Sliwa, S. M.
1980-01-01
Direct constrained parameter optimization was used to optimally size a medium range transport for minimum direct operating cost. Several stability and control constraints were varied to study the sensitivity of the configuration to specifying the unaugmented flying qualities of transports designed to take maximum advantage of relaxed static stability augmentation systems. Additionally, a number of handling qualities related design constants were studied with respect to their impact on the design.
Effects of relaxed static longitudinal stability on a single-stage-to-orbit vehicle design
Freeman, D. C., Jr.; Wilhite, A. W.
1979-01-01
The effects of relaxing longitudinal stability requirements on single stage to orbit space vehicles is studied. A comparison of the mass and performance characteristics of two vehicles, one designed for positive levels of longitudinal stability and the other designed with relaxed stability requirements in a computer aided design process is presented. Both vehicles, required to meet the same mission characteristics are described. Wind tunnel tests, conducted over a Mach number range from 0.3 to 4.63 to verify estimated aerodynamic characteristics, are discussed.
Static tensioning promotes hamstring tendons force relaxation more reliably than cycling tensioning.
Piedade, Sérgio Rocha; Dal Fabbro, Inácio Maria; Mischan, Martha Maria; Piedade, Cezar; Maffulli, Nicola
2017-08-01
Graft elongation might be a major reason for increased anterior laxity after anterior cruciate ligament (ACL) reconstruction. This study analyzed the force relaxation values and their stabilization when single strands of the gracilis and semitendinosus tendons underwent cyclic and static tensioning at 2.5% strain level, and compared the efficiency of static and cyclic tensioning in promoting force relaxation. Eighteen gracilis tendons and 18 semitendinosus tendons from nine male cadavers (mean age: 22.44years) were subjected to 10 in vitro cyclic loads at 2.5% strain level, or to a static load at 2.5% strain level. During cyclic loading, the reduction in force values tended to stabilize after the sixth cyclic load, while, in the case of static loading, this stabilization occurred by the second minute. Comparing static and cyclic loading, the gracilis tendon had similar mechanical responses in both conditions, while the semitendinosus tendon showed greater force relaxation in static compared with cyclic loading. Considering that the semitendinosus tendon is the main component of the hamstring graft, its biomechanical response to loading should guide the tensioning protocol. Therefore, static tensioning seems more effective for promoting force relaxation of the semitendinosus tendon than cyclic tensioning. The gracilis tendon showed a similar mechanical response to either tensioning protocols. Copyright © 2017 Elsevier B.V. All rights reserved.
ENROLMENT MODEL STABILITY IN STATIC SIGNATURE VERIFICATION
Allgrove, C.; Fairhurst, M.C.
2004-01-01
The stability of enrolment models used in a static verification system is assessed, in order to provide an enhanced chracterisation of signatures through the validation of the enrolment process. A number of static features are used to illustrate the effect of the variation in enrolment model size on
Quasi-static relaxation of arbitrarily shaped sessile drops
Iliev, S; Nikolayev, Vadim
2016-01-01
We study a spontaneous relaxation dynamics of arbitrarily shaped liquid drops on solid surfaces in the partial wetting regime. It is assumed that the energy dissipated near the contact line is much larger than that in the bulk of the fluid. We have shown rigorously in the case of quasi-static relaxation using the standard mechanical description of dissipative system dynamics that the introduction of a dissipation term proportional to the contact line length leads to the well known local relation between the contact line velocity and the dynamic contact angle at every point of an arbitrary contact line shape. A numerical code is developed for 3D drops to study the dependence of the relaxation dynamics on the initial drop shape. The available asymptotic solutions are tested against the obtained numerical data. We show how the relaxation at a given point of the contact line is influenced by the dynamics of the whole drop which is a manifestation of the non-local
The longitudinal static stability of tailless aircraft
de Castro, Helena V.
2001-01-01
This paper describes the development of a simple theory of the longitudinal controls fixed static stability of tailless aeroplanes. The classical theory, as developed for the conventional aircraft, is modified to accommodate the particular features of the tailless aeroplanes. The theory was then applied to a particular blended-wing-body tailless civil transport aircraft, BWB-98. Cranfield University
Plate shell structures - statics and stability
Almegaard, Henrik
2008-01-01
This paper describes the basic structural system, statics and spatial stability of plate shells. The structural system can be considered as a single layer of planar elements, where each element only transfers in-plane (membrane) forces to its neighbouring elements. External out-of-plane loads...... are carried into the structure as in-plane forces by plate action in each element. These in-plane forces are then carried through the plate structure to the supports as in-plane forces by membrane action. The consequence is that the spatial stability of the structure can be simply analysed by considering...... the plate system as only subject to in-plane loads. The stability of such systems is based on the fact that each plane element is held fixed in space by three fixed support lines and that these support lines can be provided by three plane neighbour elements. This means that the spatial stability of a plate...
Matlab Stability and Control Toolbox: Trim and Static Stability Module
Crespo, Luis G.; Kenny, Sean P.
2006-01-01
This paper presents the technical background of the Trim and Static module of the Matlab Stability and Control Toolbox. This module performs a low-fidelity stability and control assessment of an aircraft model for a set of flight critical conditions. This is attained by determining if the control authority available for trim is sufficient and if the static stability characteristics are adequate. These conditions can be selected from a prescribed set or can be specified to meet particular requirements. The prescribed set of conditions includes horizontal flight, take-off rotation, landing flare, steady roll, steady turn and pull-up/ push-over flight, for which several operating conditions can be specified. A mathematical model was developed allowing for six-dimensional trim, adjustable inertial properties, asymmetric vehicle layouts, arbitrary number of engines, multi-axial thrust vectoring, engine(s)-out conditions, crosswind and gyroscopic effects.
MATLAB Stability and Control Toolbox Trim and Static Stability Module
Kenny, Sean P.; Crespo, Luis
2012-01-01
MATLAB Stability and Control Toolbox (MASCOT) utilizes geometric, aerodynamic, and inertial inputs to calculate air vehicle stability in a variety of critical flight conditions. The code is based on fundamental, non-linear equations of motion and is able to translate results into a qualitative, graphical scale useful to the non-expert. MASCOT was created to provide the conceptual aircraft designer accurate predictions of air vehicle stability and control characteristics. The code takes as input mass property data in the form of an inertia tensor, aerodynamic loading data, and propulsion (i.e. thrust) loading data. Using fundamental nonlinear equations of motion, MASCOT then calculates vehicle trim and static stability data for the desired flight condition(s). Available flight conditions include six horizontal and six landing rotation conditions with varying options for engine out, crosswind, and sideslip, plus three take-off rotation conditions. Results are displayed through a unique graphical interface developed to provide the non-stability and control expert conceptual design engineer a qualitative scale indicating whether the vehicle has acceptable, marginal, or unacceptable static stability characteristics. If desired, the user can also examine the detailed, quantitative results.
Effect of modified hold-relax stretching and static stretching on hamstring muscle flexibility.
Ahmed, Hashim; Iqbal, Amir; Anwer, Shahnawaz; Alghadir, Ahmad
2015-02-01
[Purpose] The aim of present study was to compare the effectiveness of modified hold-relax stretching and static stretching in improving the hamstring muscle flexibility. [Subjects and Methods] Forty-five male subjects with hamstring tightness were included in this study. The subjects were randomly placed into three groups: the modified hold-relax stretching, static stretching and control groups. The modified hold-relax stretching group performed 7 seconds of isometric contraction and then relaxed for 5 seconds, and this was repeated five times daily for five consecutive days. The static stretching group received 10 minutes of static stretching with the help of a pulley and weight system for five consecutive days. The control group received only moist heat for 20 minutes for five consecutive days. A baseline reading of passive knee extension (PKE) was taken prior to the intervention; rest measurements were taken immediate post intervention on day 1, day 3, day 5, and after a 1 week follow-up, i.e., at the 12th day. [Results] On comparing the baseline readings of passive knee extension (PKE), there was no difference noted between the three groups. On comparing the posttest readings on day 5 between the 3 groups, a significant difference was noted. However, post hoc analysis revealed an insignificant difference between the modified hold-relax stretching and static stretching groups. There was a significant difference between the static stretching and control groups and between the modified hold-relax stretching and control groups. [Conclusion] The results of this study indicate that both the modified hold-relax stretching technique and static stretching are equally effective, as there was no significant difference in improving the hamstring muscle flexibility between the two groups.
New Sufficient LMI Conditions for Static Output Stabilization
Adegas, Fabiano Daher
2014-01-01
This paper presents new linear matrix inequality conditions to the static output feedback stabilization problem. Although the conditions are only sufficient, numerical experiments show excellent success rates in finding a stabilizing controller.......This paper presents new linear matrix inequality conditions to the static output feedback stabilization problem. Although the conditions are only sufficient, numerical experiments show excellent success rates in finding a stabilizing controller....
Micromechanical Fast Quasi-Static Detection of α and β Relaxations with Nanograms of Polymer
Bose, Sanjukta; Schmid, Silvan; Larsen, Tom;
2015-01-01
Micromechanical string resonators are used as a highly sensitive tool for the detection of glass transition (Tg or α relaxation) and sub-Tg (β relaxation) temperatures of polystyrene (PS) and poly (methyl methacrylate) (PMMA). The characterization technique allows for a fast detection of mechanical...... relaxations of polymers with only few nanograms of sample in a quasi-static condition. The polymers are spray coated on one side of silicon nitride (SiN) microstrings. These are pre-stressed suspended structures clamped on both ends to a silicon frame. The resonance frequency of the microstrings...... is then monitored as a function of increasing temperature. α and β relaxations in the polymer affect the net static tensile stress of the microstring and result in measureable local frequency slope maxima. Tg of PS and PMMA is detected at 91 ±2°C and 114 ±2°C, respectively. The results match well with the glass...
Micromechanical Fast Quasi-Static Detection of α and β Relaxations with Nanograms of Polymer
Bose, Sanjukta; Schmid, Silvan; Larsen, Tom
2015-01-01
Micromechanical string resonators are used as a highly sensitive tool for the detection of glass transition (Tg or α relaxation) and sub-Tg (β relaxation) temperatures of polystyrene (PS) and poly (methyl methacrylate) (PMMA). The characterization technique allows for a fast detection of mechanical...... relaxations of polymers with only few nanograms of sample in a quasi-static condition. The polymers are spray coated on one side of silicon nitride (SiN) microstrings. These are pre-stressed suspended structures clamped on both ends to a silicon frame. The resonance frequency of the microstrings...... is then monitored as a function of increasing temperature. α and β relaxations in the polymer affect the net static tensile stress of the microstring and result in measureable local frequency slope maxima. Tg of PS and PMMA is detected at 91 ±2°C and 114 ±2°C, respectively. The results match well with the glass...
Mousavi-Khatir, Roghayeh; Talebian, Saeed; Maroufi, Nader; Olyaei, Gholam Reza
2016-04-01
Neck pain is a common musculoskeletal disorder, especially among skilled workers who must keep their necks in a flexed position frequently during the day. The present study investigated changes in cervical flexion-relaxation phenomenon parameters after sustained neck flexion. The participants were 40 healthy subjects grouped by gender (20 females, 20 males). They were exposed to static neck flexion at the full angle of cervical flexion for 10 min. Each subject underwent three trials of cervical flexion and re-extension before and after this period. Differences in onset and cessation angle of flexion-relaxation phenomenon, maximum neck flexion angle, amplitude of neck muscle activation and flexion-relaxation ratio were evaluated. The maximum neck flexion angle significantly increased after sustained flexion. The onset of flexion-relaxation was significantly delayed during flexion, but cessation angle remained unchanged. Myoelectric activity of the cervical erector spinae muscles increased significantly after maintaining flexion, especially in female subjects. The flexion-relaxation ratio also decreased significantly. It was concluded that 10 min of static flexion results in a delay in flexion-relaxation phenomenon and a shortened silence period. Also the cervical erector spinae muscles are required to be active longer and generate more activity. These neuromuscular changes may be a risk factor for neck pain. Copyright © 2015 Elsevier Ltd. All rights reserved.
P.Haritha
2015-12-01
Full Text Available Background: Neck pain is a common problem within our society. Upper trapezius sternocleidomastoid and the levator scapulae are the most common postural muscles that tends to get shorten leading to restricted neck mobility. There is lack of evidence to allow conclusions to be drawn about the effectiveness of post isometric relaxation when compared with static stretching exercises. The aim is to find out the effectiveness of Post isometric relaxation Versus Static stretching in the subjects with chronic nonspecific neck pain. To evaluate the effectiveness of post isometric relaxation technique on pain by using Visual analoge scale, range of motion by using Universal Goniometry, and functional disability by using Neck Disability Index in chronic nonspecific neck pain. Methods: A convenient sample of thirty seven subjects was diagnosed with nonspecific neck pain was randomly allocated to one of the two treatment groups on the basis of the inclusion criteria. The experimental group (n=15 received three sessions of post isometric relaxation technique for trapezius, sternocleidomastoid and the levator scapulae and control group (n=15 received the three sessions of static stretching for trapezius, sternocliedomastiod and levator scapulae for four weeks. Results: Non parametric tests demonstrated a statistically significant difference with experimental group showing greater improvement in ROM, VAS, and NDI than the control group and significant difference within the group also. Conclusion: This study concluded and the results reflected that post isometric relaxation technique group had better improvement in reduction of pain, improvement in the range of motion, and increased neck functional activities than the static stretching group.
N. Vamsidhar
2014-12-01
Full Text Available Background: Flexibility is important in prevention of injury, muscular and postural imbalance more over the Hamstring flexibility has a lion share in sports performances and preventing DOMS. Stretching procedures increases the ROM by embarking on biomechanics and Neurologic and molecular mechanics. Hamstrings, the two joint muscle plays a crucial role in two joints integrity and also spine as they are in closed kinematic chain. The hamstring muscles represent the primary flexors of Knee. Hamstrings tightness results in Limits Knee extension when hip is flexed, Posterior Pelvic tilt, and flatten the lumbar spine. Methods: The subjects selected randomly and divided into two groups (Experimental group and control group.30 samples in One group applied with Static Stretch once a day for 3 repetitions 5 days a week for six weeks and 30 samples in other group applied with Hold relax technique once a day for 4 repetitions 5 days a week for six weeks. The knee joint range of motion was measured at the end of every week with Universal goniometer. Results: By comparing the means of Group – I, given Static Stretch and Group – II, given Hold relax Technique for six weeks implied that there is improvement of flexibility in Group – II and the ‘P’ value < 0.01 shows the difference is highly significant. Conclusion: This study concludes that the hold relax Technique method has proved to be better technique then the static stretch for improving hamstring flexibility.
Longitudinal static stability requirements for wing in ground effect vehicle
Yang, Wei; Yang, Zhigang; Collu, Maurizio
2015-06-01
The issue of the longitudinal stability of a WIG vehicle has been a very critical design factor since the first experimental WIG vehicle has been built. A series of studies had been performed and focused on the longitudinal stability analysis. However, most studies focused on the longitudinal stability of WIG vehicle in cruise phase, and less is available on the longitudinal static stability requirement of WIG vehicle when hydrodynamics are considered: WIG vehicle usually take off from water. The present work focuses on stability requirement for longitudinal motion from taking off to landing. The model of dynamics for a WIG vehicle was developed taking into account the aerodynamic, hydrostatic and hydrodynamic forces, and then was analyzed. Following with the longitudinal static stability analysis, effect of hydrofoil was discussed. Locations of CG, aerodynamic center in pitch, aerodynamic center in height and hydrodynamic center in heave were illustrated for a stabilized WIG vehicle. The present work will further improve the longitudinal static stability theory for WIG vehicle.
Longitudinal static stability requirements for wing in ground effect vehicle
Wei Yang
2015-03-01
Full Text Available The issue of the longitudinal stability of a WIG vehicle has been a very critical design factor since the first experimental WIG vehicle has been built. A series of studies had been performed and focused on the longitudinal stability analysis. However, most studies focused on the longitudinal stability of WIG vehicle in cruise phase, and less is available on the longitudinal static stability requirement of WIG vehicle when hydrodynamics are considered: WIG vehicle usually take off from water. The present work focuses on stability requirement for longitudinal motion from taking off to landing. The model of dynamics for a WIG vehicle was developed taking into account the aerodynamic, hydrostatic and hydrodynamic forces, and then was analyzed. Following with the longitudinal static stability analysis, effect of hydrofoil was discussed. Locations of CG, aerodynamic center in pitch, aerodynamic center in height and hydrodynamic center in heave were illustrated for a stabilized WIG vehicle. The present work will further improve the longitudinal static stability theory for WIG vehicle.
Longitudinal static stability requirements for wing in ground effect vehicle
Yang Wei
2015-06-01
Full Text Available The issue of the longitudinal stability of a WIG vehicle has been a very critical design factor since the first experimental WIG vehicle has been built. A series of studies had been performed and focused on the longitudinal stability analysis. However, most studies focused on the longitudinal stability of WIG vehicle in cruise phase, and less is available on the longitudinal static stability requirement of WIG vehicle when hydrodynamics are considered: WIG vehicle usually take off from water. The present work focuses on stability requirement for longitudinal motion from taking off to landing. The model of dynamics for a WIG vehicle was developed taking into account the aerodynamic, hydrostatic and hydrodynamic forces, and then was analyzed. Following with the longitudinal static stability analysis, effect of hydrofoil was discussed. Locations of CG, aerodynamic center in pitch, aerodynamic center in height and hydrodynamic center in heave were illustrated for a stabilized WIG vehicle. The present work will further improve the longitudinal static stability theory for WIG vehicle.
Static stability of collapsible tube conveying non-Newtonian fluid
Yushutin, V S
2014-01-01
The global static stability of a Starling Resistor conveying non-Newtonian fluid is considered. The Starling Resistor consists of two rigid circular tubes and axisymmetric collapsible tube mounted between them. Upstream and downstream pressures are the boundary condition as well as external to the collapsible tube pressure. Quasi one-dimensional model has been proposed and a boundary value problem in terms of nondimensional parameters obtained. Nonuniqueness of the boundary value problem is regarded as static instability. The analytical condition of instability which defines a surface in parameter space has been studied numerically. The influence of fluid rheology on stability of collapsible tube is established.
Stability and suppression of turbulence in relaxing molecular gas flows
Grigoryev, Yurii N
2017-01-01
This book presents an in-depth systematic investigation of a dissipative effect which manifests itself as the growth of hydrodynamic stability and suppression of turbulence in relaxing molecular gas flows. The work describes the theoretical foundations of a new way to control stability and laminar turbulent transitions in aerodynamic flows. It develops hydrodynamic models for describing thermal nonequilibrium gas flows which allow the consideration of suppression of inviscid acoustic waves in 2D shear flows. Then, nonlinear evolution of large-scale vortices and Kelvin-Helmholtz waves in relaxing shear flows are studied. Critical Reynolds numbers in supersonic Couette flows are calculated analytically and numerically within the framework of both linear and nonlinear classical energy hydrodynamic stability theories. The calculations clearly show that the relaxation process can appreciably delay the laminar-turbulent transition. The aim of the book is to show the new dissipative effect, which can be used for flo...
The longitudinal controls fixed static stability of tailless aircraft
de Castro, Helena V.
2000-01-01
This paper describes the development of a simple theory of the longitudinal controls fixed static stability of tailless aeroplanes. The classical theory, as developed for the conventional aircraft, is modified to accommodate the particular features of the tailless aeroplanes. The theory was then applied to a particular blended-wing-body tailless civil transport aircraft, BWB-98. Cranfield University
Convex Relaxation of Power Dispatch for Voltage Stability Improvement
Pedersen, Andreas Søndergaard; Blanke, Mogens; Jóhannsson, Hjörtur
2015-01-01
A method for enhancing the voltage stability ofa power system is presented in this paper. The method isbased on a stability-constrained optimal power flow approach,where dispatch is done such that a maximum L-index isminimised for all load busses in a transmission grid. It isshown that optimal...... dispatch is obtainable with enhancedmargins for voltage stability using a semidefinite relaxation ofthe optimal power flow problem, and that this problem canbe formulated as semidefinite program with a quasi-convexobjective. Numerical tests are performed on the IEEE-30 busand BPA systems. The feasibility...... of the method is demonstratedthrough demonstrating that improved voltage stability marginsare obtained for both systems....
More relaxed conditions for model predictive control with guaranteed stability
Bin LIU; Yugeng XI
2005-01-01
For the model predictive controller,terminal state satisfying a certain inequality can guarantee the stability but it is somewhat conservative.In this paper,we give a more relaxed stability condition by considering the effect of the initial state.Based on that we propose an algorithm to guarantee that the closed loop system is asymptotically stable.Finally,the conclusions are verified by a simulation.
Thermal stabilization of static single-mirror Fourier transform spectrometers
Schardt, Michael; Schwaller, Christian; Tremmel, Anton J.; Koch, Alexander W.
2017-05-01
Fourier transform spectroscopy has become a standard method for spectral analysis of infrared light. With this method, an interferogram is created by two beam interference which is subsequently Fourier-transformed. Most Fourier transform spectrometers used today provide the interferogram in the temporal domain. In contrast, static Fourier transform spectrometers generate interferograms in the spatial domain. One example of this type of spectrometer is the static single-mirror Fourier transform spectrometer which offers a high etendue in combination with a simple, miniaturized optics design. As no moving parts are required, it also features a high vibration resistance and high measurement rates. However, it is susceptible to temperature variations. In this paper, we therefore discuss the main sources for temperature-induced errors in static single-mirror Fourier transform spectrometers: changes in the refractive index of the optical components used, variations of the detector sensitivity, and thermal expansion of the housing. As these errors manifest themselves in temperature-dependent wavenumber shifts and intensity shifts, they prevent static single-mirror Fourier transform spectrometers from delivering long-term stable spectra. To eliminate these shifts, we additionally present a work concept for the thermal stabilization of the spectrometer. With this stabilization, static single-mirror Fourier transform spectrometers are made suitable for infrared process spectroscopy under harsh thermal environmental conditions. As the static single-mirror Fourier transform spectrometer uses the so-called source-doubling principle, many of the mentioned findings are transferable to other designs of static Fourier transform spectrometers based on the same principle.
Scalerandi, M; Johnson, P A
2003-01-01
Local interaction simulation approach simulations of the ultrasonic wave propagation in multi-grained materials have succeeded in reproducing most of the recently observed nonclassical nonlinear effects, such as stress-strain hysteresis and discrete memory in quasi-static experiments and a downwards shift of the resonance frequency and the generation of odd harmonics at specific amplitude rates in dynamics experiments. By including a simple mechanism of thermally activated random transitions, we can predict the occurrence of experimentally observed effects, such as the conditioning and relaxation of the specimen. Experiments are also suggested for a quantitative assessment of the validity of the model.
On the stability of Einstein static universe in massive bigravity
Mousavi, M
2016-01-01
We study the static cosmological solutions and their stability in the framework of massive bigravity theory with Friedmann-Robertson-Walker (FRW) metrics. By the modification proposed in the cosmological equations subject to a perfect fluid we obtain new solutions interpreted as the Einstein static universe. It turns out that the non-vanishing size of initial scale factor of Einstein static universe depends on the non-vanishing three-dimensional spatial curvature of FRW metrics and also the graviton's mass. By dynamical system approach and numerical analysis, we find that the extracted solutions for closed an open universes can be stable for some ranges of equation of state parameter and the values of fraction of two scale factors.
Static Voltage Stability Analysis by Using SVM and Neural Network
Mehdi Hajian
2013-01-01
Full Text Available Voltage stability is an important problem in power system networks. In this paper, in terms of static voltage stability, and application of Neural Networks (NN and Supported Vector Machine (SVM for estimating of voltage stability margin (VSM and predicting of voltage collapse has been investigated. This paper considers voltage stability in power system in two parts. The first part calculates static voltage stability margin by Radial Basis Function Neural Network (RBFNN. The advantage of the used method is high accuracy in online detecting the VSM. Whereas the second one, voltage collapse analysis of power system is performed by Probabilistic Neural Network (PNN and SVM. The obtained results in this paper indicate, that time and number of training samples of SVM, are less than NN. In this paper, a new model of training samples for detection system, using the normal distribution load curve at each load feeder, has been used. Voltage stability analysis is estimated by well-know L and VSM indexes. To demonstrate the validity of the proposed methods, IEEE 14 bus grid and the actual network of Yazd Province are used.
14 CFR 27.175 - Demonstration of static longitudinal stability.
2010-01-01
... speeds from 0.8 VNE − 10 kt to 0.8 VNE + 10 kt or, if VH is less than 0.8 VNE, from VH −10 kt to VH + 10... or VH, whichever is less; (4) The landing gear retracted; and (5) The rotorcraft trimmed at 0.8 VNE or VH, whichever is less. (c) V NE. Static longitudinal stability must be shown at speeds from...
14 CFR 29.175 - Demonstration of static longitudinal stability.
2010-01-01
... speeds from 0.8 VNE−10 kt to 0.8 VNE + 10 kt or, if VH is less than 0.8 VNE, from VH − 10 kt to VH + 10... or VH, whichever is less; (4) The landing gear retracted; and (5) The rotorcraft trimmed at 0.8 VNE or VH, whichever is less. (c) V NE. Static longitudinal stability must be shown at speeds from...
Semi-permeable wormholes and the stability of static wormholes
Novikov, D. I.; Doroshkevich, A. G.; Novikov, I. D.; Shatskii, A. A.
2009-12-01
Physical processes arising when an impermeable wormhole is irradiated by self-gravitating, exotic radiation are considered. It is shown that, in this case, the conditions required for the passage of signals fromanother universe into our own arise only in our Universe, whereas signals cannot pass through the wormhole in the opposite direction. Such wormholes are called semi-permeable. The stability of a static wormhole filled with radial magnetic field and exotic dust with a negative energy density is also considered.
NOVEL FORMULATION OF STATIC STABILITY FOR A WALKING QUADRUPED ROBOT
无
2003-01-01
By defining the static stable area for foot placement, a new approach to analysis of quadruped robot stability is presented.Unlike conventionally, the method avoids solving complicated direct kinematics of quadruped robot and shows the information on the robot stability and the selection of swing leg.Especially, the proposed algorithm can be used as real-time operation for on-line gait generation and control for quadruped robots.The effectiveness of the proposed approach is shown through a practical crawling experiment of the quadruped robot TITAN-VIII.
Evaluation of muscular stabilization ability during a static workout.
Staniszewski, Michał; Urbanik, Czesław; Staniszewski, Tadeusz
2010-01-01
The aim of this research was to determine the moving and stabilizing functions of selected groups of muscles during the process of static workout. 15 students of the Academy of Physical Education were tested in non-competitive training. Muscular torques achieved during flexing and extending big limb joints were used as the determinant of force. Comparative analysis of torque values achieved in passive stabilization (with support) and muscular stabilization (without support) in elbow and knee joints was carried out. The value of the force applied to the passively stabilizing element in a given measurement during the flexion of elbow and the extension of knee joint was tested. The results of these tests allowed us to learn the value of muscular torques and - after statistical analysis - the relationship between them in particular functions.
Importance of the different posterolateral knee static stabilizers: biomechanical study
Rodrigo Campos Pace Lasmar
2010-01-01
Full Text Available PURPOSE: The purpose of this study was to evaluate the relative importance of the different static stabilizers of the posterolateral corner of the knee in cadavers. METHODS: Tests were performed with the application of a varus and external rotation force to the knee in extension at 30 and 60 degrees of flexion using 10 cadaver knees. The forces were applied initially to an intact knee and then repeated after a selective sectioning of the ligaments into the following: section of the lateral collateral ligament; section of the lateral collateral ligament and the popliteofibular complex; and section of the lateral collateral ligament, the popliteofibular complex and the posterolateral capsule. The parameters studied were the angular deformity and stiffness when the knees were submitted to a 15 Newton-meter varus torque and a 6 Newton-meter external tibial torque. Statistical analysis was performed using the ANOVA (Analysis of Variance and Tukey's tests. RESULTS AND CONCLUSION: Our findings showed that the lateral collateral ligament was important in varus stability at 0, 30 and 60 degrees. The popliteofibular complex was the most important structure for external rotation stability at all angles of flexion and was also important for varus stability at 30 and 60 degrees. The posterolateral capsule was important for varus stability at 0 and 30 degrees and for external rotation stability in extension. Level of evidence: Level IV (cadaver study.
Benmelouka, Meriem; Borel, Alain; Moriggi, Loick; Helm, Lothar; Merbach, André E
2007-02-01
A multiple-frequency (9.4-325 GHz) and variable-temperature (276-320 K) electron paramagnetic resonance (EPR) study on low molecular weight gadolinium(III) complexes for potential use as magnetic resonance imaging (MRI) contrast agents has been performed. Peak-to-peak linewidths Delta Hpp and central magnetic fields have been analyzed within the Redfield approximation taking into account the static zero-field splitting (ZFS) up to the sixth order and the transient ZFS up to the second order. Longitudinal electronic relaxation is dominated by the static ZFS contribution at low magnetic fields (B 1.5 T). Whereas the static ZFS clearly depends on the nature of the chelating ligand, the transient ZFS does not. For the relatively fast rotating molecules studied water proton relaxivity is mainly limited by the fast rotation and electronic relaxation has only a marked influence at frequencies below 30 MHz. From our EPR results we can conclude that electronic relaxation will have no influence on the efficiency of Gd(III)-based MRI contrast agents designed for studies at very high magnetic fields (B > 3T).
Improving Power System Transient Stability with Static Synchronous Series Compensator
Prechanon Kumkratug
2011-01-01
Full Text Available Problem statement: Modern power system consists of the complicated network of transmission lines and carries heavy demand. Thus they cause in the stability problem. One of the major interests of power utilities is the improvement of power system transient behavior. Approach: Static Synchronous Series Compensator (SSSC is a power electronic based device that has the capability of controlling the power flow through a line. This study applies the SSSC to improve transient stability of power system. To verify the effect of the SSSC on transient stability, the mathematical model and control strategy of a SSSC is presented. The SSSC is represented by variable voltage injection with associate transformer leakage reactance and the voltage source. The series voltage injection model of SSSC is modeled into power flow equation and thus it is used to determine its control strategy. This study uses machine speed deviation to control it. The swing curves of the three phase faulted power system without and with a SSSC is tested and compared in various cases. Results: The swing curve of system without a SSSC gets increases monotonically and thus the system can be considered as unstable whereas the swing curves of system with a SSSC can be considered as stable. Conclusion: SSSSC can improve transient stability of power system.
GRID VOLTAGE STABILITY ENHANCEMENT USING PHOTOVOLTAIC BASED STATIC SYNCHRONOUS COMPENSATOR
Arun Bhaskar Mayilvaganan
2013-01-01
Full Text Available Today, we are mostly dependent on non renewable energy that have been and will continue to be a major cause of pollution and other environmental degradation. Because of these problems and our dwindling supply of petroleum, finding sustainable alternatives is becoming increasingly urgent. Perhaps, the greatest challenge is in devising a sustainable future, which relies on integration and control of renewable energy sources in grid distributed generation. This study presents the usage of utilizing Photovoltaic (PV Solar Farm (SF during idle conditions as Static Synchronous Compensator (STATCOM, to regulate the point of common coupling voltage when the wind farm supply the power to the grid. The proposed control will enable increased connections of WECS to the grid. MATLAB/Simulink based simulation results are presented for validation of the system. The PV-STATCOM increase the stability of the grid with interconnected wind farm system without any use of additional compensator.
Static interactions and stability of matter in Rindler space
Lenz, F; Yazaki, K
2010-01-01
Dynamical issues associated with quantum fields in Rindler space are addressed in a study of the interaction between two sources at rest generated by the exchange of scalar particles, photons and gravitons. These static interaction energies in Rindler space are shown to be scale invariant, complex quantities. The imaginary part will be seen to have its quantum mechanical origin in the presence of an infinity of zero modes in uniformly accelerated frames which in turn are related to the radiation observed in inertial frames. The impact of a uniform acceleration on the stability of matter and the properties of particles is discussed and estimates are presented of the instability of hydrogen atoms when approaching the horizon.
Effects of Contract-Relax, Static Stretching, and Isometric Contractions on Muscle-Tendon Mechanics.
