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Sample records for invasive stabilization system

  1. The stability of the femoral component of a minimal invasive total hip replacement system.

    NARCIS (Netherlands)

    Willems, M.M.M.; Kooloos, J.G.M.; Gibbons, P.; Minderhoud, N.; Weernink, T.; Verdonschot, N.J.J.

    2006-01-01

    In this study, the initial stability of the femoral component of a minimal invasive total hip replacement was biomechanically evaluated during simulated normal walking and chair rising. A 20 mm diameter canal was created in the femoral necks of five fresh frozen human cadaver bones and the femoral

  2. Biomechanical investigation of a minimally invasive posterior spine stabilization system in comparison to the Universal Spinal System (USS).

    Science.gov (United States)

    Kubosch, D; Kubosch, E J; Gueorguiev, B; Zderic, I; Windolf, M; Izadpanah, K; Südkamp, N P; Strohm, P C

    2016-03-22

    Although minimally invasive posterior spine implant systems have been introduced, clinical studies reported on reduced quality of spinal column realignment due to correction loss. The aim of this study was to compare biomechanically two minimally invasive spine stabilization systems versus the Universal Spine Stabilization system (USS). Three groups with 5 specimens each and 2 foam bars per specimen were instrumented with USS (Group 1) or a minimally invasive posterior spine stabilization system with either polyaxial (Group 2) or monoaxial (Group 3) screws. Mechanical testing was performed under quasi-static ramp loading in axial compression and torsion, followed by destructive cyclic loading run under axial compression at constant amplitude and then with progressively increasing amplitude until construct failure. Bending construct stiffness, torsional stiffness and cycles to failure were investigated. Initial bending stiffness was highest in Group 3, followed by Group 2 and Group 1, without any significant differences between the groups. A significant increase in bending stiffness after 20'000 cycles was observed in Group 1 (p = 0.002) and Group 2 (p = 0.001), but not in Group 3, though the secondary bending stiffness showed no significant differences between the groups. Initial and secondary torsional stiffness was highest in Group 1, followed by Group 3 and Group 2, with significant differences between all groups (p ≤ 0.047). A significant increase in initial torsional stiffness after 20'000 cycles was observed in Group 2 (p = 0.017) and 3 (p = 0.013), but not in Group 1. The highest number of cycles to failure was detected in Group 1, followed by Group 3 and Group 2. This parameter was significantly different between Group 1 and Group 2 (p = 0.001), between Group 2 and Group 3 (p = 0.002), but not between Group 1 and Group 3. These findings quantify the correction loss for minimally invasive spine implant systems and imply that

  3. The Photodynamic Bone Stabilization System: a minimally invasive, percutaneous intramedullary polymeric osteosynthesis for simple and complex long bone fractures.

    Science.gov (United States)

    Vegt, Paul; Muir, Jeffrey M; Block, Jon E

    2014-01-01

    The treatment of osteoporotic long bone fractures is difficult due to diminished bone density and compromised biomechanical integrity. The majority of osteoporotic long bone fractures occur in the metaphyseal region, which poses additional problems for surgical repair due to increased intramedullary volume. Treatment with internal fixation using intramedullary nails or plating is associated with poor clinical outcomes in this patient population. Subsequent fractures and complications such as screw pull-out necessitate additional interventions, prolonging recovery and increasing health care costs. The Photodynamic Bone Stabilization System (PBSS) is a minimally invasive surgical technique that allows clinicians to repair bone fractures using a light-curable polymer contained within an inflatable balloon catheter, offering a new treatment option for osteoporotic long bone fractures. The unique polymer compound and catheter application provides a customizable solution for long bone fractures that produces internal stability while maintaining bone length, rotational alignment, and postsurgical mobility. The PBSS has been utilized in a case series of 41 fractures in 33 patients suffering osteoporotic long bone fractures. The initial results indicate that the use of the light-cured polymeric rod for this patient population provides excellent fixation and stability in compromised bone, with a superior complication profile. This paper describes the clinical uses, procedural details, indications for use, and the initial clinical findings of the PBSS.

  4. Reverse Less Invasive Stabilization System (LISS) Plating for Proximal Femur Fractures in Poliomyelitis Survivors: A Report of Two Cases.

    Science.gov (United States)

    Yao, Chen; Jin, Dongxu; Zhang, Changqing

    2017-11-15

    BACKGROUND Poliomyelitis is a neuromuscular disease which causes muscle atrophy, skeletal deformities, and disabilities. Treatment of hip fractures on polio-affect limbs is unique and difficult, since routine fixation methods like nailing may not be suitable due to abnormal skeletal structures. CASE REPORT We report one femoral neck fracture and one subtrochanteric fracture in polio survivors successfully treated with reverse less invasive stabilization system (LISS) plating technique. Both fractures were on polio-affected limbs with significant skeletal deformities and low bone density. A contralateral femoral LISS plate was applied upside down to the proximal femur as an internal fixator after indirect or direct reduction. Both patients had uneventful bone union and good functional recovery. CONCLUSIONS Reverse LISS plating is a safe and effective technique to treat hip fractures with skeletal deformities caused by poliomyelitis.

  5. Outcome analysis of retrograde nailing and less invasive stabilization system in distal femoral fractures: A retrospective analysis

    Directory of Open Access Journals (Sweden)

    Christian Hierholzer

    2011-01-01

    Full Text Available Background: Two major therapeutic principles can be employed for the treatment of distal femoral fractures: retrograde intramedullary (IM nailing (RN or less invasive stabilization on system (LISS. Both operative stabilizing systems follow the principle of biological osteosynthesis. IM nailing protects the soft-tissue envelope due to its minimally invasive approach and closed reduction techniques better than distal femoral locked plating. The purpose of this study was to evaluate and compare outcome of distal femur fracture stabilization using RN or LISS techniques. Materials and Methods: In a retrospective study from 2003 to 2008, we analyzed 115 patients with distal femur fracture who had been treated by retrograde IM nailing (59 patients or LISS plating (56 patients. In the two cohort groups, mean age was 54 years (17-89 years. Mechanism of injury was high energy impact in 57% (53% RN, 67% LISS and low-energy injury in 43% (47% RN, 33% LISS, respectively. Fractures were classified according to AO classification: there were 52 type A fractures (RN 31, LISS 21 and 63 type C fractures (RN 28, LISS 35; 32% (RN and 56% (LISS were open and 68% (RN and 44% (LISS were closed fractures, respectively. Functional and radiological outcome was assessed. Results: Clinical and radiographic evaluation demonstrated osseous healing within 6 months following RN and following LISS plating in over 90% of patients. However, no statistically significant differences were found for the parameters time to osseous healing, rate of nonunion, and postoperative complications. The following complications were treated: hematoma formation (one patient RN and three patients LISS, superficial infection (one patient RN and three patients LISS, deep infection (2 patients LISS. Additional secondary bone grafting for successful healing 3 months after the primary operation was required in four patients in the RN (7% of patients and six in the LISS group (10% of patients

  6. [Comparative study of less invasive stabilization system (LISS) and the condylar support plates for the treatment of AO type C distal femoral fractures in adults].

    Science.gov (United States)

    Chen, Yu-tao; Yang, Jiang-wei; Hou, Hai-bin; Wang, Chun-sheng; Wang, Kun-zheng

    2015-02-01

    To summarize the complications and the early clinical effect of less invasive stabilization system and the femoral condylar support plates in the treatment of AO type C distal femoral fractures. From September 2007 to February 2012, 46 patients with AO type C distal femoral fractures were retrospectively studied. Of all patients 25 were treated with less invasive stabilization system including 14 males and 11 females with a mean age of (56.3±4.2) years old; according to AO classification, there were 14 cases of C1, 8 cases of C2 and 3 cases of C3 with a mean hospital stay of (15.6±1.7) days. While 21 cases were treated with femoral condylar support plates fixation including 12 males and 9 females with a mean age of (53.8±5.1) years old;there were 13 cases of C1, 6 cases of C2 and 2 cases of C3 with a mean hospital stay of (17.8±2.2) days. Comparative analysis was performed from the operation related index,postoperative complications and Evanich score of the knee joint function between the two groups at follow-up. All 46 patients were followed up from 13 to 38 months with a mean time of 19.6 months after surgery. Complications included 1 case with infection,3 cases with internal fixation failure, 1 case with nonunion and 1 case with activity limitation of the affected knee. The differences in the incision length, blood loss, fracture healing time were significant between two groups (P0.05). The statistical significance was also found in the Evanich score at last follow-up between two groups (PAO type C distal femoral fractures.

  7. Early results of reverse less invasive stabilization system plating in treating elderly intertrochanteric fractures: a prospective study compared to proximal femoral nail.

    Science.gov (United States)

    Yao, Chen; Zhang, Chang-qing; Jin, Dong-xu; Chen, Yun-feng

    2011-07-01

    Intertrochanteric femur fracture is common in elderly population. Though multiple treatment options are available, the choice of implant remains controversial. The reverse less invasive stabilization system (LISS) plating was introduced for treatment of a patient with ipsilateral intertrochanteric and midshaft femoral fractures. The aim of this research was to compare such technique to intramedullary nailing (proximal femoral nail, PFN) for intertrochanteric fractures. Fifty-six patients with an age of at least sixty-five years and an AO/OTA type-A1 or A2 fractures were included and divided into LISS and PFN treatment group. parameters, fracture and surgery details were documented. Follow-up time was at least 12 months. Radiology, complication, Harris Hip Score and Rapid Disability Rating Score (RDRS) were recorded to evaluate fixation status and hip function for each patient during follow-up. There was no significant difference between the two groups in surgical time ((48.0 ± 8.6) minutes, vs. (51.8 ± 10.8) minutes, P = 0.3836) and intraoperative blood loss ((149.1 ± 45.1) ml vs. (176.4 ± 25.4) ml, P = 0.0712). The LISS group had less postoperative haemoglobin (Hb) reduction ((10.2 ± 4.5) g/L Hb, vs. (15.1 ± 5.9) g/L Hb, P = 0.0475). There was no complication observed in PFN group. All 31A1 type fracture in LISS group showed 100% maintenance of reduction. One nonunion with locking screw breakage and 2 varus union were found in the LISS group. Postoperative hip function was similar between the two groups. Though reverse LISS plating may not be recommended as a routine fixation method for elderly unstable intertrochanteric fractures compared to PFN, it may possibly be reserved for rapid fixation and damage control in polytrauma patients and ORIF of subtrochanteric and reverse oblique intertrochanteric fractures.

  8. 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

  9. Financial System Stability

    OpenAIRE

    Freund, Christian

    2017-01-01

    Three essays on financial system stability. The first paper explores the stability of core-periphery interbank networks in a static simulation framework. The results are then compared to a meanfield approximation. While this proves accurate in early rounds of default, precision of this approximation suffers as the simulation evolves. The second essay contributes to the empirical literature on real-world economic and financial networks. We explore the topology of the Spanish bank-firm credi...

  10. The Invasive Species Forecasting System

    Science.gov (United States)

    Schnase, John; Most, Neal; Gill, Roger; Ma, Peter

    2011-01-01

    The Invasive Species Forecasting System (ISFS) provides computational support for the generic work processes found in many regional-scale ecosystem modeling applications. Decision support tools built using ISFS allow a user to load point occurrence field sample data for a plant species of interest and quickly generate habitat suitability maps for geographic regions of management concern, such as a national park, monument, forest, or refuge. This type of decision product helps resource managers plan invasive species protection, monitoring, and control strategies for the lands they manage. Until now, scientists and resource managers have lacked the data-assembly and computing capabilities to produce these maps quickly and cost efficiently. ISFS focuses on regional-scale habitat suitability modeling for invasive terrestrial plants. ISFS s component architecture emphasizes simplicity and adaptability. Its core services can be easily adapted to produce model-based decision support tools tailored to particular parks, monuments, forests, refuges, and related management units. ISFS can be used to build standalone run-time tools that require no connection to the Internet, as well as fully Internet-based decision support applications. ISFS provides the core data structures, operating system interfaces, network interfaces, and inter-component constraints comprising the canonical workflow for habitat suitability modeling. The predictors, analysis methods, and geographic extents involved in any particular model run are elements of the user space and arbitrarily configurable by the user. ISFS provides small, lightweight, readily hardened core components of general utility. These components can be adapted to unanticipated uses, are tailorable, and require at most a loosely coupled, nonproprietary connection to the Web. Users can invoke capabilities from a command line; programmers can integrate ISFS's core components into more complex systems and services. Taken together, these

  11. Morocco; Financial System Stability Assessment

    OpenAIRE

    International Monetary Fund

    2003-01-01

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

  12. Stability analysis of nonlinear systems

    CERN Document Server

    Lakshmikantham, Vangipuram; Martynyuk, Anatoly A

    2015-01-01

    The book investigates stability theory in terms of two different measure, exhibiting the advantage of employing families of Lyapunov functions and treats the theory of a variety of inequalities, clearly bringing out the underlying theme. It also demonstrates manifestations of the general Lyapunov method, showing how this technique can be adapted to various apparently diverse nonlinear problems. Furthermore it discusses the application of theoretical results to several different models chosen from real world phenomena, furnishing data that is particularly relevant for practitioners. Stability Analysis of Nonlinear Systems is an invaluable single-sourse reference for industrial and applied mathematicians, statisticians, engineers, researchers in the applied sciences, and graduate students studying differential equations.

  13. An Adaptive Deadbeat Stabilizer for Power System Dynamic Stability

    OpenAIRE

    Rajkumar, V

    1989-01-01

    This paper discusses an adaptive deadbeat stabilizer to improve power system damping. The method involves normalized recursive least squares estimation to yield a reduced order state space model of the power system. This reduced order model is used to design the required deadbeat stabilizer recursively, along with an adaptive observer to estimate the unknown states.

  14. Long term stability of power systems

    Energy Technology Data Exchange (ETDEWEB)

    Kundur, P.; Gao, B. [Powertech Labs. Inc., Surrey, BC (Canada)

    1994-12-31

    Power system long term stability is still a developing subject. In this paper we provide our perspectives and experiences related to long term stability. The paper begins with the description of the nature of the long term stability problem, followed by the discussion of issues related to the modeling and solution techniques of tools for long term stability analysis. Cases studies are presented to illustrate the voltage stability aspect and plant dynamics aspect of long term stability. (author) 20 refs., 11 figs.

  15. New stability and stabilization for switched neutral control systems

    International Nuclear Information System (INIS)

    Xiong Lianglin; Zhong Shouming; Ye Mao; Wu Shiliang

    2009-01-01

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

  16. Shrub invasion decreases diversity and alters community stability in northern Chihuahuan Desert plant communities.

    Directory of Open Access Journals (Sweden)

    Selene Báez

    Full Text Available BACKGROUND: Global climate change is rapidly altering species range distributions and interactions within communities. As ranges expand, invading species change interactions in communities which may reduce stability, a mechanism known to affect biodiversity. In aridland ecosystems worldwide, the range of native shrubs is expanding as they invade and replace native grassland vegetation with significant consequences for biodiversity and ecosystem functioning. METHODOLOGY: We used two long-term data sets to determine the effects of shrub encroachment by Larrea tridentata on subdominant community composition and stability in formerly native perennial grassland dominated by Bouteloua eriopoda in New Mexico, USA. PRINCIPAL FINDINGS: Our results indicated that Larrea invasion decreased species richness during the last 100 years. We also found that over shorter temporal scales species-poor subdominant communities in areas invaded by Larrea were less stable (more variable in time compared to species rich communities in grass-dominated vegetation. Compositional stability increased as cover of Bouteloua increased and decreased as cover of Larrea increased. SIGNIFICANCE: Changes in community stability due to altered interspecific interactions may be one mechanism by which biodiversity declines in grasslands following shrub invasion. As global warming increases, shrub encroachment into native grasslands worldwide will continue to alter species interactions and community stability both of which may lead to a decline in biodiversity.

  17. Shrub invasion decreases diversity and alters community stability in northern Chihuahuan Desert plant communities.

    Science.gov (United States)

    Báez, Selene; Collins, Scott L

    2008-06-04

    Global climate change is rapidly altering species range distributions and interactions within communities. As ranges expand, invading species change interactions in communities which may reduce stability, a mechanism known to affect biodiversity. In aridland ecosystems worldwide, the range of native shrubs is expanding as they invade and replace native grassland vegetation with significant consequences for biodiversity and ecosystem functioning. We used two long-term data sets to determine the effects of shrub encroachment by Larrea tridentata on subdominant community composition and stability in formerly native perennial grassland dominated by Bouteloua eriopoda in New Mexico, USA. Our results indicated that Larrea invasion decreased species richness during the last 100 years. We also found that over shorter temporal scales species-poor subdominant communities in areas invaded by Larrea were less stable (more variable in time) compared to species rich communities in grass-dominated vegetation. Compositional stability increased as cover of Bouteloua increased and decreased as cover of Larrea increased. Changes in community stability due to altered interspecific interactions may be one mechanism by which biodiversity declines in grasslands following shrub invasion. As global warming increases, shrub encroachment into native grasslands worldwide will continue to alter species interactions and community stability both of which may lead to a decline in biodiversity.

  18. Financial stability of banking system in China

    OpenAIRE

    Jiang, B

    2014-01-01

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

  19. Stabilization of classic and quantum systems

    International Nuclear Information System (INIS)

    Buts, V.A.

    2012-01-01

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

  20. Stability problems for linear hyperbolic systems

    International Nuclear Information System (INIS)

    Eckhoff, K.S.

    1975-05-01

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

  1. Stabilized imploding liner fusion systems

    International Nuclear Information System (INIS)

    Book, D.L.; Cooper, A.L.; Ford, R.; Gerber, K.A.; Hammer, D.A.; Jenkins, D.J.; Robson, A.E.; Turchi, P.J.

    1977-01-01

    A new concept in imploding liner plasma compression is described in which a liquid metal liner is imploded by pistons driven by high-pressure gas, and stability of the inner surface against Rayleigh-Taylor modes is achieved by rotation. The principle has been demonstrated by using a water liner to compress air. This 'captive liner' offers the possibility of stable, reversible implosion-expansion cycles in which the plasma energy is recovered into the driving system, leading to reactor cycles with low Q and, hence, small size. A new method of setting up closed-field confinement geometries inside a liner using a rotating electron beam is described. Plasma currents induced by the beam provide initial plasma heating and generate the containment geometry. Persistence of plasma currents 100 times longer than the beam duration has been observed. Development of these methods could lead to a very compact thermonuclear reactor operating in the manner of a reciprocating engine. (author)

  2. Minimally-invasive posterior lumbar stabilization for degenerative low back pain and sciatica. A review

    Energy Technology Data Exchange (ETDEWEB)

    Bonaldi, G., E-mail: bbonaldi@yahoo.com [Neuroradiology Department, Ospedale Papa Giovanni XXIII, Bergamo (Italy); Brembilla, C. [Department of neurosurgery, Ospedale Papa Giovanni XXIII, Bergamo (Italy); Cianfoni, A. [Neuroradiology of Neurocenter of Italian Switzerland, Lugano, CH (Switzerland)

    2015-05-15

    The most diffused surgical techniques for stabilization of the painful degenerated and instable lumbar spine, represented by transpedicular screws and rods instrumentation with or without interbody cages or disk replacements, require widely open and/or difficult and poorly anatomical accesses. However, such surgical techniques and approaches, although still considered “standard of care”, are burdened by high costs, long recovery times and several potential complications. Hence the effort to open new minimally-invasive surgical approaches to eliminate painful abnormal motion. The surgical and radiological communities are exploring, since more than a decade, alternative, minimally-invasive or even percutaneous techniques to fuse and lock an instable lumbar segment. Another promising line of research is represented by the so-called dynamic stabilization (non-fusion or motion preservation back surgery), which aims to provide stabilization to the lumbar spinal units (SUs), while maintaining their mobility and function. Risk of potential complications of traditional fusion methods (infection, CSF leaks, harvest site pain, instrumentation failure) are reduced, particularly transitional disease (i.e., the biomechanical stresses imposed on the adjacent segments, resulting in delayed degenerative changes in adjacent facet joints and discs). Dynamic stabilization modifies the distribution of loads within the SU, moving them away from sensitive (painful) areas of the SU. Basic biomechanics of the SU will be discussed, to clarify the mode of action of the different posterior stabilization devices. Most devices are minimally invasive or percutaneous, thus accessible to radiologists’ interventional practice. Devices will be described, together with indications for patient selection, surgical approaches and possible complications.

  3. Stability investigation of quadratic systems with delay

    Directory of Open Access Journals (Sweden)

    Vladimir Davydov

    2000-01-01

    Full Text Available Systems of differential equations with quadratic right-hand sides with delay are considered in the paper. Compact matrix notation form is proposed for the systems of such type. Stability investigations are performed by Lyapunov's second method with functions of quadratic form. Stability conditions of quadratic systems with delay, uniformly by argument deviation, and with delay depending on the system's parameters are derived. A guaranteed radius of the ball of asymptotic stability region for zero solution is obtained.

  4. Invasive alien freshwater fishes in the Wilderness Lakes System, a ...

    African Journals Online (AJOL)

    Invasive alien freshwater fishes in the Wilderness Lakes System, a wetland of international importance in the Western Cape Province, South Africa. ... A total of 87 893 fish comprising 16 species were caught. In addition to confirming the ... Key words: freshwater fish, invasive alien fishes, estuary, RAMSAR site, diversity.

  5. Stochastic stability properties of jump linear systems

    Science.gov (United States)

    Feng, Xiangbo; Loparo, Kenneth A.; Ji, Yuandong; Chizeck, Howard J.

    1992-01-01

    Jump linear systems are defined as a family of linear systems with randomly jumping parameters (usually governed by a Markov jump process) and are used to model systems subject to failures or changes in structure. The authors study stochastic stability properties in jump linear systems and the relationship among various moment and sample path stability properties. It is shown that all second moment stability properties are equivalent and are sufficient for almost sure sample path stability, and a testable necessary and sufficient condition for second moment stability is derived. The Lyapunov exponent method for the study of almost sure sample stability is discussed, and a theorem which characterizes the Lyapunov exponents of jump linear systems is presented.

  6. Biomechanics of posterior dynamic stabilization systems.

    Science.gov (United States)

    Erbulut, D U; Zafarparandeh, I; Ozer, A F; Goel, V K

    2013-01-01

    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.

  7. 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.

  8. Stability and stabilization of linear systems with saturating actuators

    CERN Document Server

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

    2011-01-01

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

  9. Stability of endodontically treated teeth with differently invasive restorations: Adhesive vs. non-adhesive cusp stabilization.

    Science.gov (United States)

    Frankenberger, Roland; Zeilinger, Inka; Krech, Michael; Mörig, Gernot; Naumann, Michael; Braun, Andreas; Krämer, Norbert; Roggendorf, Matthias J

    2015-11-01

    Aim of the present study was to evaluate fracture strength of endodontically treated molars with different preparations/restorations after thermomechanical loading in vitro. 264 extracted human third molars were used. Beside the control group, 256 teeth in 32 test groups (n=8) received root canal treatment (MTwo #40/.6) and root canal obturation with AH Plus and Guttapercha. After postendodontic sealing and build-up (Syntac, SDR), specimens were additionally prepared MO or MOD. Postendodontic restorations were: Direct restorations (Tetric EvoCeram Bulk Fill bonded with Syntac; as filling or direct partial crown (PC) after reducing the cusps 3mm; amalgam as filling or direct pin-retained partial crown (PC)), vs. indirect adhesive restorations (I: Inlay vs. PC; IPS Empress I/PC; Celtra Duo I/PC; e.max CAD I/PC; Lava Ultimate I/PC; Enamic I/PC - all inserted with Syntac/Variolink) vs. cemented cast gold I/PC. After 300,000 thermocycles (5/55°C) and 1.2 Mio. 100N load cycles, specimens were loaded until fracture. Whereas IPS Empress showed no difference between I and PC (p>0.05), in all other groups PC were significantly more stable than fillings/inlays (pgold PC exhibited the highest fracture strengths (pAmalgam fillings showed the worst outcome (pgold PC remain the ultimate stabilization tool for ETT in terms of fracture resistance. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Fuzzy stability and synchronization of hyperchaos systems

    International Nuclear Information System (INIS)

    Wang Junwei; Xiong Xiaohua; Zhao Meichun; Zhang Yanbin

    2008-01-01

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

  11. L-type calcium channels regulate filopodia stability and cancer cell invasion downstream of integrin signalling

    Science.gov (United States)

    Jacquemet, Guillaume; Baghirov, Habib; Georgiadou, Maria; Sihto, Harri; Peuhu, Emilia; Cettour-Janet, Pierre; He, Tao; Perälä, Merja; Kronqvist, Pauliina; Joensuu, Heikki; Ivaska, Johanna

    2016-01-01

    Mounting in vitro, in vivo and clinical evidence suggest an important role for filopodia in driving cancer cell invasion. Using a high-throughput microscopic-based drug screen, we identify FDA-approved calcium channel blockers (CCBs) as potent inhibitors of filopodia formation in cancer cells. Unexpectedly, we discover that L-type calcium channels are functional and frequently expressed in cancer cells suggesting a previously unappreciated role for these channels during tumorigenesis. We further demonstrate that, at filopodia, L-type calcium channels are activated by integrin inside-out signalling, integrin activation and Src. Moreover, L-type calcium channels promote filopodia stability and maturation into talin-rich adhesions through the spatially restricted regulation of calcium entry and subsequent activation of the protease calpain-1. Altogether we uncover a novel and clinically relevant signalling pathway that regulates filopodia formation in cancer cells and propose that cycles of filopodia stabilization, followed by maturation into focal adhesions, directs cancer cell migration and invasion. PMID:27910855

  12. Nest expansion assay: a cancer systems biology approach to in vitro invasion measurements

    Directory of Open Access Journals (Sweden)

    Estrada Lourdes

    2009-07-01

    Full Text Available Abstract Background Traditional in vitro cell invasion assays focus on measuring one cell parameter at a time and are often less than ideal in terms of reproducibility and quantification. Further, many techniques are not suitable for quantifying the advancing margin of collectively migrating cells, arguably the most important area of activity during tumor invasion. We have developed and applied a highly quantitative, standardized, reproducible Nest Expansion Assay (NEA to measure cancer cell invasion in vitro, which builds upon established wound-healing techniques. This assay involves creating uniform circular "nests" of cells within a monolayer of cells using a stabilized, silicone-tipped drill press, and quantifying the margin expansion into an overlaid extracellular matrix (ECM-like component using computer-assisted applications. Findings The NEA was applied to two human-derived breast cell lines, MCF10A and MCF10A-CA1d, which exhibit opposite degrees of tumorigenicity and invasion in vivo. Assays were performed to incorporate various microenvironmental conditions, in order to test their influence on cell behavior and measures. Two types of computer-driven image analysis were performed using Java's freely available ImageJ software and its FracLac plugin to capture nest expansion and fractal dimension, respectively – which are both taken as indicators of invasiveness. Both analyses confirmed that the NEA is highly reproducible, and that the ECM component is key in defining invasive cell behavior. Interestingly, both analyses also detected significant differences between non-invasive and invasive cell lines, across various microenvironments, and over time. Conclusion The spatial nature of the NEA makes its outcome susceptible to the global influence of many cellular parameters at once (e.g., motility, protease secretion, cell-cell adhesion. We propose the NEA as a mid-throughput technique for screening and simultaneous examination of factors

  13. Stability of digital feedback control systems

    Directory of Open Access Journals (Sweden)

    Larkin Eugene

    2018-01-01

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

  14. Some results on stability of difference systems

    Directory of Open Access Journals (Sweden)

    Xiao-Song Yang

    2002-01-01

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

  15. MHD stability analysis of helical system plasmas

    International Nuclear Information System (INIS)

    Nakamura, Yuji

    2000-01-01

    Several topics of the MHD stability studies in helical system plasmas are reviewed with respect to the linear and ideal modes mainly. Difference of the method of the MHD stability analysis in helical system plasmas from that in tokamak plasmas is emphasized. Lack of the cyclic (symmetric) coordinate makes an analysis more difficult. Recent topic about TAE modes in a helical system is also described briefly. (author)

  16. Invasive fungal infections in Colombian patients with systemic lupus erythematosus.

    Science.gov (United States)

    Santamaría-Alza, Y; Sánchez-Bautista, J; Fajardo-Rivero, J F; Figueroa, C L

    2018-01-01

    Introduction Systemic lupus erythematosus is an autoimmune disease with multi-organ involvement. Complications, such as invasive fungal infections usually occur in patients with a greater severity of the disease. Objective The objective of this study was to determine the prevalence and risk variables associated with invasive fungal infections in a Colombian systemic lupus erythematosus population. Materials and methods A cross-sectional, retrospective study that evaluated patients with systemic lupus erythematosus for six years. The primary outcome was invasive fungal infection. Descriptive, group comparison and bivariate analysis was performed using Stata 12.0 software. Results Two hundred patients were included in this study; 84.5% of the patients were women and the median age was 36 years; 68% of the subjects had haematological complications; 53.3% had nephropathy; 45% had pneumopathy and 28% had pericardial impairment; 7.5% of patients had invasive fungal infections and the most frequently isolated fungus was Candida albicans. Pericardial disease, cyclophosphamide use, high disease activity, elevated ESR, C3 hypocomplementemia, anaemia and lymphopenia had a significant association with invasive fungal infection ( P lupus erythematosus, which was higher than that reported in other latitudes. In this population the increase in disease activity, the presence of pericardial impairment and laboratory alterations (anaemia, lymphopenia, increased ESR and C3 hypocomplementemia) are associated with a greater possibility of invasive fungal infections. Regarding the use of drugs, unlike other studies, in the Colombian population an association was found only with the previous administration of cyclophosphamide. In addition, patients with invasive fungal infections and systemic lupus erythematosus had a higher prevalence of mortality and hospital readmission compared with patients with systemic lupus erythematosus without invasive fungal infection.

  17. Integrative invasion science: model systems, multi-site studies, focused meta-analysis, and invasion syndromes

    Czech Academy of Sciences Publication Activity Database

    Kueffer, C.; Pyšek, Petr; Richardson, D. M.

    2013-01-01

    Roč. 200, č. 3 (2013), s. 615-633 ISSN 1469-8137 R&D Projects: GA ČR(CZ) GAP504/11/1028; GA ČR GA206/09/0563 Institutional support: RVO:67985939 Keywords : model systems * invasion syndromes * multi-site studies Subject RIV: EF - Botanics Impact factor: 6.545, year: 2013

  18. Boundary feedback stabilization of distributed parameter systems

    DEFF Research Database (Denmark)

    Pedersen, Michael

    1988-01-01

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

  19. The Nature of Stability in Replicating Systems

    Directory of Open Access Journals (Sweden)

    Addy Pross

    2011-02-01

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

  20. DESIGN POWER SYSTEM STABILIZER MENGGUNAKAN FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Ivo Salvador Soares Miranda

    2014-10-01

    Full Text Available Stabiltas merupakan kemampuan sistem untuk menjaga kondisi operasi  seimbang dan kembali kekondisi operasi normal ketika terjadi gangguan. Penerapan power system stabilizer pada sistem tenaga mampu memberikan sinyal respon yang cepat atas berbagai kondisi gangguan dan mengupayakan tidak meluasnya jangkauan gangguan. Dalam mendesign power system stabilizer menggunakan robust fuzzy logic, menggunakan satu sinyal input yaitu kecepatan deviasi rotor. Hasil simulasinya dibandingkan dengan metode fuzzy logic dan kovensional. Studi simulasi menunjukan, design power system stabilizer menggunakan robust fuzzy logic memiliki nilai sinyal peak time dan settling time relatif kecil dibandingkan dengan metode fuzzy logic dan konvensional.

  1. On formalism and stability of switched systems

    DEFF Research Database (Denmark)

    Leth, John-Josef; Wisniewski, Rafal

    2012-01-01

    In this paper, we formulate a uniform mathematical framework for studying switched systems with piecewise linear partitioned state space and state dependent switching. Based on known results from the theory of differential inclusions, we devise a Lyapunov stability theorem suitable for this class...... of switched systems. With this, we prove a Lyapunov stability theorem for piecewise linear switched systems by means of a concrete class of Lyapunov functions. Contrary to existing results on the subject, the stability theorems in this paper include Filippov (or relaxed) solutions and allow infinite switching...... in finite time. Finally, we show that for a class of piecewise linear switched systems, the inertia of the system is not sufficient to determine its stability. A number of examples are provided to illustrate the concepts discussed in this paper....

  2. Stability and boundary stabilization of 1-D hyperbolic systems

    CERN Document Server

    Bastin, Georges

    2016-01-01

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

  3. Minimal invasive stabilization of osteoporotic vertebral compression fractures. Methods and preinterventional diagnostics

    International Nuclear Information System (INIS)

    Grohs, J.G.; Krepler, P.

    2004-01-01

    Minimal invasive stabilizations represent a new alternative for the treatment of osteoporotic compression fractures. Vertebroplasty and balloon kyphoplasty are two methods to enhance the strength of osteoporotic vertebral bodies by the means of cement application. Vertebroplasty is the older and technically easier method. The balloon kyphoplasty is the newer and more expensive method which does not only improve pain but also restores the sagittal profile of the spine. By balloon kyphoplasty the height of 101 fractured vertebral bodies could be increased up to 90% and the wedge decreased from 12 to 7 degrees. Pain was reduced from 7,2 to 2,5 points. The Oswestry disability index decreased from 60 to 26 points. This effects persisted over a period of two years. Cement leakage occurred in only 2% of vertebral bodies. Fractures of adjacent vertebral bodies were found in 11%. Good preinterventional diagnostics and intraoperative imaging are necessary to make the balloon kyphoplasty a successful application. (orig.) [de

  4. Lumbar Spinal Stenosis Minimally Invasive Treatment with Bilateral Transpedicular Facet Augmentation System

    Energy Technology Data Exchange (ETDEWEB)

    Masala, Salvatore, E-mail: salva.masala@tiscali.it [Interventional Radiology and Radiotherapy, University of Rome ' Tor Vergata' , Department of Diagnostic and Molecular Imaging (Italy); Tarantino, Umberto [University of Rome ' Tor Vergata' , Department of Orthopaedics and Traumatology (Italy); Nano, Giovanni, E-mail: gionano@gmail.com [Interventional Radiology and Radiotherapy, University of Rome ' Tor Vergata' , Department of Diagnostic and Molecular Imaging (Italy); Iundusi, Riccardo [University of Rome ' Tor Vergata' , Department of Orthopaedics and Traumatology (Italy); Fiori, Roberto, E-mail: fiori.r@libero.it; Da Ros, Valerio, E-mail: valeriodaros@hotmail.com; Simonetti, Giovanni [Interventional Radiology and Radiotherapy, University of Rome ' Tor Vergata' , Department of Diagnostic and Molecular Imaging (Italy)

    2013-06-15

    Purpose. The purpose of this study was to evaluate the effectiveness of a new pedicle screw-based posterior dynamic stabilization device PDS Percudyn System Trade-Mark-Sign Anchor and Stabilizer (Interventional Spine Inc., Irvine, CA) as alternative minimally invasive treatment for patients with lumbar spine stenosis. Methods. Twenty-four consecutive patients (8 women, 16 men; mean age 61.8 yr) with lumbar spinal stenosis underwent implantation of the minimally invasive pedicle screw-based device for posterior dynamic stabilization. Inclusion criteria were lumbar stenosis without signs of instability, resistant to conservative treatment, and eligible to traditional surgical posterior decompression. Results. Twenty patients (83 %) progressively improved during the 1-year follow-up. Four (17 %) patients did not show any improvement and opted for surgical posterior decompression. For both responder and nonresponder patients, no device-related complications were reported. Conclusions. Minimally invasive PDS Percudyn System Trade-Mark-Sign has effectively improved the clinical setting of 83 % of highly selected patients treated, delaying the need for traditional surgical therapy.

  5. Environmental forcing, invasion and control of ecological and epidemiological systems.

    Science.gov (United States)

    Greenman, J V; Norman, R A

    2007-08-07

    Destabilising a biological system through periodic or stochastic forcing can lead to significant changes in system behaviour. Forcing can bring about coexistence when previously there was exclusion; it can excite massive system response through resonance, it can offset the negative effect of apparent competition and it can change the conditions under which the system can be invaded. Our main focus is on the invasion properties of continuous time models under periodic forcing. We show that invasion is highly sensitive to the strength, period, phase, shape and configuration of the forcing components. This complexity can be of great advantage if some of the forcing components are anthropogenic in origin. They can be turned into instruments of control to achieve specific objectives in ecology and disease management, for example. Culling, vaccination and resource regulation are considered. A general analysis is presented, based on the leading Lyapunov exponent criterion for invasion. For unstructured invaders, a formula for this exponent can typically be written down from the model equations. Whether forcing hinders or encourages invasion depends on two factors: the covariances between invader parameters and resident populations and the shifts in average resident population levels brought about by the forcing. The invasion dynamics of a structured invader are much more complicated but an analytic solution can be obtained in quadratic approximation for moderate forcing strength. The general theory is illustrated by a range of models drawn from ecology and epidemiology. The relationship between periodic and stochastic forcing is also considered.

  6. On Stabilization of Nonautonomous Nonlinear Systems

    International Nuclear Information System (INIS)

    Bogdanov, A. Yu.

    2008-01-01

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

  7. System and method for determining stability of a neural system

    Science.gov (United States)

    Curtis, Steven A. (Inventor)

    2011-01-01

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

  8. Simplified Stability Criteria for Delayed Neutral Systems

    Directory of Open Access Journals (Sweden)

    Xinghua Zhang

    2014-01-01

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

  9. Stability of spherical gravitating collisionless systems

    Energy Technology Data Exchange (ETDEWEB)

    Polyachenko, V.L.

    1988-03-01

    A unified method that uses a procedure, established in the paper, for reducing the problem of the stability of a spherical system to the analogous problem of perturbations of the simplest form in a corresponding cylindrical system provides the framework for investigating the stability of collisionless star clusters with different types of anisotropy of the velocity distribution. For spherical systems embedded in a massive halo or possessing a large central mass, equations - in the simplest case integral equations - for the eigenfunctions and eigenfrequencies of the oscillations are derived.

  10. Stability analysis of spacecraft power systems

    Science.gov (United States)

    Halpin, S. M.; Grigsby, L. L.; Sheble, G. B.; Nelms, R. M.

    1990-01-01

    The problems in applying standard electric utility models, analyses, and algorithms to the study of the stability of spacecraft power conditioning and distribution systems are discussed. Both single-phase and three-phase systems are considered. Of particular concern are the load and generator models that are used in terrestrial power system studies, as well as the standard assumptions of load and topological balance that lead to the use of the positive sequence network. The standard assumptions regarding relative speeds of subsystem dynamic responses that are made in the classical transient stability algorithm, which forms the backbone of utility-based studies, are examined. The applicability of these assumptions to a spacecraft power system stability study is discussed in detail. In addition to the classical indirect method, the applicability of Liapunov's direct methods to the stability determination of spacecraft power systems is discussed. It is pointed out that while the proposed method uses a solution process similar to the classical algorithm, the models used for the sources, loads, and networks are, in general, more accurate. Some preliminary results are given for a linear-graph, state-variable-based modeling approach to the study of the stability of space-based power distribution networks.

  11. Uruguay; Financial System Stability Assessment

    OpenAIRE

    International Monetary Fund

    2013-01-01

    The buffers built in the aftermath of Uruguay’s 2002 banking crisis have shielded the financial sector from the effects of the global financial turmoil. Growth has been robust and the outlook continues to be favorable. However, inflation persists but capital inflows have improved, and policy measures have been taken in response. Uruguay exhibits no obvious signs of near-term domestic macrofinancial vulnerability. The external risks to the economy and the financial system come from a fragile g...

  12. Synthesis of current knowledge on post-fire seeding for soil stabilization and invasive species control

    Science.gov (United States)

    Beyers, Jan L.; Pyke, David A.; Wirth, Troy

    2015-01-01

    The General Accounting Office has identified a need for better information on the effectiveness of post-fire emergency stabilization and rehabilitation methods used by the U.S. Forest Service and Department of Interior (DOI) agencies. Since reviews were published on treatment effectiveness in the early 2000s, treatment choices have changed and increased monitoring has been done. Greater use of native species has added substantially to burned area emergency response (BAER) treatment costs, for example, but quantitative data on this treatment were scarce in earlier reviews. We synthesized current information on the effectiveness of post-fire seeding for both soil stabilization and for prevention of the spread of invasive species in rangelands. We reviewed published literature (peer-reviewed and “gray”) and agency monitoring reports, as well as compiled and analyzed quantitative data in agency files. Products of this review include a web-accessible database of monitoring reports and published information, a scientific journal paper summarizing findings of scientific studies, an annotated bibliography of peer-reviewed papers, a summary report published as a General Technical Report that will be available online (in progress), and presentations to scientific meetings and BAER/ESR team training sessions and workshops. By combining results from studies done by Forest Service and DOI agency personnel with research studies published since the initial reviews, we presented a comprehensive synthesis of seeding effectiveness knowledge that complements the review of other hillslope treatments published by other researchers. This information will help federal land managers make more cost-effective decisions on post-fire stabilization and rehabilitation treatments.

  13. Treatment of invasive fungal infections: stability of voriconazole infusion solutions in PVC bags

    Directory of Open Access Journals (Sweden)

    Andréa I.H. Adams

    Full Text Available Voriconazole is a novel broad-spectrum antifungal drug, employed in the treatment of invasive fungal infections, and represents an alternative to amphotericin B treatment. The manufacturer recommends that any unused reconstituted product should be stored at 2ºC to 8ºC, for no more than 24 h, but no recommendations about i.v. infusion solutions are given. Previous works have reported on the stability of voriconazole in polyolefin bags and just one in 5% dextrose polyvinyl chloride (PVC bags, at a 4 mg.mL-1 concentration. In this work, the stability of voriconazole as an i.v. infusion solution in 0.9% sodium chloride and in 5% dextrose, in PVC bags, at 0.5 mg.mL-1, stored at 4 ºC and at room temperature, protected from light, was evaluated. These infusion solutions were analyzed for a 21-day period. Chemical stability was evaluated by HPLC assay. Visual inspection was performed and pH of the solutions was measured. No color change or precipitation in the solutions was observed. The drug content remained above 90% for 11 days in 0.9% sodium chloride and for 9 days in 5% dextrose solutions. The i.v. infusion solutions stored at room temperature were not stable. At room temperature, the voriconazole content dropped down to 88.3 and 86.6%, in 0.9% sodium chloride or 5% dextrose solutions, respectively, two days after admixture. Assays performed at the end of the study suggest the sorption of voriconazole by the PVC bags. The results of this study allow cost-effective batch production in the hospital pharmacy.

  14. The thioredoxin system in breast cancer cell invasion and migration

    Directory of Open Access Journals (Sweden)

    Maneet Bhatia

    2016-08-01

    Full Text Available Metastasis is the most life threatening aspect of breast cancer. It is a multi-step process involving invasion and migration of primary tumor cells with a subsequent colonization of these cells at a secondary location. The aim of the present study was to investigate the role of thioredoxin (Trx1 in the invasion and migration of breast cancer cells and to assess the strength of the association between high levels of Trx1 and thioredoxin reductase (TrxR1 expression with breast cancer patient survival. Our results indicate that the expression of both Trx1 and TrxR1 are statistically significantly increased in breast cancer patient cells compared with paired normal breast tissue from the same patient. Over-expression of Trx1 in MDA-MB-231 breast cancer cell lines enhanced cell invasion in in vitro assays while expression of a redox inactive mutant form of Trx1 (designated 1SS or the antisense mRNA inhibited cell invasion. Addition of exogenous Trx1 also enhanced cell invasion, while addition of a specific monoclonal antibody that inhibits Trx1 redox function decreased cell invasion. Over-expression of intracellular Trx1 did not increase cell migration but expression of intracellular 1SS inhibited migration. Addition of exogenous Trx1 enhanced cell migration while 1SS had no effect. Treatment with auranofin inhibited TrxR activity, cell migration and clonogenic activity of MDA-MB-231 cells, while increasing reactive oxygen species (ROS levels. Analysis of 25 independent cohorts with 5910 patients showed that Trx1 and TrxR1 were both associated with a poor patient prognosis in terms of overall survival, distant metastasis free survival and disease free survival. Therefore, targeting the Trx system with auranofin or other specific inhibitors may provide improved breast cancer patient outcomes through inhibition of cancer invasion and migration.

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

    OpenAIRE

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

    2011-01-01

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

  16. Decentralized linear quadratic power system stabilizers for multi ...

    Indian Academy of Sciences (India)

    Power system stabilizer; linear quadratic regulator; small-signal stability; transient stability. Abstract. Linear quadratic stabilizers are well-known for their superior control capabilities when compared to the conventional lead–lag power system stabilizers. However, they have not seen much of practical importance as the state ...

  17. Statistics, Formation and Stability of Exoplanetary Systems

    Science.gov (United States)

    Silburt, Ari

    Over the past two decades scientists have detected thousands of exoplanets, and their collective properties are now emerging. This thesis contributes to the exoplanet field by analyzing the statistics, formation and stability of exoplanetary systems. The first part of this thesis conducts a statistical reconstruction of the radius and period distributions of Kepler planets. Accounting for observation and detection biases, as well as measurement errors, we calculate the occurrence of planetary systems, including the prevalence of Earth-like planets. This calculation is compared to related works, finding both similarities and differences. Second, the formation of Kepler planets near mean motion resonance (MMR) is investigated. In particular, 27 Kepler systems near 2:1 MMR are analyzed to determine whether tides are a viable mechanism for transporting Kepler planets from MMR. We find that tides alone cannot transport near-resonant planets from exact 2:1 MMR to their observed locations, and other mechanisms must be invoked to explain their formation. Third, a new hybrid integrator HERMES is presented, which is capable of simulating N-bodies undergoing close encounters. HERMES is specifically designed for planets embedded in planetesimal disks, and includes an adaptive routine for optimizing the close encounter boundary to help maintain accuracy. We find the performance of HERMES comparable to other popular hybrid integrators. Fourth, the longterm stability of planetary systems is investigated using machine learning techniques. Typical studies of longterm stability require thousands of realizations to acquire statistically rigorous results, which can take weeks or months to perform. Here we find that a trained machine is capable of quickly and accurately classifying longterm planet stability. Finally, the planetary system HD155358, consisting of two Jovian-sized planets near 2:1 MMR, is investigated using previously collected radial velocity data. New orbital parameters

  18. Self-Stabilization in Membrane Systems

    Directory of Open Access Journals (Sweden)

    Artiom Alhazov

    2012-07-01

    Full Text Available In this paper we study a notion of self-stabilization, inspired from biology and engineering. Multiple variants of formalization of this notion are considered, and we discuss how such properties affect the computational power of multiset rewriting systems.

  19. Differences in stability of seed-associated microbial assemblages in response to invasion by phytopathogenic microorganisms

    Directory of Open Access Journals (Sweden)

    Samir Rezki

    2016-04-01

    Full Text Available Seeds are involved in the vertical transmission of microorganisms from one plant generation to another and consequently act as reservoirs for the plant microbiota. However, little is known about the structure of seed-associated microbial assemblages and the regulators of assemblage structure. In this work, we have assessed the response of seed-associated microbial assemblages of Raphanus sativus to invading phytopathogenic agents, the bacterial strain Xanthomonas campestris pv. campestris (Xcc 8004 and the fungal strain Alternaria brassicicola Abra43. According to the indicators of bacterial (16S rRNA gene and gyrB sequences and fungal (ITS1 diversity employed in this study, seed transmission of the bacterial strain Xcc 8004 did not change the overall composition of resident microbial assemblages. In contrast seed transmission of Abra43 strongly modified the richness and structure of fungal assemblages without affecting bacterial assemblages. The sensitivity of seed-associated fungal assemblage to Abra43 is mostly related to changes in relative abundance of closely related fungal species that belong to the Alternaria genus. Variation in stability of the seed microbiota in response to Xcc and Abra43 invasions could be explained by differences in seed transmission pathways employed by these micro-organisms, which ultimately results in divergence in spatio-temporal colonization of the seed habitat.

