviations. As a result, it is possible to approximately describe magnetization vector by the in-plane angle and derive an effective one dimensional equation for that angle in the absence [1] and in the presence [2] of spin-transfer torques. Effective description maps a spin-transfer device problem onto a problem of an ``effective particle'' moving in external potential with variable friction coefficient. The advantage of such a description is that the motion of the effective particle can be qualitatively understood by applying the usual energy conservation and dissipation arguments. We show how the effective description produces analytic results for current induced precession states [3] and predicts unconventional ``stabilization by repulsion'' of static states [2]. // [1] C. J. Garcia-Cervera, Weinan E, J. Appl. Phys. 90, 370 (2001). [2] Ya. B. Bazaliy, Phys. Rev. B 76, 140402(R) (2007). [3] Ya. B. Bazaliy, arXiv:0705.0508, to be published in Appl. Phys. Lett. (2007).

  8. Thermal stability of marks gold nanoparticles: A molecular dynamics simulation

    Science.gov (United States)

    Jia, Yanlin; Li, Siqi; Qi, Weihong; Wang, Mingpu; Li, Zhou; Wang, Zhixing

    2017-03-01

    Molecular dynamics (MDs) simulations were used to explore the thermal stability of Au nanoparticles (NPs) with decahedral, cuboctahedral, icosahedral and Marks NPs. According to the calculated cohesive energy and melting temperature, the Marks NPs have a higher cohesive energy and melting temperature compared to these other shapes. The Lindemann index, radial distribution function, deformation parameters, mean square displacement and self-diffusivity have been used to characterize the structure variation during heating. This work may inspire researchers to prepare Marks NPs and apply them in different fields.

  9. Fundamental display properties of flexible devices containing polymer-stabilized ferroelectric liquid crystal between plastic substrates

    Science.gov (United States)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Iino, Yoshiki; Kawakita, Masahiro; Kikuchi, Hiroshi

    2002-09-01

    We describe several fundamental display properties of a flexible ferroelectric liquid crystal device containing polymer fibers between thin plastic substrates. The composite film of liquid crystal and polymer was created from a solution of liquid crystal and monomer materials between the plastic substrates under ultraviolet light irradiation. The dynamic electrooptic response to analog voltage pulses was examined with an incidence of laser beam light, and its light modulation property exhibited good linearity in continuous gray-scale capability. The excellent spatial uniformity of liquid crystal alignment formed between the flexible substrates resulted in high-contrast light modulation, although slight spontaneous bending of liquid crystal alignment in the device plane was recognized. When the laser light beam was obliquely incident on the flexible display device, the measured transmittance revealed that the device has a wide viewing angle of more than 100 deg without contrast reversal. This is considered to be caused by the molecular switching in the device plane and the thin electrooptic layer in the display device.

  10. Stability and dynamics of membrane-spanning DNA nanopores

    Science.gov (United States)

    Maingi, Vishal; Burns, Jonathan R.; Uusitalo, Jaakko J.; Howorka, Stefan; Marrink, Siewert J.; Sansom, Mark S. P.

    2017-03-01

    Recently developed DNA-based analogues of membrane proteins have advanced synthetic biology. A fundamental question is how hydrophilic nanostructures reside in the hydrophobic environment of the membrane. Here, we use multiscale molecular dynamics (MD) simulations to explore the structure, stability and dynamics of an archetypical DNA nanotube inserted via a ring of membrane anchors into a phospholipid bilayer. Coarse-grained MD reveals that the lipids reorganize locally to interact closely with the membrane-spanning section of the DNA tube. Steered simulations along the bilayer normal establish the metastable nature of the inserted pore, yielding a force profile with barriers for membrane exit due to the membrane anchors. Atomistic, equilibrium simulations at two salt concentrations confirm the close packing of lipid around of the stably inserted DNA pore and its cation selectivity, while revealing localized structural fluctuations. The wide-ranging and detailed insight informs the design of next-generation DNA pores for synthetic biology or biomedicine.

  11. A Dynamic Stability Criterion for Ice Shelves and Tidewater Glaciers

    Science.gov (United States)

    Bassis, J. N.; Fricker, H. A.; Minster, J.

    2006-12-01

    The collapse of the Antarctic ice shelves could have dramatic consequences for the mass balance of the Antarctic ice sheet and, as a result, sea level rise. It is therefore imperative to improve our knowledge of the mechanisms that lead to ice shelf retreat. The mechanism that has the potential to remove the largest amounts of mass rapidly is iceberg calving. However, the processes and mechanisms that lead to iceberg calving are still poorly understood. Motivated by the complexity of the short-time scale behavior of ice fracture we seek a dynamic stability criterion that predicts the onset of ice shelf retreat based on dimensional analysis. In our approach, rather than attempt to model the initiation and propagation of individual fractures, we look for a non-dimensional number that describes the overall ice shelf stability. We also make the assumption that the same criterion, valid for ice shelves, also applies to tidewater glaciers. This enables us to test our criterion against a larger set of ice shelves and calving glaciers. Our analysis predicts that retreat will occur when a non-dimensional number that we call the "terminus stability number", decreases below a critical value. We show that this criterion is valid for calving glaciers in Alaska, for several glaciers around Greenland as well as for three Antarctic ice shelves. This stability analysis has much in common with classic hydrodynamic stability theory, where the onset of instability is related to non-dimensional numbers that are largely independent of geometry or other situation specific variables.

  12. Non-Linear Dynamics and Stability of Circular Cylindrical Shells Containing Flowing Fluid. Part i: Stability

    Science.gov (United States)

    AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.

    1999-08-01

    The study presented is an investigation of the non-linear dynamics and stability of simply supported, circular cylindrical shells containing inviscid incompressible fluid flow. Non-linearities due to large-amplitude shell motion are considered by using the non-linear Donnell's shallow shell theory, with account taken of the effect of viscous structural damping. Linear potential flow theory is applied to describe the fluid-structure interaction. The system is discretiszd by Galerkin's method, and is investigated by using a model involving seven degrees of freedom, allowing for travelling wave response of the shell and shell axisymmetric contraction. Two different boundary conditions are applied to the fluid flow beyond the shell, corresponding to: (i) infinite baffles (rigid extensions of the shell), and (ii) connection with a flexible wall of infinite extent in the longitudinal direction, permitting solution by separation of variables; they give two different kinds of dynamical behaviour of the system, as a consequence of the fact that axisymmetric contraction, responsible for the softening non-linear dynamical behaviour of shells, is not allowed if the fluid flow beyond the shell is constrained by rigid baffles. Results show that the system loses stability by divergence.

  13. Dynamic plate osteosynthesis for fracture stabilization: how to do it

    Directory of Open Access Journals (Sweden)

    Juerg Sonderegger

    2010-01-01

    Full Text Available Plate osteosynthesis is one treatment option for the stabilization of long bones. It is widely accepted to achieve bone healing with a dynamic and biological fixation where the perfusion of the bone is left intact and micromotion at the fracture gap is allowed. The indications for a dynamic plate osteosynthesis include distal tibial and femoral fractures, some midshaft fractures, and adolescent tibial and femoral fractures with not fully closed growth plates. Although many lower limb shaft fractures are managed successfully with intramedullary nails, there are some important advantages of open-reduction-and-plate fixation: the risk of malalignment, anterior knee pain, or nonunion seems to be lower. The surgeon performing a plate osteosynthesis has the possibility to influence fixation strength and micromotion at the fracture gap. Long plates and oblique screws at the plate ends increase fixation strength. However, the number of screws does influence stiffness and stability. Lag screws and screws close to the fracture site reduce micromotion dramatically. Dynamic plate osteosynthesis can be achieved by applying some simple rules: long plates with only a few screws should be used. Oblique screws at the plate ends increase the pullout strength. Two or three holes at the fracture site should be omitted. Lag screws, especially through the plate, must be avoided whenever possible. Compression is not required. Locking plates are recommended only in fractures close to the joint. When respecting these basic concepts, dynamic plate osteosynthesis is a safe procedure with a high healing and a low complication rate. 

  14. Dynamic simulation of universal spacer in Dynesys dynamic stabilization system for human vertebra

    Institute of Scientific and Technical Information of China (English)

    Sung-Min KIM; In-Chul YANG; Seung-Yeol LEE; Sung-Youn CHO

    2009-01-01

    The aim of this study is to analyze the simulated behavior of universal spacer in Dynesys dynamic stabilization system inserted in human vertebra. Dynesys, so-called "Dynamic neutralization system for the spine", dynamic stabilization system is a new concept in the surgical treatment of lower back pain recently. Universal spacer used as flexible material is to stabilize the spine and the material property of universal spacer is polycarbonate urethane. Universal spacer may apply different kinematic behaviors at implanted level in vertebra. Spinal range of motion(SROM) of inter-vertebra with installed Dynesys dynamic stabilization system was studied using Adams+LifeMOD as simulation software package. The vertebra model was set up to closely resemble the in-vivo conditions. Inter-vertebra rotations were measured by post processor of Adams and compared with the intact values. SROMs of the flexion, extension, lateral bending, and axial rotation of human virtual models were measured, where three spinal fixation systems such as rigid system, Dynesys system, and fused system were installed. As a result, the value of SROM is decreased in flexion-extension and lateral bending when the spinal fixation system is implanted. The movement of Dynesys system is similar to that of intact model by allowing the movement of lumbar. This means that the Dynesys system is proved to be safe and effective in the treatment of unstable spinal condition.

  15. Stability of etoposide solutions in disposable infusion devices for day hospital cancer practices.

    Science.gov (United States)

    Klasen, Alison; Kessari, Romain; Mercier, Lionel; Valade, Cyril; Grill, Jacques; Desmaris, Romain; Paci, Angelo

    2014-03-01

    In a context of day hospital care of cancer patients, a protocol combining etoposide and carboplatin is used in paediatrics. Disposable infusion devices can be used to improve patient quality of life and to optimize nursing time. Stability data are available for carboplatin in these devices but not for etoposide. The aim of this study was to determine the stability of etoposide solutions in these devices by monitoring the changing etoposide concentration. To study the changing etoposide concentration, we investigated three different concentrations, each in two different solvents: sodium chloride (NaCl) 0.9 % and dextrose 5 %, in Intermate(®) disposable infusion devices. Quantitative analyses were performed by high-performance liquid chromatography coupled with ultraviolet (UV) detection on samples collected over a 24-h study period. The results showed that 100 mg/L etoposide solutions were stable for 24 h in NaCl 0.9 % and for 12 h in dextrose 5 %, whatever the temperature. The 400-mg/L solutions were stable for 24 h in both diluents, whatever the temperature, whereas the 600-mg/L solutions when diluted in NaCl 0.9 % and dextrose 5 % in water were stable for 8 and 6 h, respectively. We found that precipitation was the main phenomenon responsible for decreased etoposide concentrations. This study allowed us to conclude that etoposide solutions prepared in Intermate(®) infusion devices are stable for day hospital administration in paediatrics. It will also allow us to conduct a future clinical study that will focus on the medico-economic feasibility of this protocol and on the evaluation of patient and nurse satisfaction.

  16. The stability of liquid-filled matrix ionization chamber electronic portal imaging devices for dosimetry purposes.

    Science.gov (United States)

    Louwe, R J W; Tielenburg, R; van Ingen, K M; Mijnheer, B J; van Herk, M B

    2004-04-01

    This study was performed to determine the stability of liquid-filled matrix ionization chamber (LiFi-type) electronic portal imaging devices (EPID) for dosimetric purposes. The short- and long-term stability of the response was investigated, as well as the importance of factors influencing the response (e.g., temperature fluctuations, radiation damage, and the performance of the electronic hardware). It was shown that testing the performance of the electronic hardware as well as the short-term stability of the imagers may reveal the cause of a poor long-term stability of the imager response. In addition, the short-term stability was measured to verify the validity of the fitted dose-response curve immediately after beam startup. The long-term stability of these imagers could be considerably improved by correcting for room temperature fluctuations and gradual changes in response due to radiation damage. As a result, the reproducibility was better than 1% (1 SD) over a period of two years. The results of this study were used to formulate recommendations for a quality control program for portal dosimetry. The effect of such a program was assessed by comparing the results of portal dosimetry and in vivo dosimetry using diodes during the treatment of 31 prostate patients. The improvement of the results for portal dosimetry was consistent with the deviations observed with the reproducibility tests in that particular period. After a correction for the variation in response of the imager, the average difference between the measured and prescribed dose during the treatment of prostate patients was -0.7%+/-1.5% (1 SD), and -0.6%+/-1.1% (1 SD) for EPID and diode in vivo dosimetry, respectively. It can be concluded that a high stability of the response can be achieved for this type of EPID by applying a rigorous quality control program.

  17. Stability analysis of electrical powered wheelchair-mounted robotic-assisted transfer device

    Directory of Open Access Journals (Sweden)

    Hongwu Wang, PhD

    2014-09-01

    Full Text Available The ability of people with disabilities to live in their homes and communities with maximal independence often hinges, at least in part, on their ability to transfer or be transferred by an assistant. Because of limited resources and the expense of personal care, robotic transfer assistance devices will likely be in great demand. An easy-to-use system for assisting with transfers, attachable to electrical powered wheelchairs (EPWs and readily transportable, could have a significant positive effect on the quality of life of people with disabilities. We investigated the stability of our newly developed Strong Arm, which is attached and integrated with an EPW to assist with transfers. The stability of the system was analyzed and verified by experiments applying different loads and using different system configurations. The model predicted the distributions of the system’s center of mass very well compared with the experimental results. When real transfers were conducted with 50 and 75 kg loads and an 83.25 kg dummy, the current Strong Arm could transfer all weights safely without tip-over. Our modeling accurately predicts the stability of the system and is suitable for developing better control algorithms to enhance the safety of the device.

  18. Stability analysis of electrical powered wheelchair-mounted robotic-assisted transfer device.

    Science.gov (United States)

    Wang, Hongwu; Tsai, Chung-Ying; Jeannis, Hervens; Chung, Cheng-Shiu; Kelleher, Annmarie; Grindle, Garrett G; Cooper, Rory A

    2014-01-01

    The ability of people with disabilities to live in their homes and communities with maximal independence often hinges, at least in part, on their ability to transfer or be transferred by an assistant. Because of limited resources and the expense of personal care, robotic transfer assistance devices will likely be in great demand. An easy-to-use system for assisting with transfers, attachable to electrical powered wheelchairs (EPWs) and readily transportable, could have a significant positive effect on the quality of life of people with disabilities. We investigated the stability of our newly developed Strong Arm, which is attached and integrated with an EPW to assist with transfers. The stability of the system was analyzed and verified by experiments applying different loads and using different system configurations. The model predicted the distributions of the system's center of mass very well compared with the experimental results. When real transfers were conducted with 50 and 75 kg loads and an 83.25 kg dummy, the current Strong Arm could transfer all weights safely without tip-over. Our modeling accurately predicts the stability of the system and is suitable for developing better control algorithms to enhance the safety of the device.

  19. Electricity Market Stochastic Dynamic Model and Its Mean Stability Analysis

    Directory of Open Access Journals (Sweden)

    Zhanhui Lu

    2014-01-01

    Full Text Available Based on the deterministic dynamic model of electricity market proposed by Alvarado, a stochastic electricity market model, considering the random nature of demand sides, is presented in this paper on the assumption that generator cost function and consumer utility function are quadratic functions. The stochastic electricity market model is a generalization of the deterministic dynamic model. Using the theory of stochastic differential equations, stochastic process theory, and eigenvalue techniques, the determining conditions of the mean stability for this electricity market model under small Gauss type random excitation are provided and testified theoretically. That is, if the demand elasticity of suppliers is nonnegative and the demand elasticity of consumers is negative, then the stochastic electricity market model is mean stable. It implies that the stability can be judged directly by initial data without any computation. Taking deterministic electricity market data combined with small Gauss type random excitation as numerical samples to interpret random phenomena from a statistical perspective, the results indicate the conclusions above are correct, valid, and practical.

  20. Skipping Posterior Dynamic Transpedicular Stabilization for Distant Segment Degenerative Disease

    Directory of Open Access Journals (Sweden)

    Bilgehan Solmaz

    2012-01-01

    Full Text Available Objective. To date, there is still no consensus on the treatment of spinal degenerative disease. Current surgical techniques to manage painful spinal disorders are imperfect. In this paper, we aimed to evaluate the prospective results of posterior transpedicular dynamic stabilization, a novel surgical approach that skips the segments that do not produce pain. This technique has been proven biomechanically and radiologically in spinal degenerative diseases. Methods. A prospective study of 18 patients averaging 54.94 years of age with distant spinal segment degenerative disease. Indications consisted of degenerative disc disease (57%, herniated nucleus pulposus (50%, spinal stenosis (14.28%, degenerative spondylolisthesis (14.28%, and foraminal stenosis (7.1%. The Oswestry Low-Back Pain Disability Questionnaire and visual analog scale (VAS for pain were recorded preoperatively and at the third and twelfth postoperative months. Results. Both the Oswestry and VAS scores showed significant improvement postoperatively (P<0.05. We observed complications in one patient who had spinal epidural hematoma. Conclusion. We recommend skipping posterior transpedicular dynamic stabilization for surgical treatment of distant segment spinal degenerative disease.

  1. Dynamic blade row compression component model for stability studies

    Science.gov (United States)

    Tesch, W. A.; Steenken, W. G.

    1976-01-01

    This paper describes a generalized dynamic model which has been developed for use in compression component aerodynamic stability studies. The model is a one-dimensional, pitch-line, blade row, lumped volume system. Arbitrary placement of blade free volumes upstream, within, and downstream of the compression component as well as the removal of bleed flow from the exit of any rotor or stator are model options. The model has been applied to a two-stage fan and an eight-stage compressor. The clean inlet pressure ratio/flow maps and the surge line have been reproduced, thereby validating the capability of the dynamic model to reproduce the steady-flow characteristics of the compression component. A method for determining the onset of an aerodynamic instability which is associated with surge is described. Sinusoidally time-varying inlet and exit boundary conditions have been applied to the eight stage compressor as examples of the manner in which this model may be used for stability studies.

  2. Study on modeling of vehicle dynamic stability and control technique

    Institute of Scientific and Technical Information of China (English)

    GAO Yun-ting; LI Pan-feng

    2012-01-01

    In order to solve the problem of enhancing the vehicle driving stability and safety,which has been the hot question researched by scientific and engineering in the vehicle industry,the new control method was investigated.After the analysis of tire moving characteristics and the vehicle stress analysis,the tire model based on the extension pacejka magic formula which combined longitudinal motion and lateral motion was developed and a nonlinear vehicle dynamical stability model with seven freedoms was made.A new model reference adaptive control project which made the slip angle and yaw rate of vehicle body as the output and feedback variable in adjusting the torque of vehicle body to control the vehicle stability was designed.A simulation model was also built in Matlab/Simulink to evaluate this control project.It was made up of many mathematical subsystem models mainly including the tire model module,the yaw moment calculation module,the center of mass parameter calculation module,tire parameter calculation module of multiple and so forth.The severe lane change simulation result shows that this vehicle model and the model reference adaptive control method have an excellent performance.

  3. Cooperation Dynamics on Mobile Crowd Networks of Device-to-Device Communications

    Directory of Open Access Journals (Sweden)

    Yong Deng

    2016-01-01

    Full Text Available The explosive use of smart devices enabled the emergence of collective resource sharing among mobile individuals. Mobile users need to cooperate with each other to improve the whole network’s quality of service. By modeling the cooperative behaviors in a mobile crowd into an evolutionary Prisoner’s dilemma game, we investigate the relationships between cooperation rate and some main influence factors, including crowd density, communication range, temptation to defect, and mobility attributes. Using evolutionary game theory, our analysis on the cooperative behaviors of mobile takes a deep insight into the cooperation promotion in a dynamical network with selfish autonomous users. The experiment results show that mobile user’s features, including speed, moving probability, and reaction radius, have an obvious influence on the formation of a cooperative mobile social network. We also found some optimal status when the crowd’s cooperation rate reaches the best. These findings are important if we want to establish a mobile social network with a good performance.

  4. Dynamic stress of impeller blade of shaft extension tubular pump device based on bidirectional fluid-structure interaction

    Energy Technology Data Exchange (ETDEWEB)

    Kan, Kan; Liu, Huiwen; Yang, Chunxia [Hohai University, Nanjing (China); Zheng, Yuan [National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Nanjing (China); Fu, Shifeng; Zhang, Xin [Power China Huadong Engineering Corporation, Hangzhou (China)

    2017-04-15

    Current research on the stability of tubular pumps is mainly concerned with the transient hydrodynamic characteristics. However, the structural response under the influence of fluid-structure interaction hasn't been taken fully into consideration. The instability of the structure can cause vibration and cracks, which may threaten the safety of the unit. We used bidirectional fluid-structure interaction to comprehensively analyze the dynamic stress characteristics of the impeller blades of the shaft extension tubular pump device. Furthermore, dynamic stress of impeller blade of shaft extension tubular pump device was solved under different lift conditions of 0° blade angle. Based on Reynolds-average N-S equation and SST k-ω turbulence model, numerical simulation was carried out for three-dimensional unsteady incompressible turbulent flow field of the pump device whole flow passage. Meanwhile, the finite element method was used to calculate dynamic characteristics of the blade structure. The blade dynamic stress distribution was obtained on the basis of fourth strength theory. The research results indicate that the maximum blade dynamic stress appears at the joint between root of inlet side of the blade suction surface and the axis. Considering the influence of gravity, the fluctuation of the blade dynamic stress increases initially and decreases afterwards within a rotation period. In the meantime, the dynamic stress in the middle part of inlet edge presents larger relative fluctuation amplitude. Finally, a prediction method for dynamic stress distribution of tubular pump considering fluid-structure interaction and gravity effect was proposed. This method can be used in the design stage of tubular pump to predict dynamic stress distribution of the structure under different operating conditions, improve the reliability of pump impeller and analyze the impeller fatigue life.

  5. Improvement of a-Si:H device stability and performances by proper design of the interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Martins, R.; Ferreira, I.; Cabrita, A.; Fortunato, E. [CENIMAT, Department of Materials Science, Faculty of Sciences and Technology, New University of Lisbon and CEMOP-UNINOVA, 2825-114 Caparica (Portugal)

    2000-05-01

    This paper deals with a new design method for the interfaces of a-Si:H pin solar cells that improves the stability and performances of devices deposited in a single batch chamber process. The method consists in removing a deposited sacrificial layer placed between the p/i and/or i/n interfaces by etching. This layer is an absorber of defects and impurities that are introduced in the interfaces, mainly from the chamber walls cross-contamination and the substrate surface. The results achieved increase the device fill factor and short circuit current density, respectively towards 75% and 16.3 mA cm{sup -2}, with a final efficiency of about 10%, before light soaking experiments.

  6. Analysis of the particle stability in a new designed ultrasonic levitation device.

    Science.gov (United States)

    Baer, Sebastian; Andrade, Marco A B; Esen, Cemal; Adamowski, Julio Cezar; Schweiger, Gustav; Ostendorf, Andreas

    2011-10-01

    The use of acoustic levitation in the fields of analytical chemistry and in the containerless processing of materials requires a good stability of the levitated particle. However, spontaneous oscillations and rotation of the levitated particle have been reported in literature, which can reduce the applicability of the acoustic levitation technique. Aiming to reduce the particle oscillations, this paper presents the analysis of the particle stability in a new acoustic levitator device. The new acoustic levitator consists of a piezoelectric transducer with a concave radiating surface and a concave reflector. The analysis is conducted by determining numerically the axial and lateral forces that act on the levitated object and by measuring the oscillations of a sphere particle by a laser Doppler vibrometer. It is shown that the new levitator design allows to increase the lateral forces and reduce significantly the lateral oscillations of the levitated object.

  7. Relative Stability of Boiling of FC—72 and HFE—7100 with Applications to Electronic Device Cooling

    Institute of Scientific and Technical Information of China (English)

    Z.W.LIU; X.F.PENG; 等

    2000-01-01

    This paper investigates the relative stability between nucleate and film boiling modes of FC-72 and HFE-7100,which have potential to electronic device cooling applications.Equilibrium heat flux,qc.which refers to as an index for measuring the relative stability of boiling.Was obtained at a liquid subcooling of 0-20 K.Experimental results reveal that(1) qc increases with liquid subcooling;(2) although the FC-72 exhibits a higher critical heat flux(CHF) than does the HFE-7100,somewhat unexpectedly,the equilibrium heat flux for the latter is greater than the former,Rstated,at a prescribed heat flux,the risk to burnout for boiling of FC-72 is higher than that of HFE-7100,The shift in boiling curves interprets the experimental findings.

  8. Substrate and head group modifications for enhanced stability in molecular electronic devices

    Science.gov (United States)

    Ferrato, Michael-Anthony

    Poor Self-Assembled Monolayer (SAM) stability is a barrier which impedes the incorporation of molecular layers as functional components in electronic device architectures. Here we investigate the molecular electronic characteristics of two well established approaches to enhancing SAM stability. In Chapter 2 we investigate the electrochemical modification of Au substrates by the underpotential deposition of silver monolayers (AgUPD). In Chapter 3 we study chelating dithiophosphinic acid (DTPA) head groups to anchor SAM molecules to substrates. Based on molecular electronic characterization using EGaIn Tip testbeds, we observed that AgUPD substrates maintained the inherent electronic character of n-alkanethiolate SAMs, but reduced charge transport by almost 1 order of magnitude as compared with the same SAMs on bulk Au substrates. Similar molecular electronic characterization of (diphenyl)dithiophosphinic acid SAMs on Au substrates revealed that the DTPA head group induced a ~3 order of magnitude drop in charge transport as compared with analogous thiophenol SAMs.

  9. Intra-operative evaluation of cementless hip implant stability: a prototype device based on vibration analysis.

    Science.gov (United States)

    Lannocca, Maurizio; Varini, Elena; Cappello, Angelo; Cristofolini, Luca; Bialoblocka, Ewa

    2007-10-01

    Cementless implants are mechanically stabilized during surgery by a press-fitting procedure. Good initial stability is crucial to avoid stem loosening and bone cracking, therefore, the surgeon must achieve optimal press-fitting. A possible approach to solve this problem and assist the surgeon in achieving the optimal compromise, involves the use of vibration analysis. The present study aimed to design and test a prototype device able to evaluate the primary mechanical stability of a cementless prosthesis, based on vibration analysis. In particular, the goal was to discriminate between stable and quasi-stable implants; thus the stem-bone system was assumed to be linear in both cases. For that reason, it was decided to study the frequency responses of the system, instead of the harmonic distortion. The prototype developed consists of a piezoelectric exciter connected to the stem and an accelerometer attached to the femur. Preliminary tests were performed on four composite femurs implanted with a conventional stem. The results showed that the input signal was repeatable and the output could be recorded accurately. The most sensitive parameter to stability was the shift in resonance frequency of the stem-bone system, which was highly correlated with residual micromotion on all four specimens.

  10. FACTS Devices Using Neuro Fuzzy Controller in Stabilization of Grid Connected Wind Generator.

    Directory of Open Access Journals (Sweden)

    ROHI KACHROO

    2012-05-01

    Full Text Available Wind power is one of the renewable energy sources. It has various advantages like, cost competitiveness, environmentally clean and safeness. Large wind farms have stability problems when they are integrated to the power system. A thorough analysis is required to identify the stability problems and to develop measures to improve it. Mostly used wind generator is a fixed speed induction generator, which requires reactive power to maintain air gap flux. Reactive ower equipments are used to enable recovery of large wind farms from severe system disturbances. In this paper shunt and series FACTS evices, Static Synchronous Compensator (STATCOM and Static ynchronous Series Compensator are used for the purpose of stabilizing grid connected wind generator against the grid-side disturbances. The essential feature of the FACTS devices is their ability to absorb or inject the reactive power. Since stability is a non linear process so system performance can be improved by using nonlinear controllers. Neurofuzzy controller (NFC is a non linear controller. NFC has fasterresponse than conventional PI controllers

  11. Dynamic stability of sequential stimulus representations in adapting neuronal networks

    Directory of Open Access Journals (Sweden)

    Renato Carlos Farinha Duarte

    2014-10-01

    Full Text Available The ability to acquire and maintain appropriate representations of time-varying, sequentialstimulus events is a fundamental feature of neocortical circuits and a necessary first step towardsmore specialized information processing. The dynamical properties of such representationsdepend on the current state of the circuit, which is determined primarily by the ongoing, internallygenerated activity, setting the ground state from which input-specific transformations emerge.Here, we begin by demonstrating that timing-dependent synaptic plasticity mechanisms havean important role to play in the active maintenance of an ongoing dynamics characterized byasynchronous and irregular firing, closely resembling cortical activity in vivo. Incoming stimuli,acting as perturbations of the local balance of excitation and inhibition, require fast adaptiveresponses to prevent the development of unstable activity regimes, such as those characterizedby a high degree of population-wide synchrony. We establish a link between such pathologicalnetwork activity, which is circumvented by the action of plasticity, and a reduced computationalcapacity. Additionally, we demonstrate that the action of plasticity shapes and stabilizes thetransient network states exhibited in the presence of sequentially presented stimulus events,allowing the development of adequate and discernible stimulus representations. The mainfeature responsible for the increased discriminability of stimulus-driven population responsesin plastic networks is shown to be the decorrelating action of inhibitory plasticity and theconsequent maintenance of the asynchronous irregular dynamic regime both for ongoing activityand stimulus-driven responses, whereas excitatory plasticity is shown to play only a marginalrole.

  12. Dynamic Stabilization of Metal Oxide–Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    McBriarty, Martin E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Sciences Division; von Rudorff, Guido Falk [Univ. College London (United Kingdom). Dept. of Physics and Astronomy; Stubbs, Joanne E. [Univ. of Chicago, IL (United States). Center for Advanced Radiation Sources (CARS); Eng, Peter J. [Univ. of Chicago, IL (United States). Center for Advanced Radiation Sources (CARS); Blumberger, Jochen [Univ. College London (United Kingdom). Dept. of Physics and Astronomy; Rosso, Kevin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Sciences Division

    2017-02-08

    Metal oxide growth, dissolution, and redox reactivity depend on the structure and dynamics at the interface with aqueous solution. We present the most definitive analysis to date of the hydrated naturally abundant r-cut (11$\\bar{0}$2) termination of the iron oxide hematite (α-Fe2O3). In situ synchrotron X-ray scattering analysis reveals a ridged lateral arrangement of adsorbed water molecules hydrogen bonded to terminal aquo groups. Large-scale hybrid-functional density functional theory-based molecular dynamics (DFT-MD) simulations show how this structure is dynamically stabilized by picosecond exchange between aquo groups and adsorbed water, even under nominally dry conditions. Surface pKa prediction based on bond valence analysis suggests that water exchange may influence the proton transfer reactions associated with acid/base reactivity at the interface. Our findings rectify inconsistencies between existing models and may be extended to resolving more complex electrochemical phenomena at metal oxide-water interfaces.

  13. Real-time temperature estimation in a multiple device power electronics system subject to dynamic cooling

    OpenAIRE

    Davidson, J. N.; Stone, D. A.; Foster, M. P.; Gladwin, D.T.

    2016-01-01

    This paper presents a technique to estimate the temperature of each power electronic device in a thermally coupled, multiple device system subject to dynamic cooling. Using a demonstrator system, the thermal transfer impedance between pairs of devices is determined in the frequency domain for a quantised range of active cooling levels using a technique based on pseudorandom binary sequences. The technique is illustrated by application to the case temperatures of power devices. For each coolin...

  14. Posterior lumbar dynamic stabilization instead of arthrodesis for symptomatic adjacent-segment degenerative stenosis: description of a novel technique.

    Science.gov (United States)

    Mashaly, Hazem; Paschel, Erin E; Khattar, Nicolas K; Goldschmidt, Ezequiel; Gerszten, Peter C

    2016-01-01

    follow-up period. CONCLUSIONS The use of posterior lumbar dynamic stabilization may offer a valid and safe option for the management of patients who develop ASD rostral to a previously instrumented arthrodesis. The technique may serve as an alternative to multilevel arthrodesis in this patient population. By implanting a dynamic stabilization device instead of an extension of a rigid construct, this might translate into a reduction in the development of yet another level of ASD.

  15. 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

  16. Combined characterization techniques to understand the stability of a variety of organic photovoltaic devices : the ISOS-3 interlaboratory collaboration

    NARCIS (Netherlands)

    Lira-Cantu, M.; Tanenbaum, D.M.; Norrman, K.; Voroshazi, E.; Hermenau, M.; Lloyd, M.T.; Teran-Escobar, G.; Galagan, Y.O.; Zimmermann, B.; Hösel, M.; Dam, H.F.; Jørgensen, M.; Gevorgyan, S.; Lutsen, L.; Vanderzande, D.; Hoppe, H.; Rösch, R.; Würfel, U.; Andriessen, H.A.J.M.; Rivaton, A.; Uzunoglu, G.Y.; Germack, D.; Andreasen, B.; Madsen, M.V.; Bundgaard, E.; Krebs, F.C.

    2012-01-01

    This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPVs) devices prepared by leading research laboratories. All devices have been shipped to and degraded at the Danish Technical University (DTU, formerly

  17. ISO 12189 standard for the preclinical evaluation of posterior spinal stabilization devices--I: Assembly procedure and validation.

    Science.gov (United States)

    La Barbera, Luigi; Villa, Tomaso

    2016-02-01

    The International Standardization Organization introduced standard 12189 for the preclinical evaluation of the mechanical reliability of posterior stabilization devices. The well-known vertebrectomy model formalized in standard F1717 by the American Society for Testing and Materials was modified with the introduction of a modular anterior support made up of three calibrated springs, which allows to describe a more realistic scenario, closer to the effective clinical use, as well to test even very flexible and dynamic posterior stabilization implants. Despite these important improvements, ISO 12189 received very little attention in the literature. The aim of the work is to provide a systematic procedure for the assembly and validation of a finite element model capable of describing the experimental test according to ISO 12189. The validated finite element model is able to catch very well the effective stiffness of the unassembled and assembled constructs (percentage differences  0.75, root mean square error  0.96, root mean square error ISO 12189 standard.

  18. Dynamical stability of a many-body Kapitza pendulum

    Energy Technology Data Exchange (ETDEWEB)

    Citro, Roberta, E-mail: citro@sa.infn.it [Dipartimento di Fisica “E. R. Caianiello” and Spin-CNR, Universita’ degli Studi di Salerno, Via Giovanni Paolo II, I-84084 Fisciano (Italy); Dalla Torre, Emanuele G., E-mail: emanuele.dalla-torre@biu.ac.il [Department of Physics, Bar Ilan University, Ramat Gan 5290002 (Israel); Department of Physics, Harvard University, Cambridge, MA 02138 (United States); D’Alessio, Luca [Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Department of Physics, Boston University, Boston, MA 02215 (United States); Polkovnikov, Anatoli [Department of Physics, Boston University, Boston, MA 02215 (United States); Babadi, Mehrtash [Department of Physics, Harvard University, Cambridge, MA 02138 (United States); Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125 (United States); Oka, Takashi [Department of Applied Physics, University of Tokyo, Tokyo, 113-8656 (Japan); Demler, Eugene [Department of Physics, Harvard University, Cambridge, MA 02138 (United States)

    2015-09-15

    We consider a many-body generalization of the Kapitza pendulum: the periodically-driven sine–Gordon model. We show that this interacting system is dynamically stable to periodic drives with finite frequency and amplitude. This finding is in contrast to the common belief that periodically-driven unbounded interacting systems should always tend to an absorbing infinite-temperature state. The transition to an unstable absorbing state is described by a change in the sign of the kinetic term in the Floquet Hamiltonian and controlled by the short-wavelength degrees of freedom. We investigate the stability phase diagram through an analytic high-frequency expansion, a self-consistent variational approach, and a numeric semiclassical calculation. Classical and quantum experiments are proposed to verify the validity of our results.

  19. U32: Vehicle Stability and Dynamics: Longer Combination Vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Petrolino, Joseph [National Transportation Research Center (NTRC); Spezia, Tony [National Transportation Research Center (NTRC); Arant, Michael [Clemson University; Broshears, Eric [Auburn University, Auburn, Alabama; Chitwood, Caleb [Battelle; Colbert, Jameson [Auburn University, Auburn, Alabama; Hathaway, Richard [Western Michigan University; Keil, Mitch [Western Michigan University; LaClair, Tim J [ORNL; Pape, Doug [Battelle; Patterson, Jim [Hendrickson; Pittro, Collin [Battelle

    2011-01-01

    This study investigated the safety and stability of longer combination vehicles (LCVs), in particular a triple trailer combination behind a commercial tractor, which has more complicated dynamics than the more common tractor in combination with a single semitrailer. The goal was to measure and model the behavior of LCVs in simple maneuvers. Example maneuvers tested and modeled were single and double lane changes, a gradual lane change, and a constant radius curve. In addition to test track data collection and a brief highway test, two computer models of LCVs were developed. One model is based on TruckSim , a lumped parameter model widely used for single semitrailer combinations. The other model was built in Adams software, which more explicitly models the geometry of the components of the vehicle, in terms of compliant structural members. Among other results, the models were able to duplicate the experimentally measured rearward amplification behavior that is characteristic of multi-unit combination vehicles.

  20. Controllability, observability, realizability, and stability of dynamic linear systems

    Directory of Open Access Journals (Sweden)

    John M. Davis

    2009-03-01

    Full Text Available We develop a linear systems theory that coincides with the existing theories for continuous and discrete dynamical systems, but that also extends to linear systems defined on nonuniform time scales. The approach here is based on generalized Laplace transform methods (e.g. shifts and convolution from the recent work [13]. We study controllability in terms of the controllability Gramian and various rank conditions (including Kalman's in both the time invariant and time varying settings and compare the results. We explore observability in terms of both Gramian and rank conditions and establish related realizability results. We conclude by applying this systems theory to connect exponential and BIBO stability problems in this general setting. Numerous examples are included to show the utility of these results.

  1. Controllability, Observability, Reachability, and Stability of Dynamic Linear Systems

    CERN Document Server

    Jackson, Billy J; Gravagne, Ian A; Marks, Robert J

    2009-01-01

    We develop a linear systems theory that coincides with the existing theories for continuous and discrete dynamical systems, but that also extends to linear systems defined on nonuniform time domains. The approach here is based on generalized Laplace transform methods (e.g. shifts and convolution) from our recent work \\cite{DaGrJaMaRa}. We study controllability in terms of the controllability Gramian and various rank conditions (including Kalman's) in both the time invariant and time varying settings and compare the results. We also explore observability in terms of both Gramian and rank conditions as well as realizability results. We conclude by applying this systems theory to connect exponential and BIBO stability problems in this general setting. Numerous examples are included to show the utility of these results.

  2. Carotenoid incorporation into microsomes: yields, stability and membrane dynamics

    Science.gov (United States)

    Socaciu, Carmen; Jessel, Robert; Diehl, Horst A.