Kay, Anthony D; Husbands-Beasley, Jade; Blazevich, Anthony J
2015-10-01
Loading characteristics of stretching techniques likely influence the specific mechanisms responsible for acute increases in range of motion (ROM). Therefore, the effects of a version of contract-relax (CR) proprioceptive neuromuscular facilitation stretching, static stretching (SS), and maximal isometric contraction (Iso) interventions were studied in 17 healthy human volunteers. Passive ankle moment was recorded on an isokinetic dynamometer, with EMG recording from the triceps surae, simultaneous real-time motion analysis, and ultrasound-imaging-recorded gastrocnemius medialis muscle and Achilles tendon elongation. Subjects then performed each intervention randomly on separate days before reassessment. Significant increases in dorsiflexion ROM (2.5°-5.3°; P stretching (P stretching and Iso (17.7%-22.1%; P 0.05), whereas significant reductions in muscle stiffness occurred after CR stretching and SS (16.0%-20.5%; P 0.05). Increases in peak passive moment (stretch tolerance) occurred after Iso (6.8%; P stretching (10.6%; P = 0.08), and SS (5.2%; P = 0.08); no difference in changes between conditions was found (P > 0.05). Significant correlations (rs = 0.69-0.82; P stretching suggest a broader adaptive response that likely explains its superior efficacy in acutely increasing ROM. Although mechanical changes appear tissue-specific between interventions, similar increases in stretch tolerance after all interventions are strongly correlated with changes in ROM.
Salloum, Ahmed
Constraint relaxation by definition means that certain security, operational, or financial constraints are allowed to be violated in the energy market model for a predetermined penalty price. System operators utilize this mechanism in an effort to impose a price-cap on shadow prices throughout the market. In addition, constraint relaxations can serve as corrective approximations that help in reducing the occurrence of infeasible or extreme solutions in the day-ahead markets. This work aims to capture the impact constraint relaxations have on system operational security. Moreover, this analysis also provides a better understanding of the correlation between DC market models and AC real-time systems and analyzes how relaxations in market models propagate to real-time systems. This information can be used not only to assess the criticality of constraint relaxations, but also as a basis for determining penalty prices more accurately. Constraint relaxations practice was replicated in this work using a test case and a real-life large-scale system, while capturing both energy market aspects and AC real-time system performance. System performance investigation included static and dynamic security analysis for base-case and post-contingency operating conditions. PJM peak hour loads were dynamically modeled in order to capture delayed voltage recovery and sustained depressed voltage profiles as a result of reactive power deficiency caused by constraint relaxations. Moreover, impacts of constraint relaxations on operational system security were investigated when risk based penalty prices are used. Transmission lines in the PJM system were categorized according to their risk index and each category was as-signed a different penalty price accordingly in order to avoid real-time overloads on high risk lines. This work also extends the investigation of constraint relaxations to post-contingency relaxations, where emergency limits are allowed to be relaxed in energy market models
SIMULATION OF THE TRANSITIONAL REGIME OF THE MOLDOVAN POWER UNDER STATIC STABILITY
Postolaty V.M.
2013-04-01
Full Text Available The paper presents the outcome of the Moldovan power system static stability modeling and analysis, considering the operation in parallel with the Ukrainian power system and the established operation regimes. The analysis includes verification of the reserve of static stability and definition of the static stability limits for a given operation mode, and the determination of the power system stability domain of the controlled system nodes. Parameters used for the analysis are the active power flows via controlled sections and the voltage levels at the controlled system nodes. Two options of Moldovan power system scheme are considered: a single-circuit transit Dniester HPP - Balti - Straseni – Chisinau 330kV and a double-circuit transit. Studies have shown that the implementation of the double-circuit transit would lead to better static stability parameters and lower power system losses. The analysis has been carried out based on the power system stability.
Static and dynamic stability analysis of the space shuttle vehicle-orbiter
Chyu, W. J.; Cavin, R. K.; Erickson, L. L.
1978-01-01
The longitudinal static and dynamic stability of a Space Shuttle Vehicle-Orbiter (SSV Orbiter) model is analyzed using the FLEXSTAB computer program. Nonlinear effects are accounted for by application of a correction technique in the FLEXSTAB system; the technique incorporates experimental force and pressure data into the linear aerodynamic theory. A flexible Orbiter model is treated in the static stability analysis for the flight conditions of Mach number 0.9 for rectilinear flight (1 g) and for a pull-up maneuver (2.5 g) at an altitude of 15.24 km. Static stability parameters and structural deformations of the Orbiter are calculated at trim conditions for the dynamic stability analysis, and the characteristics of damping in pitch are investigated for a Mach number range of 0.3 to 1.2. The calculated results for both the static and dynamic stabilities are compared with the available experimental data.
A.R. Morgridge
2002-01-01
Effect of initial grain size (I.G.S.) on static recrystallization softening in Cr steel(0.77wt.% CR) has been investigated through the use of interrupted hot compressiontests and stress relaxation curves from Gleeble 1500. Initial grain sizes were variedbetween 20 and 93 microns. Stress strains curves for Cr steel for different initialgrain sizes and recrystallization times have been highlighted. Similar observation wasmade for metadynamic recrystallization with shorter retardation times. Staticallyrecrystallized grain size also increased as initial grain size increases. It is found thatthe values of initial grain size have significant effects on the mean flow stress andstatic recrystallization kinetics as well as the peak strain values to initiate dynamicrecrystallization.
Stability of the Einstein static universe in modified theories of gravity
Boehmer, Christian G.; Hollenstein, Lukas; Lobo, Francisco S. N.; Seahra, Sanjeev S.
2010-01-01
We present a brief overview of the stability analysis of the Einstein static universe in various modified theories of gravity, like f(R) gravity, Gauss-Bonnet or f(G) gravity, and Horava-Lifshitz gravity.
Stability of the Einstein static universe in modified theories of gravity
Boehmer, Christian G.; Hollenstein, Lukas; Lobo, Francisco S. N.; Seahra, Sanjeev S.
2010-01-01
We present a brief overview of the stability analysis of the Einstein static universe in various modified theories of gravity, like f(R) gravity, Gauss-Bonnet or f(G) gravity, and Horava-Lifshitz gravity.
farzaneh saki; masumeh Baghban
2016-01-01
Objective: Balancing is the most basic function of the neuromuscular system in performing all simple and complex activities that contribute to health-related physical fitness. Core stability may be a contributing factor to static and dynamic balance. The aim of this study was to investigate the relationship between core stability muscle endurance and static and dynamic balance in basketball players. Methods: 100 basketball players (50 female and 50 male players) were selected randomly bas...
A Static Picture of the Relaxation and Intersystem Crossing Mechanisms of Photoexcited 2-Thiouracil.
Mai, Sebastian; Marquetand, Philipp; González, Leticia
2015-09-10
Accurate excited-state quantum chemical calculations on 2-thiouracil, employing large active spaces and up to quadruple-ζ quality basis sets in multistate complete active space perturbation theory calculations, are reported. The results suggest that the main relaxation path for 2-thiouracil after photoexcitation should be S2 → S1 → T2 → T1, and that this relaxation occurs on a subpicosecond time scale. There are two deactivation pathways from the initially excited bright S2 state to S1, one of which is nearly barrierless and should promote ultrafast internal conversion. After relaxation to the S1 minimum, small singlet-triplet energy gaps and spin-orbit couplings of about 130 cm(-1) are expected to facilitate intersystem crossing to T2, from where very fast internal conversion to T1 occurs. An important finding is that 2-thiouracil shows strong pyramidalization at the carbon atom of the thiocarbonyl group in several excited states.
Deformed Horava-Lifshitz Cosmology and Stability of Einstein Static Universe
Heydarzade, Y; Darabi, F
2015-01-01
Stability of the Einstein static universe versus the linear scalar, vector and tensor perturbations is investigated in the context of deformed Ho\\v{r}ava-Lifshitz cosmology inspired by entropic force scenario. A general stability condition against the linear scalar perturbations is obtained. Using this general condition, it is shown that there is no stable Einstein static universe for the case of flat universe, $k=0$. For the the special case of large values of running parameter of HL gravity $\\omega$, in a positively curved universe $k>0$, the domination of the quintessence and phantom matter fields with barotropic equation of state parameter $\\beta -\\frac{1}{3}$ are needed to be the dominant fields of the universe. Also, a neutral stability against the vector perturbations is obtained. Finally, an inequality including the cosmological parameters of the Einstein static universe is obtained for the stability against the tensor perturbations. It turns out that for large $\\omega$ values, there is a stability ag...
电力系统稳定性分析%Electrical Power System Static Stability Analysis
纪留利
2011-01-01
The article has carried on the narration to the electrical power system static stability research connotation,then performed from the epistemology and the methodology to analyze,discusses the electrical power system to carry on the static stability analysis the goal and the analysis method,as well as the excitation adjustment influence and enhanced the static stability measure。 Small disturbance the method primarily to carry on the analysis,has analyzed the static state stable safety factor,the static stable practical criterion concept as well as does not count when the power set damping action analyzes the system static stability method and the criterion,and counts when the power set damping action analyzes the system static stability method and the criterion from the linearity to the non-linear trans formation,from takes to analyze the method to take the non-analysis method the transformation,provides the methodology instruction for the electrical power system static stability research。%本文讨论了电力系统进行静态稳定性分析的目的和分析的方法,及励磁调节的影响和提高静态稳定性的措施。其中重点以小干扰法为主分析了电力系统的静态稳定性,实现了从线性向非线性的转变、从重视解析方法到重视非解析方法的转变过程,为电力系统静态稳定性研究提供方法论指导。
A Mathematical Model and Numerical Simulation of the Static Stability of a Tractor
Ivan Demšar
2012-09-01
Full Text Available Tractor overturning remains a serious problem in agricultural activities. A detailed analysis of problems and causes leading to a tractor overturn have revealed that by improving tractor’s static stability we can positively influence the safety as early as during the concept phase. We designed a mathematical model and a numerical simulation of the static stability of a tractor with an oscillating front axle in relation to its position on a slope. It was followed by analysing the changes of individual parameters, such as the position of the centre of gravity, the wheelbase, the wheel track width and the height of the oscillating axle mounting point, and their impact on tractor’s static stability in relation to its position on a slope. Results show that manipulating these parameters can significantly increase tractor’s static stability. A better static stability is directly proportional to improved dynamic stability, resulting in a better safety in a view of the tractor overturn, particularly while working on a sloping terrain.
Chiu, Eddy; Huang, Huang; Wu, Tao; Liu, Sheng
2010-01-01
In this paper, we propose a robust transceiver design for the K-pair quasi-static MIMO interference channel. Each transmitter is equipped with M antennas, each receiver is equipped with N antennas, and the k-th transmitter sends L_k independent data streams to the desired receiver. In the literature, there exist a variety of theoretically promising transceiver designs for the interference channel such as interference alignment-based schemes, which have feasibility and practical limitations. In order to address practical system issues and requirements, we consider a transceiver design that enforces robustness against imperfect channel state information (CSI) as well as fair performance among the users in the interference channel. Specifically, we formulate the transceiver design as an optimization problem to maximize the worst-case signal-to-interference-plus-noise ratio among all users. We devise a low complexity iterative algorithm based on alternative optimization and semi-definite relaxation techniques. Nu...
farzaneh saki
2016-03-01
Full Text Available Objective: Balancing is the most basic function of the neuromuscular system in performing all simple and complex activities that contribute to health-related physical fitness. Core stability may be a contributing factor to static and dynamic balance. The aim of this study was to investigate the relationship between core stability muscle endurance and static and dynamic balance in basketball players. Methods: 100 basketball players (50 female and 50 male players were selected randomly based on the including criteria.To evaluate core stability muscle strength, a set of tests from core stability exercises was used. Static and dynamic balance were evaluated by Bass Stick and Y balance test respectively. Normality of the data was evaluated using the Kolmogorov Smirnoff test. Data analysis was performed by Spearman product moment coefficient test and independent samples t test. Significant level of p&le0/05 was used in all statistical analyses. Results: Results of t-test showed no significant difference between static balance in boys and girls, while significant differences were observed between dynamic balance and core stability in males and females. In other words, core stability and dynamic balance in boys were more than girls. Also, the results of correlation analysis showed a significant relationship between core stability and dynamic balance (p=0.00 However, no significant relationship was observed between core stability and static balance (p=0.451. Conclusion: Due to the correlation between muscle endurance and dynamic balance in the present study, it can be implied that core stability exercises can improve balance.
Stability and Convergence of Relaxation Schemes to Hyperbolic Balance Laws via a Wave Operator
Miroshnikov, Alexey; Trivisa, Konstantina
2014-01-01
This article deals with relaxation approximations of nonlinear systems of hyperbolic balance laws. We introduce a class of relaxation schemes and establish their stability and convergence to the solution of hyperbolic balance laws before the formation of shocks, provided that we are within the framework of the compensated compactness method. Our analysis treats systems of hyperbolic balance laws with source terms satisfying a special mechanism which induces weak dissipation in the spirit of D...
Static-dynamic stability of the body gymnasts qualifications
Litvinenko Y.V.
2015-01-01
Full Text Available Purpose: evaluation of individual ways of postural control gymnasts skilled in solving problems on the stability of the body in the motor tests. Material : The study involved engaged in gymnastics (n = 9. The measurements were carried out on the platform stabilographic Kistler. Tests used: handstand, Biryuk sample, sample Romberg. Results: set individual ways microvibrations parts of the body and makrokolebany in the sagittal and frontal planes. Joined symmetry and asymmetry postural control of the body, the various indicators of energy expenditure. The quality of postural control in the performance of motor tests were deterministic complex conditions of body position on the support, limited visual orientation. Also corresponds to the test specificity of the sport. Conclusions : The method microvibrations in solving problems on the stability of the body in the motor tests gymnasts is the most strategically important for the effective development and management of a system of regulation poses athlete. Confirmation rates are economical expenditure of energy during motor tests.
Voltage stability analysis of grid-connected wind farms with FACTS: Static and dynamic analysis
Kevin Zibran Heetun
2016-01-01
Full Text Available Recently, analysis of some major blackouts and failures of power system shows that voltage instability problem has been one of the main reasons of these disturbances and network collapses. In this article, a systematic approach to voltage stability analysis using various techniques for the IEEE 14-bus case study is presented. Static analysis is used to analyze the voltage stability of the system under study, while the dynamic analysis is used to evaluate the performance of compensators. The static techniques used are power flow, V–P curve analysis, and Q–V modal analysis. In this study, Flexible Alternating Current Transmission system (FACTS devices—namely, static synchronous compensators (STATCOMs and static var compensators (SVCs—are used as reactive power compensators, taking into account maintaining the violated voltage magnitudes of the weak buses within the acceptable limits defined in ANSI C84.1. Simulation results validate that both the STATCOMs and the SVCs can be effectively used to enhance the static voltage stability and increasing network loadability margin. Additionally, based on the dynamic analysis results, it has been shown that STATCOMs have superior performance, in dynamic voltage stability enhancement, compared to SVCs.
Optical-coupling nuclear spin maser under highly stabilized low static field
Yoshimi, A., E-mail: yoshimi@ribf.riken.jp [RIKEN Nishina Center (Japan); Inoue, T.; Uchida, M.; Hatakeyama, N.; Asahi, K. [Tokyo Institute of Technology, Department of Physics (Japan)
2008-01-15
A nuclear spin maser of a new type, that employs a feedback scheme based on optical nuclear spin detection, has been fabricated. The spin maser is operated at a low static field of 30 mG by using the optical detection method. The frequency stability and precision of the spin maser have been improved by a highly stabilized current source for the static magnetic field. An experimental setup to search for an electric dipole moment (EDM) in {sup 129}Xe atom is being developed.
Nonlinear Slewing Spacecraft Control Based on Exergy, Power Flow, and Static and Dynamic Stability
Robinett, Rush D.; Wilson, David G.
2009-10-01
This paper presents a new nonlinear control methodology for slewing spacecraft, which provides both necessary and sufficient conditions for stability by identifying the stability boundaries, rigid body modes, and limit cycles. Conservative Hamiltonian system concepts, which are equivalent to static stability of airplanes, are used to find and deal with the static stability boundaries: rigid body modes. The application of exergy and entropy thermodynamic concepts to the work-rate principle provides a natural partitioning through the second law of thermodynamics of power flows into exergy generator, dissipator, and storage for Hamiltonian systems that is employed to find the dynamic stability boundaries: limit cycles. This partitioning process enables the control system designer to directly evaluate and enhance the stability and performance of the system by balancing the power flowing into versus the power dissipated within the system subject to the Hamiltonian surface (power storage). Relationships are developed between exergy, power flow, static and dynamic stability, and Lyapunov analysis. The methodology is demonstrated with two illustrative examples: (1) a nonlinear oscillator with sinusoidal damping and (2) a multi-input-multi-output three-axis slewing spacecraft that employs proportional-integral-derivative tracking control with numerical simulation results.
Stability of Einstein static state universe in the spatially flat branemodels
Zhang, Kaituo; Wu, Puxun; Yu, Hongwei; Luo, Ling-Wei
2016-07-01
With the assumption that a perfect fluid with a constant equation of state is the only energy component on the brane, we study the stability of Einstein static state solution under homogeneous and inhomogeneous scalar perturbations in both spatially flat Randall-Sundrum (RS) and Shtanov-Sahni (SS) braneworlds. We find that if the perfect fluid has a phantom-like property and the "Weyl fluid" originating from the projection of the bulk Weyl tensor onto the brane behaves like a radiation with positive energy density, the Einstein static state solution is stable in the SS braneworld, but unstable in the RS one. Furthermore, we demonstrate that the static state solution is also stable in the bulk with a timelike extra dimension. Thus, in the model where the extra dimension is timelike, our universe can stay at the Einstein static state past-eternally, which means that the big bang singularity might be resolved successfully by an emergent scenario.
Stability of Einstein static state universe in the spatially flat branemodels
Zhang, Kaituo [Department of Physics, Anhui Normal University, Wuhu, Anhui 241000 (China); Wu, Puxun [Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Center for High Energy Physics, Peking University, Beijing 100080 (China); Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn [Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China); Luo, Ling-Wei [Institute of Physics, Chiao Tung University, Hsinchu 300, Taiwan (China)
2016-07-10
With the assumption that a perfect fluid with a constant equation of state is the only energy component on the brane, we study the stability of Einstein static state solution under homogeneous and inhomogeneous scalar perturbations in both spatially flat Randall–Sundrum (RS) and Shtanov–Sahni (SS) braneworlds. We find that if the perfect fluid has a phantom-like property and the “Weyl fluid” originating from the projection of the bulk Weyl tensor onto the brane behaves like a radiation with positive energy density, the Einstein static state solution is stable in the SS braneworld, but unstable in the RS one. Furthermore, we demonstrate that the static state solution is also stable in the bulk with a timelike extra dimension. Thus, in the model where the extra dimension is timelike, our universe can stay at the Einstein static state past-eternally, which means that the big bang singularity might be resolved successfully by an emergent scenario.
Impact on Generator Reactive Power Limits on a Static Voltage Stability
TOVAR-GONZALEZ, E. A.
2011-11-01
Full Text Available Voltage stability margin in a power system is closely related with the availability of reactive power in the system. Therefore, adequate modeling of the reactive power sources becomes an important issue in this type of studies. The Minimum Singular Value of the load flow Jacobian matrix has been commonly used as a static voltage stability index. In this paper, such index is used to assess the influence on the static voltage stability limit of modeling the generators reactive power limits by its capability curve. Simulation results on a test system indicate that modeling the reactive power limits of the generating units by the simplified Qmin/Qmax approach, commonly used by most of the load flow programs, yields optimistic values for this voltage stability index.
Influence of dopant ion on localized relaxation of an oxygen vacancy in stabilized zirconia
Ohta, M.; Wigmore, J. K.; Nobugai, K.; Miyasato, T.
2002-05-01
It is well known that stabilized zirconia exhibits long-range transport of oxygen ions which gives rise to diffusion relaxation of oxygen vacancies. The internal friction and the change in sound velocity in single-crystal calcia-stabilized zirconia (CSZ) doped with 12 mol % CaO were measured for longitudinal sound waves in the frequency range from 20 Hz to 700 Hz using a vibrating reed technique. In the temperature range from 300 K to 700 K, the relaxation strength exhibits strong anisotropy with respect to the directions of the k vectors. As the frequency increases the internal friction peak and the change in sound velocity shift toward high temperature, and the relaxation strength remains constant. The results show that a smaller number of oxygen vacancies contribute to diffusion relaxation than to localized relaxation, which is attributed to hopping of bound oxygen vacancies within the local structure. Comparison of the results with those reported previously for yttria-stabilized zirconia (YSZ) doped with 9.5 mol % Y2O3, suggests that oxygen vacancies are more strongly bound by the local structure in CSZ than in YSZ.
Relaxation oscillations, stability, and cavity feedback in a superradiant Raman laser
Bohnet, Justin G; Weiner, Joshua M; Cox, Kevin C; Thompson, James K
2012-01-01
We experimentally study the relaxation oscillations and amplitude stability properties of an optical laser operating deep into the bad-cavity regime using a laser-cooled $^{87}$Rb Raman laser. By combining measurements of the laser light field with non-demolition measurements of the atomic populations, we infer the response of the the gain medium represented by a collective atomic Bloch vector. The results are qualitatively explained with a simple model. Measurements and theory are extended to include the effect of intermediate repumping states on the closed-loop stability of the oscillator and the role of cavity-feedback on stabilizing or enhancing relaxation oscillations. This experimental study of the stability of an optical laser operating deep into the bad-cavity regime will guide future development of superradiant lasers with ultranarrow linewidths.
Relaxation oscillations, stability, and cavity feedback in a superradiant Raman laser.
Bohnet, Justin G; Chen, Zilong; Weiner, Joshua M; Cox, Kevin C; Thompson, James K
2012-12-21
We experimentally study the relaxation oscillations and amplitude stability properties of an optical laser operating deep into the bad-cavity regime using a laser-cooled ^{87}Rb Raman laser. By combining measurements of the laser light field with nondemolition measurements of the atomic populations, we infer the response of the gain medium represented by a collective atomic Bloch vector. The results are qualitatively explained with a simple model. Measurements and theory are extended to include the effect of intermediate repumping states on the closed-loop stability of the oscillator and the role of cavity feedback on stabilizing or enhancing relaxation oscillations. This experimental study of the stability of an optical laser operating deep into the bad-cavity regime will guide future development of superradiant lasers with ultranarrow linewidths.
Stability of SU(2) Quantum Skyrmion and Static Properties of Nucleons
Acus, A
1997-01-01
The Skyrme model is considered quantum mechanically ab initio in various irreducible representations of the SU(2) group. The canonical quantization procedure yields negative mass correction ensuring existence of stabile soliton solution even in chiral limit. The evaluated static properties of nucleons (masses, magnetic moments, radii etc.) are in a good agreement with experimental data.
Balle, S S; Magnusson, S P; McHugh, M P
2015-12-01
The purpose of this study was to determine the acute effects of contract-relax stretching (CRS) vs static stretching (SS) on strength loss and the length-tension relationship. We hypothesized that there would be a greater muscle length-specific effect of CRS vs SS. Isometric hamstring strength was measured in 20 healthy people at four knee joint angles (90°, 70°, 50°, 30°) before and after stretching. One leg received SS, the contralateral received CRS. Both stretching techniques resulted in significant strength loss, which was most apparent at short muscle lengths [SS: P = 0.025; stretching × angle P stretching × angle P stretch-induced strength loss was greater (P = 0.015) after CRS (11.7%) vs SS (3.7%). The muscle length effect on strength loss was not different between CRS and SS (stretching × angle × stretching technique P = 0.43). Contrary to the hypothesis, CRS did not result in a greater shift in the length-tension relationship, and in fact, resulted in greater overall strength loss compared with SS. These results support the use of SS for stretching the hamstrings.
KERIM SOZBIR
2016-04-01
Full Text Available The purpose of this case study was to describe the acute effects of contract-relax proprioceptive neuromuscular facilitation (cRPNF and static stretching (SS on hamstring flexibility, vertical jump performance and electromyography (EMG of vastus lateralis (VL, vastus medialis (VM and gastrocnemius (GAS in two sedentary males. Each participant completed 8 activities: warm-up, pre-stretching range of motion (ROM of hip, pre-stretching countermovement jump (cMJ, pre-stretching EMG recording, cRPNF or SS procedure, post-stretching ROM of hip, post-stretching cMJ and post-stretching EMG recording. The results of this study revealed that there were no significant increases in ROM of hip (25,34% and 24,19% and no significant decreases in cMJ (-8,67% and -8,17%, EMG activities of VL (-12,52% and -29,34%, VM (-13,02% and -32,80% and GAS (-20,63% and -24,81% following cRPNF and SS. There were no significant differences were found between both experimental groups for all variables (p > 0,05. It was concluded that cRPNF ans SS resulted in similar changes of ROM of the hip joint, cMJ and EMG activities of VL, VM and GAS muscles in sedentary males.
Balle, S S; Magnusson, S P; McHugh, M P
2015-01-01
The purpose of this study was to determine the acute effects of contract-relax stretching (CRS) vs static stretching (SS) on strength loss and the length-tension relationship. We hypothesized that there would be a greater muscle length-specific effect of CRS vs SS. Isometric hamstring strength...... was measured in 20 healthy people at four knee joint angles (90°, 70°, 50°, 30°) before and after stretching. One leg received SS, the contralateral received CRS. Both stretching techniques resulted in significant strength loss, which was most apparent at short muscle lengths [SS: P = 0.025; stretching × angle.......7%) vs SS (3.7%). The muscle length effect on strength loss was not different between CRS and SS (stretching × angle × stretching technique P = 0.43). Contrary to the hypothesis, CRS did not result in a greater shift in the length-tension relationship, and in fact, resulted in greater overall strength...
Influence of caster diameter on the static and dynamic forward stability of occupied wheelchairs.
Kirby, R L; McLean, A D; Eastwood, B J
1992-01-01
The hypothesis that the static and dynamic forward stability of an occupied wheelchair would increase as a function of the caster diameter was tested in 20 able-bodied subjects. A device was attached to the wheelchair frame so that casters with different diameters could be used. With platform testing of static stability, the occupied wheelchair equipped with casters with diameters of 10.2, 20.3, 25.4, and 33.0cm, tipped at mean (+/- 1SD) angles of 23.8 degrees (+/- 1.3 degrees), 25.2 degrees (+/- 1.4 degrees), 26.1 degrees (+/- 1.4 degrees), and 28.2 degrees (+/- 1.9 degrees), respectively. The relationship between static stability (y, in degrees) and caster diameter (x, in cm) can be expressed by the equation y = 23.5-.0196 chi + .00484 x2 (p = .0001). Dynamic stability was tested by having subjects descend a 5 degree ramp, by gravity alone, from progressively farther up the ramp until a full forward tip occurred (footrests contacted the floor) when the wheelchair struck a 5-cm-high obstruction with sufficient speed. The mean tipping speeds for the dynamic tests were .85 (+/- .08), .85 (+/- .08), .89 (+/-.07), and 1.04 (+/- .14) m/sec for the wheelchair fitted with the caster diameters ranging from smallest to largest, respectively. The relationship between dynamic stability (y, tipping speed in m/sec) and caster diameter (chi, in cm) can be expressed by the equation y = .788 + .0139 chi-.00110 chi 2 + .0000276 chi 3 (p = .0001). The relationship between caster diameter and forward wheelchair stability should be considered in wheelchair design and prescription.
Static feedback stabilization of nonlinear systems with single sensor and single actuator.
Wang, Jiqiang; Hu, Zhongzhi; Ye, Zhifeng
2014-01-01
This paper considers a single sensor and single actuator approach to the static feedback stabilization of nonlinear systems. This is essentially a remote control problem that is present in many engineering applications. The proposed method solves this problem that is less expensive to implement and more reliable in practice. Significant results are obtained on the design of controllers for stabilizing the nonlinear systems. Important issues on control implementation are also discussed. The proposed design method is validated through its application to nonlinear control of aircraft engines.
Static and dynamic stability of the guidance force in a side-suspended HTS maglev system
Zhou, Dajin; Cui, Chenyu; Zhao, Lifeng; Zhang, Yong; Wang, Xiqing; Zhao, Yong
2017-02-01
The static and dynamic stability of the guidance force in a side-suspended HTS-PMG (permanent magnetic guideway) system were studied theoretically and experimentally. It is found that there are two types of guidance force that exist in the HTS-PMG system, which are sensitive to the levitation gap and the arrangement of YBCO bulks around the central axis of the PMG. An optimized YBCO array was used to stabilize the system, which enabled a side-suspended HTS-PMG maglev vehicle to run stably at 102 km h-1 on a circular test track with 6.5 m in diameter.
Enhancement of a Power System Transient Stability Using Static Synchronous Series Compensator SSSC
Mustafa M. Al-Eedany
2013-01-01
Full Text Available Static Synchronous Series Compensator (SSSC is a well known device for effectively regulating the active power flow in a power system. In this paper, the SSSC linearized power flow equations are incorporated into Newton-Raphson algorithm in a MATLAB written program to investigate the control of active poweer flow and the transient stability of a five bus and a thirty bus IEEE test systems, during abnormal conduction (three phase fault near buses. A comparison of the results obtained for the base case without SSSC and with it to investigate the effectiveness of the device on both of the active power flow and the transient stability.
Dynamic and Static Combination Analysis Method of Slope Stability Analysis during Earthquake
Liang Lu
2014-01-01
Full Text Available The results of laboratory model tests for simulating the slope failure due to vibration, including unreinforced slope and the slope reinforced by using geotextile, show that the slope failure occurs when a cumulative plastic displacement exceeds a certain critical value. To overcome the defects of conventional stability analysis, which evaluates the slope characteristics only by its strength parameters, a numerical procedure considering the stiffness and deformation of materials and geosynthetics is proposed to evaluate the seismic slope stability. In the proposed procedure, the failure of slope is defined when the cumulative plastic displacement calculated by a dynamic response analysis using actual seismic wave exceeds the critical value of displacement estimated by a static stability analysis considering seismic coefficient. The proposed procedure is applied to the laboratory model tests and an actual failure of slope in earthquake. The case study shows the possibility that the proposed procedure gives the realistic evaluation of seismic slope stability.
Zhang, Baoyong; Lam, James; Xu, Shengyuan
2015-07-01
This paper revisits the problem of asymptotic stability analysis for neural networks with distributed delays. The distributed delays are assumed to be constant and prescribed. Since a positive-definite quadratic functional does not necessarily require all the involved symmetric matrices to be positive definite, it is important for constructing relaxed Lyapunov-Krasovskii functionals, which generally lead to less conservative stability criteria. Based on this fact and using two kinds of integral inequalities, a new delay-dependent condition is obtained, which ensures that the distributed delay neural network under consideration is globally asymptotically stable. This stability criterion is then improved by applying the delay partitioning technique. Two numerical examples are provided to demonstrate the advantage of the presented stability criteria.
On convection and static stability during the AMMA SOP3 campaign
Embolo Embolo, G. B.; Lenouo, André; Nzeukou, Armand T.; Vondou, Derbetini A.; Kamga, F. Mkankam
2017-01-01
Using radiosonde dataset from 15 weather stations over West Africa, this paper investigates the contribution of the couple convection-static stability in the framework of the African monsoon multidisciplinary analyses Special Observing Period 3 (AMMA SOP3) experiment. Within this 31-day period, the boundary layer-winds depictions have revealed the West African monsoon's (WAM) depth (around 1500 m) is not thick enough to trigger intense convection. However, the midlevel winds distribution (700-600 hPa) has shown the average African easterly jet core strength (15 m s-1) is sufficient to allow the development of African easterly waves (AEWs) necessary for squall lines activities. In return, in the upper levels (200-100 hPa), the speed (below 18 m s-1) of the mean Tropical easterly jet (TEJ) core cannot favor midlevel updrafts. The free tropospheric humidity (FTH) depiction has indicated convective events are more likely in the western Sahel where the highest FTH (FTH >50 %) are recorded. The static stability analysis has testified that convection is stronger in the semi-arid (SA) area during night time (0000 GMT). However, convective activities are inhibited in the wet equatorial (WE) region due to mean low-level stability. We used METEOSAT Second Generation (MSG) infrared (IR10.8) imagery of the 8th September 2006 to confirm that result. Furthermore, a maximum midtropospheric static stability combined with maximum relative humidity (RH) was found on the fringe of the Saharan air layer's (SAL) top (altitude around 5.3 km) in the WE region.