  20. Morocco; Financial System Stability Assessment: Update

    OpenAIRE

    International Monetary Fund

    2008-01-01

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

  1. Response Based Emergency Control System for Power System Transient Stability

    Directory of Open Access Journals (Sweden)

    Huaiyuan Wang

    2015-11-01

    Full Text Available A transient stability control system for the electric power system composed of a prediction method and a control method is proposed based on trajectory information. This system, which is independent of system parameters and models, can detect the transient stability of the electric power system quickly and provide the control law when the system is unstable. Firstly, system instability is detected by the characteristic concave or convex shape of the trajectory. Secondly, the control method is proposed based on the analysis of the slope of the state plane trajectory when the power system is unstable. Two control objectives are provided according to the methods of acquiring the far end point: one is the minimal cost to restore the system to a stable state; the other one is the minimal cost to limit the maximum swing angle. The simulation indicates that the mentioned transient stability control system is efficient.

  2. 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

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

    Science.gov (United States)

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

    2018-03-01

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

  4. Optimization of power system voltage stability

    Science.gov (United States)

    Stamp, Jason Edwin

    Contemporary power systems exist under heavy stress, caused by higher asset utilization in electric power transmission. As networks are operated nearer to their limits, new stability issues have arisen. One of the more destructive problems is voltage instability, where large areas of an electrical network may experience reduced voltages or collapse because of high reactive power demand. Voltage stability margins may be improved through the adjustment of the system operating position, which alters the power flow profile of the transmission network. Furthermore, the margins may be optimized through the application of nonlinear programming, if they are quantified using an index of voltage collapse proximity. This dissertation details the maximization of the eigenvalues of the reduced reactive power-voltage matrix, in an effort to increase voltage security. The nonlinear optimization was solved using four different techniques. First, a conventional optimal power flow was applied to the problem, which solved linear approximations of the original problem and maintained feasibility for the intermediate points. This method was augmented to include a quadratic model of the objective function. In addition, the feasibility requirement was relaxed to produce a third solution technique. Finally, the stability optimization problem was solved using a quadratic model without the feasibility requirement. Tests of all four methods were performed on three sample power systems. The systems included six, 14, and 118 bus examples. In all three cases, each of the four methods effected improvement in the stability margin, as measured by a variety of indicators. The infeasible linear solution provided the best results, based on runtime and the relative stability improvement. Also, the results showed that the additional quadratic approximation did not provide any measurable benefit to the procedure. Moreover, the methods that specified feasibility at each step were inferior compared to the

  5. B-52 stability augmentation system reliability

    Science.gov (United States)

    Bowling, T. C.; Key, L. W.

    1976-01-01

    The B-52 SAS (Stability Augmentation System) was developed and retrofitted to nearly 300 aircraft. It actively controls B-52 structural bending, provides improved yaw and pitch damping through sensors and electronic control channels, and puts complete reliance on hydraulic control power for rudder and elevators. The system has experienced over 300,000 flight hours and has exhibited service reliability comparable to the results of the reliability test program. Development experience points out numerous lessons with potential application in the mechanization and development of advanced technology control systems of high reliability.

  6. Power stability methods for parallel systems

    International Nuclear Information System (INIS)

    Wallach, Y.

    1988-01-01

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

  7. System Design Description PFP Thermal Stabilization

    International Nuclear Information System (INIS)

    RISENMAY, H.R.

    2000-01-01

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

  8. Minimally Invasive Posterior Stabilization Improved Ambulation and Pain Scores in Patients with Plasmacytomas and/or Metastases of the Spine

    Directory of Open Access Journals (Sweden)

    Joseph H. Schwab

    2011-01-01

    Full Text Available Background. The incidence of spine metastasis is expected to increase as the population ages, and so is the number of palliative spinal procedures. Minimally invasive procedures are attractive options in that they offer the theoretical advantage of less morbidity. Purpose. The purpose of our study was to evaluate whether minimally invasive posterior spinal instrumentation provided significant pain relief and improved function. Study Design. We compared pre- and postoperative pain scores as well as ambulatory status in a population of patients suffering from oncologic conditions in the spine. Patient Sample. A consecutive series of patients with spine tumors treated minimally invasively with stabilization were reviewed. Outcome Measures. Visual analog pain scale as well as pre- and postoperative ambulatory status were used as outcome measures. Methods. Twenty-four patients who underwent minimally invasive posterior spinal instrumentation for metastasis were retrospectively reviewed. Results. Seven (29% patients were unable to ambulate secondary to pain and instability prior to surgery. All patients were ambulating within 2 to 3 days after having surgery (=0.01. The mean visual analog scale value for the preoperative patients was 2.8, and the mean postoperative value was 1.0 (=0.001. Conclusion. Minimally invasive posterior spinal instrumentation significantly improved pain and ambulatory status in this series.

  9. Nonlinear physical systems spectral analysis, stability and bifurcations

    CERN Document Server

    Kirillov, Oleg N

    2013-01-01

    Bringing together 18 chapters written by leading experts in dynamical systems, operator theory, partial differential equations, and solid and fluid mechanics, this book presents state-of-the-art approaches to a wide spectrum of new and challenging stability problems.Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations focuses on problems of spectral analysis, stability and bifurcations arising in the nonlinear partial differential equations of modern physics. Bifurcations and stability of solitary waves, geometrical optics stability analysis in hydro- and magnetohydrodynam

  10. A robust motion estimation system for minimal invasive laparoscopy

    Science.gov (United States)

    Marcinczak, Jan Marek; von Öhsen, Udo; Grigat, Rolf-Rainer

    2012-02-01

    Laparoscopy is a reliable imaging method to examine the liver. However, due to the limited field of view, a lot of experience is required from the surgeon to interpret the observed anatomy. Reconstruction of organ surfaces provide valuable additional information to the surgeon for a reliable diagnosis. Without an additional external tracking system the structure can be recovered from feature correspondences between different frames. In laparoscopic images blurred frames, specular reflections and inhomogeneous illumination make feature tracking a challenging task. We propose an ego-motion estimation system for minimal invasive laparoscopy that can cope with specular reflection, inhomogeneous illumination and blurred frames. To obtain robust feature correspondence, the approach combines SIFT and specular reflection segmentation with a multi-frame tracking scheme. The calibrated five-point algorithm is used with the MSAC robust estimator to compute the motion of the endoscope from multi-frame correspondence. The algorithm is evaluated using endoscopic videos of a phantom. The small incisions and the rigid endoscope limit the motion in minimal invasive laparoscopy. These limitations are considered in our evaluation and are used to analyze the accuracy of pose estimation that can be achieved by our approach. The endoscope is moved by a robotic system and the ground truth motion is recorded. The evaluation on typical endoscopic motion gives precise results and demonstrates the practicability of the proposed pose estimation system.

  11. Heat shock protein 90β stabilizes focal adhesion kinase and enhances cell migration and invasion in breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Xiangyang [Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang, Jiangxi 330006 (China); Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Nanchang University, Nanchang, Jiangxi 330006 (China); State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, Jiangxi 330047 (China); Wang, Yao [Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang, Jiangxi 330006 (China); Liu, Chengmei [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, Jiangxi 330047 (China); Lu, Quqin [Department of Biostatistics and Epidemiology, School of Public Health, Nanchang University, Nanchang, Jiangxi 330006 (China); Liu, Tao [Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang, Jiangxi 330006 (China); Chen, Guoan [Department of Hematology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330006 (China); Rao, Hai [Department of Molecular Medicine, University of Texas Health Science Center, San Antonio, TX 78229 (United States); Luo, Shiwen, E-mail: shiwenluo@ncu.edu.cn [Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang, Jiangxi 330006 (China)

    2014-08-01

    Focal adhesion kinase (FAK) acts as a regulator of cellular signaling and may promote cell spreading, motility, invasion and survival in malignancy. Elevated expression and activity of FAK frequently correlate with tumor cell metastasis and poor prognosis in breast cancer. However, the mechanisms by which the turnover of FAK is regulated remain elusive. Here we report that heat shock protein 90β (HSP90β) interacts with FAK and the middle domain (amino acids 233–620) of HSP90β is mainly responsible for this interaction. Furthermore, we found that HSP90β regulates FAK stability since HSP90β inhibitor 17-AAG triggers FAK ubiquitylation and subsequent proteasome-dependent degradation. Moreover, disrupted FAK-HSP90β interaction induced by 17-AAG contributes to attenuation of tumor cell growth, migration, and invasion. Together, our results reveal how HSP90β regulates FAK stability and identifies a potential therapeutic strategy to breast cancer. - Highlights: • HSP90β protects FAK from degradation by the ubiquitin-proteasome pathway. • Inhibition of HSP90β or FAK attenuates tumorigenesis of breast cancer cells. • Genetic repression of HSP90β or FAK inhibits tumor cell migration and proliferation. • Inhibition of HSP90β or FAK interferes cell invasion and cytoskeleton.

  12. Heat shock protein 90β stabilizes focal adhesion kinase and enhances cell migration and invasion in breast cancer cells

    International Nuclear Information System (INIS)

    Xiong, Xiangyang; Wang, Yao; Liu, Chengmei; Lu, Quqin; Liu, Tao; Chen, Guoan; Rao, Hai; Luo, Shiwen

    2014-01-01

    Focal adhesion kinase (FAK) acts as a regulator of cellular signaling and may promote cell spreading, motility, invasion and survival in malignancy. Elevated expression and activity of FAK frequently correlate with tumor cell metastasis and poor prognosis in breast cancer. However, the mechanisms by which the turnover of FAK is regulated remain elusive. Here we report that heat shock protein 90β (HSP90β) interacts with FAK and the middle domain (amino acids 233–620) of HSP90β is mainly responsible for this interaction. Furthermore, we found that HSP90β regulates FAK stability since HSP90β inhibitor 17-AAG triggers FAK ubiquitylation and subsequent proteasome-dependent degradation. Moreover, disrupted FAK-HSP90β interaction induced by 17-AAG contributes to attenuation of tumor cell growth, migration, and invasion. Together, our results reveal how HSP90β regulates FAK stability and identifies a potential therapeutic strategy to breast cancer. - Highlights: • HSP90β protects FAK from degradation by the ubiquitin-proteasome pathway. • Inhibition of HSP90β or FAK attenuates tumorigenesis of breast cancer cells. • Genetic repression of HSP90β or FAK inhibits tumor cell migration and proliferation. • Inhibition of HSP90β or FAK interferes cell invasion and cytoskeleton

  13. Vibrations and stability of complex beam systems

    CERN Document Server

    Stojanović, Vladimir

    2015-01-01

     This book reports on solved problems concerning vibrations and stability of complex beam systems. The complexity of a system is considered from two points of view: the complexity originating from the nature of the structure, in the case of two or more elastically connected beams; and the complexity derived from the dynamic behavior of the system, in the case of a damaged single beam, resulting from the harm done to its simple structure. Furthermore, the book describes the analytical derivation of equations of two or more elastically connected beams, using four different theories (Euler, Rayleigh, Timoshenko and Reddy-Bickford). It also reports on a new, improved p-version of the finite element method for geometrically nonlinear vibrations. The new method provides more accurate approximations of solutions, while also allowing us to analyze geometrically nonlinear vibrations. The book describes the appearance of longitudinal vibrations of damaged clamped-clamped beams as a result of discontinuity (damage). It...

  14. Stability analysis of Centurion electric power system

    Energy Technology Data Exchange (ETDEWEB)

    Galu, Y.; Munda, J.L.; Jimoh, A.A. [Tshwane Univ. of Technology, Pretoria (South Africa)

    2008-07-01

    A Centurion electric power system was simulated. Data from a section of the Tshwane Municipality network in South Africa were used to evaluate the use of a power system stabilizer (PSS) and a flexible AC transmission system (FACTS) controller and a thyristor controlled series compensator (TCSC). The single-machine infinite bus (SMIB) power system model was used to validate the effectiveness of the systems under various disturbance scenarios. The system's synchronous generator was characterized as a higher order model. Thevenin's equivalent of the transmission network was used to reduce the single-machine infinite bus power system in relation to the reactance of the transformer, transmission line per circuit, and the impedance of the receiving end system. Three-phase faults were applied at the generator terminal busbar in order to evaluate the model's performance. The study demonstrated that use of the PSS and TCSC-based controllers provide an improved response in terms of both overshoot and settling time. 17 refs., 10 figs.

  15. Robust power system stabilizer design with H∞ theory

    OpenAIRE

    Marjaneh Farhoodi; MohammadTaghi HamidiBeheshti; Ali Nejati

    2007-01-01

    In this paper, the H∞ robust control technique is presented to design a power system stabilizer. First, the H∞ standard problem is expressed and then, the modeling and stability analysis of power systems are studied. Finally, a H∞ power system stabilizer is designed and the simulation results are discussed.

  16. Stability and response bounds of non-conservative linear systems

    DEFF Research Database (Denmark)

    Pommer, Christian

    2003-01-01

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

  17. Transient Stability Improvement in Multi-Machine System Using Power System Stabilizer (PSS) and Static Var Compensator (SVC)

    OpenAIRE

    Khoshnaw Khalid Hama Saleh; Ergun Ercelebi

    2015-01-01

    Increasingly complex modern power systems require stability, especially for transient and small disturbances. Transient stability plays a major role in stability during fault and large disturbance. This paper compares a power system stabilizer (PSS) and static Var compensator (SVC) to improve damping oscillation and enhance transient stability. The effectiveness of a PSS connected to the exciter and/or governor in damping electromechanical oscillations of isolated synchro...

  18. 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

  19. Performance and stability analysis of a photovoltaic power system

    Science.gov (United States)

    Merrill, W. C.; Blaha, R. J.; Pickrell, R. L.

    1978-01-01

    The performance and stability characteristics of a 10 kVA photovoltaic power system are studied using linear Bode analysis and a nonlinear analog simulation. Power conversion efficiencies, system stability, and system transient performance results are given for system operation at various levels of solar insolation. Additionally, system operation and the modeling of system components for the purpose of computer simulation are described.

  20. System specification for the plutonium stabilization and packaging system

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-07-01

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

  1. System specification for the plutonium stabilization and packaging system

    International Nuclear Information System (INIS)

    1996-01-01

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

  2. Stability Limits in Resonant Planetary Systems

    OpenAIRE

    Barnes, Rory; Greenberg, Richard

    2007-01-01

    The relationship between the boundaries for Hill and Lagrange stability in orbital element space is modified in the case of resonantly interacting planets. Hill stability requires the ordering of the planets to remain constant while Lagrange stability also requires all planets to remain bound to the central star. The Hill stability boundary is defined analytically, but no equations exist to define the Lagrange boundary, so we perform numerical experiments to estimate the location of this boun...

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

    Directory of Open Access Journals (Sweden)

    Tetiana Vasilyeva

    2016-10-01

    Full Text Available Intensification of financial development during last decade causes transformation of banking sector functioning. In particular, among the most significant changes over this period should be noted the next ones: convergence of financial market segments and appearance of cross-sector financial products, an increase of prevailing of financial sector in comparison with real economy and level of their interdependent, an intensification of crisis processes in financial and especially banking sector and a significant increase of the scale of the crisis consequences etc. thus, in such vulnerable conditions it is become very urgent to identify the relevant factors that can influence on the stability of banking sector, because its maintenance seems to be one of the most important preconditions of the stability of the national economy as a whole. Purpose of the article is to analyze key performance indicators of the Ukrainian banking system, clarify its main problems, identify relevant factors of the stability of the Ukrainian banking system and the character of their influence on the dependent variable. Realization of the mentioned above tasks was ensured by regression analysis (OLS regression. Analysis of key indicators that characterize current situation in the Ukrainian banking system found out the existence of numerous endogenous and exogenous problems, which, in turn, cause worsening most of analyzed indicators during 2013-2015. Unfavorable situation in Ukrainian banking system determined the necessity of identification of relevant factors of banking system stability to avoid transmission of financial shocks. According to the results of regression analysis on the stability of banking sector positively influence such factors as increase of interest margin to gross income ratio, reserves to assets ratio, number of branches, ratio of non-performing loans to total loans. Meanwhile, negative impact on stability of banking system has an increase of liquid

  4. Stability analysis of distributed order fractional chen system.

    Science.gov (United States)

    Aminikhah, H; Refahi Sheikhani, A; Rezazadeh, H

    2013-01-01

    We first investigate sufficient and necessary conditions of stability of nonlinear distributed order fractional system and then we generalize the integer-order Chen system into the distributed order fractional domain. Based on the asymptotic stability theory of nonlinear distributed order fractional systems, the stability of distributed order fractional Chen system is discussed. In addition, we have found that chaos exists in the double fractional order Chen system. Numerical solutions are used to verify the analytical results.

  5. Stability Analysis of Distributed Order Fractional Chen System

    Science.gov (United States)

    Aminikhah, H.; Refahi Sheikhani, A.; Rezazadeh, H.

    2013-01-01

    We first investigate sufficient and necessary conditions of stability of nonlinear distributed order fractional system and then we generalize the integer-order Chen system into the distributed order fractional domain. Based on the asymptotic stability theory of nonlinear distributed order fractional systems, the stability of distributed order fractional Chen system is discussed. In addition, we have found that chaos exists in the double fractional order Chen system. Numerical solutions are used to verify the analytical results. PMID:24489508

  6. COMPARISON OF DIFFERENT TECHNIQUES FOR DESIGN OF POWER SYSTEM STABILIZER

    OpenAIRE

    M. Ravindra Babu,; A. Ramulu; B. Durga Prasad,; Doradla. Prathap Hari Krishna,

    2011-01-01

    The major problem in power system operation is related to small signal instability caused by insufficient damping in the system. The most effective way of countering this instability is to use auxiliary controllers called power system stabilizers, to produce additional damping during low frequency oscillations in the system. Heffron-Phillip’s Model of a synchronous machine is commonly used in small signal stability analysis. Different techniques for designing of power system stabilizer is pro...

  7. Modeling invasive alien plant species in river systems : Interaction with native ecosystem engineers and effects on hydro-morphodynamic processes

    NARCIS (Netherlands)

    van Oorschot, M.; Kleinhans, M. G.; Geerling, G.W.; Egger, G.; Leuven, R.S.E.W.; Middelkoop, H.

    2017-01-01

    Invasive alien plant species negatively impact native plant communities by out-competing species or changing abiotic and biotic conditions in their introduced range. River systems are especially vulnerable to biological invasions, because waterways can function as invasion corridors. Understanding

  8. Analysis and assessment of STATCOM-based damping stabilizers for power system stability enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Abido, M.A. [Electrical Engineering Department, King Fahd University of Petroleum and Minerals, KFUPM Box Number 183, Dhahran 31261 (Saudi Arabia)

    2005-02-01

    Power system stability enhancement via STATCOM-based stabilizers is thoroughly investigated in this paper. This study presents a singular value decomposition (SVD)-based approach to assess and measure the controllability of the poorly damped electromechanical modes by STATCOM different control channels. The coordination among the proposed damping stabilizers and the STATCOM internal ac and dc voltage controllers has been taken into consideration. The design problem of STATCOM-based stabilizers is formulated as an optimization problem. For coordination purposes, a time domain-based multiobjective junction to improve the system stability as well as ac and dc voltage regulation is proposed. Then, a real-coded genetic algorithm (RCGA) is employed to search for optimal stabilizer parameters. This aims to enhance both rotor angle stability and voltage regulation of the power system. The proposed stabilizers are tested on a weakly connected power system with different disturbances and loading conditions. The nonlinear simulation results show the effectiveness and robustness of the proposed control schemes over a wide range of loading conditions. It is also observed that the proposed STATCOM-based damping stabilizers extend the critical clearing time (CCT) and enhance greatly the power system transient stability.

  9. Stability improvement of induction generator-based wind turbine systems

    DEFF Research Database (Denmark)

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

    2007-01-01

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

  10. System design document for the plutonium stabilization and packaging system

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-05-08

    The objective of this system is to stabilize and package plutonium metals and oxides of greater than 50% wt, as well as other selected isotopes, in accordance with the requirements for DOE standards for safe storage of these materials for 50 years. This document describes the highest level design information and user characteristics from an operational perspective. It provides guidance for developing procurement and installation specifications, interface requirements, and test plans.

  11. THE EFFECT OF GAS HYDRATES DISSOCIATION AND DRILLING FLUIDS INVASION UPON BOREHOLE STABILITY IN OCEANIC GAS HYDRATES-BEARING SEDIMENT

    Science.gov (United States)

    Ning, F.; Wu, N.; Jiang, G.; Zhang, L.

    2009-12-01

    Under the condition of over-pressure drilling, the solid-phase and liquid-phase in drilling fluids immediately penetrate into the oceanic gas hydrates-bearing sediment, which causes the water content surrounding the borehole to increase largely. At the same time, the hydrates surrounding borehole maybe quickly decompose into water and gas because of the rapid change of temperature and pressure. The drilling practices prove that this two factors may change the rock characteristics of wellbore, such as rock strength, pore pressure, resistivity, etc., and then affect the logging response and evaluation, wellbore stability and well safty. The invasion of filtrate can lower the angle of friction and weaken the cohesion of hydrates-bearing sediment,which is same to the effect of invading into conventional oil and gas formation on borehole mechnical properties. The difference is that temperature isn’t considered in the invasion process of conventional formations while in hydrates-bearing sediments, it is a factor that can not be ignored. Temperature changes can result in hydrates dissociating, which has a great effect on mechanical properties of borehole. With the application of numerical simulation method, we studied the changes of pore pressure and variation of water content in the gas hydrates-bearing sediment caused by drilling fluid invasion under pressure differential and gas hydrate dissociation under temperature differential and analyzed their influence on borehole stability.The result of simulation indicated that the temperature near borehole increased quickly and changed hardly any after 6 min later. About 1m away from the borehole, the temperature of formation wasn’t affected by the temperature change of borehole. At the place near borehole, as gas hydrate dissociated dramatically and drilling fluid invaded quickly, the pore pressure increased promptly. The degree of increase depends on the permeability and speed of temperature rise of formation around

  12. Stability of neutral type descriptor system with mixed delays

    International Nuclear Information System (INIS)

    Li Hong; Li Houbiao; Zhong Shouming

    2007-01-01

    In this paper, the stability problems of general neutral type descriptor system with mixed delays are considered. Some new delay-independent stability and robust stability criteria, which are simpler and less conservative than existing results, are derived in terms of the stability of a new operator I and linear matrix inequalities (LMIs). Therefore, criteria can be easily checked by utilizing the Matlab LMI toolbox

  13. Polynomial stabilization of some dissipative hyperbolic systems

    Czech Academy of Sciences Publication Activity Database

    Ammari, K.; Feireisl, Eduard; Nicaise, S.

    2014-01-01

    Roč. 34, č. 11 (2014), s. 4371-4388 ISSN 1078-0947 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : exponential stability * polynomial stability * observability inequality Subject RIV: BA - General Mathematics Impact factor: 0.826, year: 2014 http://www.aimsciences.org/journals/displayArticlesnew.jsp?paperID=9924

  14. Power system stability modelling, analysis and control

    CERN Document Server

    Sallam, Abdelhay A

    2015-01-01

    This book provides a comprehensive treatment of the subject from both a physical and mathematical perspective and covers a range of topics including modelling, computation of load flow in the transmission grid, stability analysis under both steady-state and disturbed conditions, and appropriate controls to enhance stability.

  15. Non-invasive system for monitoring of the manufacturing equipment

    Science.gov (United States)

    Mazăre, A. G.; Belu, N.; Ionescu, L. M.; Rachieru, N.; Misztal, A.

    2017-08-01

    The automotive industry is one of the most important industries in the world that concerns the economy and the world culture. High demand has resulted in increasing of the pressure on the production lines. In conclusion, it is required more careful in monitoring of the production equipment not only for maintenance but also for staff safety and to increase the quality of production. In this paper, we propose a solution for non-invasive monitoring of the industrial equipment operation by measuring the current consumption on energy supply lines. Thus, it is determined the utilization schedule of the equipment and operation mode. Based on these measurements, it’s built an activity report for that equipment, available to the quality management and maintenance team. The solution consists of the current measuring equipment, with self-harvesting capabilities and radio transceiver, and an embedded system which run a server. The current measuring equipment will transmit data about consumption of each energy supply network line where is placed the industrial equipment. So, we have an internal measuring radio network. The embedded system will collect data for the equipment and put in a local data base and it will provide via an intranet application. The entire system not requires any supplementary energy supply and interventions in the factory infrastructure. It is experimented in a company from the automotive industries.

  16. A Gimbal-Stabilized Compact Hyperspectral Imaging System, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The Gimbal-stabilized Compact Hyperspectral Imaging System (GCHIS) fully integrates multi-sensor spectral imaging, stereovision, GPS and inertial measurement,...

  17. A Gimbal-Stabilized Compact Hyperspectral Imaging System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Gimbal-stabilized Compact Hyperspectral Imaging System (GCHIS) fully integrates multi-sensor spectral imaging, stereovision, GPS and inertial measurement,...

  18. Stabilization of a class of sandwich systems via state feedback

    NARCIS (Netherlands)

    Wang, Xu; Stoorvogel, Antonie Arij; Saberi, Ali; Grip, H°avard Fjær; Roy, Sandip; Sannuti, Peddapullaiah

    We consider the problem of state-feedback stabilization for a class of sandwich systems, consisting of two linear systems connected in cascade via a saturation. In particular, we present design methodologies for constructing semiglobally and globally stabilizing controllers for such systems when the

  19. Absolute Stability of Discrete-Time Systems with Delay

    Directory of Open Access Journals (Sweden)

    Medina Rigoberto

    2008-01-01

    Full Text Available We investigate the stability of nonlinear nonautonomous discrete-time systems with delaying arguments, whose linear part has slowly varying coefficients, and the nonlinear part has linear majorants. Based on the "freezing" technique to discrete-time systems, we derive explicit conditions for the absolute stability of the zero solution of such systems.

  20. 76 FR 75860 - National Forest System Invasive Species Management Policy

    Science.gov (United States)

    2011-12-05

    ... and implementing invasive species management activities as a tool for achieving sustainable management..., controlling, or eradicating invasive species assists in the recovery of the area's resilience and the capacity... decisionmaking. The core SDM concepts and steps to better decisionmaking are useful across all types of decisions...

  1. Stability of miniature electromagnetic tracking systems

    International Nuclear Information System (INIS)

    Schicho, Kurt; Figl, Michael; Donat, Markus; Birkfellner, Wolfgang; Seemann, Rudolf; Wagner, Arne; Bergmann, Helmar; Ewers, Rolf

    2005-01-01

    This study aims at a comparative evaluation of two recently introduced electromagnetic tracking systems under reproducible simulated operating-room (OR) conditions: the recently launched Medtronic StealthStation TM Treon-EM TM and the NDI Aurora TM . We investigate if and to what extent these systems provide improved performance and stability in the presence of surgical instruments as possible sources of distortions compared with earlier reports on electromagnetic tracking technology. To investigate possible distortions under pseudo-realistic OR conditions, a large Langenbeck hook, a dental drill with its handle and an ultrasonic (US) scanhead are fixed on a special measurement rack at variable distances from the navigation sensor. The position measurements made by the Treon-EM TM were least affected by the presence of the instruments. The lengths of the mean deviation vectors were 0.21 mm for the Langenbeck hook, 0.23 mm for the drill with handle and 0.56 mm for the US scanhead. The Aurora TM was influenced by the three sources of distortion to a higher degree. A mean deviation vector of 1.44 mm length was observed in the vicinity of the Langenbeck hook, 0.53 mm length with the drill and 2.37 mm due to the US scanhead. The maximum of the root mean squared error (RMSE) for all coordinates in the presence of the Langenbeck hook was 0.3 mm for the Treon TM and 2.1 mm for the Aurora TM ; the drill caused a maximum RMSE of 0.2 mm with the Treon TM and 1.2 mm with the Aurora TM . In the presence of the US scanhead, the maximum RMSE was 1.4 mm for the Treon TM and 5.1 mm for the Aurora TM . The new generation of electromagnetic tracking systems has significantly improved compared to common systems that were available in the middle of the 1990s and has reached a high level of technical development. We conclude that, in general, both systems are suitable for routine clinical application

  2. Further Results on Finite-Time Partial Stability and Stabilization. Applications to Nonlinear Control Systems

    International Nuclear Information System (INIS)

    Jammazi, Chaker

    2009-01-01

    The paper gives Lyapunov type sufficient conditions for partial finite-time and asymptotic stability in which some state variables converge to zero while the rest converge to constant values that possibly depend on the initial conditions. The paper then presents partially asymptotically stabilizing controllers for many nonlinear control systems for which continuous asymptotically stabilizing (in the usual sense) controllers are known not to exist.

  3. Advanced signal processing theory and implementation for sonar, radar, and non-invasive medical diagnostic systems

    CERN Document Server

    Stergiopoulos, Stergios

    2009-01-01

    Integrates topics of signal processing from sonar, radar, and medical system technologies by identifying their concept similarities. This book covers non-invasive medical diagnostic system applications, including intracranial ultrasound, a technology that attempts to address non-invasive detection on brain injuries and stroke.

  4. Stability improvement of induction generator-based wind turbine systems

    DEFF Research Database (Denmark)

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

    2007-01-01

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

  5. Minimal invasive stabilization of osteoporotic vertebral compression fractures. Methods and preinterventional diagnostics; Minimal-invasive Stabilisierung osteoporotischer Wirbelkoerpereinbrueche. Methodik und praeinterventionelle Diagnostik

    Energy Technology Data Exchange (ETDEWEB)

    Grohs, J.G.; Krepler, P. [Orthopaedische Klinik, Universitaet Wien (Austria)

    2004-03-01

    Minimal invasive stabilizations represent a new alternative for the treatment of osteoporotic compression fractures. Vertebroplasty and balloon kyphoplasty are two methods to enhance the strength of osteoporotic vertebral bodies by the means of cement application. Vertebroplasty is the older and technically easier method. The balloon kyphoplasty is the newer and more expensive method which does not only improve pain but also restores the sagittal profile of the spine. By balloon kyphoplasty the height of 101 fractured vertebral bodies could be increased up to 90% and the wedge decreased from 12 to 7 degrees. Pain was reduced from 7,2 to 2,5 points. The Oswestry disability index decreased from 60 to 26 points. This effects persisted over a period of two years. Cement leakage occurred in only 2% of vertebral bodies. Fractures of adjacent vertebral bodies were found in 11%. Good preinterventional diagnostics and intraoperative imaging are necessary to make the balloon kyphoplasty a successful application. (orig.) [German] Minimal-invasive Stabilisierungen stellen eine Alternative zur bisherigen Behandlung osteoporotischer Wirbelfrakturen dar. Die Vertebroplastie und die Ballonkyphoplastik sind 2 Verfahren, um die Festigkeit der Wirbelkoerper nach osteoporotischen Kompressionsfrakturen durch Einbringen von Knochenzement wieder herzustellen. Die Vertebroplastie ist die aeltere, technisch einfachere und kostenguenstigere Technik, geht allerdings regelmaessig mit Zementaustritt einher. Die Ballonkyphoplastik ist die neuere kostenintensivere Technologie, mit der abgesehen von der Schmerzreduktion auch die Wiederherstellung des sagittalen Profils der Wirbelsaeule angestrebt werden kann. Mit der Ballonkyphoplastik konnten bei 101 frakturierten Wirbelkoerpern die Hoehe auf fast 90% des Sollwertes angehoben und die lokale Kyphose von 12 auf 7 vermindert werden. Die Schmerzen wurden - gemessen anhand einer 10-teiligen Skala - von 7,2 auf 2,5 reduziert. Der Oswestry disability

  6. Cliff stability assessment using electrical resistivity tomography at the historic WWII D-Day invasion site, Pointe du Hoc, France

    Science.gov (United States)

    Everett, M. E.; Udphuay, S.; Warden, R.

    2007-05-01

    The 1944 D-Day invasion site at Pointe du Hoc, Normandy, France is an important WWII battlefield and cultural resource but is at risk from chalk cliff collapse. The American Battle Monuments Commission tasked us to evaluate the geohazard to the observation post and other cliff-side buildings of historical significance. Geophysical multi-electrode resistivity profiling is used to study cliff stability and the condition of the observation- post foundations. Preliminary 2-D geological interpretations are provided of individual profiles. The copious steel, concrete and void spaces at the site renders hydrogeological interpretation challenging but tractable. The cliff face appears to be relatively intact and well-drained. Several routes taken by groundwater into fractures within the chalk were identified mainly on the western side of the site. The eastern side is drier and somewhat sheltered from the Atlantic storms but may contain large void spaces that could efficiently transmit groundwater flow during heavy precipitation events, thereby imperiling the major antiaircraft gun emplacement occupied by Col. Rudder in the early days of the Allied invasion. The forward German observation post perched close to the sea stack, which now hosts the U.S. Ranger memorial, may be moving with the soil and not securely anchored to bedrock. A complex failure mechanism is identified as a combination of groundwater dissolution of the fractured chalk and sea wave attack at the cliff base.

  7. Finite-Time Stability and Stabilization of Nonlinear Quadratic Systems with Jumps

    Directory of Open Access Journals (Sweden)

    Minsong Zhang

    2014-01-01

    Full Text Available This paper investigates the problems of finite-time stability and finite-time stabilization for nonlinear quadratic systems with jumps. The jump time sequences here are assumed to satisfy some given constraints. Based on Lyapunov function and a particular presentation of the quadratic terms, sufficient conditions for finite-time stability and finite-time stabilization are developed to a set containing bilinear matrix inequalities (BLIMs and linear matrix inequalities (LMIs. Numerical examples are given to illustrate the effectiveness of the proposed methodology.

  8. System identification on two-phase flow stability

    International Nuclear Information System (INIS)

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

    1996-01-01

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

  9. Learning and Understanding System Stability Using Illustrative Dynamic Texture Examples

    Science.gov (United States)

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

    2014-01-01

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

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

    Indian Academy of Sciences (India)

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

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

    Indian Academy of Sciences (India)

    The system achieves good voltage stabilization, eliminates ground loops and noise interference. It incorporates a correcting circuit for compensating the mains frequency variations in the GVM amplifier circuit. The present system has two modes of operation namely GVM control mode and slit control mode. A voltage stability ...

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

    Science.gov (United States)

    Milanović, Jovica V

    2017-08-13

    Future power systems will be significantly different compared with their present states. They will be characterized by an unprecedented mix of a wide range of electricity generation and transmission technologies, as well as responsive and highly flexible demand and storage devices with significant temporal and spatial uncertainty. The importance of probabilistic approaches towards power system stability analysis, as a subsection of power system studies routinely carried out by power system operators, has been highlighted in previous research. However, it may not be feasible (or even possible) to accurately model all of the uncertainties that exist within a power system. This paper describes for the first time an integral approach to probabilistic stability analysis of power systems, including small and large angular stability and frequency stability. It provides guidance for handling uncertainties in power system stability studies and some illustrative examples of the most recent results of probabilistic stability analysis of uncertain power systems.This article is part of the themed issue 'Energy management: flexibility, risk and optimization'. © 2017 The Author(s).

  13. Stability and Relative Stability of Linear Systems with Many Constant Time Delays. Ph.D. Thesis

    Science.gov (United States)

    Barker, Larry Keith

    1976-01-01

    A method of determining the stability of linear systems with many constant time delays is developed. This technique, an extension of the tau-decomposition method, is used to examine not only the stability but also the relative stability of retarded systems with many delays and a class of neutral equations with one delay. Analytical equations are derived for partitioning the delay space of a retarded system with two time delays. The stability of the system in each of the regions defined by the partitioning curves in the parameter plane is determined using the extended tau-decomposition method. In addition, relative stability boundaries are defined using the extended tau-decompositon method in association with parameter plane techniques. Several applications of the extended tau-decomposition method are presented and compared with stability results obtained from other analyses. In all cases the results obtained using the method outlined herein coincide with and extend those of previous investigations. The extended tau-decomposition method applied to systems with time delays requires less computational effort and yields more complete stability analyses than previous techniques.

  14. Transient Stability Enhancement of the Power System with Wind Generation

    Directory of Open Access Journals (Sweden)

    Ashwani Kumar Chandel

    2011-08-01

    Full Text Available Transient stability analysis of a power system with wind generation has been addressed in this paper. The effects of automatic voltage regulators, power system stabilizers, and static synchronous compensators on transient stability of a power system are investigated. Various simulation results show that addition of power system stabilizer and static synchronous compensators reduce the rotor angle oscillations. However, the static synchronous compensator shows better damping characteristics and improves the stability of the wind integrated system. It has been established that the static synchronous compensator damps out the speed oscillations in the shaft of the constant speed wind turbine. A transient impact index has been proposed to prove that the static compensator damps out the rotor oscillations.

  15. Multidrug efflux systems play an important role in the invasiveness of Pseudomonas aeruginosa.

    Science.gov (United States)

    Hirakata, Yoichi; Srikumar, Ramakrishnan; Poole, Keith; Gotoh, Naomasa; Suematsu, Takashi; Kohno, Shigeru; Kamihira, Shimeru; Hancock, Robert E W; Speert, David P

    2002-07-01

    Pseudomonas aeruginosa is an important opportunistic human pathogen. Certain strains can transmigrate across epithelial cells, and their invasive phenotype is correlated with capacity to cause invasive human disease and fatal septicemia in mice. Four multidrug efflux systems have been described in P. aeruginosa, however, their contribution to virulence is unclear. To clarify the role of efflux systems in invasiveness, P. aeruginosa PAO1 wild-type (WT) and its efflux mutants were evaluated in a Madin-Darby canine kidney (MDCK) epithelial cell monolayer system and in a murine model of endogenous septicemia. All efflux mutants except a deltamexCD-oprJ deletion demonstrated significantly reduced invasiveness compared with WT. In particular, a deltamexAB-oprM deletion strain was compromised in its capacity to invade or transmigrate across MDCK cells, and could not kill mice, in contrast to WT which was highly invasive (P efflux system exports virulence determinants that contribute to bacterial virulence.

  16. Toluene stability Space Station Rankine power system

    Science.gov (United States)

    Havens, V. N.; Ragaller, D. R.; Sibert, L.; Miller, D.

    1987-01-01

    A dynamic test loop is designed to evaluate the thermal stability of an organic Rankine cycle working fluid, toluene, for potential application to the Space Station power conversion unit. Samples of the noncondensible gases and the liquid toluene were taken periodically during the 3410 hour test at 750 F peak temperature. The results obtained from the toluene stability loop verify that toluene degradation will not lead to a loss of performance over the 30-year Space Station mission life requirement. The identity of the degradation products and the low rates of formation were as expected from toluene capsule test data.

  17. Advances in power system modelling, control and stability analysis

    CERN Document Server

    Milano, Federico

    2016-01-01

    Advances in Power System Modelling, Control and Stability Analysis captures the variety of new methodologies and technologies that are changing the way modern electric power systems are modelled, simulated and operated.

  18. Stabilization of bilinear systems by linear state feedback and the estimation of its stability region

    International Nuclear Information System (INIS)

    Yasuda, Kazunori; Hirai, Kazumasa

    1980-01-01

    This paper is concerned with the stabilization problem for bilinear systems by means of a linear state feedback. A bilinear system described by the equation x*(t) (*: radical) = Ax(t) + Σ(i -- r) u sub(i)(t)Bx(t) + Cu(t) is stabilizable by using a linear state feedback u = K sup(T)x(t), if the pair (A, C) is controllable; however, it is not generally stabilizable in the large. We, in this paper, give a sufficient condition under which the bilinear system is stabilizable in the large, and estimate quantitatively the extent of a stability region around the equilibrium state in the case that the system is not stabilizable in the large. Moreover, the behavior of the solution whose initial state is in the estimated stability region is considered. It is also shown that the stability region derived here is evaluated on a ground tighter than the previous ones. (author)

  19. Wind energy systems solutions for power quality and stabilization

    CERN Document Server

    Ali, Mohd Hasan

    2012-01-01

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

  20. Small invasive colon cancer with systemic metastasis: A case report

    Directory of Open Access Journals (Sweden)

    Sakamoto Taku

    2011-05-01

    Full Text Available ABSTRACT Background Recently, especially in Japan, several researchers have suggested that colorectal cancer can develop not only through an adenoma-carcinoma sequence but also from normal mucosa via a de novo pathway, and that these de novo cancers have more aggressive malignant potential. We report a case of aggressive colon cancer resulting in systemic metastasis despite small tumour size. Case Presentation A 35-year-old woman presented at the referring hospital with swelling of the left cervical lymph node. Biopsy of the lymph node revealed metastatic adenocarcinoma; however, CT scan and mammography were unable to identify the site of the primary lesion. She was diagnosed with unknown primary cancer and referred to our hospital for further examination. Immunohistochemical reevaluation showed the cervical lymph node biopsy specimen to be positive for CDX2 and CK20 and negative for CK7 expression, leading us to suspect the presence of a primary colorectal cancer. We performed a total colonoscopy, and detected a small protruding lesion in the transverse colon. The tumour was only 12 mm in diameter, with a central depressed component and a severely thickened stalk, which suggested direct cancer invasion of the deep submucosa. We concluded that this lesion was the site of origin of the metastasis despite the small tumour size, and performed diagnostic endoscopic mucosal resection. The lesion was found to have an intramucosal cancer component, demonstrating that this lesion represented primary colon cancer. The patient was referred to the gastrointestinal oncology division for systemic chemotherapy. Conclusions In this case, immunohistochemical findings strongly suggested the existence of a colorectal cancer. The non-polypoid gross appearance of the tumour suggested that it can originate de novo , thus providing a valuable case in support of the aggressive malignant potential of a de novo colorectal cancer pathway.

  1. Power System Transient Stability Based on Data Mining Theory

    Science.gov (United States)

    Cui, Zhen; Shi, Jia; Wu, Runsheng; Lu, Dan; Cui, Mingde

    2018-01-01

    In order to study the stability of power system, a power system transient stability based on data mining theory is designed. By introducing association rules analysis in data mining theory, an association classification method for transient stability assessment is presented. A mathematical model of transient stability assessment based on data mining technology is established. Meanwhile, combining rule reasoning with classification prediction, the method of association classification is proposed to perform transient stability assessment. The transient stability index is used to identify the samples that cannot be correctly classified in association classification. Then, according to the critical stability of each sample, the time domain simulation method is used to determine the state, so as to ensure the accuracy of the final results. The results show that this stability assessment system can improve the speed of operation under the premise that the analysis result is completely correct, and the improved algorithm can find out the inherent relation between the change of power system operation mode and the change of transient stability degree.

  2. Solving the stability-accuracy-diversity dilemma of recommender systems

    Science.gov (United States)

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

    2017-02-01

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

  3. Minimally Invasive Spine Metastatic Tumor Resection and Stabilization: New Technology Yield Improved Outcome

    Directory of Open Access Journals (Sweden)

    Ran Harel

    2015-01-01

    Full Text Available Spinal metastases compressing the spinal cord are a medical emergency and should be operated on if possible; however, patients’ medical condition is often poor and surgical complications are common. Minimizing surgical extant, operative time, and blood loss can potentially reduce postoperative complications. This is a retrospective study describing the patients operated on in our department utilizing a minimally invasive surgery (MIS approach to decompress and instrument the spine from November 2013 to November 2014. Five patients were operated on for thoracic or lumbar metastases. In all cases a unilateral decompression with expandable tubular retractor was followed by instrumentation of one level above and below the index level and additional screw at the index level contralateral to the decompression side. Cannulated fenestrated screws were used (Longitude FNS and cement was injected to increase pullout resistance. Mean operative time was 134 minutes and estimated blood loss was minimal in all cases. Improvement was noticeable in neurological status, function, and pain scores. No complications were observed. Technological improvements in spinal instruments facilitate shorter and safer surgeries in oncologic patient population and thus reduce the complication rate. These technologies improve patients’ quality of life and enable the treatment of patients with comorbidities.

  4. Research on Design of MUH Attitude Stability Augmentation Control System

    Science.gov (United States)

    Fan, Shigang

    2017-09-01

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

  5. Power system stabilizers based on modern control techniques

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-12-31

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

  6. 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.

  7. Stability Limits in Extra-solar Planetary Systems

    OpenAIRE

    Barnes, Rory; Greenberg, Richard

    2006-01-01

    Two types of stability boundaries exist for any planetary system consisting of one star and two planets. Lagrange stability requires that the planets remain bound to the star, conserves the ordering of the distance from the star, and limits the variations of orbital elements like semi-major axis and eccentricity. Hill stability only requires that the ordering of the planets remain constant; the outer planet may escape to infinity. A simple formula defines a region in orbital element space tha...

  8. Cooperative prevention systems to protect rangelands from the spread of invasive plants

    Science.gov (United States)

    Invasive plants continue to spread and impact rangelands in the western United States. Fortunately, many rangeland ecosystems still remain invasive weed-free.Cooperative prevention systems can safeguard these remaining areas. Local-level weed prevention areas (WPAs) prioritize prevention in the larg...

  9. Invasive fungal infections in Argentine patients with systemic lupus erythematosus.

    Science.gov (United States)

    Vinicki, J P; Catalan Pellet, S; Pappalardo, C; Cruzat, V C; Spinetto, M A; Dubinsky, D; Tiraboschi, I N; Laborde, H A; Nasswetter, G

    2013-08-01

    Infections are the leading cause of morbidity and mortality in patients with systemic lupus erythematosus (SLE). Invasive fungal infections (IFI) comprise a group of diseases caused by Cryptococcus, Histoplasma, Aspergillus and Candida. Few studies of IFI have been published in patients with SLE and associated factors have not been completely defined. The objectives of this paper are to estimate the frequency of IFI in admitted patients with SLE in our hospital, to determine the risk factors associated with IFI in our patients with SLE, and to compare IFI group with a control group (SLE without IFI). The medical charts of patients with IFI (EORTC/MSG, 2008) and SLE (ACR, 1997) admitted to our hospital from June 2001 until June 2012 were reviewed. To identify factors associated with IFI, we developed a case-control study (SLE + IFI vs SLE alone) in a one to three ratio adjusted for sex and age and hospitalization for other reasons. Comparison was made of demographic characteristics, duration of disease and disease activity previous to IFI diagnosis, especially three months before fungal infection. We defined severe activity as SLEDAI ≥ 8. Infection by fungi of the genus Candida was considered only in its disseminated form. Ten cases of IFI were identified in 208 patients with SLE admitted between June 2001 and June 2012. We included 40 patients with SLE (10 with IFI and 30 controls). Of the SLE-IFI patients, eight were women and the average age was 27.5 years (range, 19-42 years). Fungal isolation: eight Cryptococcus neoformans, one Histoplasma capsulatum and one Candida albicans. Sites affected: five in peripheral blood, five in central nervous system (CNS), four in skin/soft tissue and one in pleura. Mortality was 40% (p = 0.002), with Cryptococcus neoformans being the most common fungus. The SLE disease activity was severe in 70% of infected patients and no significant difference with the control group was found (p = 0.195). We also found no

  10. A Quantification Index for Power Systems Transient Stability

    Directory of Open Access Journals (Sweden)

    Shengen Chen

    2017-07-01

    Full Text Available In order to assess the reliability of power systems, transient stability simulations must be conducted in addition to steady state study. The transient stability component of reliability studies usually involves extensive simulations generating large amounts of data to be analyzed. Conventional stability analysis relies on a visual examination of selected simulation data plots to classify the severity of disturbances. This conventional examination, which aims to compare the simulations results to established performance criteria, is not comprehensive, is time consuming and prone to subjective interpretation. This paper presents a quantification method for power system performance evaluation. It applies a range of criteria such as rotor angle separation, loss of source, damping, and voltage sag directly to the simulation data files to achieve a more efficient and objective stability assessment. By using stability modules, the proposed method evaluates the performance of every fault location, numerically, by providing a local stability index, as well as an overall global stability index. The method also provides an evaluation of dispatches and their impacts on system stability. The IEEE 39-bus test system and the Northeast Interconnection Power System were used to show the results of this method. This method will free engineers from tedious, time-consuming and error-susceptible offline visual analysis and yield significantly quantified results.