    2000-12-01

    The carotenoids β-carotene (BC), lycopene (LYC), lutein (LUT), zeaxanthin (ZEA), canthaxanthin (CTX) and astaxanthin (ASTA) have been incorporated into pig liver microsomes. Effective incorporation concentrations in the range of about 1-6 nmol/mg microsomal protein were obtained. A stability test at room temperature revealed that after 3 h BC and LYC had decayed totally whereas, gradually, CTX (46%), LUT (21%), ASTA (17%) and ZEA (5%) decayed. Biophysical parameters of the microsomal membrane were changed hardly by the incorporation of carotenoids. A small rigidification may occur. Membrane anisotropy seems to offer only a small tolerance for incorporation of carotenoids and seems to limit the achievable incorporation concentrations of the carotenoids into microsomes. Microsomes instead of liposomes should be preferred as a membrane model to study mutual effects of carotenoids and membrane dynamics.

  3. Dynamic Stability Analysis Using High-Order Interpolation

    Directory of Open Access Journals (Sweden)

    Juarez-Toledo C.

    2012-10-01

    Full Text Available A non-linear model with robust precision for transient stability analysis in multimachine power systems is proposed. The proposed formulation uses the interpolation of Lagrange and Newton's Divided Difference. The High-Order Interpolation technique developed can be used for evaluation of the critical conditions of the dynamic system.The technique is applied to a 5-area 45-machine model of the Mexican interconnected system. As a particular case, this paper shows the application of the High-Order procedure for identifying the slow-frequency mode for a critical contingency. Numerical examples illustrate the method and demonstrate the ability of the High-Order technique to isolate and extract temporal modal behavior.

  4. Molecular dynamics simulation of thermal stability of nanocrystalline vanadium

    Institute of Scientific and Technical Information of China (English)

    WEI; Mingzhi; XIAO; Shifang; YUAN; Xiaojian; HU; Wangyu

    2006-01-01

    The microstructure and thermal stability of nanocrystalline vanadium with an average grain size ranging from 2.86 to 7.50 nm are calculated by means of the analytic embedded-atom method and molecular dynamics. The grain boundary and nanocrystalline grain atoms are differentiated by the common neighbor analysis method. The results indicate that the fraction of grain boundary increases with the grain size decreasing, and the mean energy of atoms is higher than that of coarse crystals. The thermal-stable temperatures of nanocrystalline vanadium are determined from the evolution of atomic energy, fraction of grain boundary and radial distribution function. It is shown that the stable temperature decreases obviously with the grain size decreasing. In addition the reasons which cause the grain growth of nanocrystalline vanadium are discussed.

  5. Suction-recirculation device for stabilizing particle flows within a solar powered solid particle receiver

    Science.gov (United States)

    Kolb, Gregory J [Albuquerque, NM

    2012-02-07

    A suction-recirculation device for stabilizing the flow of a curtain of blackened heat absorption particles falling inside of a solar receiver with an open aperture. The curtain of particles absorbs the concentrated heat from a solar mirror array reflected up to the receiver on a solar power tower. External winds entering the receiver at an oblique angle can destabilize the particle curtain and eject particles. A fan and ductwork is located behind the back wall of the receiver and sucks air out through an array of small holes in the back wall. Any entrained particles are separated out by a conventional cyclone device. Then, the air is recirculated back to the top of the receiver by injecting the recycled air through an array of small holes in the receiver's ceiling and upper aperture front wall. Since internal air is recirculated, heat losses are minimized and high receiver efficiency is maintained. Suction-recirculation velocities in the range of 1-5 m/s are sufficient to stabilize the particle curtain against external wind speeds in excess of 10 m/s.

  6. Stability properties of elementary dynamic models of membrane transport.

    Science.gov (United States)

    Hernández, Julio A

    2003-01-01

    Living cells are characterized by their capacity to maintain a stable steady state. For instance, cells are able to conserve their volume, internal ionic composition and electrical potential difference across the plasma membrane within values compatible with the overall cell functions. The dynamics of these cellular variables is described by complex integrated models of membrane transport. Some clues for the understanding of the processes involved in global cellular homeostasis may be obtained by the study of the local stability properties of some partial cellular processes. As an example of this approach, I perform, in this study, the neighborhood stability analysis of some elementary integrated models of membrane transport. In essence, the models describe the rate of change of the intracellular concentration of a ligand subject to active and passive transport across the plasma membrane of an ideal cell. The ligand can be ionic or nonionic, and it can affect the cell volume or the plasma membrane potential. The fundamental finding of this study is that, within the physiological range, the steady states are asymptotically stable. This basic property is a necessary consequence of the general forms of the expressions employed to describe the active and passive fluxes of the transported ligand.

  7. Dynamic-Stability Characteristics of Premixed Methane Oxy-Combustion

    KAUST Repository

    Shroll, Andrew P.

    2012-01-01

    This work explores the dynamic stability characteristics of premixed CH 4/O 2/CO 2 mixtures in a 50 kW swirl stabilized combustor. In all cases, the methane-oxygen mixture is stoichiometric, with different dilution levels of carbon dioxide used to control the flame temperature (T ad). For the highest T ad\\'s, the combustor is unstable at the first harmonic of the combustor\\'s natural frequency. As the temperature is reduced, the combustor jumps to fundamental mode and then to a low-frequency mode whose value is well below the combustor\\'s natural frequency, before eventually reaching blowoff. Similar to the case of CH 4/air mixtures, the transition from one mode to another is predominantly a function of the T ad of the reactive mixture, despite significant differences in laminar burning velocity and/or strained flame consumption speed between air and oxy-fuel mixtures for a given T ad. High speed images support this finding by revealing similar vortex breakdown modes and thus similar turbulent flame geometries that change as a function of flame temperature. Copyright © 2012 American Society of Mechanical Engineers.

  8. Switch-on dynamics of nanocavity laser devices

    DEFF Research Database (Denmark)

    Lorke, Michael; Nielsen, Torben Roland; Mørk, Jesper

    2011-01-01

    Theoretical investigations of the switch-on behavior of semiconductor quantum dot based nanocavity laser devices are presented. From a microscopic treatment of the carrier-carrier and carrier-photon interaction, we find a fast switch-on of the laser device that is enabled by ultrafast carrier...

  9. Stability Analysis of DC Distribution Systems with Droop-Based Charge Sharing on Energy Storage Devices

    Directory of Open Access Journals (Sweden)

    Despoina I. Makrygiorgou

    2017-03-01

    Full Text Available Direct current (DC distribution systems and DC microgrids are becoming a reliable and efficient alternative energy system, compatible with the DC nature of most of the distributed energy resources (DERs, storage devices and loads. The challenging problem of redesigning an autonomous DC-grid system in view of using energy storage devices to balance the power produced and absorbed, by applying simple decentralized controllers on the electronic power interfaces, is investigated in this paper. To this end, a complete nonlinear DC-grid model has been deployed that includes different DC-DERs, two controlled parallel battery branches, and different varying DC loads. Since many loads in modern distribution systems are connected through power converters, both constant power loads and simple resistive loads are considered in parallel. Within this system, suitable cascaded controllers on the DC/DC power converter interfaces to the battery branches are proposed, in a manner that ensures stability and charge sharing between the two branches at the desired ratio. To achieve this task, inner-loop current controllers are combined with outer-loop voltage, droop-based controllers. The proportional-integral (PI inner-loop current controllers include damping terms and are fully independent from the system parameters. The controller scheme is incorporated into the system model and a globally valid nonlinear stability analysis is conducted; this differs from small-signal linear methods that are valid only for specific systems, usually via eigenvalue investigations. In the present study, under the virtual cost of applying advanced Lyapunov techniques on the entire nonlinear system, a rigorous analysis is formulated to prove stability and convergence to the desired operation, regardless of the particular system characteristics. The theoretical results are evaluated by detailed simulations, with the system performance being very satisfactory.

  10. Applications of Computational Methods for Dynamic Stability and Control Derivatives

    Science.gov (United States)

    Green, Lawrence L.; Spence, Angela M.

    2004-01-01

    Initial steps in the application o f a low-order panel method computational fluid dynamic (CFD) code to the calculation of aircraft dynamic stability and control (S&C) derivatives are documented. Several capabilities, unique to CFD but not unique to this particular demonstration, are identified and demonstrated in this paper. These unique capabilities complement conventional S&C techniques and they include the ability to: 1) perform maneuvers without the flow-kinematic restrictions and support interference commonly associated with experimental S&C facilities, 2) easily simulate advanced S&C testing techniques, 3) compute exact S&C derivatives with uncertainty propagation bounds, and 4) alter the flow physics associated with a particular testing technique from those observed in a wind or water tunnel test in order to isolate effects. Also presented are discussions about some computational issues associated with the simulation of S&C tests and selected results from numerous surface grid resolution studies performed during the course of the study.

  11. Dynamic Stabilization of Metal Oxide–Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    McBriarty, Martin E.; von Rudorff, Guido Falk; Stubbs, Joanne E.; Eng, Peter J.; Blumberger, Jochen; Rosso, Kevin M.

    2017-02-08

    The interaction of water with metal oxide surfaces plays a crucial role in the catalytic and geochemical behavior of metal oxides. In a vast majority of studies, the interfacial structure is assumed to arise from a relatively static lowest energy configuration of atoms, even at room temperature. Using hematite (α-Fe2O3) as a model oxide, we show through a direct comparison of in situ synchrotron X-ray scattering with density functional theory-based molecular dynamics simulations that the structure of the (1102) termination is dynamically stabilized by picosecond water exchange. Simulations show frequent exchanges between terminal aquo groups and adsorbed water in locations and with partial residence times consistent with experimentally determined atomic sites and fractional occupancies. Frequent water exchange occurs even for an ultrathin adsorbed water film persisting on the surface under a dry atmosphere. The resulting time-averaged interfacial structure consists of a ridged lateral arrangement of adsorbed water molecules hydrogen bonded to terminal aquo groups. Surface pKa prediction based on bond valence analysis suggests that water exchange will influence the proton-transfer reactions underlying the acid/base reactivity at the interface. Our findings provide important new insights for understanding complex interfacial chemical processes at metal oxide–water interfaces.

  12. The Interspinous Spacer: A New Posterior Dynamic Stabilization Concept for Prevention of Adjacent Segment Disease

    Directory of Open Access Journals (Sweden)

    Antoine Nachanakian

    2013-01-01

    Full Text Available Introduction. Posterior Dynamic stabilization using the interspinous spacer device is a known to be used as an alternative to rigid fusion in neurogenic claudication patients in the absence of macro instability. Actually, it plays an important in the management of adjacent segment disease in previously fused lumbar spine. Materials and Method. We report our experience with posterior dynamic stabilization using an interspinous spacer. 134 cases performed in our institution between September 2008 and August 2012 with different lumbar spine pathologies. The ages of our patients were between 40 and 72 years, with a mean age of 57 years. After almost 4 years of follow up in our patient and comparing their outcome to our previous serious we found that in some case the interspinous distracter has an important role not only in the treatment of adjacent segment disease but also in its prevention. Results and Discussion. Clinical improvement was noted in ISD-treated patients, with high satisfaction rate. At first, radicular pain improves with more than 3/10 reduction of the mean score on visual analog scale (VAS. In addition, disability score as well as disc height and lordotic angle showed major improvement at 3 to 6 months post operatively. And, no adjacent segment disease was reported in the patient operated with interspinous spacer. Conclusion. The interspinous spacer is safe and efficient modality to be used not only as a treatment of adjacent segment disease but also as a preventive measure in patients necessitating rigid fusion.

  13. Flexibility and electrical stability of polyester-based device electrodes under monotonic and cyclic buckling conditions

    Energy Technology Data Exchange (ETDEWEB)

    Potoczny, G.A. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, B15 2TT Birmingham (United Kingdom); Bejitual, T.S. [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, 26506, West Virginia (United States); Abell, J.S. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, B15 2TT Birmingham (United Kingdom); Sierros, K.A. [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, 26506, West Virginia (United States); Cairns, D.R., E-mail: Darran.Cairns@mail.wvu.edu [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, 26506, West Virginia (United States); Kukureka, S.N. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, B15 2TT Birmingham (United Kingdom)

    2013-01-01

    The flexibility and electrical stability of highly conductive and transparent amorphous indium tin oxide (a-ITO) films coated on polyethylene terephthalate and polyethylene naphthalate substrates were investigated by buckling tests with in situ monitoring of the electrical resistance. Monotonic and cyclic loading tests of the ITO/polymer systems were conducted. The results show that monotonic buckling in tension is more critical for electromechanical stability of ITO films than in compression (an increase in electrical resistance was observed at a critical radius of curvature, of ∼ 3 and ∼ 1 mm, respectively for both cases investigated). In contrast, cyclic loading tests show that the compression mode is more critical than the tensile mode which may be a result of the residual stress present in the film structure. Failure of the ITO film was caused by buckling-driven delamination observed using scanning electron microscopy after the tests. The presence of residual stress could mean that buckling-driven delamination is the dominant failure mode for ITO/polymer systems under repeated flexing. In general, comparable electromechanical stability was observed in both cases. Investigating the electromechanical response of such material systems is important for polymer substrate selection and life-time prediction of flexible polyester-based electronic devices. - Highlights: ► Cyclic buckling investigation of flexible electrodes. ► Importance of ITO surface compression mode as opposed to tension. ► Role of ITO residual stresses on controlled buckling investigations.

  14. Silicon multi-nanochannel FETs to improve device uniformity/stability and femtomolar detection of insulin in serum.

    Science.gov (United States)

    Regonda, Suresh; Tian, Ruhai; Gao, Jinming; Greene, Serena; Ding, Jiahuan; Hu, Walter

    2013-07-15

    Here we demonstrate the use of multiple Si nanochannel (NC) or nanograting (NG) instead of the conventional single nanochannel or nanowire design in biosensors. The NG devices can significantly reduce device-to-device variation, and improve device performance, e.g. higher current, higher ON/OFF ratio, smaller subthreshold slope, lower threshold voltage Vt in buffer solution. NG devices also result in higher sensor stability in buffer and diluted human serum. We believe such improvements are due to reduced discrete dopant fluctuation in the Si nanowires and biochemical noise in the solution because of the multiple-channel design. The improved devices allow us to sense pH linearly with 3-aminopropyltriethoxysilane coated devices, and to selectively detect insulin with limit of detection down to 10 fM in both buffer solution and diluted human serum without pre-purification.

  15. More stability and robustness with the multi-loop control solution for dynamic voltage restorer (DVR

    Directory of Open Access Journals (Sweden)

    Abdelkhalek Othmane

    2009-01-01

    Full Text Available This paper presents the application of dynamic voltage restorers (DVR on power distribution systems for mitigation of voltage sags/swells at critical loads. DVR is one of the compensating types of custom power devices. An adequate modeling and simulation of DVR, including controls in MATLAB, based on forced-commutated voltage source converter (VSC, has been proved suitable for compensating the voltage sags/swells. In this paper, a double loop control method is proposed for the improvement of the stability of DVR during the load current variation. For the main loop (Outer Voltage Loop, we use a PI controller for the regulation of the filter condenser voltage. The second loop (Inner Current Loop also uses a PI controller to control the disturbances current during load variation. Simulation results are presented to illustrate and understand the performances of DVR in the compensation of voltage sags/swell even with variation load condition.

  16. The Dynamic Stabilizing Innersole System (DSIS): the management of hyperpronation in children.

    Science.gov (United States)

    Jay, R M; Schoenhaus, H D; Seymour, C; Gamble, S

    1995-01-01

    In a study of 50 children, the Dynamic Stabilizing Innersole System (DSIS) was found to decrease the mean resting calcaneal stance position (RCSP) by an average of 6 degrees. A comparison between the neutral calcaneal stance position and the RCSP with the DSIS showed no statistically significant difference between the means for the right or left foot, indicating that the DSIS is capable of returning severe flat foot deformities to their neutral calcaneal stance position. The RCSP with and without the DSIS differed significantly, indicating that the DSIS provides a considerable and statistically significant amount of correction in the RCSP in our study population. Furthermore, the results of linear regression showed that the DSIS appears to be sensitive to the severity of the deformity, preventing overcorrection of less severe flatfoot deformities and providing a long awaited alternative to traditional pediatric corrective flatfoot devices.

  17. Exercise of mechanisms of dynamic stability improves the stability state after an unexpected gait perturbation in elderly.

    Science.gov (United States)

    Bierbaum, Stefanie; Peper, Andreas; Arampatzis, Adamantios

    2013-10-01

    Unexpected changes during gait challenge elderly individuals to a greater degree than young adults. However, the adaptive potential of elderly seems to be retained, and therefore, the training of the mechanisms of dynamic stability as well as muscle strength training may improve the dynamic stability after unexpected perturbations. Thirty-eight subjects (65-75 years) participated in the study, divided into two experimental groups (stability training group, ST, n = 14 and mixed training group, MT, n = 14) and a control group (CG, n = 10). Both experimental groups performed exercises which focused on the mechanisms of dynamic stability. Additionally, the MT group executed a training to improve muscle strength. Session volume and duration were equal for both groups (14 weeks, twice a week, ~1.5 h per session). Pre- and post-intervention, subjects performed a gait protocol with an induced unexpected perturbation. Post-intervention, the margin of stability was significantly increased after the unexpected perturbation in the ST group, indicating an improvement in stability state (pre, -30.3 ± 5.9 cm; post, -24.1 ± 5.2 cm). Further, both intervention groups increased their base of support after the intervention to regain balance after gait perturbation, whereas only the ST group showed a statistically significant improvement (STpre, 90.9 ± 6.6 cm, STpost, 98.2 ± 8.5 cm; MTpre, 91.4 ± 6.2 cm; MTpost, 97.9 ± 12.7 cm). The CG showed no differences between pre- and post-measurements. The exercise of the mechanisms of dynamic stability led to a better application of these mechanisms after an unexpected perturbation during gait. We suggest that the repeated exercise of the mechanisms of dynamic stability contributes to significant improvements in postural stability. Additional strength training for healthy elderly individuals, however, shows no further effect on the ability to recover balance after unexpected perturbations during gait.

  18. The ISOS-3 inter-laboratory collaboration focused on the stability of a variety of organic photovoltaic devices

    DEFF Research Database (Denmark)

    Tanenbaum, David M.; Hermenau, Martin; Voroshazi, Eszter;

    2012-01-01

    Seven distinct sets (n ¢ 12) of state of the art organic photovoltaic devices were prepared by leading research laboratories in a collaboration planned at the Third International Summit on Organic Photovoltaic Stability (ISOS-3). All devices were shipped to RISØ DTU and characterized simultaneously...... experiment both to provide an assessment of the homogeneity of the samples and to distribute samples for a variety of post soaking analytical measurements at six distinct laboratories enabling comparison at various stages in the degradation of the devices. Over 100 devices with more than 300 cells were used...

  19. Fixed vs dynamic plate complications following multilevel anterior cervical corpectomy and fusion with posterior stabilization.

    Science.gov (United States)

    Epstein, N E

    2003-07-01

    Comparison of fixed vs dynamic plate complications in cervical surgery. : New York, USA. Anterior cervical plate-related complications were evaluated following 66 anterior cervical corpectomy and fusion (ACF) with posterior stabilization (PWF) procedures performed in patients with ossification of the posterior longitudinal ligament (OPLL). Clinical data were comparable for both patient populations. Patients averaged between 52 and 53 years of age. The male to female ratio was approximately 2:1. Surgery addressed MR and CT documented multilevel OPLL in all patients accompanied by spondylosis and stenosis. Preoperatively average Nurick Grades ranged from 3.6 to 3.7. Anterior cervical corpectomies included an average of 2.6-3.0 vertebral bodies, while PWF covered seven levels. Fixed plates were applied in the initial 38 patients, while the latter 28 patients had dynamic plates (ABC, Aesculap, Tuttlingen, Germany) applied. Halo devices were used until fusion was documented on both X-ray and 2D-CT studies. Patients were followed-up for an average of 5.4 years in the fixed-plated groups, and 2.7 years in the dynamic-plated population. CT and dynamic X-ray confirmed that fusion occurred an average of 4.5-4.9 months postoperatively. Five (13%) fixed plates (Medtronic, Sofamor Danek, Memphis, TN, USA) failed warranting secondary surgery, while only one (3.6%) dynamic-plated patient developed a pseudarthrosis and required secondary posterior fusion. Higher failure rates follow multilevel ACF as compared with anterior diskectomy and fusion required to resect multilevel OPLL. Vaccaro et al observed a 9% failure rate following two-level ACFs and 50% failure rate following three-level ACFs performed with fixed plates. In this series, the plate extrusion rate was reduced to 3.6% when dynamic plates were applied.

  20. In vitro stability and compatibility of tenecteplase in central venous access devices.

    Science.gov (United States)

    Lentz, Yvonne K; Joyce, Michael; Lam, Xanthe

    2011-04-01

    Central venous access devices (CVADs) aid in the delivery of nutritional support, infusion therapy, and hemodialysis. Maintaining continuous flow through these devices is challenging, because they are susceptible to complications such as thrombi occlusion. Therefore, CVADs may require treatment with anticoagulant or thrombolytic agents. Using these agents as locking solutions has been widely investigated; however, few publications have described the compatibility of the therapeutic with the CVAD itself. The objective of this investigation was to evaluate the in vitro stability and compatibility of a thrombolytic biologic agent, tenecteplase, with various CVAD materials. Tenecteplase was reconstituted to 1 mg/mL with either sterile water for injection or bacteriostatic water for injection (0.9% benzyl alcohol) then incubated in glass vials, polysulfone/silicone vascular access ports, and polyurethane or silicone catheters for up to 96 hours. Biochemical assays including protein monomer, protein one-chain, and in vitro bioactivity were used to assess tenecteplase's compatibility with the investigated diluents and materials every 24 hours. Antimicrobial testing was also performed for up to 28 days on bacteriostatic water for injection-reconstituted samples only. Our results showed tenecteplase to be compatible with both types of diluents (in glass vials) and catheters for up to 72 hours. Furthermore, tenecteplase was compatible with the polysulfone/silicone vascular access ports for up to 24 hours. Finally, bacteriostatic water for injection-reconstituted tenecteplase effectively met USP criteria for the inhibition of growth of micro-organisms. This study serves as an example of a best practice to evaluate the in vitro stability and compatibility of a biologic agent with CVAD materials.

  1. Dynamic Stability and Gravitational Balancing of Multiple Extended Bodies

    Science.gov (United States)

    Quadrelli, Marco

    2008-01-01

    Feasibility of a non-invasive compensation scheme was analyzed for precise positioning of a massive extended body in free fall using gravitational forces influenced by surrounding source masses in close proximity. The N-body problem of classical mechanics is a paradigm used to gain insight into the physics of the equivalent N-body problem subject to control forces. The analysis addressed how a number of control masses move around the proof mass so that the proof mass position can be accurately and remotely compensated when exogenous disturbances are acting on it, while its sensitivity to gravitational waves remains unaffected. Past methods to correct the dynamics of the proof mass have considered active electrostatic or capacitive methods, but the possibility of stray capacitances on the surfaces of the proof mass have prompted the investigation of other alternatives, such as the method presented in this paper. While more rigorous analyses of the problem should be carried out, the data show that, by means of a combined feedback and feed-forward control approach, the control masses succeeded in driving the proof mass along the specified trajectory, which implies that the proof mass can, in principle, be balanced via gravitational forces only while external perturbations are acting on it. This concept involves the dynamic stability of a group of massive objects interacting gravitationally under active control, and can apply to drag-free control of spacecraft during missions, to successor gravitational wave space borne sensors, or to any application requiring flying objects to be precisely controlled in position and attitude relative to another body via gravitational interactions only.

  2. Sufficient Conditions for Dynamical Output Feedback Stabilization Via the Circle Criterion

    OpenAIRE

    2003-01-01

    This paper suggests sufficient conditions for asymptotically stable dynamical output feedback controller design based on the circle criterion. It is shown that a dynamic output feedback stabilization problem with impending problems of finite escape time, previously attacked by observer-based design, can be successfully solved using circle criterion design. Stability of the closed-loop system is global and robust to parameter uncertainty.

  3. Dynamical Properties of QD-based Nanolaser Devices

    DEFF Research Database (Denmark)

    Lorke, Michael; Nielsen, Torben Roland; Mørk, Jesper

    2011-01-01

    We investigate the switch-on behavior of semiconductor QD-based nanocavity laser devices. From a microscopic treatment of the carrier-carrier and carrier-photon interaction, we find a fast switch-on, that is accompanied by heavily damped relaxation oscillations and caused by an ultrafast carrier...

  4. Stabilization and control of quad-rotor helicopter using a smartphone device

    Science.gov (United States)

    Desai, Alok; Lee, Dah-Jye; Moore, Jason; Chang, Yung-Ping

    2013-01-01

    In recent years, autonomous, micro-unmanned aerial vehicles (micro-UAVs), or more specifically hovering micro- UAVs, have proven suitable for many promising applications such as unknown environment exploration and search and rescue operations. The early versions of UAVs had no on-board control capabilities, and were difficult for manual control from a ground station. Many UAVs now are equipped with on-board control systems that reduce the amount of control required from the ground-station operator. However, the limitations on payload, power consumption and control without human interference remain the biggest challenges. This paper proposes to use a smartphone as the sole computational device to stabilize and control a quad-rotor. The goal is to use the readily available sensors in a smartphone such as the GPS, the accelerometer, the rate-gyros, and the camera to support vision-related tasks such as flight stabilization, estimation of the height above ground, target tracking, obstacle detection, and surveillance. We use a quad-rotor platform that has been built in the Robotic Vision Lab at Brigham Young University for our development and experiments. An Android smartphone is connected through the USB port to an external hardware that has a microprocessor and circuitries to generate pulse-width modulation signals to control the brushless servomotors on the quad-rotor. The high-resolution camera on the smartphone is used to detect and track features to maintain a desired altitude level. The vision algorithms implemented include template matching, Harris feature detector, RANSAC similarity-constrained homography, and color segmentation. Other sensors are used to control yaw, pitch, and roll of the quad-rotor. This smartphone-based system is able to stabilize and control micro-UAVs and is ideal for micro-UAVs that have size, weight, and power limitations.

  5. ISOS-3 Inter-Laboratory Collaboration Focused on the Stability of a Variety of Organic Photovoltaic Devices

    Energy Technology Data Exchange (ETDEWEB)

    Tanenbaum, D. M.; Hermenau, M.; Voroshazi, E.; Lloyd, M. T.; Galagan, Y.; Zimmermann, B.; Hosel, M.; Dam, H. F.; Jrgensen, M.; Gevorgyan, S. A.; Kudret, S.; Maes, W.; Lutsen, L.; Vanderzande, D.; Wurfel, U.; Andriessen, R.; Rosch, R.; Hoppe, H.; Teran-Escobar, G.; Lira-Cantu, M.

    2012-02-07

    Seven distinct sets (n {>=} 12) of state of the art organic photovoltaic devices were prepared by leading research laboratories in a collaboration planned at the Third International Summit on Organic Photovoltaic Stability (ISOS-3). All devices were shipped to RISO DTU and characterized simultaneously up to 1830 h in accordance with established ISOS-3 protocols under three distinct illumination conditions: accelerated full sun simulation; low level indoor fluorescent lighting; and dark storage with daily measurement under full sun simulation. Three nominally identical devices were used in each experiment both to provide an assessment of the homogeneity of the samples and to distribute samples for a variety of post soaking analytical measurements at six distinct laboratories enabling comparison at various stages in the degradation of the devices. Over 100 devices with more than 300 cells were used in the study. We present here design and fabrication details for the seven device sets, benefits and challenges associated with the unprecedented size of the collaboration, characterization protocols, and results both on individual device stability and uniformity of device sets, in the three illumination conditions.

  6. Stability Diagrams of Triple-Dot Single-Electron Device with Single Common Gate

    Science.gov (United States)

    Imai, Shigeru

    2011-03-01

    Triple-dot single-electron devices with a single common gate have been studied. The overall stability diagram of the single-electron device with a homogeneous tunnel capacitance Cj and a homogeneous gate capacitance Cg is derived algebraically. If the set of excess electron numbers in the three islands (n1, n2, n3) is (n, n, n), (n, n + 1, n), or (n, n - 1, n), where n is an arbitrary integer, the corresponding stability region S(n1, n2, n3) exists for any Cg/Cj. S(n, n, n), S(n, n + 1, n), and S(n, n - 1, n) for all n are arranged along the Vg axis in the order of n1 + n2 + n3, where Vg is gate voltage, and neighboring stability regions overlap for any Cg/Cj ratio. Overlaps between S(n, n, n) and S(n, n ±1, n) for all n have identical kite-like shapes. Overlaps between S(n, n + 1, n) and S(n + 1, n, n + 1) for all n have identical rhombus shapes. Turnstile operations are possible by alternating gate voltage around overlaps between S(n, n, n) and S(n, n ±1, n) and around overlaps between S(n, n + 1, n) and S(n + 1, n, n + 1), though the sequences of single-electron transfers are different. The range of drain voltage and the swing of gate voltage for turnstile operation are estimated. The overlap between S(n, n + 1, n) and S(n + 1, n, n + 1) seems superior to the overlap between S(n, n, n) and S(n, n ±1, n) because of the larger ratio of the drain voltage range to the gate voltage swing, though the overlap between S(n, n + 1, n) and S(n + 1, n, n + 1) might require higher reliability against the nonuniformity of gate capacitances.

  7. Outcomes and radiographs changes of lumbar degeneration disease treated by dynamic stabilization device%非融合固定技术治疗腰椎退行性疾病的临床疗效和影像学分析

    Institute of Scientific and Technical Information of China (English)

    张乐辉; 王炳强; 李东; 李锦军; 苏楠; 杨雍

    2010-01-01

    目的 探讨一种非融合固定技术--腰椎棘突间动态稳定系统(简称Wallis系统)治疗腰椎退行性疾病的临床疗效和影像学分析.方法 2008年2月-2010年1月因腰椎间盘突出症、腰椎管狭窄症行腰椎后路Wallis固定术,通过随访进行分析研究.结果 随访患者平均住院时间23.59 d,手术时间3.00 h,出血量平均225.56 mL,术前JOA评分13.93分;随访时26.69分,二者有显著性差异.术后改善率83.7%.患者腰椎前凸保持良好,术前病变节段腰椎活动度平均5.22°,随访时平均2.44°,二者有显著性差异.术前病变节段后伸平均3.32°,术后随访时平均1.39°,二者有显著性差异.Wallis植入后病变节段上一位节段术前平均活动度为3.68°,术后随访时6.54°,二者有显著性差异.术前后伸平均1.95°,随访时平均后伸3.95°,二者有显著差异.结论 腰椎后路减压+Wallis非融合固定术治疗腰椎退行性疾病手术安全,术后疗效肯定.术后病变节段活动度减少,特别是后伸活动限制更明显,前屈则无明显限制.术后上一位临近节段活动代偿增加,后伸增加更显著.%Objective To observe the clinical therapeutic outcomes and the radiographs changes of lumbar degeneration disease treated by dynamic stabilization device (Wallis). Methods Eighty-four cases of lumbar degeneration disease were treated by threaded fusion cage, from May 1997 to May 2002. The JOA scores, the rate of fusion,cage sink and adjacent segment degeneration were observed. Results The average hospitalizotion was 23.59 days. The mean operation time was 3.00 hours. The mean JOA scores were 13.93 before the operation,while 26.69 on the end of the following time respectively; there was statistical significant. The mean motion of operative segment was 5.22 before operation, while 2.44 on the end of the following time respectively. The mean extension of operative segment was 3.32 before operation ,while 1.39 on the end of the following

  8. Successful retrieval of a Figulla Occlutech septal occluder - embolized device stability and potential solutions

    Directory of Open Access Journals (Sweden)

    Masood Sadiq

    2016-01-01

    We report a case of an atrial septal defect where a Figulla Occlutech device embolized into the right ventricle. As this device has no left atrial hub, we brought the bare device into the inferior vena cava and used a novel two-snare technique to slenderize the device into the sheath. This report highlights additional tips in transcatheter device retrieval.

  9. Ultrafast dynamics in semiconductor optical amplifiers and all-optical processing: Bulk versus quantum dot devices

    DEFF Research Database (Denmark)

    Mørk, Jesper; Berg, Tommy Winther; Magnúsdóttir, Ingibjörg

    2003-01-01

    We discuss the dynamical properties of semiconductor optical amplifiers and the importance for all-optical signal processing. In particular, the dynamics of quantum dot amplifiers is considered and it is suggested that these may be operated at very high bit-rates without significant patterning...... effects, as opposed to quantum well or bulk devices....

  10. Dynamics and stability of divertor detachment in H-mode plasmas on JET

    Science.gov (United States)

    Field, A. R.; Balboa, I.; Drewelow, P.; Flanagan, J.; Guillemaut, C.; Harrison, J. R.; Huber, A.; Huber, V.; Lipschultz, B.; Matthews, G.; Meigs, A.; Schmitz, J.; Stamp, M.; Walkden, N.; contributors, JET

    2017-09-01

    The dynamics and stability of divertor detachment in {{{N}}}2 seeded, type-I, ELMy H-mode plasmas with dominant NBI heating in the JET ITER-like wall device is studied by means of an integrated analysis of diagnostic data from several systems, classifying data relative to the ELM times. It is thereby possible to study the response of the detachment evolution to the control parameters (SOL input power, upstream density and impurity fraction) prevailing during the inter-ELM periods and the effect of ELMs on the detached divertor. A relatively comprehensive overview is achieved, including the interaction with the targets at various stages of the ELM cycle, the role of ELMs in affecting the detachment process and the overall performance of the scenario. The results are consistent with previous studies in devices with an ITER-like, metal wall, with the important advance of distinguishing data from intra- and inter-ELM periods. Operation without significant degradation of the core confinement can be sustained in the presence of strong radiation from the x-point region (MARFE).

  11. Remarks on stability of the rotating shallow-water vortices in the frontal dynamics regime

    Energy Technology Data Exchange (ETDEWEB)

    Jelloul, M.B.; Zeitlin, V. [P. et M. Curie Univ., Paris (France). Lab. de Meteorologie Dynamique

    1999-12-01

    Stability properties of large-scale strongly nonlinear isolated vortices in the rotating shallow water on the f-plane are analysed. Working first in the framework of the balanced frontal dynamics equations, the authors demonstrate that vortices of arbitrary sign with monotonous profiles of the free-surface elevation are formally stable and establish criteria for nonlinear stability. Stability in the framework of the full rotating shallow-water equations is also discussed and a conditional stability criterion is obtained.

  12. Asymptotic Stability and Balanced Growth Solution of the Singular Dynamic Input-Output System*

    Institute of Scientific and Technical Information of China (English)

    ChonghuiGuo; HuanwenTang

    2004-01-01

    The dynamic input-output system is well known in economic theory and practice. In this paper the asymptotic stability and balanced growth solution of the dynamic input-output system are considered. Under three natural assumptions, we obtain four theorems about asymptotic stability and balanced growth solution of the dynamic input-output system and bring together in a unified manner some contributions scattered in the literature.

  13. Dynamic interaction of fingertip skin and pin of tactile device

    Science.gov (United States)

    Grigas, Vytautas; Tolocka, Rymantas T.; Ziliukas, Pranas

    2007-12-01

    The present paper deals with investigations performed with the aim to study transmitting tactile information into the area of mechanoreceptors of the fingertip skin segment and to estimate the dynamic properties and behavior of the skin by performing numerical analysis. A computational finite element model consisting of four main layers of skin was used for transient analysis of contact dynamic interaction when loading the skin by a moving pin, as well as for modal analysis of skin and analysis of skin stress-strain state under harmonic loading (a plane strain case was studied). Material properties of the skin were assumed as linear elastic because of a very small excitation signal level. The efficiency of the regime of the skin dynamic loading in terms of the tactile signal level was defined on the basis of the strain level in the dermis zone where mechanoreceptors are placed. The possibilities of using vibratory control signal were analyzed.

  14. The Role of Fast Carrier Dynamics in SOA Based Devices

    DEFF Research Database (Denmark)

    Mørk, Jesper; Berg, Tommy Winther; Nielsen, Mads Lønstrup;

    2004-01-01

    We describe the characteristics of all-optical switching schemes based on semiconductor optical amplifiers (SOAs), with particular emphasis on the role of the fast carrier dynamics. The SOA response to a single short pulse as well as to a data-modulated pulse train is investigated and the propert......We describe the characteristics of all-optical switching schemes based on semiconductor optical amplifiers (SOAs), with particular emphasis on the role of the fast carrier dynamics. The SOA response to a single short pulse as well as to a data-modulated pulse train is investigated...

  15. Distributed Dynamic State Estimator, Generator Parameter Estimation and Stability Monitoring Demonstration

    Energy Technology Data Exchange (ETDEWEB)

    Meliopoulos, Sakis [Georgia Inst. of Technology, Atlanta, GA (United States); Cokkinides, George [Georgia Inst. of Technology, Atlanta, GA (United States); Fardanesh, Bruce [New York Power Authority, NY (United States); Hedrington, Clinton [U.S. Virgin Islands Water and Power Authority (WAPA), St. Croix (U.S. Virgin Islands)

    2013-12-31

    This is the final report for this project that was performed in the period: October1, 2009 to June 30, 2013. In this project, a fully distributed high-fidelity dynamic state estimator (DSE) that continuously tracks the real time dynamic model of a wide area system with update rates better than 60 times per second is achieved. The proposed technology is based on GPS-synchronized measurements but also utilizes data from all available Intelligent Electronic Devices in the system (numerical relays, digital fault recorders, digital meters, etc.). The distributed state estimator provides the real time model of the system not only the voltage phasors. The proposed system provides the infrastructure for a variety of applications and two very important applications (a) a high fidelity generating unit parameters estimation and (b) an energy function based transient stability monitoring of a wide area electric power system with predictive capability. Also the dynamic distributed state estimation results are stored (the storage scheme includes data and coincidental model) enabling an automatic reconstruction and “play back” of a system wide disturbance. This approach enables complete play back capability with fidelity equal to that of real time with the advantage of “playing back” at a user selected speed. The proposed technologies were developed and tested in the lab during the first 18 months of the project and then demonstrated on two actual systems, the USVI Water and Power Administration system and the New York Power Authority’s Blenheim-Gilboa pumped hydro plant in the last 18 months of the project. The four main thrusts of this project, mentioned above, are extremely important to the industry. The DSE with the achieved update rates (more than 60 times per second) provides a superior solution to the “grid visibility” question. The generator parameter identification method fills an important and practical need of the industry. The “energy function” based

  16. Dynamic test devices for analyzing the tensile properties of concrete

    NARCIS (Netherlands)

    Forquin, P.; Riedel, W.; Weerheijm, J.

    2013-01-01

    Owing to their low tensile failure strain, concrete is a difficult material to test under dynamic tensile loading. Indeed, conventional testing apparatuses such as high-speed hydraulic presses or Split Hopkinson Bar facilities rely on a mechanical balance of the specimen implying a short round-trip

  17. Dynamics of capillary self-alignment for mesoscopic foil devices

    NARCIS (Netherlands)

    Arutinov, G.; Mastrangeli, M.; Smits, E.C.P.; Schoo, H.F.M.; Brugger, J.; Dietzel, A.H.