Application of Cat Swarm Optimization in testing Static Load Models for Voltage Stability
G. Naveen Kumar
2016-03-01
Full Text Available Power System Load Modeling is a method which is used to model the power system and essential for voltage stability studies. Voltage stability defines the ability of a power network to maintain steady state voltages at all the buses under normal operating conditions, and when subjected to a disturbance. The research presented as part of this paper, deals with analysis of different static load models for voltage stability studies. The precision of the results are directly related to the load models used in this analysis. The method is analyzed using continuation power flow routine. Flexible AC Transmission System technology with a combination of Cat Swarm Optimization Meta Heuristic Search approach is applied to give a solution for the problem of instability. The effectiveness of the proposed method is demonstrated through quantitative simulation on standard IEEE 14 bus system for contingency condition.
JI-WON SHIN; GUI-BIN SONG; JOOYEON KO
2017-01-01
[Abstract.] [Purpose] The purpose of this case series was to examination the effects of trunk and neck stabilization exercise on the static, dynamic trunk balance abilities of children with cerebral palsy...
Bo Ling GUO; Gan Shan YANG
2004-01-01
We prove the existence of solutions of the static Landau-Lifshitz equation with multidirect effective field and with Dirichlet boundary condition, and establish the stability of the solution of Landau-Lifshitz equation with respect to time.
New Systematic CFD Methods to Calculate Static and Single Dynamic Stability Derivatives of Aircraft
Bai-gang Mi
2017-01-01
Full Text Available Several new systematic methods for high fidelity and reliability calculation of static and single dynamic derivatives are proposed in this paper. Angle of attack step response is used to obtain static derivative directly; then translation acceleration dynamic derivative and rotary dynamic derivative can be calculated by employing the step response motion of rate of the angle of attack and unsteady motion of pitching angular velocity step response, respectively. Longitudinal stability derivative calculations of SACCON UCAV are taken as test cases for validation. Numerical results of all cases achieve good agreement with reference values or experiments data from wind tunnel, which indicate that the proposed methods can be considered as new tools in the process of design and production of advanced aircrafts for their high efficiency and precision.
Seismic stability analysis of expanded MSW landfills using pseudo-static limit equilibrium method.
Choudhury, Deepankar; Savoikar, Purnanand
2011-02-01
Capacity expansion of existing landfills is the most economical alternative to constructing new landfills where cost of land is prohibitive. From the safety point of view, the stability analyses of existing landfills expanded either vertically and/or laterally are required for different stages of construction, operation and during closure of a landfill. In the present study, a pseudo-static limit equilibrium seismic stability analysis was performed for a typical side-hill type municipal solid waste (MSW) landfill expanded using an engineered berm. Seismic stability analyses were performed for the two critical cases, namely when the failure surface passes below the berm (under berm) and when the failure surface passes over the back slope of the berm (over berm). Close-form solutions were developed for the upper bound and lower bound factor of safety and the yield acceleration of such slopes under both failure conditions. From parametric analyses it was observed that as the height of the berm increased, the factor of safety for both the over-berm failure and the under-berm failure conditions also increased. The average factor of safety and yield acceleration coefficient were found and the under-berm failure condition became critical for a back slope steeper than 1.7H : 1V. The average factor of safety decreased as both horizontal and vertical seismic accelerations increased. Comparisons between the present results and those in the literature for the static case showed good agreement and the present results of the pseudo-static seismic case were found to be of particular importance.
Madariaga, A., E-mail: amadariaga@mondragon.edu [Mechanical and Industrial Production Department, Faculty of Engineering, Mondragon Unibertsitatea, Loramendi 4, Mondragon 20500 Gipuzkoa (Spain); Esnaola, J.A.; Arrazola, P.J. [Mechanical and Industrial Production Department, Faculty of Engineering, Mondragon Unibertsitatea, Loramendi 4, Mondragon 20500 Gipuzkoa (Spain); Ruiz-Hervias, J.; Muñoz, P. [Departamento Ciencia de Materiales, ETSI Caminos, Universidad Politécnica de Madrid, c/Profesor Aranguren s/n, Madrid 28040 (Spain); Ostolaza, K. [Materials and Processes Technology Department, ITP S.A., Parque Tecnológico, Edificio 300, 48170 Zamudio (Spain)
2015-01-03
Tensile residual stresses are very often generated on the surface when machining nickel alloys. In order to determine their influence on the final mechanical behaviour of the component residual stress stability should be considered. In the present work the evolution of surface residual stresses induced by machining in Inconel 718 under static loading at room temperature was studied experimentally and numerically. An Inconel 718 disc was face turned employing industrial working conditions and specimens for tensile tests were extracted from the disc. Surface residual stresses were measured by X-ray diffraction for initial state and after applying different loads over the material's yield stress. Then, a finite element model based on the surface–core approach was fitted to experimental results and the study was extended to analyse the influence of load level, degree of work-hardening and initial surface conditions. For the studied case, initial tensile surface residual stress (776 MPa) became even more tensile when applying loads higher than the material yield stress, but a shift was observed at the highest applied load (1350 MPa) and initial residual stress was relaxed about 170 MPa. This particular behaviour is associated to the modified stress–strain properties of the machined affected surface layer which was strongly work-hardened. Moreover, if the work-hardened properties are not considered in the finite element model results differ substantially from experiments. Surface residual stress stability also depends on the initial surface residual stress, but the degree of work-hardening induced by the machining process must be considered as well. If the difference between the yield stress of the surface and the yield stress of the core is lower than the initial surface residual stress, the surface begins yielding first and consequently the surface residual stress is decreased. In contrast, if the difference between the yield stress of the surface and the
The Relaxation Properties of Myofibrils Are Compromised by Amino Acids that Stabilize α-Tropomyosin.
Scellini, Beatrice; Piroddi, Nicoletta; Matyushenko, Alexander M; Levitsky, Dmitrii I; Poggesi, Corrado; Lehrer, Sherwin S; Tesi, Chiara
2017-01-24
We investigated the functional impact of α-tropomyosin (Tm) substituted with one (D137L) or two (D137L/G126R) stabilizing amino acid substitutions on the mechanical behavior of rabbit psoas skeletal myofibrils by replacing endogenous Tm and troponin (Tn) with recombinant Tm mutants and purified skeletal Tn. Force recordings from myofibrils (15°C) at saturating [Ca(2+)] showed that Tm-stabilizing substitutions did not significantly affect the maximal isometric tension and the rates of force activation (kACT) and redevelopment (kTR). However, a clear effect was observed on force relaxation: myofibrils with D137L/G126R or D137L Tm showed prolonged durations of the slow phase of relaxation and decreased rates of the fast phase. Both Tm-stabilizing substitutions strongly decreased the slack sarcomere length (SL) at submaximal activating [Ca(2+)] and increased the steepness of the SL-passive tension relation. These effects were reversed by addition of 10 mM 2,3-butanedione 2-monoxime. Myofibrils also showed an apparent increase in Ca(2+) sensitivity. Measurements of myofibrillar ATPase activity in the absence of Ca(2+) showed a significant increase in the presence of these Tms, indicating that single and double stabilizing substitutions compromise the full inhibition of contraction in the relaxed state. These data can be understood with the three-state (blocked-closed-open) theory of muscle regulation, according to which the mutations increase the contribution of the active open state in the absence of Ca(2+) (M(-)). Force measurements on myofibrils substituted with C-terminal truncated TnI showed similar compromised relaxation effects, indicating the importance of TnI-Tm interactions in maintaining the blocked state. It appears that reducing the flexibility of native Tm coiled-coil structure decreases the optimum interactions of the central part of Tm with the C-terminal region of TnI. This results in a shift away from the blocked state, allowing myosin binding and
Bampouras, Theodoros M; Dewhurst, Susan
2016-05-01
Food shopping is an important aspect of maintaining independence and social interaction in older age. Carriage of shopping bags alters the body's weight distribution which, depending on load distribution, could potentially increase instability during standing and walking. The study examined the effect of carrying UK style shopping bags on static postural stability and gait in healthy older and young females. Nine older (71.0±6.0 years) and 10 young (26.7±5.2 years) females were assessed in five conditions carrying no bags, one 1.5kg bag in each hand, one 3kg bag in each hand, one 1.5kg bag in preferred hand, one 3kg bag in preferred hand. Antero-posterior and medio-lateral displacement, and 95% ellipse area from a 30s quiet standing were used for postural stability assessment. Stride length and its coefficient of variation, total double support time, step asymmetry and gait stability ratio were calculated from 1min treadmill walking at self-selected speed for gait assessment. Carrying shopping bags did not negatively affect postural stability or gait variables, in either group. Further, in older individuals, a decrease in sway velocity was found when holding bags during the postural stability assessment (psocial and as a physical activity.
Effect of Heat Treatment upon Dimensional Stability and Static Bending Strength of Sessile Oak Wood
Alin OLARESCU
2011-06-01
Full Text Available The paper presents the results of an experimentalstudy performed with sessile oak wood (Quercuspetrea L.. After drying and conditioning at 12%MC,the test pieces were heat-treated at three differenthigh temperatures (120, 130 and 140°C for 1h, 2hand 3h. After the treatment and cooling, standardsamples for physical and mechanical tests were cut,in order to determine comparatively the density, thedimensional stability, the static bending strength andMOE of the differently treated samples.Based on the obtained results, the optimumtreatment schedule was established, namely the onewhich enables improved dimensional stability withoutaffecting significantly the wood strength. Theseresults can be applied at the manufacturing of solidwood panels with improved dimensional stabilityusing heat-treated wood lamellas.
Lytra, Alkmini; Pelekasis, Nikos, E-mail: pel@uth.gr [Department of Mechanical Engineering, University of Thessaly, Pedion Areos, Volos 38334 (Greece)
2014-08-01
The static response of a coated microbubble subject to an external pressure distribution is investigated, in order to identify different response patterns with varying viscoelastic properties of the shell. Theoretical and numerical analysis of the axisymmetric response of a microbubble is performed via the static force balance, in order to obtain the radial and tangential (polar) displacements of a shell subject to a uniform or point load. The stretching and bending stiffnesses of the shell, along with the compressibility of the internal gas, comprise the resistance to deformation of the microbubble. The finite element methodology, with B-splines as basis functions, is employed for the solution of the nonlinear static problem while Newton’s iterations provide the converged solution. The Jacobian matrix provides necessary information regarding stability of the emerging static configurations. The buckling instability of a uniformly loaded shell results in a subcritical bifurcation that is characterized by symmetric/asymmetric shapes for the parameter range pertaining to polymeric/phospholipid shells. As the relative importance of bending stiffness with respect to stretching decreases symmetric shapes determine the primary buckling instability. Strain softening shell behavior conforms to this pattern due to the increase of the effective area dilatation modulus during compression. Increasing the resistance to compression forces the asymmetric and symmetric solution families to terminate at larger bubble volumes. When a point load is considered the force deformation curve is characterized by a transition from a linear Reissner-type to a nonlinear Pogorelov-type response, followed by a regime where resistance to compression dominates. Identifying these regimes in atomic force microscopy measurements can be used for estimating the area dilatation and bending modulus of the shell. (paper)
On the stability of Einstein static universe in doubly general relativity scenario
Khodadi, M., E-mail: m.khodadi@stu.umz.ac.ir [Department of Physics, Faculty of Basic Sciences, University of Mazandaran, P. O. Box 47416-95447, Babolsar (Iran, Islamic Republic of); Heydarzade, Y., E-mail: heydarzade@azaruniv.edu [Department of Physics, Azarbaijan Shahid Madani University, 53714-161, Tabriz (Iran, Islamic Republic of); Nozari, K., E-mail: knozari@umz.ac.ir [Department of Physics, Faculty of Basic Sciences, University of Mazandaran, P. O. Box 47416-95447, Babolsar (Iran, Islamic Republic of); Darabi, F., E-mail: f.darabi@azaruniv.edu [Department of Physics, Azarbaijan Shahid Madani University, 53714-161, Tabriz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), 55134-441, Maragha (Iran, Islamic Republic of)
2015-12-12
By presenting a relation between the average energy of the ensemble of probe photons and the energy density of the universe, in the context of gravity’s rainbow or the doubly general relativity scenario, we introduce a rainbow FRW universe model. By analyzing the fixed points in the flat FRW model modified by two well-known rainbow functions, we find that the finite time singularity avoidance (i.e. Big Bang) may still remain as a problem. Then we follow the “emergent universe” scenario in which there is no beginning of time and consequently there is no Big-Bang singularity. Moreover, we study the impact of high energy quantum gravity modifications related to the gravity’s rainbow on the stability conditions of an “Einstein static universe” (ESU). We find that independent of the particular rainbow function, the positive energy condition dictates a positive spatial curvature for the universe. In fact, without raising a nonphysical energy condition in the quantum gravity regimes, we can observe agreement between gravity’s rainbow scenario and the basic assumption of the modern version of the “emergent universe”. We show that in the absence and presence of an energy-dependent cosmological constant Λ(ϵ), a stable Einstein static solution is available versus the homogeneous and linear scalar perturbations under the variety of the obtained conditions. Also, we explore the stability of ESU against the vector and tensor perturbations.
Rosselló, Juan Manuel; Dellavale, Damián; Bonetto, Fabián José
2013-09-01
In this study we report several experimental and numerical results on the influence of static pressure (P_{0}) over the main parameters in single bubble sonoluminescence (SBSL), using a sulfuric acid aqueous solution (SA) with low concentrations of argon gas dissolved. Bifrequency driving was used in the experiments to enhance spatial stability of the bubbles. The experimental results were compared with simulations provided by a numerical code that models the radial dynamics of the bubbles. The results showed that an increase on the static pressure of the system shifts the Bjerknes instability threshold, allowing the bubble to access higher acoustic pressures (P_{Ac}^{}). Furthermore, a decrease in the measured ambient radius R_{0} and the calculated relative gas concentration c_{∞}/c_{0} were observed. A notorious increment in the bubble collapse violence and energy focusing for P_{0} above 1 bar was achieved. These were mainly indicated by the growth of the bubble expansion ratio (R_{max}/R_{0}), the bubble mechanical energy density, and the maximum bubble wall velocity dR/dt. In agreement with the previous statement, the maximum temperature during the bubble collapse predicted by the model is augmented as well. The use of different harmonics in the ultrasound pressure field regarding energy focusing is also discussed. Finally, we analyzed the stability regions of the R_{0}-P_{Ac}^{} parameter space via numerical predictions for P_{0} above the measured, identifying the shape instabilities as the main limiting agent to obtain further energy concentration in SA systems at high static pressures.
Co-relationship of physical stability of amorphous dispersions with enthalpy relaxation.
Bansal, S S; Kaushal, A M; Bansal, A K
2008-11-01
Physical stability studies of valdecoxib (VLB) and its solid dispersions with PVP (1, 2, 5, 10, 15 and 20% w/w) were carried out by Differential Scanning Calorimetry (DSC). Change in specific heat with time was measured to determine the degree of crystallinity of amorphous drug and its binary dispersions after storage at 40 degrees C and 75% RH. The rate of crystallization was found to decrease with increasing PVP concentration and time for 10% crystallization (t90%) was found to increase significantly for the amorphous drug when formulated as PVP dispersions. Enthalpy relaxation was found to be inversely correlated with t90% (min) values and was found to be a good predictor of devitrification tendency and hence stability of amorphous VLB.
A Stabilized Incompressible SPH Method by Relaxing the Density Invariance Condition
Mitsuteru Asai
2012-01-01
Full Text Available A stabilized Incompressible Smoothed Particle Hydrodynamics (ISPH is proposed to simulate free surface flow problems. In the ISPH, pressure is evaluated by solving pressure Poisson equation using a semi-implicit algorithm based on the projection method. Even if the pressure is evaluated implicitly, the unrealistic pressure fluctuations cannot be eliminated. In order to overcome this problem, there are several improvements. One is small compressibility approach, and the other is introduction of two kinds of pressure Poisson equation related to velocity divergence-free and density invariance conditions, respectively. In this paper, a stabilized formulation, which was originally proposed in the framework of Moving Particle Semi-implicit (MPS method, is applied to ISPH in order to relax the density invariance condition. This formulation leads to a new pressure Poisson equation with a relaxation coefficient, which can be estimated by a preanalysis calculation. The efficiency of the proposed formulation is tested by a couple of numerical examples of dam-breaking problem, and its effects are discussed by using several resolution models with different particle initial distances. Also, the effect of eddy viscosity is briefly discussed in this paper.
Smith, David A
2014-08-21
The filament lattice in relaxed striated muscle is thought to be stabilized by electrostatic forces between charged filaments; electrostatic theories based on known filament charge densities do predict that the lattice spacing drops slightly with sarcomere length when actin and myosin filaments overlap. However, at sarcomere lengths with no overlap, electrostatic forces are reduced to a very low level and electrostatic models predict that the lattice collapses to a much smaller spacing. This collapse is not observed, which suggests that the A-band and I-band lattices are stabilized mechanically by the M-band and Z-line. To determine which mechanisms operate, consider a model where charged-filament interactions are supplemented by elastic titin filaments and radially elastic M-bands and Z-lines. To make progress, this model is simplified by assuming that the areas of A-band and Z-line unit cells are equal. Published data for the length-dependence of the lattice spacing, in and out of overlap, can be fitted to a mechanical model with known titin elasticity and very weak M-band or Z-line stiffness (≈0.15 pN/nm per unit cell), which implies that electrostatic interactions cannot be ignored. A better fit is obtained when electrostatic interactions are restored. Electrostatic interactions also explain why the lattice spacing of relaxed muscle is a decreasing function of temperature.
Sertsou, Gabriel; Butler, James; Hempenstall, John; Rades, Thomas
2003-01-01
The poorly water-soluble drug GWX was co-precipitated with hydroxypropyl methylcellulose phthalate (HPMCP) using a solvent change method. The two co-precipitate formulations made, with drug-HPMCP ratios of 2:8 and 5:5, were analysed using modulated temperature differential scanning calorimetry. They were found to consist of completely amorphous solid solution and a mixture of amorphous solid solution, crystalline drug and amorphous drug, respectively. Stability with respect to crystallization of the two co-precipitates and pure amorphous drug made by quench cooling was compared by storing preparations at 25 degrees C and 40 degrees C, under vacuum over P(2)O(5), and at 75% relative humidity (r.h.). Humidity (75% r.h. compared with dry) had a larger influence on crystallization of the amorphous drug than temperature (25 degrees C compared with 40 degrees C). The solid solution phase in co-precipitates had a relatively higher stability than amorphous drug alone, with respect to crystallization, in presence of the plasticizer water, and crystalline drug. These findings were partly explained by evidence of decreased molecular mobility in the amorphous solid solution with respect to amorphous drug alone, using enthalpy relaxation measurements. At an ageing temperature of 65 degrees C, the calculated half-life for enthalpy relaxation of the 2:8 drug-HPMCP ratio coprecipitate was about 6 orders of magnitude greater than that of amorphous drug alone, indicating a large difference in relative molecular mobility.
Inter-Area Power Systems Stability Improvement by Static Synchronous Series Compensator
Prechanon Kumkratug
2011-01-01
Full Text Available Problem statement: The inter-area power systems have special characteristic of the stability behavior. The improvement of inter-area power system is one of the important aspects in power system. Approach: This study applies the Static Synchronous Series Compensator (SSSC to improve stability of inter-area systems. The SSSC is modeled and then is applied to be incorporated into the power system model for investigating stability improvement. The SSSC is modeled as the variable susceptance and is controlled during dynamic state. This presented SSSC model can be incorporated into susceptance matrix of power system model. The presented method is tested on sample inter-area power system with 3 phase fault distubrances. Results: The swing curve of inter-area power system without a SSSC gets increases monotonically and thus the system can be considered as unstable whereas the swing curves of system with a SSSC can be considered as stable. Conclusion: From the simulation results, the SSSC can enhance stability of inter-area power systems.
Keynton, Robert J.
1961-01-01
Tests were conducted at Mach numbers of 3.96 and 4.65 in the Langley Unitary Plan wind tunnel to determine the static longitudinal stability characteristics of a fin-stabilized rocket-vehicle configuration which had a rearward facing step located upstream of the fins. Two fin sizes and planforms, a delta and a clipped delta, were tested. The angle of attack was varied from 6 deg to -6 deg and the Reynolds number based on model 6 length was about 10 x 10. The configuration with the larger fins (clipped delta) had a center of pressure slightly rearward of and an initial normal-force-curve slope slightly higher than that of the configuration with the smaller fins (delta) as would be expected. Calculations of the stability parameters gave a slightly lower initial slope of the normal-force curve than measured data, probably because of boundary-layer separation ahead of the step. The calculated center of pressure agreed well with the measured data. Measured and calculated increments in the initial slope of the normal-force curve and in the center of pressure, due to changing fins, were in excellent agreement indicating that separated flow downstream of the step did not influence flow over the fins. This result was consistent with data from schlieren photographs.
Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves.
Meissner, Matthias; Sojka, Falko; Matthes, Lars; Bechstedt, Friedhelm; Feng, Xinliang; Müllen, Klaus; Mannsfeld, Stefan C B; Forker, Roman; Fritz, Torsten
2016-07-26
The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate-substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases. Using low-energy electron diffraction and scanning tunneling microscopy, we provide direct experimental evidence for SDWs in organic adsorbate films, namely hexa-peri-hexabenzocoronene on graphite. They manifest as wave-like sub-Ångström molecular displacements away from an ideal adsorbate lattice which is incommensurate with graphite. By means of a density-functional-theory based model, we show that, due to the flexibility in the adsorbate layer, molecule-substrate energy is gained by straining the intermolecular bonds and that the resulting total energy is minimal for the observed domain orientation, constituting the orientational epitaxy. While structural relaxation at an interface is a common assumption, the combination of the precise determination of the incommensurate epitaxial relation, the direct observation of SDWs in real space, and their identification as the sole source of epitaxial energy gain constitutes a comprehensive proof of this effect.
Static and dynamic stability analysis using 3D-DDA with incision body scheme
Wang Jianquan; Lin Gao; Liu Jun
2006-01-01
Discontinuous deformation analysis (DDA) provides a powerful numerical tool for the analysis of discontinuous media. This method has been widely applied to the 2D analysis of discontinuous deformation. However, it is hindered from analyzing 3D rock engineering problems mainly due to the lack of reliable 3D contact detection algorithms for polyhedra.Contact detection is a key in 3-D DDA analysis. The limitations and advantages of existing contact detection schemes are discussed in this paper, and a new approach, called the incision body (IB), is proposed, taking into account the advantages of the existing methods. A computer code 3DIB, which uses the IB scheme as a 3D contact detection algorithm, was programmed with Visual C++. Static and dynamic stability analysis for three realistic engineering problems has been carried out. Furthermore, the focus is on studying the stability of a gravity dam on jointed rock foundation and dynamic stability of a fractured gravity dam subject to earthquake shaking. The simulation results show that the program 3DIB and incision body scheme are capable of detecting 3D block contacts correctly and hence simulating the open-close and slide process of jointed block masses. In addition, the code 3DIB could provide an effective tool for evaluating the safety of 3D dam structures, which is quite important for engineering problems.
Influencing Power Flow and Transient Stability by Static Synchronous Series Compensator
Md. Imran Azim
2015-04-01
Full Text Available In the present world, modern power system networks, being a complicated combination of generators, transmission lines, transformers, circuit breakers and other devices, are more vulnerable to various types of faults causing stability problems. Among these faults, transient fault is believed to be a major disturbance as it causes large damage to a sound system within a certain period of time. Therefore, the protection against transient faults, better known as transient stability control is one of the major considerations for the power system engineers. This paper presents the control approach in the transmission line during transient faults by means of Static Synchronous Series Compensator (SSSC in order to stabilize Single Machine Infinite Bus (SMIB system. In this paper, SSSC is represented by variable voltage injection associated with the transformer leakage reactance and the voltage source. The comparative results depict that the swing curve of a system increases monotonically after the occurrence of transient faults However, SSSC is effective enough to make it stable after a while.
Stability of the Einstein static Universe in $f(R,T)$ gravity
Shabani, Hamid
2016-01-01
The Einstein static (ES) universe has played a major role in various emergent scenarios recently proposed in order to cure the problem of initial singularity of the standard model of cosmology. In the herein model, we study the existence and stability of ES universe in the context of $f(R,T)$ modified theories of gravity. Considering specific forms of $f(R,T)$ function, we seek for the existence of solutions representing ES state. Using dynamical system techniques along with numerical analysis, we find two classes of solutions: the first one is always unstable of the saddle type while the second is always stable so that its dynamical behavior corresponds to a center equilibrium point. The importance of the second class of solutions is due to the significant duty they have in constructing non-singular emergent models in which the universe could have experienced past-eternally, a series of infinite oscillations about such an initial static state after which, it enters through a suitable physical mechanism, to a...
Analysis of stability of a Power System by using Delay Static State Feedback
Sindy Paola Amaya
2012-12-01
Full Text Available This article presents the analysis of stability of a power system modeled as Infinite Bus Connected Generator with delay static state feedback. The model of the power system is described by nonlinear differential- algebraic equations. For controller design, we linealize the nonlinear differential-algebraic model around an operation point to obtain a lineal differential-algebraic model. As of this model obtains the Kronecker -Weierstrass model which designs the controller. To obtain the K gain of the controller outline inequalities matrix lineal (LMI's . Then it makes a study of the maximum delay that it supports in the state feedback. At the end of the article present the results and the conclusions.
Simoes Costa, A.J.A.; Silva, A.S.; Freitas, F.D. [Santa Catarina Univ., Florianopolis, SC (Brazil). Dept. de Engenharia Eletrica
1994-12-31
Two distinct approaches for the coordinated setting of multimachine power system controllers are presented. The first strategy is based on the re-allocation of the poles related to the electromechanical modes of the system through decentralized control. The second method is a coordinated global procedure based on structurally constrained optimal control. Both approaches considered power system stabilizers and supplementary signals for static var compensators as the controllers to be adjusted. Other types of controllers, such as FACTS devices, can also be tuned by using the proposed techniques. A 13-machine, 77-bus power system which is based on the Brazilian South-Southeast interconnected network is employed to assess the performance of the proposed methods. (author) 14 refs., 1 fig., 7 tabs.
On the stability of Einstein static universe in doubly general relativity scenario
Khodadi, M.; Nozari, K. [University of Mazandaran, Department of Physics, Faculty of Basic Sciences, Babolsar (Iran, Islamic Republic of); Heydarzade, Y. [Azarbaijan Shahid Madani University, Department of Physics, Tabriz (Iran, Islamic Republic of); Darabi, F. [Azarbaijan Shahid Madani University, Department of Physics, Tabriz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of)
2015-12-15
By presenting a relation between the average energy of the ensemble of probe photons and the energy density of the universe, in the context of gravity's rainbow or the doubly general relativity scenario, we introduce a rainbow FRW universe model. By analyzing the fixed points in the flat FRW model modified by two well-known rainbow functions, we find that the finite time singularity avoidance (i.e. Big Bang) may still remain as a problem. Then we follow the ''emergent universe'' scenario in which there is no beginning of time and consequently there is no Big-Bang singularity. Moreover, we study the impact of high energy quantum gravity modifications related to the gravity's rainbow on the stability conditions of an ''Einstein static universe'' (ESU). We find that independent of the particular rainbow function, the positive energy condition dictates a positive spatial curvature for the universe. In fact, without raising a nonphysical energy condition in the quantum gravity regimes, we can observe agreement between gravity's rainbow scenario and the basic assumption of the modern version of the ''emergent universe''. We show that in the absence and presence of an energy-dependent cosmological constant Λ(ε), a stable Einstein static solution is available versus the homogeneous and linear scalar perturbations under the variety of the obtained conditions. Also, we explore the stability of ESU against the vector and tensor perturbations. (orig.)
Stability of the Einstein static universe in f(R, T) gravity
Shabani, Hamid [University of Sistan and Baluchestan, Physics Department, Faculty of Sciences, Zahedan (Iran, Islamic Republic of); Ziaie, Amir Hadi [Kahnooj Branch, Islamic Azad University, Department of Physics, Kerman (Iran, Islamic Republic of)
2017-01-15
The Einstein static (ES) universe has played a major role in various emergent scenarios recently proposed in order to cure the problem of the initial singularity of the standard model of cosmology. In the model we address, we study the existence and stability of an ES universe in the context of f(R, T) modified theories of gravity. Considering specific forms of the f(R, T) function, we seek for the existence of solutions representing ES state. Using dynamical system techniques along with numerical analysis, we find two classes of solutions: the first one is always unstable of the saddle type, while the second is always stable so that its dynamical behavior corresponds to a center equilibrium point. The importance of the second class of solutions is due to the significant role they play in constructing non-singular emergent models in which the universe could have experienced past-eternally a series of infinite oscillations about such an initial static state after which it enters, through a suitable physical mechanism, to an inflationary era. Considering specific forms for the functionality of f(R, T), we show that this theory is capable of providing cosmological solutions which admit emergent universe (EU) scenarios. We also investigate homogeneous scalar perturbations for the mentioned models. The stability regions of the solutions are parametrized by a linear equation of state (EoS) parameter and other free parameters that will be introduced for the models. Our results suggest that modifications in f(R, T) gravity would lead to stable solutions which are unstable in f(R) gravity model. (orig.)
Park, San-Seong; Choi, Bo-Ram
2016-06-01
[Purpose] This study evaluated the differences in the flexion-relaxation phenomenon (FRP) of the right and left erector spinae muscles in asymptomatic subjects and the effect of lumbar stabilization exercises on these differences. [Subjects and Methods] Twenty-six participants (12 in the exercise group and 14 in the control group) with a difference in the FRP in the right and left erector spinae muscles were recruited from among healthy students attending Silla University. The exercise group performed two lumbar stabilization exercises (back bridge exercise and hand-knee exercise) for 4 weeks. The control group did not exercise. [Results] No significant group-by-exercise interaction was found. The right and left erector spinae muscles did show a difference in FRP between the control and exercise groups (119.2 ± 69.2 and 131.1 ± 85.2 ms, respectively). In addition, the exercise group showed a significant decrease in post-exercise (50.0 ± 27.0 ms) compared to pre-exercise (112.3 ± 41.5 ms) differences in the right and left FRP. [Conclusion] These results suggest that lumbar stabilization exercises may counter asymmetry of the FRP in the erector spinae muscles, possibly preventing low back pain in the general population.
Holm, Jeppe; Dasmeh, Pouria; Kepp, Kasper P
2016-07-01
The evolution of cetaceans (whales, dolphins, and porpoises) from land to water is one of the most spectacular events in mammal evolution. It has been suggested that selection for higher myoglobin stability (∆G of folding) allowed whales to conquer the deep-diving niche. The stability of multi-site protein variants, including ancient proteins, is however hard to describe theoretically. From a compilation of experimental ∆∆G vs. ∆G we first find that protein substitutions are subject to large generic protein relaxation effects. Using this discovery, we develop a simple two-parameter model that predicts multi-site ∆∆G as accurately as standard methods do for single-site mutations and reproduces trends in contemporary myoglobin stabilities. We then apply this new method to the study of the evolution of Mb stability in cetaceans: With both methods the main change in stability (about 1kcal/mol) occurred very early, and stability was later relaxed in dolphins and porpoises, but was further increased in the sperm whales. This suggests that single proteins can affect whole organism evolution and indicates a role of Mb stability in the evolution of cetaceans. Transition to the deep-diving niche probably occurred already in the ancestor of contemporary baleen and toothed whales. In summary, we have discovered generic stability relaxation effects in proteins that, when incorporated into a simple model, improves the description of multi-site protein variants.