  11. Mobile Phenotyping System Using an Aeromotively Stabilized Cable-Driven Robot

    Science.gov (United States)

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

    2017-12-01

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

  12. Review of Power System Stability with High Wind Power Penetration

    DEFF Research Database (Denmark)

    Hu, Rui; Hu, Weihao; Chen, Zhe

    2015-01-01

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

  13. Stabilization of Neutral Systems with Saturating Actuators

    Directory of Open Access Journals (Sweden)

    F. El Haoussi

    2012-01-01

    to determine stabilizing state-feedback controllers with large domain of attraction, expressed as linear matrix inequalities, readily implementable using available numerical tools and with tuning parameters that make possible to select the most adequate solution. These conditions are derived by using a Lyapunov-Krasovskii functional on the vertices of the polytopic description of the actuator saturations. Numerical examples demonstrate the effectiveness of the proposed technique.

  14. Stabilization of the field of a superconducting magnetic system

    International Nuclear Information System (INIS)

    Sukhoj, V.V.; Kurochkin, V.I.; Laptienko, A.Ya.; Timoshenko, A.O.

    1981-01-01

    A way of magnetic field stabilization of short circuited superconducting system is considered theoretically. Removable field instability is caused by resistance of circuits windings in places of conductor joints or by the presence of wive defects. An equation is obtained describing the stabilization condition which connects electrical and geometrical parameters of circuits. The cases of this equation solutions by means of geometry choice or choice of resistance value of one of the circuits are considered. Field stability dependence on the accuracy of stabilization condition satisfaction is studied. Three time scales are introduced, which characterize the system operation without the deterioration of field homogeneity and stability as well as without the critical current excess in the circuit state mostly close to a critical one. Numerical calculations for concrete two- and three-circuit systems are presented [ru

  15. Stability analysis of linear switching systems with time delays

    International Nuclear Information System (INIS)

    Li Ping; Zhong Shouming; Cui Jinzhong

    2009-01-01

    The issue of stability analysis of linear switching system with discrete and distributed time delays is studied in this paper. An appropriate switching rule is applied to guarantee the stability of the whole switching system. Our results use a Riccati-type Lyapunov functional under a condition on the time delay. So, switching systems with mixed delays are developed. A numerical example is given to illustrate the effectiveness of our results.

  16. Decentralized linear quadratic power system stabilizers for multi ...

    Indian Academy of Sciences (India)

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

  17. New Results of Global Exponential Stabilization for BLDCMs System

    Directory of Open Access Journals (Sweden)

    Fengxia Tian

    2015-01-01

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

  18. Decentralized linear quadratic power system stabilizers for multi ...

    Indian Academy of Sciences (India)

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

  19. Stability and Stabilization of Networked Control System with Forward and Backward Random Time Delays

    Directory of Open Access Journals (Sweden)

    Ye-Guo Sun

    2012-01-01

    Full Text Available This paper deals with the problem of stabilization for a class of networked control systems (NCSs with random time delay via the state feedback control. Both sensor-to-controller and controller-to-actuator delays are modeled as Markov processes, and the resulting closed-loop system is modeled as a Markovian jump linear system (MJLS. Based on Lyapunov stability theorem combined with Razumikhin-based technique, a new delay-dependent stochastic stability criterion in terms of bilinear matrix inequalities (BMIs for the system is derived. A state feedback controller that makes the closed-loop system stochastically stable is designed, which can be solved by the proposed algorithm. Simulations are included to demonstrate the theoretical result.

  20. Electrostatic stabilizer for a passive magnetic bearing system

    Science.gov (United States)

    Post, Richard F.

    2015-11-24

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

  1. On the stability of some systems of exponential difference equations

    Directory of Open Access Journals (Sweden)

    N. Psarros

    2018-01-01

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

  2. Frequency Stability Improvement of Low Inertia Systems Using Synchronous Condensers

    DEFF Research Database (Denmark)

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

    2016-01-01

    of converter interfaced components (wind turbine, HVDC, and Photovoltaic) may have negative effects on the stability of the power system. These components do not have enough inertia response to control frequency excursion, so the power grid can depend on few synchronous machines for frequency regulation...... turbine penetration, governor responsibility of synchronous generators, and disturbance are simulated to examine the impact of highlevel renewable energy integration on the system frequency characteristics. The effect of synchronous condensers for the frequency stability enhancement is investigated....... It can be concluded from the comparative simulation results that synchronous condenser demonstrates a satisfactory performance for improving the system frequency stability....

  3. Computation of robustly stabilizing PID controllers for interval systems.

    Science.gov (United States)

    Matušů, Radek; Prokop, Roman

    2016-01-01

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

  4. 76 FR 32135 - National Forest System Invasive Species Management Policy

    Science.gov (United States)

    2011-06-03

    ... management activities as a tool for achieving sustainable management and providing a broad range of ecosystem... effectiveness of treatments. Preventing, controlling, or eradicating invasive species assists in the recovery of... decision making are useful across all types of decisions: from individuals making minor decisions to...

  5. Stability of the Kepler-11 system and its origin

    Energy Technology Data Exchange (ETDEWEB)

    Mahajan, Nikhil; Wu, Yanqin [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada)

    2014-11-01

    A significant fraction of Kepler systems are closely packed, largely coplanar, and circular. We study the stability of a six-planet system, Kepler-11, to gain insights on the dynamics and formation history of such systems. Using a technique called 'frequency maps' as fast indicators of long-term stability, we explore the stability of the Kepler-11 system by analyzing the neighborhood space around its orbital parameters. Frequency maps provide a visual representation of chaos and stability, and their dependence on orbital parameters. We find that the current system is stable, but lies within a few percent of several dynamically dangerous two-body mean-motion resonances. Planet eccentricities are restricted below a small value, ∼0.04, for long-term stability, but planet masses can be more than twice their reported values (thus allowing for the possibility of mass loss by past photoevaporation). Based on our frequency maps, we speculate on the origin of instability in closely packed systems. We then proceed to investigate how the system could have been assembled. The stability constraints on Kepler-11 (mainly eccentricity constraints) suggest that if the system were assembled in situ, a dissipation mechanism must have been at work to neutralize the eccentricity excitation. On the other hand, if migration was responsible for assembling the planets, there has to be little differential migration among the planets to avoid them either getting trapped into mean motion resonances, or crashing into each other.

  6. Estimation of multiply digital process control system extractive distillation stability

    Directory of Open Access Journals (Sweden)

    V. S. Kudryashov

    2016-01-01

    Full Text Available An approach to stability analysis of digital control systems associated non-stationary object on the example of the rectification process. Object modeling with cross-connections and the control scheme of the described system, discrete transfer functions in the shift operators. The equations of connection for each output of the closed-loop system. To solve this problem developed an algorithm for estimating the margin of stability of multivariable digital control systems based on the discrete root criterion, comprising the following main stages: obtaining of the characteristic polynomial of the closed-loop system for each output; computation of eigenvalues of the system matrix in the state space to determine roots of the characteristic equation and the stability of the system; determination of the stability and margin of stability by the deviation of maximum module of the root from the boundary of the high variability. To obtain the characteristic polynomial of a as discrete models of controllers and channels of IP object-use the transfer function of the first order with transport delay. The simulation was performed at different parameters of the control object, which is characterized by a stable and an unstable state of the system. VA-den analysis of the numerical values of the roots and character of their location on the complex plane, which to you-water that the system is stable or unstable. To confirm the obtained results were calculated and presented dynamic characteristics of the closed-loop system under different conditions, which confirm the initial assessment, the root criterion. To determine the factor stability of multivariable digital systems is proposed to use the deviation of the maximum root of the characteristic equation from the stability boundary. The obtained results apply to the class of symmetric multivariable control objects. The approach to assessing the sustainability of multivariable system regulation can be effectively

  7. Power system small signal stability analysis and control

    CERN Document Server

    Mondal, Debasish; Sengupta, Aparajita

    2014-01-01

    Power System Small Signal Stability Analysis and Control presents a detailed analysis of the problem of severe outages due to the sustained growth of small signal oscillations in modern interconnected power systems. The ever-expanding nature of power systems and the rapid upgrade to smart grid technologies call for the implementation of robust and optimal controls. Power systems that are forced to operate close to their stability limit have resulted in the use of control devices by utility companies to improve the performance of the transmission system against commonly occurring power system

  8. Earth System Stability Through Geologic Time

    Science.gov (United States)

    Rothman, D.; Bowring, S. A.

    2015-12-01

    Five times in the past 500 million years, mass extinctions haveresulted in the loss of greater than three-fourths of living species.Each of these events is associated with significant environmentalchange recorded in the carbon-isotopic composition of sedimentaryrocks. There are also many such environmental events in the geologicrecord that are not associated with mass extinctions. What makes themdifferent? Two factors appear important: the size of theenvironmental perturbation, and the time scale over which it occurs.We show that the natural perturbations of Earth's carbon cycle during thepast 500 million years exhibit a characteristic rate of change overtwo orders of magnitude in time scale. This characteristic rate isconsistent with the maximum rate that limits quasistatic (i.e., nearsteady-state) evolution of the carbon cycle. We identify this rate withmarginal stability, and show that mass extinctions occur on the fast,unstable side of the stability boundary. These results suggest thatthe great extinction events of the geologic past, and potentially a"sixth extinction" associated with modern environmental change, arecharacterized by common mechanisms of instability.

  9. Safety benefits of stability control systems for tractor-semitrailers.

    Science.gov (United States)

    2009-10-01

    This study was conducted by the University of Michigan Transportation Research Institute : (UMTRI) under a Cooperative Agreement between NHTSA and Meritor WABCO to examine : the performance of electronic stability control (ESC) systems, and roll stab...

  10. Stability of asynchronous pulse systems with random perturbations of parameters

    NARCIS (Netherlands)

    Gelig, AK

    The mean-square frequency stability conditions under arbitrary initial perturbations for an asynchronous system consisting of a linear part with Gaussian perturbations of coefficients and a fete pulse elements are derived.

  11. Proposed prioritization system for the management of invasive alien plants in South Africa

    CSIR Research Space (South Africa)

    Robertson, MP

    2003-01-01

    Full Text Available system described in this article was designed to assess objectively research and control priorities of invasive alien plants at a national scale in South Africa. The evaluation consists of seventeen criteria, grouped into five modules that assess...

  12. New stability conditions for nonlinear time varying delay systems

    Science.gov (United States)

    Elmadssia, S.; Saadaoui, K.; Benrejeb, M.

    2016-07-01

    In this paper, new practical stability conditions for a class of nonlinear time varying delay systems are proposed. The study is based on the use of a specific state space description, known as the Benrejeb characteristic arrow form matrix, and aggregation techniques to obtain delay-dependent stability conditions. Application of this method to delayed Lurie-Postnikov nonlinear systems is given. Illustrative examples are presented to show the effectiveness of the proposed approach.

  13. Stability of position control system in JIPP T-II

    International Nuclear Information System (INIS)

    Sakurai, Keiichi; Tanahashi, Shygo

    1980-01-01

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

  14. Preservation of stability and synchronization in nonlinear systems

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Anaya, G. [Departamento de Fisica y Matematicas, Universidad Iberoamericana, Prol. Paseo de la Reforma 880, Lomas de Santa Fe, Mexico, D.F. 01210 (Mexico)], E-mail: guillermo.fernandez@uia.mx; Flores-Godoy, J.J. [Departamento de Fisica y Matematicas, Universidad Iberoamericana, Prol. Paseo de la Reforma 880, Lomas de Santa Fe, Mexico, D.F. 01210 (Mexico)], E-mail: job.flores@uia.mx; Femat, R. [Division de Matematicas Aplicadas y Sistemas Computacionales, IPICyT, Camino a la Presa San Jose 2055, Col. Lomas 4a. seccion, San Luis Potosi, San Luis Potosi 78216 (Mexico)], E-mail: rfemat@ipicyt.edu.mx; Alvarez-Ramirez, J.J. [Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, Mexico, D.F. 09340 (Mexico)], E-mail: jjar@xanum.uam.mx

    2007-11-12

    Preservation of stability in the presence of structural and/or parametric changes is an important issue in the study of dynamical systems. A specific case is the synchronization of chaos in complex networks where synchronization should be preserved in spite of changes in the network parameters and connectivity. In this work, a methodology to establish conditions for preservation of stability in a class of dynamical system is given in terms of Lyapunov methods. The idea is to construct a group of dynamical transformations under which stability is retained along certain manifolds. Some synchronization examples illustrate the results.

  15. Theoretical bases on thermal stability of layered metallic systems

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  16. Preservation of stability and synchronization in nonlinear systems

    International Nuclear Information System (INIS)

    Fernandez-Anaya, G.; Flores-Godoy, J.J.; Femat, R.; Alvarez-Ramirez, J.J.

    2007-01-01

    Preservation of stability in the presence of structural and/or parametric changes is an important issue in the study of dynamical systems. A specific case is the synchronization of chaos in complex networks where synchronization should be preserved in spite of changes in the network parameters and connectivity. In this work, a methodology to establish conditions for preservation of stability in a class of dynamical system is given in terms of Lyapunov methods. The idea is to construct a group of dynamical transformations under which stability is retained along certain manifolds. Some synchronization examples illustrate the results

  17. Dynamic stabilization of regular linear systems

    NARCIS (Netherlands)

    Weiss, G; Curtain, RF

    We consider a general class of infinite-dimensional linear systems, called regular linear systems, for which convenient representations are known to exist both in time and in frequency domain, For this class of systems, we investigate the concepts of stabilizability and detectability, in particular,

  18. System Design Description PFP Thermal Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    RISENMAY, H.R.

    2000-01-27

    DOE has authorized in their letter of August 2, 1999, the operation of these three furnaces, quote ''Operation of the three uncompleted muffle furnaces (No.3, No.4, and No.5) located in Room 235B is authorized, using the same feed charge limits as the two existing furnaces (No.1, and No.2) located in Room 230C,''. The above statement incorrectly refers to Room 230C whereas the correct location is Room 230A. The current effort is directed to initiate the operation and to complete the design activities DOE authorized the operation of the furnaces based on their Safety Evaluation Report (SER). Based on analogy and the principle of similarity, the risks and consequences of accidents both onsite and offsite due to operation of three furnaces are not significantly larger than those already evaluated with the two operating furnaces. Thermal stabilization operations and the material of feed for furnaces in Glovebox HA-21 I are essentially the same as those currently being stabilized in furnaces in Glovebox HC-21 C. Therefore the accident analysis has utilized identical accident scenarios in evaluation and no additional failure modes are introduced by HA-21 I muffle furnace operation that would enhance the consequences of accidents. Authorization Basis documents as referenced below (PFP FSAR and DOE Letter authorizing the operation) appear to contradict each other, i.e. one allows and authorizes the operation and the other imposes the restriction on the operation. The purpose of the PFP FSAR restrictions was to review thoroughly the design and installation of three furnaces and perform acceptance testing before approving the startup for operation. With the experience of operating the two furnaces in Glovebox HC-21C, and the knowledge of risks and hazards the facility operation, the plant is adequately prepared to operate these additional furnaces. ECN 653595 has been prepared to incorporate operation of the muffle furnaces in Glovebox HA-21 I into the

  19. 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.

  20. Dynamic stabilization of a coupled ultracold atom-molecule system.

    Science.gov (United States)

    Li, Sheng-Chang; Ye, Chong

    2015-12-01

    We numerically demonstrate the dynamic stabilization of a strongly interacting many-body bosonic system which can be realized by coupled ultracold atom-molecule gases. The system is initialized to an unstable equilibrium state corresponding to a saddle point in the classical phase space, where subsequent free evolution gives rise to atom-molecule conversion. To control and stabilize the system, periodic modulation is applied that suddenly shifts the relative phase between the atomic and the molecular modes and limits their further interconversion. The stability diagram for the range of modulation amplitudes and periods that stabilize the dynamics is given. The validity of the phase diagram obtained from the time-average calculation is discussed by using the orbit tracking method, and the difference in contrast with the maximum absolute deviation analysis is shown as well. A brief quantum analysis shows that quantum fluctuations can put serious limitations on the applicability of the mean-field results.

  1. Stabilization of switched nonlinear systems with unstable modes

    CERN Document Server

    Yang, Hao; Cocquempot, Vincent

    2014-01-01

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

  2. Voltage stability margins assessment for Muscat power system

    Energy Technology Data Exchange (ETDEWEB)

    Ellithy, K.A.; Gastli, A. [Sultan Qaboos Univ., Dept. of Electrical Engineering and Electronics, Muscat (Oman); Al-Khusaibi, T. [Ministry of Housing and Electricity and Water, Muscat (Oman); Irving, M. [Brunel Univ., Dept. of Electrical Engineering and Electronics, Uxbridge (United Kingdom)

    2002-10-01

    Voltage instability problems in power systems today are, in many countries, one of the major concerns in power system planning and operation. This paper presents the assessment of voltage stability margins for Muscat power system under normal operating condition and under contingencies. The modal analysis method is applied to identify the weak buses in the system, which could lead to voltage instability. These weak buses are selected as the best locations for applying remedial actions to enhance the stability margins. The results show that the buses at South Batna load area are the weakest buses in the system. The results also show that an increase in load demand on that area without an adequate increase of reactive power could lead to voltage collapse. Shunt VAR compensations (remedial action) are installed at the weakest buses to enhance the system stability margins. The results presented in this paper are obtained using a MATLAB computer program developed by the authors. (Author)

  3. Experimental study of flame stability in biogas premix system

    International Nuclear Information System (INIS)

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

    2008-01-01

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

  4. Global dynamics and stabilization of rigid body attitude systems

    Science.gov (United States)

    Chaturvedi, Nalin Arvind

    Attitude control is fundamental to the design and operation of many large engineering systems that consist in whole or in part of rotational components, with system performance defined in terms of global attitude control objectives. The 3D pendulum is a rigid body, freely rotating about a pivot point that is not the center-of-mass. It is acted upon by gravitational and control moments. New results are obtained for the problem of feedback stabilization of a 3D pendulum; these results exemplify attitude stabilization for a 3-DOF rigid body with potential forces. New results are first obtained for the global dynamics of the 3D pendulum. We identify integrals of its motion, and it is shown that the 3D pendulum has two disjoint equilibrium manifolds, namely the hanging equilibrium manifold and the inverted equilibrium manifold. New nonlinear controllers are shown to provide almost global stabilization of these equilibrium manifolds or almost global stabilization of any desired equilibrium in these manifolds. We identify a performance constraint, namely that there are closed-loop trajectories that can take arbitrarily long to converge to the equilibrium. We then study the problem of stabilization under input saturation effects. We show that as long as the saturation limit is greater than a certain lower bound, the inverted equilibrium manifold or any desired equilibrium in these manifolds, can be almost globally asymptotically stabilized. A new non-smooth controller is proposed that stabilizes the inverted equilibrium manifold such that the domain of attraction is almost global and is geometrically simple, and the closed-loop does not exhibit a performance constraint. We then present experimental results on stabilization of the inverted equilibrium manifold illustrating the closed-loop performance. Next, new stabilization results for an axially symmetric 3D pendulum are presented that generalize stabilization results in the literature for the planar pendulum, the

  5. Quorum sensing system lactones do not increase invasiveness of a MexAB-OprM efflux mutant but do play a partial role in Pseudomonas aeruginosa invasion.

    Science.gov (United States)

    Kondo, Akira; Hirakata, Yoichi; Gotoh, Naomasa; Fukushima, Kazuko; Yanagihara, Katsunori; Ohno, Hideaki; Higashiyama, Yasuhito; Miyazaki, Yoshitugu; Nishide, Kiyoharu; Node, Manabu; Yamada, Yasuaki; Kohno, Shigeru; Kamihira, Shimeru

    2006-01-01

    We studied the quorum sensing (QS) system and the related homoserine lactones (HSLs) observing Pseudomonas aeruginosa invasion using the epithelial cell monolayer penetration assay model. Compared to the PAO1 wild-type, the QS mutants, DeltalasI and DeltarhlI, were compromised in their capacity to invade. The decreased invasiveness of DeltarhlI was restored by adding 100 microM exogenous C(4)-HSL. However, the decreased invasiveness of an efflux mutant, DeltamexAB-oprM, was not restored in the presence of exogenous HSLs. The QS system partially plays a role in P. aeruginosa invasion; however, C(4)-HSL and 3-O-C(12)-HSL are not the essential determinants for invasiveness for P. aeruginosa.

  6. The electric power engineering handbook power system stability and control

    CERN Document Server

    Grisby, Leonard L

    2012-01-01

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

  7. Stability Analysis for a Multi-Camera Photogrammetric System

    Directory of Open Access Journals (Sweden)

    Ayman Habib

    2014-08-01

    Full Text Available Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, and describes the existing methods for performing stability analysis for a single camera. The paper then points out the lack of coverage of stability analysis for multi-camera systems, suggests a modification of the collinearity model to be used for the calibration of an entire photogrammetric system, and proposes three methods for system stability analysis. The proposed methods explore the impact of the changes in interior orientation and relative orientation/mounting parameters on the reconstruction process. Rather than relying on ground truth in real datasets to check the system calibration stability, the proposed methods are simulation-based. Experiment results are shown, where a multi-camera photogrammetric system was calibrated three times, and stability analysis was performed on the system calibration parameters from the three sessions. The proposed simulation-based methods provided results that were compatible with a real-data based approach for evaluating the impact of changes in the system calibration parameters on the three-dimensional reconstruction.

  8. Almost Sure Stability and Stabilization for Hybrid Stochastic Systems with Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Hua Yang

    2012-01-01

    Full Text Available The problems of almost sure (a.s. stability and a.s. stabilization are investigated for hybrid stochastic systems (HSSs with time-varying delays. The different time-varying delays in the drift part and in the diffusion part are considered. Based on nonnegative semimartingale convergence theorem, Hölder’s inequality, Doob’s martingale inequality, and Chebyshev’s inequality, some sufficient conditions are proposed to guarantee that the underlying nonlinear hybrid stochastic delay systems (HSDSs are almost surely (a.s. stable. With these conditions, a.s. stabilization problem for a class of nonlinear HSDSs is addressed through designing linear state feedback controllers, which are obtained in terms of the solutions to a set of linear matrix inequalities (LMIs. Two numerical simulation examples are given to show the usefulness of the results derived.

  9. 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.

  10. Nuclear Hybrid Energy System Model Stability Testing

    Energy Technology Data Exchange (ETDEWEB)

    Greenwood, Michael Scott [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cetiner, Sacit M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Fugate, David W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-04-01

    A Nuclear Hybrid Energy System (NHES) uses a nuclear reactor as the basic power generation unit, and the power generated is used by multiple customers as combinations of thermal power or electrical power. The definition and architecture of a particular NHES can be adapted based on the needs and opportunities of different localities and markets. For example, locations in need of potable water may be best served by coupling a desalination plant to the NHES. Similarly, a location near oil refineries may have a need for emission-free hydrogen production. Using the flexible, multi-domain capabilities of Modelica, Argonne National Laboratory, Idaho National Laboratory, and Oak Ridge National Laboratory are investigating the dynamics (e.g., thermal hydraulics and electrical generation/consumption) and cost of a hybrid system. This paper examines the NHES work underway, emphasizing the control system developed for individual subsystems and the overall supervisory control system.

  11. Stability Analysis of Neural Networks-Based System Identification

    Directory of Open Access Journals (Sweden)

    Talel Korkobi

    2008-01-01

    Full Text Available This paper treats some problems related to nonlinear systems identification. A stability analysis neural network model for identifying nonlinear dynamic systems is presented. A constrained adaptive stable backpropagation updating law is presented and used in the proposed identification approach. The proposed backpropagation training algorithm is modified to obtain an adaptive learning rate guarantying convergence stability. The proposed learning rule is the backpropagation algorithm under the condition that the learning rate belongs to a specified range defining the stability domain. Satisfying such condition, unstable phenomena during the learning process are avoided. A Lyapunov analysis leads to the computation of the expression of a convenient adaptive learning rate verifying the convergence stability criteria. Finally, the elaborated training algorithm is applied in several simulations. The results confirm the effectiveness of the CSBP algorithm.

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

    Science.gov (United States)

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

    2006-05-01

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

  13. The type VI secretion system impacts bacterial invasion and population dynamics in a model intestinal microbiota

    Science.gov (United States)

    Logan, Savannah L.; Shields, Drew S.; Hammer, Brian K.; Xavier, Joao B.; Parthasarathy, Raghuveer

    Animal gastrointestinal tracts are home to a diverse community of microbes. The mechanisms by which microbial species interact and compete in this dense, physically dynamic space are poorly understood, limiting our understanding of how natural communities are assembled and how different communities could be engineered. Here, we focus on a physical mechanism for competition: the type VI secretion system (T6SS). The T6SS is a syringe-like organelle used by certain bacteria to translocate effector proteins across the cell membranes of target bacterial cells, killing them. Here, we use T6SS+ and T6SS- strains of V. cholerae, the pathogen that causes cholera in humans, and light sheet fluorescence microscopy for in vivo imaging to show that the T6SS provides an advantage to strains colonizing the larval zebrafish gut. Furthermore, we show that T6SS+ bacteria can invade and alter an existing population of a different species in the zebrafish gut, reducing its abundance and changing the form of its population dynamics. This work both demonstrates a mechanism for altering the gut microbiota with an invasive species and explores the processes controlling the stability and dynamics of the gut ecosystem. Research Corporation, Gordon and Betty Moore Foundation, and the Simons Foundation.

  14. Toward a global information system for invasive species

    Science.gov (United States)

    Ricciardi, Anthony; Steiner, William W.M.; Mack, Richard N.; Simberloff, Daniel

    2000-01-01

    The growing frequency and impact of biological invasions worldwide threaten biodiversity, ecosystem functioning, resource availability, national economies, and human health (Ruesink et al. 1995, Simberloff 1996, Vitousek et al. 1997). Organisms are spreading into new regions at unprecedented rates. As a result, hundreds to thousands of nonindigenous species of invertebrates, vertebrates, plants, bacteria, and fungi have become established in all but the most remote areas of the planet (Vitousek et al. 1997). Recent examples are abundant and, in some cases, alarming. Cholera bacteria and toxic dinoflagellates have been discovered in the ballast waters of cargo ships (McCarthy and Khambaty 1994, Hallegraeff 1998). Asian tiger mosquitos—vectors of yellow fever and encephalitis—have spread to new continents in imported truck tires (Moore et al. 1988). Pasture and crop lands in Australia are being invaded by Parthenium, an aggressive Caribbean weed that causes severe allergic reactions in livestock and humans (Evans 1997). Rapid and widespread dieoffs of native freshwater mussels are occurring in the wake of the zebra mussel invasion in North America (Ricciardi et al. 1998). [[AQ4]Hardwood trees in American cities are being killed by Asian long-horned beetles introduced with wooden packing crates (Haack et al. 1997).

  15. Stability of multiplanetary systems in star clusters

    NARCIS (Netherlands)

    Cai, X.; Kouwenhoven, M.B.N.; Portegies, Zwart S.F.; Spurzem, R.

    2017-01-01

    Most stars form in star clusters and stellar associations. However, only about ˜1 per cent of the presently known exoplanets are found in these environments. To understand the roles of star cluster environments in shaping the dynamical evolution of planetary systems, we carry out direct N-body

  16. Transient stability risk assessment of power systems incorporating wind farms

    DEFF Research Database (Denmark)

    Miao, Lu; Fang, Jiakun; Wen, Jinyu

    2013-01-01

    Large-scale wind farm integration has brought several aspects of challenges to the transient stability of power systems. This paper focuses on the research of the transient stability of power systems incorporating with wind farms by utilizing risk assessment methods. The detailed model of double...... fed induction generator has been established. Wind penetration variation and multiple stochastic factors of power systems have been considered. The process of transient stability risk assessment based on the Monte Carlo method has been described and a comprehensive risk indicator has been proposed....... An investigation has been conducted into an improved 10-generator 39-bus system with a wind farm incorporated to verify the validity and feasibility of the risk assessment method proposed....

  17. Power system transient stability analysis based on branch potential characteristics

    Science.gov (United States)

    Han, Huan; Wang, Zengping

    2017-09-01

    Branch potential function is proposed based on the power system network preserving model. The concept of thermodynamics-entropy, is introduced to describe spatial distribution characteristics of the branch potential energy. Branch potential energy was analysed in time and space domain., with transient stability index proposed accordingly. The larger disturbance energy line fault injected to grid is, the larger branch energy entropy will be, and the more energy accumulated on key branches is, the more prone to lose stability the system will be. Simulation results on IEEE system proved its feasibility.

  18. FINANCIAL STABILITY OF THE UKRAINE NATIONAL SYSTEM OF PENSION INSURANCE

    Directory of Open Access Journals (Sweden)

    A. Khemii

    2014-03-01

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

  19. Stability Analysis and Design of Impulsive Control Lorenz Systems Family

    International Nuclear Information System (INIS)

    Yu Yongbin; Zhang Fengli; Zhang Hongbin; Yu Juebang; Liao Xiaofeng

    2009-01-01

    Lorenz systems family unifying Lorenz system, Chen system and Lue system is a typical chaotic family. In this paper, we consider impulsive control Lorenz chaotic systems family with time-varying impulse intervals. By establishing an effective tool of a set of inequalities, we analyze the asymptotic stability of impulsive control Lorenz systems family and obtain some new less conservative conditions. Based on the stability analysis, we design a novel impulsive controller with time-varying impulse intervals. Illustrative examples are provided to show the feasibility and effectiveness of our method. The obtained results not only can be used to design impulsive control for Lorenz systems family, but also can be extended to other chaotic systems. (general)

  20. On stability of accelerator driven systems

    International Nuclear Information System (INIS)

    Makai, Mihaly

    2003-01-01

    An unsolved problem of energy production in nuclear reactors is the waste management. A large portion of the nuclear waste is the spent fuel. At present, two possibilities are seen. The first one is to 'wrap up' all the radioactive waste safely and to bury it at a remote quiet place where it can rest undisturbed until its activity decreases to a tolerable level. The second one is to exploit the excitation energy still present in the nuclear waste. In order to release that energy, the spent fuel is bombarded by high energy particles obtained from an accelerator. The resulting system is called accelerator driven system (ADS). In an ADS, the spent fuel forms a subcritical reactor, which is driven by an external source. (author)

  1. Gyroscopic stabilization and indefimite damped systems

    DEFF Research Database (Denmark)

    Pommer, Christian

    a class of feasibel skew-Hermitian matrices A depending on the choise of M. The theory can be applied to dynamical systems of the form x''(t) + ( dD + g G) x'(t) + K x(t) = 0 where G is a skew symmetric gyrocopic matrix, D is a symmetric indefinite damping matrix and K > 0 is a positive definite stiffness...

  2. Lapabot: a compact telesurgical robot system for minimally invasive surgery: part I. System description.

    Science.gov (United States)

    Choi, Jaesoon; Park, Jun Woo; Kim, Dong Jun; Shin, Jungwook; Park, Chan Young; Lee, Jung Chan; Jo, Yung Ho

    2012-05-01

    The applications of robotic minimally invasive surgery (MIS) have widened, providing new advantages such as augmented dexterity and telesurgery. However, current commercial robotic laparoscopic surgical systems still have aspects to be improved such as heavy and bulky systems not suitable for agile operations, large rotational radii of robot manipulator arms, limited remote control capacity, and absence of force feedback. We have developed a robotic laparoscopic surgical system that features compact slave manipulators. The system can simultaneously operate one laparoscope arm and up to four instrument arms. The slave robot is controlled remotely through an Ethernet network and is ready for telesurgery. The developed surgical robot has sufficient workspace to perform general MIS and has been shown to provide acceptable motion tracking control performance.

  3. Metelitsyn's inequality and stability criteria for mechanical systems

    DEFF Research Database (Denmark)

    Kliem, Wolfhard; Seyranian, A. P.

    2004-01-01

    . Metelitsyn's theorems based on his inequality as well as critical comments in the literature on these theorems are analysed. Practical sufficient stability criteria are obtained in terms of extreme eigenvalues of the system matrices. This analysis is of special value for rotor systems in a complex setting...... which is demonstrated by three examples. (C) 2004 Elsevier Ltd. All rights reserved....

  4. On stability of fixed points and chaos in fractional systems

    Science.gov (United States)

    Edelman, Mark

    2018-02-01

    In this paper, we propose a method to calculate asymptotically period two sinks and define the range of stability of fixed points for a variety of discrete fractional systems of the order 0 logistic maps. Based on our analysis, we make a conjecture that chaos is impossible in the corresponding continuous fractional systems.

  5. Indefinite damping in mechanical systems and gyroscopic stabilization

    DEFF Research Database (Denmark)

    Kliem, Wolfhard; Pommer, Christian

    2009-01-01

    This paper deals with gyroscopic stabilization of the unstable system Mx + D(x) over dot + K-x = 0, with positive definite mass and stiffness matrices M and K, respectively, and an indefinite damping matrix D. The main question if for which skew-symmetric matrices G the system Mx (D+ G)(x) over d...

  6. Stability of time-delay systems via Lyapunov functions

    Directory of Open Access Journals (Sweden)

    Carlos F. Alastruey

    2002-01-01

    Full Text Available In this paper, a Lyapunov function candidate is introduced for multivariable systems with inner delays, without assuming a priori stability for the nondelayed subsystem. By using this Lyapunov function, a controller is deduced. Such a controller utilizes an input–output description of the original system, a circumstance that facilitates practical applications of the proposed approach.

  7. Criteria for stability of linear dynamical systems with multiple delays ...

    African Journals Online (AJOL)

    In this study we considered a linear Dynamical system with multiple delays and find suitable conditions on the systems parameters such that for a given initial function, we can define a mapping in a carefully chosen complete metric space on which the mapping has a unique fixed point. An asymptotic stability theory for the ...

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

    Directory of Open Access Journals (Sweden)

    Jeevanandham Arumugam

    2009-01-01

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

  9. Stabilization of third-order bilinear systems using constant controls

    Directory of Open Access Journals (Sweden)

    A. E. Golubev

    2014-01-01

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

  10. Design of an adaptive neural network based power system stabilizer.

    Science.gov (United States)

    Liu, Wenxin; Venayagamoorthy, Ganesh K; Wunsch, Donald C

    2003-01-01

    Power system stabilizers (PSS) are used to generate supplementary control signals for the excitation system in order to damp the low frequency power system oscillations. To overcome the drawbacks of conventional PSS (CPSS), numerous techniques have been proposed in the literature. Based on the analysis of existing techniques, this paper presents an indirect adaptive neural network based power system stabilizer (IDNC) design. The proposed IDNC consists of a neuro-controller, which is used to generate a supplementary control signal to the excitation system, and a neuro-identifier, which is used to model the dynamics of the power system and to adapt the neuro-controller parameters. The proposed method has the features of a simple structure, adaptivity and fast response. The proposed IDNC is evaluated on a single machine infinite bus power system under different operating conditions and disturbances to demonstrate its effectiveness and robustness.

  11. Exponential Stability of Stochastic Systems with Delay and Poisson Jumps

    Directory of Open Access Journals (Sweden)

    Wenli Zhu

    2014-01-01

    Full Text Available This paper focuses on the model of a class of nonlinear stochastic delay systems with Poisson jumps based on Lyapunov stability theory, stochastic analysis, and inequality technique. The existence and uniqueness of the adapted solution to such systems are proved by applying the fixed point theorem. By constructing a Lyapunov function and using Doob’s martingale inequality and Borel-Cantelli lemma, sufficient conditions are given to establish the exponential stability in the mean square of such systems, and we prove that the exponentially stable in the mean square of such systems implies the almost surely exponentially stable. The obtained results show that if stochastic systems is exponentially stable and the time delay is sufficiently small, then the corresponding stochastic delay systems with Poisson jumps will remain exponentially stable, and time delay upper limit is solved by using the obtained results when the system is exponentially stable, and they are more easily verified and applied in practice.

  12. Robust stabilization of nonlinear systems: The LMI approach

    Directory of Open Access Journals (Sweden)

    Šiljak D. D.

    2000-01-01

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

  13. Stability of Spline-Type Systems in the Abelian Case

    Directory of Open Access Journals (Sweden)

    Darian Onchis

    2017-12-01

    Full Text Available In this paper, the stability of translation-invariant spaces of distributions over locally compact groups is stated as boundedness of synthesis and projection operators. At first, a characterization of the stability of spline-type spaces is given, in the standard sense of the stability for shift-invariant spaces, that is, linear independence characterizes lower boundedness of the synthesis operator in Banach spaces of distributions. The constructive nature of the proof for Theorem 2 enabled us to constructively realize the biorthogonal system of a given one. Then, inspired by the multiresolution analysis and the Lax equivalence for general discretization schemes, we approached the stability of a sequence of spline-type spaces as uniform boundedness of projection operators. Through Theorem 3, we characterize stable sequences of stable spline-type spaces.

  14. Stability of Spline-Type Systems in the Abelian Case.

    Science.gov (United States)

    Onchis, Darian; Zappalà, Simone

    2017-12-27

    In this paper, the stability of translation-invariant spaces of distributions over locally compact groups is stated as boundedness of synthesis and projection operators. At first, a characterization of the stability of spline-type spaces is given, in the standard sense of the stability for shift-invariant spaces, that is, linear independence characterizes lower boundedness of the synthesis operator in Banach spaces of distributions. The constructive nature of the proof for Theorem 2 enabled us to constructively realize the biorthogonal system of a given one. Then, inspired by the multiresolution analysis and the Lax equivalence for general discretization schemes, we approached the stability of a sequence of spline-type spaces as uniform boundedness of projection operators. Through Theorem 3, we characterize stable sequences of stable spline-type spaces.

  15. Synthesized dynamic modeling and stability analysis of novel HVDC system

    Energy Technology Data Exchange (ETDEWEB)

    Xu Sun; Li Kong [Inst. of Electrical Engineering, CAS, BJ (China)

    2008-07-01

    At the present time, many projects large offshore wind power fields connecting to the grid adopt the novel HVDC technology. Voltage source converter structure and PWM modulation technology are used in the system and active power and reactive power can be controlled respectively, so it can ensure the excellent performance of the projects. It is very necessary to build its detailed dynamic model and analyze its stability to be the base for further research. In this paper, firstly, the switch function model is established as the base of further analysis. Secondly, the steady model, small signal model and high frequency dynamic model of novel HVDC based on state space average method are established respectively. Thirdly, the stability of the whole system is analyzed on the base of above models of the novel HVDC. Finally, the whole system is validated practically by simulation analysis to prove the validity of model and stability analysis. (orig.)

  16. Stabilizing non-Hermitian systems by periodic driving

    Science.gov (United States)

    Gong, Jiangbin; Wang, Qing-hai

    2015-04-01

    The time evolution of a system with a time-dependent non-Hermitian Hamiltonian is in general unstable with exponential growth or decay. A periodic driving field may stabilize the dynamics because the eigenphases of the associated Floquet operator may become all real. This possibility can emerge for a continuous range of system parameters with subtle domain boundaries. It is further shown that the issue of stability of a driven non-Hermitian Rabi model can be mapped onto the band structure problem of a class of lattice Hamiltonians. As a straightforward application, we show how to use the stability of driven non-Hermitian two-level systems (0 dimension in space) to simulate a spectrum analogous to Hofstadter's butterfly that has played a paradigmatic role in quantum Hall physics. The simulation of the band structure of non-Hermitian superlattice potentials with parity-time reversal symmetry is also briefly discussed.

  17. 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...

  18. Estimation of Power System Stabilizer Parameters Using Swarm Intelligence Techniques to Improve Small Signal Stability of Power System

    Directory of Open Access Journals (Sweden)

    Hossein Soleymani

    2017-08-01

    Full Text Available Interconnection of the power system utilities and grids offers a formidable dispute in front of design engineers. With the interconnections, power system has emerged as a more intricate and nonlinear system. Recent years small signal stability problems have achieved much significance along with the conventional transient constancy problems. Transient stability of the power system can be attained with high gain and fast acting Automatic Voltage Regulators (AVRs. Yet, AVRs establish negative damping in the system. Propagation of small signals is hazardous for system’s health and offers a potential threat to system’s oscillatory stability. These small signals have magnitude of 0.2 to 2 Hz. The professional control tactic to develop system damping is Power System Stabilizer (PSS.This paper presents application of swarm intelligence for PSS parameter estimation issue on standard IEEE 10 Generator 39 Bus power network (New England. Realization of the objective function is done with the help of interpolation investigation using MATLAB. The system performance is compared with the conventional optimization algorithms like Genetic Algorithm (GA and Particle Swarm Optimization (PSO based PSS controller. The strength of proposed controller is tested by examining various operating conditions. An Eigen property analysis is done on this system i.e. before installing PSS, and after the employment of GA and PSO tuned PSSs. A significant comparison is carried out with GA and PSO on the basis of convergence uniqueness and dynamic response of speed deviation curves of various generators.

  19. The Hill stability of triple planets in the Solar system

    Science.gov (United States)

    Liu, Chao; Gong, Shengping

    2017-07-01

    The Hill stability of the nine known triple asteroid systems in the solar system has been investigated in a framework of the three body system. In this paper, the Sun and triple-asteroid system are treated as a four body system to analyze the influence of the Sun on the Hill stability of the triple subsystem. First, the relationship of the total energy and the angular momentum between the four body system and the triple subsystem is derived. It is found that the total energy of this 1-3 configuration four body system is the sum of the energy of the triple subsystem and the energy of a two-body system composed of the Sun and the mass center of the subsystem; so is the angular momentum. Then, the Hill stability of the triple subsystem is reinvestigated using a previous criterion in the four body problem (Gong and Liu in Mon. Not. R. Astron. Soc. 462:547-553, 2016) and the results are compared to those in the three body problem. Among the nine known triple-asteroid systems, 1995 CC and 1999 TC are Hill stable for both models; the others are stable in the three body model while not stable in the four body model. In addition, the exploration of Pluto by New Horizons has attracted great attention in recent years, the Sun-Pluto-Charon-Hydra four body system is investigated in the paper, and it is found that the system is Hill stable.

  20. A Novel Differential Evolution Invasive Weed Optimization Algorithm for Solving Nonlinear Equations Systems

    Directory of Open Access Journals (Sweden)

    Yongquan Zhou

    2013-01-01

    Full Text Available In view of the traditional numerical method to solve the nonlinear equations exist is sensitive to initial value and the higher accuracy of defects. This paper presents an invasive weed optimization (IWO algorithm which has population diversity with the heuristic global search of differential evolution (DE algorithm. In the iterative process, the global exploration ability of invasive weed optimization algorithm provides effective search area for differential evolution; at the same time, the heuristic search ability of differential evolution algorithm provides a reliable guide for invasive weed optimization. Based on the test of several typical nonlinear equations and a circle packing problem, the results show that the differential evolution invasive weed optimization (DEIWO algorithm has a higher accuracy and speed of convergence, which is an efficient and feasible algorithm for solving nonlinear systems of equations.

  1. Communications and control for electric power systems: Power system stability applications of artificial neural networks

    Science.gov (United States)

    Toomarian, N.; Kirkham, Harold

    1994-01-01

    This report investigates the application of artificial neural networks to the problem of power system stability. The field of artificial intelligence, expert systems, and neural networks is reviewed. Power system operation is discussed with emphasis on stability considerations. Real-time system control has only recently been considered as applicable to stability, using conventional control methods. The report considers the use of artificial neural networks to improve the stability of the power system. The networks are considered as adjuncts and as replacements for existing controllers. The optimal kind of network to use as an adjunct to a generator exciter is discussed.

  2. On the conditional total stability of equilibrium for mechanical systems

    Directory of Open Access Journals (Sweden)

    L. Salvadori

    1991-05-01

    Full Text Available In connection with the problem of observability, properties of total stability restricted to classes of perturbations of the governing equations are discussed for the equilibrium of holonomic mechanical systems. These systems are subject to positional conservative and dissipative forces. The particular case of a null dissipation is included. The perturbations to which the total stability is restricted are those obtained by modifying the kinetic energy, the potential of the conservative force, and the dissipative terms, without altering the Lagrangian form of the equations of the motion.

  3. Robust Stabilization of Nonlinear Systems with Uncertain Varying Control Coefficient

    Directory of Open Access Journals (Sweden)

    Zaiyue Yang

    2014-01-01

    Full Text Available This paper investigates the stabilization problem for a class of nonlinear systems, whose control coefficient is uncertain and varies continuously in value and sign. The study emphasizes the development of a robust control that consists of a modified Nussbaum function to tackle the uncertain varying control coefficient. By such a method, the finite-time escape phenomenon has been prevented when the control coefficient is crossing zero and varying its sign. The proposed control guarantees the asymptotic stabilization of the system and boundedness of all closed-loop signals. The control performance is illustrated by a numerical simulation.

  4. Multiple-pattern stability in a photorefractive feedback system

    DEFF Research Database (Denmark)

    Schwab, M.; Denz, C.; Saffman, M.

    1999-01-01

    We report on the observation of a multiple-pattern stability region in a photorefractive single-feedback system. Whereas hexagonal patterns are predominant for feedback with positive diffraction length we show that a variety of stable non-hexagonal patterns are generated for certain negative...... diffraction lengths. For the same values of the control parameters square, rectangular, or squeezed hexagonal patterns are found alternating in time. Besides these pure states, we found a number of different mixed-pattern states. We review the linear stability analysis for this system and show...

  5. Systems to accelerate in situ stabilization of waste deposits

    Energy Technology Data Exchange (ETDEWEB)

    Amdurer, M.; Fellman, R.T.; Roetzer, J.; Russ, C.

    1986-09-01

    In-situ systems to accelerate the stabilization of waste deposits involve three essential elements: selection of a chemical or biological agent (reactant) that can react with and stabilize the waste, a method for delivery of the reactant to the deposit, and a method for recovery of the reaction products or mobilized waste. Four reactant categories were examined: biodegradation, surfactant-assistant flushing, hydrolysis, and oxidation. Of these, biodegradation and surfactant-assisted flushing appear most promising as in-situ treatment techniques. Methods of delivery of reactants based upon gravity include surface flooding, ponding, surface spraying, ditching, and subsurface infiltration beds and galleries. Forced injection (pumping) may also be used. Permeability is an important consideration in selecting the delivery system. Recovery systems using gravity include open ditching and buried drains, and pumped methods include wellpoint and deep well systems. Basically, the same limitations that apply to delivery systems are also true for recovery systems.

  6. On the stability of boundary layers in gas mantle systems

    International Nuclear Information System (INIS)

    Ohlsson, D.

    1978-10-01

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

  7. Differential contribution of tryptophans to the folding and stability of the attachment invasion locus transmembrane β-barrel from Yersinia pestis.