    2013-01-01

    We report experimental evidence for three sequential, distinct dynamic regimes in the capillary self-alignment of centimeter-sized foil dies released at large uniaxial offsets from equilibrium. We show that the initial transient wetting regime, along with inertia and wetting properties of the dies,

  18. Measurement device for ankle joint kinematic and dynamic characterisation.

    Science.gov (United States)

    Giacomozzi, C; Cesinaro, S; Basile, F; De Angelis, G; Giansanti, D; Maccioni, G; Masci, E; Panella, A; Paolizzi, M; Torre, M; Valentini, P; Macellari, V

    2003-07-01

    The paper describes a measurement device for obtaining the kinematic characterisation and isometric loading of ankle joints under different working conditions. Non-invasive, in vivo experiments can be conducted with this experimental apparatus, the potential of which could be usefully exploited in basic biomedical research, prosthesis design, clinical applications, sports medicine and rehabilitation. The device determines the 3D movement of the foot with respect to the shank and evaluates the torques and moments around the three articular axes in relation to any desired angular position of the ankle complex. When integrated with superficial electromyographic techniques and electrical stimulation, it allows the assessment of the functionality of the lower leg in both mechanical and myo-electrical terms. The paper reports the main mechanical and electronic features of the device (high linearity; maximum moment ranges +/- 300 Nm for flexion-extension, +/- 35 Nm for both pronation-supination and internal-external rotation; angular ranges: +/- 100 degrees of dorsi-plantar flexion, +/- 50 degrees of internal-external rotation and prono-supination; linear ranges: +/- 25 mm along each axis). Results from a healthy volunteer, under voluntary or stimulated conditions, helped in testing its operatability, reliability, robustness, repeatability and effectiveness. Preliminary simplified protocols have been also applied to 20 healthy volunteers, and the main results were 80.8 +/- 11.9 degrees of internalexternal rotation, 46.2 +/- 9.1 degrees of prono-supination and 74.6 +/- 13.1 degrees of flexion-extension. Torques and moments were normalised with respect to a body mass index of 30. The maximum plantar flexion moment (57.5 + 21.3 Nm) was measured with the foot at 150 of dorsal flexion; the maximum dorsal flexion moment (50.2 + 20.3 Nm) was measured with the foot at 150 of plantar flexion.

  19. Simulation of Dynamic Yaw Stability Derivatives of a Bird Using CFD

    CERN Document Server

    Moelyadi, M A

    2008-01-01

    Simulation results on dynamic yaw stability derivatives of a gull bird by means of computational fluid dynamics are presented. Two different kinds of motions are used for determining the dynamic yaw stability derivatives CNr and CNbeta . Concerning the first one, simple lateral translation and yaw rotary motions in yaw are considered. The second one consists of combined motions. To determine dynamic yaw stability derivatives of the bird, the simulation of an unsteady flow with a bird model showing a harmonic motion is performed. The unsteady flow solution for each time step is obtained by solving unsteady Euler equations based on a finite volume approach for a smaller reduced frequency. Then, an evaluation of unsteady forces and moments for one cycle is conducted using harmonic Fourier analysis. The results on the dynamic yaw stability derivatives for both simulations of the model motion show a good agreement.

  20. Elastic Dynamic Stability of Big-Span Power Transmission Tower Subjected to Seismic Excitations

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hang; LI Li; FANG Qin-han; YE Kun

    2009-01-01

    By combining the time-history response analysis and the eigenvalue buckling analysis,this paper developed a computational procedure to study the elastic dynamic stability of a transmission tower by APDL language in ANSYS.The influences of different input directions of seismic excitations and damping ratio on the elastic dynamic stability of tower were discussed.The following conclusions were obtained:(1) Longitudinal direction of the transmission lines is the worst input direction of seismic excitation for the transmission tower.(2) Dead load has no significant effect on the critical load and the occurrence time of buckling.(3) Vertical input of seismic excitations has no great effect on the dynamic stability of the transmission tower.(4) Damping effect has an influence on the dynamic stability of the transmission tower; however,the inherent characteristics of dynamic buckling is not changed.

  1. CFD Based Determination of Dynamic Stability Derivatives in Yaw for a Bird

    Institute of Scientific and Technical Information of China (English)

    M. A. Moelyadi; G. Sachs

    2007-01-01

    Dynamic yaw stability derivatives of a gull bird are determined using Computational Fluid Dynamics(CFD) method. Two kinds of motions are applied for calculating the dynamic yaw stability derivatives CNr and CNβ. The first one relates to a lateral translation and, separately, to a yaw rotation. The second one consists of a combined translational and rotational motion. To determine dynamic yaw stability derivatives, the simulation of an unsteady flow with a bird model showing a harmonic motion is performed. The flow solution for each time step is obtained by solving unsteady Euler equations based on a finite volume approach for a small reduced frequency. Then, an evaluation of unsteady forces and moments for one cycle is conducted using harmonic Fourier analysis. The results of the dynamic yaw stability derivatives for both simulations of the model show a good agreement.

  2. Enabling Dynamic Security Management of Networked Systems via Device-Embedded Security (Self-Securing Devices)

    Science.gov (United States)

    2007-01-15

    and a 3Com 3C905B 100 MB network adapter. The servers have two 700 MHz Pentium Ills, 512 MB RAM, a 9 GB 10,000 RPM Quantum Atlas 1 OK II drive, an...Pentium III machine with 384 MB of memory. Storage-nodes use a 9 GB Quantum Atlas 10K as the storage device. The machines are connected through a 100 Mb...David L. Donoho, Ana Georgina Flesia, Umesh Shankar , Vern Paxson, Jason Coit, and Stu- art Staniford. Multiscale stepping-stone detection: detecting

  3. Dynamics of fluidic devices with applications to rotor pitch links

    Science.gov (United States)

    Scarborough, Lloyd H., III

    Coupling a Fluidic Flexible Matrix Composite (F2MC) to an air-pressurized fluid port produces a fundamentally new class of tunable vibration isolator. This fluidlastic device provides significant vibration reduction at an isolation frequency that can be tuned over a broad frequency range. The material properties and geometry of the F2MC element, as well as the port inertance, determine the isolation frequency. A unique feature of this device is that the port inertance depends on pressure so the isolation frequency can be adjusted by changing the air pressure. For constant port inertance, the isolation frequency is largely independent of the isolated mass so the device is robust to changes in load. A nonlinear model is developed to predict isolator length and port inertance. The model is linearized and the frequency response calculated. Experiments agree with theory, demonstrating a tunable isolation range from 9 Hz to 36 Hz and transmitted force reductions of up to 60 dB at the isolation frequency. Replacing rigid pitch links on rotorcraft with coupled fluidic devices has the potential to reduce the aerodynamic blade loads transmitted through the pitch links to the swashplate. Analytical models of two fluidic devices coupled with three different fluidic circuits are derived. These passive fluidlastic systems are tuned, by varying the fluid inertances and capacitances of each fluidic circuit, to reduce the transmitted pitch-link loads. The different circuit designs result in transmitted pitch link loads reduction at up to three main rotor harmonics. The simulation results show loads reduction at the targeted out-of-phase and in-phase harmonics of up to 88% and 93%, respectively. Experimental validation of two of the fluidic circuits demonstrates loads reduction of up to 89% at the out-of-phase isolation frequencies and up to 81% at the in-phase isolation frequencies. Replacing rigid pitch links on rotorcraft with fluidic pitch links changes the blade torsional

  4. The effects of different atmospheric conditions on device stability of organic small-molecule solar cells under constant illumination

    Science.gov (United States)

    Karak, S.; Pradhan, S.; Dhar, A.

    2011-09-01

    A systematic study is presented on various effects of different environmental conditions on stability and degradation of small-molecule organic solar cells under continuous simulated solar radiation. Devices were fabricated based on heterojunctions with pentacene and copper phthalocyanine as donor, and [6,6]-phenyl C61 butyric acid methyl ester as acceptor materials. Seven different operating conditions were employed to investigate their degradation stability. Three simultaneous mechanisms were found to be largely responsible for device degradation: (i) photo-oxidation of active materials in the presence of light and oxygen that results in a drop of photocarrier generation and electrical transport properties of the cells, (ii) morphology instability with UV annealing reducing the charge transport within the devices and (iii) bubble formation in the vicinity of the electrodes with moisture absorption, affecting charge collection efficiency of the cells. Significant improvement in device stability was found by careful choice of operating conditions and proper encapsulation. Device lifetime enhanced by almost 100 times under UV filtered vacuum environment or with polydimethylsiloxane encapsulation as compared to a cell operated under ambient conditions without encapsulation.

  5. Optimal placement of unified power flow controllers to improve dynamic voltage stability using power system variable based voltage stability indices.

    Science.gov (United States)

    Albatsh, Fadi M; Ahmad, Shameem; Mekhilef, Saad; Mokhlis, Hazlie; Hassan, M A

    2015-01-01

    This study examines a new approach to selecting the locations of unified power flow controllers (UPFCs) in power system networks based on a dynamic analysis of voltage stability. Power system voltage stability indices (VSIs) including the line stability index (LQP), the voltage collapse proximity indicator (VCPI), and the line stability index (Lmn) are employed to identify the most suitable locations in the system for UPFCs. In this study, the locations of the UPFCs are identified by dynamically varying the loads across all of the load buses to represent actual power system conditions. Simulations were conducted in a power system computer-aided design (PSCAD) software using the IEEE 14-bus and 39- bus benchmark power system models. The simulation results demonstrate the effectiveness of the proposed method. When the UPFCs are placed in the locations obtained with the new approach, the voltage stability improves. A comparison of the steady-state VSIs resulting from the UPFCs placed in the locations obtained with the new approach and with particle swarm optimization (PSO) and differential evolution (DE), which are static methods, is presented. In all cases, the UPFC locations given by the proposed approach result in better voltage stability than those obtained with the other approaches.

  6. Optimal placement of unified power flow controllers to improve dynamic voltage stability using power system variable based voltage stability indices.

    Directory of Open Access Journals (Sweden)

    Fadi M Albatsh

    Full Text Available This study examines a new approach to selecting the locations of unified power flow controllers (UPFCs in power system networks based on a dynamic analysis of voltage stability. Power system voltage stability indices (VSIs including the line stability index (LQP, the voltage collapse proximity indicator (VCPI, and the line stability index (Lmn are employed to identify the most suitable locations in the system for UPFCs. In this study, the locations of the UPFCs are identified by dynamically varying the loads across all of the load buses to represent actual power system conditions. Simulations were conducted in a power system computer-aided design (PSCAD software using the IEEE 14-bus and 39- bus benchmark power system models. The simulation results demonstrate the effectiveness of the proposed method. When the UPFCs are placed in the locations obtained with the new approach, the voltage stability improves. A comparison of the steady-state VSIs resulting from the UPFCs placed in the locations obtained with the new approach and with particle swarm optimization (PSO and differential evolution (DE, which are static methods, is presented. In all cases, the UPFC locations given by the proposed approach result in better voltage stability than those obtained with the other approaches.

  7. Optimal Placement of Unified Power Flow Controllers to Improve Dynamic Voltage Stability Using Power System Variable Based Voltage Stability Indices

    Science.gov (United States)

    Albatsh, Fadi M.; Ahmad, Shameem; Mekhilef, Saad; Mokhlis, Hazlie; Hassan, M. A.

    2015-01-01

    This study examines a new approach to selecting the locations of unified power flow controllers (UPFCs) in power system networks based on a dynamic analysis of voltage stability. Power system voltage stability indices (VSIs) including the line stability index (LQP), the voltage collapse proximity indicator (VCPI), and the line stability index (Lmn) are employed to identify the most suitable locations in the system for UPFCs. In this study, the locations of the UPFCs are identified by dynamically varying the loads across all of the load buses to represent actual power system conditions. Simulations were conducted in a power system computer-aided design (PSCAD) software using the IEEE 14-bus and 39- bus benchmark power system models. The simulation results demonstrate the effectiveness of the proposed method. When the UPFCs are placed in the locations obtained with the new approach, the voltage stability improves. A comparison of the steady-state VSIs resulting from the UPFCs placed in the locations obtained with the new approach and with particle swarm optimization (PSO) and differential evolution (DE), which are static methods, is presented. In all cases, the UPFC locations given by the proposed approach result in better voltage stability than those obtained with the other approaches. PMID:25874560

  8. TOPICAL REVIEW: Current-driven dynamics in molecular-scale devices

    Science.gov (United States)

    Seideman, Tamar

    2003-04-01

    We review recent theoretical work on current-triggered processes in molecular-scale devices - a field at the interface between solid state physics and chemical dynamics with potential applications in diverse areas, including artificial molecular machines, unimolecular transport, surface nanochemistry and nanolithography. The qualitative physics underlying current-triggered dynamics is first discussed and placed in context with several well-studied phenomena with which it shares aspects. A theory for modelling these dynamics is next formulated within a time-dependent scattering approach. Our end result provides useful insight into the system properties that determine the reaction outcome as well as a computationally convenient framework for numerical realization. The theory is applied to study single-molecule surface reactions induced by a scanning tunnelling microscope and current-triggered dynamics in single-molecule transistors. We close with a discussion of several potential applications of current-induced dynamics in molecular devices and several opportunities for future research.

  9. Origins of periodic and chaotic dynamics in microfluidic loop devices

    CERN Document Server

    Maddala, Jeevan; Rengaswamy, Raghunathan

    2012-01-01

    Droplets moving in a microfluidic loop device exhibit both periodic and chaotic behaviors based on the inlet droplet spacing. We propose that the periodic behavior is an outcome of a dispersed phase conservation principle. This conservation principle translates into a droplet spacing conservation equation. Additionally, we define a simple technique to identify periodicity in experimental systems with input scatter. Aperiodic behavior is observed in the transition regions between different periodic behaviors. We propose that the cause for aperiodicity is the synchronization of timing between the droplets entering and leaving the system. We derive an analytical expression to estimate the occurrence of these transition regions as a function of system parameters. We provide experimental, simulation and analytical results to validate the proposed theory.

  10. Animal flight dynamics I. Stability in gliding flight.

    Science.gov (United States)

    Thomas, A L; Taylor, G K

    2001-10-07

    Stability is as essential to flying as lift itself, but previous discussions of how flying animals maintain stability have been limited in both number and scope. By developing the pitching moment equations for gliding animals and by discussing potential sources of roll and yaw stability, we consider the various sources of static stability used by gliding animals. We find that gliding animals differ markedly from aircraft in how they maintain stability. In particular, the pendulum stability provided when the centre of gravity lies below the wings is a much more important source of stability in flying animals than in most conventional aircraft. Drag-based stability also appears to be important for many gliding animals, whereas in aircraft, drag is usually kept to a minimum. One unexpected consequence of these differences is that the golden measure of static pitching stability in aircraft--the static margin--can only strictly be applied to flying animals if the equilibrium angle of attack is specified. We also derive several rules of thumb by which stable fliers can be identified. Stable fliers are expected to exhibit one or more of the following features: (1) Wings that are swept forward in slow flight. (2) Wings that are twisted down at the tips when swept back (wash-out) and twisted up at the tips when swept forwards (wash-in). (3) Additional lifting surfaces (canard, hindwings or a tail) inclined nose-up to the main wing if they lie forward of it, and nose-down if they lie behind it (longitudinal dihedral). Each of these predictions is directional--the opposite is expected to apply in unstable animals. In addition, animals with reduced stability are expected to display direct flight patterns in turbulent conditions, in contrast to the erratic flight patterns predicted for stable animals, in which large restoring forces are generated. Using these predictions, we find that flying animals possess a far higher degree of inherent stability than has generally been

  11. Overview of Orion Crew Module and Launch Abort Vehicle Dynamic Stability

    Science.gov (United States)

    Owens, Donald B.; Aibicjpm. Vamessa V.

    2011-01-01

    With the retirement of the Space Shuttle, NASA is designing a new spacecraft, called Orion, to fly astronauts to low earth orbit and beyond. Characterization of the dynamic stability of the Orion spacecraft is important for the design of the spacecraft and trajectory construction. Dynamic stability affects the stability and control of the Orion Crew Module during re-entry, especially below Mach = 2.0 and including flight under the drogues. The Launch Abort Vehicle is affected by dynamic stability as well, especially during the re-orientation and heatshield forward segments of the flight. The dynamic stability was assessed using the forced oscillation technique, free-to-oscillate, ballistic range, and sub-scale free-flight tests. All of the test techniques demonstrated that in heatshield-forward flight the Crew Module and Launch Abort Vehicle are dynamically unstable in a significant portion of their flight trajectory. This paper will provide a brief overview of the Orion dynamic aero program and a high-level summary of the dynamic stability characteristics of the Orion spacecraft.

  12. Static and dynamic stability analysis of the space shuttle vehicle-orbiter

    Science.gov (United States)

    Chyu, W. J.; Cavin, R. K.; Erickson, L. L.

    1978-01-01

    The longitudinal static and dynamic stability of a Space Shuttle Vehicle-Orbiter (SSV Orbiter) model is analyzed using the FLEXSTAB computer program. Nonlinear effects are accounted for by application of a correction technique in the FLEXSTAB system; the technique incorporates experimental force and pressure data into the linear aerodynamic theory. A flexible Orbiter model is treated in the static stability analysis for the flight conditions of Mach number 0.9 for rectilinear flight (1 g) and for a pull-up maneuver (2.5 g) at an altitude of 15.24 km. Static stability parameters and structural deformations of the Orbiter are calculated at trim conditions for the dynamic stability analysis, and the characteristics of damping in pitch are investigated for a Mach number range of 0.3 to 1.2. The calculated results for both the static and dynamic stabilities are compared with the available experimental data.

  13. Temporal stability in forest productivity increases with tree diversity due to asynchrony in species dynamics.

    Science.gov (United States)

    Morin, Xavier; Fahse, Lorenz; de Mazancourt, Claire; Scherer-Lorenzen, Michael; Bugmann, Harald

    2014-12-01

    Theory predicts a positive relationship between biodiversity and stability in ecosystem properties, while diversity is expected to have a negative impact on stability at the species level. We used virtual experiments based on a dynamic simulation model to test for the diversity-stability relationship and its underlying mechanisms in Central European forests. First our results show that variability in productivity between stands differing in species composition decreases as species richness and functional diversity increase. Second we show temporal stability increases with increasing diversity due to compensatory dynamics across species, supporting the biodiversity insurance hypothesis. We demonstrate that this pattern is mainly driven by the asynchrony of species responses to small disturbances rather than to environmental fluctuations, and is only weakly affected by the net biodiversity effect on productivity. Furthermore, our results suggest that compensatory dynamics between species may enhance ecosystem stability through an optimisation of canopy occupancy by coexisting species. © 2014 John Wiley & Sons Ltd/CNRS.

  14. An Improved Force-Angle Stability Margin for Radial Symmetrical Hexapod Robot Subject to Dynamic Effects

    Directory of Open Access Journals (Sweden)

    Shidong Long

    2015-05-01

    Full Text Available This paper presents a study on stability monitoring for a radial symmetrical hexapod robot under dynamic conditions. The force-angle stability margin (FASM measure method has been chosen as the stability criterion. This is because it is suitable for the stability analysis, in terms of external forces or manipulator loads acting on the body. Considering that a radial symmetrical hexapod robot can tumble along the contact point besides tip-over axis, this paper proposes an improved FASM measure method. Furthermore, it provides the method for calculating the stability angle of contact point and simplifies the algorithm of FASM. To verify the improved FASM measure method, three potential dynamic situations have been simulated. The simulation results confirm that, under dynamic conditions, the improved FASM is efficient, simple in terms of calculation cost and sensitive to manipulator loads and external disturbances. This means it has practical value in on-line controllers.

  15. Evaluation on Stability of Stope Structure Based on Nonlinear Dynamics of Coupling Artificial Neural Network

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The nonlinear dynamical behaviors of artificial neural network (ANN) and their application to science and engineering were summarized. The mechanism of two kinds of dynamical processes, i.e. weight dynamics and activation dynamics in neural networks, and the stability of computing in structural analysis and design were stated briefly. It was successfully applied to nonlinear neural network to evaluate the stability of underground stope structure in a gold mine. With the application of BP network, it is proven that the neuro-computing is a practical and advanced tool for solving large-scale underground rock engineering problems.

  16. Theory and analysis of nonlinear dynamics and stability in storage rings: A working group summary

    Energy Technology Data Exchange (ETDEWEB)

    Chattopadhyay, S.; Audy, P.; Courant, E.D.; Forest, E.; Guignard, G.; Hagel, J.; Heifets, S.; Keil, E.; Kheifets, S.; Mais, H.; Moshammer, H.; Pellegrini, C.; Pilat, F.; Suzuki, T.; Turchetti, G.; Warnock, R.L.

    1988-07-01

    A summary and commentary of the available theoretical and analytical tools and recent advances in the nonlinear dynamics, stability and aperture issues in storage rings are presented. 11 refs., 4 figs.

  17. 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.

  18. Relationship between Core Stability Muscle Endurance and Static and Dynamic Balance in Basketball Players

    Directory of Open Access Journals (Sweden)

    farzaneh saki

    2016-03-01

    Full Text Available Objective: Balancing is the most basic function of the neuromuscular system in performing all simple and complex activities that contribute to health-related physical fitness. Core stability may be a contributing factor to static and dynamic balance. The aim of this study was to investigate the relationship between core stability muscle endurance and static and dynamic balance in basketball players. Methods: 100 basketball players (50 female and 50 male players were selected randomly based on the including criteria.To evaluate core stability muscle strength, a set of tests from core stability exercises was used. Static and dynamic balance were evaluated by Bass Stick and Y balance test respectively. Normality of the data was evaluated using the Kolmogorov Smirnoff test. Data analysis was performed by Spearman product moment coefficient test and independent samples t test. Significant level of p&le0/05 was used in all statistical analyses. Results: Results of t-test showed no significant difference between static balance in boys and girls, while significant differences were observed between dynamic balance and core stability in males and females. In other words, core stability and dynamic balance in boys were more than girls. Also, the results of correlation analysis showed a significant relationship between core stability and dynamic balance (p=0.00 However, no significant relationship was observed between core stability and static balance (p=0.451. Conclusion: Due to the correlation between muscle endurance and dynamic balance in the present study, it can be implied that core stability exercises can improve balance.

  19. Comparative study of the Ender method and Dynamic Hip Screw stabilization in the treatment of intertrochanteric fractures of the femur.

    Science.gov (United States)

    Walo, Roman; Semenowicz, Jacek; Grabowski, Marcin; Komarek, Marcin; Czuma, Przemysław

    2003-02-28

    Background. The aim of this retrospective study was to compare the results of two fixation devices (Ender rods in 118 patients and dynamic hip screw in 98 patients) for treatment of intertrochateric fractures of the hip. Material and methods. The two treatment groups were similar with respect to important preoperative variables such as age, coexisting disseases, bone quality and incidence of stable and unstable fractures. The following outcomes were assessed: quality of reduction, length of hospital stay, early mortality, reoperations, persistent pain at a knee or hip, decrease in range of motion of the knee and leg shortening. Results and conclusions. The subgroup analysis showed higher incidence of complications in patients with unstable type of fracture treated with Ender nailing. These complications included mainly valgus angulation and malrotation of the fracture, need for a secondary procedure due to loss of stabilization and knee pain. Intramedullary stabilization with Ender rods is not recommended in treatment of unstable intertrochanteric fractures of the femur.

  20. Stability Analysis for Hand-arm-forearm Dynamic System

    Directory of Open Access Journals (Sweden)

    Florin Bausic

    2014-07-01

    Full Text Available In this paper we propose a model with four degrees of freedom for hand-arm-forearm dynamic system. Using experimental data from [9] by means of the Simulink program, is built block diagram to simulate the dynamic system motion and phase diagrams are drawn by using Matlab. From the interpretation of these diagrams result, for a set of parameters ( m, c, k, FO, ω , stable moves for the hand-arm-forearm dynamic system.

  1. Combined Characterization Techniques to Understand the Stability of a Variety of Organic Photovoltaic Devices - the ISOS-3 inter- laboratory collaboration

    DEFF Research Database (Denmark)

    Lira-Cantu, Monica; Tanenbaum, David M.; Norrman, Kion

    2012-01-01

    This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPVs) devices prepared by leading research laboratories. All devices have been shipped to and degraded at the Danish Technical University (DTU, formerly ...... and not to the active materials of the solar cell.......This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPVs) devices prepared by leading research laboratories. All devices have been shipped to and degraded at the Danish Technical University (DTU, formerly...... RISO-DTU) up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. In this work we present a summary of the degradation response observed for the NREL sample, an inverted OPV of the type ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag/Al, under full sun stability test...

  2. Coordination of Series and Shunt Flexible Alternating Current Transmission Line System Devices Based Thyristor Controller for Improving Power System Stability

    Directory of Open Access Journals (Sweden)

    Prechanon Kumkratug

    2011-01-01

    Full Text Available Problem statement: Thyristor Controlled Series Capacitor (TCSC and Static Var Compensator (SVC have been individually applied to improve stability of power system. Approach: This study presents the coordination of a TCSC and SVC for improving power system stability. The swing curves of the three phase faulted power system with various cases are tested and compared. Results: The swing curve of system without FACTS devices has undamped oscillation. The system with a TCSC or a SVC can increase damping of power system whereas the system with coordination of a TCSC and a SVC provides the best results of stability improvement Conclusion: From the simulation results, the stability of power system can be much better improved by coordination control of a TCSC and a SVC.

  3. Test of Cable Products in Respect of Thermal and Dynamic Stability

    Directory of Open Access Journals (Sweden)

    M. A. Коrotkevich

    2010-01-01

    Full Text Available The paper considers conditions for selection of  power supply of the unit which is used for testing samples of cable products by thermal and dynamic stability currents. It has been shown that while conducting testing by thermal and dynamic stability currents at nominal cable voltage it is more justifiable to use a percussive energy accumulator, and in the case when the voltage is low an inductive energy accumulator is used.

  4. Relationship between Core Stability Muscle Endurance and Static and Dynamic Balance in Basketball Players

    OpenAIRE

    farzaneh saki; masumeh Baghban

    2016-01-01

    Objective: Balancing is the most basic function of the neuromuscular system in performing all simple and complex activities that contribute to health-related physical fitness. Core stability may be a contributing factor to static and dynamic balance. The aim of this study was to investigate the relationship between core stability muscle endurance and static and dynamic balance in basketball players. Methods: 100 basketball players (50 female and 50 male players) were selected randomly bas...

  5. Dynamic stability margin using a marker based system and Tekscan: a comparison of four gait conditions.

    Science.gov (United States)

    Lugade, Vipul; Kaufman, Kenton

    2014-01-01

    Stability during gait is maintained through control of the center of mass (CoM) position and velocity in relation to the base of support (BoS). The dynamic stability margin, or the interaction of the extrapolated center of mass with the closest boundary of the BoS, can reveal possible control errors during gait. The purpose of this study was to investigate a marker based method for defining the BoS, and compare the dynamic stability margin throughout gait in comparison to a BoS defined from foot pressure sensors. The root mean squared difference between these two methodologies ranged from 0.9 cm to 3.5 cm, when walking under four conditions: plantigrade, equinus, everted, and inverted. As the stability margin approaches -35 cm prior to contralateral heel strike, there was approximately 90% agreement between the two systems at this time point. Underestimation of the marker based dynamic stability margin or overestimation of the pressure based dynamic stability margin was due to inaccuracies in defining the medial boundary of the BoS. Overall, care must be taken to ensure similar definitions of the BoS are utilized when comparing the dynamic stability margin between participants and gait conditions.

  6. Role of Intrinsic and Reflexive Dynamics in the Control of Spinal Stability

    OpenAIRE

    Moorhouse, Kevin Michael

    2005-01-01

    Role of Intrinsic and Reflexive Dynamics in the Control of Spinal Stability Kevin M. Moorhouse Abstract Spinal stability describes the ability of the neuromuscular system to maintain equilibrium in the presence of kinematic and control variability, and may play an important role in the etiology of low-back disorders (LBDs). The primary mechanism for the neuromuscular control of spinal stability is the recruitment and control of active paraspinal muscle stiffness (i.e., trunk stif...

  7. A new transient stability margin based on dynamic security region and its applications

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A new transient stability margin is proposed based on a new expression of dynamic security region (DSR) which is developed from the existing expression of DSR. Applications of the DSR based transient stability margin to contingency ranking and screening are discussed. Simulations in the 10-machine 39-bus New England system are performed to show the effectiveness of the proposed DSR based tran-sient stability margin.

  8. Differences in shielding versus trapping behaviour of dynamically stabilized NbTi cylinders

    CERN Document Server

    Häbel, E

    1977-01-01

    It was found experimentally that dynamically stabilized NbTi cylinders show, in contrast to general expectation, a stability behaviour for shielding of external magnetic fields different from that for trapping. This phenomenon is discussed and a theoretical interpretation is proposed. (10 refs).

  9. A Note on "Stability of the Constant Cost Dynamic Lot Size Model" by K. Richter

    NARCIS (Netherlands)

    S. van Hoesel (Stan); A.P.M. Wagelmans (Albert)

    1991-01-01

    textabstractIn a paper by K. Richter the stability regions of the dynamic lot size model with constant cost parameters are analyzed. In particular, an algorithm is suggested to compute the stability region of a so-called generalized solution. In general this region is only a subregion of the stabili

  10. Novel Rigid External Distraction Device Improves Stability and Controls the Vector During Midfacial Advancement.

    Science.gov (United States)

    Resnick, Cory M; Rottgers, Stephen Alex; Langenfeld, Christopher C; Mulliken, John B; Padwa, Bonnie L

    2016-06-01

    The major limitation of the rigid external devices currently used for midfacial distraction after subcranial Le Fort III osteotomies is the ductile wire that connects the midface to the device, which makes it difficult to control the vector and force during distraction. The authors describe a novel external appliance that addresses this and other problems of contemporary devices, and application of a custom cranial template that facilitates precise placement of the device to achieve the planned vector of distraction.

  11. Motivational Dynamics in Language Learning: Change, Stability, and Context

    Science.gov (United States)

    Waninge, Freerkien; Dörnyei, Zoltán; De Bot, Kees

    2014-01-01

    Motivation as a variable in L2 development is no longer seen as the stable individual difference factor it was once believed to be: Influenced by process-oriented models and principles, and especially by the growing understanding of how complex dynamic systems work, researchers have been focusing increasingly on the dynamic and changeable nature…

  12. Dynamical output feedback stabilization for neutral systems with mixed delays

    Institute of Scientific and Technical Information of China (English)

    Wei QIAN; Guo-jiang SHEN; You-xian SUN

    2008-01-01

    This paper is concerned with the issue of stabilization for the linear neutral systems with mixed delays.The attention is focused on the design of output feedback controllers which guarantee the asymptotical stability of the closed-loop systems.Based on the model transformation of neutral type,the Lyapunov-Krasovskii functional method is employed to establish the delay-dependent stability criterion.Then,through the controller parameterization and some matrix transformation techniques,the desired parameters are determined under the delay-dependent design condition in terms of linear matrix inequalities (LMIs),and the desired controller is explicitly formulated.A numerical example is given to illustrate the effectiveness of the proposed method.

  13. Stability and dynamical properties of Cooper-Shepard-Sodano compactons.

    Science.gov (United States)

    Mihaila, Bogdan; Cardenas, Andres; Cooper, Fred; Saxena, Avadh

    2010-12-01

    Extending a Padé approximant method used for studying compactons in the Rosenau-Hyman (RH) equation, we study the numerical stability of single compactons of the Cooper-Shepard-Sodano (CSS) equation and their pairwise interactions. The CSS equation has a conserved Hamiltonian which has allowed various approaches for studying analytically the nonlinear stability of the solutions. We study three different compacton solutions and find they are numerically stable. Similar to the collisions between RH compactons, the CSS compactons re-emerge with same coherent shape when scattered. The time evolution of the small-amplitude ripple resulting after scattering depends on the values of the parameters l and p characterizing the corresponding CSS equation. The simulation of the CSS compacton scattering requires a much smaller artificial viscosity to obtain numerical stability than in the case of RH compacton propagation.

  14. Studies of the Stability and Dynamics of Levitated Drops

    Science.gov (United States)

    Anikumar, A.; Lee, Chun Ping; Wang, T. G.

    1996-01-01

    This is a review of our experimental and theoretical studies relating to equilibrium and stability of liquid drops, typically of low viscosity, levitated in air by a sound field. The major emphasis here is on the physical principles and understanding behind the stability of levitated drops. A comparison with experimental data is also given, along with some fascinating pictures from high-speed photography. One of the aspects we shall deal with is how a drop can suddenly burst in an intense sound field; a phenomenon which can find applications in atomization technology. Also, we are currently investigating the phenomenon of suppression of coalescence between drops levitated in intense acoustic fields.

  15. Metal hydride switchable mirrors: Factors influencing dynamic range and stability

    Energy Technology Data Exchange (ETDEWEB)

    Slack, Jonathan L.; Locke, James C.W.; Song, Seung-Wan; Ona, Jason; Richardson, Thomas J. [Lawrence Berkeley National Laboratory, Building Technologies Department, Environmental Energy Technologies Division, Berkeley, CA 94720 (United States)

    2006-03-06

    Palladium-coated magnesium-manganese-nickel films behave as gasochromic switchable mirrors, becoming transparent on exposure to dilute hydrogen, and reverting to a mirror state on exposure to air. The cycling stability of the optical switching depends upon preservation of the integrity of the Pd catalyst overlayer. Alloying between Mg and Pd causes interdiffusion of the two elements, and leads to degradation in switching speed and eventual deactivation. Incorporation of a thin niobium oxide barrier layer between the active magnesium alloy film and the Pd layer substantially improves the cycling stability of the mirror. (author)

  16. 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.

  17. Modeling and Experimental Tests of a Mechatronic Device to Measure Road Profiles Considering Impact Dynamics

    DEFF Research Database (Denmark)

    Souza, A.; Santos, Ilmar

    2002-01-01

    Vehicles travel at different speeds and, as a consequence, experience a broad spectrum of vibrations. One of the most important source of vehicle vibration is the road profile. Hence the knowledge of the characteristics of a road profile enables engineers to predict the dynamic behavior...... to highlight that the aim of this device is to independently measure two road profiles, without the influence of the vehicle dynamics where the mechanism is attached. Before the mechatronic mechanism is attached to a real vehicle, its dynamic behavior must be known. A theoretical analysis of the mechanism...... the mechanism components. By modeling impacts between a wheel and the road by Newton´s Law, the complete dynamics of the system can be predicted, and the operational range (velocity limits) of the mechanism can be defined based on the mathematical model. Key words: multibody dynamics, impact dynamics and road...

  18. Justification for parameters of a dynamic stabilizer of the experimental stand mobile unit in studying of active rotational working tools of tiller machines

    Directory of Open Access Journals (Sweden)

    Vladimir F. Kupryashkin

    2017-03-01

    Full Text Available Introduction: The article deals with design options and technological modes of the dynamic stabilizer of the experimental stand mobile unit for studying tillage machine active rotating work tools. Based on theoretical and experimental studies, the possibility the movable module instability was discovered. This negatively affects on implementing the experiment program trough the especific method. The need in engineering solutions for the defect correction is shown. In addition, the authors consider the structural features and characteristics of the used devices for providing the stabilization of the movable module in the study of active rotating work tools of tillage machines. An electromagnetic brake dynamic stabilizer in the structure of the existing rolling module was proposed as an engineering device. Materials and Methods: A theoretical study of rolling module stability, based on synthesis of basic regulations and laws of mechanics related to active rotating work tools was conducted. As a result of the theoretical research, a design scheme of movable module loading was created. This scheme includes the design features and structural power factors. Results: A database representing the settings of power specification in the motion stability determining the mobile unit was created. Further use of the database values allow supporting the most optimal location of the electromagnetic brake with its design options. Discussion and Conclusions: The research of the electromagnetic brake in a mobile unit promoted stabilizing the unit movement, increased the frequency of its use and provided data that are more precise during experiments.

  19. Impulsive and hybrid dynamical systems stability, dissipativity, and control

    CERN Document Server

    Haddad, Wassim M; Nersesov, Sergey G

    2014-01-01

    This book develops a general analysis and synthesis framework for impulsive and hybrid dynamical systems. Such a framework is imperative for modern complex engineering systems that involve interacting continuous-time and discrete-time dynamics with multiple modes of operation that place stringent demands on controller design and require implementation of increasing complexity--whether advanced high-performance tactical fighter aircraft and space vehicles, variable-cycle gas turbine engines, or air and ground transportation systems. Impulsive and Hybrid Dynamical Systems goes beyond similar

  20. Qualitative and quantitative analysis of stability and instability dynamics of positive lattice solitons.

    Science.gov (United States)

    Sivan, Y; Fibich, G; Ilan, B; Weinstein, M I

    2008-10-01

    We present a unified approach for qualitative and quantitative analysis of stability and instability dynamics of positive bright solitons in multidimensional focusing nonlinear media with a potential (lattice), which can be periodic, periodic with defects, quasiperiodic, single waveguide, etc. We show that when the soliton is unstable, the type of instability dynamic that develops depends on which of two stability conditions is violated. Specifically, violation of the slope condition leads to a focusing instability, whereas violation of the spectral condition leads to a drift instability. We also present a quantitative approach that allows one to predict the stability and instability strength.

  1. Adaptive Finite-Time Stabilization of High-Order Nonlinear Systems with Dynamic and Parametric Uncertainties

    Directory of Open Access Journals (Sweden)

    Meng-Meng Jiang

    2016-01-01

    Full Text Available Under the weaker assumption on nonlinear functions, the adaptive finite-time stabilization of more general high-order nonlinear systems with dynamic and parametric uncertainties is solved in this paper. To solve this problem, finite-time input-to-state stability (FTISS is used to characterize the unmeasured dynamic uncertainty. By skillfully combining Lyapunov function, sign function, backstepping, and finite-time input-to-state stability approaches, an adaptive state feedback controller is designed to guarantee high-order nonlinear systems are globally finite-time stable.

  2. On the internal dynamics of starless cores: stability of starless cores with internal motions and collapse dynamics

    CERN Document Server

    Seo, Young Min; Shirley, Yancy L

    2013-01-01

    In order to understand the collapse dynamics of observed low-mass starless cores, we revise the conventional stability condition of hydrostatic Bonnor-Ebert spheres to take internal motions into account. Because observed starless cores resemble Bonnor-Ebert density structures, the stability and dynamics of the starless cores are frequently analyzed by comparing to the conventional stability condition of a hydrostatic Bonnor-Ebert sphere. However, starless cores are not hydrostatic but have observed internal motions. In this study, we take gaseous spheres with a homologous internal velocity field and derive stability conditions of the spheres utilizing a virial analysis. We propose two limiting models of spontaneous gravitational collapse: the collapse of critical Bonnor-Ebert spheres and uniform density spheres. The collapse of these two limiting models are intended to provide the lower and the upper limits, respectively, of the infall speeds for a given density structure. The results of our study suggest tha...