Effect of a static external magnetic perturbation on resistive mode stability in tokamaks
Fitzpatrick, R. [Univ. of Texas, Austin, TX (United States). Institute for Fusion Studies; Hender, T.C. [Univ. of Texas, Austin, TX (United States). Institute for Fusion Studies]|[Culham Lab., Abingdon (United Kingdom)
1994-03-01
The influence of a general static external magnetic perturbation on the stability of resistive modes in a tokamak plasma is examined. There are three main parts to this investigation. Firstly, the vacuum perturbation is expanded as a set of well-behaved toroidal ring functions and is, thereafter, specified by the coefficients of this expansion. Secondly, a dispersion relation is derived for resistive plasma instabilities in the presence of a general external perturbation and finally, this dispersion relation is solved for the amplitudes of the tearing and twisting modes driven in the plasma by a specific perturbation. It is found that the amplitudes of driven tearing and twisting modes are negligible until a certain critical perturbation strength is exceeded. Only tearing modes are driven in low-{beta} plasmas with {epsilon}{beta}{sub p} << 1. However, twisting modes may also be driven if {epsilon}{beta}{sub p}{approx}>1. For error-field perturbations made up of a large number of different poloidal and toroidal harmonics the critical strength to drive locked modes has a {open_quote}staircase{close_quote} variation with edge-q, characterized by strong discontinuities as coupled rational surfaces enter or leave the plasma. For single harmonic perturbations the variation with edge-q is far smoother. Both types of behaviour have been observed experimentally. The critical perturbation strength is found to decrease strongly close to an ideal external kink stability boundary. This is also in agreement with experimental observations.
Prechanon Kumkratug
2011-01-01
Full Text Available Problem statement: Modern power system consists of the complicated network of transmission lines and carries heavy demand. Thus they cause in the stability problem. Approach: Static Synchronous Series Compensator (SSSC is a power electronic based device that has the capability of controlling the power flow through a line. The series voltage injection model of SSSC is modeled into power flow equation and thus it is used to determine its control strategy. This study applies the fuzzy logic applies the SSSC to improve stability of power system. The mathematical model and control strategy of a SSSC are presented. The SSSC is represented by variable voltage injection with associate transformer leakage control to derive control strategy of SSSC. The swing curves of the three phase faulted power system without and with a SSSC is tested and compared in various cases. Results: The swing curve of the system with SSSC based fuzzy logic control has the less amplitude during the dynamic period. Conclusion: It was found from simulation results that SSSC can improve the power system oscillation after disturbance.
Ohta, Michihiro; Kirimoto, Kenta; Nobugai, Kohji; Wigmore, J. Keith; Miyasato, Tatsuro
2001-09-01
The internal friction in single crystal yttria-stabilized zirconia (YSZ) doped with 9.5 mol% Y2O3 was measured for longitudinal sound waves in the frequency range from 10 Hz to 800 Hz using a vibrating reed technique. In the temperature range from 300 K to 700 K, observations of internal friction reveal two closely overlapping absorption peaks, confirming the existence of two relaxation modes in YSZ@. One of the peaks is due to diffusion relaxation, which is known to be responsible for long-range transport of O-ions. The second peak shows clearly the existence of localized relaxation, which is attributed to bound oxygen vacancies within the local structure which is formed around an Y-ion due to symmetry breaking. The absorption peak caused by the localized relaxation exhibits anisotropy resulting from the asymmetric local structure, and the strength of this peak changes with temperature reflecting the number of bound oxygen vacancies.
Static Stability Analysis of a Planar Object Grasped by Multifingers with Three Joints
Takayoshi Yamada
2015-11-01
Full Text Available This paper discusses static stability of a planar object grasped by multifingers with three joints. Each individual joint (prismatic joint or revolute joint is modeled as a linear spring stiffness. The object mass and the link masses are also included. We consider not only pure rolling contact but also frictionless sliding contact. The grasp stability is investigated using the potential energy method. This paper makes the following contributions: (i Grasp wrench vectors and grasp stiffness matrices are analytically derived not only for the rolling contact but also for the sliding contact; (ii It is shown in detail that the vectors and the matrices are given by functions of grasp parameters such as the contact conditions (rolling contact and sliding contact, the contact position, the contact force, the local curvature, the link shape, the object mass, the link masses, and so on; (iii By using positive definiteness of the difference matrix of the grasp stiffness matrices, it is analytically proved that the rolling contact grasp is more stable than the sliding contact grasp. The displacement direction affected by the contact condition deviation is derived; (iv By using positive definiteness of the differential matrix with respect to the local curvatures, it is analytically proved that the grasp stability increases when the local curvatures decrease. The displacement direction affected by the local curvature deviation is also derived; (v Effects of the object mass and the joint positions are discussed using numerical examples. The numerical results are reinforced by analytical explanations. The effect of the link masses is also investigated.
Superhydrophobic stability of nanotube array surfaces under impact and static forces.
Zhu, Lin; Shi, Pan; Xue, Jian; Wang, Yuanyi; Chen, Qingmin; Ding, Jianfu; Wang, Qingjun
2014-06-11
The surfaces of nanotube arrays were coated with poly(methyl methacrylate) (PMMA) using an imprinting method with an anodized alumina membrane as the template. The prepared nanotube array surfaces then either remained untreated or were coated with NH2(CH2)3Si(OCH3)3(PDNS) or CF3(CF2)7CH2CH2Si(OC2H5)3 (PFO). Thus, nanotube arrays with three different surfaces, PDNS, PMMA (without coating), and PFO, were obtained. All three surfaces (PDNS, PMMA, and PFO) exhibited superhydrophobic properties with contact angles (CA) of 155, 166, and 168°, respectively, and their intrinsic water contact angles were 30, 79, and 118°, respectively. The superhydrophobic stabilities of these three surfaces were examined under dynamic impact and static pressures in terms of the transition from the Cassie-Baxter mode to the Wenzel mode. This transition was determined by the maximum pressure (p(max)), which is dependent on the intrinsic contact angle and the nanotube density of the surface. A p(max) greater than 10 kPa, which is sufficiently large to maintain stable superhydrophobicity under extreme weather conditions, such as in heavy rain, was expected from the PFO surface. Interestingly, the PDNS surface, with an intrinsic CA of only 30°, also displayed superhydrophobicity, with a CA of 155°. This property was partially maintained under the dynamic impact and static pressure tests. However, under an extremely high pressure (0.5 MPa), all three surfaces transitioned from the Cassie-Baxter mode to the Wenzel mode. Furthermore, the lost superhydrophobicity could not be recovered by simply relieving the pressure. This result indicates that the best way to maintain superhydrophobicity is to increase the p(max) of the surface to a value higher than the applied external pressure by using low surface energy materials and having high-density binary nano-/microstructures on the surface.
Holm, Jeppe; Dasmeh, Pouria; Kepp, Kasper Planeta
2016-01-01
The evolution of cetaceans (whales, dolphins, and porpoises) from land to water is one of the most spectacular events in mammal evolution. It has been suggested that selection for higher myoglobin stability (ΔG of folding) allowed whales to conquer the deep-diving niche. The stability of multi...... that predicts multi-site ΔΔG as accurately as standard methods do for single-site mutations and reproduces trends in contemporary myoglobin stabilities. We then apply this new method to the study of the evolution of Mb stability in cetaceans: With both methods the main change in stability (about 1 kcal....../mol) occurred very early, and stability was later relaxed in dolphins and porpoises, but was further increased in the sperm whales. This suggests that single proteins can affect whole organism evolution and indicates a role of Mb stability in the evolution of cetaceans. Transition to the deep-diving niche...
Y. Tomikawa
2010-08-01
Full Text Available An analysis of the static stability and ozone vertical gradient in the ozone tropopause based (OTB coordinate is applied to the ozonesonde data at 10 stations in the Southern Hemisphere (SH extratropics. The tropopause inversion layer (TIL with a static stability maximum just above the tropopause shows similar seasonal variations at two Antarctic stations, which are latitudinally far from each other. Since the sunshine hour varies with time in a quite different way between these two stations, it implies that the radiative heating due to solar ultraviolet absorption of ozone does not contribute to the seasonal variation of the TIL. A meridional section of the static stability in the OTB coordinate shows that the static stability just above the tropopause has a large latitudinal gradient between 60° S and 70° S in austral winter because of the absence of the TIL over the Antarctic. It is accompanied by an increase of westerly shear with height above the tropopause, so that the polar-night jet is formed above this latitude region. This result suggests a close relationship between the absence of the TIL and the stratospheric polar vortex in the Antarctic winter. A vertical gradient of ozone mixing ratio, referred to as ozone vertical gradient, around the tropopause shows similar latitudinal and seasonal variations with the static stability in the SH extratropics. In a height region above the TIL, a small ozone vertical gradient in the midlatitudes associated with the Antarctic ozone hole is observed in a height region of the subvortex but not around the polar vortex. This is a clear evidence of active latitudinal mixing between the midlatitudes and subvortex.
Sung-Chih Hsieh
2015-01-01
Full Text Available One of the causes of dental pulpitis is lipopolysaccharide- (LPS- induced inflammatory response. Following pulp tissue inflammation, odontoblasts, dental pulp cells (DPCs, and dental pulp stem cells (DPSCs will activate and repair damaged tissue to maintain homeostasis. However, when LPS infection is too serious, dental repair is impossible and disease may progress to irreversible pulpitis. Therefore, the aim of this study was to examine whether static magnetic field (SMF can attenuate inflammatory response of dental pulp cells challenged with LPS. In methodology, dental pulp cells were isolated from extracted teeth. The population of DPSCs in the cultured DPCs was identified by phenotypes and multilineage differentiation. The effects of 0.4 T SMF on DPCs were observed through MTT assay and fluorescent anisotropy assay. Our results showed that the SMF exposure had no effect on surface markers or multilineage differentiation capability. However, SMF exposure increases cell viability by 15%. In addition, SMF increased cell membrane rigidity which is directly related to higher fluorescent anisotropy. In the LPS-challenged condition, DPCs treated with SMF demonstrated a higher tolerance to LPS-induced inflammatory response when compared to untreated controls. According to these results, we suggest that 0.4 T SMF attenuates LPS-induced inflammatory response to DPCs by changing cell membrane stability.
Majumdar, Apala
2013-06-01
We analyze the dynamical stability of a naturally straight, inextensible and unshearable elastic rod, under tension and controlled end rotation, within the Kirchhoff model in three dimensions. The cases of clamped boundary conditions and isoperimetric constraints are treated separately. We obtain explicit criteria for the static stability of arbitrary extrema of a general quadratic strain energy. We exploit the equivalence between the total energy and a suitably defined norm to prove that local minimizers of the strain energy, under explicit hypotheses, are stable in the dynamic sense due to Liapounov. We also extend our analysis to damped systems to show that static equilibria are dynamically stable in the Liapounov sense, in the presence of a suitably defined local drag force. © 2013 Elsevier B.V. All rights reserved.
Mihet-Popa, Lucian; Groza, V.
2011-01-01
of the Smart Grids (SGs). A SG can operate interconnected to the main distribution grid or in islanded mode. This paper presents experimental tests for static and dynamic stability analysis carried out in a dedicated laboratory for research in distributed control and smart grid with a high share of renewable...... are required under different operation modes and loads. The testing reporting here includes three modes of operation: stand alone, parallel/hybrid and grid connection....
Ivashchuk, V D
2016-01-01
A (n+1)-dimensional gravitational model with Gauss-Bonnet term and cosmological constant term is considered. When ansatz with diagonal cosmological metrics is adopted, the solutions with exponential dependence of scale factors: a_i \\sim \\exp{ ( v^i t) }, i =1, ..., n, are analysed for n > 3. We study the stability of the solutions with non-static volume factor, i.e. if K(v) = \\sum_{k = 1}^{n} v^k \
Greathouse, James S.; Schwing, Alan M.
2015-01-01
This paper explores use of computational fluid dynamics to study the e?ect of geometric porosity on static stability and drag for NASA's Multi-Purpose Crew Vehicle main parachute. Both of these aerodynamic characteristics are of interest to in parachute design, and computational methods promise designers the ability to perform detailed parametric studies and other design iterations with a level of control previously unobtainable using ground or flight testing. The approach presented here uses a canopy structural analysis code to define the inflated parachute shapes on which structured computational grids are generated. These grids are used by the computational fluid dynamics code OVERFLOW and are modeled as rigid, impermeable bodies for this analysis. Comparisons to Apollo drop test data is shown as preliminary validation of the technique. Results include several parametric sweeps through design variables in order to better understand the trade between static stability and drag. Finally, designs that maximize static stability with a minimal loss in drag are suggested for further study in subscale ground and flight testing.
R. Kalaivani
2012-01-01
Full Text Available Problem statement: Voltage instability and voltage collapse have been considered as a major threat to present power system networks due to their stressed operation. It is very important to do the power system analysis with respect to voltage stability. Approach: Flexible AC Transmission System (FACTS is an alternating current transmission system incorporating power electronic-based and other static controllers to enhance controllability and increase power transfer capability. A FACTS device in a power system improves the voltage stability, reduces the power loss and also improves the load ability of the system. Results: This study investigates the application of Particle Swarm Optimization (PSO and Genetic Algorithm (GA to find optimal location and rated value of Static Var Compensator (SVC device to minimize the voltage stability index, total power loss, load voltage deviation, cost of generation and cost of FACTS devices to improve voltage stability in the power system. Optimal location and rated value of SVC device have been found in different loading scenario (115%, 125% and 150% of normal loading using PSO and GA. Conclusion/Recommendations: It is observed from the results that the voltage stability margin is improved, the voltage profile of the power system is increased, load voltage deviation is reduced and real power losses also reduced by optimally locating SVC device in the power system. The proposed algorithm is verified with the IEEE 14 bus, IEEE 30 bus and IEEE 57 bus.
Reale, Riccardo; English, Niall J; Garate, José-Antonio; Marracino, Paolo; Liberti, Micaela; Apollonio, Francesca
2013-11-28
Water self-diffusion and the dipolar response of the selectivity filter within human aquaporin 4 have been studied using molecular dynamics (MD) simulations in the absence and presence of pulses of external static and alternating electric fields. The pulses were approximately 50 and 100 ns in duration and 0.0065 V/Å in (r.m.s.) intensity and were either static or else 2.45 or 100 GHz in frequency and applied both along and perpendicular to the channels. In addition, the relaxation of the aquaporin, water self-diffusion and gating dynamics following cessation of the impulses was studied. In previous work it was determined that switches in the dihedral angle of the selectivity filter led to boosting of water permeation events within the channels, in the presence of identical external static and alternating electric fields, although applied continuously. Here the application of field impulses (and subsequently, upon removal) has shown that it is the dipolar orientation of the histidine-201 residue in the selectivity filter which governs the dihedral angle, and hence influences water self-diffusion; this constitutes an appropriate order parameter. The dipolar response of this residue to the applied field leads to the adoption of four distinct states, which we modelled as time-homogeneous Markov jump processes, and may be distinguished in the potential of mean force (PMF) as a function of the dipolar orientation of histidine-201. The observations of enhanced "dipolar flipping" of H201 serve to explain increased levels of water self-diffusion within aquaporin channels during, and immediately following, field impulses, although the level of statistical certainty here is lower. Given the appreciable size of the energy barriers evident in PMFs computed directly from deterministic MD (whether in the absence or presence of external fields), metadynamics calculations were undertaken to explore the free-energy landscape of histidine-201 orientation with greater accuracy and
Moul, Martin T.; Brown, Lawrence W.
1959-01-01
A preliminary theoretical investigation has been made of the short-period longitudinal and steady-rolling (inertia coupling) stability of a hypersonic glider configuration for center-of-gravity locations rear-ward of the airplane neutral point. Such center-of-gravity positions for subsonic flight would improve performance by reducing supersonic and hypersonic static margins and trim drag. Results are presented of stability calculations and a simulator study for a velocity of 700 ft/sec and an altitude of 401,000 feet. With no augmentation, the airplane was rapidly divergent and was considered unsatisfactory in the simulator study. When a pitch damper was employed as a stability augmenter, the short-period mode became overdamped, and the airplane was easily controlled on the simulator. A steady-rolling analysis showed that the airplane can be made free of rolling divergence for all roll rates with an appropriate damper gain.
Qiu, Hao; Mizutani, Tomoko; Saraya, Takuya; Hiramoto, Toshiro
2015-04-01
The commonly used four metrics for write stability were measured and compared based on the same set of 2048 (2k) six-transistor (6T) static random access memory (SRAM) cells by the 65 nm bulk technology. The preferred one should be effective for yield estimation and help predict edge of stability. Results have demonstrated that all metrics share the same worst SRAM cell. On the other hand, compared to butterfly curve with non-normality and write N-curve where no cell state flip happens, bit-line and word-line margins have good normality as well as almost perfect correlation. As a result, both bit line method and word line method prove themselves preferred write stability metrics.
Minodora Maria PASĂRE
2010-10-01
Full Text Available In these paper, starting from the relations for the displacements and spinning the transversal section of a bar with thin walls of sections opened expressed by the corresponding influence functions and introducing the components of the exterior forces distributed and the moments of the exterior forces distributed due to the inertia forces, the exciting axial forces together with the following effect of these and of the reaction forces of the elastic environment for leaning it may reach to the system of the equations of parametric vibrations under the form of three integral equation These equations may serve for the study of vibrations of the bars, to study the static stability and to study the dynamic stability
Jacobs, P. F.; Flechner, S. G.
1976-01-01
A baseline wing and a version of the same wing fitted with winglets were tested. The longitudinal aerodynamic characteristics were determined through an angle-of-attack range from -1 deg to 10 deg at an angle of sideslip of 0 deg for Mach numbers of 0.750, 0.800, and 0.825. The lateral aerodynamic characteristics were determined through the same angle-of-attack range at fixed sideslip angles of 2.5 deg and 5 deg. Both configurations were investigated at Reynolds numbers of 13,000,000, per meter (4,000,000 per foot) and approximately 20,000,000 per meter (6,000,000 per foot). The winglet configuration showed slight increases over the baseline wing in static longitudinal and lateral aerodynamic stability throughout the test Mach number range for a model design lift coefficient of 0.53. Reynolds number variation had very little effect on stability.
Relaxation dynamics of glasses along a wide stability and temperature range
Rodríguez-Tinoco, C.; Ràfols-Ribé, J.; González-Silveira, M.; Rodríguez-Viejo, J.
2016-10-01
While lots of measurements describe the relaxation dynamics of the liquid state, experimental data of the glass dynamics at high temperatures are much scarcer. We use ultrafast scanning calorimetry to expand the timescales of the glass to much shorter values than previously achieved. Our data show that the relaxation time of glasses follows a super-Arrhenius behaviour in the high-temperature regime above the conventional devitrification temperature heating at 10 K/min. The liquid and glass states can be described by a common VFT-like expression that solely depends on temperature and limiting fictive temperature. We apply this common description to nearly-isotropic glasses of indomethacin, toluene and to recent data on metallic glasses. We also show that the dynamics of indomethacin glasses obey density scaling laws originally derived for the liquid. This work provides a strong connection between the dynamics of the equilibrium supercooled liquid and non-equilibrium glassy states.
Maeda, Noriaki; Urabe, Yukio; Tsutsumi, Shogo; Numano, Shuhei; Morita, Miho; Takeuchi, Takuya; Iwata, Shou; Kobayashi, Toshiki
2016-01-01
Ankle braces have been suggested to protect ankle joints from a sprain by restricting inversion and improving proprioception. However, the difference in effects between a semi-rigid brace and a soft brace regarding dynamic postural control after landing is not known. The aim of the present study was to compare the effect of soft (SB) and semi-rigid (SRB) ankle braces on static and dynamic postural stability in healthy young men. Altogether, 21 male adults (mean age 24.0 ± 1.5 years) were assessed for one leg while wearing non-brace (NB), SB or SRB. Balance in single-limb stance on a single-force platform with open eyes and closed eyes were assessed for the non-dominant leg under SB, SRB, and NB conditions. Locus length/second (mm/s) and the enveloped area (mm·s-2) surrounded by the circumference of the wave pattern during postural sway were calculated. For assessing dynamic postural stability, the participant jumped and landed on one leg on a force platform, and the Dynamic Postural Stability Index (DPSI) and the maximum vertical ground reaction force (vGRFmax) were measured. The data were compared among the three conditions with repeated-measures analysis of variance. The correlations between locus length/second, enveloped area, DPSI values (DPSI, Anterior-Posterior Stability Index, Medial-Lateral Stability Index, and Vertical Stability Index), and vGRFmax were then calculated. The results indicated that locus length/second and enveloped area with open eyes and closed eyes were not significantly different for each condition. However, a significant lower in the DPSI and Vertical Stability Index were observed with the SRB in comparison to the SB and NB. A significant improvement in vGRFmax was also observed with the SRB in comparison to NB. SRB demonstrated a positive effect on dynamic postural stability after landing on a single leg and may improve balance by increasing dynamic postural stability. Key points This study examined the effect of ankle braces on
stability analysis of static slip-energy recovery drive via eigenvalue ...
Dr Obe
drive system is almost completely stable in the entire operating range. Routh stability criterion ... Electromagnetic torque developed. Tl load torque. Xf .... average output voltage of a three-phase full-wave uncontrolled rectifier bridge is;. √. (5).
Static and Dynamic Experimental Analysis of the Galloping Stability of Porous H-Section Beams
F. Gandia
2014-01-01
Full Text Available The phenomenon of self-induced vibrations of prismatic beams in a cross-flow has been studied for decades, but it is still of great interest due to their important effects in many different industrial applications. This paper presents the experimental study developed on a prismatic beam with H-section. The aim of this analysis is to add some additional insight into the behaviour of the flow around this type of bodies, in order to reduce galloping and even to avoid it. The influence of some relevant geometrical parameters that define the H-section on the translational galloping behaviour of these beams has been analysed. Wind loads coefficients have been measured through static wind tunnel tests and the Den Hartog criterion applied to elucidate the influence of geometrical parameters on the galloping properties of the bodies under consideration. These results have been completed with surface pressure distribution measurements and, besides, dynamic tests have been also performed to verify the static criterion. Finally, the morphology of the flow past the tested bodies has been visualised by using smoke visualization techniques. Since the rectangular section beam is a limiting case of the H-section configuration, the results here obtained are compared with the ones published in the literature concerning rectangular configurations; the agreement is satisfactory.
An Adaptive Power System Stability Enhancement Using Static Synchronous Series Compensator (SSSC
Nagarjun Donipala,
2014-01-01
Full Text Available In this research we are investigate the controlling and enhancing or modulation power flow in a transmission line using a static synchronous series compensator (SSSC. At present studies it include detailed PWM techniques controlled for SSSC, are conducted in control circuits. In this proposed technique we are study a static synchronous series compensator is used to investigate the device in controlling active and reactive power as well as damping power system oscillations in th transient mode. This SSSC DEVICE IS EQUIPPED WITH A SOURCE ENERGY IN TH dc LINK can observe or supply the active and reactive power to or supply the active and reactive power to or from the line. This application has been done in MATLAB/SIMULINK environment. The simulation results are obtained from a selected bus-2 in two machine power system shows and efficiency of this compensator is one of the facts device as a member in power flow controller to achieve desired value for active, reactive powers and damping oscillations appropriately,
Jacobi stability of the vacuum in the static spherically symmetric brane world models
Harko, T
2008-01-01
We analyze the stability of the structure equations of the vacuum in the brane world models, by using both the linear (Lyapunov) stability analysis, and the Jacobi stability analysis, the Kosambi-Cartan-Chern (KCC) theory. In the brane world models the four dimensional effective Einstein equations acquire extra terms, called dark radiation and dark pressure, respectively, which arise from the embedding of the 3-brane in the bulk. Generally, the spherically symmetric vacuum solutions of the brane gravitational field equations, have properties quite distinct as compared to the standard black hole solutions of general relativity. We close the structure equations by assuming a simple linear equation of state for the dark pressure. In this case the vacuum is Jacobi stable only for a small range of values of the proportionality constant relating the dark pressure and the dark radiation. The unstable trajectories on the brane behave chaotically, in the sense that after a finite radial distance it would be impossible...
Generalized Modelling of the Stabilizer Link and Static Simulation Using FEM
Cofaru, Nicolae Florin; Roman, Lucian Ion; Oleksik, Valentin; Pascu, Adrian
2016-12-01
This paper proposes an organological approach of one of the components of front suspension, namely anti-roll power link. There will be realized a CAD 3D modelling of this power link. 3D modelling is generalized and there were used the powers of Catia V5R20 software. Parameterized approach provides a high flexibility in the design, meaning that dimensional and shape changes of the semi-power link are very easy to perform just by changing some parameters. Several new versions are proposed for the anti-roll power link body. At the end of the work, it is made a static analysis of the semi-power link model used in the suspension of vehicles OPEL ASTRA G, ZAFIRA, MERIVA, and constructive optimization of its body.
Venkateswara Rao, B.; Kumar, G. V. Nagesh; Chowdary, D. Deepak; Bharathi, M. Aruna; Patra, Stutee
2017-07-01
This paper furnish the new Metaheuristic algorithm called Cuckoo Search Algorithm (CSA) for solving optimal power flow (OPF) problem with minimization of real power generation cost. The CSA is found to be the most efficient algorithm for solving single objective optimal power flow problems. The CSA performance is tested on IEEE 57 bus test system with real power generation cost minimization as objective function. Static VAR Compensator (SVC) is one of the best shunt connected device in the Flexible Alternating Current Transmission System (FACTS) family. It has capable of controlling the voltage magnitudes of buses by injecting the reactive power to system. In this paper SVC is integrated in CSA based Optimal Power Flow to optimize the real power generation cost. SVC is used to improve the voltage profile of the system. CSA gives better results as compared to genetic algorithm (GA) in both without and with SVC conditions.
傅旭; 付翀丽; 黄明良
2015-01-01
The effect of ZIP load characteristics on node static voltage stability is analyzed in detail. It is pointed out that the constant power component in ZIP load determines the degree of static voltage stability of the node. A new index for voltage stability based on locally measurable quantities considering the load static characteristics is presented. A simple calculation method for calculating the Thevenin equivalent parameter is provided. The proposed index is tested on IEEE 57-bus systems, and the simulation results indicate that this index can correctly reflect the effect of load static characteristics on node voltage stability, and the calculation of the Thevenin equivalent parameter is simple, thus it is suitable for the on-line monitoring of static voltage stability.%详细分析ZIP负荷特性对节点静态电压稳定性的影响规律，指出ZIP负荷中的恒定功率分量决定了该节点的静态电压稳定程度，提出一种基于局部测量的计及负荷静态特性的电压稳定指标，并给出一种简单的计算节点戴维南等值参数的计算方法。IEEE 57节点仿真表明所提指标可以很好地考虑负荷静态特性对节点电压稳定性的影响，并且戴维南等值参数计算简单，适合于静态电压稳定的在线监控。
Ivashchuk, V.D. [VNIIMS, Center for Gravitation and Fundamental Metrology, Moscow (Russian Federation); Peoples' Friendship University of Russia (RUDN University), Institute of Gravitation and Cosmology, Moscow (Russian Federation)
2016-08-15
A (n + 1)-dimensional gravitational model with Gauss-Bonnet term and a cosmological constant term is considered. When ansatz with diagonal cosmological metrics is adopted, the solutions with an exponential dependence of the scale factors, a{sub i} ∝ exp(v{sup i}t), i = 1,.., n, are analyzed for n > 3. We study the stability of the solutions with non-static volume factor, i.e. K(v) = sum {sub k=1}{sup n} v{sup k} ≠ 0. We prove that under a certain restriction R imposed solutions with K(v) > 0 are stable, while solutions with K(v) < 0 are unstable. Certain examples of stable solutions are presented. We show that the solutions with v{sup 1} = v{sup 2} = v{sup 3} = H > 0 and zero variation of the effective gravitational constant are stable if the restriction R is obeyed. (orig.)
Particle-bubble aggregate stability on static bubble generated by single nozzle on flotation process
Warjito, Harinaldi, Setyantono, Manus; Siregar, Sahala D.
2016-06-01
There are three sub-processes on flotation. These processes are intervening liquid film into critical thickness, rupture of liquid film forming three phase contact line, and expansion three phase contact line forming aggregate stability. Aggregate stability factor contribute to determine flotation efficiency. Aggregate stability has some important factors such as reagent and particle geometry. This research focussed on to understand effect of particle geometry to aggregate stability. Experimental setup consists of 9 x 9 x26 cm flotation column made of glass, bubble generator, particle feeding system, and high speed video camera. Bubble generator made from single nozzle with 0.3 mm diameter attached to programmable syringe pump. Particle feeding system made of pipette. Particle used in this research is taken from open pit Grasberg in Timika, Papua. Particle has sub-angular geometry and its size varies from 38 to 300 µm. Bubble-particle interaction are recorded using high speed video camera. Recordings from high speed video camera analyzed using image processing software. Experiment result shows that aggregate particle-bubble and induction time depends on particle size. Small particle (38-106 µm) has long induction time and able to rupture liquid film and also forming three phase contact line. Big particle (150-300 µm) has short induction time, so it unable to attach with bubble easily. This phenomenon is caused by apparent gravity work on particle-bubble interaction. Apparent gravity worked during particle sliding on bubble surface experience increase and reached its maximum magnitude at bubble equator. After particle passed bubble equator, apparent gravity force experience decrease. In conclusion particle size from 38-300 µm can form stable aggregate if particle attached with bubble in certain condition.
Kilkenny, E. A.
1986-01-01
A mobile experimental test facility has been developed to carry out the aerodynamic evaluation of hang glider wings normally performed in a wind tunnel. Longitudinal aerodynamic data obtained using this facility is presented for three modern hang glider wings, a Silhouette, Demon 175 and Magic 166, together with surface flow patterns for the latter two wings. The longitudinal stability criterion are studied and alternatives established, equivalent to the stick fixed an...
Improved Phase Stability of Formamidinium Lead Triiodide Perovskite by Strain Relaxation
Zheng, Xiaojia; Wu, Congcong; Jha, Shikhar K.; Li, Zhen; Zhu, Kai; Priya, Shashank
2016-11-11
Though formamidinium lead triiodide (FAPbI3) possesses a suitable band gap and good thermal stability, the phase transition from the pure black perovskite phase (a-phase) to the undesirable yellow nonperovskite polymorph (..delta..-phase) at room temperature, especially under humid air, hinders its practical application. Here, we investigate the intrinsic instability mechanism of the ..alpha..-phase at ambient temperature and demonstrate the existence of an anisotropic strained lattice in the (111) plane that drives phase transformation into the ..delta..-phase. Methylammonium bromide (MABr) alloying (or FAPbI3-MABr) was found to cause lattice contraction, thereby balancing the lattice strain. This led to dramatic improvement in the stability of ..alpha..-FAPbI3. Solar cells fabricated using FAPbI3-MABr demonstrated significantly enhanced stability under the humid air.
Feng, Xiao-Li; Li, Yu-Xiao; Gu, Jian-Zhong; Zhuo, Yi-Zhong
2009-10-01
The relaxation property of both Eigen model and Crow-Kimura model with a single peak fitness landscape is studied from phase transition point of view. We first analyze the eigenvalue spectra of the replication mutation matrices. For sufficiently long sequences, the almost crossing point between the largest and second-largest eigenvalues locates the error threshold at which critical slowing down behavior appears. We calculate the critical exponent in the limit of infinite sequence lengths and compare it with the result from numerical curve fittings at sufficiently long sequences. We find that for both models the relaxation time diverges with exponent 1 at the error (mutation) threshold point. Results obtained from both methods agree quite well. From the unlimited correlation length feature, the first order phase transition is further confirmed. Finally with linear stability theory, we show that the two model systems are stable for all ranges of mutation rate. The Eigen model is asymptotically stable in terms of mutant classes, and the Crow-Kimura model is completely stable.
Daniels, Janet; Smith, G. Louis; Priestley, Kory J.; Thomas, Susan
2014-10-01
Validation of in-orbit instrument performance is a function of stability in both instrument and calibration source. This paper describes a method using lunar observations scanning near full moon by the Clouds and Earth Radiant Energy System (CERES) instruments. The Moon offers an external source whose signal variance is predictable and non-degrading. From 2006 to present, these in-orbit observations have become standardized and compiled for the Flight Models -1 and -2 aboard the Terra satellite, for Flight Models-3 and -4 aboard the Aqua satellite, and beginning 2012, for Flight Model-5 aboard Suomi-NPP. Instrument performance measurements studied are detector sensitivity stability, pointing accuracy and static detector point response function. This validation method also shows trends per CERES data channel of 0.8% per decade or less for Flight Models 1-4. Using instrument gimbal data and computed lunar position, the pointing error of each detector telescope, the accuracy and consistency of the alignment between the detectors can be determined. The maximum pointing error was 0.2o in azimuth and 0.17o in elevation which corresponds to an error in geolocation near nadir of 2.09 km. With the exception of one detector, all instruments were found to have consistent detector alignment from 2006 to present. All alignment error was within 0.1o with most detector telescopes showing a consistent alignment offset of less than 0.02o.