    Science.gov (United States)

    Gupta, Ankit; Zadafiya, Punit; Mahalakshmi, Radhakrishnan

    2014-09-30

    Attachment invasion locus (Ail) protein of Yersinia pestis is a crucial outer membrane protein for host invasion and determines bacterial survival within the host. Despite its importance in pathogenicity, surprisingly little is known on Ail biophysical properties. We investigate the contribution of micelle concentrations and interface tryptophans on the Ail β-barrel refolding and unfolding processes. Our results reveal that barrel folding is surprisingly independent of micelle amounts, but proceeds through an on-pathway intermediate that requires the interface W42 for cooperative barrel refolding. On the contrary, the unfolding event is strongly controlled by absolute micelle concentrations. We find that upon Trp → Phe substitution, protein stabilities follow the order W149F>WT>W42F for the refolding, and W42F>WT>W149F for unfolding. W42 confers cooperativity in barrel folding, and W149 clamps the post-folded barrel structure to its micelle environment. Our analyses reveal, for the first time, that interface tryptophan mutation can indeed render greater β-barrel stability. Furthermore, hysteresis in Ail stems from differential barrel-detergent interaction strengths in a micelle concentration-dependent manner, largely mediated by W149. The kinetically stabilized Ail β-barrel has strategically positioned tryptophans to balance efficient refolding and subsequent β-barrel stability, and may be evolutionarily chosen for optimal functioning of Ail during Yersinia pathogenesis.

  8. AC system stabilization via phase shift transformer with thyristor commutation

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Jose Carlos de; Guimaraes, Geraldo Caixeta; Moraes, Adelio Jose [Uberlandia Univ., MG (Brazil); Abreu, Jose Policarpo G. de [Escola Federal de Engenharia de Itajuba, MG (Brazil); Oliveira, Edimar Jose de [Juiz de Fora Univ., MG (Brazil)

    1994-12-31

    This article aims to present initially the constructive and operative forms of a phase-shift autotransformer which provides both magnitude and phase angle change through thyristor commutation, including a technic to reduce the number of thyristors. Following, it is proposed a control system to make such equipment an efficient AC system stabilizing tool. It is presented some simulation results to show the operation of this transformer in an electrical system. (author) 3 refs., 11 figs., 3 tabs.

  9. Comparison of Different Techniques For Tuning of Power System Stabilizer

    OpenAIRE

    BAYAT, Ehsan; DELAVARİ, Hadi

    2015-01-01

    Abstract. The power system is subjected to different types of disturbances such as small changes in the load that affects its efficiency and sometimes leads to unstable system. These disturbances cause oscillations at low frequencies that are undesirable since it affects the amount of transferred power through the transmission lines and leads to external stress to the mechanical shaft. In order to compress low-frequency oscillations, a common solution is use the power system stabilizer (PSS)....

  10. Passivity Based Stabilization of Non-minimum Phase Nonlinear Systems

    Czech Academy of Sciences Publication Activity Database

    Travieso-Torres, J.C.; Duarte-Mermoud, M.A.; Zagalak, Petr

    2009-01-01

    Roč. 45, č. 3 (2009), s. 417-426 ISSN 0023-5954 R&D Projects: GA ČR(CZ) GA102/07/1596 Institutional research plan: CEZ:AV0Z10750506 Keywords : nonlinear systems * stabilisation * passivity * state feedback Subject RIV: BC - Control Systems Theory Impact factor: 0.445, year: 2009 http://library.utia.cas.cz/separaty/2009/AS/zagalak-passivity based stabilization of non-minimum phase nonlinear systems.pdf

  11. Decentralized, cooperative control of multivehicle systems: Design and stability analysis

    Science.gov (United States)

    Weitz, Lesley Anne

    2009-12-01

    This dissertation addresses the design and stability analysis of decentralized, cooperative control laws for multivehicle systems. Advances in communication, navigation, and surveillance systems have enabled greater autonomy in multivehicle systems, and there is a shift toward decentralized, cooperative systems for computational efficiency and robustness. In a decentralized control scheme, control inputs are determined onboard each vehicle; therefore, decentralized controllers are more efficient for large numbers of vehicles, and the system is more robust to communication failures and reconfiguration. The design of decentralized, cooperative control laws is explored for a nonlinear vehicle model that can be represented in a double-integrator form. Cooperative controllers are functions of spacing errors with respect to other vehicles in the system, where the communication structure defines the information that is available to each vehicle. Control inputs are selected to achieve internal stability, or zero steady-state spacing errors, between vehicles in the system. Closed-loop equations of motion for the cooperative system can be written in a structural form, where damping and stiffness matrices contain control gains acting on the velocity and positions of the vehicles, respectively. The form of the stiffness matrix is determined by the communication structure, where different communication structures yield different control forms. Communication structures are compared using two structural analysis tools: modal cost and frequency-response functions, which evaluate the response of the multivehicle systems to disturbances. The frequency-response information is shown to reveal the string stability of different cooperative control forms. The effects of time delays in the feedback states of the cooperative control laws on system stability are also investigated. Closed-loop equations of motion are modeled as delay differential equations, and two stability notions are

  12. Stability of a planet in the HD 41004 binary system

    Science.gov (United States)

    Satyal, S.; Musielak, Z. E.

    2016-03-01

    The Hill stability criterion is applied to analyse the stability of a planet in the binary star system of HD 41004 AB, with the primary and secondary separated by 22 AU, and masses of 0.7 M_⊙ and 0.4 M_⊙, respectively. The primary hosts one planet in an S-type orbit, and the secondary hosts a brown dwarf (18.64 M_J) on a relatively close orbit, 0.0177 AU, thereby forming another binary pair within this binary system. This star-brown dwarf pair (HD 41004 B+Bb) is considered a single body during our numerical calculations, while the dynamics of the planet around the primary, HD 41004 Ab, is studied in different phase-spaces. HD 41004 Ab is a 2.6 M_J planet orbiting at the distance of 1.7 AU with orbital eccentricity 0.39. For the purpose of this study, the system is reduced to a three-body problem and is solved numerically as the elliptic restricted three-body problem (ERTBP). The {Hill stability} function is used as a chaos indicator to configure and analyse the orbital stability of the planet, HD 41004 Ab. The indicator has been effective in measuring the planet's orbital perturbation due to the secondary star during its periastron passage. The calculated Hill stability time series of the planet for the coplanar case shows the stable and quasi-periodic orbits for at least ten million years. For the reduced ERTBP the stability of the system is also studied for different values of planet's orbital inclination with the binary plane. Also, by recording the planet's {ejection time} from the system or {collision time} with a star during the integration period, stability of the system is analysed in a bigger phase-space of the planet's orbital inclination, ≤ 90o, and its semimajor axis, 1.65-1.75 AU. Based on our analysis it is found that the system can maintain a stable configuration for the planet's orbital inclination as high as 65o relative to the binary plane. The results from the Hill stability criterion and the planet's dynamical lifetime map are found to be

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

    OpenAIRE

    Jeevanandham Arumugam; Thanushkodi Gowder Keppana

    2009-01-01

    In this paper a classical lead-lag power system stabilizer is used for demonstration. The stabilizer parameters are selected in such a manner to damp the rotor oscillations. The problem of selecting the stabilizer parameters is converted to a simple optimization problem with an eigen value based objective function and it is proposed to employ simulated annealing and particle swarm optimization for solving the optimization problem. The objective function allows the selection of the stabilizer ...

  14. Stability of interconnected dynamical systems described on Banach spaces

    Science.gov (United States)

    Rasmussen, R. D.; Michel, A. N.

    1976-01-01

    New stability results for a large class of interconnected dynamical systems (also called composite systems or large scale systems) described on Banach spaces are established. In the present approach, the objective is always the same: to analyze large scale systems in terms of their lower order and simpler subsystems and in terms of their interconnecting structure. The present results provide a systematic procedure of analyzing hybrid dynamical systems (i.e., systems that are described by a mixture of different types of equations). To demonstrate the method of analysis advanced, two specific examples are considered.

  15. Genetic Algorithm Based Design of Fuzzy Logic Power System Stabilizers in Multimachine Power System

    OpenAIRE

    Manisha Dubey; Aalok Dubey

    2010-01-01

    This paper presents an approach for the design of fuzzy logic power system stabilizers using genetic algorithms. In the proposed fuzzy expert system, speed deviation and its derivative have been selected as fuzzy inputs. In this approach the parameters of the fuzzy logic controllers have been tuned using genetic algorithm. Incorporation of GA in the design of fuzzy logic power system stabilizer will add an intelligent dimension to the stabilizer and significantly reduces ...

  16. Design of Power System Stabilizer Based on Sliding Mode Control Theory for Multi- Machine Power System

    OpenAIRE

    Hossein Shahinzadeh; Ladan Darougaran; Ebrahim Jalili Sani; Hamed Yavari; Mahdi Mozaffari Legha

    2012-01-01

    This paper present a new method for design of power system stabilizer (PSS) based on sliding mode control (SMC) technique. The control objective is to enhance stability and improve the dynamic response of the multi-machine power system. In order to test effectiveness of the proposed scheme, simulation will be carried out to analyze the small signal stability characteristics of the system about the steady state operating condition following the change in reference mechanic...

  17. Systemic Staphylococcus aureus infection mediated by Candida albicans hyphal invasion of mucosal tissue

    NARCIS (Netherlands)

    Schlecht, L.M.; Peters, B.M.; Krom, B.P.; Freiberg, J.A.; Hänsch, G.M.; Filler, S.G.; Jabra-Rizk, M.A.; Shirtliff, M.E.

    2015-01-01

    Candida albicans and Staphylococcus aureus are often co-isolated in cases of biofilm-associated infections. C. albicans can cause systemic disease through morphological switch from the rounded yeast to the invasive hyphal form. Alternatively, systemic S. aureus infections arise from seeding through

  18. Improved stability and stabilization design for networked control systems using new quadruple-integral functionals.

    Science.gov (United States)

    Li, Zhichen; Bai, Yan; Li, Tianqi

    2016-07-01

    This paper investigates stability analysis and stabilization for networked control systems. By a refined delay decomposition approach, slightly different Lyapunov-Krasovskii functionals (LKFs) with quadruple-integral terms and augmented vectors containing triple-integral forms of state are constructed. New integral inequalities are proposed to estimate the cross terms from derivatives of the LKFs, which can be proved to offer tighter bounds than what the Jensen one produces theoretically. Moreover, the non-strictly proper rational functions in deriving process are fully handled via reciprocally convex approach. A state feedback controller design approach is also developed. Numerical examples and applications to practical power and oscillator systems demonstrate the superiority of the proposed criteria in conservatism reduction compared to some existing ones. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  19. Global Transient Stability and Voltage Regulation for Multimachine Power Systems

    DEFF Research Database (Denmark)

    Gordon, Mark; Hill, David J.

    2008-01-01

    This paper addresses simultaneously the major fundamental and difficult issues of nonlinearity, uncertainty, dimensionality and globality to derive performance enhancing power system stability control. The main focus is on simultaneous enhancement of transient stability and voltage regulation...... of power systems. This problem arises from the practical concern that both frequency and voltage control are important indices of power system control and operation but they are ascribed to different stages of system operation, i.e. the transient and post transient period respectively. The Direct Feedback...... Linearization (DFL) technique together with the robust control theory has been further developed and applied to design nonlinear excitation compensators which selectively eliminate system nonlinearities and deal with plant uncertainties and interconnections between generators. Then the so called global control...

  20. A Recursive Fuzzy System for Efficient Digital Image Stabilization

    Directory of Open Access Journals (Sweden)

    Nikolaos Kyriakoulis

    2008-01-01

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

  1. Wavelength stabilized multi-kW diode laser systems

    Science.gov (United States)

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

    2015-03-01

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

  2. The chick embryo as an experimental system for melanoma cell invasion.

    Directory of Open Access Journals (Sweden)

    Christian Busch

    Full Text Available BACKGROUND: A primary cutaneous melanoma will not kill the patient, but its metastases. Since in vitro studies on melanoma cells in 2-D cultures do often not reflect reality, 3-D models might come closer to the physiological situation in the patient during cancer initiation and progression. METHODOLOGY/PRINCIPAL FINDINGS: Here, we describe the chick embryo model for in vivo studies of melanoma cell migration and invasion. After transplantation of neural crest-derived melanoma cells into the neural tube, the melanoma cells resume neural crest cell migration along the medial and lateral pathways and finally undergo apoptosis in the target areas. Upon transplantation into ectopic areas such as the hindbrain or the optic cup malignant invasion and local tissue destruction occurs. In contrast, melanocytes are not able to spontaneously resume neural crest cell migration. However, malignant invasion can be induced in melanocytes by pre-treatment with the TGF-beta family members bone morphegenetic protein-2 or nodal. Transplantation of MCF7 breast cancer cells yields a different growth pattern in the rhombencephalon than melanoma cells. CONCLUSIONS/SIGNIFICANCE: The chick embryo model is a feasible, cost-effective in vivo system to study invasion by cancer cells in an embryonic environment. It may be useful to study invasive behavior induced by embryonic oncogenes and for targeted manipulation of melanoma or breast cancer cells aiming at ablation of invasive properties.

  3. 3D active stabilization system with sub-micrometer resolution.

    Directory of Open Access Journals (Sweden)

    Olli Kursu

    Full Text Available Stable positioning between a measurement probe and its target from sub- to few micrometer scales has become a prerequisite in precision metrology and in cellular level measurements from biological tissues. Here we present a 3D stabilization system based on an optoelectronic displacement sensor and custom piezo-actuators driven by a feedback control loop that constantly aims to zero the relative movement between the sensor and the target. We used simulations and prototyping to characterize the developed system. Our results show that 95% attenuation of movement artifacts is achieved at 1 Hz with stabilization performance declining to ca. 70% attenuation at 10 Hz. Stabilization bandwidth is limited by mechanical resonances within the displacement sensor that occur at relatively low frequencies, and are attributable to the sensor's high force sensitivity. We successfully used brain derived micromotion trajectories as a demonstration of complex movement stabilization. The micromotion was reduced to a level of ∼1 µm with nearly 100 fold attenuation at the lower frequencies that are typically associated with physiological processes. These results, and possible improvements of the system, are discussed with a focus on possible ways to increase the sensor's force sensitivity without compromising overall system bandwidth.

  4. Stability and response bounds of non-conservative linear systems

    DEFF Research Database (Denmark)

    Kliem, Wolfhard; Pommer, Christian

    2004-01-01

    This paper develops a stability theorem and response bounds for non-conservative systems of the form MX + (D + G)x + (K + N)x = f(t), with hermitian positive-definite matrices M, D and K, and skew-hermitian matrices G and N. To this end, we first find a Lyapunov function by solving the Lyapunov m...

  5. Stability field diagrams for Ln–O–Cl systems

    Indian Academy of Sciences (India)

    Permanent link: http://www.ias.ac.in/article/fulltext/boms/039/03/0603-0611. Keywords. Predominance area diagram; Kellogg diagram; lanthanide oxychloride; rare-earth mineral processing; thermodynamic properties. Abstract. Isothermal stability field diagrams for Ln−O−Cl systems (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, ...

  6. Stability and control of wind farms in power systems

    DEFF Research Database (Denmark)

    Jauch, Clemens

    The Ph.D. project ‘Stability and Control of Wind Farms in Power Systems’ deals with some selected problems related to wind power in power systems. With increasing wind power penetration, wind turbines substitute the power production of conventional powerplants. Therefore, wind turbines also have ...

  7. Harmonics and voltage stability analysis in power systems including ...

    Indian Academy of Sciences (India)

    These non-sinusoidal quantities can create serious harmonic distortions in transmission and distribution systems. In this paper, harmonic generation of a static VAR compensator with thyristor-controlled reactor and effects of the harmonics on steady-state voltage stability are examined for various operational conditions.

  8. 3D Active Stabilization System with Sub-Micrometer Resolution

    Science.gov (United States)

    Rahkonen, Timo; Vähäsöyrinki, Mikko

    2012-01-01

    Stable positioning between a measurement probe and its target from sub- to few micrometer scales has become a prerequisite in precision metrology and in cellular level measurements from biological tissues. Here we present a 3D stabilization system based on an optoelectronic displacement sensor and custom piezo-actuators driven by a feedback control loop that constantly aims to zero the relative movement between the sensor and the target. We used simulations and prototyping to characterize the developed system. Our results show that 95 % attenuation of movement artifacts is achieved at 1 Hz with stabilization performance declining to ca. 70 % attenuation at 10 Hz. Stabilization bandwidth is limited by mechanical resonances within the displacement sensor that occur at relatively low frequencies, and are attributable to the sensor's high force sensitivity. We successfully used brain derived micromotion trajectories as a demonstration of complex movement stabilization. The micromotion was reduced to a level of ∼1 µm with nearly 100 fold attenuation at the lower frequencies that are typically associated with physiological processes. These results, and possible improvements of the system, are discussed with a focus on possible ways to increase the sensor's force sensitivity without compromising overall system bandwidth. PMID:22900045

  9. Robust stabilization of nonlinear systems by quantized and ternary control

    NARCIS (Netherlands)

    Persis, Claudio De

    2009-01-01

    Results on the problem of stabilizing a nonlinear continuous-time minimum-phase system by a finite number of control or measurement values are presented. The basic tool is a discontinuous version of the so-called semi-global backstepping lemma. We derive robust practical stabilizability results by

  10. Robust Stability Analysis of Nonlinear Switched Systems with Filippov Solutions

    DEFF Research Database (Denmark)

    Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal

    2012-01-01

    This paper addresses the stability problem of a class of nonlinear switched systems with partitioned state-space and state-dependent switching. In lieu of the Caratheodory solutions, the general Filippov solutions are considered. This encapsulates solutions with infinite switching in finite time....... which provides sufficient means to construct the corresponding Lyapunov functions via available semi-definite programming techniques....

  11. Asymptotic stability results for retarded differential systems | Igobi ...

    African Journals Online (AJOL)

    ... matrices are used in formulating a Lyapunov functional. The introduction of convex set segment of a symmetric matrix is explored to establish boundedness of the first derivative of the formulated functional. The integral-differential equation is utilized in computing the maximum delay interval for the system to attain stability.

  12. Stability Analysis for Multi-Parameter Linear Periodic Systems

    DEFF Research Database (Denmark)

    Seyranian, A.P.; Solem, Frederik; Pedersen, Pauli

    1999-01-01

    This paper is devoted to stability analysis of general linear periodic systems depending on real parameters. The Floquet method and perturbation technique are the basis of the development. We start out with the first and higher-order derivatives of the Floquet matrix with respect to problem...

  13. Harmonics and voltage stability analysis in power systems including

    Indian Academy of Sciences (India)

    In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of significant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious harmonic ...

  14. Harmonics and voltage stability analysis in power systems including ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Abstract. In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of significant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious har-.

  15. Stability field diagrams for Ln–O–Cl systems

    Indian Academy of Sciences (India)

    Abstract. Isothermal stability field diagrams for Ln−O−Cl systems (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy,. Ho, Er, Tm, Yb) are developed by taking partial pressures of volatile components oxygen and chlorine as variables. Thermodynamic properties of all the oxides and trichlorides (LnCl3) are available in the literature.

  16. Stochastic stability of four-wheel-steering system

    International Nuclear Information System (INIS)

    Huang Dongwei; Wang Hongli; Zhu Zhiwen; Feng Zhang

    2007-01-01

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

  17. Power System Transient Stability Analysis through a Homotopy Analysis Method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shaobu; Du, Pengwei; Zhou, Ning

    2014-04-01

    As an important function of energy management systems (EMSs), online contingency analysis plays an important role in providing power system security warnings of instability. At present, N-1 contingency analysis still relies on time-consuming numerical integration. To save computational cost, the paper proposes a quasi-analytical method to evaluate transient stability through time domain periodic solutions’ frequency sensitivities against initial values. First, dynamic systems described in classical models are modified into damping free systems whose solutions are either periodic or expanded (non-convergent). Second, because the sensitivities experience sharp changes when periodic solutions vanish and turn into expanded solutions, transient stability is assessed using the sensitivity. Third, homotopy analysis is introduced to extract frequency information and evaluate the sensitivities only from initial values so that time consuming numerical integration is avoided. Finally, a simple case is presented to demonstrate application of the proposed method, and simulation results show that the proposed method is promising.

  18. Stabilizing constrained chaotic system using a symplectic psuedospectral method

    Science.gov (United States)

    Peng, Haijun; Wang, Xinwei; Shi, Boyang; Zhang, Sheng; Chen, Biaosong

    2018-03-01

    The problem of controlling chaotic systems has drawn much attention in the last two decades. However, the controlled system may be subjected to complicated constraints and few researches on controlling chaos take constraints into consideration. Therefore, the stabilization of constrained chaotic system is solved under the frame of nonlinear optimal control in this paper. A symplectic pseudospectral method based on qusilinearizaiton techniques and the parametric variational principle is developed to solve constrained nonlinear optimal control problems with arbitrary Lagrange-type cost functional. At the beginning of the proposed method, the original nonlinear optimal control problem is converted into a series of linear-quadratic constrained optimal control problems. Then each of the converted linear quadratic problems is transformed into a standard linear complementarity problem. The proposed method is successfully applied to stabilizing constrained chaotic systems around an unstable equilibrium point or an unstable periodic orbit. Numerical simulations demonstrate that the developed method is effective and efficient, and constraints are strictly satisfied.

  19. Importance of stability study of continuous systems for ethanol production.

    Science.gov (United States)

    Paz Astudillo, Isabel Cristina; Cardona Alzate, Carlos Ariel

    2011-01-10

    Fuel ethanol industry presents different problems during bioreactors operation. One of them is the unexpected variation in the output ethanol concentration from the bioreactor or a drastic fall in the productivity. In this paper, a compilation of concepts and relevant results of several experimental and theoretical studies about dynamic behavior of fermentation systems for bioethanol production with Saccharomyces cerevisiae and Zymomonas mobilis is done with the purpose of understanding the stability phenomena that could affect the productivity of industries producing fuel ethanol. It is shown that the design of high scale biochemical processes for fuel ethanol production must be done based on stability studies. © 2010 Elsevier B.V. All rights reserved.

  20. Harmonics and voltage stability analysis in power systems including ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    1. Introduction. It is not only required to meet the demand for electrical energy but also to improve its quality. .... It is necessary to pay attention to energy system stability in the planning, management, and control of electrical ... where k ∈ {m, m + 1,... ,n} and n is total number of the buses in the system. F(h) r,k and F(h) i,k.

  1. Adaptive Stabilization for Nonholonomic Systems with Unknown Time Delays

    Directory of Open Access Journals (Sweden)

    Yuanyuan Wu

    2013-01-01

    Full Text Available This paper presents an adaptive control strategy for a class of nonholonomic systems in chained form with virtual control coefficients, nonlinear uncertainties, and unknown time delays. State scaling technique and backstepping recursive approach are applied to design a nonlinear state feedback controller, which can guarantee the stabilization of the closed-loop systems. The simulation results are provided to show the effectiveness of the proposed method.

  2. QFT Framework for Robust Tuning of Power System Stabilizers

    DEFF Research Database (Denmark)

    Alavi, Seyyed Mohammad Mahdi; Izadi-Zamanabadi, Roozbeh

    2005-01-01

    This paper discusses the use of conventional quantitative feedback design for Power System Stabilizer (PSS). An appropriate control structure of the PSS that is directly applicable to PSS, is described. Two desired performances are also proposed in order to achieve an overall improvement in damping...... and robustness. The efficiency of the proposed method is demonstrated on Single Machine Infinite Bus (SMIB) power system with level of uncertainty....

  3. Chaotic invasive weed optimization algorithm with application to parameter estimation of chaotic systems

    International Nuclear Information System (INIS)

    Ahmadi, Mohamadreza; Mojallali, Hamed

    2012-01-01

    Highlights: ► A new meta-heuristic optimization algorithm. ► Integration of invasive weed optimization and chaotic search methods. ► A novel parameter identification scheme for chaotic systems. - Abstract: This paper introduces a novel hybrid optimization algorithm by taking advantage of the stochastic properties of chaotic search and the invasive weed optimization (IWO) method. In order to deal with the weaknesses associated with the conventional method, the proposed chaotic invasive weed optimization (CIWO) algorithm is presented which incorporates the capabilities of chaotic search methods. The functionality of the proposed optimization algorithm is investigated through several benchmark multi-dimensional functions. Furthermore, an identification technique for chaotic systems based on the CIWO algorithm is outlined and validated by several examples. The results established upon the proposed scheme are also supplemented which demonstrate superior performance with respect to other conventional methods.

  4. Adaptive Fuzzy Gain of Power System Stabilizer to Improve the Global Stability

    OpenAIRE

    Mekhanet, Mohammed; Mokrani, Lakhdar; Ameur, Aissa; Attia, Yacine

    2016-01-01

    The lead-lag power system stabilizer has several parameters to be optimized.In fact, the number of these latter increases with the number of generators constituting the multi-machine system.In this work, we propose anew approach of an adaptive and robust PSS; it achieves encouraging results by adjusting the gain using fuzzy logic and in the same time we use the same PSSs for each machine. In the first place, we could check that the gain is among the most critical parameters of the lead lag PS...

  5. Ecological networks. On the structural stability of mutualistic systems.

    Science.gov (United States)

    Rohr, Rudolf P; Saavedra, Serguei; Bascompte, Jordi

    2014-07-25

    In theoretical ecology, traditional studies based on dynamical stability and numerical simulations have not found a unified answer to the effect of network architecture on community persistence. Here, we introduce a mathematical framework based on the concept of structural stability to explain such a disparity of results. We investigated the range of conditions necessary for the stable coexistence of all species in mutualistic systems. We show that the apparently contradictory conclusions reached by previous studies arise as a consequence of overseeing either the necessary conditions for persistence or its dependence on model parameterization. We show that observed network architectures maximize the range of conditions for species coexistence. We discuss the applicability of structural stability to study other types of interspecific interactions. Copyright © 2014, American Association for the Advancement of Science.

  6. Stability Analysis of Periodic Systems by Truncated Point Mappings

    Science.gov (United States)

    Guttalu, R. S.; Flashner, H.

    1996-01-01

    An approach is presented deriving analytical stability and bifurcation conditions for systems with periodically varying coefficients. The method is based on a point mapping(period to period mapping) representation of the system's dynamics. An algorithm is employed to obtain an analytical expression for the point mapping and its dependence on the system's parameters. The algorithm is devised to derive the coefficients of a multinominal expansion of the point mapping up to an arbitrary order in terms of the state variables and of the parameters. Analytical stability and bifurcation condition are then formulated and expressed as functional relations between the parameters. To demonstrate the application of the method, the parametric stability of Mathieu's equation and of a two-degree of freedom system are investigated. The results obtained by the proposed approach are compared to those obtained by perturbation analysis and by direct integration which we considered to the "exact solution". It is shown that, unlike perturbation analysis, the proposed method provides very accurate solution even for large valuesof the parameters. If an expansion of the point mapping in terms of a small parameter is performed the method is equivalent to perturbation analysis. Moreover, it is demonstrated that the method can be easily applied to multiple-degree-of-freedom systems using the same framework. This feature is an important advantage since most of the existing analysis methods apply mainly to single-degree-of-freedom systems and their extension to higher dimensions is difficult and computationally cumbersome.

  7. Asymptotic stabilization of nonlinear systems using state feedback

    International Nuclear Information System (INIS)

    D'Attellis, Carlos

    1990-01-01

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

  8. An Effective Distributed Model for Power System Transient Stability Analysis

    Directory of Open Access Journals (Sweden)

    MUTHU, B. M.

    2011-08-01

    Full Text Available The modern power systems consist of many interconnected synchronous generators having different inertia constants, connected with large transmission network and ever increasing demand for power exchange. The size of the power system grows exponentially due to increase in power demand. The data required for various power system applications have been stored in different formats in a heterogeneous environment. The power system applications themselves have been developed and deployed in different platforms and language paradigms. Interoperability between power system applications becomes a major issue because of the heterogeneous nature. The main aim of the paper is to develop a generalized distributed model for carrying out power system stability analysis. The more flexible and loosely coupled JAX-RPC model has been developed for representing transient stability analysis in large interconnected power systems. The proposed model includes Pre-Fault, During-Fault, Post-Fault and Swing Curve services which are accessible to the remote power system clients when the system is subjected to large disturbances. A generalized XML based model for data representation has also been proposed for exchanging data in order to enhance the interoperability between legacy power system applications. The performance measure, Round Trip Time (RTT is estimated for different power systems using the proposed JAX-RPC model and compared with the results obtained using traditional client-server and Java RMI models.

  9. The stability of the Manual Ability Classification System over time.

    Science.gov (United States)

    Öhrvall, Ann-Marie; Krumlinde-Sundholm, Lena; Eliasson, Ann-Christin

    2014-02-01

    To evaluate the stability over time of the Manual Ability Classification System (MACS) levels. The study group comprised 1267 children with cerebral palsy (746 males, 521 females) who were followed from 2005 to 2010 with two or more registered MACS classifications rated at least 1 year apart. Thirty-five percent of the children (n=445) had four MACS registrations. The children were between 4 and 17 years old at their first rating, The stability over time was also compared between children who were younger (4y of age) or older (≥10y) at the time of their first classification. An excellent stability was found between two ratings at 1-year intervals with an intraclass correlation coefficient (ICC) of 0.97 (95% CI 0.97-0.97) and 82% agreement (n=1267). The stability was also excellent for two ratings performed 3 to 5 years apart (ICC 0.96; 95% CI 0.95-0.97) with an agreement of 78% (n=445). Across four ratings, 70% of the children remained at the same level. The results were similar for younger and older children, indicating that stability was not influenced by age. This study provides evidence that MACS levels are stable over time and that the classification has predictive value. © 2013 Mac Keith Press.

  10. 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

  11. Fault Tolerant Emergency Control to Preserve Power System Stability

    DEFF Research Database (Denmark)

    Pedersen, Andreas Søndergaard; Richter, Jan H.; Tabatabaeipour, Mojtaba

    2016-01-01

    This paper introduces a method for fault-masking and system reconfiguration in power transmission systems. The paper demonstrates how faults are handled by reconfiguring remaining controls through utilisation of wide-area measurement in real time. It is shown how reconfiguration can be obtained...... using a virtual actuator concept, which covers Lure-type systems. The paper shows the steps needed to calculate a virtual actuator, which relies on the solution of a linear matrix inequality. The solution is shown to work with existing controls by adding a compensation signal. Simulation results...... of a benchmark system show ability of the reconfiguration to maintain stability...

  12. An image stabilization optical system using deformable freeform mirrors.

    Science.gov (United States)

    Hao, Qun; Cheng, Xuemin; Kang, Jiqiang; Jiang, Yuhua

    2015-01-15

    An image stabilization optical system using deformable freeform mirrors is proposed that enables the ray sets to couple dynamically in the object and image space. It aims to correct image blurring and degradation when there is relative movement between the imaging optical axis and the object. In this method, Fermat's principle and matrix methods are used to describe the optical path of the entire optical system with a shift object plane and a fixed corresponding image plane in the carrier coordinate system. A constant optical path length is determined for each ray set, so the correspondence between the object and the shift free image point is used to calculate the solution to the points on the surface profile of the deformable mirrors (DMs). Off-axis three-mirror anastigmats are used to demonstrate the benefits of optical image stabilization with one- and two-deformable mirrors.

  13. Stability of detecting system using NaI(Tl)

    International Nuclear Information System (INIS)

    Zhuo Yunshang; Lei Zhangyun; Zen Yu; Gong Hua

    1996-01-01

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

  14. On the stability and collisions in triple stellar systems

    Science.gov (United States)

    He, Matthias Y.; Petrovich, Cristobal

    2018-02-01

    A significant fraction of main-sequence (MS) stars are part of a triple system. We study the long-term stability and dynamical outcomes of triple stellar systems using a large number of long-term direct N-body integrations with relativistic precession. We find that the previously proposed stability criteria by Eggleton & Kiseleva and Mardling & Aarseth predict the stability against ejections reasonably well for a wide range of parameters. Assuming that the triple stellar systems follow orbital and mass distributions from FGK binary stars in the field, we find that ˜ 1 per cent and ˜ 0.5 per cent of the triple systems lead to a direct head-on collision (impact velocity ˜ escape velocity) between MS stars and between a MS star and a stellar-mass compact object, respectively. We conclude that triple interactions are the dominant channel for direct collisions involving a MS star in the field with a rate of one event every ˜100 years in the Milky Way. We estimate that the fraction of triple systems that form short-period binaries is up to ˜ 23 per cent with only up to ˜ 13 per cent being the result of three-body interactions with tidal dissipation, which is consistent with previous work using a secular code.

  15. Percolation-based risk index for pathogen invasion: application to soilborne disease in propagation systems.

    Science.gov (United States)

    Poggi, S; Neri, F M; Deytieux, V; Bates, A; Otten, W; Gilligan, C A; Bailey, D J

    2013-10-01

    Propagation systems for seedling growth play a major role in agriculture, and in notable cases (such as organic systems), are under constant threat from soil and seedborne fungal plant pathogens such as Rhizoctonia solani or Pythium spp. Yet, to date little is known that links the risk of disease invasion to the host density, which is an agronomic characteristic that can be readily controlled. We introduce here, for the first time in an agronomic system, a percolation framework to analyze the link. We set up an experiment to study the spread of the ubiquitous fungus R. solani in replicated propagation systems with different planting densities, and fit a percolation-based epidemiological model to the data using Bayesian inference methods. The estimated probability of pathogen transmission between infected and susceptible plants is used to calculate the risk of invasion. By comparing the transmission probability and the risk values obtained for different planting densities, we are able to give evidence of a nonlinear relationship between disease invasion and the inter-plant spacing, hence to demonstrate the existence of a spatial threshold for epidemic invasion. The implications and potential use of our methods for the evaluation of disease control strategies are discussed.

  16. Stress-gradient hypothesis explains susceptibility to Bromus tectorum invasion and community stability in North America's semi-arid Artemisia tridentata wyomingensis ecosystems

    Science.gov (United States)

    Reisner, Michael D.; Doescher, Paul S.; Pyke, David A.

    2015-01-01

    Questions: (1) What combinations of overlapping water and heat stress and herbivory disturbance gradients are associated with shifts in interactions between Artemisia tridentata subsp. wyomingensis (Artemisia) and herbaceous beneficiary species? (2) Do interactions between Artemisia and beneficiaries shift from competition to facilitation with increasing stress-disturbance where facilitation and competition are most frequent and strongest at the highest and lowest levels, respectively? (3) Do such relationships differ for native and non-native beneficiaries? (4) What are the implications of any observed shifts in interactions between community compositional stability in space and susceptibility to invasion?

  17. Stability Analysis of a Helicopter with an External Slung Load System

    OpenAIRE

    Thanapalan, Kary

    2016-01-01

    This paper describes the stability analysis of a helicopter with an underslung external load system. The Lyapunov second method is considered for the stability analysis. The system is considered as a cascade connection of uncertain nonlinear system. The stability analysis is conducted to ensure the stabilisation of the helicopter system and the positioning of the underslung load at hover condition. Stability analysis and numerical results proved that if desired condition for the stability is ...

  18. An extremely high stability cooling system for planet hunter

    Science.gov (United States)

    l’Allemand, J. L. Lizon a.; Becerril, S.; Mirabet, E.

    2017-12-01

    The detection of exoplanets is done by measuring very tiny periodical variations of the radial velocity of the parent star. Extremely stable spectrographs are required in order to enhance the wavelength variations of the spectral lines due to Doppler effect. CARMENES is the new high-resolution, high-stability spectrograph built for the 3.5 m telescope at the Calar Alto Observatory (CAHA, Almería, Spain) by a consortium formed by German and Spanish institutions. This instrument is composed of two separated spectrographs: VIS channel (550-1050 nm) and NIR channel (950-1700 nm). The NIR-channel spectrograph’s has been built under the responsibility of the Instituto de Astrofísica de Andalucía (IAA-CSIC). It has been manufactured, assembled, integrated and verified in the last two years, delivered in fall 2015 and commissioned in December 2015. Beside the various opto-mechanical challenges, the cooling system was one of the most demanding sub-systems of the NIR channel. Due to the highly demanding requirements applicable in terms of stability, this system arises as one of the core systems to provide outstanding stability to the channel at an operating temperature finally fixed at 140 K. Really at the edge of the state-of-the-art, the Cooling System is able to provide to the cold mass (∼1 Ton) better thermal stability than few hundredths of a degree over 24 hours (goal: 0.01K/day). The present paper describes the main technical approach, which has been taken in order to reach this very ambitious performance.

  19. Do alien species matter? Impacts of invasions in Indian freshwater systems and challenges in management

    Directory of Open Access Journals (Sweden)

    Murugan Muralidharan

    2017-06-01

    Full Text Available Alongside anthropogenic activities and habitat destruction, invasions are regarded as one of the most influential components of global change. India as a growing economy and rapidly developing nation has been constantly engaged in infrastructure development which consequently has led to depletion of natural resources and declining quality of habitats aquatic systems in particular. Invasions that have established from the introductions in past during the colonial era and recently spread species are great challenges that hamper survival of aquatic resources. As of 2015, 20 plants, one mollusc and 37 fishes are known to have naturalized in Indian water bodies. Awareness on the invasive species along with detailed information on the ecosystem-wide impacts is essential for management.

  20. Stereotactic minimally invasive tubular retractor system for deep brain lesions.

    Science.gov (United States)

    Greenfield, Jeffrey P; Cobb, William S; Tsouris, A John; Schwartz, Theodore H

    2008-10-01

    Deep-seated supratentorial intraparenchymal and intraventricular brain lesions can be difficult to access without causing significant trauma to the overlying cortex and intervening white matter tracts. Traditional brain retractors use multiple blades, which do not exert pressure in an equally distributed fashion. Tubular retractors offer an advantage. Although a commercially available frame-based tubular retractor system is on the market (COMPASS; Compass, Inc., Rochester, MN), we modified existing off-the-shelf equipment at our institution into a frameless tubular brain retractor. We used 14- to 22-mm METRx (Medtronic, Minneapolis, MN) tubular retractors in combination with a frameless stereotactic navigation system to remove 10 deep lesions. Histological findings included 6 periventricular metastases, 1 insular glioblastoma multiforme, 1 periventricular glioblastoma multiforme, 1 intraventricular meningioma, and 1 hippocampal cavernous malformation. Radiographic gross total resection was achieved in all patients. One patient experienced a transient worsening of an existing preoperative Wernicke's aphasia; otherwise, there were no intra- or postoperative complications. One patient with radiographic gross total resection of a metastatic lesion experienced a local recurrence of disease, requiring stereotactic radiosurgery. A frameless stereotactic tubular retractor system for deep brain lesions can be assembled with equipment already available at many institutions. Use of this system can decrease incision and craniotomy size, decrease retractor-induced trauma to overlying cortex, and help prevent damage to underlying white matter tracts.

  1. Stability of Rotor Systems: A Complex Modelling Approach

    DEFF Research Database (Denmark)

    Kliem, Wolfhard; Pommer, Christian; Stoustrup, Jakob

    1996-01-01

    with the results of the classical approach using Rayleighquotients. Several rotor systems are tested: a simple Laval rotor, a Laval rotor with additional elasticity and damping in thr bearings, and a number of rotor systems with complex symmetric 4x4 randomly generated matrices.......A large class of rotor systems can be modelled by a complex matrix differential equation of secondorder. The angular velocity of the rotor plays the role of a parameter. We apply the Lyapunov matrix equation in a complex setting and prove two new stability results which are compared...

  2. Optimal Subinterval Selection Approach for Power System Transient Stability Simulation

    Directory of Open Access Journals (Sweden)

    Soobae Kim

    2015-10-01

    Full Text Available Power system transient stability analysis requires an appropriate integration time step to avoid numerical instability as well as to reduce computational demands. For fast system dynamics, which vary more rapidly than what the time step covers, a fraction of the time step, called a subinterval, is used. However, the optimal value of this subinterval is not easily determined because the analysis of the system dynamics might be required. This selection is usually made from engineering experiences, and perhaps trial and error. This paper proposes an optimal subinterval selection approach for power system transient stability analysis, which is based on modal analysis using a single machine infinite bus (SMIB system. Fast system dynamics are identified with the modal analysis and the SMIB system is used focusing on fast local modes. An appropriate subinterval time step from the proposed approach can reduce computational burden and achieve accurate simulation responses as well. The performance of the proposed method is demonstrated with the GSO 37-bus system.

  3. Dynamic stabilization for L4-5 spondylolisthesis: comparison with minimally invasive transforaminal lumbar interbody fusion with more than 2 years of follow-up.

    Science.gov (United States)

    Kuo, Chao-Hung; Chang, Peng-Yuan; Wu, Jau-Ching; Chang, Hsuan-Kan; Fay, Li-Yu; Tu, Tsung-Hsi; Cheng, Henrich; Huang, Wen-Cheng

    2016-01-01

    OBJECTIVE In the past decade, dynamic stabilization has been an emerging option of surgical treatment for lumbar spondylosis. However, the application of this dynamic construct for mild spondylolisthesis and its clinical outcomes remain uncertain. This study aimed to compare the outcomes of Dynesys dynamic stabilization (DDS) with minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) for the management of single-level spondylolisthesis at L4-5. METHODS This study retrospectively reviewed 91 consecutive patients with Meyerding Grade I spondylolisthesis at L4-5 who were managed with surgery. Patients were divided into 2 groups: DDS and MI-TLIF. The DDS group was composed of patients who underwent standard laminectomy and the DDS system. The MI-TLIF group was composed of patients who underwent MI-TLIF. Clinical outcomes were evaluated by visual analog scale for back and leg pain, Oswestry Disability Index, and Japanese Orthopaedic Association scores at each time point of evaluation. Evaluations included radiographs and CT scans for every patient for 2 years after surgery. RESULTS A total of 86 patients with L4-5 spondylolisthesis completed the follow-up of more than 2 years and were included in the analysis (follow-up rate of 94.5%). There were 64 patients in the DDS group and 22 patients in the MI-TLIF group, and the overall mean follow-up was 32.7 months. Between the 2 groups, there were no differences in demographic data (e.g., age, sex, and body mass index) or preoperative clinical evaluations (e.g., visual analog scale back and leg pain, Oswestry Disability Index, and Japanese Orthopaedic Association scores). The mean estimated blood loss of the MI-TLIF group was lower, whereas the operation time was longer compared with the DDS group (both p spondylolisthesis at L4-5. DDS might be an alternative to standard arthrodesis in mild lumbar spondylolisthesis. However, unlike fusion, dynamic implants have issues of wearing and loosening in the long term

  4. Stabilization of Multiple Unstable Modes for Small-Scale Inverter-Based Power Systems with Impedance-Based Stability Analysis

    DEFF Research Database (Denmark)

    Yoon, Changwoo; Wang, Xiongfei; Bak, Claus Leth

    2015-01-01

    This paper investigates the harmonic stability of small-scale inverter-based power systems. A holistic procedure to assess the contribution of each inverter to the system stability is proposed by means of using the impedancebased stability criterion. Multiple unstable modes can be identified step......-by-step coming from the interactions among inverters and passive networks. Compared to the conventional system stability analysis, the approach is easy to implement and avoids the effect of potential unstable system dynamics on the impedance ratio derived for the stability analysis. PSCAD/ EMTDC simulations...... of a Cigre LV network Benchmark system with multiple renewable energy sources are carried out. The results confirm the validity of the proposed approach....

  5. Research on Handling Stability of Steering-by-wire System

    Directory of Open Access Journals (Sweden)

    Yuan Ying

    2017-01-01

    Full Text Available The main function of steer-by-wire (SBW system are improving steering characteristics, security and stability of the vehicle. In this paper, the variable steering ratio of SBW system is analyzed, and the method of steering ratio based on fuzzy control and neural network are researched. In order to solve the actual working condition, the wheel angle may not reach the expected value, this paper establishes a twodegree-of-freedom (2-DOF vehicle model, and a Matlab/Simulink simulation model, in which a control strategy based on PID controller is put forward to control the front wheel steering angle. Simulation results show that proposed control strategy based on fuzzy neural network can effectively reduce lateral deviation and improve the handling stability and comfortability of the vehicle.

  6. Linking the distribution of an invasive amphibian (Rana catesbeiana) to habitat conditions in a managed river system in northern California.

    Science.gov (United States)

    Terra Fuller; Karen Pope; Donald Ashton; Hartwell Welsh

    2010-01-01

    Extensive modifications of river systems have left floodplains some of the most endangered ecosystems in the world and made restoration of these systems a priority. Modified river ecosystems frequently support invasive species to the detriment of native species. Rana catesbeiana (American bullfrog) is an invasive amphibian that thrives in modified...

  7. An alternative soil nailing system for slope stabilization: Akarpiles

    Science.gov (United States)

    Lim, Chun-Lan; Chan, Chee-Ming

    2017-11-01

    This research proposes an innovative solution for slope stabilization with less environmental footprint: AKARPILES. In Malaysia, landslide has become common civil and environmental problems that cause impacts to the economy, safety and environment. Therefore, effective slope stabilization method helps to improve the safety of public and protect the environment. This study focused on stabilizing surfacial slope failure. The idea of AKARPILES was generated from the tree roots system in slope stabilization. After the piles are installed in the slope and intercepting the slip plane, grout was pumped in and discharged through holes on the piles. The grout then filled the pores in the soil with random flow within the slip zone. SKW mixture was used to simulate the soil slope. There were two designs being proposed in this study and the prototypes were produced by a 3D printer. Trial mix of the grout was carried out to obtain the optimum mixing ratio of bentonite: cement: water. A series of tests were conducted on the single-pile-reinforced slope under vertical slope crest loading condition considering different slope gradients and nail designs. Parameters such as ultimate load, failure time and failure strain were recorded and compared. As comparison with the unreinforced slope, both designs of AKARPILES showed better but different performances in the model tests.

  8. 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.

  9. Stability and bifurcation for Marchuk's model of an immune system

    Science.gov (United States)

    Marzuki, Ira Syazwani Mohamad; Roslan, Ummu'Atiqah Mohd

    2017-08-01

    The investigation of an immune system has long been and will continue to be one of dominant themes in both ecology and biology due to its importance. In this paper, we consider Marchuk's model of an immune system where this model is governed by a system of three differential equations with time. This model has two equilibrium states which are healthy state and chronic state. It is healthy state when the antigen reproduction is small while chronic state is when antigen reproduction rate is large. The objectives of this paper are to analyse the stability of this model, to summarize this stability using bifurcation diagram and to discuss interaction between the healthy and chronic states at stationary solution. The methods involved are stability theory and bifurcation theory. Our results show that healthy states are saddle and only one chronic state is asymptotically stable for a region of parameter considered. For the bifurcation's case, as we increase the value of a parameter in this model, the chronic state shows that there are increment in the number of antigen, plasma cell and the antibody production.

  10. Modeling and Stability Analysis of Wedge Clutch System

    Directory of Open Access Journals (Sweden)

    Jian Yao

    2014-01-01

    Full Text Available A wedge clutch with unique features of self-reinforcement and small actuation force was designed. Its self-reinforcement feature, associated with different factors such as the wedge angle and friction coefficient, brings different dynamics and unstable problem with improper parameters. To analyze this system, a complete mathematical model of the actuation system is built, which includes the DC motor, the wedge mechanism, and the actuated clutch pack. By considering several nonlinear factors, such as the slip-stick friction and the contact or not of the clutch plates, the system is piecewise linear. Through the stability analysis of the linearized system in clutch slipping phase, the stable condition of the designed parameters is obtained as α>arctan⁡(μc. The mathematical model of the actuation system is validated by prototype testing. And with the validated model, the system dynamics in both stable and unstable conditions is investigated and discussed in engineering side.