  3. A Robust Stability and Control Theory for Hybrid Dynamical Systems

    Science.gov (United States)

    2006-09-30

    IEEE Transactions on Automatic Control , to...Dual Linear Differential Inclusions", IEEE Transactions on Automatic Control , Vol. 51, Issue 4, April 2006, pp. 661-666. D. Liberzon and J. Hespanha...34Stabilization of nonlinear systems with limited information feedback", IEEE Transactions on Automatic Control , vol. 50, no. 6, pp. 910-915,

  4. Dynamic surface tension measured with an integrated sensor-actuator device using electrolytically generated gas bubbles

    NARCIS (Netherlands)

    Olthuis, Wouter; Volanschi, Alex; Bergveld, Piet

    1997-01-01

    In this paper, a new, simple method to determine dynamic surface tension in aqueous solutions is reported, explained and experimentally verified. By function integration, a small device is obtained; apart from control and interface electronics no external components or systems are necessary. Instead

  5. The Dynamics of an Isolated Plasma Filament at the Edge of a Toroidal Device, Rev. 1

    Energy Technology Data Exchange (ETDEWEB)

    Ryutov, D D

    2006-09-28

    The dynamics of an isolated plasma filament (an isolated blob) in the far scrape-off layer (SOL) of a toroidal device is described, with a proper averaging of the geometrical parameters as well as plasma parameters along the filament. The analysis is limited to the magnetohydrodynamic description. The effects of the anchored ends and finite plasma resistivity are also discussed.

  6. Robust adaptive dynamic programming and feedback stabilization of nonlinear systems.

    Science.gov (United States)

    Jiang, Yu; Jiang, Zhong-Ping

    2014-05-01

    This paper studies the robust optimal control design for a class of uncertain nonlinear systems from a perspective of robust adaptive dynamic programming (RADP). The objective is to fill up a gap in the past literature of adaptive dynamic programming (ADP) where dynamic uncertainties or unmodeled dynamics are not addressed. A key strategy is to integrate tools from modern nonlinear control theory, such as the robust redesign and the backstepping techniques as well as the nonlinear small-gain theorem, with the theory of ADP. The proposed RADP methodology can be viewed as an extension of ADP to uncertain nonlinear systems. Practical learning algorithms are developed in this paper, and have been applied to the controller design problems for a jet engine and a one-machine power system.

  7. A unifying energy-based approach to stability of power grids with market dynamics

    NARCIS (Netherlands)

    Stegink, Tjerk; De Persis, Claudio; van der Schaft, Arjan

    2016-01-01

    In this paper a unifying energy-based approach is provided to the modeling and stability analysis of power systems coupled with market dynamics. We consider a standard model of the power network with a third-order model for the synchronous generators involving voltage dynamics. By applying the prima

  8. Meteorological fluid dynamics asymptotic modelling, stability and chaotic atmospheric motion

    CERN Document Server

    Zeytounian, Radyadour K

    1991-01-01

    The author considers meteorology as a part of fluid dynamics. He tries to derive the properties of atmospheric flows from a rational analysis of the Navier-Stokes equations, at the same time analyzing various types of initial and boundary problems. This approach to simulate nature by models from fluid dynamics will be of interest to both scientists and students of physics and theoretical meteorology.

  9. Transient modelling of loss and thermal dynamics in power semiconductor devices

    DEFF Research Database (Denmark)

    Ma, Ke; Yang, Yongheng; Blaabjerg, Frede

    2014-01-01

    on the proposed models, the bandwidths of the loss or thermal response to major disturbances in the converter system can be analytically mapped, enabling more advanced tools to investigate the transient characteristics of loss and thermal dynamics in the power electronics devices.......The dynamical behavior of temperature is becoming a critical design consideration for the power electronics, because they are referred as “thermal cycling” which is the root cause of fatigues in the power electronics devices, and thus is closely related to the reliability of the converter....... It is well understood that the loading of power devices are disturbed by many factors of the converter system like grid, control, environment, etc., which emerge at various time-constants. However, the corresponding thermal response to these disturbances is still unclear, especially the transient behaviors...

  10. Dynamic stability during level walking and obstacle crossing in persons with facioscapulohumeral muscular dystrophy.

    Science.gov (United States)

    Rijken, N H M; van Engelen, B G M; Geurts, A C H; Weerdesteyn, V

    2015-09-01

    Patients with FSHD suffer from progressive skeletal muscle weakness, which is associated with an elevated fall risk. To obtain insight into fall mechanisms in this patient group, we aimed to assess dynamic stability during level walking and obstacle crossing in patients at different disease stages. Ten patients with at least some lower extremity weakness were included, of whom six were classified as moderately affected and four as mildly affected. Ten healthy controls were also included. Level walking at comfortable speed was assessed, as well as crossing a 10 cm high wooden obstacle. We assessed forward and lateral dynamic stability, as well as spatiotemporal and kinematics variables. During level walking, the moderately affected group demonstrated a lower walking speed, which was accompanied by longer step times and smaller step lengths, yet dynamic stability was unaffected. When crossing the obstacle, however, the moderately affected patients demonstrated reduced forward stability margins during the trailing step, which was accompanied by an increased toe clearance and greater trunk and hip flexion. This suggests that during level walking, the patients effectively utilized compensatory strategies for maintaining dynamic stability, but that the moderately affected group lacked the capacity to fully compensate for the greater stability demands imposed by obstacle crossing, rendering them unable to maintain optimal stability levels. The present results highlight the difficulties that FSHD patients experience in performing this common activity of daily living and may help explain their propensity to fall in the forward direction.

  11. A review of dynamic stability of repulsive-force maglev suspension systems

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Y.; Rote, D.M.

    1998-07-01

    Vehicle dynamics and the need to satisfy ride quality requirements have long been recognized as crucial to the commercial success of passenger-carrying transportation systems. Design concepts for maglev systems are no exception. Early maglev investigators and designers were well aware of the importance of ride quality and took care to ensure that their designs would meet acceptable ride quality standards. In contrast, the dynamic stability of electrodynamic suspension (EDS) systems, which has obvious implications for system safety and cost as well as for ride quality, has not received nearly as much attention. Because of the well-known under-damped nature of EDS suspension systems and the observation of instabilities in laboratory-scale model systems, it is prudent to develop a better understanding of vehicle stability characteristics. The work reported in this was undertaken with the intention of summarizing information that has been accumulated worldwide and that is relevant to dynamic stability of repulsive-force maglev suspension systems, assimilating that information, and gaining an understanding of the factors that influence that stability. Included in the paper is a discussion and comparison of results acquired from some representative tests of large-scale vehicles on linear test tracks, together with analytical and laboratory-scale investigations of stability and dynamics of EDS systems. This paper will also summarize the R and D activities at Argonne National Laboratory (ANL) since 1991 to study the nature of the forces that are operative in an EDS system and the dynamic stability of such systems.

  12. Research on Dynamics and Stability in the Stairs-Climbing of a Tracked Mobile Robot

    Directory of Open Access Journals (Sweden)

    Weijun Tao

    2012-10-01

    Full Text Available Aiming at the functional requirement of climbing up the stairs, the dynamics and stability during a tracked mobile robot's climbing of stairs is studied. First, from the analysis of its cross-country performance, the mechanical structure of the tracked mobile robot is designed and the hardware composition of its control system is given. Second, based on the analysis to its stairs-climbing process, the dynamical model of stairs-climbing is established by using the classical mechanics method. Next, the stability conditions for its stairs-climbing are determined and an evaluation method of its stairs-climbing stability is proposed, based on a mechanics analysis on the robot's backwards tumbling during the stairs-climbing process. Through simulation and experiments, the effectiveness of the dynamical model and the stability evaluation method of the tracked mobile robot in stairs-climbing is verified, which can provide design and analysis foundations for the tracked mobile robots' stairs-climbing.

  13. Numerical Simulation of the Dynamic FSI Response and Stability of a Flapping Foil in a Dense Fluid

    Science.gov (United States)

    Chae, Eun Jung; Akcabay, Deniz Tolga; Young, Yin Lu

    2012-11-01

    To advance the understanding of fish locomotion, improve the design biological devices or marine propulsions or turbines, or to explore innovative ocean energy harvesting ideas, it is important to be able accurately predict the dynamic fluid structure interaction (FSI) response and stability of flexible structures in a dense fluid. The objectives of this research are to (1) present an efficient and stable algorithm for numerical modeling of the dynamic FSI response and stability of a flapping foil in dense fluid, and (2) investigate the influence of fluid-to-solid density ratio on the FSI response and stability of a flapping foil. The numerical model involves coupling an unsteady RANS solver with a 2DOF structural model using a new hybrid coupling approach. The results show that the new hybrid coupling approach converge much faster than traditional loosely and tightly coupled approaches, and is able to avoid numerical instability issues due to virtual added mass effects for light, flexible structures in incompressible flow. The influence of density ratio on the FSI response, divergence and flutter speeds are presented, along with comparisons between viscous and inviscid FSI computations.

  14. Stability of limit cycles in a pluripotent stem cell dynamics model

    Energy Technology Data Exchange (ETDEWEB)

    Adimy, Mostafa [Laboratoire de Mathematiques Appliquees UMR 5142, Universite de Pau et des Pays de l' Adour, Avenue de l' universite, 64000 Pau (France)] e-mail: mostafa.adimy@univ-pau.fr; Crauste, Fabien [Laboratoire de Mathematiques Appliquees UMR 5142, Universite de Pau et des Pays de l' Adour, Avenue de l' universite, 64000 Pau (France)] e-mail: fabien.crauste@univ-pau.fr; Halanay, Andrei [Department of Mathematics 1, University Politehnica of Bucharest, Splaiul Independentei 313, RO-060042, Bucharest (Romania)] e-mail: halanay@vectron.mathem.pub.ro; Neamtu, Mihaela [Faculty of Economics, I.N. Pestalozzi 16, West University of Timisoara, RO-300115, Timisoara (Romania)] e-mail: mihaela.neamtu@fse.uvt.ro; Opris, Dumitru [Department of Applied Mathematics, Faculty of Mathematics, Bd. V. Parvan 4, West University of Timisoara, RO-300223, Timisoara (Romania)] e-mail: opris@math.uvt.ro

    2006-02-01

    This paper is devoted to the study of the stability of limit cycles of a nonlinear delay differential equation with a distributed delay. The equation arises from a model of population dynamics describing the evolution of a pluripotent stem cells population. We study the local asymptotic stability of the unique nontrivial equilibrium of the delay equation and we show that its stability can be lost through a Hopf bifurcation. We then investigate the stability of the limit cycles yielded by the bifurcation using the normal form theory and the center manifold theorem. We illustrate our results with some numerics.

  15. STUDY ON DYNAMICS, STABILITY AND CONTROL OF MULTI-BODY FLEXIBLE STRUCTURE SYSTEM IN FUNCTIONAL SPACE

    Institute of Scientific and Technical Information of China (English)

    徐建国; 贾军国

    2001-01-01

    The dynamics, stability and control problem of a kind of infinite dimensional system are studied in the functional space with the method of modern mathematics. First,the dynamical control model of the distributed parameter system with multi-body flexible and multi-topological structure was established which has damping, gyroscopic parts and constrained damping. Secondly, the necessary and sufficient condition of controllability and observability, the stability theory and asymptotic property of the system were obtained.These results expand the theory of the field about the dynamics and control of the system with multi-body flexible structure, and have important engineering significance.

  16. Microtubule Dynamicity Is More Important than Stability in Memory Formation: an In Vivo Study.

    Science.gov (United States)

    Atarod, Deyhim; Eskandari-Sedighi, Ghazaleh; Pazhoohi, Farid; Karimian, Seyed Morteza; Khajeloo, Mojtaba; Riazi, Gholam Hossein

    2015-06-01

    It has been shown that microtubule (MT) activity and dynamics can have huge impacts on synaptic plasticity and memory formation. This is mainly due to various functions of MTs in neurons; MTs are involved in dendritic spine formation, axonal transportation, neuronal polarity, and receptor trafficking. Recent studies from our group and other labs have suggested the possible role of brain MT dynamicity and activity in memory; however, there is a need for more detailed studies regarding this aspect. In this study, we have tried to evaluate the importance of microtubule dynamicity rather than stability in memory formation in vivo. In order to investigate the role of MT stability in memory formation, we treated mice with paclitaxel-a classic microtubule-stabilizing agent. We then studied the behavior of treated animals using Morris water maze (MWM) test. To measure the effect of injected paclitaxel on MT polymerization kinetics, we conducted polymerization assays on brain extracts of the same paclitaxel-treated animals. Our results show that paclitaxel treatment affects animals' memory in a negative way and treated animals behave poorly in MWM compared to control group. In addition, our kinetics studies show that MT stability is significantly increased in brain extracts from paclitaxel-treated mice, but MT dynamics is reduced. Thus, we suggest that dynamicity is a very important feature of MT protein structures, and regarding memory formation, dynamicity is more important than stability and high activity.

  17. Characterizations and thermal stability improvement of phase-change memory device containing Ce-doped GeSbTe films

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yu-Jen; Tsai, Min-Chuan; Wang, Chiung-Hsin; Hsieh, Tsung-Eong, E-mail: tehsieh@mail.nctu.edu.tw

    2012-02-29

    Phase-transition temperature of GeSbTe (GST) chalcogenide film was drastically increased from 159 to 236 Degree-Sign C by cerium (Ce) doping (up to 8.6 at.%) without altering the resistivity property of GST. Grain refinement via the solid-solution mechanism and the amplification of p-type semiconducting behavior in Ce-doped GST were observed. They were correlated with the enhancement of thermal stability and data retention property of GST as revealed by exothermal and isothermal analyses. Phase-change memory (PCM) device characterized at various temperatures revealed an effective thermal stability improvement on the threshold voltage of PCM device by Ce doping. - Highlights: Black-Right-Pointing-Pointer Ce doping increased phase-change temperature of GST from 159 to 236 Degree-Sign C. Black-Right-Pointing-Pointer No suppression of resistivity level in amorphous Ce-doped GST. Black-Right-Pointing-Pointer Resistance ratio of amorphous and crystalline Ce-doped GST was preserved at 10{sup 5}. Black-Right-Pointing-Pointer p-type semiconducting behavior of GST was enhanced by Ce-doping. Black-Right-Pointing-Pointer Ce-doping improved the thermal stability of threshold voltage of GST PCM device.

  18. Clinical experiences of dynamic stabilizers: Dynesys and Dynesys top loading system for lumbar spine degenerative disease.

    Science.gov (United States)

    Hsieh, Cheng-Ta; Chang, Chih-Ju; Su, I-Chang; Lin, Li-Ying

    2016-04-01

    Dynesys (Dynamic Neutralization System) was designed to overcome the shortcomings of fusion. The Dynesys top loading (DTL) system is a new alternative Dynesys system that can be applied via a minimally invasive procedure. This study aimed to ascertain whether DTL is a suitable device for motion preservation and prevention of instability, and to compare the clinical and radiological outcomes between DTL and Dynesys. In this study, 12 patients were treated with Dynesys and 21 patients were treated with DTL. Back and leg pain were evaluated using the visual analog scale. The Oswestry Disability Index was used to evaluate the patients' function. Range of motion (ROM) at the operative level and for the whole lumbar spine was measured pre- and postoperatively. The length of wound, blood loss, length of hospital stay, and operation duration were also compared. All patients were followed up for 12-76 months. Scores on the visual analog scale and Oswestry Disability Index were significantly improved postoperatively. The median ROM of the whole spine and index level ROM in all patients showed 12.5% and 79.6% loss, respectively. The DTL group exhibited significantly better results in terms of blood loss, wound length, and operation duration, in addition to early ambulation. In conclusion, Dynesys and DTL are semirigid fixation systems that can significantly improve clinical symptoms and signs. Our results suggested that DTL was better than Dynesys as a result of it being a minimally invasive procedure. However, further study with large sample sizes and longer follow-up durations is required to validate the effects of these dynamic stabilizers.

  19. Distributed-Order Dynamic Systems Stability, Simulation, Applications and Perspectives

    CERN Document Server

    Jiao, Zhuang; Podlubny, Igor

    2012-01-01

    Distributed-order differential equations, a generalization of fractional calculus, are of increasing importance in many fields of science and engineering from the behaviour of complex dielectric media to the modelling of nonlinear systems. This Brief will broaden the toolbox available to researchers interested in modeling, analysis, control and filtering. It contains contextual material outlining the progression from integer-order, through fractional-order to distributed-order systems. Stability issues are addressed with graphical and numerical results highlighting the fundamental differences between constant-, integer-, and distributed-order treatments. The power of the distributed-order model is demonstrated with work on the stability of noncommensurate-order linear time-invariant systems. Generic applications of the distributed-order operator follow: signal processing and viscoelastic damping of a mass–spring set up. A new general approach to discretization of distributed-order derivatives and integrals ...

  20. Static-dynamic stability of the body gymnasts qualifications

    Directory of Open Access Journals (Sweden)

    Litvinenko Y.V.

    2015-01-01

    Full Text Available Purpose: evaluation of individual ways of postural control gymnasts skilled in solving problems on the stability of the body in the motor tests. Material : The study involved engaged in gymnastics (n = 9. The measurements were carried out on the platform stabilographic Kistler. Tests used: handstand, Biryuk sample, sample Romberg. Results: set individual ways microvibrations parts of the body and makrokolebany in the sagittal and frontal planes. Joined symmetry and asymmetry postural control of the body, the various indicators of energy expenditure. The quality of postural control in the performance of motor tests were deterministic complex conditions of body position on the support, limited visual orientation. Also corresponds to the test specificity of the sport. Conclusions : The method microvibrations in solving problems on the stability of the body in the motor tests gymnasts is the most strategically important for the effective development and management of a system of regulation poses athlete. Confirmation rates are economical expenditure of energy during motor tests.

  1. Nonlinear dynamics of human locomotion: effects of rhythmic auditory cueing on local dynamic stability

    Directory of Open Access Journals (Sweden)

    Philippe eTerrier

    2013-09-01

    Full Text Available It has been observed that times series of gait parameters (stride length (SL, stride time (ST and stride speed (SS, exhibit long-term persistence and fractal-like properties. Synchronizing steps with rhythmic auditory stimuli modifies the persistent fluctuation pattern to anti-persistence. Another nonlinear method estimates the degree of resilience of gait control to small perturbations, i.e. the local dynamic stability (LDS. The method makes use of the maximal Lyapunov exponent, which estimates how fast a nonlinear system embedded in a reconstructed state space (attractor diverges after an infinitesimal perturbation. We propose to use an instrumented treadmill to simultaneously measure basic gait parameters (time series of SL, ST and SS from which the statistical persistence among consecutive strides can be assessed, and the trajectory of the center of pressure (from which the LDS can be estimated. In 20 healthy participants, the response to rhythmic auditory cueing (RAC of LDS and of statistical persistence (assessed with detrended fluctuation analysis (DFA was compared. By analyzing the divergence curves, we observed that long-term LDS (computed as the reverse of the average logarithmic rate of divergence between the 4th and the 10th strides downstream from nearest neighbors in the reconstructed attractor was strongly enhanced (relative change +47%. That is likely the indication of a more dampened dynamics. The change in short-term LDS (divergence over one step was smaller (+3%. DFA results (scaling exponents confirmed an anti-persistent pattern in ST, SL and SS. Long-term LDS (but not short-term LDS and scaling exponents exhibited a significant correlation between them (r=0.7. Both phenomena probably result from the more conscious/voluntary gait control that is required by RAC. We suggest that LDS and statistical persistence should be used to evaluate the efficiency of cueing therapy in patients with neurological gait disorders.

  2. Phase stability and dynamics of entangled polymer-nanoparticle composites.

    KAUST Repository

    Mangal, Rahul

    2015-06-05

    Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

  3. Stability of Non-Neutral and Neutral Dynamic Switched Systems Subject to Internal Delays

    Directory of Open Access Journals (Sweden)

    M. De la Sen

    2005-01-01

    Full Text Available This study deals with the quadratic stability and linear state-feedback and output-feedback stabilization of switched delayed linear dynamic systems with, in general, a finite number of non commensurate constant internal point delays. The results are obtained based on Lyapunov’s stability analysis via appropriate Krasovsky-Lyapunov’s functionals and the related stability study is performed to obtain both delay independent and delay dependent results. It is proved that the stabilizing switching rule is arbitrary if all the switched subsystems are quadratically stable and that it exists a (in general, non-unique stabilizing switching law when the system is polytopic, stable at some interior point of the polytope but with non-necessarily stable parameterizations at the vertices defining the subsystems.

  4. Dynamic stabilization methods for bilateral control of remote manipulation

    Science.gov (United States)

    Handlykken, M.

    1982-01-01

    This paper discusses and analyses several control strategies for generalized, bilateral master/slave manipulator systems. In these manipulators the two arms have different dynamic/kinematic properties which implies a more difficult control problem. Attention is focused on torque/force driven arms. Required performance for the necessary control computer(s) is discussed.

  5. Protein kinesis: The dynamics of protein trafficking and stability

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-31

    The purpose of this conference is to provide a multidisciplinary forum for exchange of state-of-the-art information on protein kinesis. This volume contains abstracts of papers in the following areas: protein folding and modification in the endoplasmic reticulum; protein trafficking; protein translocation and folding; protein degradation; polarity; nuclear trafficking; membrane dynamics; and protein import into organelles.

  6. Reverse of mixing process with a two-dimensional electro-fluid-dynamic device.

    Science.gov (United States)

    Liu, Chang; Luo, Yong; Maxwell, E Jane; Fang, Ning; Chen, David D Y

    2010-03-15

    Mixing of two solutions into one is a spontaneous process with a net increase in entropy. However, the reverse of the mixing process is usually not possible unless certain conditions are met. A continuous solution stream containing a mixture of two compounds can be separated into two channels, each containing a pure compound, thus reversing the mixing process using a two-dimensional microfluidic electro-fluid-dynamic (EFD) device. When the electric field is strategically applied in the interconnecting channels of an EFD device, the pressure required to direct an analyte into a certain channel can be calculated by using the solutions of electric field and fluid dynamics in the mass balance equation. If the pressure and electric potential at various inlets and outlets satisfy these predetermined conditions, the reverse of a mixing process is observed. Conventional microfluidic devices have been used to introduce samples from interconnecting channels or efficiently mix different solutions into a single channel. The EFD devices expand the spatial separation of analytes from one dimension to two using both the differential migration behavior of analytes and the velocity field distribution in different channel geometries. The devices designed according to these basic physicochemical principles can be used for complete processing of minute samples and to obtain pure chemical species from complex mixtures.

  7. Nyquist and Bode stability criteria to assess changes in dynamic knee stability in healthy and anterior cruciate ligament reconstructed individuals during walking.

    Science.gov (United States)

    Morgan, Kristin D; Zheng, Yanbing; Bush, Heather; Noehren, Brian

    2016-06-14

    Anterior cruciate ligament (ACL) injuries are one of the most frequently injured knee ligaments. Despite reconstruction, many individuals report difficulty returning to high level activities that require greater dynamic stability. Since few methods have been tested to assess dynamic stability post ACL reconstruction (ACLR), the purpose of this study was to evaluate between and within dynamic knee stability in control and ACLR individuals using Nyquist and Bode stability criteria. Sixteen control and sixteen post ACLR individuals performed a walking protocol. Nyquist and Bode stability criteria were implemented to classify and quantify individual step-to-step sagittal plane dynamic knee stability from the gait waveforms at initial contact, 15% and 30% of stance based on the resulting gain and phase margins. An ANOVA compared differences in phase margins between the control and ACLR limbs and found that the ACLR limbs were overall significantly more unstable than the non-reconstructed and control limbs (p=0.001). The results indicated that the ACLR individuals who exhibited stable steps adopted a more compensatory strategy aimed to stabilize the knee. These methods of evaluating dynamic knee stability may help clinicians to assess dynamic knee stability progression throughout rehabilitation and help assess return-to-sport with minimal risk to the individual.

  8. Use efficiency of dynamic stabilizer in the post-repair period of railways in Ukraine

    Directory of Open Access Journals (Sweden)

    O.V. Gubar

    2013-08-01

    Full Text Available Purpose. To analyze the interaction forces of the track and rolling stock at application of dynamic stabilizers, as well as the determination of the area, on which the track stabilization is necessary not only according to the technical indices but also according to the economic ones. Methodology.To achieve the research purpose the methods of analysis of material flows, peculiar to the places that need applications of dynamic stabilizers on railway transport tracks are used. Findings. Researches of relatively economic efficiency of dynamic stabilizers application, which were conducted by scientists during the last years, do not spread to comparison of cost of works on the track stabilizing and losses of railway for period of running. During the running period the trains move with a limited speed that causes corresponding financial losses. Speed limitation result in the both the motion time increase and in some occasions in the heavy consumption of fuel and energy resources. The more intensive track discord and expenses increase for its maintenance are observed in the sections of braking and acceleration immediately in front of and after the areas of limitation. The methodology relative to the estimation of economic efficiency of dynamic stabilizers application after completion of track repairs for the areas of Ukrainian railways with different operational conditions was developed. This methodology includes the losses calculation of railroad, which are predefined by extra motion time, heavy consumption of fuel and energy resources and charges for current maintenance. Originality. The methodology of cost effectiveness evaluating of the dynamic stabilizers application in the post-repair period was developed. Such an approach would allow one to take the rational decisions taking into account the features of the track sections, which were reconstructed. Practical value. The obtained results will rationally assign the works on the dynamic track

  9. Stabilization of chaotic and non-permanent food-web dynamics

    Science.gov (United States)

    Williams, R. J.; Martinez, N. D.

    2004-03-01

    Several decades of dynamical analyses of food-web networks[CITE] have led to important insights into the effects of complexity, omnivory and interaction strength on food-web stability[CITE]. Several recent insights[CITE] are based on nonlinear bioenergetic consumer-resource models[CITE] that display chaotic behavior in three species food chains[CITE] which can be stabilized by omnivory[CITE] and weak interaction of a fourth species[CITE]. We slightly relax feeding on low-density prey in these models by modifying standard food-web interactions known as “typeII” functional responses[CITE]. This change drastically alters the dynamics of realistic systems containing up to ten species. Our modification stabilizes chaotic dynamics in three species systems and reduces or eliminates extinctions and non-persistent chaos[CITE] in ten species systems. This increased stability allows analysis of systems with greater biodiversity than in earlier work and suggests that dynamic stability is not as severe a constraint on the structure of large food webs as previously thought. The sensitivity of dynamical models to small changes in the predator-prey functional response well within the range of what is empirically observed suggests that functional response is a crucial aspect of species interactions that must be more precisely addressed in empirical studies.

  10. Criterion for stability of a special relativistically covariant dynamical system

    Science.gov (United States)

    Horwitz, L. P.; Zucker, D.

    2017-03-01

    We study classically the problem of two relativistic particles with an invariant Duffing-like potential which reduces to the usual Duffing form in the nonrelativistic limit. We use a special relativistic generalization (RGEM) of the geometric method (GEM) developed for the analysis of nonrelativistic Hamiltonian systems to study the local stability of a relativistic Duffing oscillator. Poincaré plots of the simulated motion are consistent with the RGEM. We find a threshold for the external driving force required for chaotic behavior in the Minkowski spacetime.

  11. STUDIES ON STABILITY AND DYNAMICS OF A SWIRLING JET

    Institute of Scientific and Technical Information of China (English)

    胡国辉; 孙德军; 尹协远

    2001-01-01

    The temporal instability and nonlinear evolution of the swirling jet near a nozzle exit are studied by both normal-mode method and three dimensional direct numerical simulation (3D DNS). It is found that the swirl enhances the maximum linear growth rates for negative helical modes, while decreases the growth rate for axisymmetric mode. Numerical simulations show that the evolution in early stage is compared well with the linear stability theory. In nonlinear stage, the swirl promotes the breakup of 3D large scale organized structures in the flow into small eddies.

  12. Stability properties of a general class of nonlinear dynamical systems

    Energy Technology Data Exchange (ETDEWEB)

    Gleria, I.M. [Filho Instituto de Fisica, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, Brasilia (Brazil). E-mail: iram@ucb.br; Figueiredo, A. [Filho Instituto de Fisica, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, Brasilia (Brazil). E-mail: annibal@helium.fis.unb.br; Rocha, T.M. [Filho Instituto de Fisica, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, Brasilia (Brazil). E-mail: marciano@helium.fis.unb.br

    2001-05-04

    We establish sufficient conditions for the boundedness of the trajectories and the stability of the fixed points in a class of general nonlinear systems, the so-called quasi-polynomial vector fields, with the help of a natural embedding of such systems in a family of generalized Lotka-Volterra (LV) equations. A purely algebraic procedure is developed to determine such conditions. We apply our method to obtain new results for LV systems, by a reparametrization in time variable, and to study general nonlinear vector fields, originally far from the LV format. (author)

  13. A mobile communication device adapted to provide a dynamic display arrangement

    DEFF Research Database (Denmark)

    2011-01-01

    The invention relates to a mobile communication device comprising a light projector adapted to project a multi-coloured image onto a surface; a hinged mirror comprising a first mirror part adapted to be tilted around the hinge into the light path of the light projector; wherein the first mirror...... part comprises means for correcting a skew angle in the multi-coloured image projected onto a surface. Thereby is achieved that the mobile communication device is able to provide RGB full colour dynamic image projection which is preferred over monochromatic laser projection because it is a speckle free...

  14. Dynamic 2D-barcodes for multi-device Web session migration including mobile phones

    DEFF Research Database (Denmark)

    Alapetite, Alexandre

    2010-01-01

    This article introduces a novel Web architecture that supports session migration in multi-device Web applications, particularly the case when a user starts a Web session on a computer and wishes to continue on a mobile phone. The proposed solution for transferring the needed session identifiers...... across devices is to dynamically generate pictures of 2D-barcodes containing a Web address and a session ID in an encoded form. 2D-barcodes are a cheap, fast and robust approach to the problem. They are widely known and used in Japan, and are spreading in other countries. Variations on the topic...

  15. A new device for dynamic luminance mapping and glare risk assessment in buildings

    Science.gov (United States)

    Borisuit, Apiparn; Münch, Mirjam; Deschamps, Laurent; Kämpf, Jérôme; Scartezzini, Jean-Louis

    2012-10-01

    High dynamic range imaging has been shown to be a reliable tool to assess luminance maps and glare risk probability in buildings. However, there are some limitations of image capturing time, especially when dealing with highly dynamic and contrasted daylight situations. We used a newly developed prototype of a digital camera which contains a high dynamic range pixel array chip, with a logarithmic scale for encoding. This type of camera allows to effectively assessing luminance, contrast and contrast directions, by taking only a single image or by performing real time recordings. The device was equipped with a fisheye lens and V-lambda filters to adapt the camera's spectral sensitivity to the human eye. After spectral as well as photometric calibration and vignetting correction, the device was tested to perform luminance mapping of real scenes. The results showed that luminance maps of a room can be efficiently assessed under dynamic daylight and mixed day- and electric lighting conditions in a very short time (i.e. 100 ms), when compared to classical HDR imaging techniques. This allows us to calculate glare indexes of a scene simultaneously. The camera opens a variety of new applications as a useful tool for architects, building designers and lighting experts. The device can be used to easily monitor daylight availability and glare indexes in existing buildings and further developments for advanced (day-) lighting control can be envisaged.

  16. Location of facts devices from a dynamic perspective; Ubicacion de dispositivos FACTS desde una perspectiva dinamica

    Energy Technology Data Exchange (ETDEWEB)

    Coronado Gallegos, Ixtlahuatl

    2001-09-15

    In this work techniques for the location of FACTS devices (Flexible Systems of AC Transmission) in a multi-machine power system in order to improve the electromechanical transient behavior is presented. In the first part, a brief introduction is presented about the FACTS devices, in which are mentioned some of the main characteristics, classification and advantages that their utilization represents. In the next part, the formulation of the matrix of state in the context of machine-infinite bar considering the possibility of including a power system stabilizer is developed. Later the formulation is extended to a multi-machine system. Additionally the form of including a series capacitor controlled by thyristors (TCSC) as well as a unified controller of power flows (UPFC) is analyzed. An analysis of the UPFC is carried out in conditions of stationary and dynamic state in a system machine-infinite bar in order to know its operating characteristics and its capacity for dampening power oscillations through its entrances of control when using local signals. In the last part of the work a methodology is proposed to attack the problem of the location of FACTS devices, which is based in the technique of response to the system frequency. In order to validate this proposal some cases of study are used and the results obtained with the ones provided by other techniques are compared. Also some auxiliary means are proposed for obtaining the feasible locations utilizing other mathematical tools such as the singular values and the sensitivities. Finally, simulations in the time are carried out to corroborate the results obtained. [Spanish] En este trabajo se presentan tecnicas para la localizacion de dispositivos FACTS (Sistemas Flexibles de Transmision de C.A) en un sistema de potencia multimaquinas a fin de mejorar el comportamiento transitorio electromecanico. En la primera parte se presenta una breve introduccion acerca de los dispositivos FACTS, en la cual se mencionan

  17. STABILITY, BIFURCATIONS AND CHAOS IN UNEMPLOYMENT NON-LINEAR DYNAMICS

    Directory of Open Access Journals (Sweden)

    Pagliari Carmen

    2013-07-01

    Full Text Available The traditional analysis of unemployment in relation to real output dynamics is based on some empirical evidences deducted from Okun’s studies. In particular the so called Okun’s Law is expressed in a linear mathematical formulation, which cannot explain the fluctuation of the variables involved. Linearity is an heavy limit for macroeconomic analysis and especially for every economic growth study which would consider the unemployment rate among the endogenous variables. This paper deals with an introductive study about the role of non-linearity in the investigation of unemployment dynamics. The main idea is the existence of a non-linear relation between the unemployment rate and the gap of GDP growth rate from its trend. The macroeconomic motivation of this idea moves from the consideration of two concatenate effects caused by a variation of the unemployment rate on the real output growth rate. These two effects are concatenate because there is a first effect that generates a secondary one on the same variable. When the unemployment rate changes, the first effect is the variation in the level of production in consequence of the variation in the level of such an important factor as labour force; the secondary effect is a consecutive variation in the level of production caused by the variation in the aggregate demand in consequence of the change of the individual disposal income originated by the previous variation of production itself. In this paper the analysis of unemployment dynamics is carried out by the use of the logistic map and the conditions for the existence of bifurcations (cycles are determined. The study also allows to find the range of variability of some characteristic parameters that might be avoided for not having an absolute unpredictability of unemployment dynamics (deterministic chaos: unpredictability is equivalent to uncontrollability because of the total absence of information about the future value of the variable to

  18. Dynamic compensator design for robust stability of linear uncertain systems

    Science.gov (United States)

    Yedavalli, R. K.

    1986-01-01

    This paper presents a robust linear dynamic compensator design algorithm for linear uncertain systems whose parameters vary within given bounded sets. The algorithm explicitly incorporates the structure of the uncertainty into the design procedure and utilizes the elemental perturbation bounds developed recently. The special cases of linear state feedback and measurement feedback controllers are considered and the relative trade offs are discussed. The design algorithm is illustrated with the help of a simple example.

  19. Controllability, observability, realizability, and stability of dynamic linear systems

    OpenAIRE

    Davis, John M.; Gravagne, Ian A.; Jackson, Billy J.; Marks II, Robert J.

    2009-01-01

    We develop a linear systems theory that coincides with the existing theories for continuous and discrete dynamical systems, but that also extends to linear systems defined on nonuniform time scales. The approach here is based on generalized Laplace transform methods (e.g. shifts and convolution) from the recent work [13]. We study controllability in terms of the controllability Gramian and various rank conditions (including Kalman's) in both the time invariant and time varying settings...

  20. Stability and Dynamics in the Ukrainian Higher Danube Dialect

    Directory of Open Access Journals (Sweden)

    Maryna Delyusto

    2015-08-01

    Full Text Available The article deals with some dynamic processes in the Ukrainian dialect spoken in the village Shevchenkove, Kiliya district, Odessa region. The author establishes stables elements of its grammatical system which are indifferent towards influence of other languages, especially Russian and Romanian, towards the Ukrainian literary standard and neighboring dialects, and changeable ones, which have been modified since last investigations of this dialect.

  1. 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

  2. Interfacial Modifiers for Enhanced Stability and Reduced Degradation of Cu(In,Ga)Se2 Devices

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Ina T.; Oyster, Tricia M.; Mansfield, Lorelle M.; Matthews, Rachael; Pentzer, Emily B.; French, Roger H.; Peshek, Timothy J.

    2016-11-21

    Transparent conductive oxide (TCO) degradation is a known failure mode in thin-film photovoltaic (PV) devices through mechanisms such as resistivity increase and delamination. Here we apply thin interfacial modifiers to aluminum-doped zinc oxide (AZO) to mitigate damp heat induced degradation of electrical performance. Additionally, we demonstrate that these modifiers can be applied to the AZO front contact of a Cu(In, Ga)Se2 device without significantly degrading the device performance, a promising step towards improving the lifetime performance.

  3. Au@polymer core-shell nanoparticles for simultaneously enhancing efficiency and ambient stability of organic optoelectronic devices.

    Science.gov (United States)

    Kim, Taesu; Kang, Hyunbum; Jeong, Seonju; Kang, Dong Jin; Lee, Changyeon; Lee, Chun-Ho; Seo, Min-Kyo; Lee, Jung-Yong; Kim, Bumjoon J

    2014-10-08

    In this paper, we report and discuss our successful synthesis of monodispersed, polystyrene-coated gold core-shell nanoparticles (Au@PS NPs) for use in highly efficient, air-stable, organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). These core-shell NPs retain the dual functions of (1) the plasmonic effect of the Au core and (2) the stability and solvent resistance of the cross-linked PS shell. The monodispersed Au@PS NPs were incorporated into a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film that was located between the ITO substrate and the emitting layer (or active layer) in the devices. The incorporation of the Au@PS NPs provided remarkable improvements in the performances of both OLEDs and OPVs, which benefitted from the plasmonic effect of the Au@PS NPs. The OLED device with the Au@PS NPs achieved an enhancement of the current efficiency that was 42% greater than that of the control device. In addition, the power conversion efficiency was increased from 7.6% to 8.4% in PTB7:PC71BM-based OPVs when the Au@PS NPs were embedded. Direct evidence of the plasmonic effect on optical enhancement of the device was provided by near-field scanning optical microscopy measurements. More importantly, the Au@PS NPs induced a remarkable and simultaneous improvement in the stabilities of the OLED and OPV devices by reducing the acidic and hygroscopic properties of the PEDOT:PSS layer.