Khan Aafreen
2014-11-01
Full Text Available Power system security is recognized as one of the major problems in many power systems throughout the world. Power system insecurity such as transmission lines being overloaded causes transmission elements cascade outages, which may lead to complete blackout. In accordance with these reasons, the prediction and recognition of voltage instability in power system has particular importance and it makes the network security stronger. This work, by considering the power system contingencies based on the effects of them on Mega Watt Margin (MWM and maximum loading point (MLP is focused to analyse the voltage stability using continuation power flow method. The study has been carried out on IEEE 30-Bus Test System using MATLAB and PSAT softwares and results are presented.
Influence of stability islands in the recurrence of particles in a static oval billiard with holes
Hansen, Matheus; Egydio de Carvalho, R.; Leonel, Edson D.
2016-10-01
Statistical properties for the recurrence of particles in an oval billiard with a hole in the boundary are discussed. The hole is allowed to move in the boundary under two different types of motion: (i) counterclockwise periodic circulation with a fixed step length and; (ii) random movement around the boundary. After injecting an ensemble of particles through the hole we show that the surviving probability of the particles without recurring - without escaping - from the billiard is described by an exponential law and that the slope of the decay is proportional to the relative size of the hole. Since the phase space of the system exhibits islands of stability we show there are preferred regions of escaping in the polar angle, hence given a partial answer to an open problem: Where to place a hole in order to maximize or minimize a suitable defined measure of escaping.
金鑫鑫; 金峰; 刘宁; 孙其诚
2016-01-01
The granular system has complicated force chain network and multiple relaxation mechanisms. The different relaxation mechanisms have largely effects on others. The force chains divide the whole system into many soft zones which dominate the main dissipation process. The system evolves into lower potential energy state gradually and forms directional arrangement under an external load. During the evolution, the complex relaxation behaviors such as transport and migrant processes, make it diﬃcult to distinguish different dissipated mechanisms. Each single physical mechanism stripping from multiple mechanisms should be studied in depth. While among all the mechanisms, the structure evolution plays a crucial role and needs to be paid more attention to. From the view of potential energy, the detailed energy transformation is illustrated. The granular system is often at a metastable state. When the external disturbance is large enough, the system would step over the energy barrier to a new state. The height of energy barrier is related to the packing structure and grain property. In energy landscape, there exist many energy valleys which correspond to different metastable states. The grain rearrangement and structure reorganization are two main evolution processes at a quasi-static state. The former brings about major potential energy change because of friction and forms certain contact relations. While the latter evolves on the basis of the skeleton formed by grain rearrangement and reaches lower energy state. The conversion among different energy valleys can be used to explain stress relaxation process. In a complex granular system, the choosing of appropriate internal state variables becomes important, which can reflect specific relaxation process and internal characteristics. The energy fluctuation in the system has a huge influence on dissipation process and macroscopic response and is an effective internal variable to have an insight into the structure evolution
Sona Padma
2011-01-01
Full Text Available Problem statement: FACTS devices play a major role in the efficient operation of the complex power system. FACTS devices such as STATCOM, SSSC and IPFC are in increasing usage. With energy storage systems they have a good control over the real as well as reactive power compensation and transient stability improvement. The design of controller for the SSSC with SMES system is analyzed in this study. Approach: The main variables to be controlled in the power system for efficient operation are the voltage, phase angle and impedance. A SSSC is a series connected converter based FACTS control which can provide a series reactive power compensation for a transmission system. With the addition of energy storage device, in addition to the reactive power compensation the real power exchange is also accomplished. Fuzzy logic controller is designed for the efficient operation of the power system with SSSC integrated with energy storage device. From the power reference the current reference is calculated and the error and change in error in the current are calculated in the controller. Results: A three phase to ground fault is simulated in the test system. A comparative analysis of the PI and fuzzy logic control of SSSC with energy storage system for the rotor angle oscillation damping following the disturbance is done. Conclusion: The fuzzy logic controller works efficiently compared to the conventional PI controller for the SSSC with SMES system. Also with energy storage system in the FACTS devices, the efficient operation of the power system is possible.
QUASI-STATIC MODEL OF MAGNETICALLY COLLIMATED JETS AND RADIO LOBES. II. JET STRUCTURE AND STABILITY
Colgate, Stirling A.; Li, Hui [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Fowler, T. Kenneth [University of California, Berkeley, CA 94720 (United States); Hooper, E. Bickford [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); McClenaghan, Joseph; Lin, Zhihong [University of California, Irvine, CA 92697 (United States)
2015-11-10
This is the second in a series of companion papers showing that when an efficient dynamo can be maintained by accretion disks around supermassive black holes in active galactic nuclei, it can lead to the formation of a powerful, magnetically driven, and mediated helix that could explain both the observed radio jet/lobe structures and ultimately the enormous power inferred from the observed ultrahigh-energy cosmic rays. In the first paper, we showed self-consistently that minimizing viscous dissipation in the disk naturally leads to jets of maximum power with boundary conditions known to yield jets as a low-density, magnetically collimated tower, consistent with observational constraints of wire-like currents at distances far from the black hole. In this paper we show that these magnetic towers remain collimated as they grow in length at nonrelativistic velocities. Differences with relativistic jet models are explained by three-dimensional magnetic structures derived from a detailed examination of stability properties of the tower model, including a broad diffuse pinch with current profiles predicted by a detailed jet solution outside the collimated central column treated as an electric circuit. We justify our model in part by the derived jet dimensions in reasonable agreement with observations. Using these jet properties, we also discuss the implications for relativistic particle acceleration in nonrelativistically moving jets. The appendices justify the low jet densities yielding our results and speculate how to reconcile our nonrelativistic treatment with general relativistic MHD simulations.
Aromataris, Luis [Universidad Nacional de Rio Cuarto (UNRC) (Argentina); Arnera, Patricia; Riubrugent, Jean [Universidad Nacional de La Plata, Buenos Aires (Argentina). Facultad de Ingenieria. Instituto de Investigaciones Tecnologicas para Redes y Equipos Electricos
2001-07-01
This work investigate the impact produced by the load model on the voltage stability analysis of an electric system. Qualitative and quantitative analyses are approached in connection with the effects of modeling the electric loads by both dynamical and static way. Also it is highlighted the importance of using dynamical models of load, mainly when it is composed by motors.
Bird, John D; Lichtenstein, Jacob H; Jaquet, Byron M
1952-01-01
Results are presented of a wind-tunnel investigation to determine influence of the fuselage and tail on static stability and rotary derivatives in roll of a model having 45 degrees sweptback wing and tail surfaces. The wing alone and the model without the horizontal tail showed marginal longitudinal stability near maximum lift. The longitudinal stability of the complete model was satisfactory. The vertical tail produced larger increments of rate of change of lateral-force and yawing-moment coefficients with wing-tip helix angle than the fuselage or the horizontal tail.
Weil, Joseph; Sleeman, William C , Jr
1949-01-01
The effects of propeller operation on the static longitudinal stability of single-engine tractor monoplanes are analyzed, and a simple method is presented for computing power-on pitching-moment curves for flap-retracted flight conditions. The methods evolved are based on the results of powered-model wind-tunnel investigations of 28 model configurations. Correlation curves are presented from which the effects of power on the downwash over the tail and the stabilizer effectiveness can be rapidly predicted. The procedures developed enable prediction of power-on longitudinal stability characteristics that are generally in very good agreement with experiment.
Abbas Rahimi
2012-07-01
Full Text Available Background and Aim: Reviewing the literature reveals a possible correlation between the obesity and the potential foot, spine and stability problems. Investigating the important parameters affecting the balance of obese people and prevention from falling are of high importance to reduce the resulting expenditures. This study aimed to assess the acts and the counter acts between the medial longitudinal arch (MLA and the thoracic and lumbar curvatures with the static and dynamic stability in obese females. Materials and Methods: Twenty eight obese females (age= 25±8 years old, BMI=37±4 and twenty nine non-obese females (age= 23±4 years old, BMI=23±3 were recruited in this case-control study with the cross-sectional technique. The MLA, spinal curve angles and the static or dynamic balance index of the subjects were measured using the navicular drop, flexible ruler and Biodex balance system tools, respectively. The static balance test was carried out using a modified Clinical Test of Sensory Interaction and Balance (CTSIB test in both the open and closed eyes while the subjects stood on their dominant legs. The order of the dynamic and static tests was selected randomly.Results: The findings of this study showed that in closed eye condition, most changes happened between the global Stability Index (SI and BMI; while in open eye condition, most changes occurred between the lateral-medial stability index and BMI (r=0.5. Also during an open eye condition, a moderate correlation was found between the navicular drop and lateral-medial stability index (r=0.05. In closed eyes condition, no significant changes were found between the SI and lumbar lordosis (r=0.0004; while a weak correlation was found between the thoracic curve angle and lateral-medial stability index (r=0.04.Conclusion: The dynamic stability is not only correlated to their BMI, but is highly dependent on their foot curvature types and slightly on their thoracic curve angle. Abdominal
Duan, Shu-Chao
2016-01-01
We construct eight implicit-explicit (IMEX) Runge-Kutta (RK) schemes up to third order of the type in which all stages are implicit so that they can be used in the zero relaxation limit in a unified and convenient manner. These all-stages-implicit (ASI) schemes attain the strong-stability-preserving (SSP) property in the limiting case, and two are SSP for not only the explicit part but also the implicit part and the entire IMEX scheme. Three schemes can completely recover to the designed accuracy order in two sides of the relaxation parameter for both equilibrium and non-equilibrium initial conditions. Two schemes converge nearly uniformly for equilibrium cases. These ASI schemes can be used for hyperbolic systems with stiff relaxation terms or differential equations with some type constraints.
Chalapathi, P.V. [Department of Physics, A.K.R.G. College of Engineering and Technology, Nallajerla 534112 (India); Srinivasulu, M. [Department of Chemistry, Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Pisipati, V.G.K.M. [Department of Electronics and Communications Engineering, R and D Division, KL-University, Vaddeswaram (India); Satyanarayana, Ch. [Department of Computers Science Engineering, University College of Engineering, Jawaharlal Nehru Technological University: Kakinada, Kakinada 533003 (India); Potukuchi, D.M., E-mail: potukuchidm@yahoo.co [Department of Physics, University College of Engineering, Jawaharlal Nehru Technological University: Kakinada, Kakinada 533003 (India)
2011-05-15
The occurrence of ferroelectric phases and influence of chemical moieties in the area of supra-molecular achiral Bent core Liquid Crystals (BLCs) are reviewed. Synthesis of an intermediate/higher homolog of PBnOB series (for n=11), PBUOB, viz. 1,3-Phenyline-Bis(4-UndecylOxy Benzoate), is presented. Smectic LC phases exhibited by PBUOB are characterized by Polarized Optical Microscopy (POM), Differential Scanning Calorimetry (DSC) and Spontaneous Polarization (P{sub S}) techniques. Observations infer a bi-variant FE LC smectic phase occurrence, viz., isotropic{yields}B{sub 2}(FE){yields}B{sub 5}(FE){yields}solid phases in cooling and solid{yields}B{sub 5{yields}}isotropic phases in heating scans. Occurrence of B{sub 2} phase is monotropic (in cooling), while B{sub 5} phase is enantiotropic. I-B{sub 2} and B{sub 2}-B{sub 5} phase transitions are found to be of first order nature. The FE phases possess a moderate P{sub S} value of {approx}40 nC cm{sup -2}. Transition temperatures from dielectric studies agree with those from TM and DSC. Two modes of relaxations are observed, viz., a slow scissor mode at {approx}1 kHz and a fast mode at {approx}1 MHz. Anisotropic Dipolar Model is proposed to explain the reorientation mechanism. Arrhenius shifts of Relaxation Frequency (f{sub R}) show differing activation energies for two modes, i.e., 0.11 and 0.98 eV; 0.25 and 1.18 eV in B{sub 2} and B{sub 5} phases, respectively. Temperature variation of dielectric increment {Delta}{epsilon} and {alpha}-parameter LC phases reveals the relative fixture of dipole moment in polar smectic layers. An analytical study for the thermal stability, P{sub S} and f{sub R} in the FE phases is presented with respect to the constitution and configuration of moieties in BLCs.
Martinez, P.; Kasper, M.; Costille, A.; Sauvage, J. F.; Dohlen, K.; Puget, P.; Beuzit, J. L.
2013-06-01
Context. Observing sequences have shown that the major noise source limitation in high-contrast imaging is the presence of quasi-static speckles. The timescale on which quasi-static speckles evolve is determined by various factors, mechanical or thermal deformations, among others. Aims: Understanding these time-variable instrumental speckles and, especially, their interaction with other aberrations, referred to as the pinning effect, is paramount for the search for faint stellar companions. The temporal evolution of quasi-static speckles is, for instance, required for quantifying the gain expected when using angular differential imaging (ADI) and to determining the interval on which speckle nulling techniques must be carried out. Methods: Following an early analysis of a time series of adaptively corrected, coronagraphic images obtained in a laboratory condition with the high-order test bench (HOT) at ESO Headquarters, we confirm our results with new measurements carried out with the SPHERE instrument during its final test phase in Europe. The analysis of the residual speckle pattern in both direct and differential coronagraphic images enables the characterization of the temporal stability of quasi-static speckles. Data were obtained in a thermally actively controlled environment reproducing realistic conditions encountered at the telescope. Results: The temporal evolution of the quasi-static wavefront error exhibits a linear power law, which can be used to model quasi-static speckle evolution in the context of forthcoming high-contrast imaging instruments, with implications for instrumentation (design, observing strategies, data reduction). Such a model can be used for instance to derive the timescale on which non-common path aberrations must be sensed and corrected. We found in our data that quasi-static wavefront error increases with ~0.7 Å per minute.
Wei-Cheng Wang
2002-06-01
Full Text Available We study the asymptotic equivalence of the Jin-Xin relaxation model and its formal limit for genuinely nonlinear $2imes 2$ conservation laws. The initial data is allowed to have jump discontinuities corresponding to centered rarefaction waves, which includes Riemann data connected by rarefaction curves. We show that, as long as the initial data is a small perturbation of a constant state, the solution for the relaxation system exists globally in time and converges, in the zero relaxation limit, to the solution of the corresponding conservation law uniformly except for an initial layer.
Wu, X.; Arulampalam, A.; Zhan, C.; Jenkins, N.
2003-03-01
A control strategy to improve the stability of a large wind farm using a Static Reactive Power Compensator (STATCOM) and Dynamic Braking Resistor (DBR) is proposed and investigated. The STATCOM supplies the reactive power demand of the wind farm dynamically in order to maintain the network voltage. The DBR is controlled by Liapunov's stability criterion to absorb the active power of the wind farm during the network fault. The performance of the STATCOM and DBR, applied to a large wind farm (60MW), is studied in PSCAD/EMTDC. The simulation results show that effective control of the STATCOM and DBR together can enhance the stability of large wind farms. (author)
Jacopo Zenzeri
2013-01-01
Full Text Available The goal of this paper is to analyze the static stability of a computational architecture, based on the Passive Motion Paradigm, for coordinating the redundant degrees of freedom of a humanoid robot during whole-body reaching movements in bipedal standing. The analysis is based on a simulation study that implements the Functional Reach Test, originally developed for assessing the danger of falling in elderly people. The study is carried out in the YARP environment that allows realistic simulations with the iCub humanoid robot.
Gatti-Lafranconi, Pietro; Natalello, Antonino; Rehm, Sascha; Doglia, Silvia Maria; Pleiss, Jürgen; Lotti, Marina
2010-01-08
Molecular aspects of thermal adaptation of proteins were studied by following the co-evolution of temperature dependence, conformational stability, and substrate specificity in a cold-active lipase modified via directed evolution. We found that the evolution of kinetic stability was accompanied by a relaxation in substrate specificity. Moreover, temperature dependence and selectivity turned out to be mutually dependent. While the wild-type protein was strictly specific for short-chain triglycerides (C4) in the temperature range 10-50 degrees C and displayed highest activity in the cold, its stabilized variant was able to accept C8 and C12 molecules and its selectivity was temperature dependent. We could not detect any improvement in the overall structural robustness of the mutant when the structure was challenged by temperature or chemical denaturants. There is, however, strong evidence for local stabilization effects in the active-site region provided by two independent approaches. Differential scanning fluorimetry revealed that the exposure of hydrophobic patches (as the active site is) precedes denaturation, and molecular dynamics simulations confirmed that stability was obtained by restriction of the mobility of the lid, a flexible structure that regulates the access to the enzyme active site and influences its stability. This reduction of lid movements is suggested to be accompanied by a concomitant increase in the mobility of other protein regions, thus accounting for the observed broadening of substrate specificity.
Silva, Juan P.; Lasso, Ana; Lubberding, Henk J.; Peña, Miguel R.; Gijzen, Hubert J.
2015-05-01
The closed static chamber technique is widely used to quantify greenhouse gases (GHG) i.e. CH4, CO2 and N2O from aquatic and wastewater treatment systems. However, chamber-measured fluxes over air-water interfaces appear to be subject to considerable uncertainty, depending on the chamber design, lack of air mixing in the chamber, concentration gradient changes during the deployment, and irregular eruptions of gas accumulated in the sediment. In this study, the closed static chamber technique was tested in an anaerobic pond operating under tropical conditions. The closed static chambers were found to be reliable to measure GHG, but an intrinsic limitation of using closed static chambers is that not all the data for gas concentrations measured within a chamber headspace can be used to estimate the flux due to gradient concentration curves with non-plausible and physical explanations. Based on the total data set, the percentage of curves accepted was 93.6, 87.2, and 73% for CH4, CO2 and N2O, respectively. The statistical analyses demonstrated that only considering linear regression was inappropriate (i.e. approximately 40% of the data for CH4, CO2 and N2O were best fitted to a non-linear regression) for the determination of GHG flux from stabilization ponds by the closed static chamber technique. In this work, it is clear that when R2adj-non-lin > R2adj-lin, the application of linear regression models is not recommended, as it leads to an underestimation of GHG fluxes by 10-50%. This suggests that adopting only or mostly linear regression models will affect the GHG inventories obtained by using closed static chambers. According to our results, the misuse of the usual R2 parameter and only the linear regression model to estimate the fluxes will lead to reporting erroneous information on the real contribution of GHG emissions from wastewater. Therefore, the R2adj and non-linear regression model analysis should be used to reduce the biases in flux estimation by the
Marzola, Luca; Raidal, Martti
2016-11-01
Motivated by natural inflation, we propose a relaxation mechanism consistent with inflationary cosmology that explains the hierarchy between the electroweak scale and Planck scale. This scenario is based on a selection mechanism that identifies the low-scale dynamics as the one that is screened from UV physics. The scenario also predicts the near-criticality and metastability of the Standard Model (SM) vacuum state, explaining the Higgs boson mass observed at the Large Hadron Collider (LHC). Once Majorana right-handed neutrinos are introduced to provide a viable reheating channel, our framework yields a corresponding mass scale that allows for the seesaw mechanism as well as for standard thermal leptogenesis. We argue that considering singlet scalar dark matter extensions of the proposed scenario could solve the vacuum stability problem and discuss how the cosmological constant problem is possibly addressed.
Rustad, James R.; Felmy, Andrew R.; Hay, Benjamin P.
1996-05-01
A new approach to estimating stability constants for proton binding in multisite surface complexation models is presented. The method is based on molecular statics computation of energies for the formation of proton vacancies and interstitials in ideal periodic slabs representing the (100), (110), (010), (001), and (021) surfaces of goethite. Gas-phase energies of clusters representing the hydrolysis products of ferric iron are calculated using the same potential energy functions used for the surface. These energies are linearly related to the hydrolysis constants for ferric iron in aqueous solution. Stability constants for proton binding at goethite surfaces are estimated by assuming the same log K- Δ E relationship for goethite surface protonation reactions. These stability constants predict a pH of zero charge of 8.9, in adequate agreement with measurements on CO 2-free goethite. The estimated stability constants differ significantly from previous estimations based on Pauling bond strength. We find that nearly all the surface oxide ions are reactive; nineteen of the twenty-six surface sites investigated have log Kint between 7.7 and 9.4. This implies a site density between fifteen and sixteen reactive sites/nm for crystals dominated by (110) and (021) crystal faces.
Syvertson, Clarence A; Gloria, Hermilo R; Sarabia, Michael F
1958-01-01
A study is made of aerodynamic performance and static stability and control at hypersonic speeds. In a first part of the study, the effect of interference lift is investigated by tests of asymmetric models having conical fuselages and arrow plan-form wings. The fuselage of the asymmetric model is located entirely beneath the wing and has a semicircular cross section. The fuselage of the symmetric model was centrally located and has a circular cross section. Results are obtained for Mach numbers from 3 to 12 in part by application of the hypersonic similarity rule. These results show a maximum effect of interference on lift-drag ratio occurring at Mach number of 5, the Mach number at which the asymmetric model was designed to exploit favorable lift interference. At this Mach number, the asymmetric model is indicated to have a lift-drag ratio 11 percent higher than the symmetric model and 15 percent higher than the asymmetric model when inverted. These differences decrease to a few percent at a Mach number of 12. In the course of this part of the study, the accuracy to the hypersonic similarity rule applied to wing-body combinations is demonstrated with experimental results. These results indicate that the rule may prove useful for determining the aerodynamic characteristics of slender configurations at Mach numbers higher than those for which test equipment is really available. In a second part of the study, the aerodynamic performance and static stability and control characteristics of a hypersonic glider are investigated in somewhat greater detail. Results for Mach numbers from 3 to 18 for performance and 0.6 to 12 for stability and control are obtained by standard text techniques, by application of the hypersonic stability rule, and/or by use of helium as a test medium. Lift-drag ratios of about 5 for Mach numbers up to 18 are shown to be obtainable. The glider studied is shown to have acceptable longitudinal and directional stability characteristics through the
Purser, Paul E.; Spear, Margaret F.
1947-01-01
A wind-tunnel investigation has been made to determine the effects of unsymmetrical horizontal-tail arrangements on the power-on static longitudinal stability of a single-engine single-rotation airplane model. Although the tests and analyses showed that extreme asymmetry in the horizontal tail indicated a reduction in power effects on longitudinal stability for single-engine single-rotation airplanes, the particular "practical" arrangement tested did not show marked improvement. Differences in average downwash between the normal tail arrangement and various other tail arrangements estimated from computed values of propeller-slipstream rotation agreed with values estimated from pitching-moment test data for the flaps-up condition (low thrust and torque) and disagreed for the flaps-down condition (high thrust and torque). This disagreement indicated the necessity for continued research to determine the characteristics of the slip-stream behind various propeller-fuselage-wing combinations. Out-of-trim lateral forces and moments of the unsymmetrical tail arrangements that were best from consideration of longitudinal stability were no greater than those of the normal tail arrangement.
Byrdsong, T. A.; Hallissy, J. B.
1979-01-01
An investigation was conducted in the Langley 8-foot transonic pressure tunnel to determine the longitudinal and lateral-directional static stability and control characteristics of a 1/6-scale force model of a remotely piloted research vehicle. The model was equipped with a supercritical wing and employed elevons for pitch and roll control. Test conditions were as follows: Reynolds number of about 6.6 x 10 to the 6th power per meter, variations of sideslip from -6 deg to 6 deg, elevon deflection angle (symmetrically and asymmetrically) from -9 deg to 3 deg, and rudder deflection angle from 0 deg to -10 deg. The model was longitudinally statically stable at angles of attack up to about 7 deg, which is significantly greater than the angle of attack for the cruise condition (approximately 4 deg). In the range of test Mach numbers, the model was directionally stable and had positive effective dihedral, sufficient pitch control, and positive effectiveness of roll and yaw control.
Ware, George M.
1960-01-01
An investigation of the low-subsonic-speed static longitudinal stability and control characteristics of a model of a manned reentry-vehicle configuration capable of high-drag reentry and glide landing has been a made in the Langley free-flight tunnel. The model had a modified 63 deg delta plan-form wing with a fuselage on the upper surface. This configuration had wingtip panels designed to fold up 90 deg for the high-drag reentry phase of the flight and to extend horizontally for the glide landing. Data for the basic configurations and modifications to determine the effects of plan form, wingtip panel incidence, dihedral, and vertical position of the wingtip panels are presented without analysis.
2004-12-01
introduced to the wind tunnel. Its dimensions are 122”w * 111”h * 70”d. In order to provide a good quality of air with the minimum turbulence possible...inches % Requeried for the Solid body blockage corrections due to wing and fuselage Body_Volume = ((9.42962435*(2...vertical stabilizers (Tail 2)+ Connector+Prop-to-Wing+Wing Front-to- Wing Back % Requeried for the Pitching Moment
Logunov, S. L.; Pashchenko, V. Z.
1989-01-01
Picosecond absorption spectroscopy was used in a study of stabilization of a primary ion-radical pair P +I - in reaction centers of purple bacteria Rb. sphaeroides. Measurements were made on samples with hydrogen bonds modified by isotopic substitution of H2O with D2O and by introduction of cryoprotectors into the structure of the reaction centers. The state P +I -, which appeared as a result of separation of charges in a P *I complex, was stabilized by the interaction of P +I - with charged light groups of the water-protein environment in modified reaction centers after an interval of ~ 1 ns (stabilization in control samples took ~ 100 ps). Moreover, the transport of an electron to the next acceptor Qa was slowed down (by a factor of ~ 5) in modified reaction centers and the probability of recombination of charges increased (by a factor of ~ 3) in the unrelaxed state. Relaxation processes lowered the energy level of P +I - by 0.03-0.05 eV and reduced the energy of the interaction in an ion-radical pair by a factor of 2.
AN EXPERIMENTAL STUDY ON THE RELAXATION OF BOLTS
Muhammad Abid
2015-05-01
Full Text Available Loss of pre-load with time, commonly known as ‘Relaxation’ is an established phenomena. Behaviour of a bolted joint depends upon the pre-load in the bolts in use, not the pre-load introduced by the mechanic. Loss of pre-load is expected due to the many factors such as embedment relaxation, gasket creep, elastic interactions, and vibration loosening or stress relaxation. In a gasketed joint, due to the gasket flexibility, relaxation is always substantial during preliminary passes, as 80 to 100% loss is not uncommon in almost all the bolts, resulting in a dynamic behaviour. Pre-load in a gasketed joint is stabilized and retained to certain extent in the final passes only. In a non-gasketed joint, due to no gasket and no rotation its static behaviour is concluded. This paper highlights the factors affecting the amount of relaxation with time and presents important considerations that can reduce this. Both the short and long term relaxations are recorded and a ‘best fit’ model for relaxation behaviour is derived.
Field theory of bicritical and tetracritical points. II. Relaxational dynamics.
Folk, R; Holovatch, Yu; Moser, G
2008-10-01
We calculate the relaxational dynamical critical behavior of systems of O(n_||)(plus sign in circle)O(n_perpendicular) symmetry by renormalization group method within the minimal subtraction scheme in two-loop order. The three different bicritical static universality classes previously found for such systems correspond to three different dynamical universality classes within the static borderlines. The Heisenberg and the biconical fixed point lead to strong dynamic scaling whereas in the region of stability of the decoupled fixed point weak dynamic scaling holds. Due to the neighborhood of the stability border between the strong and the weak scaling dynamic fixed point to the dynamical stable fixed point a very small dynamic transient exponent of omega(Beta)_(v) =0.0044 is present in the dynamics for the physically important case n_|| =1 and n_perpendicular =2 in d=3 .
The stability of piezoceramic materials properties at external influences
Kuzenko D. V.
2010-02-01
Full Text Available The impact of exciting electric fields (static and resonance frequency alternating, mechanical uniaxial loading and temperature on the stability of working parameters of piezoelectric ceramic elements had been investigated. It is shown that after the removal of excitation the long relaxation of properties under the law close to logarithmic is observed.
Valerie-Marie Kumer
2017-03-01
Full Text Available Wake characteristics are of great importance for wind park performance and turbine loads. While wind tunnel experiments provided a solid base for the basic understanding of the structure and dynamics of wind turbine wakes, the consequent step forward to characterize wakes is full-scale measurements in real atmospheric boundary layer conditions under different stability regimes. Scanning Doppler LiDAR measurements have proven to be a flexible and useful tool for such measurements. However, their advantage of measuring spatial fluctuation is accompanied by the limited temporal resolution of individual sampling volumes within the scanned area. This study presents results from LiDAR Doppler Beam Swing (DBS measurements and highlights the potential of information retrieved from a spectral analysis of wake measurements. Data originate from three Windcube v1 and sonic anemometers, collected during the Wind Turbine Wake Experiment–Wieringermeer. Despite the ongoing research on the reliability of turbulence retrievals based on DBS data, our results show wake peak frequencies consistent with sonic anemometer measurements. The energy spectra show rather distinct maxima during stable conditions, which broaden during unstable and neutral conditions. Investigations on the effect of blade pitch on downstream wind speed and turbulence intensity profiles indicate the potential for the development of stability-dependent wind farm control strategies.
Shenkarev, Zakhar O; Paramonov, Alexander S; Balashova, Tamara A; Yakimenko, Zoya A; Baru, Michael B; Mustaeva, Leila G; Raap, Jan; Ovchinnikova, Tatyana V; Arseniev, Alexander S
2004-12-17
Zervamicin IIB is a 16 amino acid peptaibol that forms voltage dependent ion channels with multilevel conductance states in planar lipid bilayers and vesicular systems. Stability of the hinge region and intermolecular interactions were investigated in the N- and C-terminally spin-labelled peptide analogues. Intermolecular and intramolecular paramagnetic enhancement indicates that zervamicin behaves as a rigid helical rod in methanol solution. There are no high amplitude hinge-bending motions, and the peptaibol is monomeric up to concentration 1.5 mM. Stability of the hinge region illustrates the helix stabilising propensity of the Pro residue in membrane mimic environments and implies absence of significant conformational rearrangement due to voltage peptaibol activation.
Static stability of a three-dimensional space truss. M.S. Thesis - Case Western Reserve Univ., 1994
Shaker, John F.
1995-01-01
In order to deploy large flexible space structures it is necessary to develop support systems that are strong and lightweight. The most recent example of this aerospace design need is vividly evident in the space station solar array assembly. In order to accommodate both weight limitations and strength performance criteria, ABLE Engineering has developed the Folding Articulating Square Truss (FASTMast) support structure. The FASTMast is a space truss/mechanism hybrid that can provide system support while adhering to stringent packaging demands. However, due to its slender nature and anticipated loading, stability characterization is a critical part of the design process. Furthermore, the dire consequences surely to result from a catastrophic instability quickly provide the motivation for careful examination of this problem. The fundamental components of the space station solar array system are the (1) solar array blanket system, (2) FASTMast support structure, and (3) mast canister assembly. The FASTMast once fully deployed from the canister will provide support to the solar array blankets. A unique feature of this structure is that the system responds linearly within a certain range of operating loads and nonlinearly when that range is exceeded. The source of nonlinear behavior in this case is due to a changing stiffness state resulting from an inability of diagonal members to resist applied loads. The principal objective of this study was to establish the failure modes involving instability of the FASTMast structure. Also of great interest during this effort was to establish a reliable analytical approach capable of effectively predicting critical values at which the mast becomes unstable. Due to the dual nature of structural response inherent to this problem, both linear and nonlinear analyses are required to characterize the mast in terms of stability. The approach employed herein is one that can be considered systematic in nature. The analysis begins with one
Malta, Paula Oliveira; Alves, Davi Silva; Ferreira, Aline Oliveira Vasconcelos; Moutinho, Iane Dutra; Dias, Carolina Arriel Pedroso; Santos, Dagoberto Brandão
2017-03-01
In the present study, Nb-stabilized ferritic stainless steel was prepared with annealing (430-A) and without annealing (430-NA) annealing, and the microstructure of the resulting samples was examined. The steel was then subjected to cold rolling and isothermal annealing in order to analyze its recrystallization kinetics and texture evolution. Microstructural characterization was performed by scanning and transmission electron microscopies. Recrystallization kinetics were evaluated by measuring the microhardness of the samples, and analyzing their kernel average misorientation and grain orientation spread via electron backscatter diffraction. The Avrami exponent data revealed that one-dimensional grain growth occurred owing to the migration of high-angle grain boundaries. The mean activation energies for recrystallization for 430-NA and 430-A was found to be 365 and 419 kJ mol-1, respectively. The recrystallization texture was influenced by oriented nucleation and selected growth mechanisms, as well as by the Nb carbonitride distribution and grain boundary energy. The recrystallized and growing grains with the {554} orientation showed a dimensional advantage over the other recrystallized components. The coincident site lattice boundaries were attributed to the progression of recrystallization since the CSL numeric fraction increased as the temperature increased. The {554} component was associated with the ∑19a boundary, which exerted a significant control on the selective growth during the recrystallization.