  11. Stabilization of Electromagnetic Suspension System Behavior by Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Abbas Najar Khoda Bakhsh

    2012-07-01

    Full Text Available Electromagnetic suspension system with a nonlinear and unstable behavior, is used in maglev trains. In this paper a linear mathematical model of system is achieved and the state feedback method is used to improve the system stability. The control coefficients are tuned by two different methods, Riccati and a new method based on Genetic algorithm. In this new proposed method, we use Genetic algorithm to achieve the optimum values of control coefficients. The results of the system simulation by Matlab indicate the effectiveness of new proposed system. When a new reference of air gap is needed or a new external force is added, the proposed system could omit the vibration and shake of the train coupe and so, passengers feel more comfortable.

  12. Multiple myeloma invasion of the central nervous system

    Directory of Open Access Journals (Sweden)

    Marjanović Slobodan

    2012-01-01

    Full Text Available Introduction. Multiple myeloma (MM is characterized by the presence of neoplastic proliferating plasma cells. The tumor is generally restricted to the bone marrow. The most common complications include renal insufficiency, hypercalcemia, anemia and reccurent infections. The spectrum of MM neurological complications is diverse, however, involvement of MM in the cerebrospinal fluid (CSF and leptomeningeal infiltration are rare considered. In about 1% of the cases, the disease affects the central nervous system (CNS and presents itself in the form of localized intraparenchymal lesions, solitary cerebral plasmocytoma or CNS myelomatosis (LMM. Case report. We presented the clinical course of a 55-year-old man with MM and LMM proven by malignant plasma cells in the CSF, hospitalized with the pain in the thoracic spine. His medical history was uneventful. There had been no evidence of mental or neurological impairment prior to the seizures. Physical examination showed no abnormalities. After a complete staging, the diagnosis of MM type biclonal gammopathia IgG lambda and free lambda light chains in the stage III was confirmed. The treatment started with systemic chemotherapy (with vincristine, doxorubicin plus high-dose dexamethasone - VAD protocol, radiotherapy and bisphosphonate. The patient developed weakness, nausea, febrility, dispnea, bilateral bronchopneumonia, acute renal insufficiency, confusions, headaches and soon thereafter sensomotor aphasias and right hemiparesis. The patient was treated with the adequate therapy including one hemodyalisis. His neurological status was deteriorated, so Multislice Computed Tomography (MSCT of the head was performed and the findings were normal. Analysis of CSF showed pleocytosis, 26 elements/ mL and increased concentrations of proteins. Cytological analysis revealed an increased number of plasma cells (29%. Electrophoretic analysis of proteins disclosed the existance of monoclonal components in the serum

  13. Stability and Control of Wind Farms in Power Systems

    DEFF Research Database (Denmark)

    Jauch, Clemens

    The Ph.D. project ‘Stability and Control of Wind Farms in Power Systems' deals with some selected problems related to wind power in power systems. With increasing wind power penetration, wind turbines substitute the power production of conventional power plants. Therefore, wind turbines also have...... to take over the power system stabilisation and control tasks, that were traditionally carried out by conventional power plants. Out of the many aspects related to this problem, this project focuses on transient fault ride-through and power system stabilisation. The selection of turbine types considered...... that were in force, or published as drafts, at the time, and scientific literature related to the topic, are studied. The project is based on simulations of wind turbines in a power system simulations tool. Some of the models used in this project were readily available prior to the project; the development...

  14. Investigating the Impact of Wind Turbines on Distribution System Stability

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Rishabh; Zhang, Yingchen; Hodge, Bri-Mathias

    2016-12-12

    Modern wind turbines utilize power electronic converters to regulate their output and optimize their performance. Their impact on the distribution system is not as well understood as for transmission system. The novelty of this work is in studying the impact of wind turbines given its proximity to faults or severe voltage events, and the influence on system stability given its location relative to the substation (representing the conventional grid). This paper presents the frequency and voltage swing plots for various study scenarios. The responses are analyzed two fold - Steady state operation, and performance given a fault or voltage events occurs in the system. The findings are presented, with crucial differences from transmission systems highlighted.

  15. Stability Analysis of a Reaction-Diffusion System Modeling Atherogenesis

    KAUST Repository

    Ibragimov, Akif

    2010-01-01

    This paper presents a linear, asymptotic stability analysis for a reaction-diffusionconvection system modeling atherogenesis, the initiation of atherosclerosis, as an inflammatory instability. Motivated by the disease paradigm articulated by Ross, atherogenesis is viewed as an inflammatory spiral with a positive feedback loop involving key cellular and chemical species interacting and reacting within the intimal layer of muscular arteries. The inflammatory spiral is initiated as an instability from a healthy state which is defined to be an equilibrium state devoid of certain key inflammatory markers. Disease initiation is studied through a linear, asymptotic stability analysis of a healthy equilibrium state. Various theorems are proved, giving conditions on system parameters guaranteeing stability of the health state, and a general framework is developed for constructing perturbations from a healthy state that exhibit blow-up, which are interpreted as corresponding to disease initiation. The analysis reveals key features that arterial geometry, antioxidant levels, and the source of inflammatory components (through coupled third-kind boundary conditions or through body sources) play in disease initiation. © 2010 Society for Industrial and Applied Mathematics.

  16. Characterization and stability studies of emulsion systems containing pumice

    Directory of Open Access Journals (Sweden)

    Marilene Estanqueiro

    2014-04-01

    Full Text Available Emulsions are the most common form of skin care products. However, these systems may exhibit some instability. Therefore, when developing emulsions for topical application it is interesting to verify whether they have suitable physical and mechanical characteristics and further assess their stability. The aim of this work was to study the stability of emulsion systems, which varied in the proportion of the emulsifying agent cetearyl alcohol (and sodium lauryl sulfate (and sodium cetearyl sulfate (LSX, the nature of the oily phase (decyl oleate, cyclomethicone or dimethicone and the presence or absence of pumice (5% w/w. While maintaining the samples at room temperature, rheology studies, texture analysis and microscopic observation of formulations with and without pumice were performed. Samples were also submitted to an accelerated stability study by centrifugation and to a thermal stress test. Through the testing, it was found that the amount of emulsifying agent affects the consistency and textural properties such as firmness and adhesiveness. So, formulations containing LSX (5% w/w and decyl oleate or dimethicone as oily phase had a better consistency and remained stable with time, so exhibited the best features to be used for skin care products.

  17. Invasive central nervous system aspergillosis in bone marrow transplantation recipients: an overview

    International Nuclear Information System (INIS)

    Guermazi, Ali; Gluckman, Eliane; Tabti, Bachir; Miaux, Yves

    2003-01-01

    Invasive central nervous system aspergillosis is being seen with an increased frequency, particularly due to the increased number of immunosuppressed patients. The major cause of invasive central nervous system aspergillosis is bone marrow transplantation. In most cases, aspergillosis develops in the paranasal sinuses and in the lungs, and secondarily spreads to the brain. Imaging of cerebral aspergillosis may present different patterns depending on the lesion's age and the immunologic status of the patient. Lesions of the spinal cord are far less common but has been encountered in our series. In this article we review the clinical and radiologic features of aspergillosis affecting the central nervous system in patients who underwent bone marrow transplantation. Different CT and MR patterns are presented, including pertinent clinical and pathologic material. Significant morbidity and mortality can be associated with this fungal infection, and it is therefore incumbent upon the radiologist to identify intracranial aspergillosis as early as possible so that appropriate therapy can be administered. (orig.)

  18. Investigation on flow stability of supercritical water cooled systems

    International Nuclear Information System (INIS)

    Cheng, X.; Kuang, B.

    2006-01-01

    Research activities are ongoing worldwide to develop nuclear power plants with supercritical water cooled reactor (SCWR) with the purpose to achieve a high thermal efficiency and to improve their economical competitiveness. However, the strong variation of the thermal-physical properties of water in the vicinity of the pseudo-critical line results in challenging tasks in various fields, e.g. thermal-hydraulic design of a SCWR. One of the challenging tasks is to understand and to predict the dynamic behavior of supercritical water cooled systems. Although many thermal-hydraulic research activities were carried out worldwide in the past as well as in the near present, studies on dynamic behavior and flow stability of SC water cooled systems are scare. Due to the strong density variation, flow stability is expected to be one of the key items which need to be taken into account in the design of a SCWR. In the present work, the dynamic behavior and flow stability of SC water cooled systems are investigated using both numerical and theoretical approaches. For this purpose a new computer code SASC was developed, which can be applied to analysis the dynamic behavior of systems cooled by supercritical fluids. In addition, based on the assumptions of a simplified system, a theoretical model was derived for the prediction of the onset of flow instability. A comparison was made between the results obtained using the theoretical model and those from the SASC code. A good agreement was achieved. This gives the first evidence of the reliability of both the SASC code and the theoretical model

  19. Stability and Bifurcation in Magnetic Flux Feedback Maglev Control System

    Directory of Open Access Journals (Sweden)

    Wen-Qing Zhang

    2013-01-01

    Full Text Available Nonlinear properties of magnetic flux feedback control system have been investigated mainly in this paper. We analyzed the influence of magnetic flux feedback control system on control property by time delay and interfering signal of acceleration. First of all, we have established maglev nonlinear model based on magnetic flux feedback and then discussed hopf bifurcation’s condition caused by the acceleration’s time delay. The critical value of delayed time is obtained. It is proved that the period solution exists in maglev control system and the stable condition has been got. We obtained the characteristic values by employing center manifold reduction theory and normal form method, which represent separately the direction of hopf bifurcation, the stability of the period solution, and the period of the period motion. Subsequently, we discussed the influence maglev system on stability of by acceleration’s interfering signal and obtained the stable domain of interfering signal. Some experiments have been done on CMS04 maglev vehicle of National University of Defense Technology (NUDT in Tangshan city. The results of experiments demonstrate that viewpoints of this paper are correct and scientific. When time lag reaches the critical value, maglev system will produce a supercritical hopf bifurcation which may cause unstable period motion.

  20. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  1. Methods to assess the stability of a bicycle rider system

    NARCIS (Netherlands)

    Cooke, A.G.; Bulsink, Vera Elisabeth; Beusenberg, Mark; Dubbeldam, Rosemary; Bonnema, Gerrit Maarten; Poelman, Wim; Koopman, Hubertus F.J.M.

    2012-01-01

    The SOFIE (Intelligent Assisted Bicycles) project wishes to create performance and design guidelines for mechatronic appliances which improve the stability of electric bicycles, so-called intelligent stability assist devices (IAD). To achieve this goal, a stability hypothesis, an advanced

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

    Directory of Open Access Journals (Sweden)

    Cheng-Ta Hsieh

    2016-04-01

    Full Text Available 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.

  3. Power System Stability Improvement through the Coordination of TCPS-based Damping Controller and Power System Stabilizer

    Directory of Open Access Journals (Sweden)

    ALI, M. A. S.

    2017-11-01

    Full Text Available To guarantee the secure and reliable operations of power systems through the rapid damping of low-frequency electromechanical oscillations (LFEOs is the ultimate objective of this study. This paper presents a coordination of a flexible AC transmission system (FACTS device and power system stabilizer (PSS to meet this objective, and deals with the design of a damping controller based on a thyristor-controlled phase shifter (TCPS and a PSS. The proposed design is incorporated in the framework of a single-machine infinite-bus (SMIB power system. The effectiveness of the proposed design in damping power system oscillations is explored through eigenvalue analysis, time-domain simulations and damping torque contribution. A comparative study on different control schemes, such as with an SMIB including a PSS and an SMIB including a TCPS-based damping controller is also carried out. The obtained results prove the superior performance of the proposed design in improving the stability of the given power system. All the digital simulations are performed using MATLAB/ SIMULINK.

  4. A MARTe based simulator for the JET Vertical Stabilization system

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-10-15

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

  5. Automotive mechatronics automotive networking, driving stability systems, electronics

    CERN Document Server

    2015-01-01

    As the complexity of automotive vehicles increases this book presents operational and practical issues of automotive mechatronics. It is a comprehensive introduction to controlled automotive systems and provides detailed information of sensors for travel, angle, engine speed, vehicle speed, acceleration, pressure, temperature, flow, gas concentration etc. The measurement principles of the different sensor groups are explained and examples to show the measurement principles applied in different types. Contents Basics of mechatronics.- Architecture.- Electronic control unit.- Software development.- Basic principles of networking.- Automotive networking.- Bus systems.- Automotive sensors.- Sensor measuring principles.- Sensor types.- Electric actuators.- Electrohydraulic actuators.- Electronic transmission control.- Electronic transmission control unit.- Modules for transmission control.- Antilock braking system.- Traction control system.- Electronic stability program.- Automatic brake functions.- Hydraulic modu...

  6. Stability of Moons in the Trappist-1 System

    Science.gov (United States)

    Allen, John; Becker, Christopher; Fuse, Christopher

    2018-01-01

    In the last 20 years, numerous exoplanets have been discovered and it has become clear that habitable bodies are rare. Exomoons mark the next stage in identifying habitable environs. In our own Solar system, several moons have been identified as having features suitable to sustain life. The Trappist-1 system (Gillon et al. 2017) is a compact configuration of seven Earth-like planets orbiting a M-type dwarf star. The presence of moons cannot be confirmed in the transit data. Kane et al. (2017) suggests that it would be highly improbable for a moon to maintain a stable orbit around any Trappist-1 planet. The current study investigates the claim by Kane et al. (2017), examining the stability of the Trappist-1 system in the presence of forming satellites. Moon disks are simulated by distributing 100 bodies, each with mass 5.26 x 1018 kg randomly within 10% - 90% of the exoplanet’s Hill sphere. Utilizing N-body simulations, the planets and theoretical moons were tracked for 500 kyrs, allowing for gravitational interactions and mergers. Instabilities in the orbital parameters of the Trappist-1 planets was detected, in agreement with previous authors (Burgasser & Mamajerk 2017). Some of the planets are found to retain at least a single satellite for the same duration as the planetary stability. These data suggest that additional observation of the Trappist-1 system may yield the first detection of an exomoon.

  7. METHODOLOGY FOR INSTITUTIONAL ANALYSIS OF STABILITY OF REGIONAL FINANCIAL SYSTEM

    Directory of Open Access Journals (Sweden)

    A. V. Milenkov

    2016-01-01

    Full Text Available The relevance of the article due to the urgent need to develop a methodological framework in the field of regional finance research dictated by the substantial increase in the volume and composition of the socio-economic problems, the solution of which, including financial support, the responsibility of the public authorities of the Russian Federation. The article presents the results of the author's research in the field of institutional analysis of the stability of the regional financial system as a set of institutions and organizations interacting with the regional real sector of economy.Methodology. The methodological basis of this article are the economic and statistical methods of analysis, legal documents in the field of the sustainability of the regional financial system, publications in the field of economic and financial security.Conclusions / relevance. The practical significance of the work lies in the provisions of orientation, conclusions and recommendations aimed at the widespread use of search and adaptation of the institutional analysis of the sources of the regional stability of the financial system, which can be used by the legislative and executive authorities of the Russian Federation, the Ministry of Defence in the current activity.Methodological approaches to the structuring objectives of institutional analysis on the basis of the hierarchical representation of the institutional environment of functioning of federal subject the financial system.

  8. Study of nonlinear system stability using eigenvalue analysis: Gyroscopic motion

    Science.gov (United States)

    Shabana, Ahmed A.; Zaher, Mohamed H.; Recuero, Antonio M.; Rathod, Cheta

    2011-11-01

    General computational multibody system (MBS) algorithms allow for the linearization of the highly nonlinear equations of motion at different points in time in order to obtain the eigenvalue solution. This eigenvalue solution of the linearized equations is often used to shed light on the system stability at different configurations that correspond to different time points. Different MBS algorithms, however, employ different sets of orientation coordinates, such as Euler angles and Euler parameters, which lead to different forms of the dynamic equations of motion. As a consequence, the forms of the linearized equations and the eigenvalue solution obtained strongly depend on the set of orientation coordinates used. This paper addresses this fundamental issue by examining the effect of the use of different orientation parameters on the linearized equations of a gyroscope. The nonlinear equations of motion of the gyroscope are formulated using two different sets of orientation parameters: Euler angles and Euler parameters. In order to obtain a set of linearized equations that can be used to define the eigenvalue solution, the algebraic equations that describe the MBS constraints are systematically eliminated leading to a nonlinear form of the equations of motion expressed in terms of the system degrees of freedom. Because in MBS applications the generalized forces can be highly nonlinear and can depend on the velocities, a state space formulation is used to solve the eigenvalue problem. It is shown in this paper that the independent state equations formulated using Euler angles and Euler parameters lead to different eigenvalue solutions. This solution is also different from the solution obtained using a form of the Newton-Euler matrix equation expressed in terms of the angular accelerations and angular velocities. A time-domain solution of the linearized equations is also presented in order to compare between the solutions obtained using two different sets of

  9. MHD-Stabilization of Axisymmetric Mirror Systems Using Pulsed ECRH

    International Nuclear Information System (INIS)

    Post, R.F.

    2010-01-01

    This paper, part of a continuing study of means for the stabilization of MHD interchange modes in axisymmertric mirror-based plasma confinement systems, is aimed at a preliminary look at a technique that would employ a train of plasma pressure pulses produced by ECRH to accomplish the stabilization. The purpose of using sequentially pulsed ECRH rather than continuous-wave ECRH is to facilitate the localization of the heated-electron plasma pulses in regions of the magnetic field with a strong positive field-line curvature, e. g. in the 'expander' region of the mirror magnetic field, outside the outermost mirror, or in other regions of the field with positive field-line curvature. The technique proposed, of the class known as 'dynamic stabilization,' relies on the time-averaged effect of plasma pressure pulses generated in regions of positive field-line curvature to overcome the destabilizing effect of plasma pressure in regions of negative field-line curvature within the confinement region. As will also be discussed in the paper, the plasma pulses, when produced in regions of the confining having a negative gradient, create transient electric potentials of ambipolar origin, an effect that was studied in 1964 in The PLEIDE experiment in France. These electric fields preserve the localization of the hot-electron plasma pulses for a time determined by ion inertia. It is suggested that it may be possible to use this result of pulsed ECRH not only to help to stabilize the plasma but also to help plug mirror losses in a manner similar to that employed in the Tandem Mirror.

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

    Directory of Open Access Journals (Sweden)

    Tadeusz Kaczorek

    2013-06-01

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

  11. Linear local stability of electrostatic drift modes in helical systems

    International Nuclear Information System (INIS)

    Yamagishi, O.; Nakajima, N.; Sugama, H.; Nakamura, Y.

    2003-01-01

    We investigate the stability of the drift wave in helical systems. For this purpose, we solve the linear local gyrokinetic-Poisson equation, in the electrostatic regime. As a model of helical plasmas, Large helical Device (LHD) is considered. The equation we apply is rather exact in the framework of linear gyrokinetic theory, where only the approximation is the ballooning representation. In this paper, we consider only collisionless cases. All the frequency regime can be naturally reated without any assumptions, and in such cases, ion temperature gradient modes (ITG), trapped electron modes (TEM), and electron temperature gradient modes (ETG) are expected to become unstable linearly independently. (orig.)

  12. Preliminary hazards analysis of thermal scrap stabilization system. Revision 1

    International Nuclear Information System (INIS)

    Lewis, W.S.

    1994-01-01

    This preliminary analysis examined the HA-21I glovebox and its supporting systems for potential process hazards. Upon further analysis, the thermal stabilization system has been installed in gloveboxes HC-21A and HC-21C. The use of HC-21C and HC-21A simplified the initial safety analysis. In addition, these gloveboxes were cleaner and required less modification for operation than glovebox HA-21I. While this document refers to glovebox HA-21I for the hazards analysis performed, glovebox HC-21C is sufficiently similar that the following analysis is also valid for HC-21C. This hazards analysis document is being re-released as revision 1 to include the updated flowsheet document (Appendix C) and the updated design basis (Appendix D). The revised Process Flow Schematic has also been included (Appendix E). This Current revision incorporates the recommendations provided from the original hazards analysis as well. The System Design Description (SDD) has also been appended (Appendix H) to document the bases for Safety Classification of thermal stabilization equipment

  13. Long-term evolution and stability of planetary systems

    Science.gov (United States)

    Juric, Mario

    This dissertation studies the dynamical evolution and stability of planetary systems over long time spans (10 8 -10 9 years). I investigated the dynamical evolution of few-planet systems by simulating ensembles of systems consisting of hundreds to thousands of randomly constructed members. I looked at ways to classify the systems according to their dynamical activity, and found the median Hill separation of an ensemble to be a sufficiently good criterion for separation into active (those exhibiting frequent planetary close encounters, collisions or ejections) and inactive ensembles. I examined the evolution of dynamical parameters in active systems. I found that in ensembles of dynamically active (initially unstable) systems the eccentricity distribution evolves towards the same equilibrium form, irrespective of the distribution it began with. Furthermore, this equilibrium distribution is indistinguishable, within observational errors, from the distribution found in extrasolar planets. This is to my knowledge the first successful detailed theoretical reproduction of the form of observed exoplanet eccentricity distribution. I further looked for quantities that can be used as indicators of long-term stability of planetary systems, specifically the angular momentum deficit (AMD) as originally proposed by Laskar. I found that the quantity Q , defined as the ratio of minimum AMD required for a planetary collision to occur in secular theory and the total AMD of the system, may be used to predict the likelihood of decay of a planetary system. Qualitatively, the decay in systems having Q [Special characters omitted.] 1 is highly probable, while systems with Q [Special characters omitted.] 1 were found to be stable. To conduct the above investigations, I developed a new integrator package (VENUS), and the HYBRID/EE integration scheme designed for nearly-symplectic long-term integrations. VENUS implements integration algorithms for few-body planetary system integrations

  14. Recurrent Neural Network for Single Machine Power System Stabilizer

    Directory of Open Access Journals (Sweden)

    Widi Aribowo

    2010-04-01

    Full Text Available In this paper, recurrent neural network (RNN is used to design power system stabilizer (PSS due to its advantage on the dependence not only on present input but also on past condition. A RNN-PSS is able to capture the dynamic response of a system without any delays caused by external feedback, primarily by the internal feedback loop in recurrent neuron. In this paper, RNNPSS consists of a RNN-identifier and a RNN-controller. The RNN-Identifier functions as the tracker of dynamics characteristics of the plant, while the RNN-controller is used to damp the system’s low frequency oscillations. Simulation results using MATLAB demonstrate that the RNNPSS can successfully damp out oscillation and improve the performance of the system.

  15. Stability and Multiscroll Attractors of Control Systems via the Abscissa

    Directory of Open Access Journals (Sweden)

    Edgar-Cristian Díaz-González

    2017-01-01

    Full Text Available We present an approach to generate multiscroll attractors via destabilization of piecewise linear systems based on Hurwitz matrix in this paper. First we present some results about the abscissa of stability of characteristic polynomials from linear differential equations systems; that is, we consider Hurwitz polynomials. The starting point is the Gauss–Lucas theorem, we provide lower bounds for Hurwitz polynomials, and by successively decreasing the order of the derivative of the Hurwitz polynomial one obtains a sequence of lower bounds. The results are extended in a straightforward way to interval polynomials; then we apply the abscissa as a measure to destabilize Hurwitz polynomial for the generation of a family of multiscroll attractors based on a class of unstable dissipative systems (UDS of affine linear type.

  16. Breaking Dense Structures: Proving Stability of Densely Structured Hybrid Systems

    Directory of Open Access Journals (Sweden)

    Eike Möhlmann

    2015-06-01

    Full Text Available Abstraction and refinement is widely used in software development. Such techniques are valuable since they allow to handle even more complex systems. One key point is the ability to decompose a large system into subsystems, analyze those subsystems and deduce properties of the larger system. As cyber-physical systems tend to become more and more complex, such techniques become more appealing. In 2009, Oehlerking and Theel presented a (de-composition technique for hybrid systems. This technique is graph-based and constructs a Lyapunov function for hybrid systems having a complex discrete state space. The technique consists of (1 decomposing the underlying graph of the hybrid system into subgraphs, (2 computing multiple local Lyapunov functions for the subgraphs, and finally (3 composing the local Lyapunov functions into a piecewise Lyapunov function. A Lyapunov function can serve multiple purposes, e.g., it certifies stability or termination of a system or allows to construct invariant sets, which in turn may be used to certify safety and security. In this paper, we propose an improvement to the decomposing technique, which relaxes the graph structure before applying the decomposition technique. Our relaxation significantly reduces the connectivity of the graph by exploiting super-dense switching. The relaxation makes the decomposition technique more efficient on one hand and on the other allows to decompose a wider range of graph structures.

  17. Steam Turbine Control Valve Stiction Effect on Power System Stability

    International Nuclear Information System (INIS)

    Halimi, B.

    2010-01-01

    One of the most important problems in power system dynamic stability is low frequency oscillations. This kind of oscillation has significant effects on the stability and security of the power system. In some previous papers, a fact was introduced that a steam pressure continuous fluctuation in turbine steam inlet pipeline may lead to a kind of low frequency oscillation of power systems. Generally, in a power generation plant, steam turbine system composes of some main components, i.e. a boiler or steam generator, stop valves, control valves and turbines that are connected by piping. In the conventional system, the turbine system is composed with a lot of stop and control valves. The steam is provided by a boiler or steam generator. In an abnormal case, the stop valve shuts of the steal flow to the turbine. The steam flow to the turbine is regulated by controlling the control valves. The control valves are provided to regulate the flow of steam to the turbine for starting, increasing or decreasing the power, and also maintaining speed control with the turbine governor system. Unfortunately, the control valve has inherent static friction (stiction) nonlinearity characteristics. Industrial surveys indicated that about 20-30% of all control loops oscillate due to valve problem caused by this nonlinear characteristic. In this paper, steam turbine control valve stiction effect on power system oscillation is presented. To analyze the stiction characteristic effect, firstly a model of control valve and its stiction characteristic are derived by using Newton's laws. A complete tandem steam prime mover, including a speed governing system, a four-stage steam turbine, and a shaft with up to for masses is adopted to analyze the performance of the steam turbine. The governor system consists of some important parts, i.e. a proportional controller, speed relay, control valve with its stiction characteristic, and stem lift position of control valve controller. The steam turbine has

  18. 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.

  19. Currency System and Its Impact on Economic Stability

    Directory of Open Access Journals (Sweden)

    Desmadi Saharuddin

    2017-05-01

    Full Text Available A number of economic problems that occurred during the power of Mamluk (1250-1517 AD was considered as a result of the change to currency system, namely from the system of commodity-based money (gold and silver into paper-based money (fiat. Instability prices, decrease of trading activities, high of unemployment number were a number of economic indicators that occurred at that time. This issue of macro-economy was considered as a result of changes in the money system. This study analyzes the dynamic relationship between the price of gold as a representation of commodity money system and M2 as a representation of fiat money against the stability of economic indicators such as inflation, economic growth, stock prices, and unemployment and interest rates. This study found that both systems not vary significantly against each other in its influence on macroeconomic variables. It means that the two systems do not have contrast distinction. Indeed, it was found that the commodity-based money system is not free of inflation, as propagated by the supporters of the dinar and dirham (dinarist. DOI: 10.15408/aiq.v9i2.4749

  20. Multistage position-stabilized vibration isolation system for neutron interferometry

    Science.gov (United States)

    Arif, Muhammad; Brown, Dennis E.; Greene, Geoffrey L.; Clothier, R.; Littrell, K.

    1994-10-01

    A two stage, position stabilized vibration isolation system has been constructed and is now in operation at the Cold Neutron Research Facility of the National Institute of Standards and Technology, Gaithersburg, MD. The system employs pneumatic isolators with a multiple input/multiple output pneumatic servo system based upon pulse width modulation control loops. The first stage consists of a 40,000 kg reinforced concrete table supported by pneumatic isolators. A large environmentally isolated laboratory enclosure rests on the concrete table. The second stage consists of a 3000 kg granite optical table located within the enclosure and supported by another set of pneumatic isolators. The position of the two stages is monitored by proximity sensors and inclinometers with 12 degrees of freedom. The system controls 12 independent pneumatic airsprings. The signals from these sensors are fed into a personal computer based control system. The control system has maintained the position of the two stages to better than 1 micrometers in translation and 5 (mu) rad in orientation for a period of a few months. A description of the system and its characteristics is given.

  1. System specification/system design document comment review: Plutonium Stabilization and Packaging System. Notes of conference

    International Nuclear Information System (INIS)

    1996-01-01

    A meeting was held between DOE personnel and the BNFL team to review the proposed resolutions to DOE comments on the initial issue of the system specification and system design document for the Plutonium Stabilization and Packaging System. The objectives of this project are to design, fabricate, install, and start up a glovebox system for the safe repackaging of plutonium oxide and metal, with a requirement of a 50-year storage period. The areas discussed at the meeting were: nitrogen in can; moisture instrumentation; glovebox atmosphere; can marking bar coding; weld quality; NFPA-101 references; inner can swabbing; ultimate storage environment; throughput; convenience can screw-top design; furnacetrays; authorization basis; compactor safety; schedule for DOE review actions; fire protection; criticality safety; applicable standards; approach to MC and A; homogeneous oxide; resistance welder power; and tray overfill. Revised resolutions were drafted and are presented

  2. System specification/system design document comment review: Plutonium Stabilization and Packaging System. Notes of conference

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-07-01

    A meeting was held between DOE personnel and the BNFL team to review the proposed resolutions to DOE comments on the initial issue of the system specification and system design document for the Plutonium Stabilization and Packaging System. The objectives of this project are to design, fabricate, install, and start up a glovebox system for the safe repackaging of plutonium oxide and metal, with a requirement of a 50-year storage period. The areas discussed at the meeting were: nitrogen in can; moisture instrumentation; glovebox atmosphere; can marking-bar coding; weld quality; NFPA-101 references; inner can swabbing; ultimate storage environment; throughput; convenience can screw-top design; furnace/trays; authorization basis; compactor safety; schedule for DOE review actions; fire protection; criticality safety; applicable standards; approach to MC and A; homogeneous oxide; resistance welder power; and tray overfill. Revised resolutions were drafted and are presented.

  3. Stability considerations of packed multi-planet systems

    Science.gov (United States)

    Gratia, Pierre; Lissauer, Jack

    2018-04-01

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

  4. Invasive lobular breast cancer and its variants: how special are they for systemic therapy decisions?

    Science.gov (United States)

    Guiu, Séverine; Wolfer, Anita; Jacot, William; Fumoleau, Pierre; Romieu, Gilles; Bonnetain, Franck; Fiche, Maryse

    2014-12-01

    The WHO classification of breast tumors distinguishes, besides invasive breast cancer 'of no special type' (former invasive ductal carcinoma, representing 60-70% of all breast cancers), 30 special types, of which invasive lobular carcinoma (ILC) is the most common (5-15%). We review the literature on (i) the specificity and heterogeneity of ILC biology as documented by various analytical techniques, including the results of molecular testing for risk of recurrence; (ii) the impact of lobular histology on prediction of prognosis and effect of systemic therapies in patients. Though it is generally admitted that ILC has a better prognosis than IDC, is endocrine responsive, and responds poorly to chemotherapy, currently available data do not unanimously support these assumptions. This review demonstrates some lack of specific data and a need for improving clinical research design to allow oncologists to make informed systemic therapy decisions in patients with ILC. Importantly, future studies should compare various endpoints in ILC breast cancer patients among the group of hormonosensitive breast cancer. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  6. Managing invasive aquatic plants in a changing system: strategic consideration of ecosystem services.

    Science.gov (United States)

    Hershner, Carl; Havens, Kirk J

    2008-06-01

    Climate change is projected to increase stress for many coastal plant communities. Along large portions of the North American coast, habitat degradation from anthropogenic changes to the environment already threaten the community structure of tidal marshes and submerged aquatic grass beds. The potential loss of ecological services historically provided by these communities has been a long-standing rationale for aggressive control of invading plants such as Phragmites australis and Hydrilla verticillata. Increasing evidence of ecological services provided by invasive species such as P. australis and H. verticillata suggest that, in the face of increasing stress, it may be prudent to take a more pragmatic approach regarding the effect of these species on coastal ecosystems. The notable resilience of these species to control efforts and their competitive success and comparative vigor in stressed systems and capacity to provide at least some beneficial services combine to suggest some invasive species may have a useful role in managed coastal ecosystems.

  7. Modified Schur-Cohn Criterion for Stability of Delayed Systems

    Directory of Open Access Journals (Sweden)

    Juan Ignacio Mulero-Martínez

    2015-01-01

    Full Text Available A modified Schur-Cohn criterion for time-delay linear time-invariant systems is derived. The classical Schur-Cohn criterion has two main drawbacks; namely, (i the dimension of the Schur-Cohn matrix generates some round-off errors eventually resulting in a polynomial of s with erroneous coefficients and (ii imaginary roots are very hard to detect when numerical errors creep in. In contrast to the classical Schur-Cohn criterion an alternative approach is proposed in this paper which is based on the application of triangular matrices over a polynomial ring in a similar way as in the Jury test of stability for discrete systems. The advantages of the proposed approach are that it halves the dimension of the polynomial and it only requires seeking real roots, making this modified criterion comparable to the Rekasius substitution criterion.

  8. A fuzzy logic pitch angle controller for power system stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Jauch, Clemens; Cronin, Tom; Sorensen, Poul [Wind Energy Department, Riso National Laboratory, PO Box 49, DK-4000 Roskilde, (Denmark); Jensen, Birgitte Bak [Institute of Energy Technology, Aalborg University, Pontoppidanstraede 101, DK-9220 Aalborg East, (Denmark)

    2006-07-12

    In this article the design of a fuzzy logic pitch angle controller for a fixed speed, active-stall wind turbine, which is used for power system stabilization, is presented. The system to be controlled, which is the wind turbine and the power system to which the turbine is connected, is described. The advantages of fuzzy logic control when applied to large-signal control of active-stall wind turbines are outlined. The general steps of the design process for a fuzzy logic controller, including definition of the controller inputs, set-up of the fuzzy rules and the method of defuzzification, are described. The performance of the controller is assessed by simulation, where the wind turbine's task is to dampen power system oscillations. In the scenario simulated for this work, the wind turbine has to ride through a transient short-circuit fault and subsequently contribute to the damping of the grid frequency oscillations that are caused by the transient fault. It is concluded that the fuzzy logic controller enables the wind turbine to dampen power system oscillations. It is also concluded that, owing to the inherent non-linearities in a wind turbine and the unpredictability of the whole system, the fuzzy logic controller is very suitable for this application. (Author).

  9. Stabilization for Damping Multimachine Power System with Time-Varying Delays and Sector Saturating Actuator

    OpenAIRE

    Ma, Linlin; Liang, Yanping; Chen, Jian

    2016-01-01

    This paper studies the stabilization problem for damping multimachine power system with time-varying delays and sector saturating actuator. The multivariable proportional plus derivative (PD) type stabilizer is designed by transforming the problem of PD controller design to that of state feedback stabilizer design for a system in descriptor form. A new sufficient condition of closed-loop multimachine power system asymptomatic stability is derived based on the Lyapunov theory. Computer simulat...

  10. STATCOM's Effects on Stability Improvement of Induction Generator based Wind Turbine Systems

    DEFF Research Database (Denmark)

    Hu, Y; Chen, Zhe

    2009-01-01

    Large number of wind turbines are being installed and connected to power systems. In some countries or networks, the penetration level of wind power is significant high so as to affect the power system operation and control. Consequently, the stable operation of wind turbine systems is very impor...... important for power system stability. This paper studies the effect of STATCOM on stability improvement of a wind turbine system. The function of the STATCOM in improving the system stability has been demonstrated....

  11. Implant survivorship analysis after minimally invasive sacroiliac joint fusion using the iFuse Implant System?

    OpenAIRE

    Cher, Daniel J; Reckling, W Carlton; Capobianco, Robyn A

    2015-01-01

    Daniel J Cher,1 W Carlton Reckling,2 Robyn A Capobianco1 1Department of Clinical Affairs, SI-BONE, Inc., 2Department of Medical Affairs, SI-BONE, Inc., San Jose, CA, USA Introduction: Surgical revision rate is a key outcome with all permanent implants. The iFuse Implant System® is a permanent implant used to perform minimally invasive sacroiliac joint fusion. The purpose of this study is to determine the surgical revision rate after sacroiliac joint fusion surgery with this system. M...

  12. Improved Delay-Dependent Stability Conditions for MIMO Networked Control Systems with Nonlinear Perturbations

    Science.gov (United States)

    2014-01-01

    This paper provides improved time delay-dependent stability criteria for multi-input and multi-output (MIMO) network control systems (NCSs) with nonlinear perturbations. Without the stability assumption on the neutral operator after the descriptor approach, the new proposed stability theory is less conservative than the existing stability condition. Theoretical proof is given in this paper to demonstrate the effectiveness of the proposed stability condition. PMID:24744679

  13. Improving Power System Stability Using Transfer Function: A Comparative Analysis

    Directory of Open Access Journals (Sweden)

    G. Shahgholian

    2017-10-01

    Full Text Available In this paper, a small-signal dynamic model of a single-machine infinite-bus (SMIB power system that includes IEEE type-ST1 excitation system and PSS based on transfer fu¬n¬c¬¬tion structure is presented. The changes in the operating co¬n¬dition of a power system on dynamic performance have been exa¬m¬ined. The dynamic performance of the closed-loop system is ana¬lyzed base on its eigenvalues. The effectiveness of the par¬a¬m¬e¬t¬ers changes on dynamic stability is verified by simulation res¬u¬l¬ts. Three types of PSS have been considered for analysis: (a the derivative PSS, (b the lead-lag PSS or conventional PSS, and (c the proportional-integral-derivative PSS. The objective fu¬nc¬t¬i¬o¬n is formulated to increase the dam¬¬ping ratio of the electromechanical mode eigenvalues. Simu¬la¬tion results show that the PID-PSS performs better for less ov¬e¬r¬shoot and less settling time comp¬ared with the CPSS and DPSS un¬der different load ope¬ration and the significant system pa¬r¬am¬eter variation conditions.

  14. Complex systems of biological interest stability under ionising radiations

    International Nuclear Information System (INIS)

    Maclot, Sylvain

    2014-01-01

    This PhD work presents the study of stability of molecular systems of biological interest in the gas phase after interaction with ionising radiations. The use of ionising radiation can probe the physical chemistry of complex systems at the molecular scale and thus consider their intrinsic properties. Beyond the fundamental aspect, this work is part of the overall understanding of radiation effects on living organisms and in particular the use of ionizing radiation in radiotherapy. Specifically, this study focused on the use of low-energy multiply charged ions (tens of keV) provided by the GANIL (Caen), which includes most of the experiments presented. In addition, experiments using VUV photons were also conducted at synchrotron ELETTRA (Trieste, Italy). The bio-molecular systems studied are amino acids and nucleic acid constituents. Using an experimental crossed beams device allows interaction between biomolecules and ionising radiation leads mainly to the ionization and fragmentation of the system. The study of its relaxation dynamics is by time-of-flight mass spectrometry coupled to a coincidences measurements method. It is shown that an approach combining experiment and theory allows a detailed study of the fragmentation dynamics of complex systems. The results indicate that fragmentation is generally governed by the Coulomb repulsion but the intramolecular rearrangements involve specific relaxation mechanisms. (author) [fr

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

    Science.gov (United States)

    Malekpour, Mahyar R. (Inventor)

    2010-01-01

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

  16. Absolute stability of nonlinear systems with time delays and applications to neural networks

    Directory of Open Access Journals (Sweden)

    Xinzhi Liu

    2001-01-01

    Full Text Available In this paper, absolute stability of nonlinear systems with time delays is investigated. Sufficient conditions on absolute stability are derived by using the comparison principle and differential inequalities. These conditions are simple and easy to check. In addition, exponential stability conditions for some special cases of nonlinear delay systems are discussed. Applications of those results to cellular neural networks are presented.

  17. STABILITY OF SATELLITES IN CLOSELY PACKED PLANETARY SYSTEMS

    International Nuclear Information System (INIS)

    Payne, Matthew J.; Holman, Matthew J.; Deck, Katherine M.; Perets, Hagai B.

    2013-01-01

    We perform numerical integrations of four-body (star, planet, planet, satellite) systems to investigate the stability of satellites in planetary systems with tightly packed inner planets (STIPs). We find that the majority of closely spaced stable two-planet systems can stably support satellites across a range of parameter-space which is only slightly decreased compared to that seen for the single-planet case. In particular, circular prograde satellites remain stable out to ∼0.4 R H (where R H is the Hill radius) as opposed to 0.5 R H in the single-planet case. A similarly small restriction in the stable parameter-space for retrograde satellites is observed, where planetary close approaches in the range 2.5-4.5 mutual Hill radii destabilize most satellites orbits only if a ∼ 0.65 R H . In very close planetary pairs (e.g., the 12:11 resonance) the addition of a satellite frequently destabilizes the entire system, causing extreme close approaches and the loss of satellites over a range of circumplanetary semi-major axes. The majority of systems investigated stably harbored satellites over a wide parameter-space, suggesting that STIPs can generally offer a dynamically stable home for satellites, albeit with a slightly smaller stable parameter-space than the single-planet case. As we demonstrate that multi-planet systems are not a priori poor candidates for hosting satellites, future measurements of satellite occurrence rates in multi-planet systems versus single-planet systems could be used to constrain either satellite formation or past periods of strong dynamical interaction between planets

  18. Design of Power System Stabilizer based on Sliding Mode Control Theory for Multi- Machine Power System

    Directory of Open Access Journals (Sweden)

    Ghazanfar Shahgholian

    2010-01-01

    Full Text Available This paper presents a new method for designing of power system stabilizer (PSS based on sliding mode control (SMC technique. The control objective is to enhance stability and improve the dynamic response of the multi-machine power system. The mathematical model of the synchronous generator is first transformed into a form that facilitates the design of nonlinear control schemes. Then, a sliding mode controller is proposed. In order to test effectiveness of the proposed scheme, simulation will be carried out to analyze the small signal stability characteristics of the system about the steady state operating condition following the change in the parameters of the system and to the disturbances. For comparison, simulation of a conventional control PSS (lead-lag compensation type will be carried out. The main approach is to focus on the control performance which later is proven to have the degree of shorter reaching time and lower spike.

  19. Stable Tending Control of Complex Power Systems: An Example of Localized Design of Power System Stabilizers

    OpenAIRE

    Wenjuan Du

    2016-01-01

    The phase compensation method was proposed based on the concept of the damping torque analysis (DTA). It is a method for the design of a PSS (power system stabilizer) to suppress local-mode power oscillations in a single-machine infinite-bus power system. This paper presents the application of the phase compensation method for the design of a PSS in a multi-machine power system. The application is achieved by examining the direct damping contribution of the stabilizer to the power oscillation...

  20. Performance of UPFC to enhance Power Stability in Multi-Machine Power System under Fault Condition

    OpenAIRE

    Khan, Shah Munir; Arbab, Muhammad Naeem

    2017-01-01

    International audience; Modern power systems are interconnected and exposed to external as well as internal disturbances. The stable operation of power system (Power System Stability) is the subject of great interest for power engineers for the last few decades. Stability in power system is achieved by many means, but nowadays FACTS controllers, which are a family of flexible alternating current transmission system devices, are widely used to enhance stability. Among these is the unified powe...

  1. INVESTIGATION WITH MODAL ANALYSIS OF EFFECTS OF HIGH PV PENETRATION ON POWER SYSTEM VOLTAGE STABILITY

    OpenAIRE

    YILDIRIM, Burak

    2017-01-01

    This paper shows the effects of high PVintegration on the power system voltage stability. PV power plant was appliedto the IEEE 30 bus test system. Modal analysis method is used to show theeffect of PV integration on power system voltage stability. The power rate ofsynchronous generator in the IEEE 30 bus system is increased to show the powersystem stability effect of high PV penetration and then the PV generation withthe same power rate is connected appropriate bus in power system. The modal...

  2. Stabilization of Harmonic Instability in AC Distribution Power System with Active Damping

    DEFF Research Database (Denmark)

    Yoon, Changwoo; Wang, Xiongfei; Bak, Claus Leth

    2015-01-01

    This paper deals stabilizing method of the interaction problems among the interconnected power electronics based power devices in a power distribution system. Even if each of the inverters in the network is stable individually, the combined network stability cannot be assured unless holistic...... stability assessment is performed. The impedance based stability criterion is used to study the effect of the active damping on the system stability. A benchmark of a Cigré power distribution network is modeled under the impedance based stability criterion and validated using the PSCAD/EMTDC simulation...

  3. Co-simulation of heavy truck tire dynamics and electronic stability control systems (phase A).

    Science.gov (United States)

    2009-07-01

    Electronic stability control (ESC) systems have been proven to be an effective means of preventing instability and loss of control on both passenger vehicles and heavy trucks. In addition, roll stability algorithms are an effective means of reducing ...

  4. Optimization of Fuzzy Logic Controller for Supervisory Power System Stabilizers

    Directory of Open Access Journals (Sweden)

    Y. A. Al-Turki

    2012-01-01

    Full Text Available This paper presents a powerful supervisory power system stabilizer (PSS using an adaptive fuzzy logic controller driven by an adaptive fuzzy set (AFS. The system under study consists of two synchronous generators, each fitted with a PSS, which are connected via double transmission lines. Different types of PSS-controller techniques are considered. The proposed genetic adaptive fuzzy logic controller (GAFLC-PSS, using 25 rules, is compared with a static fuzzy logic controller (SFLC driven by a fixed fuzzy set (FFS which has 49 rules. Both fuzzy logic controller (FLC algorithms utilize the speed error and its rate of change as an input vector. The adaptive FLC algorithm uses a genetic algorithmto tune the parameters of the fuzzy set of each PSS. The FLC’s are simulated and tested when the system is subjected to different disturbances under a wide range of operating points. The proposed GAFLC using AFS reduced the computational time of the FLC, where the number of rules is reduced from 49 to 25 rules. In addition, the proposed adaptive FLC driven by a genetic algorithm also reduced the complexity of the fuzzy model, while achieving a good dynamic response of the system under study.

  5. Canister positioning. Influence of fracture system on deposition hole stability

    International Nuclear Information System (INIS)

    Hoekmark, Harald

    2003-11-01

    The study concerns the mechanical behaviour of rock surrounding tunnels and deposition holes in a nuclear waste repository. The mechanical effects of tunnel excavation and deposition hole excavation are investigated by use of a tunnel scale numerical model representing a part of a KBS-3 type repository. The excavation geometry, the initial pre-mining state of stress, and the geometrical features of the fracture system are defined according to conditions that prevail in the TBM tunnel rock mass in Aespoe HRL. Comparisons are made between results obtained without consideration of fractures and results obtained with inclusion of the fracture system. The focus is on the region around the intersection of a tunnel and a deposition hole. A general conclusion is that a fracture system of the type found in the TBM rock mass does not have a decisive influence on the stability of the deposition holes. To estimate the expected extent of spalling, information about other conditions, e.g. the orientation of the initial stresses and the strength properties of the intact rock, is more important than detailed information about the fracture system

  6. Stability Analysis of a Helicopter with an External Slung Load System

    Directory of Open Access Journals (Sweden)

    Kary Thanapalan

    2016-01-01

    Full Text Available This paper describes the stability analysis of a helicopter with an underslung external load system. The Lyapunov second method is considered for the stability analysis. The system is considered as a cascade connection of uncertain nonlinear system. The stability analysis is conducted to ensure the stabilisation of the helicopter system and the positioning of the underslung load at hover condition. Stability analysis and numerical results proved that if desired condition for the stability is met, then it is possible to locate the load at the specified position or its neighbourhood.