  4. Dihedral influence on lateral-directional dynamic stability on large aspect ratio tailless flying wing aircraft

    Institute of Scientific and Technical Information of China (English)

    Song Lei; Yang Hua; Zhang Yang; Zhang Haoyu; Huang Jun

    2014-01-01

    The influence of dihedral layout on lateral-directional dynamic stability of the tailless flying wing aircraft is discussed in this paper. A tailless flying wing aircraft with a large aspect ratio is selected as the object of study, and the dihedral angle along the spanwise sections is divided into three segments. The influence of dihedral layouts is studied. Based on the stability derivatives cal-culated by the vortex lattice method code, the linearized small-disturbance equations of the lateral modes are used to determine the mode dynamic characteristics. By comparing 7056 configurations with different dihedral angle layouts, two groups of stability optimized dihedral layout concepts are created. Flight quality close to Level 2 requirements is achieved in these optimized concepts without any electric stability augmentation system.

  5. Adaptive Stabilization for Uncertain Nonholonomic Dynamic Mobile Robots Based on Visual Servoing Feedback

    Institute of Scientific and Technical Information of China (English)

    YANG Fang; WANG Chao-Li

    2011-01-01

    The stabilization problem of nonholonomic dynamic mobile robots with a fixed (ceiling-mounted) camera is addressed in this paper.First,a camera-object visual servding kinematic model is introduced by utilizing the pin-hole camera model and a kinematic stabilizing controller is given for the kinematic model.Then,an adaptive sliding mode controller is designed to stabilize uncertain dynamic mobile robot in the presence of parametric uncertainties associated with the camera system.The proposed controller is robust not only to structured uncertainty such as mass variation but also to unstructured one such as disturbances.The stability of the proposed control system and the boundedness of estimated parameters are rigorously proved by Lyapunov method.Simulation results are presented to illustrate the performance of the control law.

  6. Glass-to-metal bonding process improves stability and performance of semiconductor devices

    Science.gov (United States)

    Trent, R. L.

    1970-01-01

    Anodic bonding of glass coverslips to photodiodes and photovoltaic devices eliminates the need for adhesive. The process requires relatively low temperatures /less than 560 degrees C/ and the metals and glass remain solid throughout the bonding process.

  7. Stability of dynamical systems on the role of monotonic and non-monotonic Lyapunov functions

    CERN Document Server

    Michel, Anthony N; Liu, Derong

    2015-01-01

    The second edition of this textbook provides a single source for the analysis of system models represented by continuous-time and discrete-time, finite-dimensional and infinite-dimensional, and continuous and discontinuous dynamical systems.  For these system models, it presents results which comprise the classical Lyapunov stability theory involving monotonic Lyapunov functions, as well as corresponding contemporary stability results involving non-monotonicLyapunov functions.Specific examples from several diverse areas are given to demonstrate the applicability of the developed theory to many important classes of systems, including digital control systems, nonlinear regulator systems, pulse-width-modulated feedback control systems, and artificial neural networks.   The authors cover the following four general topics:   -          Representation and modeling of dynamical systems of the types described above -          Presentation of Lyapunov and Lagrange stability theory for dynamical sy...

  8. Dynamic Stability of Viscoelastic Plates with Finite Deformation and Shear Effects

    Institute of Scientific and Technical Information of China (English)

    李晶晶; 程昌钧; 等

    2002-01-01

    Based on Reddy's theory of plates with higher-order shear deformations and the Boltzmann superposition principles,the governing equations were established for dynamic stability of viscoelastic plates with finite deformations taking account of shear effects,The Galerkin method was applied to simplify the set of equations.The numerical methods in nonlinear dynamics were used to solve the simplified system.It could e seen that there are plenty of dynamic properties for this kind of viscoelastic plates under transverse harmonic loads.The influences of the transverse shear deformations and material parameter on the dynamic behavior of nonlinear viscoelatic plates were investigated.

  9. Dynamical observations of self-stabilizing stationary light

    Science.gov (United States)

    Everett, J. L.; Campbell, G. T.; Cho, Y.-W.; Vernaz-Gris, P.; Higginbottom, D. B.; Pinel, O.; Robins, N. P.; Lam, P. K.; Buchler, B. C.

    2017-01-01

    The precise control of atom-light interactions is vital to many quantum technologies. For instance, atomic systems can be used to slow and store light, acting as a quantum memory. Optical storage can be achieved via stopped light, where no optical energy continues to exist in the atomic system, or as stationary light, where some optical energy remains present during storage. Here, we demonstrate a form of self-stabilizing stationary light. From any initial state, our atom-light system evolves to a stable configuration that may contain bright optical excitations trapped within the atomic ensemble. This phenomenon is verified experimentally in a cloud of cold Rb87 atoms. The spinwave in our atomic cloud is imaged from the side, allowing direct comparison with theoretical predictions.

  10. Stability of a time discrete perturbed dynamical system with delay

    Directory of Open Access Journals (Sweden)

    Michael I. Gil'

    1999-01-01

    Full Text Available Let Cn be the set of n complex vectors endowed with a norm ‖⋅‖Cn. Let A,B be two complex n×n matrices and τ a positive integer. In the present paper we consider the nonlinear difference equation with delay of the type uk+1=Auk+Buk−τ+Fk(uk,uk−τ,      k=0,1,2,…, where Fk:Cn×Cn→Cn satisfies the condition ‖Fk(x,y‖Cn≤p‖x‖Cn+q‖y‖Cn,       k=0,1,2,…, where p and q are positive constants. In this paper, absolute stability conditions for this equation are established.

  11. The dynamics of CRM attitude change: Attitude stability

    Science.gov (United States)

    Gregorich, Steven E.

    1993-01-01

    Special training seminars in cockpit resource management (CRM) are designed to enhance crew effectiveness in multicrew air-transport cockpits. In terms of CRM, crew effectiveness is defined by teamwork rather than technical proficiency. These seminars are designed to promote factual learning, alter aviator attitudes, and motivate aviators to make use of what they have learned. However, measures of attitude change resulting from CRM seminars have been the most common seminar evaluation technique. The current investigation explores a broader range of attitude change parameters with specific emphasis on the stability of change between recurrent visits to the training center. This allows for a comparison of training program strengths in terms of seminar ability to effect lasting change.

  12. Stability mechanisms of a thermophilic laccase probed by molecular dynamics

    DEFF Research Database (Denmark)

    Christensen, Niels Johan; Kepp, Kasper Planeta

    2013-01-01

    to variable ionic strengths, temperatures, and glycosylation status. Near-physiological conditions provided excellent agreement with the crystal structure (average RMSD ∼0.92 Å) and residual agreement with experimental B-factors. The persistence of backbone hydrogen bonds was identified as a key descriptor...... of structural response to environment, whereas solvent-accessibility, radius of gyration, and fluctuations were only locally relevant. Backbone hydrogen bonds decreased systematically with temperature in all simulations (∼9 per 50 K), probing structural changes associated with enthalpy-entropy compensation....... Approaching T opt (∼350 K) from 300 K, this change correlated with a beginning "unzipping" of critical β-sheets. 0 M ionic strength triggered partial denucleation of the C-terminal (known experimentally to be sensitive) at 400 K, suggesting a general salt stabilization effect. In contrast, F(-) (but not Cl...

  13. Stability analysis of associative memory network composed of stochastic neurons and dynamic synapses.

    Science.gov (United States)

    Katori, Yuichi; Otsubo, Yosuke; Okada, Masato; Aihara, Kazuyuki

    2013-01-01

    We investigate the dynamical properties of an associative memory network consisting of stochastic neurons and dynamic synapses that show short-term depression and facilitation. In the stochastic neuron model used in this study, the efficacy of the synaptic transmission changes according to the short-term depression or facilitation mechanism. We derive a macroscopic mean field model that captures the overall dynamical properties of the stochastic model. We analyze the stability and bifurcation structure of the mean field model, and show the dependence of the memory retrieval performance on the noise intensity and parameters that determine the properties of the dynamic synapses, i.e., time constants for depressing and facilitating processes. The associative memory network exhibits a variety of dynamical states, including the memory and pseudo-memory states, as well as oscillatory states among memory patterns. This study provides comprehensive insight into the dynamical properties of the associative memory network with dynamic synapses.

  14. Diversity, Stability, Recursivity, and Rule Generation in Biological System Intra-inter Dynamics Approach

    CERN Document Server

    Kaneko, K

    1998-01-01

    Basic problems for the construction of a scenario for the Life are discussed. To study the problems in terms of dynamical systems theory, a scheme of intra-inter dynamics is presented. It consists of internal dynamics of a unit, interaction among the units, and the dynamics to change the dynamics itself, for example by replication (and death) of units according to their internal states. Applying the dynamics to cell differentiation, isologous diversification theory is proposed. According to it, orbital instability leads to diversified cell behaviors first. At the next stage, several cell types are formed, first triggered by clustering of oscillations, and then as attracting states of internal dynamics stabilized by the cell-to-cell interaction. At the third stage, the differentiation is determined as a recursive state by cell division. At the last stage, hierarchical differentiation proceeds, with the emergence of stochastic rule for the differentiation to sub-groups, where regulation of the probability for t...

  15. APPROACH FOR LAYOUT OPTIMIZATION OF TRUSS STRUCTURES WITH DISCRETE VARIABLES UNDER DYNAMIC STRESS, DISPLACEMENT AND STABILITY CONSTRAINTS

    Institute of Scientific and Technical Information of China (English)

    SHI Lian-shuan; WANG Yue-fang; SUN Huan-chun

    2006-01-01

    A mathematical model was developed for layout optimization of truss structures with discrete variables subjected to dynamic stress, dynamic displacement and dynamic stability constraints. By using the quasi-static method, the mathematical model of structure optimization under dynamic stress, dynamic displacement and dynamic stability constraints were transformed into one subjected to static stress, displacement and stability constraints. The optimization procedures include two levels, i.e., the topology optimization and the shape optimization. In each level, the comprehensive algorithm was used and the relative difference quotients of two kinds of variables were used to search the optimum solution. A comparison between the optimum results of model with stability constraints and the optimum results of model without stability constraint was given. And that shows the stability constraints have a great effect on the optimum solutions.

  16. Study on dynamic anti-sliding stability of a high gravity dam considering complex dam foundation

    OpenAIRE

    Deng-hong CHEN; Cheng-bin DU

    2011-01-01

    There existed some limitations when analyzing the anti-sliding seismic stability of dam-foundation system by traditional pseudo-static method and response spectrum method. The dynamic strength reduction method was used to study on the deep anti-sliding stability of a high gravity dam considering complex dam foundation under strong earthquake-induced ground action. The static analysis was firstly carried out by reducing the shear strength parameters of the dam foundation’s rock mass with equal...

  17. Adaptive Stabilization for a Class of Dynamical Systems with Nonlinear Delayed State Perturbations

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The problem of adaptive stabilization for a class of systems with nonlinear delayed state perturbations is considered. The bound of the perturbations is assumed to be unknown, by using the adaptive control method, an adaptive controller is designed. Based on the Lyapunov- Karasovskii functional, it is shown that the dynamical system can be stabilized by the adaptive controller. The effectiveness of the proposed controller is demonstrated by some simulations.

  18. ANALYSIS ON STABILITY OF AN AUTONOMOUS DYNAMICS SYSTEM FOR SARS EPIDEMIC

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shuang-de; HAO Hai

    2005-01-01

    An extended dynamic model for SARS epidemic was deduced on the basis of the K-M infection model with taking the density constraint of susceptible population and the cure and death rates of patients into consideration. It is shown that the infectionfree equilibrium is the global asymptotic stability under given conditions, and endemic equilibrium is not the asymptotic stability. It comes to the conclusion that the epidemic system is the permanent persistence existence under appropriate conditions.

  19. Population dynamics and the ecological stability of obligate pollination mutualisms

    Science.gov (United States)

    Holland, J. Nathaniel; DeAngelis, Donald L.

    2001-01-01

    Mutualistic interactions almost always produce both costs and benefits for each of the interacting species. It is the difference between gross benefits and costs that determines the net benefit and the per-capita effect on each of the interacting populations. For example, the net benefit of obligate pollinators, such as yucca and senita moths, to plants is determined by the difference between the number of ovules fertilized from moth pollination and the number of ovules eaten by the pollinator's larvae. It is clear that if pollinator populations are large, then, because many eggs are laid, costs to plants are large, whereas, if pollinator populations are small, gross benefits are low due to lack of pollination. Even though the size and dynamics of the pollinator population are likely to be crucial, their importance has been neglected in the investigation of mechanisms, such as selective fruit abortion, that can limit costs and increase net benefits. Here, we suggest that both the population size and dynamics of pollinators are important in determining the net benefits to plants, and that fruit abortion can significantly affect these. We develop a model of mutualism between populations of plants and their pollinating seed-predators to explore the ecological consequences of fruit abortion on pollinator population dynamics and the net effect on plants. We demonstrate that the benefit to a plant population is unimodal as a function of pollinator abundance, relative to the abundance of flowers. Both selective abortion of fruit with eggs and random abortion of fruit, without reference to whether they have eggs or not, can limit pollinator population size. This can increase the net benefits to the plant population by limiting the number of eggs laid, if the pollination rate remains high. However, fruit abortion can possibly destabilize the pollinator population, with negative consequences for the plant population.

  20. Postdistraction stability of hypoplastic maxilla in unilateral cleft lip and palate treated using rigid external distraction device: An audit

    Directory of Open Access Journals (Sweden)

    Prasanna Kumar

    2015-01-01

    Full Text Available Introduction: Maxillary hypoplasia resulting in skeletal class III malocclusion is common among patients with cleft lip and palate. Large anteroposterior discrepancies and surgical scaring often leads to unpredictable stability of maxillary advancement with Le Fort I osteotomy and is known for a high degree of relapse. The aim of this retrospective study was to evaluate the postdisraction stability after 1-year of maxillary advancement done with rigid external distraction (RED device in patients with unilateral cleft lip and palate. Materials and Methods: Records of 11 cases treated with RED device used for distraction of maxilla in cleft lip and palate cases were assessed. Lateral cephalograms selected were taken at the end of presurgical (T1, immediate postdistraction (T2 and 1-year postdistraction (T3. Five angular measurements and nine linear measurements were used to assess the position of maxilla in all three planes. P values were obtained for repeated measurement by analysis of variance with Bonferroni′s correction for multiple comparisons. Normality was tested using Shapiro-Wilk′s test. Results: The average 1-year postdistraction measurements (T3 did not differ significantly compared to the corresponding average postdistraction measurements (T2 (P > 0.05. Conclusion: Midface distraction with RED device provides a significant structural improvement for patients with cleft lip and palate. There was marked an improvement in dentofacial structures and results were stable during the retention phase.

  1. Stabilization of Quantum Information A Unified Dynamical-Algebraic Approach

    CERN Document Server

    Zanardi, P

    2002-01-01

    The notion of symmetry is shown to be at the heart of all error correction/avoidance strategies for preserving quantum coherence of an open quantum system S e.g., a quantum computer. The existence of a non-trivial group of symmetries of the dynamical algebra of S provides state-space sectors immune to decoherence. Such noiseless sectors, that can be viewed as a noncommutative version of the pointer basis, are shown to support universal quantum computation and to be robust against perturbations. When the required symmetry is not present one can generate it artificially resorting to active symmetrization procedures.

  2. Dynamic stability of locomotor respiratory coupling during cycling in humans.

    Science.gov (United States)

    Villard, Sébastien; Casties, Jean-François; Mottet, Denis

    2005-08-05

    We explored the locomotor respiratory coupling (LRC) during a 50-min constant-load submaximal cycling exercise. A 4-week recombinant human erythropoietin (r-HuEPO) treatment improved participants' aerobic capabilities, but did not elicit significant changes in LRC. The distributions of the respiratory frequency over pedalling frequency ratios were systematically bimodal, with a preferred use of 1/3 and 1/2, and a progressive shift of the higher mode from 1/3 towards 1/2 with exercise duration. These results are interpreted in the framework of the sine circle map as the result of coordination dynamics between the physiological subsystems involved in the breathing pedalling cooperation.

  3. Investigating the fluid dynamics of rapid processes within microfluidic devices using bright-field microscopy.

    Science.gov (United States)

    Pirbodaghi, Tohid; Vigolo, Daniele; Akbari, Samin; deMello, Andrew

    2015-05-07

    The widespread application of microfluidic devices in the biological and chemical sciences requires the implementation of complex designs and geometries, which in turn leads to atypical fluid dynamic phenomena. Accordingly, a complete understanding of fluid dynamics in such systems is key in the facile engineering of novel and efficient analytical tools. Herein, we present an accurate approach for studying the fluid dynamics of rapid processes within microfluidic devices using bright-field microscopy with white light illumination and a standard high-speed camera. Specifically, we combine Ghost Particle Velocimetry and the detection of moving objects in automated video surveillance to track submicron size tracing particles via cross correlation between the speckle patterns of successive images. The efficacy of the presented technique is demonstrated by measuring the flow field over a square pillar (80 μm × 80 μm) in a 200 μm wide microchannel at high volumetric flow rates. Experimental results are in excellent agreement with those obtained via computational fluid dynamics simulations. The method is subsequently used to study the dynamics of droplet generation at a flow focusing microfluidic geometry. A unique feature of the presented technique is the ability to perform velocimetry analysis of high-speed phenomena, which is not possible using micron-resolution particle image velocimetry (μPIV) approaches based on confocal or fluorescence microscopy.

  4. Modeling and Experimental Tests of a Mechatronic Device to Measure Road Profiles Considering Impact Dynamics

    DEFF Research Database (Denmark)

    Souza, A.; Santos, Ilmar

    2002-01-01

    profile by means of gravitational and spring forces. Accelerometers are attached above the rolling wheels and the wheels follow the profiles of a rough ground. After integrating the acceleration signal twice and measuring the vehicle displacement the road profiles can be achieved. It is important...... to highlight that the aim of this device is to independently measure two road profiles, without the influence of the vehicle dynamics where the mechanism is attached. Before the mechatronic mechanism is attached to a real vehicle, its dynamic behavior must be known. A theoretical analysis of the mechanism...

  5. In operandi observation of dynamic annealing: A case study of boron in germanium nanowire devices

    Energy Technology Data Exchange (ETDEWEB)

    Koleśnik-Gray, Maria M.; Krstić, Vojislav, E-mail: vojislav.krstic@fau.de [Department of Physics, Chair for Applied Physics, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Staudtstr. 7, 91058 Erlangen (Germany); Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), and AMBER at CRANN, Trinity College Dublin, College Green, Dublin 2 (Ireland); School of Physics, Trinity College Dublin, College Green, Dublin 2 (Ireland); Sorger, Christian; Weber, Heiko B. [Department of Physics, Chair for Applied Physics, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Staudtstr. 7, 91058 Erlangen (Germany); Biswas, Subhajit; Holmes, Justin D. [Materials Chemistry and Analysis Group, Department of Chemistry, Tyndall Institute, University College Cork, Cork (Ireland); Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), and AMBER at CRANN, Trinity College Dublin, College Green, Dublin 2 (Ireland)

    2015-06-08

    We report on the implantation of boron in individual, electrically contacted germanium nanowires with varying diameter and present a technique that monitors the electrical properties of a single device during implantation of ions. This method gives improved access to study the dynamic annealing ability of the nanowire at room temperature promoted by its quasi-one-dimensional confinement. Based on electrical data, we find that the dopant activation efficiency is nontrivially diameter dependent. As the diameter decreases, a transition from a pronounced dynamic-annealing to a radiation-damage dominated regime is observed.

  6. A wearable mobility device for the blind using retina-inspired dynamic vision sensors.

    Science.gov (United States)

    Ghaderi, Viviane S; Mulas, Marcello; Pereira, Vinicius Felisberto Santos; Everding, Lukas; Weikersdorfer, David; Conradt, Jorg

    2015-01-01

    Proposed is a prototype of a wearable mobility device which aims to assist the blind with navigation and object avoidance via auditory-vision-substitution. The described system uses two dynamic vision sensors and event-based information processing techniques to extract depth information. The 3D visual input is then processed using three different strategies, and converted to a 3D output sound using an individualized head-related transfer function. The performance of the device with different processing strategies is evaluated via initial tests with ten subjects. The outcome of these tests demonstrate promising performance of the system after only very short training times of a few minutes due to the minimal encoding of outputs from the vision sensors which are translated into simple sound patterns easily interpretable for the user. The envisioned system will allow for efficient real-time algorithms on a hands-free and lightweight device with exceptional battery life-time.

  7. Simulation of Droplet Dynamics and Mixing in Microfluidic Devices Using a VOF-Based Method

    Directory of Open Access Journals (Sweden)

    Anurag CHANDORKAR

    2009-10-01

    Full Text Available This paper demonstrates that the Volume of Fluid (TruVOF® method in FLOW-3D® general purpose CFD software is an effective tool for studying droplet dynamics and mixing in microfluidic devices. The first example studied is a T-junction where flow patterns for both droplet generation and passive mixing are analyzed. The second example studied is a co-flowing device where the formation and breakup of bubbles is simulated. The effect of viscosity on bubble formation is also analyzed. For a T-junction the bubble size is corroborated with experimental data. Both the bubble size and frequency are studied and corroborated with experimental data for a co-flowing device. The third example studied is the electrowetting phenomenon observed in a small water droplet resting on a dielectric material. The steady-state contact angle is plotted against the voltage applied. The results are compared with both the Young-Lippmann curve and experimental results.

  8. Intensification of heat exchange in a device for gas-dynamic energy separation

    Science.gov (United States)

    Leontiev, A. I.; Burtsev, S. A.

    2016-11-01

    The operating efficiency of a gas-dynamic energy-separation device is analyzed, and it is shown that it can be improved if we deposit a regular relief on the wall separating the supersonic and subsonic channels. To decrease the total pressure losses on the side of the supersonic channel, shallow spherical dimples (stampings) are deposited, creating spherical ledges in the subsonic channel because of the small thickness of the wall. The calculation technique is modernized, and modeling is carried out, which shows that by introducing intensified heat exchange, it is possible to improve the efficiency of this device by 1.2-1.4 times in air and in natural gas with a simultaneous decrease in the device size by 20-25%.

  9. A microfluidic device for the study of the orientational dynamics of microrods

    CERN Document Server

    Mishra, Y N; John, O A; Andersson, P; Mehlig, B; Hanstorp, D

    2012-01-01

    We describe a microfluidic device for studying the orientational dynamics of microrods. The device enables us to experimentally investigate the tumbling of microrods immersed in the shear flow in a microfluidic channel with a depth of 400 mu and a width of 2.5 mm. The orientational dynamics was recorded using a 20 X microscopic objective and a CCD camera. The microrods were produced by shearing microdroplets of photocurable epoxy resin. We show different examples of empirically observed tumbling. On the one hand we find that short stretches of the experimentally determined time series are well described by fits to solutions of Jeffery's approximate equation of motion [Jeffery, Proc. R. Soc. London. 102 (1922), 161-179]. On the other hand we find that the empirically observed trajectories drift between different solutions of Jeffery's equation. We discuss possible causes of this orbit drift.

  10. Evaluating the stability of pharmacophore features using molecular dynamics simulations.

    Science.gov (United States)

    Wieder, Marcus; Perricone, Ugo; Boresch, Stefan; Seidel, Thomas; Langer, Thierry

    2016-02-12

    Molecular dynamics simulations of twelve protein-ligand systems were used to derive a single, structure based pharmacophore model for each system. These merged models combine the information from the initial experimental structure and from all snapshots saved during the simulation. We compared the merged pharmacophore models with the corresponding PDB pharmacophore models, i.e., the static models generated from an experimental structure in the usual manner. The frequency of individual features, of feature types and the occurrence of features not present in the static model derived from the experimental structure were analyzed. We observed both pharmacophore features not visible in the traditional approach, as well as features which disappeared rapidly during the molecular dynamics simulations and which may well be artifacts of the initial PDB structure-derived pharmacophore model. Our approach helps mitigate the sensitivity of structure based pharmacophore models to the single set of coordinates present in the experimental structure. Further, the frequency with which specific features occur during the MD simulation may aid in ranking the importance of individual features.

  11. Bacterial dynamics in steady-state biofilters: beyond functional stability.

    Science.gov (United States)

    Cabrol, Léa; Malhautier, Luc; Poly, Franck; Lepeuple, Anne-Sophie; Fanlo, Jean-Louis

    2012-01-01

    The spatial and temporal dynamics of microbial community structure and function were surveyed in duplicated woodchip-biofilters operated under constant conditions for 231 days. The contaminated gaseous stream for treatment was representative of composting emissions, included ammonia, dimethyl disulfide and a mixture of five oxygenated volatile organic compounds. The community structure and diversity were investigated by denaturing gradient gel electrophoresis on 16S rRNA gene fragments. During the first 42 days, microbial acclimatization revealed the influence of operating conditions and contaminant loading on the biofiltration community structure and diversity, as well as the limited impact of inoculum compared to the greater persistence of the endogenous woodchip community. During long-term operation, a high and stable removal efficiency was maintained despite a highly dynamic microbial community, suggesting the probable functional redundancy of the community. Most of the contaminant removal occurred in the first compartment, near the gas inlet, where the microbial diversity was the highest. The stratification of the microbial structures along the filter bed was statistically correlated to the longitudinal distribution of environmental conditions (selective pressure imposed by contaminant concentrations) and function (contaminant elimination capacity), highlighting the central role of the bacterial community. The reproducibility of microbial succession in replicates suggests that the community changes were presumably driven by a deterministic process.

  12. The dynamics of mobile promoters: Enhanced stability in promoter regions.

    Science.gov (United States)

    Rabbani, Mahnaz; Wahl, Lindi M

    2016-10-21

    Mobile promoters are emerging as a new class of mobile genetic elements, first identified by examining prokaryote genome sequences, and more recently confirmed by experimental observations in bacteria. Recent datasets have identified over 40,000 putative mobile promoters in sequenced prokaryote genomes, however only one-third of these are in regions of the genome directly upstream from coding sequences, that is, in promoter regions. The presence of many promoter sequences in non-promoter regions is unexplained. Here we develop a general mathematical model for the dynamics of mobile promoters, extending previous work to capture the dynamics both within and outside promoter regions. From this general model, we apply rigorous model selection techniques to identify which parameters are statistically justified in describing the available mobile promoter data, and find best-fit values of these parameters. Our results suggest that high rates of horizontal gene transfer maintain the population of mobile promoters in promoter regions, and that once established at these sites, mobile promoters are rarely lost, but are commonly copied to other genomic regions. In contrast, mobile promoter copies in non-promoter regions are more numerous and more volatile, experiencing substantially higher rates of duplication, loss and diversification.

  13. Dynamic characteristics and seismic stability of expanded polystyrene geofoam embankments

    Science.gov (United States)

    Amini, Zahra A.

    Expanded Polystyrene (EPS) geofoam has become a preferred material in various construction applications due to its light weight. Application of EPS accelerates the projects particularly on soft soils. The focus of this research is on the application of the EPS in embankments and its behavior mainly under harmonic vibration. The goal of this study was to investigate dynamic characteristics of freestanding vertical EPS geofoam embankment and address potential seismic issues that result from the distinguished dynamic behavior of such systems due to the layered and discrete block structure. A series of experimental studies on EPS 19 and a commercially available adhesive was conducted. Two-dimensional numerical analyses were performed to replicate the response of EPS geofoam embankment to horizontal and vertical harmonic motions. The results of the analyses have shown that for some acceleration amplitude levels interlayer sliding is expected to occur in EPS geofoam embankments almost immediately after the start of the base excitation; however, as a highly efficient energy dissipation mechanism sliding ceases rapidly. Shear keys and adhesive may be used to prevent interlayer sliding if they cover the proper extent of area of the embankment. EPS blocks placed in the corners of the embankment and at the edges of the segment prohibited from sliding may experience high stress concentrations. The embankment may show horizontal sway and rocking once sliding is prevented.

  14. Radio galaxies radiation transfer, dynamics, stability and evolution of a synchrotron plasmon

    CERN Document Server

    Pacholczyk, A G

    1977-01-01

    Radio Galaxies: Radiation Transfer, Dynamics, Stability and Evolution of a Synchrotron Plasmon deals with the physics of a region in space containing magnetic field and thermal and relativistic particles (a plasmon). The synchrotron emission and absorption of this region are discussed, along with the properties of its spectrum; its linear and circular polarization; transfer of radiation through such a region; its dynamics and expansion; and interaction with external medium.Comprised of eight chapters, this volume explores the stability, turbulence, and acceleration of particles in a synchrotro

  15. Guidelines for Computing Longitudinal Dynamic Stability Characteristics of a Subsonic Transport

    Science.gov (United States)

    Thompson, Joseph R.; Frank, Neal T.; Murphy, Patrick C.

    2010-01-01

    A systematic study is presented to guide the selection of a numerical solution strategy for URANS computation of a subsonic transport configuration undergoing simulated forced oscillation about its pitch axis. Forced oscillation is central to the prevalent wind tunnel methodology for quantifying aircraft dynamic stability derivatives from force and moment coefficients, which is the ultimate goal for the computational simulations. Extensive computations are performed that lead in key insights of the critical numerical parameters affecting solution convergence. A preliminary linear harmonic analysis is included to demonstrate the potential of extracting dynamic stability derivatives from computational solutions.

  16. STABILITY AND BIFURCATION BEHAVIORS ANALYSIS IN A NONLINEAR HARMFUL ALGAL DYNAMICAL MODEL

    Institute of Scientific and Technical Information of China (English)

    WANG Hong-li; FENG Jian-feng; SHEN Fei; SUN Jing

    2005-01-01

    A food chain made up of two typical algae and a zooplankton was considered. Based on ecological eutrophication, interaction of the algal and the prey of the zooplankton, a nutrient nonlinear dynamic system was constructed. Using the methods of the modern nonlinear dynamics, the bifurcation behaviors and stability of the model equations by changing the control parameter r were discussed. The value of r for bifurcation point was calculated, and the stability of the limit cycle was also discussed. The result shows that through quasi-periodicity bifurcation the system is lost in chaos.

  17. Dynamical stabilization by phonon-phonon interaction exemplified in cubic zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Souvatsos, [etrps G [Los Alamos National Laboratory; Rudin, Sven P [Los Alamos National Laboratory

    2008-01-01

    Cubic zirconia exhibits a soft phonon mode (X{sup -}{sub 2}), which becomes dynamically unstable at low temperatures. Previous ab initio invest.igations into the temperature-induced stabilization of the soft mode treated it as an independent anharmonic oscillator. Calculations presented here, using the self consistent ab initio lattice dynamical (SCAILD) method to evaluate the phonons at 2570 K, show that the soft mode should not be treated independently of other phonon modes. Phonon-phonon interactions stabilize the X{sup -}{sub 2} mode. Furthermore, the effective potential experienced by the mode takes on a quadratic form.

  18. Suture-Button Device Stabilization Following Ring Finger Ray Amputation: A Comparative Cadaver Study.

    Science.gov (United States)

    Morgan, Emily N; Means, Kenneth R; Paez, Adrian G; Parks, Brent G; Innis, Peter C

    2017-06-01

    The purpose of this study was to determine whether placing the suture-button device between the long and small finger metacarpals following ring finger ray amputation may better close the intermetacarpal gap and allow early range of motion without increasing the risk of malrotation than soft tissue repair alone. We performed ray amputation of the ring finger of 14 cadaver specimens by performing an osteotomy of the base of the ring finger metacarpal and then excising the remainder of the digit. We first performed a soft tissue repair of the transverse metacarpal ligaments and then cycled the fingers in simulated active flexion and extension on a custom computer-controlled device to re-create 6 weeks of range of motion. We then placed a suture-button device across the long and small finger metacarpals and tested the specimens again, thereby using each hand as an internal control. The distance between the ring and small finger metacarpals was reduced following suture-button device placement compared with the initial control; this spacing was maintained following complete cycling of the fingers. The angle between the metacarpals was divergent following soft tissue repair, and then became slightly convergent after insertion of the suture-button device. None of the hands developed clinically relevant scissoring of the digits before or after application of the suture-button device. The suture-button device provides stable fixation to withstand early range of motion following ring finger ray amputation and significantly closes the gap and angle between the adjacent metacarpals without causing scissoring.

  19. On Hamiltonian Magnetohydrodynamics: Lagrangian, Eulerian, and Dynamically Accessible Stability - Applications with Translation Symmetry

    Science.gov (United States)

    Morrison, P. J.; Andreussi, T.; Pegoraro, F.

    2016-10-01

    In a series of papers we have investigated general properties of equilibria and their stability in each of the Lagrangian, Eulerian, and Dynamically Accessible stability formulations of magnetohydrodynamics. In our latest work we compare and contrast stability results with these formulations for two applications: stratified convection and rotating pinch equilibrium configurations. The former example, emphasizes the role played entropy, while the later demonstrates the utility of a relabeling transformation that we introduced in our earlier work. Comparisons to classical works, in particular on interchange instability, are made. DOE DE-FG02-04ER-54742.

  20. Dynamic Hand Gesture Recognition for Wearable Devices with Low Complexity Recurrent Neural Networks

    OpenAIRE

    Shin, Sungho; Sung, Wonyong

    2016-01-01

    Gesture recognition is a very essential technology for many wearable devices. While previous algorithms are mostly based on statistical methods including the hidden Markov model, we develop two dynamic hand gesture recognition techniques using low complexity recurrent neural network (RNN) algorithms. One is based on video signal and employs a combined structure of a convolutional neural network (CNN) and an RNN. The other uses accelerometer data and only requires an RNN. Fixed-point optimizat...

  1. Dynamical aspects on FEL interaction in single passage and storage ring devices

    Energy Technology Data Exchange (ETDEWEB)

    Dattoli, G.; Renieri, A. [ENEA, Frascati (Italy)

    1995-12-31

    The dynamical behaviour of the free-electron lasers is investigated using appropriate scaling relations valid for devices operating in the low and high gain regimes, including saturation. The analysis is applied to both single passage and storage ring configurations. In the latter case the interplay between the interaction of the electron bean with the laser field and with the accelerator environment is investigated. In particular we discuss the effect of FEL interaction on the microwave instability.

  2. Recent Advances in Heliogyro Solar Sail Structural Dynamics, Stability, and Control Research

    Science.gov (United States)

    Wilkie, W. Keats; Warren, Jerry E.; Horta, Lucas G.; Lyle, Karen H.; Juang, Jer-Nan; Gibbs, S. Chad; Dowell, Earl H.; Guerrant, Daniel V.; Lawrence, Dale

    2015-01-01

    Results from recent NASA sponsored research on the structural dynamics, stability, and control characteristics of heliogyro solar sails are summarized. Specific areas under investigation include coupled nonlinear finite element analysis of heliogyro membrane blade with solar radiation pressure effects, system identification of spinning membrane structures, and solarelastic stability analysis of heliogyro solar sails, including stability during blade deployment. Recent results from terrestrial 1-g blade dynamics and control experiments on "rope ladder" membrane blade analogs, and small-scale in vacuo system identification experiments with hanging and spinning high-aspect ratio membranes will also be presented. A low-cost, rideshare payload heliogyro technology demonstration mission concept is used as a mission context for these heliogyro structural dynamics and solarelasticity investigations, and is also described. Blade torsional dynamic response and control are also shown to be significantly improved through the use of edge stiffening structural features or inclusion of modest tip masses to increase centrifugal stiffening of the blade structure. An output-only system identification procedure suitable for on-orbit blade dynamics investigations is also developed and validated using ground tests of spinning sub-scale heliogyro blade models. Overall, analytical and experimental investigations to date indicate no intractable stability or control issues for the heliogyro solar sail concept.

  3. Nonlinear Slewing Spacecraft Control Based on Exergy, Power Flow, and Static and Dynamic Stability

    Science.gov (United States)

    Robinett, Rush D.; Wilson, David G.

    2009-10-01

    This paper presents a new nonlinear control methodology for slewing spacecraft, which provides both necessary and sufficient conditions for stability by identifying the stability boundaries, rigid body modes, and limit cycles. Conservative Hamiltonian system concepts, which are equivalent to static stability of airplanes, are used to find and deal with the static stability boundaries: rigid body modes. The application of exergy and entropy thermodynamic concepts to the work-rate principle provides a natural partitioning through the second law of thermodynamics of power flows into exergy generator, dissipator, and storage for Hamiltonian systems that is employed to find the dynamic stability boundaries: limit cycles. This partitioning process enables the control system designer to directly evaluate and enhance the stability and performance of the system by balancing the power flowing into versus the power dissipated within the system subject to the Hamiltonian surface (power storage). Relationships are developed between exergy, power flow, static and dynamic stability, and Lyapunov analysis. The methodology is demonstrated with two illustrative examples: (1) a nonlinear oscillator with sinusoidal damping and (2) a multi-input-multi-output three-axis slewing spacecraft that employs proportional-integral-derivative tracking control with numerical simulation results.

  4. Effect of midsole thickness of dance shoes on dynamic postural stability.

    Science.gov (United States)

    Wyon, Matthew A; Cloak, Ross; Lucas, Josephine; Clarke, Frances

    2013-12-01

    Landing from jumps is one of the main causes of injury within dance. A number of studies have reported a negative effect of shoe midsole thickness on lower limb kinematics during running due to the reduction in afferent sensory outputs from the foot's epithelium. The purpose of this study was to examine the influence of varying midsole thicknesses in dance shoes on dynamic postural stability during a single-leg landing. Twenty-eight female undergraduate dance participants volunteered for the study. They carried out three trials under four conditions: barefoot and in ballet flats (2 mm midsole thickness), jazz shoes (7 mm), and dance sneakers (30 mm). The task consisted of a single-leg forward jump over a hurdle at 50% of their maximal vertical jump height, landing on a force platform, and balancing for 3 seconds. The stability indices for vertical stability (VSI), anterior-posterior stability (APSI), medial-lateral stability (MLSI), and dynamic postural stability (DPSI) were calculated using Wikstrom's revised method. Significant differences were reported between the midsole thicknesses for both DPSI and VSI (p<0.01). No statistical differences were noted for the indices SPSI or MLSI. The present data agree with the running studies in that increased midsole thickness has a negative influence on landing stability.

  5. STABILITY AND DYNAMICS OF SPATIO-TEMPORAL STRUCTURES

    Energy Technology Data Exchange (ETDEWEB)

    Hermann Riecke

    2005-10-21

    This document constitutes the final report for the grant. It provides a complete list of publications and presentations that arose from the project as well as a brief description of the highlights of the research results. The research funded by this grant has provided insights into the spontaneous formation of structures of increasing complexity in systems driven far from thermodynamic equilibrium. A classic example of such a system is thermally driven convection in a horizontal fluid layer. Highlights of the research are: (1) explanation of the localized traveling wave pulses observed in binary-mixture convection, (2) explanation of the localized waves in electroconvection, (3) introduction of a new diagnostics for spatially and temporally chaotic states, which is based on the statistics of defect trajectories, (4) prediction of complex states in thermally driven convection in rotating systems. Additional contributions provided insight into the localization mechanism for oscillons, the prediction of a new localization mechanism for traveling waves based on a resonant periodic forcing, and an analysis of the stability of quasi-periodic patterns.