Malta, Paula Oliveira; Alves, Davi Silva; Ferreira, Aline Oliveira Vasconcelos; Moutinho, Iane Dutra; Dias, Carolina Arriel Pedroso; Santos, Dagoberto Brandão
2017-01-01
In the present study, Nb-stabilized ferritic stainless steel was prepared with annealing (430-A) and without annealing (430-NA) annealing, and the microstructure of the resulting samples was examined. The steel was then subjected to cold rolling and isothermal annealing in order to analyze its recrystallization kinetics and texture evolution. Microstructural characterization was performed by scanning and transmission electron microscopies. Recrystallization kinetics were evaluated by measuring the microhardness of the samples, and analyzing their kernel average misorientation and grain orientation spread via electron backscatter diffraction. The Avrami exponent data revealed that one-dimensional grain growth occurred owing to the migration of high-angle grain boundaries. The mean activation energies for recrystallization for 430-NA and 430-A was found to be 365 and 419 kJ mol-1, respectively. The recrystallization texture was influenced by oriented nucleation and selected growth mechanisms, as well as by the Nb carbonitride distribution and grain boundary energy. The recrystallized and growing grains with the {554} orientation showed a dimensional advantage over the other recrystallized components. The coincident site lattice boundaries were attributed to the progression of recrystallization since the CSL numeric fraction increased as the temperature increased. The {554} component was associated with the ∑19a boundary, which exerted a significant control on the selective growth during the recrystallization.
Static postural stability and sway spectrum of elderly individuals%老年人静态姿势稳定性及摆动频谱特征分析
张丽; 彭楠; 瓮长水; 王秋华; 黎春华; 李晓瑛; 陈蔚; 季红梅
2011-01-01
目的 观察老年人静态姿势摆动频谱和稳定性,分析老年人平衡功能下降的风险因素.方法 选择60-94岁老年患者85例,分为60-74岁组和≥75岁组.18-30岁健康对照组41例.采用Tetrax平衡测试系统测试受试者睁眼自然站立状态下的姿势摆动频谱和稳定性指数(ST).结果 姿势摆动强度(0.01-0.10)Hz:各组间差异不显著(P=0.110)；(0.10-3.00)Hz:≥75岁组＞60-74岁组/对照组,而对照组与60-74岁组比较差异不显著；≥3.00Hz:≥75岁组＞健康对照组＞60-74岁组.≥75岁组与60-74岁组比较在a=0.1水平存在显著性差异(P=0.094),而健康对照组与60-74岁组比较差异不显著(P=0.656).ST:≥75岁组＞60-74岁组＞健康对照组.≥75岁组与健康对照组和60-74岁组比较差异均显著(P=0.000),而健康对照组与60-74岁组比较差异不显著(P=0.436).结论 ≥75岁老年人静态姿势控制能力下降明显.外周前庭、中枢前庭和本体感觉功能异常是主要因素.%Objective To observe the static postural sway spectrum and postural stability of elderly individuals at different ages and analyze the main risk factors for impairment in static balance among elderly individuals over the age of 60 years. Methods Eighty-five elderly individuals at the age of 60-94 years were divided into 60-74 years old group and ≥75 years old group. Forty-one healthy individuals at the age of 18-30 years served as a control group. Their static stability(ST) and postural sway spectrum in standing with eyes opened were measured using the Tetrax balance system. Results No significant difference was observed in postural sway intensity at Fl(0.0l-0.10Hz) among different groups. The postural sway intensity at F2-F7(0.10-3.00Hz) and at F8( ≥ 3.00 Hz) was higher in ≥75 years old group than in 60-74 years old group and control group(P<0.01) with no significant difference between 60-74 years old group and control group. The ST was higher in ≥75 years old group
吴昊; 薛贵挺; 张焰; 杨增辉; 冯煜尧
2011-01-01
Due to the common mode outages and dependent outages have great impact on system static voltage stability,this paper focuses on the establishment of the equivalent branch outage model for two parallel transmission lines by considering outage overlapping, then computes the state probability of transmission system. Basing on the state probability model of power system, a risk index system of static voltage stability and the calculation method of every index are presented. By the voltage stability criteria based on CPF and optimal load shedding model, the loss of voltage stability of transmission system can be judged and controlled. Taking an area of power grid for east china for example, the risk of static voltage stability is assessed, which verifies the effectiveness of the proposed method.%鉴于双回平行输电线路共同模式停运和相关停运对系统电压稳定性影响较大,本文重点建立了双回线多种停运模式重叠的支路等效停运模型,进而计算输电系统状态概率.在输电系统状态概率模型的基础上,提出输电系统静态电压稳定风险评估指标体系及各项指标计算方法,其中通过基于连续潮流的电压稳定性判据及最优切负荷模型,对输电系统电压失稳进行判定及校正控制.最后以华东某地区电网为例进行静态电压稳定风险评估,说明本文所提方法的有效性.
刘道伟; 韩学山; 杨明; 吴萌; 王虹富; 董毅峰
2012-01-01
The concepts of static angle stability and voltage stability are inconsistent, which brings inconvenience to stability analysis and control. In the views of dynamics, this paper argues that the essence of the power system static stability is the balance during the source-network-load power transformation process, while voltage is just a physical quantity which supports the conversion process. The value of voltage has not necessary internal relationship with system static stability, and it is just a bounded problem of a non-linear power system output variable. Therefore, this paper deduced the maximum system active power transmission capability, and its semi-circular boundary in R-X coordinate. Based on eomprehensive physical parameter sensitivities, an applied criterion of generalized static stability, which expanded the static stability theory, was presented. In addition, the voltage support level index was given to measure system voltage support capability. Theory analysis and various simulation examples show the validity and rationality of the newly developed criterion, and it is expected to realize on-line static stability monitoring in power system based on wide-area measurement system （WAMS）.%针对静态的功角稳定和电压稳定在概念上尚未统一，给稳定分析与控制带来不便的情形。从动力学角度出发，提出电网静态稳定实质是电磁有功功率牵引下的“源-网-荷”功率转化平衡性问题。电压只是这一过程的支撑，性质上属于非线性系统输出变量的有界性问题，而与稳定性没有必然关系。由此，推演最大有功传输及其在R-X坐标上的半圆边界特性。基于全参量灵敏度，给出一种广义的静态稳定实用判据，使静态稳定理论得到扩展。另外，给出电压支撑量化指标，衡量电压支撑水平。理论研究与多场景算例分析表明了新判据的有效性和合理性，在广域测量（wide-areameasurement system
Martinez, P; Costille, A; Sauvage, J F; Dohlen, K; Puget, P; Beuzit, J L
2013-01-01
Observing sequences have shown that the major noise source limitation in high-contrast imaging is due to the presence of quasi-static speckles. The timescale on which quasi-static speckles evolve, is determined by various factors, among others mechanical or thermal deformations. Understanding of these time-variable instrumental speckles, and especially their interaction with other aberrations, referred to as the pinning effect, is paramount for the search of faint stellar companions. The temporal evolution of quasi-static speckles is for instance required for a quantification of the gain expected when using angular differential imaging (ADI), and to determine the interval on which speckle nulling techniques must be carried out. Following an early analysis of a time series of adaptively corrected, coronagraphic images obtained in a laboratory condition with the High-Order Test bench (HOT) at ESO Headquarters, we confirm our results with new measurements carried out with the SPHERE instrument during its final t...
Static stability analysis of a passive-active hybrid vibration isolator%磁悬浮主被动混合隔振器静稳定性分析
倪圆; 何琳; 帅长庚; 李彦
2015-01-01
Passive-active vibration isolator using maglev actuator is a elastic structure combining positive and negative stiffness. Stiffness model of the hybrid vibration isolator is established to solve the stability problem of the structure. According to virtual work principle, the stiffness principle determining the static stability of a elastic system is derived. This stiffness principle combining the stiffness model is used to ana-lyze the static stability of the hybrid vibration isolator. Theory and experimental results show that the stiff-ness of the hybrid vibration isolator is positive for working displace, and the isolator is stable.%磁悬浮主被动混合隔振器是一种正负刚度并联的弹性结构.针对该结构存在的稳定性问题,建立了某型磁悬浮主被动混合隔振器的刚度模型. 基于虚功原理,推导出判定弹性系统静稳定性的刚度准则. 运用该准则,结合混合隔振器的刚度模型分析了该主被动混合隔振器的静稳定性. 理论和实验结果表明,该混合隔振器在工作位移内,系统刚度为正,混合隔振器是静稳定的.
Statics and mechanics of structures
Krenk, Steen
2013-01-01
The statics and mechanics of structures form a core aspect of civil engineering. This book provides an introduction to the subject, starting from classic hand-calculation types of analysis and gradually advancing to a systematic form suitable for computer implementation. It starts with statically determinate structures in the form of trusses, beams and frames. Instability is discussed in the form of the column problem - both the ideal column and the imperfect column used in actual column design. The theory of statically indeterminate structures is then introduced, and the force and deformation methods are explained and illustrated. An important aspect of the book’s approach is the systematic development of the theory in a form suitable for computer implementation using finite elements. This development is supported by two small computer programs, MiniTruss and MiniFrame, which permit static analysis of trusses and frames, as well as linearized stability analysis. The book’s final section presents related ...
Relaxation properties in classical diamagnetism
Carati, A.; Benfenati, F.; Galgani, L.
2011-06-01
It is an old result of Bohr that, according to classical statistical mechanics, at equilibrium a system of electrons in a static magnetic field presents no magnetization. Thus a magnetization can occur only in an out of equilibrium state, such as that produced through the Foucault currents when a magnetic field is switched on. It was suggested by Bohr that, after the establishment of such a nonequilibrium state, the system of electrons would quickly relax back to equilibrium. In the present paper, we study numerically the relaxation to equilibrium in a modified Bohr model, which is mathematically equivalent to a billiard with obstacles, immersed in a magnetic field that is adiabatically switched on. We show that it is not guaranteed that equilibrium is attained within the typical time scales of microscopic dynamics. Depending on the values of the parameters, one has a relaxation either to equilibrium or to a diamagnetic (presumably metastable) state. The analogy with the relaxation properties in the Fermi Pasta Ulam problem is also pointed out.
Stability-Based Equivalent Static Wind Loads on Large-Span Snowy Roofs%基于稳定等效的覆雪屋盖静力风荷载计算方法
黄友钦; 林俊宏; 岳启哲; 傅继阳
2013-01-01
To avoid the dynamic instability of roofs in snowstorms,a method of stability-based equivalent static wind loads was presented.Snowdrifts on roofs are firstly simulated by the computational fluid dynamics (CFD) method.The state of dynamic instability of the snowy roof is determined by the Budiansky-Roth criterion.Then,the computational theory of stability-based equivalent static wind loads is constructed by referring to the principle of the gust loading factor method.Finally,the theory is applied to a real double-layer cylindrical reticulated shell.The results show that the snowy roof takes on evident instability under strong winds,and would become dynamically unstable when the wind velocity is 1.0 times the basic wind velocity.The critical wind velocity for wind-induced dynamic instability of snowy roofs,which is 35.8 m/s for the shell,can be obtained by static stability analysis using the proposed method.%为了避免屋盖结构在暴风雪中发生动力失稳,建立了基于稳定等效的静力风荷载计算方法.采用计算流体动力学方法模拟了屋面积雪漂移现象；根据Budiansky-Roth准则判定了覆雪屋盖的动力稳定性；借鉴阵风荷载因子法构建了基于稳定等效的静力风荷载计算方法；最后,对实际双层柱面网壳进行了动力稳定性设计.研究结果表明,强风下覆雪屋盖出现较为明显的失稳阶段,当风速为设计基准风速的1.0倍时,屋盖发生动力失稳,静力失稳计算可得临界风速为35.8 m/s,该结果可作为该屋盖设计的动力失稳临界风速.
Fleischmann, C.; Lieten, R. R.; Hermann, P.; Hönicke, P.; Beckhoff, B.; Seidel, F.; Richard, O.; Bender, H.; Shimura, Y.; Zaima, S.; Uchida, N.; Temst, K.; Vandervorst, W.; Vantomme, A.
2016-08-01
Strained Ge1-xSnx thin films have recently attracted a lot of attention as promising high mobility or light emitting materials for future micro- and optoelectronic devices. While they can be grown nowadays with high crystal quality, the mechanism by which strain energy is relieved upon thermal treatments remains speculative. To this end, we investigated the evolution (and the interplay) of composition, strain, and morphology of strained Ge0.94Sn0.06 films with temperature. We observed a diffusion-driven formation of Sn-enriched islands (and their self-organization) as well as surface depressions (pits), resulting in phase separation and (local) reduction in strain energy, respectively. Remarkably, these compositional and morphological instabilities were found to be the dominating mechanisms to relieve energy, implying that the relaxation via misfit generation and propagation is not intrinsic to compressively strained Ge0.94Sn0.06 films grown by molecular beam epitaxy.
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.
van Santen, G; Wierda, JMKH; Fidler, [No Value
1999-01-01
Objective. To determine whether the twitch force of the adductor pollicis remains stable when 0.1 Hz single twitch stimulation is started after stabilization of the thumb preload at a constant degree of thumb abduction; also to study any possible increase in twitch force before the onset of and afte
Fleischmann, C.; Lieten, R. R.; Shimura, Y.; Vandervorst, W. [Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium); imec, Kapeldreef 75, 3001 Leuven (Belgium); Hermann, P.; Hönicke, P.; Beckhoff, B. [Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin (Germany); Seidel, F. [Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium); imec, Kapeldreef 75, 3001 Leuven (Belgium); Institut für Elektronik-und Sensormaterialien, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 3, 09599 Freiberg (Germany); Richard, O.; Bender, H. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Zaima, S. [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Uchida, N. [Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba West SCR, 16-1 Onogawa, Tsukuba, Ibaraki 305-8569 (Japan); Temst, K.; Vantomme, A. [Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium)
2016-08-28
Strained Ge{sub 1-x}Sn{sub x} thin films have recently attracted a lot of attention as promising high mobility or light emitting materials for future micro- and optoelectronic devices. While they can be grown nowadays with high crystal quality, the mechanism by which strain energy is relieved upon thermal treatments remains speculative. To this end, we investigated the evolution (and the interplay) of composition, strain, and morphology of strained Ge{sub 0.94}Sn{sub 0.06} films with temperature. We observed a diffusion-driven formation of Sn-enriched islands (and their self-organization) as well as surface depressions (pits), resulting in phase separation and (local) reduction in strain energy, respectively. Remarkably, these compositional and morphological instabilities were found to be the dominating mechanisms to relieve energy, implying that the relaxation via misfit generation and propagation is not intrinsic to compressively strained Ge{sub 0.94}Sn{sub 0.06} films grown by molecular beam epitaxy.
Jackson, Charles M., Jr.; Harris, Roy V., Jr.
1960-01-01
An investigation has been made in the Langley 4- by 4-foot supersonic pressure tunnel at a Mach number of 1.99 to determine the longitudinal stability and control characteristics of a reentry model consisting of a lenticular-shaped body with two fin configurations (horizontal fins with end plates). Effects of deflecting the larger size fins as pitch-control surfaces were also investigated. The results indicate that the body alone was unstable from an angle of attack of 0 deg to about 55 deg where it became stable and remained so to 90 deg. The addition of fins provided positive longitudinal stability throughout the angle-of-attack range and increased the lift-drag ratio of the configuration. Reducing the horizontal-fin area at the inboard trailing edge of the fin had only a small effect on the aerodynamic characteristics of the vehicle for the condition of no fin deflection. Deflecting the fins, appeared to be an effective means of pitch control and had only a small effect on lift-drag ratio.
Plasma Relaxation Dynamics Moderated by Current Sheets
Dewar, Robert; Bhattacharjee, Amitava; Yoshida, Zensho
2014-10-01
Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor-relaxed equilibrium model all these constraints are relaxed save for global magnetic flux and helicity. A Lagrangian is presented that leads to a new variational formulation of magnetized fluid dynamics, relaxed MHD (RxMHD), all static solutions of which are Taylor equilibrium states. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-relaxed MHD (MRxMHD), is developed. These concepts are illustrated using a simple two-region slab model similar to that proposed by Hahm and Kulsrud--the formation of an initial shielding current sheet after perturbation by boundary rippling is calculated using MRxMHD and the final island state, after the current sheet has relaxed through a reconnection sequence, is calculated using RxMHD. Australian Research Council Grant DP110102881.
Dalibor Petrović
2006-07-01
Full Text Available U ovom radu opisan je softver za proračun uzdužne statičke stabilnosti i upravljivosti aviona za osnovnu obuku pilota. Softver je urađen sa numerom da konstruktorima omogući brzo i lako dobijanje potrebnih rezultata vezanih za stabilnost i upravljivost kod preliminarnih proračuna vezanih za ovu vrstu aviona. Program je urađen na osnovu analize velikog broja aviona iz ove klase, a njegova tačnost je testirana na avionu "Lasta". Rezultati koji su dobijeni ovim softverom bili su više od zadovoljavajućih, s obzirom na to da se radi o programu koji bi se koristio za preliminarni proračun. / This document introduced software for calculation of an axial static stability and management of airplanes for basic pilot training. The purpose of this software is to provide a quicker and an easier way of getting results regarding preliminary calculation of stability and management for these types of airplanes. The program is based upon analysis of data gathered from a large number of tested airplanes of this class. The accuracy of the program has been tested on the airplane type 'Lasta' and results were more than satisfying, especially regarding the fact that the program is meant to be used for preliminary calculation.
Chabaud-Reytier, M
1999-07-01
The heat affected zone (HAZ) of titanium stabilised austenitic stainless steel welds (AISI 321) may exhibit a serious form of intercrystalline cracking during service at high temperature. This type of cracking, called 'stress relief cracking', is known to be due to work hardening but also to ageing: a fine and abundant intragranular Ti(C,N) precipitation appears near the fusion line and modifies the mechanical behaviour of the HAZ. This study aims to better know the accused mechanism and to succeed in estimating the risk of such cracking in welded junctions of 321 stainless steel. To analyse this embrittlement mechanism, and to assess the lifetime of real components, different HAZ are simulated by heat treatments applied to the base material which is submitted to various cold rolling and ageing conditions in order to reproduce the HAZ microstructure. Then, we study the effects of work hardening and ageing on the titanium carbide precipitation, on the mechanical (tensile and creep) behaviour of the resulting material and on its stress relief cracking sensitivity. It is shown that work hardening is the main parameter of the mechanism and that ageing do not favour crack initiation although it leads to titanium carbide precipitation. The role of this precipitation is also discussed. Moreover, a creep damage model is identified by a local approach to fracture. Materials sensitive to stress relief cracking are selected. Then, creep tests are carried out on notched bars in order to quantify the intergranular damage of these different materials; afterwards, these measurements are combined with calculated mechanical fields. Finally, it is shown that the model gives good results to assess crack initiation for a compact tension (CT) specimen during relaxation tests, as well as for a notched tubular specimen tested at 600 deg. C under a steady torque. (author)
Bisplinghoff, Raymond L; Pian, Theodore HH
2014-01-01
Profusely illustrated exposition of fundamentals of solid mechanics and principles of mechanics, statics, and simple statically indeterminate systems. Covers strain and stress in three-dimensional solids, elementary elasticity, energy principles in solid continuum, and more. 1965 edition.
Nada S. Abdelwahab
2017-05-01
Full Text Available The present work concerns with the development of stability indicating the RP-HPLC method for simultaneous determination of guaifenesin (GUF and pseudoephedrine hydrochloride (PSH in the presence of guaifenesin related substance (Guaiacol. GUC, and in the presence of syrup excepients with minimum sample pre-treatment. In the developed RP-HPLC method efficient chromatographic separation was achieved for GUF, PSH, GUC and syrup excepients using ODS column as a stationary phase and methanol: water (50:50, v/v, pH = 4 with orthophosphoric acid as a mobile phase with a flow rate of 1 mL min−1 and UV detection at 210 nm. The chromatographic run time was approximately 10 min. Calibration curves were drawn relating the integrated area under peak to the corresponding concentrations of PSH, GUF and GUC in the range of 1–8, 1–20, 0.4–8 μg mL−1, respectively. The developed method has been validated and met the requirements delineated by ICH guidelines with respect to linearity, accuracy, precision, specificity and robustness. The validated method was successfully applied for determination of the studied drugs in triaminic chest congestion® syrup; moreover its results were statistically compared with those obtained by the official method and no significant difference was found between them.
Relaxation Techniques for Health
... R S T U V W X Y Z Relaxation Techniques for Health Share: On This Page What’s the ... Bottom Line? How much do we know about relaxation techniques? A substantial amount of research has been done ...
Gray, W J; Midgley, J E
1972-08-01
The biosynthesis and stability of various RNA fractions was studied in RC(str) and RC(rel) multiple amino acid auxotrophs of Escherichia coli. In conditions of amino acid deprivation, RC(str) mutants were labelled with exogenous nucleotide bases at less than 1% of the rate found in cultures growing normally in supplemented media. Studies by DNA-RNA hybridization and by other methods showed that, during a period of amino acid withdrawal, not more than 60-70% of the labelled RNA formed in RC(str) mutants had the characteristics of mRNA. Evidence was obtained for some degradation of newly formed 16S and 23S rRNA species to heterogeneous material of lower molecular weight. This led to overestimations of the mRNA content of rapidly labelled RNA from such methods as simple examination of sucrose-density-gradient profiles. In RC(rel) strains the absolute and relative rates of synthesis of the various RNA fractions were not greatly affected. However, the stability of about half of the mRNA fraction was increased in RC(rel) strains during amino acid starvation, giving kinetics of mRNA labelling and turnover that were identical with those found in either RC(str) or RC(rel) strains inhibited by high concentrations of chloramphenicol. Coincidence hybridization techniques showed that the mRNA content of amino acid-starved RC(str) auxotrophs was unchanged from that found in normally growing cells. In contrast, RC(rel) strains deprived of amino acids increased their mRNA content about threefold. In such cultures the mRNA content of accumulating newly formed RNA was a constant 16% by wt.
Kobayashi, M; Irisawa, H
1961-10-27
The latent period of relaxation of molluscan myocardium due to anodal current is much longer than that of contraction. Although the rate and the grade of relaxation are intimately related to both the stimulus condition and the muscle tension, the latent period of relaxation remains constant, except when the temperature of the bathing fluid is changed.
The in Vivo Stability Study of Normal Knee under Static Load%正常膝关节静态加载在体稳定性研究
李凭跃; 尹庆水; 黄华扬; 李鉴轶; 沈洪园; 王泽锦; 王庆
2011-01-01
目的 对正常膝关节进行静态加载在体稳定性研究.方法 对8例志愿者,由加载架上对膝关节在屈曲0°、30°、60°和90°时分别进行134 N前、后加载.采集各角度相互垂直的2D图像,与CT(3D)图像在虚拟X线投射系统进行2D/3D图像配准,还原膝关节不同角度时的股骨和胫骨相对3D位置关系,获得膝关节静态加载在体稳定性数据并进行统计学分析.结果 随屈曲角度的增大,胫骨前移和前交叉韧带(ACL)长度的增加在30°时最大,胫骨后移和后交叉韧带(PCL)长度增加在0°最大,各角度间均有统计学差异(P＜0.05)；内外侧副韧带各角度间及前后加载间均无统计学差异.结论 通过2D/3D图像配准技术可以实现对膝关节静态加载的在体稳定性分析,并获得不同角度各静态加载在体稳定性参数.%Objective To study the in vivo stability of normal knee under 134 N pre/post loading by the method of 2D/3D registration technique. Methods Eight healthy volunteers were captured CT (3D) images and 2 orthogonal images of the knee at 0°, 30°, 60°, and 90° under 134 N Pre/Post loading. These orthogonal images were used to recreate the in vivo knee positions at each of the targeted flexion angles by the method of 2D/3D registration. The tibial translation and ligament length data of the knee could be obtained and analyzed. Results With the flexion angle increased, the length of the ACL increasing and anterior tibial translation got maximum at 30°, the length of the increasing PCL and posterior tibial translation got maximum at 0°, there were significant differences between each angle (P <0.05), but there were no significant differences between different angle and pre/post loading according MCL and LCL. Conclusion The in vivo parameters of the normal knee under 134 N pre/post loading can be obtained by the method of 2D/3D registration technique.
Arresting relaxation in Pickering Emulsions
Atherton, Tim; Burke, Chris
2015-03-01
Pickering emulsions consist of droplets of one fluid dispersed in a host fluid and stabilized by colloidal particles absorbed at the fluid-fluid interface. Everyday materials such as crude oil and food products like salad dressing are examples of these materials. Particles can stabilize non spherical droplet shapes in these emulsions through the following sequence: first, an isolated droplet is deformed, e.g. by an electric field, increasing the surface area above the equilibrium value; additional particles are then adsorbed to the interface reducing the surface tension. The droplet is then allowed to relax toward a sphere. If more particles were adsorbed than can be accommodated by the surface area of the spherical ground state, relaxation of the droplet is arrested at some non-spherical shape. Because the energetic cost of removing adsorbed colloids exceeds the interfacial driving force, these configurations can remain stable over long timescales. In this presentation, we present a computational study of the ordering present in anisotropic droplets produced through the mechanism of arrested relaxation and discuss the interplay between the geometry of the droplet, the dynamical process that produced it, and the structure of the defects observed.
李苏川; 吕智林; 谭颖
2016-01-01
为了深入研究孤立微网的静态电压稳定性问题，将分岔理论应用于微网静态电压稳定性分析研究。以鞍结分岔点作为电压稳定临界点，采用连续潮流( CPF)算法对四节点小型孤立微网进行电压稳定性分析，追踪出该系统的PU曲线，并根据特征根来判断该曲线上是否存在鞍结分岔点。分别计算出含SVC和不含SVC系统的电压稳定极限，得出负荷节点处电压稳定裕度。由实验结果可以看出，随着负荷参数的不断增大，负荷所需功率和发电机的输出功率也会随之增大，当达到它的传输极限时就会产生鞍结分岔现象，从而导致系统电压出现跌落甚至崩溃的现象。结果表明，利用上述方法可以有效地计算出孤立微网的电压稳定极限，并且使用SVC控制器可以提高系统电压稳定性。%In order to study the problem of static voltage stability of isolated micro-grid, the bifurca-tion theory is applied. The saddle node bifurcation point is used as the voltage collapse critical point while using continuous power flow ( CPF) algorithm to analyze the voltage stability of a small isolated micro-grid with four nodes. Then by tracing the PU curve of the system and according to the charac-teristics of the root the saddle node bifurcation point in the curve is determined. The stability limit of the SVC and non SVC system voltage are calculated respectively to obtain the voltage stability margin of load node. The experiments show that with the increase of the load parameters, the required pow-er of the load and the output power of the generator will increase. Then the saddle node bifurcation will occur when the transmission limit which causes the system voltage to fall or collapse. The results of simulations show that the voltage stability limit of isolated micro grid can be calculated by using this method. And by using SVC controller the stability of system voltage can be improved.
Static electromagnetic frequency changers
Rozhanskii, L L
1963-01-01
Static Electromagnetic Frequency Changers is about the theory, design, construction, and applications of static electromagnetic frequency changers, devices that used for multiplication or division of alternating current frequency. It is originally published in the Russian language. This book is organized into five chapters. The first three chapters introduce the readers to the principles of operation, the construction, and the potential applications of static electromagnetic frequency changers and to the principles of their design. The two concluding chapters use some hitherto unpublished work
Motional Spin Relaxation in Large Electric Fields
Schmid, Riccardo; Filippone, B W
2008-01-01
We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and $^{3}\\mathrm{He}$ atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional $v\\times E$ magnetic fields. Particle motion in an electric field creates a motional $v\\times E$ magnetic field, which when combined with collisions, produces variations of the total magnetic field and results in spin relaxation of neutron and $^{3}\\mathrm{He}$ samples. The spin relaxation times $T_{1}$ (longitudinal) and $T_{2}$ (transverse) of spin-polarized UCN and $^{3}\\mathrm{He}$ atoms are important considerations in a new search for the neutron Electric Dipole Moment at the SNS \\emph{nEDM} experiment. We use a Monte Carlo approach to simulate the relaxation of spins due to the motional $v\\times E$ field for UCN and for $^{3}\\mathrm{He}$ atoms at temperatures below $600 \\mathrm{mK}$. We find the relaxation times for the neutron due to the $v\\times E$ effect to be long compared to the neutron lifetime, ...
Doppler effect induced spin relaxation boom
Zhao, Xinyu; Huang, Peihao; Hu, Xuedong
2016-03-01
We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures.
Spivak, A.V., E-mail: spivak@iem.ac.ru [Institute of Experimental Mineralogy of the Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation); Litvin, Yu.A. [Institute of Experimental Mineralogy of the Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation); Ovsyannikov, S.V. [Bayerishes Geoinstitut, University of Bayreuth, Bayreuth (Germany); Dubrovinskaia, N.A. [Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth, Bayreuth (Germany); Dubrovinsky, L.S. [Bayerishes Geoinstitut, University of Bayreuth, Bayreuth (Germany)
2012-07-15
Melting of calcium carbonate Ca{sup 13}CO{sub 3}, stability of the melt and its decomposition were studied in static high pressure experiments at pressures of 11-43 GPa and temperatures of 1600-3900 K using diamond anvil cell technique with laser heating. We observed formation of {sup 13}C-graphite (below 16 GPa) and {sup 13}C-diamond (between 16 and 43 GPa) on decomposition of the Ca{sup 13}CO{sub 3} melt at temperatures above 3400 K. At temperatures below 3400 K congruent melting of calcium carbonate was confirmed. The experimental results were applied to construction of the phase diagram of CaCO{sub 3} up to 43 GPa and 3900 K focusing at the melting curve of calcium carbonate and the decomposition phase boundary of CaCO{sub 3} melt. - Graphical abstract: Highlights: Black-Right-Pointing-Pointer Phase states of CaCO{sub 3} were studied at P=11-43 GPa and T=1600-3900 K. Black-Right-Pointing-Pointer {sup 13}C-diamond easily crystallizes in carbonate-carbon (Ca{sup 13}CO{sub 3-}{sup 13}C-graphite) melt-solutions. Black-Right-Pointing-Pointer Ca-carbonate melts congruently that was observed in experiments in DAC with laser heating. Black-Right-Pointing-Pointer Decomposition of CaCO{sub 3} melt, indicated by formation of graphite and/or diamond. Black-Right-Pointing-Pointer Decomposition of CaCO{sub 3} was observed at temperatures above 3400 K in the pressure interval studied.
Noninteracting control of nonlinear systems based on relaxed control
Jayawardhana, B.
2010-01-01
In this paper, we propose methodology to solve noninteracting control problem for general nonlinear systems based on the relaxed control technique proposed by Artstein. For a class of nonlinear systems which cannot be stabilized by smooth feedback, a state-feedback relaxed control can be designed to
Rectifier cabinet static breaker
Costantino, Jr, Roger A.; Gliebe, Ronald J.
1992-09-01
A rectifier cabinet static breaker replaces a blocking diode pair with an SCR and the installation of a power transistor in parallel with the latch contactor to commutate the SCR to the off state. The SCR serves as a static breaker with fast turnoff capability providing an alternative way of achieving reactor scram in addition to performing the function of the replaced blocking diodes. The control circuitry for the rectifier cabinet static breaker includes on-line test capability and an LED indicator light to denote successful test completion. Current limit circuitry provides high-speed protection in the event of overload.