  7. Integrated monitoring and information systems for managing aquatic invasive species in a changing climate

    Science.gov (United States)

    Lee, Henry; Reusser, Deborah A.; Olden, Julian D.; Smith, Scott S.; Graham, Jim; Burkett, Virginia; Dukes, Jeffrey S.; Piorkowski, Robert J.; Mcphedran, John

    2008-01-01

    Changes in temperature, precipitation, and other climatic drivers and sea-level rise will affect populations of existing native and non-native aquatic species and the vulnerability of aquatic environments to new invasions. Monitoring surveys provide the foundation for assessing the combined effects of climate change and invasions by providing baseline biotic and environmental conditions, although the utility of a survey depends on whether the results are quantitative or qualitative, and other design considerations. The results from a variety of monitoring programs in the United States are available in integrated biological information systems, although many include only non-native species, not native species. Besides including natives, we suggest these systems could be improved through the development of standardized methods that capture habitat and physiological requirements and link regional and national biological databases into distributed Web portals that allow drawing information from multiple sources. Combining the outputs from these biological information systems with environmental data would allow the development of ecological-niche models that predict the potential distribution or abundance of native and non-native species on the basis of current environmental conditions. Environmental projections from climate models can be used in these niche models to project changes in species distributions or abundances under altered climatic conditions and to identify potential high-risk invaders. There are, however, a number of challenges, such as uncertainties associated with projections from climate and niche models and difficulty in integrating data with different temporal and spatial granularity. Even with these uncertainties, integration of biological and environmental information systems, niche models, and climate projections would improve management of aquatic ecosystems under the dual threats of biotic invasions and climate change

  8. Stabilization of nonlinear sandwich systems via state feedback-Discrete-time systems

    NARCIS (Netherlands)

    Wang, Xu; Stoorvogel, Antonie Arij; Saberi, Ali; Grip, H°avard Fjær; Sannuti, Peddapullaiah

    2011-01-01

    A recent paper (IEEE Trans. Aut. Contr. 2010; 55(9):2156–2160) considered stabilization of a class of continuous-time nonlinear sandwich systems via state feedback. This paper is a discrete-time counterpart of it. The class of nonlinear sandwich systems consists of saturation elements sandwiched

  9. Preliminary safety evaluation for the plutonium stabilization and packaging system

    International Nuclear Information System (INIS)

    Shapley, J.E.

    1997-01-01

    This Preliminary Safety Evaluation (PSE) describes and analyzes the installation and operation of the Plutonium Stabilization and Packaging System (SPS) at the Plutonium Finishing Plant (PFP). The SPS is a combination of components required to expedite the safe and timely storage of Plutonium (Pu) oxide. The SPS program will receive site Pu packages, process the Pu for storage, package the Pu into metallic containers, and safely store the containers in a specially modified storage vault. The location of the SPS will be in the 2736- ZB building and the storage vaults will be in the 2736-Z building of the PFP, as shown in Figure 1-1. The SPS will produce storage canisters that are larger than those currently used for Pu storage at the PFP. Therefore, the existing storage areas within the PFP secure vaults will require modification. Other modifications will be performed on the 2736-ZB building complex to facilitate the installation and operation of the SPS

  10. Proposed Application of Fast Fourier Transform in Near Infra Red Based Non Invasive Blood Glucose Monitoring System

    Science.gov (United States)

    Jenie, R. P.; Iskandar, J.; Kurniawan, A.; Rustami, E.; Syafutra, H.; Nurdin, N. M.; Handoyo, T.; Prabowo, J.; Febryarto, R.; Rahayu, M. S. K.; Damayanthi, E.; Rimbawan; Sukandar, D.; Suryana, Y.; Irzaman; Alatas, H.

    2017-03-01

    Worldwide emergence of glycaemic status related health disorders, such as diabetes and metabolic syndrome, is growing in alarming rate. The objective was to propose new methods for non invasive blood glucose level measurement system, based on implementation of Fast Fourier Transform methods. This was an initial-lab-scale-research. Data on non invasive blood glucose measurement are referred from Scopus, Medline, and Google Scholar, from 2011 until 2016, and was used as design references, combined with in house verification. System was developed in modular fashion, based on aforementioned compiled references. Several preliminary tests to understand relationship between LED and photo-diode responses have been done. Several references were used as non invasive blood glucose measurement tools design basis. Solution is developed in modular fashion. we have proven different sensor responses to water and glucose. Human test for non invasive blood glucose level measurement system is needed.

  11. Dynamic Stability Enhancement of a Multi Machine Electric Power System Using Unified Power Flow Controller

    OpenAIRE

    Ahmad Memaripour; Sayed Mojtaba Shirvani Boroujeni; Reza Hemmati

    2011-01-01

    This study presents the application of Unified Power Flow Controller (UPFC) to improvement dynamic stability of a multi-machine electric power system installed with UPFC. Since UPFC is considered to mitigate Low Frequency Oscillations (LFO) and stability enhancement, therefore a supplementary stabilizer based on UPFC (like power system stabilizer) is designed to reach the defined purpose. Intelligence optimization methods such as Particle Swarm Optimization (PSO) and Genetic Algorithms (GA) a...

  12. Stability and stabilization of nonlinear systems and Takagi-Sugeno's fuzzy models

    Directory of Open Access Journals (Sweden)

    Blanco Yann

    2001-01-01

    Full Text Available This paper outlines a methodology to study the stability of Takagi-Sugeno's (TS fuzzy models. The stability analysis of the TS model is performed using a quadratic Liapunov candidate function. This paper proposes a relaxation of Tanaka's stability condition: unlike related works, the equations to be solved are not Liapunov equations for each rule matrix, but a convex combination of them. The coefficients of this sums depend on the membership functions. This method is applied to the design of continuous controllers for the TS model. Three different control structures are investigated, among which the Parallel Distributed Compensation (PDC. An application to the inverted pendulum is proposed here.

  13. Force measuring optical tweezers system for long time measurements of P pili stability

    Science.gov (United States)

    Andersson, Magnus; Fällman, Erik; Uhlin, Bernt Eric; Axner, Ove

    2006-02-01

    A force-measuring optical tweezers instrumentation and long time measurements of the elongation and retraction of bacterial fimbriae from Uropathogenic E. coli (UPEC) under strain are presented. The instrumentation is presented in some detail. Special emphasis is given to measures taken to reduce the influence of noise and drifts in the system and from the surrounding, which makes long term force measurements possible. Individual P pili from UPEC bacteria were used as a biological model system for repetitive unfolding and refolding cycles of bacterial fimbriae under equilibrium conditions. P pili have evolved into a three-dimensional helix-like structure, the PapA rod, that can be successively and significantly elongated and/or unfolded when exposed to external forces. The instrumentation is used for characterization of the force-vs.-elongation response of the PapA rod of individual P pili, with emphasis on the long time stability of the forced unfolding and refolding of the helical structure of the PapA rod. The results show that the PapA rod is capable of withstanding extensive strain, leading to a complete unfolding of the helical structure, repetitive times during the life cycle of a bacterium without any noticeable alteration of the mechanical properties of the P pili. This function is believed to be importance for UPEC bacteria in vivo since it provides a close contact to a host cell (which is an initial step of invasion) despite urine cleaning attempts.

  14. AxiaLIF system: minimally invasive device for presacral lumbar interbody spinal fusion

    Directory of Open Access Journals (Sweden)

    Rapp SM

    2011-08-01

    Full Text Available Steven M Rapp1, Larry E Miller2,3, Jon E Block31Michigan Spine Institute, Waterford, MI, USA; 2Miller Scientific Consulting Inc, Biltmore Lake, NC, USA; 3Jon E. Block, Ph.D., Inc., San Francisco, CA, USAAbstract: Lumbar fusion is commonly performed to alleviate chronic low back and leg pain secondary to disc degeneration, spondylolisthesis with or without concomitant lumbar spinal stenosis, or chronic lumbar instability. However, the risk of iatrogenic injury during traditional anterior, posterior, and transforaminal open fusion surgery is significant. The axial lumbar interbody fusion (AxiaLIF system is a minimally invasive fusion device that accesses the lumbar (L4–S1 intervertebral disc spaces via a reproducible presacral approach that avoids critical neurovascular and musculoligamentous structures. Since the AxiaLIF system received marketing clearance from the US Food and Drug Administration in 2004, clinical studies of this device have reported high fusion rates without implant subsidence, significant improvements in pain and function, and low complication rates. This paper describes the design and approach of this lumbar fusion system, details the indications for use, and summarizes the clinical experience with the AxiaLIF system to date.Keywords: AxiaLIF, fusion, lumbar, minimally invasive, presacral

  15. New real-time MR image-guided surgical robotic system for minimally invasive precision surgery

    International Nuclear Information System (INIS)

    Hashizume, M.; Yasunaga, T.; Konishi, K.; Tanoue, K.; Ieiri, S.; Kishi, K.; Nakamoto, H.; Ikeda, D.; Sakuma, I.; Fujie, M.; Dohi, T.

    2008-01-01

    To investigate the usefulness of a newly developed magnetic resonance (MR) image-guided surgical robotic system for minimally invasive laparoscopic surgery. The system consists of MR image guidance [interactive scan control (ISC) imaging, three-dimensional (3-D) navigation, and preoperative planning], an MR-compatible operating table, and an MR-compatible master-slave surgical manipulator that can enter the MR gantry. Using this system, we performed in vivo experiments with MR image-guided laparoscopic puncture on three pigs. We used a mimic tumor made of agarose gel and with a diameter of approximately 2 cm. All procedures were successfully performed. The operator only advanced the probe along the guidance device of the manipulator, which was adjusted on the basis of the preoperative plan, and punctured the target while maintaining the operative field using robotic forceps. The position of the probe was monitored continuously with 3-D navigation and 2-D ISC images, as well as the MR-compatible laparoscope. The ISC image was updated every 4 s; no artifact was detected. A newly developed MR image-guided surgical robotic system is feasible for an operator to perform safe and precise minimally invasive procedures. (orig.)

  16. Pythium invasion of plant-based life support systems: biological control and sources

    Science.gov (United States)

    Jenkins, D. G.; Cook, K. L.; Garland, J. L.; Board, K. F.; Sager, J. C. (Principal Investigator)

    2000-01-01

    Invasion of plant-based life support systems by plant pathogens could cause plant disease and disruption of life support capability. Root rot caused by the fungus, Pythium, was observed during tests of prototype plant growth systems containing wheat at the Kennedy Space Center (KSC). We conducted experiments to determine if the presence of complex microbial communities in the plant root zone (rhizosphere) resisted invasion by the Pythium species isolated from the wheat root. Rhizosphere inocula of different complexity (as assayed by community-level physiological profile: CLPP) were developed using a dilution/extinction approach, followed by growth in hydroponic rhizosphere. Pythium growth on wheat roots and concomitant decreases in plant growth were inversely related to the complexity of the inocula during 20-day experiments in static hydroponic systems. Pythium was found on the seeds of several different wheat cultivars used in controlled environmental studies, but it is unclear if the seed-borne fungal strain(s) were identical to the pathogenic strain recovered from the KSC studies. Attempts to control pathogens and their effects in hydroponic life support systems should include early inoculation with complex microbial communities, which is consistent with ecological theory.

  17. Percutaneous Stabilization System Osseofix® for Treatment of Osteoporotic Vertebral Compression Fractures - Clinical and Radiological Results after 12 Months.

    Directory of Open Access Journals (Sweden)

    Stephan Albrecht Ender

    Full Text Available A prospective consecutive cohort study (follow-up study.Our study investigated whether implantation of an expandable titanium mesh cage (Osseofix® is a successful and safe minimally invasive therapy for osteoporotic vertebral compression fractures (VCF. Our experiences, clinical and radiological findings after 12 months follow-up are presented. Kypho- and vertebroplasty are well-established minimally invasive procedures for the treatment of osteoporotic VCF. The main complications associated with both procedures are uncontrolled bone cement leakage. Therefore a suitable alternative has been investigated.During June 2010 to May 2011 24 patients were included with 32 osteoporotic VCF (T6 to L4. All of them were stabilized with the Osseofix® system. Preinterventionally we performed X-ray, MRI, and bone density measurements (DXA. Clinical and radiological results were evaluated preop., postop. and after 12 months postop. based on the Oswestry Disability Index (ODI and the Visual Analogue Scale (VAS, X-ray (Beck Index, Cobb-angle and CT.There was a significant improvement in the mean ODI (70,6% to 30,1% as well as a significant reduction in pain intensity (VAS (7,7 to 1,4 after 12 month. The mean kyphotic angle according to Cobb showed significant improvements (11,7° to 10,4° after 12 months. Postinterventional imaging showed only one case of loss of height in a stabilized vertebral body (3.1%. We saw no changes in posterior vertebral wall or adjacent fractures. Except for one pronounced postoperative hematoma we saw no surgical complications including no cement leakage.Stabilization of symptomatic osteoporotic VCF with Osseofix® system is a safe and effective procedure, even in fractures with posterior wall involvement. The clinical mid-term results are good at a very low complication rate. The Osseofix® system is an interesting alternative to the established procedures of cement augmentation.

  18. The mathematical model of dynamic stabilization system for autonomous car

    Science.gov (United States)

    Saikin, A. M.; Buznikov, S. E.; Shabanov, N. S.; Elkin, D. S.

    2018-02-01

    Leading foreign companies and domestic enterprises carry out extensive researches and developments in the field of control systems for autonomous cars and in the field of improving driver assistance systems. The search for technical solutions, as a rule, is based on heuristic methods and does not always lead to satisfactory results. The purpose of this research is to formalize the road safety problem in the terms of modern control theory, to construct the adequate mathematical model for solving it, including the choice of software and hardware environment. For automatic control of the object, it is necessary to solve the problem of dynamic stabilization in the most complete formulation. The solution quality of the problem on a finite time interval is estimated by the value of the quadratic functional. Car speed, turn angle and additional yaw rate (during car drift or skidding) measurements are performed programmatically by the original virtual sensors. The limit speeds at which drift, skidding or rollover begins are calculated programmatically taking into account the friction coefficient identified in motion. The analysis of the results confirms both the adequacy of the mathematical models and the algorithms and the possibility of implementing the system in the minimal technical configuration.

  19. System design and animal experiment study of a novel minimally invasive surgical robot.

    Science.gov (United States)

    Wang, Wei; Li, Jianmin; Wang, Shuxin; Su, He; Jiang, Xueming

    2016-03-01

    Robot-assisted minimally invasive surgery has shown tremendous advances over the traditional technique. However, currently commercialized systems are large and complicated, which vastly raises the system cost and operation room requirements. A MIS robot named 'MicroHand' was developed over the past few years. The basic principle and the key technologies are analyzed in this paper. Comparison between the proposed robot and the da Vinci system is also presented. Finally, animal experiments were carried out to test the performance of MicroHand. Fifteen animal experiments were carried out from July 2013 to December 2013. All animal experiments were finished successfully. The proposed design method is an effective way to resolve the drawbacks of previous generations of the da Vinci surgical system. The animal experiment results confirmed the feasibility of the design. Copyright © 2015 John Wiley & Sons, Ltd.

  20. Finite-time stability of discrete fractional delay systems: Gronwall inequality and stability criterion

    Science.gov (United States)

    Wu, Guo-Cheng; Baleanu, Dumitru; Zeng, Sheng-Da

    2018-04-01

    This study investigates finite-time stability of Caputo delta fractional difference equations. A generalized Gronwall inequality is given on a finite time domain. A finite-time stability criterion is proposed for fractional differential equations. Then the idea is extended to the discrete fractional case. A linear fractional difference equation with constant delays is considered and finite-time stable conditions are provided. One example is numerically illustrated to support the theoretical result.

  1. Stability boundaries analysis of electric power system with DC transmission based on differential-algebraic equation system

    OpenAIRE

    Susuki, Yoshihiko; Hikihara Takashi; Chiang, HD

    2004-01-01

    This paper discusses stability boundaries in an electric power system with dc transmission based on a differential-algebraic equation (DAE) system. The DAE system is derived to analyze transient stability of the ac/dc power system: the differential equation represents the dynamics of the generator and the dc transmission, and the algebraic equation the active and reactive power relationship between the ac system and the dc transmission. In this paper complete characterization of stability bou...

  2. Spacecraft power system compatibility and stability for the NASA EOS satellite

    Science.gov (United States)

    Sable, Dan M.; Cho, Bo H.; Lee, Fred C.

    1992-01-01

    This paper addresses the problem of system stability of the NASA EOS satellite power system. A potential stability problem exists without a clear specification of the payload input impedance characteristic. Design guidelines are established for the control of the power system and the individual subcomponents to help insure stability with an unknown complex load. A testbed of the EOS power system is employed to verify the analysis.

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

    OpenAIRE

    T. Hussein

    2011-01-01

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

  4. Power System Stabilizer Design Based on a Particle Swarm Optimization Multiobjective Function Implemented Under Graphical Interface

    OpenAIRE

    Ghouraf Djamel Eddine

    2016-01-01

    Power system stability considered a necessary condition for normal functioning of an electrical network. The role of regulation and control systems is to ensure that stability by determining the essential elements that influence it. This paper proposes a Particle Swarm Optimization (PSO) based multiobjective function to tuning optimal parameters of Power System Stabilizer (PSS); this later is used as auxiliary to generator excitation system in order to damp electro mechanicals oscillations of...

  5. Drivers and Controls of the Zebra Mussel Invasion of the Mississippi-Missouri River System

    Science.gov (United States)

    Casagrandi, R.; Mari, L.; Bertuzzo, E.; Gatto, M.; Levin, S. A.; Rodriguez-Iturbe, I.; Rinaldo, A.

    2010-12-01

    The zebra mussel Dreissena polymorpha has been haunting North American inland waters for the past twenty years. Due to the huge population densities reached by local colonies and the species' unparalleled dispersal ability, the zebra mussel represents a major threat from both an ecological and an economic perspective. We propose a novel ecohydrological model for the invasion of inland waters by this alien species and test it against field data gathered within the Mississippi-Missouri river system in North America. To incorporate both hydrologic controls and anthropogenic drivers of the invasion, the proposed multi-layer network model accounts explicitly for zebra mussel demographic dynamics, hydrologic transport and dispersal due to human activities. We show that hydrologic transport alone is not sufficient to explain the spread of the species at the basin scale. We also quantify the role played by commercial navigation in promoting the initial, selective colonization of the river system and show how recreational boating may have determined the capillary penetration of the species into the water system. The role of post-establishment dispersal mechanisms and the effectiveness of possible prevention measures are also discussed in the context of model sensitivity and robustness to reparameterization.

  6. Towards Effective Non-Invasive Brain-Computer Interfaces Dedicated to Gait Rehabilitation Systems

    Directory of Open Access Journals (Sweden)

    Thierry Castermans

    2013-12-01

    Full Text Available In the last few years, significant progress has been made in the field of walk rehabilitation. Motor cortex signals in bipedal monkeys have been interpreted to predict walk kinematics. Epidural electrical stimulation in rats and in one young paraplegic has been realized to partially restore motor control after spinal cord injury. However, these experimental trials are far from being applicable to all patients suffering from motor impairments. Therefore, it is thought that more simple rehabilitation systems are desirable in the meanwhile. The goal of this review is to describe and summarize the progress made in the development of non-invasive brain-computer interfaces dedicated to motor rehabilitation systems. In the first part, the main principles of human locomotion control are presented. The paper then focuses on the mechanisms of supra-spinal centers active during gait, including results from electroencephalography, functional brain imaging technologies [near-infrared spectroscopy (NIRS, functional magnetic resonance imaging (fMRI, positron-emission tomography (PET, single-photon emission-computed tomography (SPECT] and invasive studies. The first brain-computer interface (BCI applications to gait rehabilitation are then presented, with a discussion about the different strategies developed in the field. The challenges to raise for future systems are identified and discussed. Finally, we present some proposals to address these challenges, in order to contribute to the improvement of BCI for gait rehabilitation.

  7. Invasive central nervous system aspergillosis in bone marrow transplantation recipients: an overview

    Energy Technology Data Exchange (ETDEWEB)

    Guermazi, Ali [Department of Radiology, University of California, San Francisco, 350 Parnassus Avenue, Suite 150, San Francisco, CA 94117 (United States); Department of Radiology, Saint-Louis Hospital, AP-HP, Paris (France); Gluckman, Eliane [Department of Bone Marrow Transplantation, Saint-Louis Hospital, AP-HP, Paris (France); Tabti, Bachir [Department of Radiology, Saint-Louis Hospital, AP-HP, Paris (France); Miaux, Yves [Department of Radiology, University of California, San Francisco, 350 Parnassus Avenue, Suite 150, San Francisco, CA 94117 (United States)

    2003-02-01

    Invasive central nervous system aspergillosis is being seen with an increased frequency, particularly due to the increased number of immunosuppressed patients. The major cause of invasive central nervous system aspergillosis is bone marrow transplantation. In most cases, aspergillosis develops in the paranasal sinuses and in the lungs, and secondarily spreads to the brain. Imaging of cerebral aspergillosis may present different patterns depending on the lesion's age and the immunologic status of the patient. Lesions of the spinal cord are far less common but has been encountered in our series. In this article we review the clinical and radiologic features of aspergillosis affecting the central nervous system in patients who underwent bone marrow transplantation. Different CT and MR patterns are presented, including pertinent clinical and pathologic material. Significant morbidity and mortality can be associated with this fungal infection, and it is therefore incumbent upon the radiologist to identify intracranial aspergillosis as early as possible so that appropriate therapy can be administered. (orig.)

  8. 14 CFR 27.672 - Stability augmentation, automatic, and power-operated systems.

    Science.gov (United States)

    2010-01-01

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

  9. 14 CFR 29.672 - Stability augmentation, automatic, and power-operated systems.

    Science.gov (United States)

    2010-01-01

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

  10. 14 CFR 25.672 - Stability augmentation and automatic and power-operated systems.

    Science.gov (United States)

    2010-01-01

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

  11. Improvement of Transient Stability of Power System by System Damping Series Resistor (SDSR)

    OpenAIRE

    上里, 勝実; 千住, 智信; 当銘, 秀之; 高原, 景滋; Uezato, Katsumi; Senjyu, Tomonobu; Toume, Hideyuki; Takahara, Keiji

    1990-01-01

    The system damping resistor is one of the method for improving the transient stability of power systems. The main circuit is the simple construction so that is low cost and is few abnormal surge, and is superior in ability of economy, reliability and maintenance. Conventionally, most of all system damping resistors have adopted the paralleled resistor, whereas the series resistor is used little.In this paper, we investigate the characteristics of the series resistor by comparing with the para...

  12. 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

  13. General local stability criteria for stratified, weakly magnetized rotating systems

    International Nuclear Information System (INIS)

    Balbus, S.A.

    1995-01-01

    We consider the local stability of laminar differential rotation in a weakly magnetized plasma to adiabatic axisymmetric disturbances. Our assumptions are considerably less restrictive than those of previous analyses. The angular velocity need not have cylindrical isorotational surfaces, and a priori convective stability is not assumed. In an unmagnetized gas, stability under these circumstances would be governed by the Ho/iland criteria. These criteria change qualitatively when even a weak magnetic field is present. In a magnetized plasma, the new criteria for stability have the same general form exhibited by the purely hydrodynamical case, but with all angular momentum gradients replaced by angular velocity gradients. Our findings are in accord with those of Papaloizou ampersand Szuszkiewicz, who, using very different methods, considered the stability of iso-rotational field configurations. The results presented here thus point very generally to angular velocity gradients, not angular momentum gradients, as the fundamental stability discriminants in rotating astrophysical plasmas. copyright 1995 The American Astronomical Society

  14. Stability and control of wind farms in power systems

    Energy Technology Data Exchange (ETDEWEB)

    Jauch, C.

    2006-10-15

    The Ph.D. project 'Stability and Control of Wind Farms in Power Systems' deals with some selected problems related to wind power in power systems. With increasing wind power penetration, wind turbines substitute the power production of conventional power plants. Therefore, wind turbines also have to take over the power system stabilisation and control tasks, that were traditionally carried out by conventional power plants. Out of the many aspects related to this problem, this project focuses on transient fault ride-through and power system stabilisation. The selection of turbine types considered in this project is limited to active-stall turbines and variable speed, variable pitch turbines with gearboxes and full-scale converter-connected synchronous generators. As a basis for the project, a study into the state of the art is conducted at the beginning of the project. Grid connection requirements that were in force, or published as drafts, at the time, and scientific literature related to the topic, are studied. The project is based on simulations of wind turbines in a power system simulations tool. Some of the models used in this project were readily available prior to the project; the development of others is part of the project. The most extensive modelling work deals with the design of the electrical part of the variable speed turbine and its controls. To simulate realistic grid operation the wind turbine models are connected to an aggregated model of the Nordic power system. For that purpose the Nordic power system model, which was available prior to the project, is extended with a realistic feeder configuration. It is commonly demanded from modern wind turbines, that they must not disconnect in case of transient faults. Therefore, controllers are designed that enable the two turbine types to ride through transient faults. With these transient fault controllers the wind turbines can stay connected to the grid, such that their generation capacity is

  15. Intrafractional setup errors in patients undergoing non-invasive fixation using an immobilization system during hypofractionated stereotactic radiotherapy for lung tumors

    International Nuclear Information System (INIS)

    Watanabe, Meguru; Onishi, Hiroshi; Kuriyama, Kengo

    2013-01-01

    Intrafractional setup errors during hypofractionated stereotactic radiotherapy (SRT) were investigated on the patient under voluntary breath-holding conditions with non-invasive immobilization on the CT-linac treatment table. A total of 30 patients with primary and metastatic lung tumors were treated with the hypofractionated SRT with a total dose of 48-60 Gy with four treatment fractions. The patient was placed supine and stabilized on the table with non-invasive patient fixation. Intrafractional setup errors in Right/Left (R.L.), Posterior/Anterior (P.A.), and Inferior/Superior (I.S.) dimensions were analyzed with pre- and post-irradiation CT images. The means and one standard deviation of the intrafractional errors were 0.9±0.7 mm (R.L.), 0.9±0.7 mm (P.A.) and 0.5±1.0 mm (I.S.). Setup errors in each session of the treatment demonstrated no statistically significant difference in the mean value between any two sessions. The frequency within 3 mm displacement was 98% in R.L., 98% in P.A. and 97% in I.S. directions. SRT under the non-invasive patient fixation immobilization system with a comparatively loose vacuum pillow demonstrated satisfactory reproducibility of minimal setup errors with voluntary breath-holding conditions that required a small internal margin. (author)

  16. Robust Stability and H∞ Stabilization of Switched Systems with Time-Varying Delays Using Delta Operator Approach

    Directory of Open Access Journals (Sweden)

    Chen Qin

    2013-01-01

    Full Text Available This paper considers the problems of the robust stability and robust H∞ controller design for time-varying delay switched systems using delta operator approach. Based on the average dwell time approach and delta operator theory, a sufficient condition of the robust exponential stability is presented by choosing an appropriate Lyapunov-Krasovskii functional candidate. Then, a state feedback controller is designed such that the resulting closed-loop system is exponentially stable with a guaranteed H∞ performance. The obtained results are formulated in the form of linear matrix inequalities (LMIs. Finally, a numerical example is provided to explicitly illustrate the feasibility and effectiveness of the proposed method.

  17. Car drivers' perceptions of electronic stability control (ESC) systems.

    Science.gov (United States)

    Vadeby, Anna; Wiklund, Mats; Forward, Sonja

    2011-05-01

    As a way to reduce the number of car crashes different in-car safety devices are being introduced. In this paper one such application is being investigated, namely the electronic stability control system (ESC). The study used a survey method, including 2000 private car drivers (1000 driving a car with ESC and 1000 driving a car without ESC). The main objective was to investigate the effect of ESC on driver behaviour. Results show that drivers report that they drive even more carelessly when they believe that they have ESC, than when they do not. Men are more risk prone than women and young drivers more than older drivers. Using the theory of planned behaviour the results show that attitude, subjective norm and perceived control explain between 62% and 67% of driver's variation of intentions to take risks. When descriptive norm was added to the model a small but statistically significant increase was found. The study also shows that more than 35% erroneously believe that their car is equipped with an ESC system. These findings may suggest that driver behaviour could reduce the positive effect ESC has on accidents. It also shows that drivers who purchase a new car are not well informed about what kind of safety devices the car is equipped with. These findings highlight the need for more targeted information to drivers. Copyright © 2010 Elsevier Ltd. All rights reserved.

  18. Non-invasive Continuous Monitoring of Cerebral Edema Using Portable Microwave Based System

    Science.gov (United States)

    Jiang, Yuhao; Zhao, Minji; Wang, Huiqian; Li, Guoquan

    2018-01-01

    A portable non-invasive head detecting system based on microwave technology was developed for evaluation of cerebral edema change inside human brain. Real-time monitoring of cerebral edema in the brain helps the clinician to assess medical condition and treatment. In this work, a microwave signal was transmitted and coupled into an open-end circular waveguide sensor, incident on a 3D printed head phantom, and reflected back to receiver. Theoretically, the operation of this instrument depends on the conductivity contrast between cerebral edema and healthy brain tissues. The efficacy of the proposed detecting system is verified using 3D printed anatomically and dielectrically realistic human head phantoms with simulated cerebral edema targets with different size. Changes in the amplitude of time domain result were shown to be induced by the expansion or decrease of the edema volume. The eventual goal of this proposed head evaluating system is use in the hospital as an effective real-time monitoring tool.

  19. LMI optimization approach to stabilization of time-delay chaotic systems

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  20. Investigation of the stability of collision-less spherically symmetric systems

    Energy Technology Data Exchange (ETDEWEB)

    Polyachenko, V.L.; Shukhman, I.G. (AN SSSR, Leningrad. Inst. Teoreticheskoj Astronomii)

    The matrix equation star is suggested for investigating the large- scale stability of general spherical collisionless star systems. The equation derived is used for a stability analysis of Idlis one-parametric series of distribution functions. It is shown that the stability condition restricts strongly the permissible degree of anisotropy of the stellar velocity distribution.

  1. The Practical Stability of the Linear Systems with the Phase Space Variable Measurability

    Directory of Open Access Journals (Sweden)

    SOPRONIUK, Y.

    2007-04-01

    Full Text Available For the linear transitional systems with the variable measurability of the phase space it was formulated and solved the problem about the practical stability. It was proved the theorem about the criteria of the practical stability, on the base of which it was developed the algorithm of the digital method of the search of the quality criteria of the practical stability.

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

    DEFF Research Database (Denmark)

    Fang, Jiakun; Miao, Lu; Wen, Jinyu

    2013-01-01

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

  3. Use of a dynamic in vitro attachment and invasion system (DIVAS) to determine influence of growth rate on invasion of respiratory epithelial cells by group B Streptococcus.

    Science.gov (United States)

    Malin, G; Paoletti, L C

    2001-11-06

    Expression of capsular polysaccharide (CPS) and some surface proteins by group B Streptococcus (GBS) is regulated by growth rate. We hypothesized that precise control of GBS growth, and thus surface-expressed components, could modulate the ability of GBS to invade eukaryotic cells. To test this hypothesis, a dynamic in vitro attachment and invasion system (DIVAS) was developed that combines the advantages of bacterial growth in continuous culture with tissue culture. Tissue culture flasks were modified with inlet and outlet ports to permit perfusion of GBS. Encapsulated type III GBS strains M781 and COH1 and strains COH1-11 and COH1-13 (transposon mutants of COH1 that express an asialo CPS or are acapsular, respectively) were grown in continuous culture in a chemically defined medium at fast mass doubling time (t(d) = 1.8 h) and slow (t(d) = 11 h) growth rates, conditions previously shown to induce and repress, respectively, type III CPS expression. Encapsulated GBS strains invaded A549 respiratory epithelial cells 20- to 700-fold better at the fast than at the slow growth rate, suggesting a role for CPS. However, unencapsulated GBS were also invasive but only when cultured at the fast growth rate, which indicates that GBS invasion is independent of CPS expression and can be regulated by growth rate. Growth rate-dependent invasion occurred when GBS was grown in continuous culture under glucose-defined, thiamine-defined, and undefined nutrient limitations. These results suggest a growth rate-dependent regulation of GBS pathogenesis and demonstrate the usefulness of DIVAS as a tool in studies of host-microbe interactions.

  4. Phase diagram for a nano-yttria-stabilized zirconia system

    DEFF Research Database (Denmark)

    Asadikiya, Mohammad; Sabarou, Hooman; Chen, Ming

    2016-01-01

    Due to the attractive properties of nanoparticles because of their effective surface area, they have been studied widely. Nano-yttria-stabilized zirconia (n-YSZ) is a ceramic which has been scrutinized extensively in past years. Because of the different stability behavior of n-YSZ in comparison...

  5. Thermal stability of α-amylase in aqueous cosolvent systems

    Indian Academy of Sciences (India)

    Prakash

    Enhancement of the structural stability of enzymes is of great importance for their application in several industrial processes. The mechanism of thermal denaturation depends on various physicochemical parameters of the solution in which the reaction is catalysed. Any process that enhances the structural stability and rate ...

  6. Improvement of the transient stability using SFCL in Korean power systems

    International Nuclear Information System (INIS)

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

    2013-01-01

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

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

    International Nuclear Information System (INIS)

    Wang Guangming

    2010-01-01

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

  8. Comparison of UPFC-Based Stabilizer and PSS Performances on Damping of Power System Oscillations

    OpenAIRE

    M. R. Meshkatoddini; M. Majidi; M. Sadeghierad; H. Lesani

    2009-01-01

    This paper establishes the linearized Phillips-Heffron model of a power system equipped with UPFC and demonstrates the application of the model in analyzing the damping effect of the UPFC and designing UPFC based stabilizer to improve power system oscillation stability. A comprehensive approach to the design of UPFC based stabilizer (power flow control, DC-voltage regulator and damping controller) is presented. In this case, the multi-machine power system with UPFC is studied and an example o...

  9. pth moment asymptotic stability of stochastic delayed hybrid systems with Lévy noise

    Science.gov (United States)

    Yang, Jun; Zhou, Wuneng; Yang, Xueqing; Hu, Xiaotao; Xie, Lili

    2015-09-01

    The problem of pth moment asymptotic stability analysis is considered for stochastic delayed hybrid systems with Lévy noise. By virtue of Itô's formula and M-matrix theories, we propose some sufficient conditions to guarantee the asymptotic stability and exponential stability of the system. The criterion of mean square asymptotic stability is derived as well for delayed neural networks with Lévy noise. A numerical example is provided to show the usefulness of the proposed asymptotic stability criterion.

  10. An AIL family protein promotes type three secretion system-1-independent invasion and pathogenesis of Salmonella enterica serovar Typhi.

    Science.gov (United States)

    Chowdhury, Rimi; Mandal, Rahul S; Ta, Atri; Das, Santasabuj

    2015-04-01

    Adhesion and invasion of Intestinal Epithelial Cells (IECs) are critical for the pathogenesis of Salmonella Typhi, the aetiological agent of human typhoid fever. While type three secretion system-1 (T3SS-1) is a major invasion apparatus of Salmonella, independent invasion mechanisms were described for non-typhoidal Salmonellae. Here, we show that T2942, an AIL-like protein of S. Typhi Ty2 strain, is required for adhesion and invasion of cultured IECs. That invasion was T3SS-1 independent was proved by ectopic expression of T2942 in the non-invasive E. coli BL21 and double-mutant Ty2 (Ty2Δt2942ΔinvG) strains. Laminin and fibronectin were identified as the host-binding partners of T2942 with higher affinity for laminin. Standalone function of T2942 was confirmed by cell adhesion of the recombinant protein, while the protein or anti-T2942 antiserum blocked adhesion/invasion of S. Typhi, indicating specificity. A 20-amino acid extracellular loop was required for invasion, while several loop regions of T2942 contributed to adhesion. Further, T2942 cooperates with laminin-binding T2544 for adhesion and T3SS-1 for invasion. Finally, T2942 was required and synergistically worked with T3SS-1 for pathogenesis of S. Typhi in mice. Considering wide distribution of T2942 among clinical strains, the protein or the 20-mer peptide may be suitable for vaccine development. © 2014 John Wiley & Sons Ltd.

  11. Significant reduction of fluoroscopy repetition with lumbar localization system in minimally invasive spine surgery

    Science.gov (United States)

    Fan, Guoxin; Zhang, Hailong; Gu, Xin; Wang, Chuanfeng; Guan, Xiaofei; Fan, Yunshan; He, Shisheng

    2017-01-01

    Abstract The conventional location methods for minimally invasive spinal surgery (MISS) were mainly based on repeated fluoroscopy in a trial-and-error manner preoperatively and intraoperatively. Localization system mainly consisted of preoperative applied radiopaque frame and intraoperative guiding device, which has the potential to minimize fluoroscopy repetition in MISS. The study aimed to evaluate the efficacy of a novel lumbar localization system in reducing radiation exposure to patients. Included patients underwent minimally invasive transforaminal lumbar interbody fusion (MISTLIF) or percutaneous transforaminal endoscopic discectomy (PTED). Patients treated with novel localization system were regarded as Group A, and patients treated without novel localization system were regarded as Group B. For PTED, The estimated effective dose was 0.41 ± 0.13 mSv in Group A and 0.57 ± 0.14 mSv in Group B (P fluoroscopy exposure time of PTED was 22.18 ± 7.30 seconds in Group A and 30.53 ± 7.56 seconds in Group B (P fluoroscopy exposure time was 25.41 ± 5.52 seconds in Group A and 32.82 ± 5.03 seconds in Group B (P < .001); The estimated cancer risk was 24.90 ± 5.15 (10–6) in Group A and 31.96 ± 5.04 (10–6) in Group B (P < .001). There were also significant differences in localization time and operation time between the 2 groups either for MISTLIF or PTED. The lumbar localization system could be a potential protection strategy for minimizing radiation hazards. PMID:28538369

  12. The Invasive Species Forecasting System (ISFS): An iRODS-Based, Cloud-Enabled Decision Support System for Invasive Species Habitat Suitability Modeling

    Science.gov (United States)

    Gill, Roger; Schnase, John L.

    2012-01-01

    The Invasive Species Forecasting System (ISFS) is an online decision support system that allows users to load point occurrence field sample data for a plant species of interest and quickly generate habitat suitability maps for geographic regions of interest, such as a national park, monument, forest, or refuge. Target customers for ISFS are natural resource managers and decision makers who have a need for scientifically valid, model- based predictions of the habitat suitability of plant species of management concern. In a joint project involving NASA and the Maryland Department of Natural Resources, ISFS has been used to model the potential distribution of Wavyleaf Basketgrass in Maryland's Chesapeake Bay Watershed. Maximum entropy techniques are used to generate predictive maps using predictor datasets derived from remotely sensed data and climate simulation outputs. The workflow to run a model is implemented in an iRODS microservice using a custom ISFS file driver that clips and re-projects data to geographic regions of interest, then shells out to perform MaxEnt processing on the input data. When the model completes, all output files and maps from the model run are registered in iRODS and made accessible to the user. The ISFS user interface is a web browser that uses the iRODS PHP client to interact with the ISFS/iRODS- server. ISFS is designed to reside in a VMware virtual machine running SLES 11 and iRODS 3.0. The ISFS virtual machine is hosted in a VMware vSphere private cloud infrastructure to deliver the online service.

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

    International Nuclear Information System (INIS)

    Hossein-Zadeh, N.; Kalam, A.

    2002-01-01

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

  14. Semi-global output feedback stabilization for a class of nonlinear systems using homogeneous domination approach.

    Science.gov (United States)

    Zhai, Junyong; Du, Haibo

    2013-03-01

    This paper investigates the problem of semi-global stabilization by output feedback for a class of nonlinear systems using homogeneous domination approach. For each subsystem, we first design an output feedback stabilizer for the nominal system without the perturbing nonlinearities. Then, based on the ideas of the homogeneous systems theory and the adding a power integrator technique, a series of homogeneous output feedback stabilizers are constructed recursively for each subsystem and the closed-loop system is rendered semi-globally asymptotically stable. The efficiency of the output feedback stabilizers is demonstrated by a simulation example. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  15. Stabilization for Damping Multimachine Power System with Time-Varying Delays and Sector Saturating Actuator

    Directory of Open Access Journals (Sweden)

    Linlin Ma

    2016-01-01

    Full Text Available This paper studies the stabilization problem for damping multimachine power system with time-varying delays and sector saturating actuator. The multivariable proportional plus derivative (PD type stabilizer is designed by transforming the problem of PD controller design to that of state feedback stabilizer design for a system in descriptor form. A new sufficient condition of closed-loop multimachine power system asymptomatic stability is derived based on the Lyapunov theory. Computer simulation of a two-machine power system has verified the effectiveness and efficiency of the proposed approach.

  16. 77 FR 39206 - Public Hearing on Proposed Rule for Heavy Vehicle Electronic Stability Control Systems

    Science.gov (United States)

    2012-07-02

    ... Control Systems AGENCY: National Highway Traffic Safety Administration (NHTSA), Department of... No. 136, Electronic Stability Control Systems for Heavy Vehicles (77 FR 30766). The standard would... kilograms (26,000 pounds), to be equipped with an electronic stability control (ESC) system that meets the...

  17. Amyloid fibril systems reduce, stabilize and deliver bioavailable nanosized iron

    Science.gov (United States)

    Shen, Yi; Posavec, Lidija; Bolisetty, Sreenath; Hilty, Florentine M.; Nyström, Gustav; Kohlbrecher, Joachim; Hilbe, Monika; Rossi, Antonella; Baumgartner, Jeannine; Zimmermann, Michael B.; Mezzenga, Raffaele

    2017-07-01

    Iron-deficiency anaemia (IDA) is a major global public health problem. A sustainable and cost-effective strategy to reduce IDA is iron fortification of foods, but the most bioavailable fortificants cause adverse organoleptic changes in foods. Iron nanoparticles are a promising solution in food matrices, although their tendency to oxidize and rapidly aggregate in solution severely limits their use in fortification. Amyloid fibrils are protein aggregates initially known for their association with neurodegenerative disorders, but recently described in the context of biological functions in living organisms and emerging as unique biomaterial building blocks. Here, we show an original application for these protein fibrils as efficient carriers for iron fortification. We use biodegradable amyloid fibrils from β-lactoglobulin, an inexpensive milk protein with natural reducing effects, as anti-oxidizing nanocarriers and colloidal stabilizers for iron nanoparticles. The resulting hybrid material forms a stable protein-iron colloidal dispersion that undergoes rapid dissolution and releases iron ions during acidic and enzymatic in vitro digestion. Importantly, this hybrid shows high in vivo iron bioavailability, equivalent to ferrous sulfate in haemoglobin-repletion and stable-isotope studies in rats, but with reduced organoleptic changes in foods. Feeding the rats with these hybrid materials did not result in abnormal iron accumulation in any organs, or changes in whole blood glutathione concentrations, inferring their primary safety. Therefore, these iron-amyloid fibril hybrids emerge as novel, highly effective delivery systems for iron in both solid and liquid matrices.

  18. Electronic properties and stability of graphene oxyradical systems

    International Nuclear Information System (INIS)

    Wang Jinhua; Guo Liyuan; Li Zepeng

    2015-01-01

    An investigation about the electronic properties of a series of graphene patches with O-bonding to zigzag or armchair edges is performed by density functional theory (DFT). The stability, orbital hybridization, spin density, HOMO and LUMO energy for 4a4z-O, 5a5z-O and 6a6z-O graphene oxyradicals are discussed. The 4a4z-z2, 5a5z-z3 and 6a6z-z3 are the most stable structure in their individual graphene oxyradicals systems and the corresponding C=O bond length is about 0.1231 nm. This shows that the structure with O-bonding to central positions of zigzag edges is the most stable one indicating its “safe harbor” status. Meanwhile, spin density changes obviously after O-bonding to zigzag edge of graphene. As the presumptive outer effects, folding along an axis at z3 position would deprive the “safe harbor” status with O-bonding to zigzag edge. This inspires the exploration of new ways in absorbing or storage energy behavior and intermediate of combustion can be understood better. (author)

  19. Immobilization, stabilization and patterning techniques for enzyme based sensor systems.

    Energy Technology Data Exchange (ETDEWEB)

    Flounders, A.W.; Carichner, S.C.; Singh, A.K.; Volponi, J.V.; Schoeniger, J.S.; Wally, K.

    1997-01-01

    Sandia National Laboratories has recently opened the Chemical and Radiation Detection Laboratory (CRDL) in Livermore CA to address the detection needs of a variety of government agencies (e.g., Department of Energy, Environmental Protection Agency, Department of Agriculture) as well as provide a fertile environment for the cooperative development of new industrial technologies. This laboratory consolidates a variety of existing chemical and radiation detection efforts and enables Sandia to expand into the novel area of biochemically based sensors. One aspect of this biosensor effort is further development and optimization of enzyme modified field effect transistors (EnFETs). Recent work has focused upon covalent attachment of enzymes to silicon dioxide and silicon nitride surfaces for EnFET fabrication. They are also investigating methods to pattern immobilized proteins; a critical component for development of array-based sensor systems. Novel enzyme stabilization procedures are key to patterning immobilized enzyme layers while maintaining enzyme activity. Results related to maximized enzyme loading, optimized enzyme activity and fluorescent imaging of patterned surfaces will be presented.

  20. A Novel Fuzzy Logic Based Power System Stabilizer for a Multimachine System

    OpenAIRE

    Singh, Anup; Sen, Indraneel

    2003-01-01

    This paper describes the design of a Fuzzy logic based controller to counter the small signal oscillatory instability in power system. The stabilizing signal is computed in real time using suitable fuzzy membership functions depending upon the state of the generator on the speed-acceleration phase plane. The use of output membership function permits further fine tuning of the controller parameters for varied system configurations specially in multimachine environment. The efficacy of the p...