  6. Stability of viscoelastic dynamic contact lines: An experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Spaid, M.A.; Homsy, G.M. [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States)

    1997-04-01

    An experimental study of the rivulet instability associated with spin coating a circular drop of fluid is conducted to examine the effect of elasticity on the onset and evolution of the instability. The spin coating experiments are conducted with viscoelastic drops consisting of a high molecular weight polystyrene in tricresyl phosphate (TCP), as well as the Newtonian solvent TCP. Results show an unequivocal delay in the onset of the instability when the appropriate Weissenberg number is sufficiently large, resulting in a larger coated area and more finger arms relative to Newtonian results. Experiments performed with the viscoelastic fluid at low Weissenberg number exhibit similar behavior to those performed with the Newtonian solvent as expected. Additionally, the growth rate of the instability is reduced for experiments in which the elastic forces are important, in agreement with the perturbation theory of Spaid and Homsy [Phys. Fluids {bold 8}, 460 (1996)], demonstrating that elastic forces have a stabilizing influence on the contact line instability. {copyright} {ital 1997 American Institute of Physics.}

  7. Stability and control of dynamic walking for a five-link planar biped robot with feet

    Institute of Scientific and Technical Information of China (English)

    Chenglong FU; Ken CHEN; Jing XIONG; Leon XU

    2007-01-01

    During dynamic walking of biped robots, the underactuated rotating degree of freedom (DOF) emerges between the support foot and the ground, which makes the biped model hybrid and dimension-variant. This paper addresses the asymptotic orbit stability for dimension-variant hybrid systems (DVHS). Based on the generalized Poincare map, the stability criterion for DVHS is also presented, and the result is then used to study dynamic walking for a five-link planar biped robot with feet. Time-invariant gait planning and nonlinear control strategy for dynamic walking with flat feet is also introduced. Simulation results indicate that an asymptotically stable limit cycle of dynamic walking is achieved by the proposed method.

  8. Dynamical stabilization of the Fermi scale. Towards a composite universe

    Energy Technology Data Exchange (ETDEWEB)

    Sannino, Francesco [Univ. of Southern Denmark, Odense (Denmark). CP3-Origins, Center for Particle Physics

    2013-02-01

    This lecture-based, concise primer introduces and summarize basic features associated with dynamical breaking of the electroweak symmetry in elementary particle physics. In particular, the phase diagram of strongly-coupled theories as function of the number of colors, flavors and matter representation, playing a fundamental role when trying to construct viable extensions of the standard model, are examined for SU(N) gauge theories with fermionic matter transforming according to arbitrary representations of the underlying gauge group. We further discuss how the phase diagram can be used to construct unparticle models and then review Minimal Walking Technicolor (MWT) and other extensions, such as partially gauged and split technicolor. Eventually, the unification of the standard model gauge couplings are revisited within technicolor extensions of the standard model. A number of appendices helps student and newcomers to the field reviewing some basic methods and provide them with useful details.

  9. On the Dynamical Stability of the Solar System

    CERN Document Server

    Batygin, Konstantin

    2008-01-01

    A long-term numerical integration of the classical Newtonian approximation to the planetary orbital motions of the full Solar System (sun + 8 planets), spanning 20 Gyr, was performed. The results showed no severe instability arising over this time interval. Subsequently, utilizing a bifurcation method described by Jacques Laskar, two numerical experiments were performed with the goal of determining dynamically allowed evolutions for the Solar System in which the planetary orbits become unstable. The experiments yielded one evolution in which Mercury falls onto the Sun at ~1.261Gyr from now, and another in which Mercury and Venus collide in ~862Myr. In the latter solution, as a result of Mercury's unstable behavior, Mars was ejected from the Solar System at ~822Myr. We have performed a number of numerical tests that confirm these results, and indicate that they are not numerical artifacts. Using synthetic secular perturbation theory, we find that Mercury is destabilized via an entrance into a linear secular re...

  10. Dynamics and stability of directional jumps in the desert locust

    Science.gov (United States)

    Gvirsman, Omer

    2016-01-01

    Locusts are known for their ability to jump large distances to avoid predation. The jump also serves to launch the adult locust into the air in order to initiate flight. Various aspects of this important behavior have been studied extensively, from muscle physiology and biomechanics, to the energy storage systems involved in powering the jump, and more. Less well understood are the mechanisms participating in control of the jump trajectory. Here we utilise video monitoring and careful analysis of experimental directional jumps by adult desert locusts, together with dynamic computer simulation, in order to understand how the locusts control the direction and elevation of the jump, the residual angular velocities resulting from the jump and the timing of flapping-flight initiation. Our study confirms and expands early findings regarding the instrumental role of the initial body position and orientation. Both real-jump video analysis and simulations based on our expanded dynamical model demonstrate that the initial body coordinates of position (relative to the hind-legs ground-contact points) are dominant in predicting the jumps’ azimuth and elevation angles. We also report a strong linear correlation between the jumps’ pitch-angular-velocity and flight initiation timing, such that head downwards rotations lead to earlier wing opening. In addition to offering important insights into the bio-mechanical principles of locust jumping and flight initiation, the findings from this study will be used in designing future prototypes of a bio-inspired miniature jumping robot that will be employed in animal behaviour studies and environmental monitoring applications. PMID:27703846

  11. Dynamics and stability of directional jumps in the desert locust

    Directory of Open Access Journals (Sweden)

    Omer Gvirsman

    2016-09-01

    Full Text Available Locusts are known for their ability to jump large distances to avoid predation. The jump also serves to launch the adult locust into the air in order to initiate flight. Various aspects of this important behavior have been studied extensively, from muscle physiology and biomechanics, to the energy storage systems involved in powering the jump, and more. Less well understood are the mechanisms participating in control of the jump trajectory. Here we utilise video monitoring and careful analysis of experimental directional jumps by adult desert locusts, together with dynamic computer simulation, in order to understand how the locusts control the direction and elevation of the jump, the residual angular velocities resulting from the jump and the timing of flapping-flight initiation. Our study confirms and expands early findings regarding the instrumental role of the initial body position and orientation. Both real-jump video analysis and simulations based on our expanded dynamical model demonstrate that the initial body coordinates of position (relative to the hind-legs ground-contact points are dominant in predicting the jumps’ azimuth and elevation angles. We also report a strong linear correlation between the jumps’ pitch-angular-velocity and flight initiation timing, such that head downwards rotations lead to earlier wing opening. In addition to offering important insights into the bio-mechanical principles of locust jumping and flight initiation, the findings from this study will be used in designing future prototypes of a bio-inspired miniature jumping robot that will be employed in animal behaviour studies and environmental monitoring applications.

  12. Simultaneously enhanced device efficiency, stabilized chromaticity of organic light emitting diodes with lambertian emission characteristic by random convex lenses

    Science.gov (United States)

    Lee, Keunsoo; Lee, Jonghee; Kim, Eunhye; Lee, Jeong-Ik; Cho, Doo-Hee; Lim, Jong Tae; Joo, Chul Woong; Kim, Joo Yeon; Yoo, Seunghyup; Ju, Byeong-Kwon; Moon, Jaehyun

    2016-02-01

    An optical functional film applicable to various lighting devices is demonstrated in this study. The phase separation of two immiscible polymers in a common solvent was used to fabricate the film. In this paper, a self-organized lens-like structure is realized in this manner with optical OLED functional film. For an OLED, there are a few optical drawbacks, including light confinement or viewing angle distortion. By applying the optical film to an OLED, the angular spectra distortion resulting from the designed organic stack which produced the highest efficiency was successfully stabilized, simultaneously enhancing the efficiency of the OLED. We prove the effect of the film on the efficiency of OLEDs through an optical simulation. With the capability to overcome the main drawbacks of OLEDs, we contend that the proposed film can be applied to various lighting devices.

  13. Dynamic Diamond Anvil Cell (dDAC): A novel device for studying the dynamic-pressure properties of materials

    Energy Technology Data Exchange (ETDEWEB)

    Evans, W J; Yoo, C; Lee, G W; Cynn, H; Lipp, M J; Visbeck, K

    2007-02-23

    We have developed a unique device, a dynamic diamond anvil cell (dDAC), which repetitively applies a time-dependent load/pressure profile to a sample. This capability allows studies of the kinetics of phase transitions and metastable phases at compression (strain) rates of up to 500 GPa/sec ({approx}0.16 s{sup -1} for a metal). Our approach adapts electromechanical piezoelectric actuators to a conventional diamond anvil cell design, which enables precise specification and control of a time-dependent applied load/pressure. Existing DAC instrumentation and experimental techniques are easily adapted to the dDAC to measure the properties of a sample under the varying load/pressure conditions. This capability addresses the sparsely studied regime of dynamic phenomena between static research (diamond anvil cells and large volume presses) and dynamic shock-driven experiments (gas guns, explosive and laser shock). We present an overview of a variety of experimental measurements that can be made with this device.

  14. Asymptotic stability and blow up for a semilinear damped wave equation with dynamic boundary conditions

    KAUST Repository

    Gerbi, Stéphane

    2011-12-01

    In this paper we consider a multi-dimensional wave equation with dynamic boundary conditions, related to the KelvinVoigt damping. Global existence and asymptotic stability of solutions starting in a stable set are proved. Blow up for solutions of the problem with linear dynamic boundary conditions with initial data in the unstable set is also obtained. © 2011 Elsevier Ltd. All rights reserved.

  15. Research on Dynamics and Stability in the Stairs-climbing of a Tracked Mobile Robot

    OpenAIRE

    Weijun Tao; Yi Ou; Hutian Feng

    2012-01-01

    Aiming at the functional requirement of climbing up the stairs, the dynamics and stability during a tracked mobile robot's climbing of stairs is studied. First, from the analysis of its cross-country performance, the mechanical structure of the tracked mobile robot is designed and the hardware composition of its control system is given. Second, based on the analysis to its stairs-climbing process, the dynamical model of stairs-climbing is established by using the classical mechanics method. N...

  16. Stability and Control of Large-Scale Dynamical Systems A Vector Dissipative Systems Approach

    CERN Document Server

    Haddad, Wassim M

    2011-01-01

    Modern complex large-scale dynamical systems exist in virtually every aspect of science and engineering, and are associated with a wide variety of physical, technological, environmental, and social phenomena, including aerospace, power, communications, and network systems, to name just a few. This book develops a general stability analysis and control design framework for nonlinear large-scale interconnected dynamical systems, and presents the most complete treatment on vector Lyapunov function methods, vector dissipativity theory, and decentralized control architectures. Large-scale dynami

  17. Comparison of Mandibular Advancement Splint and Tongue Stabilizing Device in Obstructive Sleep Apnea: A Randomized Controlled Trial

    Science.gov (United States)

    Deane, Sheryn A.; Cistulli, Peter A; Ng, Andrew T.; Zeng, Biao; Petocz, Peter; Darendeliler, M. Ali

    2009-01-01

    Study Objectives: To compare the efficacy of a mandibular advancement splint (MAS) and a novel tongue stabilizing device (TSD) in the treatment of obstructive sleep apnea (OSA). Design: A randomized crossover design was used. Patients: Twenty-seven patients (20 male, 7 female), recruited from a tertiary hospital sleep clinic. Measurements and Results: The apnea-hypopnea index (AHI) was reduced with MAS (11.68 ± 8.94, P = 0.000) and TSD (13.15 ± 10.77, P = 0.002) compared with baseline (26.96 ± 17.17). The arousal index decreased for MAS (21.09 ± 9.27, P = 0.004) and TSD (21.9 ± 10.56, P = 0.001) compared with baseline (33.23 ± 16.41). Sixty-eight percent of patients achieved a complete or partial response with MAS, compared with 45% with TSD. The Epworth Sleepiness Scale (ESS) score was decreased with MAS (P = <0.001) and TSD (P = 0.002). Subjective improvements in snoring and quality of sleep were reported, with a better response for MAS than TSD. Compliance was poorer for TSD, and the side effect profiles of the 2 modalities were different. All patients were satisfied with MAS compared to TSD, and 91% of patients preferred the MAS. Conclusion: Objective testing showed the MAS and TSD had similar efficacy in terms of AHI reduction. Patients reported improvements with both devices; however, better compliance and a clear preference for MAS was apparent when both devices were offered. Longer term studies are needed to clarify the role of TSD. Citation: Deane SA; Cistulli PA; Ng AT; Zeng B; Petocz P; Darendeliler MA. Comparison of mandibular advancement splint and tongue stabilizing device in obstructive sleep apnea: a randomized controlled trial. SLEEP 2009;32(5):648-653. PMID:19480232

  18. Certain Actions from the Functional Movement Screen Do Not Provide an Indication of Dynamic Stability

    Directory of Open Access Journals (Sweden)

    Lockie Robert G.

    2015-09-01

    Full Text Available Dynamic stability is an essential physical component for team sport athletes. Certain Functional Movement Screen (FMS exercises (deep squat; left- and right-leg hurdle step; left- and right-leg in-line lunge [ILL]; left- and right-leg active straight-leg raise; and trunk stability push-up [TSPU] have been suggested as providing an indication of dynamic stability. No research has investigated relationships between these screens and an established test of dynamic stability such as the modified Star Excursion Balance Test (mSEBT, which measures lower-limb reach distance in posteromedial, medial, and anteromedial directions, in team sport athletes. Forty-one male and female team sport athletes completed the screens and the mSEBT. Participants were split into high-, intermediate-, and low-performing groups according to the mean of the excursions when both the left and right legs were used for the mSEBT stance. Any between-group differences in the screens and mSEBT were determined via a one-way analysis of variance with Bonferroni post hoc adjustment (p < 0.05. Data was pooled for a correlation analysis (p < 0.05. There were no between-group differences in any of the screens, and only two positive correlations between the screens and the mSEBT (TSPU and right stance leg posteromedial excursion, r = 0.37; left-leg ILL and left stance leg posteromedial excursion, r = 0.46. The mSEBT clearly indicated participants with different dynamic stability capabilities. In contrast to the mSEBT, the selected FMS exercises investigated in this study have a limited capacity to identify dynamic stability in team sport athletes.

  19. NiTiNol Hernia Device Stability in Inguinal Hernioplasty Without Fixation

    OpenAIRE

    Brown, Roderick B.

    2011-01-01

    Background and Objective: To determine whether the NiTiNol frame of a novel hernia repair device utilizing polypropylene mesh for inguinal hernioplasty remains stable and intransient without fixation after a minimum of 6 months. Methods: Twenty patients had 27 inguinal hernias repaired using a novel hernia repair device that has a NiTiNol frame without any fixation. Initial single-view, postoperative X-rays were compared with a second X-ray obtained at least 6 months later. The NiTiNol frame,...

  20. Effect of intermolecular force on the static/dynamic behaviour of M/NEM devices.

    Science.gov (United States)

    Kim, Namjung; Aluru, N R

    2014-12-01

    Advances made in the fabrication of micro/nano-electromechanical (M/NEM) devices over the last ten years necessitate the understanding of the attractive force that arises from quantum fluctuations (generally referred to as Casimir effects) [Casimir H B G 1948 Proc. K. Ned. Akad. Wet. 51 793]. The fundamental mechanisms underlying quantum fluctuations have been actively investigated through various theoretical and experimental approaches. However, the effect of the force on M/NEM devices has not been fully understood yet, especially in the transition region involving gaps ranging from 10 nm to 1 μm, due to the complexity of the force. Here, we numerically calculate the Casimir effects in M/NEM devices by using the Lifshitz formula, the general expression for the Casimir effects [Lifshitz E 1956 Sov. Phys. JETP 2 73]. Since the Casimir effects are highly dependent on the permittivity of the materials, the Kramer-Kronig relation [Landau L D, Lifshitz E M and Pitaevskii L P 1984 Electrodynamics of Continuous Media (New York: Pergamon Press)] and the optical data for metals and dielectrics are used in order to obtain the permittivity. Several simplified models for the permittivity of the materials, such as the Drude and Lorentz models [Jackson J D 1975 Classical Electrodynamics (New York: Wiley)], are also used to extrapolate the optical data. Important characteristic values of M/NEM devices, such as the pull-in voltage, pull-in gap, detachment length, etc, are calculated for devices operating in the transition region. Our results show that accurate predictions for the pull-in behaviour are possible when the Lifshitz formula is used instead of the idealized expressions for Casimir effects. We expand this study into the dynamics of M/NEM devices, so that the time and frequency response of M/NEM devices with Casimir effects can be explored.

  1. Evaluation of a New Technique for iFOBT Utilising a New Sample Collection Device with Increased Buffer Stability.

    Science.gov (United States)

    Bruns-Toepler, Markus; Hardt, Philip

    2017-07-01

    The aims of the present study were: (i) Evaluate specificity and sensitivity of Hb Smart enzyme-linked immunosorbent assay (ELISA) (ScheBo Biotech) compared to colonoscopy results and (ii) assess stability of a new sample collection device containing a newly formulated buffer to extract haemoglobin using buffer and stool samples spiked with defined concentrations of haemoglobin. Stool samples were quantified with the ELISA method. The stability of haemoglobin in the extraction buffer and in native stool samples, respectively, was determined daily by ELISA during storage for 5 days at 4°C and at room temperature after addition of haemoglobin. Haemoglobin ELISA had a sensitivity of 78.4% for detection of CRC with a specificity of 98%. Haemoglobin extracted in corresponding extraction buffer demonstrated stability throughout storage for 5 days at 4°C and at room temperature. Hb Smart represents a very promising tool for large-scale screening of CRC with regard to sample handling, stability and analysis of haemoglobin in faeces. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

  2. A direct comparison of local dynamic stability during unperturbed standing and walking.

    Science.gov (United States)

    Kang, Hyun Gu; Dingwell, Jonathan B

    2006-06-01

    Standing and walking are very different tasks. It might be reasonable, therefore, to assume that the mechanisms used to maintain the stability of standing and walking should be quite different. However, many studies have shown that postural stability measures can generally predict risk of falls, even though most falls occur during locomotor tasks and not during postural tasks. This suggests that there is at least some commonality among the mechanisms governing the control of both standing and walking. The present study was conducted to determine whether the postural stability either is or is not directly related to locomotor stability. Twenty healthy adults, age 18-73 years, walked on a motorized treadmill at their preferred walking speed for three trials of 5 min. They also stood on a force plate for three trials of 5 min. Both tasks were performed without imposing any additional external perturbations. The motion of each subject's trunk segment was recorded and described using a multi-dimensional state space defined in the same manner for both tasks. Local dynamic stability was quantified from the mean divergence over time of locally perturbed trajectories in state space, which was parameterized as a double exponential process. Divergence parameters were compared to determine the relationship between local dynamic stability during standing and walking. Standing and walking exhibited local dynamic stability properties that were significantly different (P0.1). Divergence parameters were also compared to traditional center of pressure (COP) measures obtained from standing trials. COP measures were significantly correlated to local divergence parameters for standing, but not to those for walking. This study provides direct evidence that the mechanisms governing standing and walking stability are significantly different.

  3. Stabilization of Regional Column Models by Parameterized Dynamical Tendencies

    Science.gov (United States)

    Bergman, J. W.

    2002-12-01

    Atmospheric Single Column Models (SCMs) provide an efficient modeling framework for regional studies. In these models, vertical profiles of temperature and humidity evolve in response to diabatic interactions within the column and adiabatic tendencies produced by by the large scale circulation. The adiabatic tendencies are either prescribed or neglected and,thus, decoupled from the diabatic tendencies. This decoupling can lead to the rapid development of unrealistic atmospheric states. In particular, the temperature profiles from a SCM can become unrealistic enough within just a few hours to render any meaningful diagnosis difficult, if not impossible. We have implemented an SCM framework in which the adiabatic tendencies are coupled to the column physics through a formula that links vertical temperature advection to the time-history of diabatic heating rates. The parameters in any such coupling formula should depend in principle depend upon the zonal, meridional, vertical and temporal scales of the heating. In practice, however, we find that the dependence is weak over a wide range of zonal and meridional scales; the vertical dependence is accounted for in the formula itself, as is also the temporal dependence by considering the time history of the diabatic forcing rather than just instantaneous values. The effect of this dynamical coupling on the behavior of an SCM extracted from the NCAR CCM is investigated here. Because of the coupling, only the mean temperature and humidity profiles for the environment in which the column is embedded need to be explicitly specified; all other quantities are generated by the model. The coupled SCM is tested in tropical conditions during the TOGA COARE period. Control runs and 100-member ensembles, in which initial temperature and humidity profiles are perturbed, are run for environmental conditions taken from 85 sets of observed temperature and humidity profiles. The same data are also used to force the original, dynamically

  4. Convergence and Heterogeneity in Euro Based Economies: Stability and Dynamics

    Directory of Open Access Journals (Sweden)

    Philip Haynes

    2016-08-01

    Full Text Available Cluster analysis is used to explore the performance of key macroeconomic variables in European countries that share the euro, from the inception of the currency in 2002 through to 2013. An original applied statistical approach searches for a pattern synthesis across a matrix of macroeconomic data to examine if there is evidence for country clusters and whether there is convergence of the cluster patterns over time. A number of different clusters appear and these change over time as the economies of the member states dynamically interact. This includes some new countries joining the currency during the period of examination. As found in previous research, Southern European countries tend to remain separate from other countries. The new methods used, however, add to an understanding of some differences between Southern European countries, in addition to replicating their broad similarities. Hypotheses are formed about the country clusters existing in 2002, 2006 and 2013, at key points in time of the euro integration process. These hypotheses are tested using the rigour of a bivariate analysis and the multivariate method of Qualitative Comparative Analysis (QCA. The results confirm the hypotheses of cluster memberships in all three periods. The confirmation analysis provides evidence about which variables are most influencing cluster memberships at each time point. In 2002 and 2006, differences between countries are influenced by their different Harmonised Index of Consumer Prices (HICP and labour productivity scores. In 2013, after the crisis, there is a noticeable change. Long term interest rates and gross government debt become key determinants of differences, in addition to the continuing influence of labour productivity. The paper concludes that in the last decade the convergence of countries sharing the euro has been limited, by the joining of new countries and the circumstances of the global economic crisis. The financial crisis has driven

  5. Electronic device having electrode with high area density and improved mechanical stability

    NARCIS (Netherlands)

    Guiraud, L.; Lecornec, F.; Klootwijk, J.H.; Roozeboom, F.; Chevrie, D.D.R.

    2012-01-01

    The invention relates to an electric device including an electric element, the electric element comprising a first electrode (104) having a first surface (106) and a pillar (108), the pillar extending from the first surface in a first direction (110), the pillar having a length measured from the fir

  6. Dynamical Behavior and Stability Analysis in a Hybrid Epidemiological-Economic Model with Incubation

    Directory of Open Access Journals (Sweden)

    Chao Liu

    2014-01-01

    Full Text Available A hybrid SIR vector disease model with incubation is established, where susceptible host population satisfies the logistic equation and the recovered host individuals are commercially harvested. It is utilized to discuss the transmission mechanism of infectious disease and dynamical effect of commercial harvest on population dynamics. Positivity and permanence of solutions are analytically investigated. By choosing economic interest of commercial harvesting as a parameter, dynamical behavior and local stability of model system without time delay are studied. It reveals that there is a phenomenon of singularity induced bifurcation as well as local stability switch around interior equilibrium when economic interest increases through zero. State feedback controllers are designed to stabilize model system around the desired interior equilibria in the case of zero economic interest and positive economic interest, respectively. By analyzing corresponding characteristic equation of model system with time delay, local stability analysis around interior equilibrium is discussed due to variation of time delay. Hopf bifurcation occurs at the critical value of time delay and corresponding limit cycle is also observed. Furthermore, directions of Hopf bifurcation and stability of the bifurcating periodic solutions are studied. Numerical simulations are carried out to show consistency with theoretical analysis.

  7. Stability and lattice dynamics of SiO2 cristobalite

    Science.gov (United States)

    Coh, Sinisa; Vanderbilt, David

    2008-03-01

    Among the phases of SiO2 are alpha and beta cristobalite. Despite early indications that the higher-temperature beta phase might be cubic (Fd3m), it is now accepted that it is in fact tetragonal (I42d), and that the experiments suggesting a cubic structure were averaging spatially or dynamically over tetragonal domains. Recently, Zhang and Scott (J. Phys. Cond.Matt. 19, 275201) suggested that the lower-temperature alpha phase, widely accepted to be tetragonal (P41212), might be an artifact in a similar way. With this motivation we investigate the energy landscape in the vicinity of cristobalite phases using first-principles calculations. We use the ABINIT implementation of density-functional theory in a plane-wave pseudopotential framework. We find that both the P41212 alpha and I42d beta phases are local minima, thus reinforcing that the identification of the alpha phase as belonging to the P41212 structure. We compute the frequencies of phonon modes at high-symmetry k-points in both structures and compare with experiment. We also identify a minimum-energy path connecting the alpha and beta phases through an intermediate orthorhombic phase (P212121), and find a surprisingly low barrier of ˜5,eV per formula unit. We note that a simple rigid-unit mode picture gives a good rough description of these energetics, and we map out the minimum-energy path in the space of rigid unit rotations in a physically insightful way.

  8. Static and Dynamic Mechanical Analyses for the Vacuum Vessel of EAST Superconducting Tokamak Device

    Science.gov (United States)

    Song, Yuntao; Yao, Damao; Du, Shijun; Wu, Songtao; Weng, Peide

    2006-03-01

    EAST (experimental advanced superconducting tokamak) is an advanced steady-state plasma physics experimental device, which is being constructed as the Chinese National Nuclear Fusion Research Project. During the plasma operation the vacuum vessel as one of the key component will withstand the electromagnetic force due to the plasma disruption, the Halo current and the toroidal field coil quench, the pressure of boride water and the thermal load due to 250 oC baking by pressurized nitrogen gas. In this paper a report of the static and dynamic mechanical analyses of the vacuum vessel is made. Firstly the applied loads on the vacuum vessel were given and the static stress distribution under the gravitational loads, the pressure loads, the electromagnetic loads and thermal loads were investigated. Then a series of primary dynamic, buckling and fatigue life analyses were performed to predict the structure's dynamic behavior. A seismic analysis was also conducted.

  9. Light stability of ITO-free semi-transparent and opaque organic photovoltaic devices

    NARCIS (Netherlands)

    Voroshazi, E.; Yaala, M.B.; Uytterhoeven, G.; Tait, J.G.; Andriessen, R.H.A.J.M.; Galagan, Y.; Cheyns, D.

    2015-01-01

    Intrinsic light stability of transparent MoO3/Ag/TiO2 electrode is studied in four different polymer:fullerene solar cell configurations. We demonstrate that this stack can successfully replace ITO both in superstrate and substrate configurations required for non-transparent carriers. Although we

  10. Light stability of ITO-free semi-transparent and opaque organic photovoltaic devices

    NARCIS (Netherlands)

    Voroshazi, E.; Yaala, M.B.; Uytterhoeven, G.; Tait, J.G.; Andriessen, R.H.A.J.M.; Galagan, Y.; Cheyns, D.

    2015-01-01

    Intrinsic light stability of transparent MoO3/Ag/TiO2 electrode is studied in four different polymer:fullerene solar cell configurations. We demonstrate that this stack can successfully replace ITO both in superstrate and substrate configurations required for non-transparent carriers. Although we ob

  11. Dynamic stability during level walking and obstacle crossing in persons with facioscapulohumeral muscular dystrophy

    NARCIS (Netherlands)

    Rijken, N.H.M.; Engelen, B.G.M. van; Geurts, A.C.H.; Weerdesteyn, V.G.

    2015-01-01

    Patients with FSHD suffer from progressive skeletal muscle weakness, which is associated with an elevated fall risk. To obtain insight into fall mechanisms in this patient group, we aimed to assess dynamic stability during level walking and obstacle crossing in patients at different disease stages.

  12. On the stability of nonautonomous binary dynamical systems of partial differential equations

    Directory of Open Access Journals (Sweden)

    Salvatore Rionero

    2013-01-01

    Full Text Available Nonlinear nonautonomoua binary reaction-diffusion dynamical systems of partial differential equations (PDE are considered. Stability criteria - via a nonautonomous L²-energy - are obtained. Applications to nonautonomous Lotka-volterra systems of PDEs and to “preys” struggle for the life, are furnished.

  13. Dynamic postural stability differences between male and female players with and without ankle sprain

    NARCIS (Netherlands)

    Dallinga, Joan M.; Does, van der Henrike T. D.; Benjaminse, Anne; Lemmink, Koen A. P. M.

    2016-01-01

    Objectives: To evaluate dynamic stability index (DSI) differences between males and females for different jump directions. To examine both preseason DSI differences between players with and without a history of ankle sprain, and between players with and without an ankle sprain during the subsequent

  14. Effect of active arm swing to local dynamic stability during walking.

    Science.gov (United States)

    Wu, Yu; Li, Yue; Liu, An-Min; Xiao, Fei; Wang, Yin-Zhi; Hu, Fei; Chen, Jin-Ling; Dai, Ke-Rong; Gu, Dong-Yun

    2016-02-01

    Arm swing is an essential component in regulating dynamic stability of the whole body during walking, while the contribution of active arm swing to local dynamic stability of different motion segments remains unclear. This study investigated the effects of arm swing under natural arm swing condition and active arm swing condition on local dynamic stability and gait variability of the trunk segments (C7 and T10 joint) and lower extremity joints (hip, knee and ankle joint). The local divergence exponents (λs) and mean standard deviation over strides (MeanSD) of 24 young healthy adults were calculated while they were walking on treadmill with two arm swing conditions at their preferred walking speed (PWS). We found that in medial-lateral direction, both λs and MeanSD values of the trunk segments (C7 and T10 joint) in active arm swing condition were significantly lower than those in natural arm swing condition (pknee and ankle joint) was found between two arm swing conditions (p>0.05, respectively). In anterior-posterior and vertical direction, neither λs nor MeanSD values of all body segments showed significant difference between two arm swing conditions (p>0.05, respectively). These findings indicate that active arm swing may help to improve the local dynamic stability of the trunk segments in medial-lateral direction.

  15. Total Stability Properties Based on Fixed Point Theory for a Class of Hybrid Dynamic Systems

    Directory of Open Access Journals (Sweden)

    M. De la Sen

    2009-01-01

    Full Text Available Robust stability results for nominally linear hybrid systems are obtained from total stability theorems for purely continuous-time and discrete-time systems by using the powerful tool of fixed point theory. The class of hybrid systems dealt consists, in general, of coupled continuous-time and digital systems subject to state perturbations whose nominal (i.e., unperturbed parts are linear and, in general, time-varying. The obtained sufficient conditions on robust stability under a wide class of harmless perturbations are dependent on the values of the parameters defining the over-bounding functions of those perturbations. The weakness of the coupling dynamics in terms of norm among the analog and digital substates of the whole dynamic system guarantees the total stability provided that the corresponding uncoupled nominal subsystems are both exponentially stable. Fixed point stability theory is used for the proofs of stability. A generalization of that result is given for the case that sampling is not uniform. The boundedness of the state-trajectory solution at sampling instants guarantees the global boundedness of the solutions for all time. The existence of a fixed point for the sampled state-trajectory solution at sampling instants guarantees the existence of a fixed point of an extended auxiliary discrete system and the existence of a global asymptotic attractor of the solutions which is either a fixed point or a limit n globally stable asymptotic oscillation.

  16. Finite element analysis of dynamic stability of skeletal structures under periodic loading

    Institute of Scientific and Technical Information of China (English)

    THANA Hemantha Kumar; AMEEN Mohammed

    2007-01-01

    This paper addresses the dynamic stability problem of columns and frames subjected to axially applied periodic loads. Such a structure can become unstable under certain combinations of amplitudes and frequencies of the imposed load acting on its columns/beams. These are usually shown in the form of plots which describe regions of instability. The finite element method (FEM) is used in this work to analyse dynamic stability problems of columns. Two-noded beam elements are used for this purpose.The periodic loading is decomposed into various harmonics using Fourier series expansion. Computer codes in C++ using object oriented concepts are developed to determine the stability regions of columns subjected to periodic loading. A number of numerical examples are presented to illustrate the working of the program. The direct integration of the equations of motions of the discretised system is carried out using Newmark's method to verify the results.

  17. A Non-equilibrium Thermodynamic Framework for the Dynamics and Stability of Ecosystems

    CERN Document Server

    Michaelian, K

    2002-01-01

    The population dynamics and stability of ecosystems of interacting species is studied from the perspective of non-equilibrium thermodynamics by assuming that species, through their biotic and abiotic interactions, are units of entropy production and exchange in an open thermodynamic system with constant external constraints. Within the context of the linear theory of irreversible thermodynamics, such a system will naturally evolve towards a stable stationary state in which the production of entropy within the ecosystem is at a local minimum value. It is shown that this extremal condition leads to equations for the stationary (steady) state population dynamics of interacting species, more general than those of Lotka-Volterra, and to conditions on the parameters of the community interaction matrix guaranteeing ecosystem stability. The paradoxical stability of real complex ecosystems thus has a simple explanation within the proposed framework. Furthermore, it is shown that the second law of thermodynamics constr...

  18. Dynamic Phasors-Based Modeling and Stability Analysis of Droop-Controlled Inverters for Microgrid Applications

    DEFF Research Database (Denmark)

    Guo, Xiaoqiang; Lu, Zhigang; Wang, Baocheng

    2014-01-01

    System modeling and stability analysis is one of the most important issues of inverter-dominated microgrids. It is useful to determine the system stability and optimize the control parameters. The complete small signal models for the inverter-dominated microgrids have been developed which are very...... accurate and could be found in literature. However, the modeling procedure will become very complex when the number of inverters in microgrid is large. One possible solution is to use the reduced-order small signal models for the inverter-dominated microgrids. Unfortunately, the reduced-order small signal...... models fail to predict the system instabilities. In order to solve the problem, a new modeling approach for inverter-dominated microgrids by using dynamic phasors is presented in this paper. Our findings indicate that the proposed dynamic phasor model is able to predict accurately the stability margins...

  19. A passive-flow microfluidic device for imaging latent HIV activation dynamics in single T cells.

    Science.gov (United States)

    Ramji, Ramesh; Wong, Victor C; Chavali, Arvind K; Gearhart, Larisa M; Miller-Jensen, Kathryn

    2015-09-01

    Quantifying cell-to-cell variability in drug response dynamics is important when evaluating therapeutic efficacy. For example, optimizing latency reversing agents (LRAs) for use in a clinical "activate-and-kill" strategy to purge the latent HIV reservoir in patients requires minimizing heterogeneous viral activation dynamics. To evaluate how heterogeneity in latent HIV activation varies across a range of LRAs, we tracked drug-induced response dynamics in single cells via live-cell imaging using a latent HIV-GFP reporter virus in a clonal Jurkat T cell line. To enable these studies in suspension cells, we designed a simple method to capture an array of single Jurkat T cells using a passive-flow microfluidic device. Our device, which does not require external pumps or tubing, can trap hundreds of cells within minutes with a high retention rate over 12 hours of imaging. Using this device, we quantified heterogeneity in viral activation stimulated by transcription factor (TF) activators and histone deacetylase (HDAC) inhibitors. Generally, TF activators resulted in both faster onset of viral activation and faster rates of production, while HDAC inhibitors resulted in more uniform onset times, but more heterogeneous rates of production. Finally, we demonstrated that while onset time of viral gene expression and rate of viral production together predict total HIV activation, rate and onset time were not correlated within the same individual cell, suggesting that these features are regulated independently. Overall, our results reveal drug-specific patterns of noisy HIV activation dynamics not previously identified in static single-cell assays, which may require consideration for the most effective activate-and-kill regime.

  20. Dynamic stabilization of cubic CaSiO3 perovskite at high temperatures and pressures from ab initio molecular dynamics

    Science.gov (United States)

    Sun, Tao; Zhang, Dong-Bo; Wentzcovitch, Renata M.

    2014-03-01

    The stability of cubic CaSiO3 perovskite (CaPv) at high temperatures and pressures is investigated by vibrational normal-mode analysis. We compute power spectra of mode autocorrelation functions using a recently developed hybrid approach combining ab initio molecular dynamics with lattice dynamics. These power spectra, together with the probability distributions of atomic displacements, indicate that cubic CaPv is stabilized at T ˜600 K and P ˜ 26 GPa. We then utilize the concept of phonon quasiparticles to characterize the vibrational properties of cubic CaPv at high temperature and obtain anharmonic phonon dispersions through the whole Brillouin zone. Such temperature-dependent phonon dispersions pave the way for more accurate calculations of free-energy, thermodynamic, and thermoelastic properties of cubic CaPv at Earth's lower mantle conditions.

  1. Dynamic Stability of Passive Bipedal Walking on Rough Terrain:A Preliminary Simulation Study

    Institute of Scientific and Technical Information of China (English)

    Parsa Nassiri Afshar; Lei Ren

    2012-01-01

    A simplified 2D passive dynamic model was simulated to walk down on a rough slope surface defined by deterministic profiles to investigate how the walking stability changes with increasing surface roughness.Our results show that the passive walker can walk on rough surfaces subject to surface roughness up to approximately 0.1% of its leg length.This indicates that bipedal walkers based on passive dynamics may possess some intrinsic stability to adapt to rough terrains although the maximum roughness they can tolerate is small.Orbital stability method was used to quantify the walking stability before the walker started to fall over.It was found that the average maximum Floquet multiplier increases with surface roughness in a non-linear form.Although the passive walker remained orbitally stable for all the simulation cases,the results suggest that the possibility of the bipedal model moving away from its limit cycle increases with the surface roughness if subjected to additional perturbations.The number of consecutive steps before falling was used to measure the walking stability after the passive walker started to fall over.The results show that the number of steps before falling decreases exponentially with the increase in surface roughness.When the roughness magnitude approached to 0.73% of the walker's leg length,it fell down to the ground as soon as it entered into the uneven terrain.It was also found that shifting the phase angle of the surface profile has apparent affect on the system stability.This is probably because point contact was used to simulate the heel strikes and the resulted variations in system states at heel strikes may have pronounced impact on the passive gaits,which have narrow basins of attraction.These results would provide insight into how the dynamic stability of passive bipedal walkers evolves with increasing surface roughness.

  2. Dynamical investigation and parameter stability region analysis of a flywheel energy storage system in charging mode

    Science.gov (United States)

    Zhang, Wei-Ya; Li, Yong-Li; Chang, Xiao-Yong; Wang, Nan

    2013-09-01

    In this paper, the dynamic behavior analysis of the electromechanical coupling characteristics of a flywheel energy storage system (FESS) with a permanent magnet (PM) brushless direct-current (DC) motor (BLDCM) is studied. The Hopf bifurcation theory and nonlinear methods are used to investigate the generation process and mechanism of the coupled dynamic behavior for the average current controlled FESS in the charging mode. First, the universal nonlinear dynamic model of the FESS based on the BLDCM is derived. Then, for a 0.01 kWh/1.6 kW FESS platform in the Key Laboratory of the Smart Grid at Tianjin University, the phase trajectory of the FESS from a stable state towards chaos is presented using numerical and stroboscopic methods, and all dynamic behaviors of the system in this process are captured. The characteristics of the low-frequency oscillation and the mechanism of the Hopf bifurcation are investigated based on the Routh stability criterion and nonlinear dynamic theory. It is shown that the Hopf bifurcation is directly due to the loss of control over the inductor current, which is caused by the system control parameters exceeding certain ranges. This coupling nonlinear process of the FESS affects the stability of the motor running and the efficiency of energy transfer. In this paper, we investigate into the effects of control parameter change on the stability and the stability regions of these parameters based on the averaged-model approach. Furthermore, the effect of the quantization error in the digital control system is considered to modify the stability regions of the control parameters. Finally, these theoretical results are verified through platform experiments.