Jeletic, Matthew; Lin, Po-Heng; Le Roy, Jennifer J; Korobkov, Ilia; Gorelsky, Serge I; Murugesu, Muralee
2011-12-07
A dysprosium(III) sandwich complex, [Dy(III)(COT″)(2)Li(THF)(DME)], was synthesized using 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion (COT″). The complex behaves as a single-ion magnet and demonstrates unusual multiple relaxation modes. The observed relaxation pathways strongly depend on the applied static dc fields.
Soares, Domingos Savio
2012-01-01
Einstein's static model is the first relativistic cosmological model. The model is static, finite and of spherical spatial symmetry. I use the solution of Einstein's field equations in a homogeneous and isotropic universe -- Friedmann's equation -- to calculate the radius of curvature of the model (also known as "Einstein's universe"). Furthermore, I show, using a Newtonian analogy, the model's mostly known feature, namely, its instability under small perturbations on the state of equilibrium.
Static Analysis Numerical Algorithms
2016-04-01
STATIC ANALYSIS OF NUMERICAL ALGORITHMS KESTREL TECHNOLOGY, LLC APRIL 2016 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE; DISTRIBUTION...3. DATES COVERED (From - To) NOV 2013 – NOV 2015 4. TITLE AND SUBTITLE STATIC ANALYSIS OF NUMERICAL ALGORITHMS 5a. CONTRACT NUMBER FA8750-14-C... algorithms , linear digital filters and integrating accumulators, modifying existing versions of Honeywell’s HiLiTE model-based development system and
许正勇; 张先熠
2016-01-01
and cross-sectional areas by using image processing software ImageJ, and performed an interclass correlation coefficient (ICC) analysis on two sets of measurement data by using data processing software SPSS, so as to verify the repeatability of this test method; in the mean time, the authors also measured eyes closed single leg standing time in order to evaluate balance stability, analyzed the Pearson coef-ficients of correlation between eyes closed single leg standing time and the morphologies of the four foot intrinsic muscles, and probed into the effects of foot intrinsic muscle morphology on static balance ability. The authors re-vealed the following findings: most ICC values of two sets measurement values of foot intrinsic muscle thicknesses and cross-sectional areas measured by using ultrasonic technology were greater than 0.9, which means that the re-peatability of this test method is good; the thickness of abductor hallucis and the cross-sectional areas of flexor digitorum brevis and abductor digiti minimi were significantly correlative with eyes closed single leg standing time, while the cross-sectional area of abductor hallucis was very significant correlative with eyes closed single leg standing time; the larger the cross-sectional area of foot intrinsic muscles, the longer the eyes closed single leg standing time. The said findings indicate the followings: the reliability of measuring foot intrinsic muscle morphol-ogy by using type B ultrasonic technology is good; foot intrinsic muscle morphology will affect human body static balance control, its function on foot core area stability should not be neglected.
Dynamics of cosmological relaxation after reheating
Choi, Kiwoon; Sekiguchi, Toyokazu
2016-01-01
We examine if the cosmological relaxation mechanism, which was proposed recently as a new solution to the hierarchy problem, can be compatible with high reheating temperature well above the weak scale. As the barrier potential disappears at high temperature, the relaxion rolls down further after the reheating, which may ruin the successful implementation of the relaxation mechanism. It is noted that if the relaxion is coupled to a dark gauge boson, the new frictional force arising from dark gauge boson production can efficiently slow down the relaxion motion, which allows the relaxion to be stabilized after the electroweak phase transition for a wide range of model parameters, while satisfying the known observational constraints.
Indentation load relaxation test
Hannula, S.P.; Stone, D.; Li, C.Y. (Cornell Univ., Ithaca, NY (USA))
Most of the models that are used to describe the nonelastic behavior of materials utilize stress-strain rate relations which can be obtained by a load relaxation test. The conventional load relaxation test, however, cannot be performed if the volume of the material to be tested is very small. For such applications the indentation type of test offers an attractive means of obtaining data necessary for materials characterization. In this work the feasibility of the indentation load relaxation test is studied. Experimental techniques are described together with results on Al, Cu and 316 SS. These results are compared to those of conventional uniaxial load relaxation tests, and the conversion of the load-indentation rate data into the stress-strain rate data is discussed.
Relaxation techniques for stress
... problems such as high blood pressure, stomachaches, headaches, anxiety, and depression. Using relaxation techniques can help you feel calm. These exercises can also help you manage stress and ease the effects of stress on your body.
Perturbations and quantum relaxation
Kandhadai, Adithya
2016-01-01
We investigate whether small perturbations can cause relaxation to quantum equilibrium over very long timescales. We consider in particular a two-dimensional harmonic oscillator, which can serve as a model of a field mode on expanding space. We assume an initial wave function with small perturbations to the ground state. We present evidence that the trajectories are highly confined so as to preclude relaxation to equilibrium even over very long timescales. Cosmological implications are briefly discussed.
Observing the Forces Involved in Static Friction under Static Situations
Kaplan, Daniel
2013-01-01
Static friction is an important concept in introductory physics. Later in the year students apply their understanding of static friction under more complex conditions of static equilibrium. Traditional lab demonstrations in this case involve exceeding of the maximum level of static friction, resulting in the "onset of motion." (Contains…
Compaction and relaxation of biofilms
Valladares Linares, R.
2015-06-18
Operation of membrane systems for water treatment can be seriously hampered by biofouling. A better characterization of biofilms in membrane systems and their impact on membrane performance may help to develop effective biofouling control strategies. The objective of this study was to determine the occurrence, extent and timescale of biofilm compaction and relaxation (decompaction), caused by permeate flux variations. The impact of permeate flux changes on biofilm thickness, structure and stiffness was investigated in situ and non-destructively with optical coherence tomography using membrane fouling monitors operated at a constant crossflow velocity of 0.1 m s−1 with permeate production. The permeate flux was varied sequentially from 20 to 60 and back to 20 L m−2 h−1. The study showed that the average biofilm thickness on the membrane decreased after elevating the permeate flux from 20 to 60 L m−2 h−1 while the biofilm thickness increased again after restoring the original flux of 20 L m−2 h−1, indicating the occurrence of biofilm compaction and relaxation. Within a few seconds after the flux change, the biofilm thickness was changed and stabilized, biofilm compaction occurred faster than the relaxation after restoring the original permeate flux. The initial biofilm parameters were not fully reinstated: the biofilm thickness was reduced by 21%, biofilm stiffness had increased and the hydraulic biofilm resistance was elevated by 16%. Biofilm thickness was related to the hydraulic biofilm resistance. Membrane performance losses are related to the biofilm thickness, density and morphology, which are influenced by (variations in) hydraulic conditions. A (temporarily) permeate flux increase caused biofilm compaction, together with membrane performance losses. The impact of biofilms on membrane performance can be influenced (increased and reduced) by operational parameters. The article shows that a (temporary) pressure increase leads to more
Danvy, Olivier; Damian, Daniel
2001-01-01
Starting from an operational specification of a translation from a structured to an unstructured imperative language, we point out how a compositional and context-insensitive translation gives rise to static chains of jumps. Taking an inspiration from the notion of continuation, we state a new...... compositional and context-sensitive specification that provably gives rise to no static chains of jumps, no redundant labels, and no unused labels. It is defined with one inference rule per syntactic construct and operates in linear time and space on the size of the source program (indeed it operates in one...
Messerle, H K; Declaris, Nicholas
2013-01-01
Energy Conversion Statics deals with equilibrium situations and processes linking equilibrium states. A development of the basic theory of energy conversion statics and its applications is presented. In the applications the emphasis is on processes involving electrical energy. The text commences by introducing the general concept of energy with a survey of primary and secondary energy forms, their availability, and use. The second chapter presents the basic laws of energy conversion. Four postulates defining the overall range of applicability of the general theory are set out, demonstrating th
Robot-Crawler: Statically Balanced Gaits
S. Parasuraman
2012-12-01
Full Text Available This paper presents a new statically balanced walking technique for a robot‐crawler. The gait design and the control of the robot crawler aim to achieve stability while walking. This statically balanced gait has to be designed in a different fashion to a wheeled robot, as there are discrete changes in the support of the robot when its legs are lifted or placed on the ground. The stability of the robot depends on how the legs are positioned relative to the body and also on the sequence and timing with which the legs are lifted and placed. In order to reduce the risk of stability loss while walking, a measure for the robot stability (so‐called stability margin is typically used in the gait and motion planning. In this paper different biological behaviours of four‐legged animals are studied and mapped on a quad-legrobot‐crawler. Experiments were carried out on the forward walking gaits of lizards and horses. Based on these results, the stability margins of different gaits are discussed and compared.
Static shapes of levitated viscous drops
Duchemin, L.; Lister, J. R.; Lange, U.
2005-06-01
We consider the levitation of a drop of molten glass above a spherical porous mould, through which air is injected with constant velocity. The glass is assumed to be sufficiently viscous compared to air that motion in the drop is negligible. Thus static equilibrium shapes are determined by the coupling between the lubricating pressure in the supporting air cushion and the Young-Laplace equation. The upper surface of the drop is under constant atmospheric pressure; the static shape of the lower surface of the drop is computed using lubrication theory for the thin air film. Matching of the sessile curvature of the upper surface to the curvature of the mould gives rise to a series of capillary "brim" waves near the edge of the drop which scale with powers of a modified capillary number. Several branches of static solutions are found, such that there are multiple solutions for some drop volumes, but no physically reasonable solutions for other drop volumes. Comparison with experiments and full Navier-Stokes calculations suggests that the stability of the process can be predicted from the solution branches for the static shapes, and related to the persistence of brim waves to the centre of the drop. This suggestion remains to be confirmed by a formal stability analysis.
Explosions and static electricity
Jonassen, Niels M
1995-01-01
The paper deals with the problem of electrostatic discharges as causes of ignition of vapor/gas and dust/gas mixtures. A series of examples of static-caused explosions will be discussed. The concepts of explosion limits, the incendiveness of various discharge types and safe voltages are explained...
Naab, Laurie; Henry, David
2009-01-01
Using Wiggins and McTighe's (1998) concept of Big Ideas, the authors planned and designed an electricity investigation to address common student misconceptions about static electricity. With Styrofoam plates and transparent tape, elementary students investigated many properties of electrically charged and uncharged objects in a 5E learning cycle…
Static Gravitational Global Monopoles
Liebling, S L
2000-01-01
Static solutions in spherical symmetry are found for gravitating global monopoles. Regular solutions lacking a horizon are found for $\\eta \\sqrt{3/8\\pi} \\approx 0.3455$ is consistent with findings that topological inflation begins at $\\eta \\approx 0.33$.
Molecular Relaxation in Liquids
Bagchi, Biman
2012-01-01
This book brings together many different relaxation phenomena in liquids under a common umbrella and provides a unified view of apparently diverse phenomena. It aligns recent experimental results obtained with modern techniques with recent theoretical developments. Such close interaction between experiment and theory in this area goes back to the works of Einstein, Smoluchowski, Kramers' and de Gennes. Development of ultrafast laser spectroscopy recently allowed study of various relaxation processes directly in the time domain, with time scales going down to picosecond (ps) and femtosecond (fs
Dynamic isotope effects on relaxation of quadrupolar nuclei in 12 simple organic molecules
毛希安; andM.Holz
1995-01-01
Dynamic isotope effects on relaxation rate of quadrupolar nuclei are preliminarily reported. The relaxation rates of 17O and 14N in 12 simple organic molecules and their 18 corresponding deuterated species have been systematically measured. The principal components of the molecular inertia tensors have been calculated. The results show that there is an intrinsic correlation between the dynamic isotope effects of the relaxation rate and the static isotope effects of the molecular inertia. The concepts of molecular collision frequency and translation-rotation coupling have been introduced into the NMR relaxation theory. Therefore, a reasonable explanation of the experimental results has been given.
Jernell, Lloyd S.
1961-01-01
An investigation w a s made i n the Langley Unitary Plan wind tunnel o determine the effects of fin area and the effects of antennas and w iring tunnels on the static longitudinal and lateral stability of a 0 .10- scale model of a three- stage configuration of the Scout vehicle. The tests were performed at Mach numbers of 2.29, 2.96, 3.96, and 4. 65 6 and at Reynolds numbers of about 3.5 X 10 per foot.
Lu, Zijie; Manias, Evangelos; MacDonald, Digby D.; Lanagan, Michael
2009-10-01
Dielectric spectra of dimethyl sulfoxide (DMSO)/water mixtures, over the entire concentration range, have been measured using the transmission line method at frequencies from 45 MHz to 26 GHz and at temperatures of 298-318 K. The relaxation times of the mixtures show a maximum at an intermediate molar fraction of DMSO. The specific structure of mixtures in different concentration regions was determined by the dielectric relaxation dynamics, obtained from the effect of temperature on the relaxation time. A water structure "breaking effect" is observed in dilute aqueous solutions. The average number of hydrogen bonds per water molecule in these mixtures is found to be reduced compared to pure water. The increase in the dielectric relaxation time in DMSO/water mixtures is attributed to the spatial (steric) constraints of DMSO molecules on the hydrogen-bond network, rather than being due to hydrophobic hydration of the methyl groups. The interaction between water and DMSO by hydrogen bonding reaches a maximum at a DMSO molar fraction of 0.33, reflected by the maximum activation enthalpy for dielectric relaxation in this concentration, suggesting the formation of a stoichiometric compound, H2O-DMSO-H2O. In highly concentrated solutions, negative activation entropies are observed, indicating the presence of aggregates of DMSO molecules. A distinct antiparallel arrangement of dipoles is obtained for neat DMSO in the liquid state according to the Kirkwood correlation factor (gK = 0.5), calculated from the static permittivity. The similarity of the dielectric behavior of pure DMSO and DMSO-rich mixtures suggests that dipole-dipole interactions contribute significantly to the rotational relaxation process in these solutions.
Microprocessor controlled static converter
Stefan Szabo
2005-10-01
Full Text Available This paper wants to demonstrate a way of implementing a microcontroller into an DC motor speed control loop. The static power converter is a fully controlled rectifier bridge, using standard SCR's. The bridge's control signals are supplied by the microcontroller and are phase-angle or burst types. The automation loop contains a software PI-style regulator. All the experimental results shows that this aproach is flexibile enough to be used on a large scale.
Nomura, Yasunori
2012-01-01
We consider the multiverse in the intrinsically quantum mechanical framework recently proposed in Refs. [1,2]. By requiring that the principles of quantum mechanics are universally valid and that physical predictions do not depend on the reference frame one chooses to describe the multiverse, we find that the multiverse state must be static---in particular, the multiverse does not have a beginning or end. We argue that, despite its naive appearance, this does not contradict observation, inclu...
Open static Chaplygin universe
Khalatnikov, I M
2003-01-01
We apply the qualitative theory of dynamical systems to the study of the Chaplygin gas cosmological model. In difference to earlier works devoted to this model we give up sign restrictions on the choice of the sign of the energy density and on the parameters characterising initial conditions for a cosmological evolution. It appears that exists a static stable open universe filled with the Chaplygin gas. Besides exist universes where the acoustic waves have a velocity exceeding that of light in the vacuum.
... For Consumers Consumer Information by Audience For Women Hair Dye and Hair Relaxers Share Tweet Linkedin Pin it More sharing ... products. If you have a bad reaction to hair dyes and relaxers, you should: Stop using the ...
Oreste, Pierpaolo; Soldano, Silvia
2012-12-01
The problem of the stability of "ravanetos" (debris piles of mining waste material extracted from the Apuan Alps, Italy) is very relevant, because of the consequences a landslide would have on the people and the existing civil infrastructures throughout the territory. In this work, the stability of two ravanetos that can be considered as representative of those in the Carrara area has been studied: the Polvaccio ravaneto, a recent type of debris pile and the Torrione-Tecchione, an old debris pile at present undergoing re-naturalisation. The study using the LEM (Limit Equilibrium Method) in a static and pseudo-static field, has made it possible to first carry out a back-analysis to define the most probable apparent cohesion and friction angle values of the material that makes up the ravanetos. Subsequently, it was possible to determine the intensity of the seismic wave that would be able to lead the two ravanetos to limit stability conditions and to determine the probability of such a seismic wave occurring in the next 50 years. A more accurate analysis, carried out with a numerical method in the dynamic field, of the most critical condition (the Polvaccio ravaneto) has led to more conservative results (higher safety factors) than those obtained with the LEM. This result allows us to reveal how the LEM can be considered a cautionary instrument to judge the stability of debris piles during a seismic event and that the likelihood of a landslide occurring in the two studied representative ravanetos over the next 50 years is very slim.
Control of Transport-barrier relaxations by Resonant Magnetic Perturbations
Leconte, M; Garbet, X; Benkadda, S
2009-01-01
Transport-barrier relaxation oscillations in the presence of resonant magnetic perturbations are investigated using three-dimensional global fluid turbulence simulations from first principles at the edge of a tokamak. It is shown that resonant magnetic perturbations have a stabilizing effect on these relaxation oscillations and that this effect is due mainly to a modification of the pressure profile linked to the presence of both residual residual magnetic island chains and a stochastic layer.
Kinetic Actviation Relaxation Technique
Béland, Laurent Karim; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand
2011-01-01
We present a detailed description of the kinetic Activation-Relaxation Technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si, self-interstitial diffusion in Fe and structural relaxation in amorphous silicon.
The β relaxation in metallic glasses: an overview
Hai-Bin Yu
2013-05-01
Full Text Available Metallic glasses, combining metallic bonding and disordered atomic structures, are at the cutting edge of metallic materials research. Recent advances in this field have revealed that many key questions in glassy physics are inherently connected to one important relaxation mode: the so-called secondary (β relaxation. Here, in metallic glasses, we review the features of β relaxations and their relations to other processes and properties. Special emphasis is put on their current roles and future promise in understanding the glass transition phenomenon, mechanical properties and mechanisms of plastic deformation, diffusion, physical aging, as well as the stability and crystallization of metallic glasses.
Nonlinear fractional relaxation
A Tofighi
2012-04-01
We deﬁne a nonlinear model for fractional relaxation phenomena. We use -expansion method to analyse this model. By studying the fundamental solutions of this model we ﬁnd that when → 0 the model exhibits a fast decay rate and when → ∞ the model exhibits a power-law decay. By analysing the frequency response we ﬁnd a logarithmic enhancement for the relative ratio of susceptibility.
Nielsen, Christoffer Rosenkilde; Nielson, Hanne Riis
2006-01-01
operation blinding. In this paper we study the theoretical foundations for one of the successful approaches to validating cryptographic protocols and we extend it to handle the blinding primitive. Our static analysis approach is based on Flow Logic; this gives us a clean separation between the specification...... of the analysis and its realisation in an automatic tool. We concentrate on the former in the present paper and provide the semantic foundation for our analysis of protocols using blinding - also in the presence of malicious attackers....
Tishin, A.M.; Spichkin, Yu.I.; Bohr, Jakob
1999-01-01
In this chapter we shall consider the properties of lanthanide metals, their alloys and compounds which can be studied using static and alternating mechanical stresses. The main attention will be paid to the effects related to magnetoelastic interactions. These interactions in magnetic materials...... to the appearance of anomalies in elastic constants, as well as to additional damping of sound oscillations in the lanthanide materials. The importance of understanding the nature of magnetoelastic interactions and related effects arises from the scientific desire to gather a better knowledge of magnetism, as well...
Model Checking as Static Analysis
Zhang, Fuyuan
Both model checking and static analysis are prominent approaches to detecting software errors. Model Checking is a successful formal method for verifying properties specified in temporal logics with respect to transition systems. Static analysis is also a powerful method for validating program...... properties which can predict safe approximations to program behaviors. In this thesis, we have developed several static analysis based techniques to solve model checking problems, aiming at showing the link between static analysis and model checking. We focus on logical approaches to static analysis......-calculus can be encoded as the intended model of SFP. Our research results have strengthened the link between model checking and static analysis. This provides a theoretical foundation for developing a unied tool for both model checking and static analysis techniques....
Jian Zuo; Yinhong Li; Dongyuan Shi; Xianzhong Duan
2017-01-01
The potential of utilizing doubly-fed induction generator (DFIG)-based wind farms to improve power system damping performance and to enhance small signal stability has been proposed by many researchers...
Quantum singularities in static and conformally static space-times
Konkowski, D A; 10.1142/S0217751X11054334
2011-01-01
The definition of quantum singularity is extended from static space-times to conformally static space-times. After the usual definitions of classical and quantum singularities are reviewed, examples of quantum singularities in static space-times are given. These include asymptotically power-law space-times, space-times with diverging higher-order differential invariants, and a space-time with a 2-sphere singularity. The theory behind quantum singularities in conformally static space-times is followed by an example, a Friedmann-Robertson-Walker space-time with cosmic string. The paper concludes by discussing areas of future research.
李永梅; 胡琨; 张微敬; 李运运
2015-01-01
To study the effect on the static performance of single-layer latticed shells under earthquake damage, based on the material constructive relationship considering damage cumulative effect, the dynamic stable analysis is first carried out for a K8 type and single-layer latticed shell through the incremental dynamic analysis ( IDA) method, in which B-R kinetic criterion in combination with plastic strain energy density is put forward as the criterion for judging dynamic instability of single-layer latticed shells, from which the dynamic critical load value can be derived. Then, nonlinear buckling analysis by the arc-length method combined with Newton-Raphson method is done to the damaged structure due to earthquake, from which the static critical load value can be derived. Results show that the reduction to the structural static stable ability will be obvious after considering damage accumulation effect for single-layer latticed shells, which can be a reference for the structural seismic design, performance assessment, and engineering repair or reinforcement after earthquake.%为了研究地震损伤对单层网壳结构静力稳定性能的影响,基于考虑材料损伤累积效应的本构模型,对一K8型单层球面网壳结构,首先利用动态增量( incremental dynamic analysis,IDA)方法对单层网壳结构进行动力稳定分析,提出将B-R准则与塑性应变能曲线相结合作为结构动力失稳破坏的判断准则,得到结构动力失稳临界值；然后采用弧长法和Newton-Raphson法相结合的增量迭代法对损伤后的结构进行非线性屈曲分析,得到震后结构的静力稳定临界荷载。结果表明：考虑地震损伤累积效应的结构静力稳定性能显著降低,为该类结构抗震设计、性能评估和震后修复、加固提供参考。
Load and speed effects on the cervical flexion relaxation phenomenon
Descarreaux Martin
2010-03-01
Full Text Available Abstract Background The flexion relaxation phenomenon (FRP represents a well-studied neuromuscular response that occurs in the lumbar and cervical spine. However, the cervical spine FRP has not been investigated extensively, and the speed of movement and loading effects remains to be characterized. The objectives of the present study were to evaluate the influence of load and speed on cervical FRP electromyographic (EMG and kinematic parameters and to assess the measurement of cervical FRP kinematic and EMG parameter repeatability. Methods Eighteen healthy adults (6 women and 12 men, aged 20 to 39 years, participated in this study. They undertook 2 sessions in which they had to perform a standardized cervical flexion/extension movement in 3 phases: complete cervical flexion; the static period in complete cervical flexion; and extension with return to the initial position. Two different rhythm conditions and 3 different loading conditions were applied to assess load and speed effects. Kinematic and EMG data were collected, and dependent variables included angles corresponding to the onset and cessation of myoelectric silence as well as the root mean square (RMS values of EMG signals. Repeatability was examined in the first session and between the 2 sessions. Results Statistical analyses revealed a significant load effect (P Conclusions The load increase evoked augmented FRP onset and cessation angles as well as heightened muscle activation. Such increments may reflect the need to enhance spinal stability under loading conditions. The kinematic and EMG parameters showed promising repeatability. Further studies are needed to assess kinematic and EMG differences between healthy subjects and patients with neck pain.
Speight, J. M.
1997-03-01
A point particle approximation to the classical dynamics of well-separated vortices of the Abelian Higgs model is developed. A static vortex is asymptotically identical to a solution of the linearized field theory (a Klein-Gordon-Proca theory) in the presence of a singular point source at the vortex center. It is shown that this source is a composite scalar monopole and magnetic dipole, and the respective charges are determined numerically for various values of the coupling constant. The interaction potential of two well-separated vortices is computed by calculating the interaction Lagrangian of two such point sources in the linear theory. The potential is used to model type II vortex scattering.
Grueneisen relaxation photoacoustic microscopy
Wang, Lidai; Zhang, Chi; Wang, Lihong V.
2014-01-01
The temperature-dependent property of the Grueneisen parameter has been employed in photoacoustic imaging mainly to measure tissue temperature. Here we explore this property using a different approach and develop Grueneisen-relaxation photoacoustic microscopy (GR-PAM), a technique that images non-radiative absorption with confocal optical resolution. GR-PAM sequentially delivers two identical laser pulses with a micro-second-scale time delay. The first laser pulse generates a photoacoustic signal and thermally tags the in-focus absorbers. Owing to the temperature dependence of the Grueneisen parameter, when the second laser pulse excites the tagged absorbers within the thermal relaxation time, a photoacoustic signal stronger than the first one is produced. GR-PAM detects the amplitude difference between the two co-located photoacoustic signals, confocally imaging the non-radiative absorption. We greatly improved axial resolution from 45 µm to 2.3 µm and at the same time slightly improved lateral resolution from 0.63 µm to 0.41 µm. In addition, the optical sectioning capability facilitates the measurement of the absolute absorption coefficient without fluence calibration. PMID:25379919
Elements of magnetohydrodynamic stability theory
Spies, G O
1976-11-01
The nonlinear equations of ideal magnetohydrodynamics are discussed along with the following topics: (1) static equilibrium, (2) strict linear theory, (3) stability of a system with one degree of freedom, (4) spectrum and variational principles in magnetohydrodynamics, (5) elementary proof of the modified energy principle, (6) sufficient stability criteria, (7) local stability, and (8) normal modes. (MOW)
Magnetoviscosity and relaxation in ferrofluids
Felderhof
2000-09-01
The increase in viscosity of a ferrofluid due to an applied magnetic field is discussed on the basis of a phenomenological relaxation equation for the magnetization. The relaxation equation was derived earlier from irreversible thermodynamics, and differs from that postulated by Shliomis. The two relaxation equations lead to a different dependence of viscosity on magnetic field, unless the relaxation rates are related in a specific field-dependent way. Both planar Couette flow and Poiseuille pipe flow in parallel and perpendicular magnetic field are discussed. The entropy production for these situations is calculated and related to the magnetoviscosity.
Rupp, Wolf; Simon, Karl-Heinz; Bohnert, Michael
2009-01-01
Complete relaxation can be achieved by floating in a darkened, sound-proof relaxation tank filled with salinated water kept at body temperature. Under these conditions, meditation exercises up to self-hypnosis may lead to deep relaxation with physical and mental revitalization. A user manipulated his tank, presumably to completely cut off all optical and acoustic stimuli and accidentally also covered the ventilation hole. The man was found dead in his relaxation tank. The findings suggested lack of oxygen as the cause of death.
Relaxing Behavioural Inheritance
Nuno Amálio
2013-05-01
Full Text Available Object-oriented (OO inheritance allows the definition of families of classes in a hierarchical way. In behavioural inheritance, a strong version, it should be possible to substitute an object of a subclass for an object of its superclass without any observable effect on the system. Behavioural inheritance is related to formal refinement, but, as observed in the literature, the refinement constraints are too restrictive, ruling out many useful OO subclassings. This paper studies behavioural inheritance in the context of ZOO, an object-oriented style for Z. To overcome refinement's restrictions, this paper proposes relaxations to the behavioural inheritance refinement rules. The work is presented for Z, but the results are applicable to any OO language that supports design-by-contract.
Zhang Xingyi; Zhou Jun; Zhou Youhe [Key Laboratory of Mechanics on Western Disaster and Environment, Ministry of Education (China); Liang Xinwen [Department of Finance, School of Economics of Sichuan University, Sichuan University, Chengdu, Sichuan 610064 (China)
2009-02-15
We present an experimental study of the relaxation of vertical and horizontal force components in an unsymmetrical high-temperature superconducting levitation system, with different initial cooling processes, after fixing the levitated body statically in a given position. It was found that the values of the relaxation measurements of the levitation force and lateral force remained constant or increased with time after vertical and horizontal traverses. The phenomenon has been theoretically described based on the Bean model and the thermally activated flux creep theory. The criterion developed in the present work is considered to be suitable for providing qualitative predictions of the relaxation properties in the levitation force and lateral force.
Zhang, Xing-Yi; Zhou, Jun; Zhou, You-He; Liang, Xin-Wen
2009-02-01
We present an experimental study of the relaxation of vertical and horizontal force components in an unsymmetrical high-temperature superconducting levitation system, with different initial cooling processes, after fixing the levitated body statically in a given position. It was found that the values of the relaxation measurements of the levitation force and lateral force remained constant or increased with time after vertical and horizontal traverses. The phenomenon has been theoretically described based on the Bean model and the thermally activated flux creep theory. The criterion developed in the present work is considered to be suitable for providing qualitative predictions of the relaxation properties in the levitation force and lateral force.
Statics and Mechanics of Structures
Krenk, Steen; Høgsberg, Jan Becker
The statics and mechanics of structures form a core aspect of civil engineering. This book provides an introduction to the subject, starting from classic hand-calculation types of analysis and gradually advancing to a systematic form suitable for computer implementation. It starts with statically...
Static analysis of an office desk construction
Milan Novotný
2011-01-01
Full Text Available The objective of the paper is a static analysis of a desk construction and the determination of its probable mechanical behaviour using Finite Element Method. The construction was modelled and numerically analysed in Autocad Inventor 2011 and the stability of the entire desk was calculated with the size and placement of the loading force based on the standards and cited literature. Possible locations and directions of the deformation were analysed and a solution for its prevention was proposed and the stability of the desk as well as the extreme position of the stand were calculated. The verification of the obtained results in an accredited furniture testing lab is planned using a prototype of the office desk.
Magnetic relaxation in anisotropic magnets
Lindgård, Per-Anker
1971-01-01
The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse or...
Hard sphere colloidal dispersions: Mechanical relaxation pertaining to thermodynamic forces
Mellema, J.; Kruif, de C.G.; Blom, C.; Vrij, A.
1987-01-01
The complex viscosity of sterically stabilized (hard) silica spheres in cyclohexane has been measured between 80 Hz and 170 kHz with torsion pendulums and a nickel tube resonator. The observed relaxation behaviour can be attributed to the interplay of hydrodynamic and thermodynamic forces. The valid
Einstein Static Universe in Exponential $f(T)$ Gravity
Li, Jung-Tsung; Geng, Chao-Qiang
2013-01-01
We analyze the stability of the Einstein static closed and open universe in two types of exponential $f(T)$ gravity theories. We show that the stable solutions exist in these two models. In particular, we find that large regions of parameter space in equation of state $w=p/\\rho$ for the stable universe are allowed in the $f(T)$ theories.
Einstein static universe in exponential f(T) gravity
Li, Jung-Tsung; Lee, Chung-Chi; Geng, Chao-Qiang [National Tsing Hua University, Department of Physics, Hsinchu (China); National Center for Theoretical Sciences, Physics Division, Hsinchu (China)
2013-02-15
We analyze the stability of the Einstein static closed and open universe in two types of exponential f(T) gravity theory. We show that stable solutions exist in these two models. In particular, we find that large regions of parameter space in equation of state w=p/{rho} for the stable universe are allowed in the f(T) theories. (orig.)
A Synthesis Method for Static Anti-Windup Compensators
Solyom, Stefan
2003-01-01
Synthesis of static anti-windup compensators is considered. LMIconditions are established for stability and performance analysis of the closedloop system. The performance criterion describes the servo problem forthe resulting closed-loop piecewise linear system. The synthesisof the anti-windup compensators will be given by some bilinear matrix inequalities.