  1. The urokinase-system in tumor tissue stroma of the breast and breast cancer cell invasion.

    Science.gov (United States)

    Hildenbrand, Ralf; Schaaf, Antonela

    2009-01-01

    The urokinase-system has been implicated in tumor spread. The serine protease urokinase-type plasminogen activator (uPA), its receptor (uPAR) and its inhibitor (PAI-1) are involved in the control of extracellular turnover, cell migration, invasion, cell signalling, proliferation, apoptosis and angiogenesis leading to a variety of different responses, under both physiological and pathological conditions. uPA and PAI-1 were the first novel tumor biological factors to be validated at the highest level of evidence regarding their clinical utility in breast cancer. However, it is unclear whether it is their (relative) levels in the tumor stroma or in the tumor cells themselves that is the most relevant to patients outcome. This is the first study in which tumor cells and stromal tissue of invasive breast carcinomas were separated by laser capture microdissection followed by ELISA-based determination of the uPA, uPAR and PAI-1 levels. In addition, we localized uPA, uPAR and PAI-1 distribution in invasive breast cancer (n=30) and in ductal carcinoma in situ (DCIS, n=30) by immunohistochemistry and in situ hybridization. We have demonstrated that no significant differences between uPA, uPAR and PAI-1 levels in tumor stroma only, tumor cells only and not separated breast cancer tissue exist (p>0.05). Our results suggest that similar expression levels of these factors in both compartments and in not separated breast cancer tissue may have the same impact on the clinical behavior of breast cancer. These results are an important issue for practical use of tissue sampling. For using uPA and PAI-1 levels as prognostic and predictive factors in breast cancer the quantity of tumor stroma in the tumor tissue specimen is not relevant for assessment patients outcome. Our results were confirmed by immunohistochemistry and in situ hybridization analysis showing that in nearly all cases of invasive carcinomas and DCIS fibroblasts as well as macrophages strongly express uPA, uPAR and PAI

  2. Design of waste stabilization pond systems: A review.

    Science.gov (United States)

    Ho, Long T; Van Echelpoel, Wout; Goethals, Peter L M

    2017-10-15

    A better design instruction for waste stabilization ponds is needed due to their growing application for wastewater purification, increasingly strict environmental regulations, and the fact that most of previous design manuals are outdated. To critically review model-based designs of typical pond treatment systems, this paper analyzed more than 150 articles, books, and reports from 1956 to 2016. The models developed in these publications ranged from simple rules and equations to more complex first-order and mechanistic models. From a case study on all four approaches, it appeared that rules of thumb is no longer a proper tool for pond designs due to its low design specification and very high output variability and uncertainty. On the other hand, at the beginning phase of design process or in case of low pressure over land and moderate water quality required, regression equations can be useful to form an idea for pond dimensions. More importantly, mechanistic models proved their capacity of generating more precise and comprehensive designs but still need to overcome their lack of calibration and validation, and overparameterization. In another case study, an essential but often overlooked role of uncertainty analysis in pond designs was investigated via a comparison between deterministic and uncertainty-based approaches. Unlike applying a safety factor representing all uncertainty sources, probabilistic designs quantify the uncertainty of model outputs by including prior uncertainty of inputs and parameters, which generates more scientifically reliable outcomes for decision makers. Based on these findings, we advise engineers and designers to shift from the conventional approaches to more innovative and economic tools which are suitable for dealing with large variations of natural biological systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Voltage stability via energy function analysis on reduced order model of power system

    OpenAIRE

    ÇİFCİ, Ahmet; UYAROĞLU, Yılmaz; YALÇIN, Mehmet Ali

    2014-01-01

    A power system is a typical nonlinear dynamical system and voltage stability is an important subject of power system stability. This paper describes the use of the variable gradient method in a reduced order model of a single-machine infinite-bus power system. Additionally, the system's Lyapunov (energy) function is created and thus the system's energy level changes' effects on the system's stability are shown using the MACSYMA program. The Lyapunov ...

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    Recently, the security and stability of power system with large amount of wind power are the concerned issues, especially the transient stability. In Denmark, the onshore and offshore wind farms are connected to distribution system and transmission system respectively. The control and protection...... methodologies of onshore and offshore wind farms definitely affect the transient stability of power system. In this paper, the onshore and offshore wind farms are modeled in detail in order to assess the transient stability of western Danish power system. Further, the computation of critical clearing time (CCT......) in different scenarios is proposed to evaluate the vulnerable areas in western Danish power system. The result of CCTs in different scenarios can evaluate the impact of wind power on power system transient stability. Besides, some other influencing factors such as the load level of generators in central power...

  5. Analog System of Detonations with Loss and Stability of the Analog System

    Science.gov (United States)

    Sun, Yuanxiang; Wang, Cheng; Group of Computationa Fluid Dynamics Team

    2017-06-01

    Analog system of detonation is a simplified model of the Euler system. Analog system removes unnecessary details of the Euler system and reduces mathematical difficulty Analog system with losses and reaction mechanism that applicable for condensed-phase detonation is studied to examine whether the analog system in this paper is valid Details are as follows: 1. The relationship of detonation velocity vs. loss parameter is analytically solved, and a minimal state-dependence of the reaction rate n required for this relationship to exhibit a critical behavior (i.e., a turning point) is examined The results agree with the limits which derived from Euler system. 2. Normal-mode method is used to study the stability of the analog system. A radiation (closure) condition is derived and applied at the end of the reaction zone. An analysis is performed to investigate whether the ideal, steady-state detonation can keep stable to small perturbations 3. Because analog system with loss can be more unstable than the ideal one. An numerical simulation is used to examine the detonation stability near the loss limits. The results above show that the analog system is basically valid for condensed-phase detonation.

  6. Year 1 Assessment of the Unit Focused Stability Manning System

    National Research Council Canada - National Science Library

    Smith, Monte

    2004-01-01

    .... Under UFS, combat forces are formed, trained, and deployed as intact units, with resulting stability and opportunity for accretive training serving to increase combat skills and cohesion above levels...

  7. SPECTRAL ANALYSIS OF GAS BEARING SYSTEMS FOR STABILITY STUDIES

    Science.gov (United States)

    latter case is given in terms of a herringbone-grooved journal bearing . This method of stability analysis is applicable to both thrust and journal bearings for both whirl and pneumatic-hammer instabilities.

  8. γδ Intraepithelial Lymphocyte Migration Limits Transepithelial Pathogen Invasion and Systemic Disease in Mice.

    Science.gov (United States)

    Edelblum, Karen L; Singh, Gurminder; Odenwald, Matthew A; Lingaraju, Amulya; El Bissati, Kamal; McLeod, Rima; Sperling, Anne I; Turner, Jerrold R

    2015-06-01

    Intraepithelial lymphocytes that express the γδ T-cell receptor (γδ IELs) limit pathogen translocation across the intestinal epithelium by unknown mechanisms. We investigated whether γδ IEL migration and interaction with epithelial cells promote mucosal barrier maintenance during enteric infection. Salmonella typhimurium or Toxoplasma gondii were administered to knockout (KO) mice lacking either the T cell receptor δ chain (Tcrd) or CD103, or control TcrdEGFP C57BL/6 reporter mice. Intravital microscopy was used to visualize migration of green fluorescent protein (GFP)-tagged γδ T cells within the small intestinal mucosa of mice infected with DsRed-labeled S typhimurium. Mixed bone marrow chimeras were generated to assess the effects of γδ IEL migration on early pathogen invasion and chronic systemic infection. Morphometric analyses of intravital video microscopy data showed that γδ IELs rapidly localized to and remained near epithelial cells in direct contact with bacteria. Within 1 hour, greater numbers of T gondii or S typhimurium were present within mucosae of mice with migration-defective occludin KO γδ T cells, compared with controls. Pathogen invasion in Tcrd KO mice was quantitatively similar to that in mice with occludin-deficient γδ T cells, whereas invasion in CD103 KO mice, which have increased migration of γδ T cells into the lateral intercellular space, was reduced by 63%. Consistent with a role of γδ T-cell migration in early host defense, systemic salmonellosis developed more rapidly and with greater severity in mice with occludin-deficient γδ IELs, relative to those with wild-type or CD103 KO γδ IELs. In mice, intraepithelial migration to epithelial cells in contact with pathogens is essential to γδ IEL surveillance and immediate host defense. γδ IEL occludin is required for early surveillance that limits systemic disease. Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved.

  9. 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 ...

  10. Some Thoughts on Stability in Nonlinear Periodic Focusing Systems [Addendum

    Science.gov (United States)

    McMillan, Edwin M.

    1968-03-29

    Addendum to September 5, 1967 report with the same title and with the abstract: A brief discussion is given of the long-term stability of particle motions through periodic focusing structures containing lumped nonlinear elements. A method is presented whereby one can specify the nonlinear elements in such a way as to generate a variety of structures in which the motion has long-term stability.

  11. Homogeneous piecewise polynomial Lyapunov function for robust stability of uncertain piecewise linear system

    International Nuclear Information System (INIS)

    BenAbdallah, Abdallah; Hammami, Mohamed Ali; Kallel, Jalel

    2009-01-01

    In this paper we present some sufficient conditions for the robust stability and stabilization of time invariant uncertain piecewise linear system using homogenous piecewise polynomial Lyapunov function. The proposed conditions are given in terms of linear matrix inequalities which can be numerically solved. An application of the obtained result is given. It consists in resolving the stabilization of piecewise uncertain linear control systems by using a state piecewise linear feedback.

  12. A Developed Graphical User Interface for Power System Stability and Robustness Studies

    OpenAIRE

    GHOURAF Djamel Eddine; NACERI Abdellatif; ABID Mohamed; KABI Wahiba

    2015-01-01

    This paper present the realization and development of a graphical user interface (GUI) to studied the stability and robustness of power systems (analysis and synthesis), using Conventional Power System Stabilizers (CPSS - realized on PID scheme) or advanced controllers (based on adaptive and robust control), and applied on automatic excitation control of powerful synchronous generators, to improve dynamic performances and robustness. The GUI is a useful average to facilitate stability study o...

  13. Modeling invasive alien plant species in river systems: Interaction with native ecosystem engineers and effects on hydro-morphodynamic processes

    Science.gov (United States)

    van Oorschot, M.; Kleinhans, M. G.; Geerling, G. W.; Egger, G.; Leuven, R. S. E. W.; Middelkoop, H.

    2017-08-01

    Invasive alien plant species negatively impact native plant communities by out-competing species or changing abiotic and biotic conditions in their introduced range. River systems are especially vulnerable to biological invasions, because waterways can function as invasion corridors. Understanding interactions of invasive and native species and their combined effects on river dynamics is essential for developing cost-effective management strategies. However, numerical models for simulating long-term effects of these processes are lacking. This paper investigates how an invasive alien plant species affects native riparian vegetation and hydro-morphodynamics. A morphodynamic model has been coupled to a dynamic vegetation model that predicts establishment, growth and mortality of riparian trees. We introduced an invasive alien species with life-history traits based on Japanese Knotweed (Fallopia japonica), and investigated effects of low- and high propagule pressure on invasion speed, native vegetation and hydro-morphodynamic processes. Results show that high propagule pressure leads to a decline in native species cover due to competition and the creation of unfavorable native colonization sites. With low propagule pressure the invader facilitates native seedling survival by creating favorable hydro-morphodynamic conditions at colonization sites. With high invader abundance, water levels are raised and sediment transport is reduced during the growing season. In winter, when the above-ground invader biomass is gone, results are reversed and the floodplain is more prone to erosion. Invasion effects thus depend on seasonal above- and below ground dynamic vegetation properties and persistence of the invader, on the characteristics of native species it replaces, and the combined interactions with hydro-morphodynamics.

  14. Wireless network system based multi-non-invasive sensors for smart home

    Science.gov (United States)

    Issa Ahmed, Rudhwan

    There are several techniques that have been implemented for smart homes usage; however, most of these techniques are limited to a few sensors. Many of these methods neither meet the needs of the user nor are cost-effective. This thesis discusses the design, development, and implementation of a wireless network system, based on multi-non-invasive sensors for smart home environments. This system has the potential to be used as a means to accurately, and remotely, determine the activities of daily living by continuously monitoring relatively simple parameters that measure the interaction between users and their surrounding environment. We designed and developed a prototype system to meet the specific needs of the elderly population. Unlike audio-video based health monitoring systems (which have associated problems such as the encroachment of privacy), the developed system's distinct features ensure privacy and are almost invisible to the occupants, thus increasing the acceptance levels of this system in household environments. The developed system not only achieved high levels of accuracy, but it is also portable, easy to use, cost-effective, and requires low data rates and less power compared to other wireless devices such as Wi-Fi, Bluetooth, wireless USB, Ultra wideband (UWB), or Infrared (IR) wireless. Field testing of the prototype system was conducted at different locations inside and outside of the Minto Building (Centre for Advanced Studies in Engineering at Carleton University) as well as other locations, such as the washroom, kitchen, and living room of a prototype apartment. The main goal of the testing was to determine the range of the prototype system and the functionality of each sensor in different environments. After it was verified that the system operated well in all of the tested environments, data were then collected at the different locations for analysis and interpretation in order to identify the activities of daily living of an occupant.

  15. Improved Step Response of Power System Stabilizer Using Fuzzy Logic Controller

    OpenAIRE

    Kiran, Nagulapati; Kumar, M. Sudheer; Raju, M. Naga

    2014-01-01

    As every power system is constantly being subjected to disturbances, we should see that these disturbances do not make the system unstable. Therefor additional signals derived from speed deviation, excitation deviation and accelerating power are injected into voltage regulators. The device to provide these signals is referred as power system stabilizer. The use of power system stabilizers has become very common in operation of large electric power systems. The conventional PSS which uses lead...

  16. Dynamic stability enhancement of a multimachine electric power system using STATCOM

    OpenAIRE

    BOROUJENI, Hasan Fayazi; HEMMATI, Reza; BOROUJENI, Sayed Mojtaba Shirvani

    2011-01-01

    With the expansion of electric power systems, the size and complexity of the network is increased. One of the most important drawbacks of network expansion is the reduction in the damping torque of the whole system. The lack of damping torque can lead to fluctuations and instability in the power system. With regard to this problem, power system stabilizers (PSSs) have been widely utilized to improve power system stability. However, due to some drawbacks of the conventional PSSs, the ...

  17. Non-invasive detection of murals with pulsed terahertz reflected imaging system

    Science.gov (United States)

    Yuan, Minjie; Sun, Wenfeng; Wang, Xinke; Ye, Jiasheng; Wang, Sen; Zhang, Qunxi; Zhang, Yan

    2015-11-01

    Pulsed terahertz reflected imaging technology has been expected to have great potential for the non-invasive analysis of artworks. In this paper, three types of defects hidden in the plaster used to simulate the cases of defects in the murals, have been investigated by a pulsed terahertz reflected imaging system. These preset defects include a circular groove, a cross-shaped slit and a piece of "Y-type" metal plate built in the plaster. With the terahertz reflective tomography, information about defects has been determined involving the thickness from the surface of sample to the built-in defect, the profile and distribution of the defect. Additionally, three-dimensional analyses have been performed in order to reveal the internal structure of defects. Terahertz reflective imaging can be applied to the defect investigation of the murals.

  18. Evolving minimally invasive spine surgery: a surgeon's perspective on technological convergence and digital or control system.

    Science.gov (United States)

    Chiu, John C; Maziad, Ali M; Rappard, George; Thacker, James T; Liu, Brent; Documet, Jorge

    2010-04-01

    Degenerated spinal disc and spinal stenosis are common problems requiring decompressive spinal surgery. Traditional open spinal discectomy is associated with significant tissue trauma, greater morbidity/complications, scarring, often longer term of convalescence, and even destabilization of the spine. Therefore, the pursuit of less traumatic minimally invasive spine surgery (MISS) began. The trend of spinal surgery is rapidly moving toward MISS. MISS is a technologically dependent surgery, and requires increased utilization of advanced endoscopic surgical instruments, imaging-video technology, and tissue modulation technology for performing spinal surgery in a digital operating room (DOR). It requires seamless connectivity and control to perform the surgical procedures in a precise and orchestrated manner. A new integrated DOR, the technological convergence and control system SurgMatix(R), was created in response to the need and to facilitate MISS with "organized control instead of organized chaos" in the endoscopic OR suite. It facilitates the performance, training, and further development of MISS.

  19. Non invasive techniques for the study of the extracranial carotid arterial system

    International Nuclear Information System (INIS)

    Ameneiro Perez, Santiago; Alvarez Sanchez, Jose Antonio; Aldama Figueroa, Alfredo

    2000-01-01

    A review of the noninvasive diagnostic techniques that have been historically used to detect the stenoocclussive lesions of the extracranial carotid arterial system is made. The technological development and the new therapeutic criteria to prevent strokes caused by these lesions have encouraged research in this field. A review of the most used techniques at present: mode B ultrasound, duplex ultrasound and color duplex ultrasound, as well as of the advantages and disadvantages of each one is made. Nowadays, there are hemodynamic criteria together with these techniques that evaluate the stenosis degrees and the characteristics of the lesions with accuracy enough to substitute in most of the cases the invasive and more expensive diagnostic angiographic methods

  20. Apnea induced by respiratory syncytial virus infection is not associated with viral invasion of the central nervous system.

    Science.gov (United States)

    Erez, Daniella Levy; Yarden-Bilavsky, Havatzelet; Mendelson, Ella; Yuhas, Yael; Ashkenazi, Shai; Nahum, Elhanan; Berent, Eva; Hindiyeh, Musa; Bilavsky, Efraim

    2014-08-01

    We aimed to study whether direct central nervous system invasion is responsible for the neurologic manifestations seen in hospitalized infants with respiratory syncytial virus (RSV) infection. Cerebrospinal fluid from infants with RSV infection was tested for the detection of the following respiratory RNA viruses: RSV, influenza A and B, pandemic influenza H1N1, Parainfluenza-3, human metapneumovirus, adenovirus, parechovirus and enterovirus. All children tested negative for the presence of viral material in the cerebrospinal fluid. Our results support the notion that the mechanism of RSV-induced neurologic manifestations, including apnea, is not direct central nervous system invasion.

  1. 77 FR 30765 - Federal Motor Vehicle Safety Standards; Electronic Stability Control Systems for Heavy Vehicles

    Science.gov (United States)

    2012-05-23

    ... Traffic Safety Administration 49 CFR Part 571 Federal Motor Vehicle Safety Standards; Electronic Stability Control Systems for Heavy Vehicles; Proposed Rule #0;#0;Federal Register / Vol. 77 , No. 100 / Wednesday... Vehicle Safety Standards; Electronic Stability Control Systems for Heavy Vehicles AGENCY: National Highway...

  2. Power System Transient Stability Improvement Using Demand Side Management in Competitive Electricity Markets

    DEFF Research Database (Denmark)

    Hu, Weihao; Wang, Chunqi; Chen, Zhe

    2012-01-01

    for demand side management generates different load profiles and may provide an opportunity to improve the transient stability of power systems with high wind power penetrations. In this paper, the idea of the power system transient stability improvement by using optimal load response to the electricity...

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

    Science.gov (United States)

    Ivanitskii, G. R.

    2017-10-01

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

  4. Historical Building Stability Monitoring by Means of a Cosmic Ray Tracking System

    Energy Technology Data Exchange (ETDEWEB)

    Zenoni, Aldo [Department of Mechanical and Industrial Engineering of the University of Brescia, Via Branze 38, 25123 Brescia (Italy); INFN Sezione di Pavia, Via Bassi 6, 27100 Pavia (Italy)

    2015-07-01

    Cosmic ray radiation is mostly composed, at sea level, by high energy muons, which are highly penetrating particles capable of crossing kilometers of rock. The ubiquitous and steady presence at the Earth's surface and the high penetration capability have motivated the use of cosmic ray radiation also in fields beyond particle physics, from geology, archaeology, speleology to industrial applications and homeland security. In particular, in recent years, the novel technique of muon tomography has been proposed, with the aim of performing non invasive inspection of large non accessible volumes, material atomic number Z and density discrimination, and three dimension image reconstruction of the inspected volume. In the present paper, after a short recall of the physical principles and mathematical formalism on which muon tomography is based, a number of examples of application of the novel technique in industry and homeland security issues is given. Moreover, a new application of cosmic rays detection techniques in the field of civil engineering is proposed. The aim is the monitoring of the stability of large structures, in particular the static monitoring of historical buildings, where conservation constraints are more severe and the time evolution of the deformation phenomena under study may be of the order of months or years. The new technique may be seen, in some way, as the reverse problem of muon tomography. As a significant case study, the monitoring of the wooden vaulted roof of the Palazzo della Loggia in the town of Brescia, in Italy, has been considered. The feasibility as well as the performances and limitations of a monitoring system based on cosmic ray tracking have been studied by Monte Carlo simulation and discussed in comparison with more traditional monitoring systems. (authors)

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

    Science.gov (United States)

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

    2015-09-01

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

  6. Frequency scanning-based stability analysis method for grid-connected inverter system

    DEFF Research Database (Denmark)

    Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion with conside......This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion...... with consideration of the inverter nonlinearities. Small current disturbance is injected into grid-connected inverter system in a particular frequency range, and the impedance is computed according to the harmonic-frequency response using Fourier analysis, and then the stability is predicted on the basis...... of the impedance stability criterion. The stability issues of grid-connected inverters with grid-current feedback and the converter-current feedback are addressed using the proposed method. The results obtained from simulation and experiments validate the effectiveness of the method. The frequency scanning...

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

    Directory of Open Access Journals (Sweden)

    Zumatov S. S.

    2017-12-01

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

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

    Science.gov (United States)

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

    2018-01-01

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

  9. CISM Session on Bifurcation and Stability of Dissipative Systems

    CERN Document Server

    1993-01-01

    The first theme concerns the plastic buckling of structures in the spirit of Hill’s classical approach. Non-bifurcation and stability criteria are introduced and post-bifurcation analysis performed by asymptotic development method in relation with Hutchinson’s work. Some recent results on the generalized standard model are given and their connection to Hill’s general formulation is presented. Instability phenomena of inelastic flow processes such as strain localization and necking are discussed. The second theme concerns stability and bifurcation problems in internally damaged or cracked colids. In brittle fracture or brittle damage, the evolution law of crack lengths or damage parameters is time-independent like in plasticity and leads to a similar mathematical description of the quasi-static evolution. Stability and non-bifurcation criteria in the sense of Hill can be again obtained from the discussion of the rate response.

  10. Respiratory System Function in Patients After Minimally Invasive Aortic Valve Replacement Surgery: A Case Control Study.

    Science.gov (United States)

    Stoliński, Jarosław; Musiał, Robert; Plicner, Dariusz; Andres, Janusz

    The aim of the study was to comparatively analyze respiratory system function after minimally invasive, through right minithoracotomy aortic valve replacement (RT-AVR) to conventional AVR. Analysis of 201 patients scheduled for RT-AVR and 316 for AVR between January 2010 and November 2013. Complications of the respiratory system and pulmonary functional status are presented. Complications of the respiratory system occurred in 16.8% of AVR and 11.0% of RT-AVR patients (P = 0.067). The rate of pleural effusions, thoracenteses, pneumonias, or phrenic nerve dysfunctions was not significantly different between groups. Perioperative mortality was 1.9% in AVR and 1.0% in RT-AVR (P = 0.417). Mechanical ventilation time after surgery was 9.7 ± 5.9 hours for AVR and 7.2 ± 3.2 hours for RT-AVR patients (P respiratory system complications. Spirometry examinations revealed that pulmonary functional status was more impaired after AVR in comparison with RT-AVR surgery.

  11. A Non-Invasive Multichannel Hybrid Fiber-Optic Sensor System for Vital Sign Monitoring

    Directory of Open Access Journals (Sweden)

    Marcel Fajkus

    2017-01-01

    Full Text Available In this article, we briefly describe the design, construction, and functional verification of a hybrid multichannel fiber-optic sensor system for basic vital sign monitoring. This sensor uses a novel non-invasive measurement probe based on the fiber Bragg grating (FBG. The probe is composed of two FBGs encapsulated inside a polydimethylsiloxane polymer (PDMS. The PDMS is non-reactive to human skin and resistant to electromagnetic waves, UV absorption, and radiation. We emphasize the construction of the probe to be specifically used for basic vital sign monitoring such as body temperature, respiratory rate and heart rate. The proposed sensor system can continuously process incoming signals from up to 128 individuals. We first present the overall design of this novel multichannel sensor and then elaborate on how it has the potential to simplify vital sign monitoring and consequently improve the comfort level of patients in long-term health care facilities, hospitals and clinics. The reference ECG signal was acquired with the use of standard gel electrodes fixed to the monitored person's chest using a real-time monitoring system for ECG signals with virtual instrumentation. The outcomes of these experiments have unambiguously proved the functionality of the sensor system and will be used to inform our future research in this fast developing and emerging field.

  12. Microprocessor supervised stability control system for the united power system of Middle Volga in fault conditions

    Energy Technology Data Exchange (ETDEWEB)

    Berdnikov, V.I.; Birgel, E.R.; Kovalev, V.D.; Kuznestov, A.N.

    1994-12-31

    The development of the 500 kV UPS of Middle Volga, the complication of its configuration and operating conditions particularly in connection with concentration of the generating power at Balakovo NPS have aggravated the problem of stability of the Middle Volga UPS when high power is transmitted along the 500 kV transient system. In this case the necessity for improving control actions` dosage accuracy has also appeared. This work discusses solution to the above mentioned issue. (author) 3 figs.

  13. Non-invasive brain-computer interface system: towards its application as assistive technology.

    Science.gov (United States)

    Cincotti, Febo; Mattia, Donatella; Aloise, Fabio; Bufalari, Simona; Schalk, Gerwin; Oriolo, Giuseppe; Cherubini, Andrea; Marciani, Maria Grazia; Babiloni, Fabio

    2008-04-15

    The quality of life of people suffering from severe motor disabilities can benefit from the use of current assistive technology capable of ameliorating communication, house-environment management and mobility, according to the user's residual motor abilities. Brain-computer interfaces (BCIs) are systems that can translate brain activity into signals that control external devices. Thus they can represent the only technology for severely paralyzed patients to increase or maintain their communication and control options. Here we report on a pilot study in which a system was implemented and validated to allow disabled persons to improve or recover their mobility (directly or by emulation) and communication within the surrounding environment. The system is based on a software controller that offers to the user a communication interface that is matched with the individual's residual motor abilities. Patients (n=14) with severe motor disabilities due to progressive neurodegenerative disorders were trained to use the system prototype under a rehabilitation program carried out in a house-like furnished space. All users utilized regular assistive control options (e.g., microswitches or head trackers). In addition, four subjects learned to operate the system by means of a non-invasive EEG-based BCI. This system was controlled by the subjects' voluntary modulations of EEG sensorimotor rhythms recorded on the scalp; this skill was learnt even though the subjects have not had control over their limbs for a long time. We conclude that such a prototype system, which integrates several different assistive technologies including a BCI system, can potentially facilitate the translation from pre-clinical demonstrations to a clinical useful BCI.

  14. An Integrated Glucose Sensor with an All-Solid-State Sodium Ion-Selective Electrode for a Minimally Invasive Glucose Monitoring System

    Directory of Open Access Journals (Sweden)

    Junko Kojima

    2015-06-01

    Full Text Available We developed a minimally invasive glucose monitoring system that uses a microneedle to permeate the skin surface and a small hydrogel to accumulate interstitial fluid glucose. The measurement of glucose and sodium ion levels in the hydrogel is required for estimating glucose levels in blood; therefore, we developed a small, enzyme-fixed glucose sensor with a high-selectivity, all-solid-state, sodium ion-selective electrode (ISE integrated into its design. The glucose sensor immobilized glucose oxidase showed a good correlation between the glucose levels in the hydrogels and the reference glucose levels (r > 0.99, and exhibited a good precision (coefficient of variation = 2.9%, 0.6 mg/dL. In the design of the sodium ISEs, we used the insertion material Na0.33MnO2 as the inner contact layer and DD16C5 exhibiting high Na+/K+ selectivity as the ionophore. The developed sodium ISE exhibited high selectivity (\\( \\log \\,k^{pot}_{Na,K} = -2.8\\ and good potential stability. The sodium ISE could measure 0.4 mM (10−3.4 M sodium ion levels in the hydrogels containing 268 mM (10−0.57 M KCl. The small integrated sensor (ϕ < 10 mm detected glucose and sodium ions in hydrogels simultaneously within 1 min, and it exhibited sufficient performance for use as a minimally invasive glucose monitoring system.

  15. Experimental research of "microcable in a microconduct" system stability to effect of freezing water

    Science.gov (United States)

    Andreev, Vladimir A.; Burdin, Vladimir A.; Nikulina, Tatiana G.; Alekhin, Ivan N.; Gavryushin, Sergey A.; Nikulin, Aleksey G.; Praporshchikov, Denis E.

    2011-12-01

    Results of experimental researches of "optical microcable in a microduct" system stability to effect of freezing water are presented. It is shown this system is steadier to water freezing in comparison to lighten optical cable in protective polymer tube.

  16. EHPS Handling Stability Analysis of Electric Bus Based on System Identification Method

    Science.gov (United States)

    Zhang, Ni; Liu, Hai-mei; Bei, Shao-yi; Li, Bo; Zhao, Jing-bo

    2017-09-01

    Electric hydraulic assist force steering system (EHPS system) is the steering system of electric bus, this paper presents a method of EHPS handling stability analysis based on system identification method according to the handling stability of EHPS system for electric bus. The simulation model of electro-hydraulic assist force steering system EHPS is established by using the software AMESim, and making a quantitative analysis on the characteristics of the electric assist force assisted steering system, the assist force response and stability. At the same time, we study the stability of vehicle, including hunting, transient response, return experiment, the results show that the HPS and EHPS by comparing the simulation: It improves the portability, road sense, transient response and return performance after loading the system, which verifiy the effectiveness of the control strategy that improves vehicle steering performance, and it provides the basis for the optimization of control methods in the future.

  17. Evaluation of Laser Stabilization and Imaging Systems for LCLS-II - Oral Presentation

    Energy Technology Data Exchange (ETDEWEB)

    Barry, Matthew; /Auburn U.

    2015-08-19

    This presentation covers data collected on two commercial laser stabilization systems, Guidestar-II and MRC, and two optical imaging systems. Additionally, general information about LCLS-II and how to go about continuing-testing is covered.

  18. Total abdominal hysterectomy versus minimal-invasive hysterectomy: a systemic review and meta-analysis

    International Nuclear Information System (INIS)

    Aragon Palmero, Felipe Jorge; Exposito Exposito, Moises

    2011-01-01

    INTRODUCTION. At the present time three types of hysterectomies are used: the vaginal hysterectomy and the minimal-invasive hysterectomy (MIH). The objective of present research was to compare the MIH and the total abdominal hysterectomy (TAH) in women presenting with benign uterine diseases. METHODS. A systemic review was made and a meta-analysis from the following databases: MEDLINE, EBSCO HOST AND The Cochrane Central Register of Controlled Trials. Only the controlled and randomized studies were selected. The data of all studies were combined and also the relative risk (RR) with a 95% CI was used with the Mantel-Haenszel method as an effect measure for dichotomy variables. For the analysis of continuing variables the mean difference was used. In all the comparisons performed the results were obtained with the fix effect and randomized forms. RESULTS. A total of 53 transoperative complications were registered in the MIH hysterectomy versus 17 in the TAH group (RR: 1,78; 95% CI: 1,04-3.05). Postoperative complications evolved in a similar way in both groups without significant differences from the statistical point of view. The blood losses, the hospital stay and the patient's reincorporation to usual and work activities were lesser in the laparoscopy group; however, the operative time is higher when it is compared with TAH (mean difference: 37,36; 95% CI: 34,36-39,93). CONCLUSIONS. Both techniques have advantages and disadvantages. The indication of MIH must to be individualized according to the clinical situation of each patient and these not to be performed in those centers without a properly trained surgical staff and with experience in advanced minimal invasive surgery. (author)

  19. Thermal stability of -amylase in aqueous cosolvent systems

    Indian Academy of Sciences (India)

    The activity and thermal stability of -amylase were studied in the presence of different concentrations of trehalose, sorbitol, sucrose and glycerol. ... Department of Protein Chemistry and Technology, Central Food Technological Research Institute (A constituent laboratory of Council of Scientific and Industrial Research), ...

  20. Thermal stability of α-amylase in aqueous cosolvent systems

    Indian Academy of Sciences (India)

    Prakash

    Department of Protein Chemistry and Technology, Central Food Technological Research Institute. (A constituent laboratory of Council of Scientific and Industrial Research), Mysore 570 020, India. *Corresponding author (Fax, +91-821-2516 308; Email, prakash@cftri.com). The activity and thermal stability of α-amylase were ...

  1. Visual Neuroscience: Unique Neural System for Flight Stabilization in Hummingbirds.

    Science.gov (United States)

    Ibbotson, M R

    2017-01-23

    The pretectal visual motion processing area in the hummingbird brain is unlike that in other birds: instead of emphasizing detection of horizontal movements, it codes for motion in all directions through 360°, possibly offering precise visual stability control during hovering. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Interferometric system for PM-level stability characterization

    NARCIS (Netherlands)

    Verlaan, A.L.; Ellis, J.D.; Voigt, D.; Spronck, J.W.; Munnig Schmidt, R.H.

    2010-01-01

    We present a double sided, single pass Michelson heterodyne interferometer for dimensional stability measurements. In preliminary measurements, the double deadpath configuration (no sample) showed better than ±1.5 nm (2/) over 13 hours. A 30 mm stainless gauge block was then measured with a

  3. Invasive endocervical adenocarcinoma: a new pattern-based classification system with important clinical significance.

    Science.gov (United States)

    Roma, Andres A; Diaz De Vivar, Andrea; Park, Kay J; Alvarado-Cabrero, Isabel; Rasty, Golnar; Chanona-Vilchis, Jose G; Mikami, Yoshiki; Hong, Sung R; Teramoto, Norihiro; Ali-Fehmi, Rouba; Rutgers, Joanne K L; Barbuto, Denise; Silva, Elvio G

    2015-05-01

    A new 3-tier pattern-based system to classify endocervical adenocarcinoma was recently presented. In short, pattern A tumors were characterized by well-demarcated glands frequently forming clusters or groups with relative lobular architecture. Pattern B tumors demonstrated localized destructive invasion defined as desmoplastic stroma surrounding glands with irregular and/or ill-defined borders or incomplete glands and associated tumor cells (individual or small clusters) within the stroma. Tumors with pattern C showed diffusely infiltrative glands with associated extensive desmoplastic response. In total, 352 cases (all FIGO stages) from 12 institutions were identified. Mean patient age was 45 years (range, 20 to 83 y). Forty-nine (13.9%) cases demonstrated lymph nodes (LNs) with metastatic endocervical carcinoma. Using this new system, 73 patients (20.7%) were identified with pattern A tumors (all stage I); none had LN metastases and/or recurrences. Ninety patients (25.6%) were identified with pattern B tumors (all stage I); only 4 (4.4%) had LN metastases; 1 had vaginal recurrence. The 189 (53.7%) remaining patients had pattern C tumors; 45 (23.8%) of them had LN metastases. This new classification system demonstrated 20.7% of patients (pattern A) with negative LNs, and patients with pattern A tumors can be spared of lymphadenectomy. Patients with pattern B tumors rarely presented with metastatic LNs, and sentinel LN examination could potentially identify these patients. Aggressive treatment is justified in patients with pattern C tumors.

  4. Stability analysis of a simplified model of supercritical water-cooled system

    International Nuclear Information System (INIS)

    Xue Aijun; Cheng Xu

    2009-01-01

    This paper presents the stability analysis of a simplified model of supercritical water-cooled system. Based on the perturbation linearization and Laplace transformation, transfer function of the simplified system model is established. A stability map is generated using both dimensionless parameters, i.e. sub-pseudo-critical number and trans-pseudo-critical number. An unstable region nearby the pseudo-critical point is determined. The effect of some important parameters on the stability behavior is investigated. It is found that the system is stabilized with a higher hydraulic resistance of the inlet, fluid inlet velocity. It is also found that a longer heating zone or a bigger acceleration of gravity leads to a larger stability margin of the system. (authors)

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

    Directory of Open Access Journals (Sweden)

    Kaur Ramandeep

    2016-01-01

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

  6. Stability of linear systems in second-order form based on structure preserving similarity transformations

    DEFF Research Database (Denmark)

    Stoustrup, Jakob; Pommer, Christian; Kliem, Wolfhard

    2015-01-01

    of the transformation parameters into a new system (I, B 1, C 1) with a symmetrizable matrix C 1. This procedure facilitates stability investigations. We also consider systems with a Hamiltonian spectrum which discloses marginal stability after a Jordan form preserving transformation.......This paper deals with two stability aspects of linear systems of the form Ix¨+Bx˙+Cx=0 given by the triple (I, B, C). A general transformation scheme is given for a structure and Jordan form preserving transformation of the triple. We investigate how a system can be transformed by suitable choices...

  7. Power system stabilizers based on distributed energy resources for damping of inter-area oscillations

    Directory of Open Access Journals (Sweden)

    Stefanov Predrag Č.

    2014-01-01

    Full Text Available This paper deals with inter-area power oscillations damping enhancement by distributed energy resources contained in typical micro grid. Main idea behind this work is to use distributed generation and distributed storage, such as battery energy storage to mimic conventional power system stabilizer, but with regulating active power output, rather than reactive power, as in standard power system stabilizer realization. The analysis of the small signal stability is established for four-machine, two-area system, with inverter based micro grids in each area. Dynamic simulation results are included in this work and they show that proposed controller provides additional damping effect to this test system.

  8. Stability Analysis for Fractional-Order Linear Singular Delay Differential Systems

    Directory of Open Access Journals (Sweden)

    Hai Zhang

    2014-01-01

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

  9. Evaluation of the tear film stability after laser in situ keratomileusis using the tear film stability analysis system.

    Science.gov (United States)

    Goto, Tomoko; Zheng, Xiaodong; Klyce, Stephen D; Kataoka, Hisashi; Uno, Toshihiko; Yamaguchi, Masahiko; Karon, Mike; Hirano, Sumie; Okamoto, Shigeki; Ohashi, Yuichi

    2004-01-01

    To evaluate the tear film stability of patients before and after laser in situ keratomileusis (LASIK) using the tear film stability analysis system (TSAS). Prospective observational case series. New videokeratography software for a topographic modeling system (TMS-2N) was developed that can automatically capture consecutive corneal surface images every second for 10 seconds. Thirty-four subjects (64 eyes) who underwent myopia LASIK were enrolled in this study. All subjects were examined with the new system before LASIK and at 1 week, 1 month, 3 months, and 6 months after the surgery. Corneal topographs were analyzed for tear breakup time (TMS breakup time) and breakup area (TMS breakup area). Based on pre-LASIK TSAS analysis, subjects were separated into normal and abnormal TSAS value groups. The criteria for the normal group were either TMS breakup time more than 5 seconds or TMS breakup area less than 0.2. The percentage of the occurrence of superficial punctuate keratitis was compared between the two groups with regard to subject's dry eye signs and symptoms. Tear film stability decreased significantly during the early period after LASIK, as indexed by decreased TMS breakup time and increased TMS breakup area. Tear film instability resolved at 6 months after surgery. Before LASIK, 22 subjects (43 eyes) had normal TSAS evaluation and 12 subjects (21 eyes) were abnormal. After LASIK, among normal TSAS value eyes, 8 of 43 (18.6%) eyes developed superficial punctuate keratitis. In sharp contrast, 14 of 21 (66.7%) eyes in the abnormal group displayed superficial punctuate keratitis, correlating well with the patients' dry eye symptoms. The difference in the presence of superficial punctuate keratitis after LASIK between normal and abnormal TSAS value groups was statistically significant (P <.001). Subjects with abnormal TSAS evaluation also displayed resistance to dry eye treatment and had extended period of recovery. Tear film stability analysis can be a useful

  10. Construction of a multiple fluorescence labeling system for use in co-invasion studies of Listeria monocytogenes

    DEFF Research Database (Denmark)

    Andersen, Jens Bo; Roldgaard, Bent; Lindner, A. B.

    2006-01-01

    strains at the single cell level by use of fluorescence microscopy. More than 90% of the L. monocytogenes host cells maintained the fluorescence tags for 40 generations. The fluorescence tags did not alter the invasive capacity of the L. monocytogenes cells in a traditional Caco-2 cell invasion assay......, and visual discrimination between invaded bacteria carrying different fluorescent labels inside the cells was possible. Conclusion The constructed fluorescent marker system is stable, easy to use, does not affect the virulence of L. monocytogenes in Caco-2 cell assays, and allows discrimination between...

  11. Coordination of Series and Shunt Flexible AC Transmission System Devices Based Voltage Source Converter for Improving Power System Stability

    OpenAIRE

    Prechanon Kumkratug

    2011-01-01

    Abstract: Problem statement: Static Synchronous Compensator (STATCOM) and Static Synchronous Series Compensator (SSSC) have been individually applied to improve stability of power system. Approach: This study presents the coordination of a STATCOM and SSSC 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 oscill...

  12. The PGI enzyme system and fitness response to temperature as a measure of environmental tolerance in an invasive species

    Directory of Open Access Journals (Sweden)

    Marie-Caroline Lefort

    2014-11-01

    Full Text Available In the field of invasion ecology, the determination of a species’ environmental tolerance, is a key parameter in the prediction of its potential distribution, particularly in the context of global warming. In poikilothermic species such as insects, temperature is often considered the most important abiotic factor that affects numerous life-history and fitness traits through its effect on metabolic rate. Therefore the response of an insect to challenging temperatures may provide key information as to its climatic and therefore spatial distribution. Variation in the phosphoglucose-6-isomerase (PGI metabolic enzyme-system has been proposed in some insects to underlie their relative fitness, and is recognised as a key enzyme in their thermal adaptation. However, in this context it has not been considered as a potential mechanism contributing to a species invasive cability. The present study aimed to compare the thermal tolerance of an invasive scarabaeid beetle, Costelytra zealandica (White with that of the closely related, and in part sympatrically occurring, congeneric non-invasive species C. brunneum (Broun, and to consider whether any correlation with particular PGI genotypes was apparent. Third instar larvae of each species were exposed to one of three different temperatures (10, 15 and 20 °C over six weeks and their fitness (survival and growth rate measured and PGI phenotyping performed via cellulose acetate electrophoresis. No consistent relationship between PGI genotypes and fitness was detected, suggesting that PGI may not be contributing to the invasion success and pest status of C. zealandica.

  13. High-spatial-resolution localization algorithm based on cascade deconvolution in a distributed Sagnac interferometer invasion monitoring system.

    Science.gov (United States)

    Pi, Shaohua; Wang, Bingjie; Zhao, Jiang; Sun, Qi

    2016-10-10

    In the Sagnac fiber optic interferometer system, the phase difference signal can be illustrated as a convolution of the waveform of the invasion with its occurring-position-associated transfer function h(t); deconvolution is introduced to improve the spatial resolution of the localization. In general, to get a 26 m spatial resolution at a sampling rate of 4×106  s-1, the algorithm should mainly go through three steps after the preprocessing operations. First, the decimated phase difference signal is transformed from the time domain into the real cepstrum domain, where a probable region of invasion distance can be ascertained. Second, a narrower region of invasion distance is acquired by coarsely assuming and sweeping a transfer function h(t) within the probable region and examining where the restored invasion waveform x(t) gets its minimum standard deviation. Third, fine sweeping the narrow region point by point with the same criteria is used to get the final localization. Also, the original waveform of invasion can be restored for the first time as a by-product, which provides more accurate and pure characteristics for further processing, such as subsequent pattern recognition.

  14. Stability improvement of a wavefront correction system for robust image acquisition

    Science.gov (United States)

    Park, Seung-Kyu; Baik, Sung-Hoon; Park, Nak-Gyu; Lee, Soo Man; Kim, Hyun Tae; Yoo, Jae Eun; Choi, Young Soo

    2014-07-01

    Stabilization techniques for a wavefront correction system using a Shack-Hartmann wavefront sensor and a membrane deformable mirror (DM) for robust image acquisition were investigated in this research. Though stability of a closed-loop wavefront correction system is essential in practical fields, stability is decreased when the system spends voltage resources to correct non-meaningful residual distortions. In this research, adaptive limit control techniques were devised to ensure the long-term stability of a wavefront correction system. An adaptive deformation technique for the outer non-active actuators of a membrane deformable mirror was adopted to improve the correction efficiency of the wavefront correction system. The experimental results corrected for wavefront distortions by using a configured wavefront correction system were described in this research.

  15. Power System Stabilizer Design Based on a Particle Swarm Optimization Multiobjective Function Implemented Under Graphical Interface

    Directory of Open Access Journals (Sweden)

    Ghouraf Djamel Eddine

    2016-05-01

    Full Text Available Power system stability considered a necessary condition for normal functioning of an electrical network. The role of regulation and control systems is to ensure that stability by determining the essential elements that influence it. This paper proposes a Particle Swarm Optimization (PSO based multiobjective function to tuning optimal parameters of Power System Stabilizer (PSS; this later is used as auxiliary to generator excitation system in order to damp electro mechanicals oscillations of the rotor and consequently improve Power system stability. The computer simulation results obtained by developed graphical user interface (GUI have proved the efficiency of PSS optimized by a Particle Swarm Optimization, in comparison with a conventional PSS, showing stable   system   responses   almost   insensitive   to   large parameter variations.Our present study was performed using a GUI realized under MATLAB in our work.

  16. Stabilization of the RF system at the SPring-8 linac

    CERN Document Server

    Asaka, T; Hori, T; Kobayashi, T; Mizuno, A; Sakaki, H; Suzuki, S; Taniuchi, T; Yanagida, K; Yokomizo, H; Yoshikawa, H

    2002-01-01

    Beam energy variation of the SPring-8 linac was 1% or more at the start of beam commissioning. Depending on fluctuation, beam transmission efficiency from the linac to the booster synchrotron was significantly affected, and beam intensity in the booster synchrotron changed 20-30%. This caused delay of optimization of the various parameters in the booster synchrotron. More problematic, the beam intensities stored in each RF (radio frequency) bucket of the storage ring at SPring-8 were all different from each other. The users utilizing synchrotron radiation requested that the beam intensity in each RF bucket be as uniform as possible. It was thus a pressing necessity to stabilize the beam energy in the linac. Investigation of the cause has clarified that the various apparatuses installed in the linac periodically changed depending on circumstances and utilities such as the air conditioner, cooling water and electric power. After various improvements, beam energy stability in the linac of <0.06% rms was attai...

  17. 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.

  18. A Laser Stabilization System for Rydberg Atom Physics

    Science.gov (United States)

    2015-09-06

    that is generated in a multi-pass frequency doubling cavity. In addition, the master laser wavelengths of 1020 nm and 960 nm lie in the near infra - red ...U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 laser stabilization, precision measurement REPORT DOCUMENTATION...Field Measurements Using Cs Rydberg Atoms in Vapor Cells,” H. Fan, S. Kumar and J.P. Shaffer, DAMOP, Columbus, OH (2015). “Interacting Rydberg Atoms

  19. A Wide-Band Electromagnetic Impedance Profiling System forNon-Invasive Subsurface Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Hung-Wen; Lee, Ki Ha; Becker, Alex

    2004-12-17

    A non-invasive, wide-band electromagnetic (EM) impedance difference system for shallow subsurface electrical structure characterization in environmental and engineering problems has been developed at the Lawrence Berkeley National Laboratory (LBNL). Electrical parameters of interest are electrical conductivity and dielectric permittivity that are deduced from the impedance difference data. The prototype system includes a magnetic loop transmitter, which operates between 0.1 MHz and 100 MHz, an electrical dipole antenna for observing the electric field, and a loop antenna for measuring the magnetic field.All antennas are mounted on a cart made of non-metallic material for easy movement of the whole array for profiling. Surface EM impedance difference is obtained by taking the difference of the ratios of the electric fields to the magnetic fields at selected frequencies at two different levels. Numerical simulations will be presented to verify this new approach. A set of the impedance difference data acquired at the University of California's Richmond Field Station compares reasonably well with simulation results based on a model obtained with the resistivity method and in situ TDR (time domain reflectometry)measurements.

  20. Stabilization and regulation of nonlinear systems a robust and adaptive approach

    CERN Document Server

    Chen, Zhiyong

    2015-01-01

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

  1. Control and stabilization system of extensive air showers Cherenkov detector parameters

    International Nuclear Information System (INIS)

    Bryanskij, S.V.; Basil'chenko, Yu.V.; Dudkin, G.N.; Egorov, V.Yu.; Zhavoronkov, N.A.; Padalko, V.N.

    1995-01-01

    Hardware and functional capabilities of control and stabilization system for parameters of photometric channels of extensive air showers Cherenkov detectors are described. The results of the system operation under severe climatic conditions are presented. The system is shown to ensure permanent stability of parameters of amplitude-measurement channels within ∼2% limits and measurement accuracy of time intervals equal to ∼0.2 ns. 6 refs.; 8 figs

  2. Mittag-Leffler Stability Theorem for Fractional Nonlinear Systems with Delay

    Directory of Open Access Journals (Sweden)

    S. J. Sadati

    2010-01-01

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

  3. Data Fusion Modeling for an RT3102 and Dewetron System Application in Hybrid Vehicle Stability Testing

    OpenAIRE

    Zhibin Miao; Hongtian Zhang

    2015-01-01

    More and more hybrid electric vehicles are driven since they offer such advantages as energy savings and better active safety performance. Hybrid vehicles have two or more power driving systems and frequently switch working condition, so controlling stability is very important. In this work, a two-stage Kalman algorithm method is used to fuse data in hybrid vehicle stability testing. First, the RT3102 navigation system and Dewetron system are introduced. Second, a modeling of data fusion is p...