  3. The stabilizing effects of genetic diversity on predator-prey dynamics.

    Science.gov (United States)

    Steiner, Christopher F; Masse, Jordan

    2013-01-01

    Heterogeneity among prey in their susceptibility to predation is a potentially important stabilizer of predator-prey interactions, reducing the magnitude of population oscillations and enhancing total prey population abundance. When microevolutionary responses of prey populations occur at time scales comparable to population dynamics, adaptive responses in prey defense can, in theory, stabilize predator-prey dynamics and reduce top-down effects on prey abundance. While experiments have tested these predictions, less explored are the consequences of the evolution of prey phenotypes that can persist in both vulnerable and invulnerable classes. We tested this experimentally using a laboratory aquatic system composed of the rotifer Brachionus calyciflorus as a predator and the prey Synura petersenii, a colony-forming alga that exhibits genetic variation in its propensity to form colonies and colony size (larger colonies are a defense against predators). Prey populations of either low initial genetic diversity and low adaptive capacity or high initial genetic diversity and high adaptive capacity were crossed with predator presence and absence. Dynamics measured over the last 127 days of the 167-day experiment revealed no effects of initial prey genetic diversity on the average abundance or temporal variability of predator populations. However, genetic diversity and predator presence/absence interactively affected prey population abundance and stability; diversity of prey had no effects in the absence of predators but stabilized dynamics and increased total prey abundance in the presence of predators. The size structure of the genetically diverse prey populations diverged from single strain populations in the presence of predators, showing increases in colony size and in the relative abundance of cells found in colonies. Our work sheds light on the adaptive value of colony formation and supports the general view that genetic diversity and intraspecific trait variation of

  4. The relationship between trunk rotation, upper quarter dynamic stability and pitch velocity.

    Science.gov (United States)

    Bullock, Garrett S; Schmitt, Abigail C; Chasse, Patrick; Little, Barrett A; Diehl, Lee H; Butler, Robert J

    2017-02-21

    Understanding the relationship between upper quarter mobility, dynamic stability and pitching velocity may be beneficial in elucidating underlying factors that affect pitching performance. The purpose of this study was to investigate upper trunk rotation mobility and upper quarter dynamic stability and their correlation to pitch velocity in NCAA Division I collegiate pitchers. We hypothesized that collegiate pitchers with greater upper trunk rotation mobility and upper extremity dynamic stability would exhibit higher pitching velocity. Trunk rotation and the Upper Quarter Y-Balance Test (YBT-UQ) were measured utilizing standardized protocols. Collegiate pitchers (n=30) then proceeded to complete their team prescribed dynamic and throwing warm up followed by a pitching session from regulation distance at 100% effort. Each pitch was recorded for velocity and pitch type, only fastballs were utilized in analysis. The relationships between trunk rotation and fastball velocity, and YBT-UQ scores and fastball velocity were assessed using a series of two-tail Pearsons Correlations (p<.05). Throwing and non-throwing sides (69.6± 9.5 deg., 70.7± 9.4 deg.) had similar trunk rotation mobility. No statistically significant correlation between upper trunk rotation mobility and pitch velocity was found (throwing arm: r=.131, p<.491; non-throwing arm: r=.135, p<.478). There was also no correlation between the YBT-UQ and fastball velocity. In this study of Division I baseball pitchers, we found no relationship between trunk rotational mobility, upper quarter dynamic stability and pitching velocity. This suggests that increased upper extremity stability and trunk mobility are not directly related to fastball velocity. Understanding factors that associate to velocity may be helpful in predicting pitching performance.

  5. Dynamic Modeling & Stability Analysis of a Generic UAV in Glide Phase

    Directory of Open Access Journals (Sweden)

    Mir Imran

    2017-01-01

    Full Text Available In this paper, we present dynamic modelling and stability analysis of a generic UAV in the glide phase under engine failure condition. When such extreme phenomena occurs, the most desirable requirement is to survive that stage by keeping the vehicle controllable by maintaining its orientation and to glide the vehicle towards the intended direction with maximum extended range. This study investigates the stability aspects of one such aerial vehicle under engine failure condition. In the proposed architecture, a six degree of freedom vehicle dynamic simulation model is implemented through a set of coupled non-linear differential equations. The aerodynamic forces and moments encountered by the UAV during various phases of the flight are ascertained through empirical / non-empirical techniques. Non-linear constrained optimization technique is employed to evaluate the steady state values of the optimized trajectory for the complete flight regime. Results from dynamical systems theory are applied to investigate local stability characteristics of UAV around the steady state. Complete set of dynamic modes of UAV throughout the glide phase are evaluated and mode content in each of the motion variable is determined using modal decomposition technique. The dynamic characteristics of the open-loop configuration are assessed to generate adequate benchmark performance for closed-loop controller design

  6. Dynamic and Static Combination Analysis Method of Slope Stability Analysis during Earthquake

    Directory of Open Access Journals (Sweden)

    Liang Lu

    2014-01-01

    Full Text Available The results of laboratory model tests for simulating the slope failure due to vibration, including unreinforced slope and the slope reinforced by using geotextile, show that the slope failure occurs when a cumulative plastic displacement exceeds a certain critical value. To overcome the defects of conventional stability analysis, which evaluates the slope characteristics only by its strength parameters, a numerical procedure considering the stiffness and deformation of materials and geosynthetics is proposed to evaluate the seismic slope stability. In the proposed procedure, the failure of slope is defined when the cumulative plastic displacement calculated by a dynamic response analysis using actual seismic wave exceeds the critical value of displacement estimated by a static stability analysis considering seismic coefficient. The proposed procedure is applied to the laboratory model tests and an actual failure of slope in earthquake. The case study shows the possibility that the proposed procedure gives the realistic evaluation of seismic slope stability.

  7. Testing of the stability of intensity modulated beams generated with dynamic multileaf collimation, applied to the MM50 racetrack microtron.

    Science.gov (United States)

    Dirkx, M L; Heijmen, B J

    2000-12-01

    Recently, we have published a method for the calculation of required leaf trajectories to generate optimized intensity modulated x-ray beams by means of dynamic multileaf collimation [Phys. Med. Biol. 43, 1171-1184 (1998)]. For the MM50 Racetrack Microtron it has been demonstrated that the dosimetric accuracy of this method, in combination with the dose calculation algorithm of the Cadplan 3D treatment planning system, is adequate for a clinical application (within 2% or 0.2 cm). Prior to initiating patient treatment with dynamic multileaf collimation (DMLC), tests have been performed to investigate the stability of DMLC fields generated at the MM50, (i) in time, (ii) subject to gantry rotation and (iii) in case of treatment interrupts, e.g., caused by an error detected by the treatment machine. The stability of relative dose profiles, normalized to a reference point in a relatively flat part of the modulated beam profile, was assessed from measurements with an electronic portal imaging device (EPID), with a linear diode array attached to the collimator and with film. The dose in the reference point was monitored using an ionization chamber. Tests were performed for several intensity modulated fields using 10 and 25 MV photon beams. Based on film measurements for sweeping 0.1 cm leaf gaps it was concluded that in an 80 days period the variation in leaf positioning was within 0.05 cm, without requiring any recalibration. For a uniform 10x10 cm2 field, realized dynamically by a scanning 0.4x10 cm2 slit beam, a maximum variation in slit width of 0.01 cm was derived from ionization chamber measurements, both in time and for gantry rotation. For a clinical example, the dose in the reference point reproduced within 0.2% (1 SD) over a period of 100 days. Apart from regions with very large dose gradients, variations in the relative beam profiles measured with the EPID were generally less than 1% (1 SD). For different gantry angles the dose profiles also reproduced within 1

  8. Dynamical Stability of Imaged Planetary Systems in Formation: Application to HL Tau

    CERN Document Server

    Tamayo, Daniel; Menou, Kristen; Rein, Hanno

    2015-01-01

    We present a general and simple framework for understanding the dynamical stability of planets embedded in a protoplanetary nebula over typical disk lifetimes, and provide estimates for the maximum allowable planetary masses. We collect these easily evaluated dynamical constraints into a workflow that can help guide the design and interpretation of new observational campaigns and numerical simulations of gap opening in such systems. We argue that the locations of resonances should be significantly shifted from integer period ratios in massive disks like HL Tau, and that theoretical uncertainties in the exact shift, together with observational errors, imply a large uncertainty in the dynamical state and stability in such disks. This renders our results largely insensitive to an improved determination of the gaps' orbital radii, and presents an important barrier to using systems like HL Tau as a proxy for the initial conditions following planet formation. An important observational avenue to breaking this degen...

  9. Linguistic dynamic systems based on computing with words and their stabilities

    Institute of Scientific and Technical Information of China (English)

    MO Hong; WANG FeiYue

    2009-01-01

    Linguistic dynamic systems (LDS) are the systems based on computing with words (CW) instead of computing with numbers or symbols. In this paper, LDS are divided into two types: type-Ⅰ LDS being converted from conventional dynamical systems (CDS) by using extension principle and type-Ⅱ LDS by using fuzzy logic rules. For type-Ⅰ LDS, the method of endograph is provided to discuss the stabilities of type-Ⅰ LDS and two cases of stabilities of logistic mappings: one is the states being abstracted and the other is parameters also being abstracted. For type-Ⅱ LDS, the method of degree of match is used to discuss the dynamical behavior of arbitrary initial words under fuzzy rule.

  10. Aeromechanical stability analysis of a multirotor vehicle with application to hybrid heavy lift helicopter dynamics

    Science.gov (United States)

    Venkatesan, C.; Friedmann, P. P.

    1984-01-01

    The Hybrid Heavy Lift Helicopter (HHLH) is a potential candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure. Four rotor systems are also attached to the supporting structure. Nonlinear equations of motion capable of modeling the dynamics of this multi-rotor/support frame/vehicle system have been developed and used to study the fundamental aeromechanical stability characteristics of this class of vehicles. The mechanism of coupling between the blades, supporting structure and rigid body modes is identified and the effect of buoyancy ratio (buoyant lift/total weight) on the vehicle dynamics is studied. It is shown that dynamics effects have a major role in the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.

  11. Aeromechanical stability analysis of a multirotor vehicle with application to hybrid heavy lift helicopter dynamics

    Science.gov (United States)

    Venkatesan, C.; Friedmann, P. P.

    1984-01-01

    The Hybrid Heavy Lift Helicopter (HHLH) is a potential candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure. Four rotor systems are also attached to the supporting structure. Nonlinear equations of motion capable of modeling the dynamics of this multi-rotor/support frame/vehicle system have been developed and used to study the fundamental aeromechanical stability characteristics of this class of vehicles. The mechanism of coupling between the blades, supporting structure and rigid body modes is identified and the effect of buoyancy ratio (buoyant lift/total weight) on the vehicle dynamics is studied. It is shown that dynamics effects have a major role in the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.

  12. Power system dynamics and stability with synchrophasor measurement and power system toolbox

    CERN Document Server

    Sauer, Peter W; Chow, Joe H

    2017-01-01

    This new edition addresses the needs of dynamic modeling and simulation relevant to power system planning, design, and operation, including a systematic derivation of synchronous machine dynamic models together with speed and voltage control subsystems. Reduced-order modeling based on integral manifolds is used as a firm basis for understanding the derivations and limitations of lower-order dynamic models. Following these developments, a multi-machine model interconnected through the transmission network is formulated and simulated using numerical simulation methods. Energy function methods are discussed for direct evaluation of stability. Small-signal analysis is used for determining the electromechanical modes and mode-shapes, and for power system stabilizer design. Time-synchronized high-sampling-rate phasor measurement units (PMUs) to monitor power system disturbances ave been implemented throughout North America and many other countries. In this second edition, new chapters on synchrophasor measurement ...

  13. Robust Global Control Strategies for Improvement of Angular Stability using FACTS and HVDC Devices

    Science.gov (United States)

    Agnihotri, P.; Kulkarni, A. M.; Gole, A. M.

    2013-05-01

    System-wide feedback signals made available by Wide-Area Measurement Systems technology can be used in FACTS/HVDC based controllers for the improvement of angular stability. These global signals can facilitate the efficient use of controller effort to stabilize critical swing modes. This paper introduces a restricted global strategy which involves the use of specific global feedback signals which are available at the HVDC/FACTS locations. The strategy is expected to be robust to changes in the power grid as well as communication uncertainties. This paper presents a heuristic introduction to this strategy using a circuit analogy of a simplified model of a power system. Preliminary results on a small system are also presented.

  14. The Next Generation of High-Speed Dynamic Stability Wind Tunnel Testing (Invited)

    Science.gov (United States)

    Tomek, Deborah M.; Sewall, William G.; Mason, Stan E.; Szchur, Bill W. A.

    2006-01-01

    Throughout industry, accurate measurement and modeling of dynamic derivative data at high-speed conditions has been an ongoing challenge. The expansion of flight envelopes and non-conventional vehicle design has greatly increased the demand for accurate prediction and modeling of vehicle dynamic behavior. With these issues in mind, NASA Langley Research Center (LaRC) embarked on the development and shakedown of a high-speed dynamic stability test technique that addresses the longstanding problem of accurately measuring dynamic derivatives outside the low-speed regime. The new test technique was built upon legacy technology, replacing an antiquated forced oscillation system, and greatly expanding the capabilities beyond classic forced oscillation testing at both low and high speeds. The modern system is capable of providing a snapshot of dynamic behavior over a periodic cycle for varying frequencies, not just a damping derivative term at a single frequency.

  15. Dynamic stability of running: The effects of speed and leg amputations on the maximal Lyapunov exponent

    Energy Technology Data Exchange (ETDEWEB)

    Look, Nicole [Department of Applied Mathematics, University of Colorado Boulder, Boulder, Colorado 80309 (United States); Arellano, Christopher J.; Grabowski, Alena M.; Kram, Rodger [Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado 80309 (United States); McDermott, William J. [The Orthopedic Specialty Hospital, Murray, Utah 84107 (United States); Bradley, Elizabeth [Department of Computer Science, University of Colorado Boulder, Boulder, Colorado 80309, USA and Santa Fe Institute, Santa Fe, New Mexico 87501 (United States)

    2013-12-15

    In this paper, we study dynamic stability during running, focusing on the effects of speed, and the use of a leg prosthesis. We compute and compare the maximal Lyapunov exponents of kinematic time-series data from subjects with and without unilateral transtibial amputations running at a wide range of speeds. We find that the dynamics of the affected leg with the running-specific prosthesis are less stable than the dynamics of the unaffected leg and also less stable than the biological legs of the non-amputee runners. Surprisingly, we find that the center-of-mass dynamics of runners with two intact biological legs are slightly less stable than those of runners with amputations. Our results suggest that while leg asymmetries may be associated with instability, runners may compensate for this effect by increased control of their center-of-mass dynamics.

  16. Stability Testing of a Wide Bone-Anchored Device after Surgery without Skin Thinning

    Directory of Open Access Journals (Sweden)

    Malou Hultcrantz

    2015-01-01

    Full Text Available Objective. To longitudinally follow the osseointegration using Resonance Frequency Analysis (RFA for different lengths of abutment on a new wide bone-anchored implant, introduced with the non-skin thinning surgical technique. Study Design. A single-center, prospective 1 year study following adults with bone-anchored hearing implants. Materials and Methods. Implantation was performed and followed for a minimum of 1 year. All patients were operated on according to the tissue preserving technique. A 4.5 mm wide fixture (Oticon Medical with varying abutments (9 to 12 mm was used and RFA was tested 1 week, 7 weeks, 6 months, and 12 months later. Implant Stability Quotient (ISQ, was measured from 1 to 100. Stability was compared to a group of patients (N=7 implanted with another brand (Cochlear BI400 of 4.5 mm fixtures. Results. All 10 adults concluded the study. None of the participants lost their implant during the test period indicating a good anchoring of abutments to the wide fixture tested. Stability testing was shown to vary depending on abutment length and time after surgery and with higher values for shorter abutments and increasing values over the first period of time. One patient changed the abutment from 12 to 9 mm and another from a 9 to a 12 during the year. No severe skin problems, numbness around the implant, or cosmetic problems arose. Conclusion. After 1 year of follow-up, combination of a wide fixture implant and the non-skin thinning surgical technique indicates a safe procedure with good stability and no abutment losses.

  17. Nonspherical dynamics and shape mode stability of ultrasound contrast agent microbubbles

    Science.gov (United States)

    Calvisi, Michael

    2016-11-01

    Ultrasound contrast agents (UCAs) are shell encapsulated microbubbles developed originally for ultrasound imaging enhancement. UCAs are more recently being exploited for therapeutic applications, such as for drug delivery, gene therapy, and tissue ablation. Ultrasound transducer pulses can induce spherical (radial) UCA oscillations, translation, and nonspherical shape oscillations, the dynamics of which are highly coupled. If driven sufficiently strongly, the ultrasound can induce breakup of UCAs, which can facilitate drug or gene delivery but should be minimized for imaging purposes to increase residence time and maximize diagnostic effect. Therefore, an understanding of the interplay between the acoustic driving and nonspherical shape mode stability of UCAs is essential for both diagnostic and therapeutic applications. In this work, we use both analytical and numerical methods to analyze shape mode stability for cases of small and large nonspherical oscillations, respectively. To analyze shape mode stability in the limit of small nonspherical perturbations, we couple a radial model of a lipid-coated microbubble with a model for bubble translation and nonspherical shape oscillation. This hybrid model is used to predict shape mode stability for ultrasound driving frequencies and pressure amplitudes of clinical interest. In addition, calculations of the stability of individual shape modes, residence time, maximum radius, and translation are provided with respect to acoustic driving parameters and compared to an unshelled bubble. The effects of shell elasticity, shell viscosity, and initial radius on stability are investigated. Furthermore, the well-established boundary element method (BEM) is used to investigate the dynamics and shape stability of large amplitude nonspherical oscillations of an ultrasonically-forced, polymer-coated microbubble near a rigid boundary. Different instability modes are identified based on the degree of jetting and proximity to the

  18. Polyethylenimine Interfacial Layers in Inverted Organic Photovoltaic Devices: Effects of Ethoxylation and Molecular Weight on Efficiency and Temporal Stability.

    Science.gov (United States)

    Courtright, Brett A E; Jenekhe, Samson A

    2015-12-02

    We report a comparative study of polyethylenimine (PEI) and ethoxylated-polyethylenimine (PEIE) cathode buffer layers in high performance inverted organic photovoltaic devices. The work function of the indium-tin oxide (ITO)/zinc oxide (ZnO) cathode was reduced substantially (Δφ = 0.73-1.09 eV) as the molecular weight of PEI was varied from 800 g mol(-1) to 750 000 g mol(-1) compared with the observed much smaller reduction when using a PEIE thin film (Δφ = 0.56 eV). The reference inverted polymer solar cells based on the small band gap polymer PBDTT-FTTE (ITO/ZnO/PBDTT-FTTE:PC70BM/MoO3/Ag), without a cathode buffer layer, had an average power conversion efficiency (PCE) of 6.06 ± 0.22%. Incorporation of a PEIE cathode buffer layer in the same PBDTT-FTTE:PC70BM blend devices gave an enhanced performance with a PCE of 7.37 ± 0.53%. In contrast, an even greater photovoltaic efficiency with a PCE of 8.22 ± 0.10% was obtained in similar PBDTT-FTTE:PC70BM blend solar cells containing a PEI cathode buffer layer. The temporal stability of the inverted polymer solar cells was found to increase with increasing molecular weight of the cathode buffer layer. The results show that PEI is superior to PEIE as a cathode buffer layer in high performance organic photovoltaic devices and that the highest molecular weight PEI interlayer provides the highest temporal stability.

  19. Micro- and nanoscale devices for the investigation of epigenetics and chromatin dynamics

    Science.gov (United States)

    Aguilar, Carlos A.; Craighead, Harold G.

    2013-10-01

    Deoxyribonucleic acid (DNA) is the blueprint on which life is based and transmitted, but the way in which chromatin -- a dynamic complex of nucleic acids and proteins -- is packaged and behaves in the cellular nucleus has only begun to be investigated. Epigenetic modifications sit 'on top of' the genome and affect how DNA is compacted into chromatin and transcribed into ribonucleic acid (RNA). The packaging and modifications around the genome have been shown to exert significant influence on cellular behaviour and, in turn, human development and disease. However, conventional techniques for studying epigenetic or conformational modifications of chromosomes have inherent limitations and, therefore, new methods based on micro- and nanoscale devices have been sought. Here, we review the development of these devices and explore their use in the study of DNA modifications, chromatin modifications and higher-order chromatin structures.

  20. Long-term stability assessment of AlGaN/GaN field effect transistors modified with peptides: Device characteristics vs. surface properties

    Energy Technology Data Exchange (ETDEWEB)

    Rohrbaugh, Nathaniel; Bryan, Isaac; Bryan, Zachary; Collazo, Ramon; Ivanisevic, Albena, E-mail: ivanisevic@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695 (United States)

    2015-09-15

    AlGaN/GaN Field Effect Transistors (FETs) are promising biosensing devices. Functionalization of these devices is explored in this study using an in situ approach with phosphoric acid etchant and a phosphonic acid derivative. Devices are terminated on peptides and soaked in water for up to 168 hrs to examine FETs for both device responses and surface chemistry changes. Measurements demonstrated threshold voltage shifting after the functionalization and soaking processes, but demonstrated stable FET behavior throughout. X-ray photoelectron spectroscopy and atomic force microscopy confirmed peptides attachment to device surfaces before and after water soaking. Results of this work point to the stability of peptide coated functionalized AlGaN/GaN devices in solution and support further research of these devices as disposable, long term, in situ biosensors.

  1. An upper-body can improve the stability and efficiency of passive dynamic walking.

    Science.gov (United States)

    Chyou, T; Liddell, G F; Paulin, M G

    2011-09-21

    The compass-gait walker proposed by McGeer can walk down a shallow slope with a self-stabilizing gait that requires no actuation or control. However, as the slope goes to zero so does the walking speed, and dynamic gait stability is only possible over a very narrow range of slopes. Gomes and Ruina have results demonstrating that by adding a torso to the compass-gait walker, it can walk passively on level-ground with a non-infinitesimal constant average speed. However, the gait involves exaggerated joint movements, and for energetic reasons horizontal passive dynamic walking cannot be stable. We show in this research that in addition to collision-free walking, adding a torso improves stability and walking speed when walking downhill. Furthermore, adding arms to the torso results in a collision-free periodic gait with natural-looking torso and limb movements. Overall, in contrast to the suggestions that active control may be needed to balance an upper-body on legs, it turns out that the upper and lower bodies can be integrated to improve the stability, efficiency and speed of a passive dynamic walker. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. On Stabilizing the Variance of Dynamic Functional Brain Connectivity Time Series.

    Science.gov (United States)

    Thompson, William Hedley; Fransson, Peter

    2016-12-01

    Assessment of dynamic functional brain connectivity based on functional magnetic resonance imaging (fMRI) data is an increasingly popular strategy to investigate temporal dynamics of the brain's large-scale network architecture. Current practice when deriving connectivity estimates over time is to use the Fisher transformation, which aims to stabilize the variance of correlation values that fluctuate around varying true correlation values. It is, however, unclear how well the stabilization of signal variance performed by the Fisher transformation works for each connectivity time series, when the true correlation is assumed to be fluctuating. This is of importance because many subsequent analyses either assume or perform better when the time series have stable variance or adheres to an approximate Gaussian distribution. In this article, using simulations and analysis of resting-state fMRI data, we analyze the effect of applying different variance stabilization strategies on connectivity time series. We focus our investigation on the Fisher transformation, the Box-Cox (BC) transformation and an approach that combines both transformations. Our results show that, if the intention of stabilizing the variance is to use metrics on the time series, where stable variance or a Gaussian distribution is desired (e.g., clustering), the Fisher transformation is not optimal and may even skew connectivity time series away from being Gaussian. Furthermore, we show that the suboptimal performance of the Fisher transformation can be substantially improved by including an additional BC transformation after the dynamic functional connectivity time series has been Fisher transformed.

  3. Voltage stability analysis of grid-connected wind farms with FACTS: Static and dynamic analysis

    Directory of Open Access Journals (Sweden)

    Kevin Zibran Heetun

    2016-01-01

    Full Text Available Recently, analysis of some major blackouts and failures of power system shows that voltage instability problem has been one of the main reasons of these disturbances and network collapses. In this article, a systematic approach to voltage stability analysis using various techniques for the IEEE 14-bus case study is presented. Static analysis is used to analyze the voltage stability of the system under study, while the dynamic analysis is used to evaluate the performance of compensators. The static techniques used are power flow, V–P curve analysis, and Q–V modal analysis. In this study, Flexible Alternating Current Transmission system (FACTS devices—namely, static synchronous compensators (STATCOMs and static var compensators (SVCs—are used as reactive power compensators, taking into account maintaining the violated voltage magnitudes of the weak buses within the acceptable limits defined in ANSI C84.1. Simulation results validate that both the STATCOMs and the SVCs can be effectively used to enhance the static voltage stability and increasing network loadability margin. Additionally, based on the dynamic analysis results, it has been shown that STATCOMs have superior performance, in dynamic voltage stability enhancement, compared to SVCs.

  4. Torsional Stiffness Effects on the Dynamic Stability of a Horizontal Axis Wind Turbine Blade

    Directory of Open Access Journals (Sweden)

    Min-Soo Jeong

    2013-04-01

    Full Text Available Aeroelastic instability problems have become an increasingly important issue due to the increased use of larger horizontal axis wind turbines. To maintain these large structures in a stable manner, the blade design process should include studies on the dynamic stability of the wind turbine blade. Therefore, fluid-structure interaction analyses of the large-scaled wind turbine blade were performed with a focus on dynamic stability in this study. A finite element method based on the large deflection beam theory is used for structural analysis considering the geometric nonlinearities. For the stability analysis, a proposed aerodynamic approach based on Greenberg’s extension of Theodorsen’s strip theory and blade element momentum method were employed in conjunction with a structural model. The present methods proved to be valid for estimations of the aerodynamic responses and blade behavior compared with numerical results obtained in the previous studies. Additionally, torsional stiffness effects on the dynamic stability of the wind turbine blade were investigated. It is demonstrated that the damping is considerably influenced by variations of the torsional stiffness. Also, in normal operating conditions, the destabilizing phenomena were observed to occur with low torsional stiffness.

  5. Non-Topological (Dynamical) Approach to Stability of 't Hooft-Polyakov Monopole

    CERN Document Server

    Qandalji, K Rasem

    2012-01-01

    At classical level, dynamical derivation of the properties and conservation laws for topologically non-trivial systems from Noether theorem versus the derivation of the system's properties on topological grounds are considered as distinct. We do celebrate any agreements in results derived from these two distinct approaches: i.e. the dynamical versus the topological approach. Here we consider the Corrigan-Olive-Fairlie-Nuyts solution based on which we study the stability of the 't Hooft- Polyakov outer field, known as its Higgs vacuum, and derive its stability, dynamically, from the equations of motion rather than from the familiar topological approach. Then we use our derived result of the preservation of the Higgs vacuum asymptotically to derive the stability of the 't Hooft-Polyakov monopole, even if inner core is perturbed, where we base that on observing that the magnetic charge must be conserved if the Higgs vacuum is preserved asymptotically. We also, alternatively, note stability of 't Hooft-Polyakov m...

  6. Research on Dynamics and Stability in the Stairs-climbing of a Tracked Mobile Robot

    Directory of Open Access Journals (Sweden)

    Weijun Tao

    2012-10-01

    Full Text Available Aiming at the functional requirement of climbing up the stairs, the dynamics and stability during a tracked mobile robot’s climbing of stairs is studied. First, from the analysis of its cross‐country performance, the mechanical structure of the tracked mobile robot is designed and the hardware composition of its control system is given. Second, based on the analysis to its stairs‐climbing process, the dynamical model of stairs‐climbing is established by using the classical mechanics method. Next, the stability conditions for its stairs‐climbing are determined and an evaluation method of its stairs‐climbing stability is proposed, based on a mechanics analysis on the robot’s backwards tumbling during the stairs‐climbing process. Through simulation and experiments, the effectiveness of the dynamical model and the stability evaluation method of the tracked mobile robot in stairs‐climbing is verified, which can provide design and analysis foundations for the tracked mobile robots’ stairs‐climbing.

  7. On the stability of a variety of organic photovoltaic devices by IPCE and in situ IPCE analyses – the ISOS-3 inter-laboratory collaboration

    DEFF Research Database (Denmark)

    Teran-Escobar, Gerardo; Tanenbaum, David; Voroshazi, Eszter

    2012-01-01

    : accelerated full sun simulation, low level indoor fluorescent lighting and dark storage. The devices were also monitored under conditions of ambient and inert (N2) atmospheres, which allows for the identification of the solar cell materials more susceptible to degradation by ambient air (oxygen and moisture......This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPV) devices prepared by leading research laboratories. All devices have been shipped to and degraded at RISØ-DTU up to 1830 hours in accordance......). The different OPVs configurations permitted the study of the intrinsic stability of the devices depending on: two different ITO-replacement alternatives, two different hole extraction layers (PEDOT:PSS and MoO3), and two different P3HT-based polymers. The response of un-encapsulated devices to ambient...

  8. Dynamic stability of communities of amphibians in short-term-flooded forest ecosystems

    Directory of Open Access Journals (Sweden)

    O. V. Zhukov

    2015-09-01

    Full Text Available The estimation of stability of amphibian populations on the basis of data of population dynamics is given. The paper shows an attempt to estimate the direction of dynamic changes of amphibian populations, and defines the rate of the system deviation from the stationary state due to possible influence of the environmental factors by using concepts such as reactivity, degree of reactivity and flexibility of the system when using their indexes. It is found that populations of amphibians are quite stable with regard to quantifying these species. Characteristic feature is the elasticity of the system. It is confirmed by the elasticity of the system species Bufo bufo (Linnaeus, 1758. TypePelobates fuscus (Laurenti, 1768 is defined as a factor of stability of the system in quantitative terms. Dependenceof dynamics of the population on its size is established using the regression equation. Dynamics of groups depends on the action of possible predictors in response to which the population of B. bufo is not changed. The ecosystem is characterized as a place of interaction between biotic factors and factors of abiotic origin, which are due to the external action. Internal factor of the ecosystem stability is the influence of some amphibian populations on the other ones. The system features sustainable and relatively stable number of B. bufo, which does not affect the level of its stability. Stationary state of the grouping is unstable due to dynamic matrix, which describes the behavior of the group in the vicinity of the first stationary state. The second steady state is stableone, and the system returns to the stationary state with the help of wave-like dynamics. On the basis of our study it is established that the number of groups of amphibians remains stable, the systems behave differently, and dynamics of their return to the stationary state is elastic or reactive one. Еcosystems within lime-ash oak forests in the Central floodplain of the Samarariver

  9. Analytical stability analysis of periodic systems by Poincaré mappings with application to rotorcraft dynamics

    Directory of Open Access Journals (Sweden)

    Henryk Flashner

    1997-01-01

    Full Text Available A point mapping analysis is employed to investigate the stability of periodic systems. The method is applied to simplified rotorcraft models. The proposed approach is based on a procedure to obtain an analytical expression for the period-to-period mapping description of system's dynamics, and its dependence on system's parameters. Analytical stability and bifurcation conditions are then determined and expressed as functional relations between important system parameters. The method is applied to investigate the parametric stability of flapping motion of a rotor and the ground resonance problem encountered in rotorcraft dynamics. It is shown that the proposed approach provides very accurate results when compared with direct numerical results which are assumed to be an “exact solution” for the purpose of this study. It is also demonstrated that the point mapping method yields more accurate results than the widely used classical perturbation analysis. The ability to perform analytical stability studies of systems with multiple degrees-of-freedom is an important feature of the proposed approach since most existing analysis methods are applicable to single degree-of-freedom systems. Stability analysis of higher dimensional systems, such as the ground resonance problems, by perturbation methods is not straightforward, and is usually very cumbersome.

  10. The effects of core stabilization exercise on dynamic balance and gait function in stroke patients.

    Science.gov (United States)

    Chung, Eun-Jung; Kim, Jung-Hee; Lee, Byoung-Hee

    2013-07-01

    [Purpose] The purpose of this study was to determine the effects of core stabilization exercise on dynamic balance and gait function in stroke patients. [Subjects] The subjects were 16 stroke patients, who were randomly divided into two groups: a core stabilization exercise group of eight subjects and control group of eight subjects. [Methods] Subjects in both groups received general training five times per week. Subjects in the core stabilization exercise group practiced an additional core stabilization exercise program, which was performed for 30 minutes, three times per week, during a period of four weeks. All subjects were evaluated for dynamic balance (Timed Up and Go test, TUG) and gait parameters (velocity, cadence, step length, and stride length). [Results] Following intervention, the core exercise group showed a significant change in TUG, velocity, and cadence. The only significant difference observed between the core group and control group was in velocity. [Conclusion] The results of this study suggest the feasibility and suitability of core stabilization exercise for stroke patients.

  11. Emulating structural stability of Pseudomonas mendocina lipase: in silico mutagenesis and molecular dynamics studies.

    Science.gov (United States)

    Saravanan, Parameswaran; Dubey, Vikash Kumar; Patra, Sanjukta

    2014-11-01

    The need of alkaline detergent-stable lipases has been growing rapidly as they are highly attractive for the production of detergents, biodiesel, pharmaceuticals agents, and various other applications. Lipase from Pseudomonas mendocina (PML) is one such candidate with triglyceride activity and non-homologous with other reported Pseudomonas lipases. The present work provides insights on the role of amino acids toward structural stability of PML. PML was subjected to mutagenesis through in silico point mutations for emulating its structural stability, the foremost property to enhance biophysiochemical properties for industrial process. The structural effects of identified mutants on PML have been analyzed through comparative atomistic molecular dynamics simulations on wild type and mutants. The in silico mutants P187A and P219A were found to stabilize their respective local dynamics and improved the structural stability of PML. The current study sheds light on the rational engineering of PML through in silico methodologies to improvise its structural stability as well as prototype for rational engineering of the lipases.

  12. Local Dynamic Stability Assessment of Motion Impaired Elderly Using Electronic Textile Pants.

    Science.gov (United States)

    Liu, Jian; Lockhart, Thurmon E; Jones, Mark; Martin, Tom

    2008-10-01

    A clear association has been demonstrated between gait stability and falls in the elderly. Integration of wearable computing and human dynamic stability measures into home automation systems may help differentiate fall-prone individuals in a residential environment. The objective of the current study was to evaluate the capability of a pair of electronic textile (e-textile) pants system to assess local dynamic stability and to differentiate motion-impaired elderly from their healthy counterparts. A pair of e-textile pants comprised of numerous e-TAGs at locations corresponding to lower extremity joints was developed to collect acceleration, angular velocity and piezoelectric data. Four motion-impaired elderly together with nine healthy individuals (both young and old) participated in treadmill walking with a motion capture system simultaneously collecting kinematic data. Local dynamic stability, characterized by maximum Lyapunov exponent, was computed based on vertical acceleration and angular velocity at lower extremity joints for the measurements from both e-textile and motion capture systems. Results indicated that the motion-impaired elderly had significantly higher maximum Lyapunov exponents (computed from vertical acceleration data) than healthy individuals at the right ankle and hip joints. In addition, maximum Lyapunov exponents assessed by the motion capture system were found to be significantly higher than those assessed by the e-textile system. Despite the difference between these measurement techniques, attaching accelerometers at the ankle and hip joints was shown to be an effective sensor configuration. It was concluded that the e-textile pants system, via dynamic stability assessment, has the potential to identify motion-impaired elderly.

  13. Effect of high hydrostatic pressure and high dynamic pressure on stability and rheological properties of model oil-in-water emulsions

    Science.gov (United States)

    Bigikocin, Erman; Mert, Behic; Alpas, Hami

    2011-09-01

    Both static and dynamic high pressure applications provide interesting modifications in food structures which lead to new product formulations. In this study, the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP), on oil-in-water emulsions were identified and compared. Microfluidization was selected from among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared with the coarse emulsions. The stability of the emulsions was determined comparatively by using an analytical photo-centrifuge device employing novel analysis technology. Whey protein isolate (WPI) in combination with a food polysaccharide (xanthan gum, guar gum or locust bean gum) were used as emulsifying and stabilizing ingredients. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities, leading to distinctive improvements in emulsion stability. On the other hand, improvements in stability obtained with HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations containing higher oil content. Apart from these, HHP treatment was found to be relatively more contributive to the enhancements in viscoelastic properties.

  14. DYNAMIC ANALYSIS OF A CRIMPING DEVICE WITH MULTIPLE CAMS USING MSC ADAMS II

    Directory of Open Access Journals (Sweden)

    Gheorghe Popescu

    2012-05-01

    Full Text Available Through the present paper, the author presents the results of the dynamic analysis with MSC ADAMS of the mechanism with a crimping device with 12 tightening cams, designed and used in the technological process of assembly of the indigenous electrical detonators. In this sense, the mechanism with multiple cams is considered a mechanical system and is treated as an assembly of rigid bodies connected by mechanical connections and elastic elements. For shaping and simulation of the mechanism with multiple cams using ADAMS program, the author got through the following stages: construction of the pattern, its testing and simulation, validation, finishing, parametrization, optimization of the pattern.

  15. Stability of Intelligent Transportation Network Dynamics: A Daily Path Flow Adjustment considering Travel Time Differentiation

    Directory of Open Access Journals (Sweden)

    Ming-Chorng Hwang

    2015-01-01

    Full Text Available A theoretic formulation on how traffic time information distributed by ITS operations influences the trajectory of network flows is presented in this paper. The interactions between users and ITS operator are decomposed into three parts: (i travel time induced path flow dynamics (PFDTT; (ii demand induced path flow dynamics (PFDD; and (iii predicted travel time dynamics for an origin-destination (OD pair (PTTDOD. PFDTT describes the collective results of user’s daily route selection by pairwise comparison of path travel time provided by ITS services. The other two components, PTTDOD and PFDD, are concentrated on the evolutions of system variables which are predicted and observed, respectively, by ITS operators to act as a benchmark in guiding the target system towards an expected status faster. In addition to the delivered modelings, the stability theorem of the equilibrium solution in the sense of Lyapunov stability is also provided. A Lyapunov function is developed and employed to the proof of stability theorem to show the asymptotic behavior of the aimed system. The information of network flow dynamics plays a key role in traffic control policy-making. The evaluation of ITS-based strategies will not be reasonable without a well-established modeling of network flow evolutions.