  4. A comparative study of voltage stability indices in a power system

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, A.K. [I.I.T., Kharagpur (India). Dept. of Electrical Engineering; Hazarika, D. [Assam Engineering College (India)

    2000-11-01

    The paper compares the effectiveness of voltage stability indices in providing information about the proximity of voltage instability of a power system. Three simple voltage stability indices are proposed and their effectiveness is compared with some of the recently proposed indices. The comparison is carried out over a wide range of system operating conditions by changing the load power factor and feeder X/R ratios. Test results for the IEEE 57 bus and IEEE 118 bus system are presented. (author)

  5. ANALYSIS OF PERTURBED MOTION STABILITY OF WHEELER VEHICLES BRAKES CONTROL SYSTEM

    Directory of Open Access Journals (Sweden)

    V. Verbytskiyi

    2011-01-01

    Full Text Available The analysis of the perturbed motion stability of the brake automatic control system on the basis of Lyapunov’s second method is carried out. Using transformations of Lurie there has been ob-tained the canonical form of the system of equations of automatic control. It allowed determining the necessary and sufficient conditions of the asymptotic stability of the system irrespective of its initial condition and a definite choice of the admissible characteristic of the regulator.

  6. Some stability and boundedness criteria for a class of Volterra integro-differential systems

    Directory of Open Access Journals (Sweden)

    Jito Vanualailai

    2002-01-01

    Full Text Available Using Lyapunov and Lyapunov-like functionals, we study the stability and boundedness of the solutions of a system of Volterra integrodifferential equations. Our results, also extending some of the more well-known criteria, give new sufficient conditions for stability of the zero solution of the nonperturbed system, and prove that the same conditions for the perturbed system yield boundedness when the perturbation is $L^2$.

  7. Stability bound analysis of singularly perturbed systems with time-delay

    Directory of Open Access Journals (Sweden)

    Sun Fengqi

    2013-01-01

    Full Text Available This paper considers the stability bound problem of singularly perturbed systems with time-delay. Some stability criteria are derived by constructing appropriate Lyapunov-Krasovskii functionals. The proposed criteria are less conservative than the existing ones. Two numerical examples are given to illustrate the advantages and effectiveness of the proposed methods.

  8. pth Moment stability of impulsive stochastic delay differential systems with Markovian switching

    Science.gov (United States)

    Wu, Xiaotai; Zhang, Wenbing; Tang, Yang

    2013-07-01

    This paper is concerned with the pth moment stability of impulsive stochastic delay differential systems with Markovian switching. By using the Razumikhin-type method, some stability criteria are obtained, which can loosen the constraints of the existing results and thus reduce the conservativeness. Two examples are presented to demonstrate the usefulness of the proposed results.

  9. Results on stabilization of nonlinear systems under finite data-rate constraints

    NARCIS (Netherlands)

    Persis, Claudio De

    2004-01-01

    We discuss in this paper a result concerning the stabilization problem of nonlinear systems under data-rate constraints using output feedback. To put the result in a broader context, we shall first review a number of recent contributions on the stabilization problem under data-rate constraints when

  10. Parasitoid aggregation and the stabilization of a salt marsh host-parasitoid system

    Science.gov (United States)

    John D. Reeve; James T. Cronin; Donald R. Strong

    1994-01-01

    We examine a salt marsh host-parasitoid system, consisting of the planthopper Prokelisia marginata and its egg parasitoid Anagrus delicatus, for evidence of stabilizing parasitoid behavior. We first determine if there is sufficient parasitoid aggregation to potentially stabilize the Prokelisia-Anagrus interactions, using methods that infer parasitoid behavior from the...

  11. Regional modeling approach for analyzing harmonic stability in radial power electronics based power system

    DEFF Research Database (Denmark)

    Yoon, Changwoo; Bai, Haofeng; Wang, Xiongfei

    2015-01-01

    -function creates an ambiguity of knowing the reason of instability and also there is no fixed way of choosing the sequence of the analysis. This paper suggests a method to perform a regional stability analysis in the distribution power system. The main idea is started from the simplest stability analysis entity...

  12. Students' Understanding of Equilibrium and Stability: The Case of Dynamic Systems

    Science.gov (United States)

    Canu, Michaël; de Hosson, Cécile; Duque, Mauricio

    2016-01-01

    Engineering students in control courses have been observed to lack an understanding of equilibrium and stability, both of which are crucial concepts in this discipline. The introduction of these concepts is generally based on the study of classical examples from Newtonian mechanics supplemented with a control system. Equilibrium and stability are…

  13. Investigation of external and internal shock in the stability of Indonesia’s financial system

    Directory of Open Access Journals (Sweden)

    Maulina Vinus

    2017-07-01

    Full Text Available The objective of this research is to develop a financial system stability index and analyze the internal and external factors that we expect to affect the stability of the Indonesian financial system. We measured the single model of financial system stability index (FSSI from year 2004M03 to2014M09 in Indonesia, and compiled a single quantitative measure based on aggregate internal factors and external factors to capture and predict the shocks of the financial system stability. Stability parameters were composed of composite indicators on different bases. In addition, we developed a comprehensive index component associated with the relevant market conditions, including banking soundness index, financial vulnerability index, and regional economic climate index. Results stated that US economic growth and economic growth of ASEAN countries positively affected financial stability. In addition, current account, exchange rate, inflation, interest rate were shown to negatively affect financial stability. The results of this study imply that internal factors have a strong influence on the financial stability. Therefore, the central bank should give a fast and correct response to the changes of external and internal financial environment, especially for internal factors through monetary policy.

  14. Stabilized high-power laser system for the gravitational wave detector advanced LIGO.

    Science.gov (United States)

    Kwee, P; Bogan, C; Danzmann, K; Frede, M; Kim, H; King, P; Pöld, J; Puncken, O; Savage, R L; Seifert, F; Wessels, P; Winkelmann, L; Willke, B

    2012-05-07

    An ultra-stable, high-power cw Nd:YAG laser system, developed for the ground-based gravitational wave detector Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory), was comprehensively characterized. Laser power, frequency, beam pointing and beam quality were simultaneously stabilized using different active and passive schemes. The output beam, the performance of the stabilization, and the cross-coupling between different stabilization feedback control loops were characterized and found to fulfill most design requirements. The employed stabilization schemes and the achieved performance are of relevance to many high-precision optical experiments.

  15. Stability of large DC power systems using switching converters, with application to the international space station

    Science.gov (United States)

    Manners, B.; Gholdston, E. W.; Karimi, K.; Lee, F. C.; Rajagopalan, J.; Panov, Y.

    1996-01-01

    As space direct current (dc) power systems continue to grow in size, switching power converters are playing an ever larger role in power conditioning and control. When designing a large dc system using power converters of this type, special attention must be placed on the electrical stability of the system and of the individual loads on the system. In the design of the electric power system (EPS) of the International Space Station (ISS), the National Aeronautics and Space Administration (NASA) and its contractor team led by Boeing Defense & Space Group has placed a great deal of emphasis on designing for system and load stability. To achieve this goal, the team has expended considerable effort deriving a dear concept on defining system stability in both a general sense and specifically with respect to the space station. The ISS power system presents numerous challenges with respect to system stability, such as high power, complex sources and undefined loads. To complicate these issues, source and load components have been designed in parallel by three major subcontractors (Boeing, Rocketdyne, and McDonnell Douglas) with interfaces to both sources and loads being designed in different countries (Russia, Japan, Canada, Europe, etc.). These issues, coupled with the program goal of limiting costs, have proven a significant challenge to the program. As a result, the program has derived an impedance specification approach for system stability. This approach is based on the significant relationship between source and load impedances and the effect of this relationship on system stability. This approach is limited in its applicability by the theoretical and practical limits on component designs as presented by each system segment. As a result, the overall approach to system stability implemented by the ISS program consists of specific hardware requirements coupled with extensive system analysis and hardware testing. Following this approach, the ISS program plans to begin

  16. Wind Power Impact to Transient and Voltage Stability of the Power System in Eastern Denmark

    DEFF Research Database (Denmark)

    Rasmussen, Joana; Jørgensen, Preben; Palsson, Magni Thor

    2005-01-01

    Voltage stability, transient stability and reactive power compensation are extremely important issues for largescale integration of wind power in areas distant from the main transmission system in Eastern Denmark. This paper describes the application of a dynamic wind farm model in simulation...... studies for assessments of a large wind power penetration. The simulation results reveal problems with voltage stability due to the characteristic of wind turbine generation as well as the inability of the power system to meet the reactive power demand. Furthermore, the established model is applied...... to analyse challenges in system protection as means to reduce the risk of widespread blackouts....

  17. ℋ∞ constant gain state feedback stabilization of stochastic hybrid systems with Wiener process

    Directory of Open Access Journals (Sweden)

    E. K. Boukas

    2004-01-01

    Full Text Available This paper considers the stabilization problem of the class of continuous-time linear stochastic hybrid systems with Wiener process. The ℋ∞ state feedback stabilization problem is treated. A state feedback controller with constant gain that does not require access to the system mode is designed. LMI-based conditions are developed to design the state feedback controller with constant gain that stochastically stabilizes the studied class of systems and, at the same time, achieve the disturbance rejection of a desired level. The minimum disturbance rejection is also determined. Numerical examples are given to show the usefulness of the proposed results.

  18. Hurwitz stability analysis of fractional order LTI systems according to principal characteristic equations.

    Science.gov (United States)

    Alagoz, Baris Baykant

    2017-09-01

    With power mapping (conformal mapping), stability analyses of fractional order linear time invariant (LTI) systems are carried out by consideration of the root locus of expanded degree integer order polynomials in the principal Riemann sheet. However, it is essential to show the left half plane (LHP) stability analysis of fractional order characteristic polynomials in the s plane in order to close the gap emerging in stability analyses of fractional order and integer order systems. In this study, after briefly discussing the relation between the characteristic root orientations and the system stability, the author presents a methodology to establish principal characteristic polynomials to perform the LHP stability analysis of fractional order systems. The principal characteristic polynomials are formed by factorizing principal characteristic roots. Then, the LHP stability analysis of fractional order systems can be carried out by using the root equivalency of fractional order principal characteristic polynomials. Illustrative examples are presented to explain how to find equivalent roots of fractional order principal characteristic polynomials in order to carry out the LHP stability analyses of fractional order nominal and interval systems. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  19. A Panoramic Wireless Endoscope System Design for the Application of Minimally Invasive Surgery

    Directory of Open Access Journals (Sweden)

    Chun-Hsiang Peng

    2014-05-01

    Full Text Available Minimally Invasive Surgery (MIS is the current trend in surgery. Compared to traditional surgery, MIS can substantially decrease recovery time and expenses needed by patients after surgeries, reduce pain during surgical procedures, and is highly regarded by physicians and patients. An endoscope is widely used in the diagnosis and treatments of various medical disciplines, such as hysteroscopy, laparoscopy, and colonoscopy, and have been adopted by many branches of medicine. However, the limited image field of MIS is often the most difficult obstacles faced by surgeons and medical students, especially to less experienced physicians and difficult surgical procedures; the limited field of view of endoscopic imaging does not provide a whole picture of the surgery area, making the procedures difficult and full of uncertainty. In light of this problem, we proposed a "Panoramic Wireless Endoscope System design", hoping to provide physicians with a wide field of view of the endoscopic image. We combine images captured from two parallel-mounted endoscope lenses into a single, wide-angle image, giving physicians a wider field of view and easier access to the surgical area. In addition, we developed a wireless transmission system so the image can be transmitted to various display platforms, eliminating the needs for excessive cabling on surgical tools and enable physicians to better operate on the patient. Finally, our system allows surgical assistants a better view of the operation process, and enables other physicians and nurses to remotely observe the process. Our experiment results have shown that we can increase the image to 152% of its original size. We used the PandaBoard ES platform with an ARM9 processor and 1G of onboard RAM, and continuously implementing animal trials to verify the reliability of our system.

  20. Dynamics of a distributed drill string system: Characteristic parameters and stability maps

    Science.gov (United States)

    Aarsnes, Ulf Jakob F.; van de Wouw, Nathan

    2018-03-01

    This paper involves the dynamic (stability) analysis of distributed drill-string systems. A minimal set of parameters characterizing the linearized, axial-torsional dynamics of a distributed drill string coupled through the bit-rock interaction is derived. This is found to correspond to five parameters for a simple drill string and eight parameters for a two-sectioned drill-string (e.g., corresponding to the pipe and collar sections of a drilling system). These dynamic characterizations are used to plot the inverse gain margin of the system, parametrized in the non-dimensional parameters, effectively creating a stability map covering the full range of realistic physical parameters. This analysis reveals a complex spectrum of dynamics not evident in stability analysis with lumped models, thus indicating the importance of analysis using distributed models. Moreover, it reveals trends concerning stability properties depending on key system parameters useful in the context of system and control design aiming at the mitigation of vibrations.

  1. Exponential Stability of Time-Switched Two-Subsystem Nonlinear Systems with Application to Intermittent Control

    Directory of Open Access Journals (Sweden)

    Huang Tingwen

    2009-01-01

    Full Text Available This paper studies the exponential stability of a class of periodically time-switched nonlinear systems. Three cases of such systems which are composed, respectively, of a pair of unstable subsystems, of both stable and unstable subsystems, and of a pair of stable systems, are considered. For the first case, the proposed result shows that there exists periodically switching rule guaranteeing the exponential stability of the whole system with (sufficient small switching period if there is a Hurwitz linear convex combination of two uncertain linear systems derived from two subsystems by certain linearization. For the second case, we present two general switching criteria by means of multiple and single Lyapunov function, respectively. We also investigate the stability issue of the third case, and the switching criteria of exponential stability are proposed. The present results for the second case are further applied to the periodically intermittent control. Several numerical examples are also given to show the effectiveness of theoretical results.

  2. Orbital Stability of Multi-Planet Systems: Behavior at High Masses

    Science.gov (United States)

    Morrison, Sarah J.; Kratter, Kaitlin M.

    2015-12-01

    We explore the relationships between planet separation, mass, and stability timescale in high mass multi-planet systems containing planet masses and multiplicities relevant for planetary systems detectable via direct imaging. Extrapolating empirically derived relationships between planet mass, separation, and stability timescale derived from lower mass planetary systems misestimate the stability timescales for higher mass planetary systems by more than an order of magnitude at close separations near the two body Hill stability limit. We also find that characterizing critical separations in terms of period ratio produces a linear relationship between log-timescale and separation with the same slope for planet-star mass ratios comparable to or exceeding Jupiter’s, but this slope steepens for lower mass planetary systems. We discuss possible mechanisms for instability that result in this behavior including perturbing adjacent planet pairs into an overlap regime between 1st and sometimes 2nd order mean motion resonances.

  3. A digital frequency stabilization system of external cavity diode laser based on LabVIEW FPGA

    Science.gov (United States)

    Liu, Zhuohuan; Hu, Zhaohui; Qi, Lu; Wang, Tao

    2015-10-01

    Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument's FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.

  4. Stability of limit cycles in autonomous nonlinear systems

    Czech Academy of Sciences Publication Activity Database

    Náprstek, Jiří; Fischer, Cyril

    2014-01-01

    Roč. 49, č. 8 (2014), s. 1929-1943 ISSN 0025-6455 R&D Projects: GA AV ČR(CZ) IAA200710902; GA ČR(CZ) GA103/09/0094; GA ČR(CZ) GC13-34405J Institutional support: RVO:68378297 Keywords : limit cycle * nonlinear oscillator * stability Subject RIV: JM - Building Engineering Impact factor: 1.949, year: 2014 http://link.springer.com/article/10.1007/s11012-014-9899-8

  5. L2-stability of the Vlasov-Maxwell-Boltzmann system near global Maxwellians

    International Nuclear Information System (INIS)

    Ha, Seung-Yeal; Xiao, Qinghua; Xiong, Linjie; Zhao, Huijiang

    2013-01-01

    We present a L 2 -stability theory of the Vlasov-Maxwell-Boltzmann system for the two-species collisional plasma. We show that in a perturbative regime of a global Maxwellian, the L 2 -distance between two strong solutions can be controlled by that between initial data in a Lipschitz manner. Our stability result extends earlier results [Ha, S.-Y. and Xiao, Q.-H., “A revisiting to the L 2 -stability theory of the Boltzmann equation near global Maxwellians,” (submitted) and Ha, S.-Y., Yang, X.-F., and Yun, S.-B., “L 2 stability theory of the Boltzmann equation near a global Maxwellian,” Arch. Ration. Mech. Anal. 197, 657–688 (2010)] on the L 2 -stability of the Boltzmann equation to the Boltzmann equation coupled with self-consistent external forces. As a direct application of our stability result, we show that classical solutions in Duan et al. [“Optimal large-time behavior of the Vlasov-Maxwell-Boltzmann system in the whole space,” Commun. Pure Appl. Math. 24, 1497–1546 (2011)] and Guo [“The Vlasov-Maxwell-Boltzmann system near Maxwellians,” Invent. Math. 153(3), 593–630 (2003)] satisfy a uniform L 2 -stability estimate. This is the first result on the L 2 -stability of the Boltzmann equation coupled with self-consistent field equations in three dimensions

  6. Minimally-Invasive Neural Interface for Distributed Wireless Electrocorticogram Recording Systems

    Science.gov (United States)

    Chang, Sun-Il

    2018-01-01

    This paper presents a minimally-invasive neural interface for distributed wireless electrocorticogram (ECoG) recording systems. The proposed interface equips all necessary components for ECoG recording, such as the high performance front-end integrated circuits, a fabricated flexible microelectrode array, and wireless communication inside a miniaturized custom-made platform. The multiple units of the interface systems can be deployed to cover a broad range of the target brain region and transmit signals via a built-in intra-skin communication (ISCOM) module. The core integrated circuit (IC) consists of 16-channel, low-power push-pull double-gated preamplifiers, in-channel successive approximation register analog-to-digital converters (SAR ADC) with a single-clocked bootstrapping switch and a time-delayed control unit, an ISCOM module for wireless data transfer through the skin instead of a power-hungry RF wireless transmitter, and a monolithic voltage/current reference generator to support the aforementioned analog and mixed-signal circuit blocks. The IC was fabricated using 250 nm CMOS processes in an area of 3.2 × 0.9 mm2 and achieved the low-power operation of 2.5 µW per channel. Input-referred noise was measured as 5.62 µVrms for 10 Hz to 10 kHz and ENOB of 7.21 at 31.25 kS/s. The implemented system successfully recorded multi-channel neural activities in vivo from a primate and demonstrated modular expandability using the ISCOM with power consumption of 160 µW. PMID:29342103

  7. Minimally-Invasive Neural Interface for Distributed Wireless Electrocorticogram Recording Systems.

    Science.gov (United States)

    Chang, Sun-Il; Park, Sung-Yun; Yoon, Euisik

    2018-01-17

    This paper presents a minimally-invasive neural interface for distributed wireless electrocorticogram (ECoG) recording systems. The proposed interface equips all necessary components for ECoG recording, such as the high performance front-end integrated circuits, a fabricated flexible microelectrode array, and wireless communication inside a miniaturized custom-made platform. The multiple units of the interface systems can be deployed to cover a broad range of the target brain region and transmit signals via a built-in intra-skin communication (ISCOM) module. The core integrated circuit (IC) consists of 16-channel, low-power push-pull double-gated preamplifiers, in-channel successive approximation register analog-to-digital converters (SAR ADC) with a single-clocked bootstrapping switch and a time-delayed control unit, an ISCOM module for wireless data transfer through the skin instead of a power-hungry RF wireless transmitter, and a monolithic voltage/current reference generator to support the aforementioned analog and mixed-signal circuit blocks. The IC was fabricated using 250 nm CMOS processes in an area of 3.2 × 0.9 mm² and achieved the low-power operation of 2.5 µW per channel. Input-referred noise was measured as 5.62 µV rms for 10 Hz to 10 kHz and ENOB of 7.21 at 31.25 kS/s. The implemented system successfully recorded multi-channel neural activities in vivo from a primate and demonstrated modular expandability using the ISCOM with power consumption of 160 µW.

  8. Local crop planting systems enhance insecticide-mediated displacement of two invasive leafminer fly.

    Directory of Open Access Journals (Sweden)

    Yulin Gao

    Full Text Available Liriomyza sativae and L. trifolii are highly invasive leafminer pests of vegetable crops that have invaded southern China in recent years. Liriomyza sativae was the first of these species to invade China, but it is now being displaced by L. trifolii. The rate and extent of this displacement vary across southern China. In Hainan, monocultures of highly valuable cowpea are planted and treated extensively with insecticides in attempts to control leafminer damage. In Guangdong, cowpea fields are interspersed with other less valuable crops, such as towel gourd (Luffa cylindrica, which receive significantly fewer insecticide applications than cowpea. To determine how differences in cropping systems influence the Liriomyza species composition, we conducted field trials in 2011 and 2012 in Guangdong where both species were present. We replicated conditions in Hainan by planting cowpea monocultures that were isolated from other agricultural fields, and we replicated conditions in Guangdong by planting cowpea in a mixed crop environment with towel gourd planted in neighboring plots. We then compared leafminer populations in cowpea treated with the insecticide avermectin and untreated cowpea. We also monitored leafminer populations in the untreated towel gourd. Untreated cowpea and towel gourd had comparatively low proportions of L. trifolii, which remained relatively stable over the course of each season. Avermectin applications led to increases in the proportions of L. trifolii, and after three weekly applications populations were >95% L. trifolii in both crop systems. However, the rate of change and persistence of L. trifolii in the mixed crop system were less than in the monocrop. These results indicate that L. trifolii is much less susceptible to avermectin than is L. sativae. Further, L. sativae was able to persist in the untreated towel gourd, which probably enabled it to recolonize treated cowpea.

  9. Minimally-Invasive Neural Interface for Distributed Wireless Electrocorticogram Recording Systems

    Directory of Open Access Journals (Sweden)

    Sun-Il Chang

    2018-01-01

    Full Text Available This paper presents a minimally-invasive neural interface for distributed wireless electrocorticogram (ECoG recording systems. The proposed interface equips all necessary components for ECoG recording, such as the high performance front-end integrated circuits, a fabricated flexible microelectrode array, and wireless communication inside a miniaturized custom-made platform. The multiple units of the interface systems can be deployed to cover a broad range of the target brain region and transmit signals via a built-in intra-skin communication (ISCOM module. The core integrated circuit (IC consists of 16-channel, low-power push-pull double-gated preamplifiers, in-channel successive approximation register analog-to-digital converters (SAR ADC with a single-clocked bootstrapping switch and a time-delayed control unit, an ISCOM module for wireless data transfer through the skin instead of a power-hungry RF wireless transmitter, and a monolithic voltage/current reference generator to support the aforementioned analog and mixed-signal circuit blocks. The IC was fabricated using 250 nm CMOS processes in an area of 3.2 × 0.9 mm2 and achieved the low-power operation of 2.5 µW per channel. Input-referred noise was measured as 5.62 µVrms for 10 Hz to 10 kHz and ENOB of 7.21 at 31.25 kS/s. The implemented system successfully recorded multi-channel neural activities in vivo from a primate and demonstrated modular expandability using the ISCOM with power consumption of 160 µW.

  10. 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...

  11. Linear Quantum Systems: Non-Classical States and Robust Stability

    Science.gov (United States)

    2016-06-29

    paper is to extend linear systems and signals theory to include single photon quantum signals . We provide detailed results describing how quantum...v) physical realizability results for finite level quantum systems. 15. SUBJECT TERMS Control Theory , Quantum Feedback, Quantum Algorithms 16...nominal linear models, and (v) physical realizability results for finite level quantum systems. Introduction: Classical linear systems theory

  12. MicroRNA-184 Modulates Human Central Nervous System Lymphoma Cells Growth and Invasion by Targeting iASPP.

    Science.gov (United States)

    Liang, Xiao-Gong; Meng, Wen-Tong; Hu, Lian-Jie; Li, Lin; Xing, Hongyun; Xie, Gan; Wang, An-Qiong; Jia, Yong-Qian

    2017-09-01

    Central nervous system lymphoma (CNSL) remains a diagnostical and therapeutical challenge. MiRNAs post-transcriptionally regulate expression of targeted mRNAs through binding to their 3' UTR to inhibit their translation or promote their degradation. Oncoprotein inhibitory member of the ASPP family (iASPP), a key inhibitor of tumor suppressor p53, has been reported to play oncogenic role in cancers. Our present study was aimed to determine whether the miR-184/iASPP axis is involved in the proliferation and invasion of CNSL. A reduced level of miR-184 was observed in CNSL tissues. Exogenous miR-184 inhibited cell survival and invasion, as well as the tumor volumes, while miR-184 inhibition could reverse this process. The RNA and protein levels of iASPP were significantly inhibited by miR-184, and the 3' UTR of iASPP was shown to be a target of miR-184. The expression of iASPP was up-regulated in CNSL tissues, compared to that of the normal brain tissues. The inhibition of iASPP by shRNA iASPP significantly repressed CNSL cells' proliferation and invasion, and reduced the volume of the tumor. Besides, iASPP overexpression could partly restore the suppressive effect of miR-184 on CNSL cell proliferation and invasive capability. We also revealed that miR-184/iASPP axis regulated the proliferation and invasion via PI3K/Akt signaling pathway, which presents a novel potential therapy for intervention of CNSL. Taken together, our findings revealed the detailed role of the miR-184/iASPP axis in CNSL and this axis might modulate the proliferation and invasion of CNSL via regulating the PI3K/Akt signaling pathway. J. Cell. Biochem. 118: 2645-2653, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  13. Treatment feasibility study of osteoporosis using minimal invasive laser needle system

    Science.gov (United States)

    Kang, Dongyeon; Ko, Chang-Yong; Ryu, Yeon-Hang; Park, Sunwook; Kim, Han-Sung; Jung, Byungjo

    2010-02-01

    Although the mechanism of laser stimulation effect in bone has not completely understood, laser stimulation is recommended in the treatment of osteoporosis due to positive treatment efficacy. In this study, a minimal invasive laser needle system (MILNS) was developed using a fine hollow needle in order to stimulate directly bone site by guiding an optical fiber. In order to evaluate the MILNS as a treatment method, in-vivo animal experiment study was performed using osteopenic mice. Twelve virginal ICR mice were employed and divided two groups: SHAM-group and LASERgroup. SHARM-group was stimulated by only fine hollow needle and LASER-group by fine hollow needle combined with laser stimulation. All mice were served in-vivo micro-CT images before and after treatment. Three dimensional (3D) structural parameters and vBMD (volume bone mineral density, g/cm3) in the trabecular bone were measured. After 2 weeks of stimulation, the vBMD, BV/TV, Tb.Th and Tb.N in LASER-group were significantly higher than those in SHAM-group (p<0.05). Potentially, this study suggested that the MILNS might prevent the bone loss and maintains the bone mineral density of osteopenic mice.

  14. Invasive species: Ocean ecosystem case studies for earth systems and environmental sciences

    Science.gov (United States)

    Schofield, Pam; Brown, Mary E.

    2016-01-01

    Marine species are increasingly transferred from areas where they are native to areas where they are not. Some nonnative species become invasive, causing undesirable impacts to environment, economy and/or human health. Nonnative marine species can be introduced through a variety of vectors, including shipping, trade, inland corridors (such as canals), and others. Effects of invasive marine species can be dramatic and irreversible. Case studies of four nonnative marine species are given (green crab, comb jelly, lionfish and Caulerpa algae).

  15. Methods of solving of the optimal stabilization problem for stationary smooth control systems. Part I

    Directory of Open Access Journals (Sweden)

    G. Kondrat'ev

    1999-10-01

    Full Text Available In this article some ideas of Hamilton mechanics and differential-algebraic Geometry are used to exact definition of the potential function (Bellman-Lyapunov function in the optimal stabilization problem of smooth finite-dimensional systems.

  16. 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.

  17. Stability Analysis of a Turbocharger Rotor System Supported on Floating Ring Bearings

    International Nuclear Information System (INIS)

    Zhang, H; Shi, Z Q; Zhen, D; Gu, F S; Ball, A D

    2012-01-01

    The stability of a turbocharger rotor is governed by the coupling of rotor dynamics and fluid dynamics because the high speed rotor system is supported on a pair of hydrodynamic floating ring bearings which comprise of inner and outer fluid films in series. In order to investigate the stability, this paper has developed a finite element model of the rotor system with consideration of such exciting forces as rotor imbalance, hydrodynamic fluid forces, lubricant feed pressure and dead weight. The dimensionless analytical expression of nonlinear oil film forces in floating ring bearings have been derived on the basis of short bearing theory. Based on numerical simulation, the effects of rotor imbalance, lubricant viscosity, lubricant feed pressure and bearing clearances on the stability of turbocharger rotor system have been studied. The disciplines of the stability of two films and dynamic performances of rotor system have been provided.

  18. Analysis and improvement of digital control stability for master-slave manipulator system

    International Nuclear Information System (INIS)

    Yoshida, Koichi; Yabuta, Tetsuro

    1992-01-01

    Some bilateral controls of master-slave system have been designed, which can realize high-fidelity telemanipulation as if the operator were manipulating the object directly. While usual robot systems are controlled by software-servo system using digital computer, little work has been published on design and analysis for digital control of these systems, which must consider time-delay of sensor signals and zero order hold effect of command signals on actuators. This paper presents a digital control analysis for single degree of freedom master-slave system including impedance models of both the human operator and the task object, which clarifies some index for the stability. The stability result shows a virtual master-slave system concepts, which improve the digital control stability. We first analyze a dynamic control method of master-slave system in discrete-time system for the stability problem, which can realize high-fidelity telemanipulation in the continuous-time. Secondly, using the results of the stability analysis, the robust control scheme for master-slave system is proposed, and the validity of this scheme is finally confirmed by the simulation. Consequently, it would be considered that any combination of master and slave modules with dynamic model of these manipulators is possible to construct the stable master-slave system. (author)

  19. Pyrophosphate scintigraphy and other non-invasive methods in the detection of cardiac involvement in some systemic connective tissue diseases

    Energy Technology Data Exchange (ETDEWEB)

    Duska, F.; Bradna, P.; Pospisil, M.; Kubicek, J.; Vizda, J.; Kafka, P.; Palicka, V.; Mazurova, Y.

    1987-02-01

    Thirteen patients with systemic lupus erythematosus, 8 patients with polymyositis, and 6 patients with spondylitis ankylopoetica (Bechterew's disease) underwent clinical cardiologic examination and scintigraphy of the myocardium (/sup 99m/Tc-pyrophosphate), ECG, echocardiography, polygraphy, and their blood pressure was taken. The aim of the study was to ascertain how such a combination of non-invasive examinations can help in recognizing a cardiac involvement. In systemic lupus erythematosus cases one or more positive findings were revealed in 9 patients (69%), in 4 patients all examinations were negative (31%). Four patients (50%) with polymyosits had positive findings. In patients with spondylitis ankylopoetica positive findings occurred in 2 cases (33%). The study has shown that a combination of non-invasive cardiologic methods increases the probability of detecting cardiac involvement in systemic connective tissue diseases.

  20. Small-angle stability analysis of a linear control system for a high power communication satellite

    Science.gov (United States)

    Omalley, T. A.

    1972-01-01

    A small angle stability analysis is presented for one particular configuration of a high power communication satellite having a linear control system. Both the central body and the solar array are treated as rigid bodies. The control system studied consists of three-axis control of the central body and one-axis control of the solar array rotation relative to the central body. The results yield preliminary indications of the relation of stability to satellite inertias and control gains.

  1. Analisis Penggunaan Power System Stabilizer (PSS) Dalam Perbaikan Stabilitas Dinamik Sistem Tenaga Listrik Multimesin

    OpenAIRE

    Rudi Masrul

    2009-01-01

    Tugas akhir ini menganalisis perbaikan stabilitas dinamis sistem tenaga listrik yang dilakukan dengan pemasangan Power System Stabilizer (PSS) yang diterapkan pada sistem eksitasi. Model sistem yang digunakan ialah sistem tenaga listrik multimesin, yang terdiri dari tiga generator atau pembangkit. Analisis dan simulasi ini diawali dengan pembuatan model matematik sistem tenaga listrik tanpa pemasangan Power System Stabilizer (PSS) ke dalam persamaan variabel keadaan, dan kemudian dibentuk ...

  2. Coordinated corrective control for transient stability enhancement in future Great Britain transmission system

    OpenAIRE

    Martinez Sanz, I; Chaudhuri, B; Strbac, G

    2016-01-01

    This paper demonstrates a corrective control strategy through fast actuators (TCSC FACTS and HVDC links, both LCC and VSC) in order to enhance the transient stability in the future Great Britain (GB) transmission network. A model predictive control (MPC) scheme that relies on system wide-area measurements is employed for coordinated control action through these power electronic devices with the aim of preserving the system stability without having to constrain pre-fault transfer levels. Case ...

  3. Comparison of implant stability measurement devices for bone-anchored hearing aid systems.

    Science.gov (United States)

    Westover, Lindsey; Faulkner, Gary; Hodgetts, William; Raboud, Don

    2018-01-01

    The success of implants for bone-anchored hearing aids (BAHA) relies on proper osseointegration at the bone-implant interface. Clinical evaluation of implant stability is important in prescribing loading, identifying the risk of failure, and monitoring the long-term health of the implant. The purpose of this in vitro study was to evaluate 2 measurement systems for BAHA implant stability: the most commonly used, Osstell implant stability quotient (ISQ), and a newly developed advance system for implant stability testing (ASIST). BAHA implants (Oticon Medical Ponto and Cochlear BAHA Connect systems) were installed in plastic materials with adhesive to simulate implants integrated in bone with varying levels of interface stiffness. Different lengths of BAHA abutments were used with each implant specimen, and stability measurements were obtained with both the Osstell ISQ and the ASIST systems. The measurement systems were evaluated in terms of sensitivity to differences in interface stiffness and the effect of abutment length on the stability measurement. Repeated measures ANOVA followed by post hoc t tests were used for the comparisons with a Bonferroni adjusted alpha value of .05/15 = .003 to control for potential type 1 errors. Changing the abutment length of a single implant installation had minimal effect on the ASIST stability coefficient, whereas large variations were observed in the Osstell implant stability quotient (ISQ). The Osstell showed a clear relationship of decreasing ISQ with increasing abutment length for both the Oticon Medical and the Cochlear implant systems. Both the ASIST and the Osstell were found to be sensitive to changes in interface properties, with the ASIST being more sensitive to these changes. The ASIST system is more sensitive to changes in interface properties and shows smaller variation because of changes in abutment length than the Osstell ISQ system. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry

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

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

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

  5. 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.

  6. Asymptotic Stability Results of Solutions of Neutral Delay Systems ...

    African Journals Online (AJOL)

    In this paper, a retarded delay system is transformed to a class of neutral delay system using the differentiability condition of the functional on the Banach space. The Leibnez-Newton formula and symmetric properties of some chosen matrices are utilized to formulate a Lyapunov functional of the transformed system, which ...

  7. Small disturbance voltage stability assessment of power systems by modal analysis and dynamic simulation

    International Nuclear Information System (INIS)

    Amjady, Nima; Ansari, Mohammad Reza

    2008-01-01

    The introduction of liberalized electricity markets in many countries has resulted in more highly stressed power systems. On the other hand, operating points of a power system are acceptable in the feasible region, which is surrounded by the borders of different stabilities. Power system instability is critical for all participants of the electricity market. Determination of different stability margins can result in the optimum utilization of power system with minimum risk. This paper focuses on the small disturbance voltage stability, which is an important subset of the power system global stability. This kind of voltage stability is usually evaluated by static analysis tools such as continuation power flow, while it essentially has dynamic nature. Besides, a combination of linear and nonlinear analysis tools is required to correctly analyze it. In this paper, a hybrid evaluation method composed of static, dynamic, linear, and nonlinear analysis tools is proposed for this purpose. Effect of load scenario, generation pattern, branch and generator contingency on the small disturbance voltage stability are evaluated by the hybrid method. The test results are given for New England and IEEE68 bus test systems. (author)

  8. Global Uniform Asymptotic Stability of a Class of Switched Linear Systems with an Infinite Number of Subsystems

    Directory of Open Access Journals (Sweden)

    L. F. Araghi

    2014-01-01

    Full Text Available Stability of switching systems with an infinite number of subsystems is important in some structure of systems, like fuzzy systems, neural networks, and so forth. Because of the relationship between stability of a set of matrices and switching systems, this paper first studies the stability of a set of matrices, then and the results are applied for stability of switching systems. Some new conditions for globally uniformly asymptotically stability (GUAS of discrete-time switched linear systems with an infinite number of subsystems are proposed. The paper considers some examples and simulation results.

  9. Theoretical and Methodological Aspects of Assessing the Financial Stability of the Banking System

    Directory of Open Access Journals (Sweden)

    Bezrodna Olena S.

    2017-06-01

    Full Text Available The aim of the article is to substantiate the directions and develop methodological tools for assessing the financial stability of the banking system. Taking into account the emergence character of the banking system as a complex systemic formation and the results of the analysis of scientific literature, arguments are given regarding the need to assess its financial stability using the following groups of indicators: intensity of the credit and financial interaction in the interbank market; functional load of the banking system in the context of ensuring macroeconomic development; structural changes and financial imbalances in the banking system and the activity of systemically important banks. There proposed a methodological approach to assessing the financial stability of the banking system, which implies quantitative integral assessment of its level and qualitative interpretation of the results using the methods of entropy and “golden section”, respectively. The application of the improved approach will allow identifying sources of risk distribution in the banking system and develop a set of effective regulatory measures in accordance with a certain level of its financial stability. Prospects for further research in this direction are to determine the dominants of ensuring the financial stability of the banking system as well as the threshold values of its assessment indicators, which serve to diagnose the crisis and can be used as a tool for the macro-prudential policy.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-20

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

  11. Stabilizing and destabilizing effects of damping in non-conservative systems: Some new results

    Science.gov (United States)

    Abdullatif, Mahmoud; Mukherjee, Ranjan; Hellum, Aren

    2018-01-01

    Previous work has amply demonstrated that non-conservative systems can be made unstable by the application of damping. Systems with two neutrally-stable damping levels, whereby the system initially gains stability but later loses stability as the level of damping is increased, have also been observed. The phenomenon of three damping-induced stability transitions has not been reported in the literature. Here we show that the addition of damping can cause non-conservative systems to become stable, then unstable, then stable again at the same value of the non-conservative forcing variable. This combination of stability transitions is found to exist for several example systems, including linkages with follower end forces and fluid-conveying pipes. Another interesting observation is that a given system can exhibit different forms of stability transitions in different regions of its parameter space. In a particular example, the neutral stability curves corresponding to two different modes are observed to intersect, such that the boundary separating the stable and unstable regions is piecewise continuous. This observation requires that the accepted definitions of "stabilizing" and "destabilizing" roles of damping be revised. All of these stability transition behaviors were found by applying the Routh-Hurwitz procedure, whereby the traditional procedure is first applied to the characteristic polynomial of the system, and then again to guarantee the existence of a second-order auxiliary polynomial in the Routh array. This procedure is developed in the context of examples, each of which concerns a classical apparatus who dynamics are more interesting than previously believed.

  12. RMP model based optimization of power system stabilizers in multi-machine power system.

    Science.gov (United States)

    Baek, Seung-Mook; Park, Jung-Wook

    2009-01-01

    This paper describes the nonlinear parameter optimization of power system stabilizer (PSS) by using the reduced multivariate polynomial (RMP) algorithm with the one-shot property. The RMP model estimates the second-order partial derivatives of the Hessian matrix after identifying the trajectory sensitivities, which can be computed from the hybrid system modeling with a set of differential-algebraic-impulsive-switched (DAIS) structure for a power system. Then, any nonlinear controller in the power system can be optimized by achieving a desired performance measure, mathematically represented by an objective function (OF). In this paper, the output saturation limiter of the PSS, which is used to improve low-frequency oscillation damping performance during a large disturbance, is optimally tuned exploiting the Hessian estimated by the RMP model. Its performances are evaluated with several case studies on both single-machine infinite bus (SMIB) and multi-machine power system (MMPS) by time-domain simulation. In particular, all nonlinear parameters of multiple PSSs on IEEE benchmark two-area four-machine power system are optimized to be robust against various disturbances by using the weighted sum of the OFs.

  13. Real time simulation application to monitor the stability limit of power system

    Science.gov (United States)

    Hartono, Kuo, Ming-Tse

    2017-06-01

    If the power system falls into an unsteady state, there will be voltage collapse in which the power system will be separated into small systems. Identifying the stability reserve in conformity with a certain practical operation condition is very important for the system management and operation. In fact, the global power system issue has caused serious outages due to voltage collapse such as in the United States-Canada in August 14, 2003; South London in August 28, 2003; southern Sweden and eastern Denmark in September 23, 2003; and Italy on September 28, 2003, and in Vietnam where power system problem led to power loss on 17 May 2005, 27 December 2006, 20 July 2007, and 10 September 2007. The analysis shows that the phenomenon is related to the loss of system stability. Thus, the operational system as well as the power system designs should be studied related to the issue of the system stability. To study the static stability of the power system, different approximate standards, called pragmatic criteria, were examined. Markovits has investigated the application of the standard of dP/dd to test the stability of the power button and dq/dU to check the voltage stability of the load button [1]. However, the storage stability when calculating standard dP/d d is usually much larger than the reserves when calculating standard dq/dU [1]. This paper presents a method to build a possible operation region in the power plane of load bus which works in comply with the stability limit to evaluate the stability reserve of the power system. This method is used to build a program to monitor the stability reserve of IEEE 39 Bus Power System in real time. To monitor the stability reserve of IEEE 39 nodes power system, articles based on the standard dq/dU was used to calculate the assessment. When using standard dq/dU to check for voltage stability load button, the amount of storage stability can be calculated by the following steps: first, transformed replacement scheme Masonry on

  14. Constructing a Laser Stabilization System for a Parity Non-Conservation Experiment with Francium

    Science.gov (United States)

    Dehart, A. C.; Gwinner, Gerald; Kossin, Michael; Behr, John; Gorelov, Alexandre; Kalita, Mukut; Pearson, Matthew; Aubin, Seth; Gomez Garcia, Eduardo; Orozco, Luis

    2017-04-01

    We are developing an experiment at TRIUMF to test the Standard model at low energies by measuring Parity Non-Conservation (PNC) effects in francium. Current efforts include preparations to study the 7s - 8s electric dipole (E1) forbidden transition in francium at 507 nm under the influence of an electric field. Fr has no stable isotope; therefore to frequency-stabilize our laser at 507 nm, we are developing a laser stabilization system by using the Pound-Drever-Hall technique with a Fabry-Perot cavity made of Ultra Low Expansion Glass (ULE) as our stable frequency reference. The system will stabilize a 1014 nm laser, which will be frequency doubled to 507 nm, before sending the light to our cold and trapped francium sample. We will report on our recent experiences with the laser stabilization system. Supported by NSERC, NRC/TRIUMF, DOE, NSF, CONACYT, Fulbright, and U. of Manitoba.

  15. Zinc metalloproteinase ZmpC suppresses experimental pneumococcal meningitis by inhibiting bacterial invasion of central nervous systems.

    Science.gov (United States)

    Yamaguchi, Masaya; Nakata, Masanobu; Sumioka, Ryuichi; Hirose, Yujiro; Wada, Satoshi; Akeda, Yukihiro; Sumitomo, Tomoko; Kawabata, Shigetada

    2017-11-17

    Streptococcus pneumoniae is a leading cause of bacterial meningitis. Here, we investigated whether pneumococcal paralogous zinc metalloproteases contribute to meningitis onset. Findings of codon-based phylogenetic analyses indicated 3 major clusters in the Zmp family; ZmpA, ZmpC, and ZmpB, with ZmpD as a subgroup. In vitro invasion assays of human brain microvascular endothelial cells (hBMECs) showed that deletion of the zmpC gene in S. pneumoniae strain TIGR4 significantly increased bacterial invasion into hBMECs, whereas deletion of either zmpA or zmpB had no effect. In a mouse meningitis model, the zmpC deletion mutant exhibited increased invasion of the brain and was associated with increased matrix metalloproteinase-9 in plasma and mortality as compared with the wild type. We concluded that ZmpC suppresses pneumococcal virulence by inhibiting bacterial invasion of the central nervous system. Furthermore, ZmpC illustrates the evolutional theory stating that gene duplication leads to acquisition of novel function to suppress excessive mortality.

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

    Directory of Open Access Journals (Sweden)

    Mnif Faïçal

    2016-12-01

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

  17. Harmonic Stability Analysis of Inverter-Fed Power Systems Using Component Connection Method

    DEFF Research Database (Denmark)

    Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede

    2016-01-01

    This paper presents a Component Connection Method (CCM)-based harmonic stability analysis for ac power-electronic-fed power systems. In the approach, the system is partitioned as individual components, including the controllers of DG units, LC filters, network impedances, and power loads...... is formulated. And the harmonic stability is assessed based on eigenvalue traces of the composite model. Simulations and experimental results are given to validate the effectiveness of the analysis method, which can be employed to assess the system harmonic stability for any combinations of system parameters....... They are first independently modeled and then assembled together based on component interconnection relationships, forming a composite system model featured with the sparse and diagonal state matrix, and thereby reducing the computational burdens. A modular modelling technique for inverter-fed power system...

  18. Hydrologic controls and anthropogenic drivers of the zebra mussel invasion of the Mississippi-Missouri river system

    Science.gov (United States)

    Mari, L.; Bertuzzo, E.; Casagrandi, R.; Gatto, M.; Levin, S. A.; Rodriguez-Iturbe, I.; Rinaldo, A.

    2011-03-01

    We propose a novel ecohydrological model for the invasion of inland waters by the zebra mussel Dreissena polymorpha and test it against field data gathered within the Mississippi-Missouri river system in North America. This biological invasion poses major ecological and economic threats, especially due to the huge population densities reached by local zebra mussel colonies and the species' unparalleled dispersal abilities within fluvial systems. We focus on a quantitative evaluation, attempted here for the first time, of the individual roles and the mutual interactions of drivers and controls of the Mississippi-Missouri invasion. To this end, we use a multilayer network model accounting explicitly for zebra mussel demographic dynamics, hydrologic transport, and dispersal due to anthropic activities. By testing our results against observations, we show that hydrologic transport alone is not sufficient to explain the spread of the species at the basin scale. We also quantify the role played by commercial navigation in promoting the initial, selective colonization of the river system, and show how recreational boating may have determined the capillary penetration of the species into the water system. The role of post-establishment dispersal mechanisms and the effectiveness of possible prevention measures are also discussed in the context of model sensitivity and robustness to reparametrization.

  19. Research on the Stability of Open Financial System

    Directory of Open Access Journals (Sweden)

    Haijun Yang

    2015-03-01

    Full Text Available We propose a new herd mechanism and embed it into an open financial market system, which allows traders to get in and out of the system based on some transition rates. Moreover, the novel mechanism can avoid the volatility disappearance when the population scale increases. There are three kinds of heterogeneous agents in the system: optimistic, pessimistic and fundamental. Interactions especially occur among three different groups of agents instead of two, which makes the artificial financial market more close to the real one. By the simulation results of this complex system, we can explain stylized facts like volatility clustering and find the key parameters of market bubbles and market collapses.

  20. 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