  16. Transmission stability and Raman-induced amplitude dynamics in multichannel soliton-based optical waveguide systems

    Science.gov (United States)

    Peleg, Avner; Nguyen, Quan M.; Tran, Thinh P.

    2016-12-01

    We study transmission stability and dynamics of pulse amplitudes in N-channel soliton-based optical waveguide systems, taking into account second-order dispersion, Kerr nonlinearity, delayed Raman response, and frequency dependent linear gain-loss. We carry out numerical simulations with systems of N coupled nonlinear Schrödinger (NLS) equations and compare the results with the predictions of a simplified predator-prey model for Raman-induced amplitude dynamics. Coupled-NLS simulations for single-fiber transmission with 2 ≤ N ≤ 4 frequency channels show stable oscillatory dynamics of soliton amplitudes at short-to-intermediate distances, in excellent agreement with the predator-prey model's predictions. However, at larger distances, we observe transmission destabilization due to resonant formation of radiative sidebands, which is caused by Kerr nonlinearity. The presence of linear gain-loss in a single fiber leads to a limited increase in transmission stability. Significantly stronger enhancement of transmission stability is achieved in a nonlinear N-waveguide coupler due to efficient suppression of radiative sideband generation by the linear gain-loss. As a result, the distances along which stable Raman-induced dynamics of soliton amplitudes is observed are significantly larger in the waveguide coupler system compared with the single-fiber system.

  17. Preliminary evaluation of posterior dynamic lumbar stabilization in lumbar degenerative disease in Chinese patients

    Institute of Scientific and Technical Information of China (English)

    JIA Yu-hua; SUN Peng-fei

    2012-01-01

    Background There has been some controversy related to the use of the Wallis system,rather than disc fusion in the treatment of patients with degenerative spine disease.Furthermore,there are no reports concerning the application of this dynamic stabilization system in Chinese patients,who have a slightly different lifestyle with Western patients.The aim of this study was to assess the safety and efficacy of the dynamic stabilization system in the treatment of degenerative spinal diseases in Chinese patients.Methods The clinical outcomes of 20 patients with lumbar degenerative disease treated by posterior decompression with the Wallis posterior dynamic lumbar stabilization implant were studied.All of the patients completed the visual analogue scale and the Chinese version of the Oswestry Disability Index.The following radiologic parameters were measured in all patients:global lordotic angles and segmental lordotic angles (stabilized segments,above and below adjacent segments).The range of motion was then calculated.Results Nineteen patients (95%) were available for follow-up.The mean follow-up period was (27.25±5.16) months (range 16-35 months).The visual analogue scale decreased from 8.55±1.21 to 2.20±1.70 (P <0.001),and the mean score on the Chinese version of the Oswestry Disability Index was improved from 79.58%±15.93% to 22.17%±17.24% (P <0.001).No significant changes were seen in the range of motion at the stabilized segments (P=0.502) and adjacent segments (above,P=0.453; below,P=0.062).The good to excellent result was 94.4% at the latest follow-up.No complications related to the use of the Wallis posterior dynamic lumbar stabilization occurred.Conclusions It was found to be both easy and safe to use the Wallis posterior dynamic lumbar stabilization implant in the treatment of degenerative lumbar disease,and the early therapeutic effectiveness is good.The Wallis system provides an alternative method for the treatment of lumbar degenerative

  18. Cell Stability Analysis of Conventional 6T Dynamic 8T SRAM Cell in 45NM Technology

    Directory of Open Access Journals (Sweden)

    K. Dhanumjaya

    2012-04-01

    Full Text Available A SRAM cell must meet requirements for operation in submicron/nano ranges. The scaling of CMOS technology has significant impact on SRAM cell -- random fluctuation of electrical characteristics and substantial leakage current. In this paper we present dynamic column based power supply 8 T SRAM cell and comparing the proposed SRAM cell with respect to conventional SRAM 6T in various aspects. To verify read stability and write ability analysis we use N-curve metric. Simulation results affirmed that proposed 8T SRAM cell achieved improved read stability, read current, and leakage current in 45nm Technology comparing with conventional 6T SRAM using cadence virtuoso tool.

  19. Cell Stability Analysis of Conventional 6T Dynamic 8T SRAM Cell in 45NM Technology

    Directory of Open Access Journals (Sweden)

    K.Padmaraju

    2012-05-01

    Full Text Available A SRAM cell must meet requirements for operation in submicron/nano ranges. The scaling of CMOS technology has significant impact on SRAM cell -- random fluctuation of electrical characteristics andsubstantial leakage current. In this paper we present dynamic column based power supply 8T SRAM cell and comparing the proposed SRAM cell with respect to conventional SRAM 6T in various aspects. To verify read stability and write ability analysis we use N-curve metric. Simulation results affirmed that proposed 8T SRAM cell achieved improved read stability, read current, and leakage current in 45nm Technology comparing with conventional 6T SRAM using cadence virtuoso tool.

  20. A new strategy for transient stability using augmented generator control and local dynamic braking

    Energy Technology Data Exchange (ETDEWEB)

    Dorsey, J.; Jiang, H.; Habetler, T. [Georgia Inst. of Tech., Atlanta, GA (United States); Qu, Z. [University of Central Florida, Orlando, FL (United States)

    1994-12-31

    A decentralized automatic control strategy for significantly improving the transient stability of a large power system is introduced. The strategy combines local dynamic braking and a straightforward augmentation of the existing turbine / governor control system that uses only local feedback. The brake resistor, which employs thick film, metal oxide technology, has no inductance and is of very low resistance, allowing its use during fault to show a generator`s acceleration. Simulation results using the 39 Bus New England system show that the strategy dramatically increases the global stability of a power system. (author) 15 refs., 7 figs., 1 tab.

  1. DYNAMIC STABILITY OF A BEAM-MODEL VISCOELASTIC PIPE FOR CONVEYING PULSATIVE FLUID

    Institute of Scientific and Technical Information of China (English)

    Xiaodong Yang; Tianzhi Yang; Jiduo Jin

    2007-01-01

    The dynamic stability in transverse vibration of a viscoelastic pipe for conveying pulsative fluid is investigated for the simply-supported case. The material property of the beammodel pipe is described by the Kelvin-type viscoelastic constitutive relation. The axial fluid speed is characterized as simple harmonic variation about a constant mean speed. The method of multiple scales is applied directly to the governing partial differential equation without discretization when the viscoelastic damping and the periodical excitation are considered small. The stability conditions are presented in the case of subharmonic and combination resonance. Numerical results show the effect of viscosity and mass ratio on instability regions.

  2. Dynamic stability of fcc crystals under isotropic loading from first principles.

    Science.gov (United States)

    Rehák, Petr; Cerný, Miroslav; Pokluda, Jaroslav

    2012-05-30

    Lattice dynamics and stability of four fcc crystals (Al, Ir, Pt and Au) under isotropic (hydrostatic) tensile loading are studied from first principles using the linear response method and the harmonic approximation. The results reveal that, contrary to former expectations, strengths of all the studied crystals are limited by instabilities related to soft phonons with finite or vanishing wavevectors. The critical strains associated with such instabilities are remarkably lower than those related to the volumetric instability. On the other hand, the corresponding reduction of the tensile strength is by 20% at the most. An analysis of elastic stability conditions is also performed and the results obtained by means of both approaches are compared.

  3. Stability and periodicity of solutions for delay dynamic systems on time scales

    Directory of Open Access Journals (Sweden)

    Zhi-Qiang Zhu

    2014-04-01

    Full Text Available This article concerns the stability and periodicity of solutions to the delay dynamic system $$ x^{\\triangle}(t=A(t x(t + F(t, x(t, x(g(t+C(t $$ on a time scale. By the inequality technique for vectors, we obtain some stability criteria for the above system. Then, by using the Horn fixed point theorem, we present some conditions under which our system is asymptotically periodic and its periodic solution is unique. In particular, the periodic solution is positive under proper assumptions.

  4. Stability of the beta-sheet of the WW domain: A molecular dynamics simulation study.

    OpenAIRE

    Ibragimova, G T; Wade, R C

    1999-01-01

    The WW domain consists of approximately 40 residues, has no disulfide bridges, and forms a three-stranded antiparallel beta-sheet that is monomeric in solution. It thus provides a model system for studying beta-sheet stability in native proteins. We performed molecular dynamics simulations of two WW domains, YAP65 and FBP28, with very different stability characteristics, in order to explore the initial unfolding of the beta-sheet. The less stable YAP domain is much more sensitive to simulatio...

  5. Static and dynamic stability of the guidance force in a side-suspended HTS maglev system

    Science.gov (United States)

    Zhou, Dajin; Cui, Chenyu; Zhao, Lifeng; Zhang, Yong; Wang, Xiqing; Zhao, Yong

    2017-02-01

    The static and dynamic stability of the guidance force in a side-suspended HTS-PMG (permanent magnetic guideway) system were studied theoretically and experimentally. It is found that there are two types of guidance force that exist in the HTS-PMG system, which are sensitive to the levitation gap and the arrangement of YBCO bulks around the central axis of the PMG. An optimized YBCO array was used to stabilize the system, which enabled a side-suspended HTS-PMG maglev vehicle to run stably at 102 km h-1 on a circular test track with 6.5 m in diameter.

  6. Nonlinear theory of combustion stability in liquid rocket engine based on chemistry dynamics

    Institute of Scientific and Technical Information of China (English)

    黄玉辉; 王振国; 周进

    2002-01-01

    Detailed models of combustion instability based on chemistry dynamics are developed. The results show that large activation energy goes against the combustion stability. The heat transfer coefficient between the wall and the combust gas is an important bifurcation parameter for the combustion instability. The acoustics modes of the chamber are in competition and cooperation with each other for limited vibration energy. Thermodynamics criterion of combustion stability can be deduced from the nonlinear thermodynamics. Correlations of the theoretical results and historical experiments indicate that chemical kinetics play a critical role in the combustion instability.

  7. Correlation of stability to varied CdCl2 treatment and related defects in CdS/CdTe PV devices as measured by thermal admittance spectroscopy

    Science.gov (United States)

    Enzenroth, R. Albert; Barth, K. L.; Sampath, W. S.

    2005-11-01

    A correlation between the CdCl2 treatment and the change in conversion efficiency with light and heat stress indoors (stability) has been shown previously by our group for CdS/CdTe:Cu PV devices. In the present work CdTe devices were fabricated with various CdCl2 treatments and with and without a Cu containing back contact. The electrical characteristics of the defects acting as traps in these devices were studied using thermal admittance spectroscopy (TAS). The activation energy Et-EV, the apparent capture cross section and the densities of state functions (using Walter's method) of the traps in the devices were estimated.

  8. On the problems of stability and durability of field-emission current sources for electrovacuum devices

    Science.gov (United States)

    Yakunin, Alexander N.; Aban'shin, Nikolay P.; Akchurin, Garif G.; Akchurin, Georgy G.; Avetisyan, Yuri A.

    2016-03-01

    The results of the practical implementation of the concept of field-emission current source with high average current density of 0.1-0.3 A-cm-2 are shown. The durability of cathode samples at a level of 6000 hours is achieved under conditions of technical vacuum. A phenomenological model is suggested that describes the tunneling of both equilibrium and nonequilibrium electrons in a vacuum from the zone of concentration of electrostatic field. Conditions are discussed as the resulting increase in the emission current due to the connection mechanism of the photoelectric effect is thermodynamically favorable, that is not accompanied by an undesirable increase in the temperature of the local emission zone. It is shown that to ensure stability and durability of the cathode is also important to limit the concentration of equilibrium carriers using composite structures «DLC film on Mo substrate." This helps to reduce the criticality of the CVC. A possible alternative is to use a restrictive resistance in the cathode. However, this increases the heat losses and thus decreases assembly efficiency. The results of experimental studies of the structure showing the saturation of photoemission current component with an increase in operating voltage. This fact suggests the existence of an effective mechanism for control of emission at constant operating voltage. This is fundamentally important for the stabilization of field emission cathode, providing a reliability and durability. The single-photon processes and the small thickness DLC films (15-20 nm) provide high-speed process of control.

  9. Invited Review Nanoscale devices fabricated by dynamic ploughing with an atomic force microscope

    Science.gov (United States)

    Kunze, Ulrich

    2002-01-01

    A review is given on the dynamic ploughing technique and its application on the fabrication of nanoscale semiconductor structures. The vibrating tip of an atomic force microscope is used to dynamically plough furrows into a polymer layer of a few nm thickness on top of the semiconductor surface. Wet-chemical etching transfers the desired line pattern. The resulting grooves of 50-100 nm width form an arrangement of barriers in the electron layer of a conventional modulation-doped GaAs/AlGaAs heterostructure. A new type of heterostructure with a compensating p-type doped cap layer shows an electron enhancement if the cap layer is selectively removed. Etching a groove in these structures enables one to induce a one-dimensional electron system. Both types of structures are used to fabricate various ballistic quantum devices and Coulomb-blockade structures.

  10. Nonlinear Dynamics of an Ambient Noise Driven Array of Coupled Graphene Nanostructured Devices for Energy Harvesting

    Directory of Open Access Journals (Sweden)

    El Aroudi A.

    2014-01-01

    Full Text Available Nonlinearities have been shown to play an important role in increasing the extracted energy of energy harvesting devices at the macro and micro scales. Vibration-based energy harvesting on the nano scale has also received attention. In this paper, we characterize the nonlinear dynamical behavior of an array of three coupled strained nanostructured graphene for its potential use in energy harvesting applications. The array is formed by three compressed vibrating membrane graphene sheet subject to external vibrational noise excitation. We present the continuous time dynamical model of the system in the form of a double-well three degree of freedom system. Random vibrations are considered as the main ambient energy source for the system and its performances in terms of the probability density function, RMS or amplitude value of the position, FFT spectra and state plane trajectories are presented in the steady state non-equilibrium regime when the noise level is considered as a control parameter.

  11. Note: Increasing dynamic range of digital-to-analog converter using a superconducting quantum interference device

    Energy Technology Data Exchange (ETDEWEB)

    Nakanishi, Masakazu, E-mail: m.nakanishi@aist.go.jp [Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, AIST Central-3, 1-1, Umezono, Tsukuba, Ibaraki 305-8563 (Japan)

    2014-10-15

    Responses of a superconducting quantum interference device (SQUID) are periodically dependent on magnetic flux coupling to its superconducting ring and the period is a flux quantum (Φ{sub o} = h/2e, where h and e, respectively, express Planck's constant and elementary charge). Using this periodicity, we had proposed a digital to analog converter using a SQUID (SQUID DAC) of first generation with linear current output, interval of which corresponded to Φ{sub o}. Modification for increasing dynamic range by interpolating within each interval is reported. Linearity of the interpolation was also based on the quantum periodicity. A SQUID DAC with dynamic range of about 1.4 × 10{sup 7} was created as a demonstration.

  12. Stability and multiattractor dynamics of a toggle switch based on a two-stage model of stochastic gene expression.

    Science.gov (United States)

    Strasser, Michael; Theis, Fabian J; Marr, Carsten

    2012-01-04

    A toggle switch consists of two genes that mutually repress each other. This regulatory motif is active during cell differentiation and is thought to act as a memory device, being able to choose and maintain cell fate decisions. Commonly, this switch has been modeled in a deterministic framework where transcription and translation are lumped together. In this description, bistability occurs for transcription factor cooperativity, whereas autoactivation leads to a tristable system with an additional undecided state. In this contribution, we study the stability and dynamics of a two-stage gene expression switch within a probabilistic framework inspired by the properties of the Pu/Gata toggle switch in myeloid progenitor cells. We focus on low mRNA numbers, high protein abundance, and monomeric transcription-factor binding. Contrary to the expectation from a deterministic description, this switch shows complex multiattractor dynamics without autoactivation and cooperativity. Most importantly, the four attractors of the system, which only emerge in a probabilistic two-stage description, can be identified with committed and primed states in cell differentiation. To begin, we study the dynamics of the system and infer the mechanisms that move the system between attractors using both the quasipotential and the probability flux of the system. Next, we show that the residence times of the system in one of the committed attractors are geometrically distributed. We derive an analytical expression for the parameter of the geometric distribution, therefore completely describing the statistics of the switching process and elucidate the influence of the system parameters on the residence time. Moreover, we find that the mean residence time increases linearly with the mean protein level. This scaling also holds for a one-stage scenario and for autoactivation. Finally, we study the implications of this distribution for the stability of a switch and discuss the influence of the

  13. Dynamizing stability

    NARCIS (Netherlands)

    Boumans, Marcel

    2009-01-01

    This article aims to show the mathematical contexts out of which emerged Solow's 1957 article “Technical Change and the Aggregate Production Function.” In particular, it seeks to provide some understanding of its most striking feature, namely, the highly aggregate level on which technical change is

  14. Dynamizing stability

    NARCIS (Netherlands)

    Boumans, Marcel|info:eu-repo/dai/nl/075268574

    2009-01-01

    This article aims to show the mathematical contexts out of which emerged Solow's 1957 article “Technical Change and the Aggregate Production Function.” In particular, it seeks to provide some understanding of its most striking feature, namely, the highly aggregate level on which technical change is

  15. Dynamizing stability

    NARCIS (Netherlands)

    Boumans, M.

    2009-01-01

    This article aims to show the mathematical contexts out of which emerged Solow's 1957 article "Technical Change and the Aggregate Production Function." In particular, it seeks to provide some understanding of its most striking feature, namely, the highly aggregate level on which technical change is

  16. FINANCIAL STABILITY OF SMALL BUSINESS: THE ESTIMATION AND DYNAMICS OF REGIONAL DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    A.U. Makarova

    2008-03-01

    Full Text Available In clause the problem of an estimation of financial stability of the enterprises of small business is considered. It is offered to use traditional indicators of an estimation of the financial stability, describing it in the short-term period, and such indicators as equation of monetary streams, qualitative risk-management, a level äèâåðñèôèêàöèè business and competitive position of the company for an estimation of stability in the long-term period. On the basis of data of statistical supervision over small enterprises the estimation of dynamics of results of financial activity and financial stability of small enterprises of Sverdlovsk area is lead to 2001 – 2005 is drawn a conclusion about low parameters of solvency and financial stability of small enterprises of region in comparison with normative parameters and data on the large and average enterprises. The measures directed on increase of financial stability of the enterprises of small business are offered.

  17. TWO-MODE GALERKIN APPROACH IN DYNAMIC STABILITY ANALYSIS OF VISCOELASTIC PLATES

    Institute of Scientific and Technical Information of China (English)

    张能辉; 程昌钧

    2003-01-01

    The dynamic stability of viscoelastic thin plates with large deflections was investigated by using the largest Liapunov exponent analysis and other numerical and analytical dynamic methods. The material behavior was described in terms of the Boltzmann superposition principle. The Galerkin method was used to simplify the original integropartial-differential model into a two-mode approximate integral model, which further reduced to an ordinary differential model by introducing new variables. The dynamic properties of one-mode and two-mode truncated systems were numerically compared. The influence of viscoelastic properties of the material, the loading amplitude and the initial values on the dynamic behavior of the plate under in-plane periodic excitations was discussed.

  18. Feedback control stabilization of critical dynamics via resource transport on multilayer networks: How glia enable learning dynamics in the brain

    Science.gov (United States)

    Virkar, Yogesh S.; Shew, Woodrow L.; Restrepo, Juan G.; Ott, Edward

    2016-10-01

    Learning and memory are acquired through long-lasting changes in synapses. In the simplest models, such synaptic potentiation typically leads to runaway excitation, but in reality there must exist processes that robustly preserve overall stability of the neural system dynamics. How is this accomplished? Various approaches to this basic question have been considered. Here we propose a particularly compelling and natural mechanism for preserving stability of learning neural systems. This mechanism is based on the global processes by which metabolic resources are distributed to the neurons by glial cells. Specifically, we introduce and study a model composed of two interacting networks: a model neural network interconnected by synapses that undergo spike-timing-dependent plasticity; and a model glial network interconnected by gap junctions that diffusively transport metabolic resources among the glia and, ultimately, to neural synapses where they are consumed. Our main result is that the biophysical constraints imposed by diffusive transport of metabolic resources through the glial network can prevent runaway growth of synaptic strength, both during ongoing activity and during learning. Our findings suggest a previously unappreciated role for glial transport of metabolites in the feedback control stabilization of neural network dynamics during learning.

  19. More stability and robustness with the multi-loop control solution for dynamic voltage restorer (DVR)

    OpenAIRE

    2009-01-01

    This paper presents the application of dynamic voltage restorers (DVR) on power distribution systems for mitigation of voltage sags/swells at critical loads. DVR is one of the compensating types of custom power devices. An adequate modeling and simulation of DVR, including controls in MATLAB, based on forced-commutated voltage source converter (VSC), has been proved suitable for compensating the voltage sags/swells. In this paper, a double loop control method is proposed for the improvement o...

  20. Study on dynamic anti-sliding stability of a high gravity dam considering complex dam foundation

    Directory of Open Access Journals (Sweden)

    Deng-hong CHEN

    2011-06-01

    Full Text Available There existed some limitations when analyzing the anti-sliding seismic stability of dam-foundation system by traditional pseudo-static method and response spectrum method. The dynamic strength reduction method was used to study on the deep anti-sliding stability of a high gravity dam considering complex dam foundation under strong earthquake-induced ground action. The static analysis was firstly carried out by reducing the shear strength parameters of the dam foundation’s rock mass with equal proportion. Then, the time-history seismic analysis was carried out based on the static analysis. It was proposed as one of dynamic instability criterions that the peak values of the dynamic displacements and plastic strain energy change suddenly with increasing strength reduction coefficient. The elasto-plastic behavior of the dam foundation was idealized using Drucker–Prager yield criterion based on associated flow rule assumption. Through the static, dynamic strength reduction analysis and dynamic linear elastic analysis of the overflow dam monolith of a high gravity dam, the results’ reliability of elastic-plastic time history analysis was confirmed. The results also showed that the rock mass strength of the high gravity dam foundation has higher strength reserve coefficient. The instability criterions of dynamic strength reduction method proposed were feasible. Although the static anti-slide analysis methods and standards of gravity dam based on the numerical methods are being discussed at present, the dynamic calculation method and instability criterions proposed in this paper would provide some meaningful suggestions for the dynamic analysis of the similar projects.

  1. Dynamic Stability of Zaghloul Drainage Pumping Station, Kafr El Shiekh, Egypt

    Directory of Open Access Journals (Sweden)

    Ibrahim R. Teaima

    2016-09-01

    Full Text Available Zaghloul Pumping Station located at El-Moheet drainage in Kafr El Sheikh Governorate. The station consists of four axial pumping units. The operating system depends on running not more than three pumping units. The old station is replaced by new one and the old sump is reused with some modifications. Each pump takes 20 second to start and takes 300 second to reach steady state. Activation more than two units lead to decrease the suction water level, disturbance of velocity distribution in suction intake and increase vibration and noise levels. The disturbance in velocity distribution generates dynamic instability of pumping units which leads to failure, damage and other operation and maintenance difficulties. Field measurements and numerical simulation were done to investigate dynamic stability of the station. The Solid Works flow simulation software, Computational Fluid Dynamics (CFD is used to simulate the flow conditions at different water levels to predict the hydraulic problem at the suction side. The field measurements are used to investigate the dynamic problem. Measurements are used to measure pump flow rate, pump head and vibration levels. The (MVP2C OneproD/ ACOEM two channel vibration analyzer and data collector was used to prepare dynamic balancing for each unit with different weights. In general, the results indicated that with the decrease of water level; approach velocity increases, swirl and vortices induce vibrations and excessive bearing loads. From simulation results the geometry of suction intake is proper for running three parallel axial flow pumps with the designed flow rate. The input data to simulation model were taken from the filed measurements and this data is validating to simulation model. The dynamic balancing as a solution leads to reduce vibration level and save bearing life. It is very important to investigate the dynamic stability and check the dynamic balancing for pumping units at the primary operation of the

  2. Conceptual Design Optimization of an Augmented Stability Aircraft Incorporating Dynamic Response and Actuator Constraints

    Science.gov (United States)

    Welstead, Jason; Crouse, Gilbert L., Jr.

    2014-01-01

    Empirical sizing guidelines such as tail volume coefficients have long been used in the early aircraft design phases for sizing stabilizers, resulting in conservatively stable aircraft. While successful, this results in increased empty weight, reduced performance, and greater procurement and operational cost relative to an aircraft with optimally sized surfaces. Including flight dynamics in the conceptual design process allows the design to move away from empirical methods while implementing modern control techniques. A challenge of flight dynamics and control is the numerous design variables, which are changing fluidly throughout the conceptual design process, required to evaluate the system response to some disturbance. This research focuses on addressing that challenge not by implementing higher order tools, such as computational fluid dynamics, but instead by linking the lower order tools typically used within the conceptual design process so each discipline feeds into the other. In thisresearch, flight dynamics and control was incorporated into the conceptual design process along with the traditional disciplines of vehicle sizing, weight estimation, aerodynamics, and performance. For the controller, a linear quadratic regulator structure with constant gains has been specified to reduce the user input. Coupling all the disciplines in the conceptual design phase allows the aircraft designer to explore larger design spaces where stabilizers are sized according to dynamic response constraints rather than historical static margin and volume coefficient guidelines.

  3. ANALYSIS OF THE DYNAMIC STABILITY OF ELECTRICAL GRADED PIEZOELECTRIC CIRCULAR CYLINDRICAL SHELLS

    Institute of Scientific and Technical Information of China (English)

    ZhuJunqiang; ShenYapeng; ChenChangqing

    2004-01-01

    A system of Mathieu Hill equations have been obtained for the dynamic stability analysis of electrical graded piezoelectric circular cylindrical shells subjected to the combined loading of periodic axial compression and radial pressure and electric field. Bolotin's method is then employed to obtain the dynamic instability regions. It is revealed that the piezoelectric effect, the piezoelectric graded effect and the electric field only have minor effect on the unstable region. In contrast, the geometric parameters, the rigidity of constituent materials and the external loading play a dominant role in determining the unstable region.

  4. Accuracy Enhanced Stability and Structure Preserving Model Reduction Technique for Dynamical Systems with Second Order Structure

    DEFF Research Database (Denmark)

    Tahavori, Maryamsadat; Shaker, Hamid Reza

    A method for model reduction of dynamical systems with the second order structure is proposed in this paper. The proposed technique preserves the second order structure of the system, and also preserves the stability of the original systems. The method uses the controllability and observability...... gramians within the time interval to build the appropriate Petrov-Galerkin projection for dynamical systems within the time interval of interest. The bound on approximation error is also derived. The numerical results are compared with the counterparts from other techniques. The results confirm...

  5. Stability of the Supply Chain Using System Dynamics Simulation and the Accumulated Deviations from Equilibrium

    Directory of Open Access Journals (Sweden)

    Luis Rabelo

    2011-01-01

    Full Text Available We propose and demonstrate a new methodology to stabilize systems with complex dynamics like the supply chain. This method is based on the accumulated deviations from equilibrium (ADE. It is most beneficial for controlling system dynamic models characterized by multiple types of delays, many interacting variables, and feedback processes. We employ the classical version of particle swarm optimization as the optimization approach due to its performance in multidimensional space, stochastic properties, and global reach. We demonstrate the effectiveness of our method based on ADE using a manufacturing-supply-chain case study.

  6. Dynamic axial stabilization of counterpropagating beam-traps with feedback control

    DEFF Research Database (Denmark)

    Tauro, Sandeep; Bañas, Andrew Rafael; Palima, Darwin

    2010-01-01

    Optical trapping in a counter-propagating (CP) beam-geometry provides unique advantages in terms of working distance, aberration requirements and intensity hotspots. However, its axial performance is governed by the wave propagation of the opposing beams, which can limit the practical geometries....... Here we propose a dynamic method for controlling axial forces to overcome this constraint. The technique uses computervision object tracking of the axial position, in conjunction with softwarebased feedback, for dynamically stabilizing the axial forces. We present proof-of-concept experiments showing...

  7. Jump and pull-in dynamics of an electrically actuated bistable MEMS device

    KAUST Repository

    Ruzziconi, Laura

    2014-09-01

    This study analyzes a theoretical bistable MEMS device, which exhibits a considerable versatility of behavior. After exploring the coexistence of attractors, we focus on each rest position, and investigate the final outcome, when the electrodynamic voltage is suddenly applied. Our aim is to describe the parameter range where each attractor may practically be observed under realistic conditions, when an electric load is suddenly applied. Since disturbances are inevitably encountered in experiments and practice, a dynamical integrity analysis is performed in order to take them into account. We build the integrity charts, which examine the practical vulnerability of each attractor. A small integrity enhances the sensitivity of the system to disturbances, leading in practice either to jump or to dynamic pull-in. Accordingly, the parameter range where the device, subjected to a suddenly applied load, can operate in safe conditions with a certain attractor is smaller, and sometimes considerably smaller, than in the theoretical predictions. While we refer to a particular case-study, the approach is very general.

  8. Experimental study of gradual/abrupt dynamics of HfO2-based memristive devices

    Science.gov (United States)

    Brivio, S.; Covi, E.; Serb, A.; Prodromakis, T.; Fanciulli, M.; Spiga, S.

    2016-09-01

    The resistance switching dynamics of TiN/HfO2/Pt devices is analyzed in this paper. When biased with a voltage ramp of appropriate polarity, the devices experience SET transitions from high to low resistance states in an abrupt manner, which allows identifying a threshold voltage. However, we find that the stimulation with trains of identical pulses at voltages near the threshold results in a gradual SET transition, whereby the resistive state visits a continuum of intermediate levels as it approaches some low resistance state limit. On the contrary, RESET transitions from low to high resistance states proceed in a gradual way under voltage ramp stimulation, while gradual resistance changes driven by trains of identical spikes cover only a limited resistance window. The results are discussed in terms of the relations among the thermo-electrochemical effects of Joule heating, ion mobility, and resistance change, which provide positive and negative closed loop processes in SET and RESET, respectively. Furthermore, the effect of the competition between opposite tendencies of filament dissolution and formation at opposite metal/HfO2 interfaces is discussed as an additional ingredient affecting the switching dynamics.

  9. On the dynamical stability of the proposed planetary system orbiting NSVS 14256825

    CERN Document Server

    Wittenmyer, Robert A; Marshall, Jonathan

    2013-01-01

    We present a detailed dynamical analysis of the orbital stability of the two circumbinary planets recently proposed to orbit the evolved eclipsing binary star system NSVS 14256825. As is the case for other recently proposed circumbinary planetary systems detected through the timing of mutual eclipses between the central binary stars, the proposed planets do not stand up to dynamical scrutiny. The proposed orbits for the two planets are extremely unstable on timescales of less than a thousand years, regardless of the mutual inclination between the planetary orbits. For the scenario where the planetary orbits are coplanar, a small region of moderate stability was observed, featuring orbits that were somewhat protected from destabilisation by the influence of mutual 2:1 mean-motion resonance between the orbits of the planets. Even in this stable region, however, the systems tested typically only survived on timescales of order 1 million years, far shorter than the age of the system. Our results suggest that, if ...

  10. Dynamic stabilities of icosahedral-like clusters and their ability to form quasicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Xiaogang; Hamid, Ilyar; Duan, Haiming, E-mail: dhm@xju.edu.cn [College of Physics Science and Technology. Xinjiang University, Urumqi 830046 (China)

    2016-06-15

    The dynamic stabilities of the icosahedral-like clusters containing up to 2200 atoms are investigated for 15 metal elements. The clusters originate from five different initial structures (icosahedron, truncated decahedron, octahedron, closed-shell fragment of an HCP structure, and non-closed-shell fragment of an HCP structure). The obtained order of the dynamic stabilities of the icosahedral-like clusters can be assigned to three groups, from stronger to weaker, according to the size ranges involved: (Zr, Al, Ti) > (Cu, Fe, Co, Ni, Mg, Ag) > (Pb, Au, Pd, Pt, Rh, Ir), which correspond to the predicted formation ability of the quasicrystals. The differences of the sequences can be explained by analyzing the parameters of the Gupta-type many-body inter-atomic potentials.

  11. Dynamic angle stability of an industrial turbo generator connected in power system

    Science.gov (United States)

    Grouni, S.; Hallak, M.; Aibeche, A.; Ramdani, A.; Bouallegue, K.

    2014-12-01

    This paper deals with the dynamic problem of oscillation and damping on an industrial turbo generator connected to infinite networks. A set of equations that governs the turbo generator connected to infinite bus are written in characteristic form. The power system stabilizer PSS applied in order to solve the problem of damping internal angle and operating power system synchronization. The PSS model described is inspired from Heffron-Philips model is applied on real parameters simulation under Matlab simulink. The results obtained from practical application are advantageous which variations of amplitude and time mitigation oscillations magnitude of electrical and mechanical output variables. This numerical experiment permits to gain more simplicity compared with several methods applied in a real operating prototyping systems. The PSS that is used will improve the dynamic stability.

  12. Dynamic stability conditions for Lotka-Volterra recurrent neural networks with delays.

    Science.gov (United States)

    Yi, Zhang; Tan, K K

    2002-07-01

    The Lotka-Volterra model of neural networks, derived from the membrane dynamics of competing neurons, have found successful applications in many "winner-take-all" types of problems. This paper studies the dynamic stability properties of general Lotka-Volterra recurrent neural networks with delays. Conditions for nondivergence of the neural networks are derived. These conditions are based on local inhibition of networks, thereby allowing these networks to possess a multistability property. Multistability is a necessary property of a network that will enable important neural computations such as those governing the decision making process. Under these nondivergence conditions, a compact set that globally attracts all the trajectories of a network can be computed explicitly. If the connection weight matrix of a network is symmetric in some sense, and the delays of the network are in L2 space, we can prove that the network will have the property of complete stability.

  13. Dynamics and Stability of Blind Grasping of a 3-Dimensional Object under Non-holonomic Constraints

    Institute of Scientific and Technical Information of China (English)

    Suguru Arimoto; Morio Yoshida; Ji-Hun Bae

    2006-01-01

    A mathematical model expressing the motion of a pair of multi-DOF robot fingers with hemi-spherical ends,grasping a 3-D rigid object with parallel flat surfaces, is derived, together with non-holonomic constraints. By referring to the fact that humans grasp an object in the form of precision prehension, dynamically and stably by opposable forces, between the thumb and another finger (index or middle finger), a simple control signal constructed from finger-thumb opposition is proposed, and shown to realize stable grasping in a dynamic sense without using object information or external sensing (this is called "blind grasp" in this paper). The stability of grasping with force/torque balance under non-holonomic constraints is analyzed on the basis of a new concept named "stability on a manifold". Preliminary simulation results are shown to verify the validity of the theoretical results.

  14. Dynamic Stability Analysis of Autonomous Medium-Voltage Mixed-Source Microgrid

    DEFF Research Database (Denmark)

    Zhao, Zhuoli; Yang, Ping; Guerrero, Josep M.

    2015-01-01

    In an autonomous microgrid without connection to the interconnected grid to support the frequency and voltage, it is more complex to control and manage. Thus in order to investigate the dynamic stability of the medium-voltage (MV) microgrid in Dongao Island, a detailed small-signal state......-space model of the autonomous MV mixed-source microgrid containing diesel generator set (DGS), grid-supporting battery energy storage system (BESS), squirrel cage induction generator (SCIG) wind turbine and network is developed. Sensitivity analysis is carried out to reveal the dynamic stability margin...... of the MV microgrid and identify the permissible variations range of the droop coefficients. Finally, the theoretical analysis is verified with time-domain simulation and experimental results....

  15. Performance of Three Mode-Meter Block-Processing Algorithms for Automated Dynamic Stability Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Trudnowski, Daniel J.; Pierre, John W.; Zhou, Ning; Hauer, John F.; Parashar, Manu

    2008-05-31

    The frequency and damping of electromechanical modes offer considerable insight into the dynamic stability properties of a power system. The performance properties of three block-processing algorithms from the perspective of near real-time automated stability assessment are demonstrated and examined. The algorithms are: the extended modified Yule Walker (YW); extended modified Yule Walker with Spectral analysis (YWS); and numerical state-space subspace system identification(N4SID) algorithm. The YW and N4SID have been introduced in previous publications while the YWS is introduced here. Issues addressed include: stability assessment requirements; automated subset selecting identified modes; using algorithms in an automated format; data assumptions and quality; and expected algorithm estimation performance.

  16. 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.

  17. Effects of head type on the stability of gemini surfactant foam by molecular dynamics simulation

    Science.gov (United States)

    Wu, Gang; Yuan, Congtai; Ji, Xianjing; Wang, Hongbing; Sun, Shuangqing; Hu, Songqing

    2017-08-01

    Molecular dynamics simulations have been carried out to study the stability of gemini surfactant foam with different head groups. The results showed that the interaction strength between the polar head groups of the surfactants and water molecules increased from 12-3S-12 (sulfate) system, 12-3Sn-12 (sulfonate) system to 12-3L-12 (carboxylate) system, and the coordination number of water molecules around head increased. From the perspective of energy, the interface formation energy of 12-3L-12 system was smallest, which means that the foam stability was the best. These results indicated that the different head type had a significant effect on the stability of gemini surfactant foam.

  18. Assessment of pipeline stability in the Gulf of Mexico during hurricanes using dynamic analysis

    Directory of Open Access Journals (Sweden)

    Yinghui Tian

    2015-03-01

    Full Text Available Pipelines are the critical link between major offshore oil and gas developments and the mainland. Any inadequate on-bottom stability design could result in disruption and failure, having a devastating impact on the economy and environment. Predicting the stability behavior of offshore pipelines in hurricanes is therefore vital to the assessment of both new design and existing assets. The Gulf of Mexico has a very dense network of pipeline systems constructed on the seabed. During the last two decades, the Gulf of Mexico has experienced a series of strong hurricanes, which have destroyed, disrupted and destabilized many pipelines. This paper first reviews some of these engineering cases. Following that, three case studies are retrospectively simulated using an in-house developed program. The study utilizes the offshore pipeline and hurricane details to conduct a Dynamic Lateral Stability analysis, with the results providing evidence as to the accuracy of the modeling techniques developed.

  19. A framework to update Hofstede's cultural value indices: economic dynamics and institutional stability

    OpenAIRE

    Linghui Tang; Peter E Koveos

    2008-01-01

    This study offers an update of the Hofstede cultural value dimensions. We argue that changes in economic conditions are the source of cultural dynamics, while the endurance of institutional characteristics provides the foundation for cultural stability. It is found that national wealth, measured by GDP per capita, has a curvilinear relationship with individualism, long-term orientation, and power distance scores. Relatively speaking, uncertainty avoidance and masculinity mainly reflect some r...

  20. Global Stability and Dynamics of Strongly Nonlinear Systems Using Koopman Operator Theory

    Science.gov (United States)

    2017-03-01

    calculus, applied mathematics, Director’s Research Initiative 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18...ARL-TR-7959 MAR 2017 US Army Research Laboratory Global Stability and Dynamics of Strongly Nonlinear Systems Using Koopman...report when it is no longer needed. Do not return it to the originator. ARL-TR-7959 ● MAR 2017 US Army Research Laboratory Global