Size-dependent MR relaxivities of magnetic nanoparticles
Joos, Alexander; Löwa, Norbert; Wiekhorst, Frank; Gleich, Bernhard; Haase, Axel
2017-04-01
Magnetic nanoparticles (MNPs) can be used as carriers for magnetic drug targeting and for stem cell tracking by magnetic resonance imaging (MRI). For these applications, it is crucial to quantitatively determine the spatial distribution of the MNP concentration, which can be approached by MRI relaxometry. Theoretical considerations and experiments have shown that R2 relaxation rates are sensitive to the aggregation state of the particles, whereas R2* is independent of aggregation state and therefore suited for MNP quantification if the condition of static dephasing is met. We present a new experimental approach to characterize an MNP system with respect to quantitative MRI based on hydrodynamic fractionation. The first results qualitatively confirm the outer sphere relaxation theory for small MNPs and show that the two commercial MRI contrast agents Resovist® and Endorem® should not be used for quantitative MRI because they do not fulfill the condition for static dephasing. Our approach could facilitate the choice of MNPs for quantitative MRI and help clarifying the relationship between size, magnetism and relaxivity of MNPs in the future.
Interconnection between static regimes in the LJJs described by the double sine-Gordon equation
Atanasova, P. Kh; Zemlyanaya, E. V.; Shukrinov, Yu M.
2012-11-01
The second harmonic contribution to the current-phase relation changes the properties of the static magnetic flux distributions in the long Josephson junction (LJJ) and inspires new homogenious and fluxon static states. We study stability properties and bifurcations of these static regimes within the frame of a model described by the double sine-Gordon equation. The critical curves behavior and the interconnection between different types of magnetic flux distributions are analyzed.
Zero-field slow magnetic relaxation in a uranium(III) complex with a radical ligand.
Coutinho, Joana T; Antunes, Maria A; Pereira, Laura C J; Marçalo, Joaquim; Almeida, Manuel
2014-09-14
[U(Tp(Me2))2(bipy˙)], a uranium(III) complex with a radical bipyridine ligand which has magnetic properties with contributions from both the ligand and the metal, presents slow relaxation of the magnetisation at low temperatures, already under zero static magnetic field, and energy barriers slightly above the non-radical analogues.
Static Validation of XSL Transformations
Møller, Anders; Olesen, Mads Østerby; Schwartzbach, Michael Ignatieff
2007-01-01
no static guarantees that, under the assumption that the input is valid relative to the input schema, the output of the transformation is valid relative to the output schema. We present a validation technique for XSLT based on the XML graph formalism introduced in the static analysis of JWIG Web services...... and XACT XML transformations. Being able to provide static guarantees, we can detect a large class of errors in an XSLT stylesheet at the time it is written instead of later when it has been deployed, and thereby provide benefits similar to those of static type checkers for modern programming languages....... Our analysis takes a pragmatic approach that focuses its precision on the essential language features but still handles the entire XSLT language. We evaluate the analysis precision on a range of real stylesheets and demonstrate how it may be useful in practice....
The statics of cervical traction.
Pio, A; Rendina, M; Benazzo, F; Castelli, C; Paparella, F
1994-08-01
The statics of a sliding body was used to study the distribution of forces during the application of cervical traction in supine patients. This theoretical analysis was completed using a dynamometer to determine the static friction between bed surface and patient head. Therefore, we measured the head weight in 12 inpatients and the minimum force that causes impending motion of the head on the bed surface. The static friction coefficient was calculated from the ratio of the two quantities. The forces acting on the cervical spine were determined by inserting the former data into a specifically designed algorithm that forecasted a progressively increasing traction angle. The coefficient of static friction was 0.62, whereas the maximum available force acting on the cervical spine was obtained with a 35 degrees traction inclination. In contrast, the forces dissipated by the plane progressively decreased with larger angles.
Statics of Historic Masonry Constructions
Como, Mario
2013-01-01
Masonry constructions are the great majority of the buildings in Europe’s historic centres and the most important monuments in its architectural heritage. Given the age of much of these constructions, the demand for safety assessments and restoration projects is pressing and constant. This book aims to help fill this demand presenting a comprehensive new statics of masonry constructions. The book, result of thirty years of research and professional experience, gives the fundamentals of statics of the masonry solid, then applied to the study of statics of arches, piers and vaults. Further, combining engineering and architecture and through an interdisciplinary approach, the book investigates the statical behaviour of many historic monuments, as the Pantheon, the Colosseum, the domes of S. Maria del Fiore in Florence and of St. Peter in Rome, the Tower of Pisa, the Gothic Cathedrals and the Masonry Buildings under seismic actions.
Can Black Hole Relax Unitarily?
Solodukhin, S. N.
2005-03-01
We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.
Can Black Hole Relax Unitarily?
Solodukhin, Sergey N.
2004-01-01
We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the...
Can Black Hole Relax Unitarily?
Solodukhin, S N
2004-01-01
We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.
Static and Dynamic Traversable Wormholes
Adamiak, Jaroslaw P.
2008-09-01
The aim of this work is to discuss the effects found in static and dynamic wormholes that occur as a solution of Einstein equations in general relativity. The ground is prepared by presentation of faster than light effects, then the focus is narrowed to Morris-Thorne framework for a static spherically symmetric wormhole. Two types of dynamic worm-holes, evolving and rotating, are considered.
Static Decoupling in fault detection
Niemann, Hans Henrik
1998-01-01
An algebraic approach is given for a design of a static residual weighting factor in connection with fault detection. A complete parameterization is given of the weighting factor which will minimize a given performance index......An algebraic approach is given for a design of a static residual weighting factor in connection with fault detection. A complete parameterization is given of the weighting factor which will minimize a given performance index...
Loss of the Statical Stabity of Electrical Machine Rotor Under Influence of Stator Magnetic Field
Shekyan H.G.
2007-06-01
Full Text Available It is assumed, that magnetic forces, acting on to the rotor by the stator field, are varied proportional with displacements. The criteria of rotor statical stability, depending on rigid characteristics and boundary conditions are obtained.
Field theory of bicritical and tetracritical points. I. Statics.
Folk, R; Holovatch, Yu; Moser, G
2008-10-01
We calculate the static critical behavior of systems of O(n_||)(plus sign in circle)O(n_perpendicular) symmetry by the renormalization group method within the minimal subtraction scheme in two-loop order. Summation methods lead to fixed points describing multicritical behavior. Their stability border lines in the space of the order parameter components n_|| and n_perpendicular and spatial dimension d are calculated. The essential features obtained already in two-loop order for the interesting case of an antiferromagnet in a magnetic field ( n_|| =1, n_perpendicular =2 ) are the stability of the biconical fixed point and the neighborhood of the stability border lines to the other fixed points, leading to very small transient exponents. We are also able to calculate the flow of static couplings, which allows us to consider the attraction region. Depending on the nonuniversal background parameters, the existence of different multicritical behavior (bicritical or tetracritical) is possible, including a triple point.
Meena .V
2016-10-01
Full Text Available Background: Osteoarthritis (OA is a degenerative joint disease and one of the major public health problem that causesfunctional impairment and reduced quality of life. To compare the effectiveness of PNF Hold relax stretching versus Static stretching on pain and flexibility of hamstring following moist heat in individuals with knee osteoarthritis. Hamstring tightness is the major problem in knee osteoarthritis individuals. Therefore the need of study is comparing the effectiveness of PNF Hold relax stretching versus static stretching on pain and flexibility of hamstrings following moist heat in knee osteoarthritis participants. Determining the effects of PNF Hold relax stretching versus Static stretching along with moist heat on pain and hamstring flexibility by VAS and Active knee extension range of motion in knee osteoarthritis individuals. Methods: 30 subjects with symptoms of knee osteoarthritis were randomly distributed into 2 groups 15 in each group. PNF Hold relax stretching along with moist heat is compared to Static stretching along with moist heat. Pain was measured by Visual Analogue Scale (VAS and hamstring flexibility by Active knee Extension Range of Motion (AKEROM by universal goniometer. Measurements are taken pre and post intervention. Results: The results indicated PNF Hold relax stretching along with moist heat showed a statistically significant improvement in pain (p<0.05 and improvement in hamstring flexibility (p<0.05 when compared to Static stretching along with moist heat. Conclusion: Subjects with PNF Hold relax stretching along with moist heat showed significant improvement in pain reduction and improving hamstring flexibility than Static stretching along with moist heat.
严宏志; 何攀; 刘明
2009-01-01
To deal with the vibration and crawling of casting machine,motion and dynamics models of the chain belt system about a casting machine were established by commercial software ADAMS.It Was discussed that dynamic characteristics effects the chain belt system stability under different"chain belt-guide"dynamic friction difference and different load conditions.And combined with field test of the chain belt vibration,the generation condition of the chain belt vibration and crawling was explored.It would provide a basis for the control of casting machine vibration and crawling.%针对铸型机的振动与爬行问题,基于ADAMS建立铸型机链带系统的运动与动力学模型,分析不同"链带-导轨"动摩擦与静摩擦差、不同载荷条件下的动态特性对链带系统稳定性的影响.结合对铸型机链带振动的现场测试,探讨铸型机链带振动和爬行产生的条件,为铸型机振动和爬行的控制提供依据.
Immersed Boundary-Lattice Boltzmann Method Using Two Relaxation Times
Kosuke Hayashi
2012-06-01
Full Text Available An immersed boundary-lattice Boltzmann method (IB-LBM using a two-relaxation time model (TRT is proposed. The collision operator in the lattice Boltzmann equation is modeled using two relaxation times. One of them is used to set the fluid viscosity and the other is for numerical stability and accuracy. A direct-forcing method is utilized for treatment of immersed boundary. A multi-direct forcing method is also implemented to precisely satisfy the boundary conditions at the immersed boundary. Circular Couette flows between a stationary cylinder and a rotating cylinder are simulated for validation of the proposed method. The method is also validated through simulations of circular and spherical falling particles. Effects of the functional forms of the direct-forcing term and the smoothed-delta function, which interpolates the fluid velocity to the immersed boundary and distributes the forcing term to fixed Eulerian grid points, are also examined. As a result, the following conclusions are obtained: (1 the proposed method does not cause non-physical velocity distribution in circular Couette flows even at high relaxation times, whereas the single-relaxation time (SRT model causes a large non-physical velocity distortion at a high relaxation time, (2 the multi-direct forcing reduces the errors in the velocity profile of a circular Couette flow at a high relaxation time, (3 the two-point delta function is better than the four-point delta function at low relaxation times, but worse at high relaxation times, (4 the functional form of the direct-forcing term does not affect predictions, and (5 circular and spherical particles falling in liquids are well predicted by using the proposed method both for two-dimensional and three-dimensional cases.
Nonlinear relaxation field in charged systems under high electric fields
Morawetz, K
2000-07-01
The influence of an external electric field on the current in charged systems is investigated. The results from the classical hierarchy of density matrices are compared with the results from the quantum kinetic theory. The kinetic theory yields a systematic treatment of the nonlinear current beyond linear response. To this end the dynamically screened and field-dependent Lenard-Balescu equation is integrated analytically and the nonlinear relaxation field is calculated. The classical linear response result known as Debye - On-Sager relaxation effect is only obtained if asymmetric screening is assumed. Considering the kinetic equation of one specie the other species have to be screened dynamically while the screening with the same specie itself has to be performed statically. Different other approximations are discussed and compared. (author)
Local spin relaxation within the random Heisenberg chain.
Herbrych, J; Kokalj, J; Prelovšek, P
2013-10-04
Finite-temperature local dynamical spin correlations S(nn)(ω) are studied numerically within the random spin-1/2 antiferromagnetic Heisenberg chain. The aim is to explain measured NMR spin-lattice relaxation times in BaCu(2)(Si(0.5)Ge(0.5))(2)O(7), which is the realization of a random spin chain. In agreement with experiments we find that the distribution of relaxation times within the model shows a very large span similar to the stretched-exponential form. The distribution is strongly reduced with increasing T, but stays finite also in the high-T limit. Anomalous dynamical correlations can be associated with the random singlet concept but not directly with static quantities. Our results also reveal the crucial role of the spin anisotropy (interaction), since the behavior is in contrast with the ones for the XX model, where we do not find any significant T dependence of the distribution.
Fast relaxation transients in a kicked damped oscillator
Urquizu, Merce [Laboratori d' Estudis Geofisics ' Eduard Fontsere' , IEC, Barcelona (Spain); Correig, Antoni M. [Departament d' Astronomical i Meteorologia, Laboratori d' Estudis Geofisics Eduard Fontsere, UB Marti Franques 1, E-08028 Barcelona (Spain) and Laboratori d' Estudis Geofisics ' Eduard Fontsere' , IEC, Barcelona (Spain)]. E-mail: ton.correig@am.ub.es
2007-08-15
Although nonlinear relaxation transients are very common in nature, very few studies are devoted to its characterization, mainly due to its short time duration. In this paper, we present a study about the nature of relaxation transients in a kicked damped oscillator, in which transients are generated in terms of continuous fast changes in the parameters of the system. We have found that transient dynamics can be described, rather than in terms of bifurcation dynamics, in terms of instantaneous stretching factors, which are related to the stability of fixed points of the corresponding stroboscopic maps.
An application-semantics-based relaxed transaction model for internetware
HUANG Tao; DING Xiaoning; WEI Jun
2006-01-01
An internetware application is composed by existing individual services, while transaction processing is a key mechanism to make the composition reliable. The existing research of transactional composite service (TCS) depends on the analysis to composition structure and exception handling mechanism in order to guarantee the relaxed atomicity.However, this approach cannot handle some application-specific requirements and causes lots of unnecessary failure recoveries or even aborts. In this paper, we propose a relaxed transaction model, including system mode, relaxed atomicity criterion, static checking algorithm and dynamic enforcement algorithm. Users are able to define different relaxed atomicity constraint for different TCS according to application-specific requirements, including acceptable configurations and the preference order. The checking algorithm determines whether the constraint can be guaranteed to be satisfied. The enforcement algorithm monitors the execution and performs transaction management work according to the constraint. Compared to the existing work, our approach can handle complex application requirements, avoid unnecessary failure recoveries and perform the transaction management work automatically.
An Exact Relaxation of Clustering
Mørup, Morten; Hansen, Lars Kai
2009-01-01
of clustering problems such as the K-means objective and pairwise clustering as well as graph partition problems, e.g., for community detection in complex networks. In particular we show that a relaxation to the simplex can be given for which the extreme solutions are stable hard assignment solutions and vice......Continuous relaxation of hard assignment clustering problems can lead to better solutions than greedy iterative refinement algorithms. However, the validity of existing relaxations is contingent on problem specific fuzzy parameters that quantify the level of similarity between the original...... versa. Based on the new relaxation we derive the SR-clustering algorithm that has the same complexity as traditional greedy iterative refinement algorithms but leading to significantly better partitions of the data. A Matlab implementation of the SR-clustering algorithm is available for download....
The relaxation & stress reduction workbook
Davis, Martha; Eshelman, Elizabeth Robbins; McKay, Matthew
2008-01-01
"The Relaxation & Stress Reduction Workbook broke new ground when it was first published in 1980, detailing easy, step-by-step techniques for calming the body and mind in an increasingly overstimulated world...
Relaxation Dynamics in Heme Proteins.
Scholl, Reinhard Wilhelm
A protein molecule possesses many conformational substates that are likely arranged in a hierarchy consisting of a number of tiers. A hierarchical organization of conformational substates is expected to give rise to a multitude of nonequilibrium relaxation phenomena. If the temperature is lowered, transitions between substates of higher tiers are frozen out, and relaxation processes characteristic of lower tiers will dominate the observational time scale. This thesis addresses the following questions: (i) What is the energy landscape of a protein? How does the landscape depend on the environment such as pH and viscosity, and how can it be connected to specific structural parts? (ii) What relaxation phenomena can be observed in a protein? Which are protein specific, and which occur in other proteins? How does the environment influence relaxations? (iii) What functional form best describes relaxation functions? (iv) Can we connect the motions to specific structural parts of the protein molecule, and are these motions important for the function of the protein?. To this purpose, relaxation processes after a pressure change are studied in carbonmonoxy (CO) heme proteins (myoglobin-CO, substrate-bound and substrate-free cytochrome P450cam-CO, chloroperoxidase-CO, horseradish peroxidase -CO) between 150 K and 250 K using FTIR spectroscopy to monitor the CO bound to the heme iron. Two types of p -relaxation experiments are performed: p-release (200 to ~eq40 MPa) and p-jump (~eq40 to 200 MPa) experiments. Most of the relaxations fall into one of three groups and are characterized by (i) nonexponential time dependence and non-Arrhenius temperature dependence (FIM1( nu), FIM1(Gamma)); (ii) exponential time dependence and non-Arrhenius temperature dependence (FIM0(A_{i}to A_{j})); exponential time dependence and Arrhenius temperature dependence (FIMX( nu)). The influence of pH is studied in myoglobin-CO and shown to have a strong influence on the substate population of the
Negative magnetic relaxation in superconductors
Krasnoperov E.P.
2013-01-01
Full Text Available It was observed that the trapped magnetic moment of HTS tablets or annuli increases in time (negative relaxation if they are not completely magnetized by a pulsed magnetic field. It is shown, in the framework of the Bean critical-state model, that the radial temperature gradient appearing in tablets or annuli during a pulsed field magnetization can explain the negative magnetic relaxation in the superconductor.
High-codimensional static bifurcations of strongly nonlinear oscillator
Zhang Qi-Chang; Wang Wei; Liu Fu-Hao
2008-01-01
The static bifurcation of the parametrically excited strongly nonlinear oscillator is studied.We consider the averaged equations of a system subject to Duffing-van der Pol and quintic strong nonlinearity by introducing the undetermined fundamental frequency into the computation in the complex normal form.To discuss the static bifurcation,the bifurcation problem is described as a 3-codimensional unfolding with Z2 symmetry on the basis of singularity theory.The transition set and bifurcation diagrams for the singularity are presented,while the stability of the zero solution is studied by using the eigenvalues in various parameter regions.
Spin Relaxation in Kondo Lattice Systems with Anisotropic Kondo Interaction
Belov, S. I.; Kutuzov, A. S.
2016-12-01
We study the influence of the Kondo effect on the spin relaxation in systems with anisotropic Kondo interaction at temperatures both high and low as compared with the static magnetic field. In the absence of the Kondo effect, the electron spin resonance linewidth is not narrowed in the whole temperature range due to the high anisotropy of the Kondo interaction. The Kondo effect leads to the universal energy scale, which regulates the temperature and magnetic field dependence of different kinetic coefficients and results in a mutual cancelation of their singular parts in a collective spin mode.
Krylov-subspace acceleration of time periodic waveform relaxation
Lumsdaine, A. [Univ. of Notre Dame, IN (United States)
1994-12-31
In this paper the author uses Krylov-subspace techniques to accelerate the convergence of waveform relaxation applied to solving systems of first order time periodic ordinary differential equations. He considers the problem in the frequency domain and presents frequency dependent waveform GMRES (FDWGMRES), a member of a new class of frequency dependent Krylov-subspace techniques. FDWGMRES exhibits many desirable properties, including finite termination independent of the number of timesteps and, for certain problems, a convergence rate which is bounded from above by the convergence rate of GMRES applied to the static matrix problem corresponding to the linear time-invariant ODE.
Structural relaxation in dense liquids composed of anisotropic particles.
Shen, Tianqi; Schreck, Carl; Chakraborty, Bulbul; Freed, Denise E; O'Hern, Corey S
2012-10-01
We perform extensive molecular dynamics simulations of dense liquids composed of bidisperse dimer- and ellipse-shaped particles in two dimensions that interact via purely repulsive contact forces. We measure the structural relaxation times obtained from the long-time α decay of the self part of the intermediate scattering function for the translational and rotational degrees of freedom (DOF) as a function of packing fraction φ, temperature T, and aspect ratio α. We are able to collapse the packing-fraction and temperature-dependent structural relaxation times for disks, and dimers and ellipses over a wide range of α, onto a universal scaling function F(±)(|φ-φ(0)|,T,α), which is similar to that employed in previous studies of dense liquids composed of purely repulsive spherical particles in three dimensions. F(±) for both the translational and rotational DOF are characterized by the α-dependent scaling exponents μ and δ and packing fraction φ(0)(α) that signals the crossover in the scaling form F(±) from hard-particle dynamics to super-Arrhenius behavior for each aspect ratio. We find that the fragility of structural relaxation at φ(0), m(φ(0)), decreases monotonically with increasing aspect ratio for both ellipses and dimers. For α>α(p), where α(p) is the location of the peak in the packing fraction φ(J) at jamming onset, the rotational DOF are strongly coupled to the translational DOF, and the dynamic scaling exponents and φ(0) are similar for the rotational and translational DOF. For 1composed of dimer- and ellipse-shaped particles are qualitatively the same, despite the fact that zero-temperature static packings of dimers are isostatic, while static packings of ellipses are hypostatic. Thus, zero-temperature contact counting arguments do not apply to structural relaxation of dense liquids of anisotropic particles near the glass transition.
Static-static-light-light tetraquarks in lattice QCD
Wagner, Marc
2011-01-01
I report on a lattice computation of the energy of a system of two light quarks and two static antiquarks as a function of the separation of the static antiquarks. In terms of hadrons such a system corresponds to a pair of B mesons and its energy to the hadronic potential. I present selected results for different isospin, spin and parity combinations of the individual B mesons mainly focusing on those channels relevant to determine, whether two B mesons may form a bound tetraquark state.
Static Filtered Sky Color Constancy
Ali Alkhalifah
2016-05-01
Full Text Available In Computer Vision, the sky color is used for lighting correction, image color enhancement, horizon alignment, image indexing, and outdoor image classification and in many other applications. In this article, for robust color based sky segmentation and detection, usage of lighting correction for sky color detection is investigated. As such, the impact of color constancy on sky color detection algorithms is evaluated and investigated. The color correction (constancy algorithms used includes Gray-Edge (GE, Gray-World (GW, Max-RGB (MRGB and Shades-of-Gray (SG. The algorithms GE, GW, MRGB, and SG, are tested on the static filtered sky modeling. The static filter is developed in the LAB color space. This evaluation and analysis is essential for detection scenarios, especially, color based object detection in outdoor scenes. From the results, it is concluded that the color constancy before sky color detection using LAB static filters has the potential of improving sky color detection performance. However, the application of the color constancy can impart adverse effects on the detection results. For images, the color constancy algorithms depict a compact and stable representative of the sky chroma loci, however, the sky color locus might have a shifting and deviation in a particular color representation. Since the sky static filters are using the static chromatic values, different results can be obtained by applying color constancy algorithms on various datasets.
刘昇; 徐政; 华文; 黄弘扬
2014-01-01
Solving loadability limit quickly is the basic requirement of online assessment for power systems voltage stability. This paper proposed a SIPSS-Lasso-BP network aiming to offline fitting and online forecasting the loadability limit. The network consisted of the similarity index of power system state (SIPSS) based screening method, the least absolute shrinkage and select operator (Lasso) algorithm and the back propagation (BP) neural network. The SIPSS based screening method screened the training samples according to their loadability limits and similarity indexes of power system state. The Lasso algorithm selected the principal system state variables which were most explanatory to the loadability limit via the modified regression analysis of the training samples. The BP network was used to offline fit and online forecast the loadability limit of the system through the cut training samples. The test results on the New England 39-bus system and a practical example show that the SIPSS-Lasso-BP network can significantly improve the efficiency of offline training the BP network and guarantee the forecasting accuracy.%快速求解系统负荷能力极限是在线评估电力系统电压稳定性的基本要求。提出一种用于离线拟合并在线预测负荷能力极限的 SIPSS-Lasso-BP 网络。该网络由基于电网状态相似度指标(similarity index of power system state，SIPSS)的样本筛选方法、最小绝对值收缩选择(least absolute shrinkage and select operator，Lasso)方法和BP(back propagation)神经网络共同组成。基于SIPSS的样本筛选方法以样本负荷能力极限值和电网状态相似度量化指标为依据，对训练样本进行筛选。Lasso 方法对训练样本进行回归分析，确定各状态量中对负荷能力极限最具有解释性的系统状态量。BP神经网络通过精简后的训练样本来离线拟合负荷能力极限并用于在线预测。通过新英格兰39节点算例和某省实际算例
Statics of historic masonry constructions
Como, Mario
2017-01-01
Masonry constructions are the great majority of the buildings in Europe’s historic centres and the most important monuments of its architectural heritage. Given the age of these constructions, the demand for safety assessments and restoration projects is pressing and constant; still within the broad studies in the subject it is not yet recognised, in particular within the seismic area, a unitary approach to deal with Masonry structures. This successful book contributes to clarify the issues with a rigorous approach offering a comprehensive new Statics of Masonry Constructions. This third edition has been driven by some recent developments of the research in the field, and it gives the fundamentals of Statics with an original and rigorous mathematical formulation, further in-depth inquired in this new version. With many refinements and improvements, the book investigates the static behaviour of many historic monuments, such as the Gothic Cathedrals, the Mycenaean Tholoi, the Pantheon, the Colosseum, the dome...
Static Correctness of Hierarchical Procedures
Schwartzbach, Michael Ignatieff
1990-01-01
A system of hierarchical, fully recursive types in a truly imperative language allows program fragments written for small types to be reused for all larger types. To exploit this property to enable type-safe hierarchical procedures, it is necessary to impose a static requirement on procedure calls....... We introduce an example language and prove the existence of a sound requirement which preserves static correctness while allowing hierarchical procedures. This requirement is further shown to be optimal, in the sense that it imposes as few restrictions as possible. This establishes the theoretical...... basis for a general type hierarchy with static type checking, which enables first-order polymorphism combined with multiple inheritance and specialization in a language with assignments. We extend the results to include opaque types. An opaque version of a type is different from the original but has...
Static dipole polarizabilities of Scn (n≤15) clusters
Li Xi-Bo; Wang Hong-Yan; Luo Jiang-Shan; Guo Yun-Dong; Wu Wei-Dong; Tang Yong-Jian
2009-01-01
The static dipole polarizabilities of scandium clusters with up to 15 atoms are determined by using the numerically finite field method in the framework of density functional theory. The electronic effects on the polarizabilities are investigated for the scandium clusters.We examine a large highest occupied molecular orbital-the lowest occupied molecular orbital (HOMO-LUMO) gap of a scandium cluster usually corresponds to a large dipole moment.The static polarizability per atom decreases slowly and exhibits local minimum with increasing cluster size.The polarizability anisotropy and the ratio of mean static polarizability to the HOMO-LUMO gap can also reflect the cluster stability.The polarizability of the scandium cluster is partially related to the HOMO-LUMO gap and is also dependent on geometrical characteristics.A strong correlation between the polarizability and ionization energy is observed.
Static and dynamic buckling of thin-walled plate structures
Kubiak, Tomasz
2013-01-01
This monograph deals with buckling and postbuckling behavior of thin plates and thin-walled structures with flat wall subjected to static and dynamic load. The investigations are carried out in elastic range. The basic assumption here is the thin plate theory. This method is used to determination the buckling load and postbuckling analysis of thin-walled structures subjected to static and dynamic load. The book introduces two methods for static and dynamic buckling investigation which allow for a wider understanding of the phenomenon. Two different methods also can allow uncoupling of the phenomena occurring at the same time and attempt to estimate their impact on the final result. A general mathematical model, adopted in proposed analytical-numerical method, enables the consideration of all types of stability loss i.e.local, global and interactive forms of buckling. The applied numerical-numerical method includes adjacent of walls, shear-lag phenomenon and a deplanation of cross-sections.
Static impedance behavior of programmable metallization cells
Rajabi, S.; Saremi, M.; Barnaby, H. J.; Edwards, A.; Kozicki, M. N.; Mitkova, M.; Mahalanabis, D.; Gonzalez-Velo, Y.; Mahmud, A.
2015-04-01
Programmable metallization cell (PMC) devices work by growing and dissolving a conducting metallic bridge across a chalcogenide glass (ChG) solid electrolyte, which changes the resistance of the cell. PMC operation relies on the incorporation of metal ions in the ChG films via photo-doping to lower the off-state resistance and stabilize resistive switching, and subsequent transport of these ions by electric fields induced from an externally applied bias. In this paper, the static on- and off-state resistance of a PMC device composed of a layered (Ag-rich/Ag-poor) Ge30Se70 ChG film with active Ag and inert Ni electrodes is characterized and modeled using three dimensional simulation code. Calibrating the model to experimental data enables the extraction of device parameters such as material bandgaps, workfunctions, density of states, carrier mobilities, dielectric constants, and affinities.
Cho, Inyong
2016-01-01
We investigate black holes formed by static perfect fluid with $p=-\\rho/3$. These represent the black holes in $S_3$ and $H_3$ spatial geometries. There are three classes of black-hole solutions, two $S_3$ types and one $H_3$ type. The interesting solution is the one of $S_3$ type which possesses two singularities. The one is at the north pole behind the horizon, and the other is naked at the south pole. The observers, however, are free from falling to the naked singularity. There are also nonstatic cosmological solutions in $S_3$ and $H_3$, and a singular static solution in $H_3$.
Static Fourier transform infrared spectrometer.
Schardt, Michael; Murr, Patrik J; Rauscher, Markus S; Tremmel, Anton J; Wiesent, Benjamin R; Koch, Alexander W
2016-04-01
Fourier transform spectroscopy has established itself as the standard method for spectral analysis of infrared light. Here we present a robust and compact novel static Fourier transform spectrometer design without any moving parts. The design is well suited for measurements in the infrared as it works with extended light sources independent of their size. The design is experimentally evaluated in the mid-infrared wavelength region between 7.2 μm and 16 μm. Due to its large etendue, its low internal light loss, and its static design it enables high speed spectral analysis in the mid-infrared.
Voltage Sensors Monitor Harmful Static
2009-01-01
A tiny sensor, small enough to be worn on clothing, now monitors voltage changes near sensitive instruments after being created to alert Agency workers to dangerous static buildup near fuel operations and avionics. San Diego s Quasar Federal Systems received a Small Business Innovation Research (SBIR) contract from Kennedy Space Center to develop its remote voltage sensor (RVS), a dime-sized electrometer designed to measure triboelectric changes in the environment. One of the unique qualities of the RVS is that it can detect static at greater distances than previous devices, measuring voltage changes from a few centimeters to a few meters away, due to its much-improved sensitivity.
Vrancea slab earthquakes triggered by static stress transfer
A. Ganas
2010-12-01
Full Text Available The purpose of this paper is to study the interaction of the Vrancea seismic activity (Romania in space as result of Coulomb, static stress transfer during M=7+ events. In this area, three large events occurred in 1977, 1986 and 1990 at mid-lower, lithospheric depths and with similar focal mechanisms. Assuming elastic rheology for the deforming rocks it is suggested that frictional sliding on pre-existing fault produced the 1986 M=7.1 event (depth 131 km, that was possibly triggered by the 1977 M=7.4 event (depth 94 km. We calculated a static stress transfer of 0.52–0.78 bar to the hypocentre of the 1986 event. On the contrary, the occurrence of the 1990 event is uncertain: it is located inside the relaxed (shadow zone of the combined 1977 and 1986 static stress field considering an azimuth for maximum compression of N307° E. It follows that, the 1990 earthquake most likely represents an unbroken patch (asperity of the 1977 rupture plane that failed due to loading. However, if a different compression azimuth is assumed (N323° E then the 1990 event was also possibly triggered by static stress transfer of the 1977 and 1986 events (combined. Our modeling is a first-order approximation of the kind of earthquake interaction we might expect at intermediate lithospheric depths (80–90 to 130–140 km. It is also suggested that static stress transfer may explain the clustering of Vrancea earthquakes in space by the rupturing of two (possibly three NW-dipping major zones of weakness (faults which accommodate the extension (vertical elongation of the slab.
Dynamical theory of spin relaxation
Field, Timothy R.; Bain, Alex D.
2013-02-01
The dynamics of a spin system is usually calculated using the density matrix. However, the usual formulation in terms of the density matrix predicts that the signal will decay to zero, and does not address the issue of individual spin dynamics. Using stochastic calculus, we develop a dynamical theory of spin relaxation, the origins of which lie in the component spin fluctuations. This entails consideration of random pure states for individual protons, and how these pure states are correctly combined when the density matrix is formulated. Both the lattice and the spins are treated quantum mechanically. Such treatment incorporates both the processes of spin-spin and (finite temperature) spin-lattice relaxation. Our results reveal the intimate connections between spin noise and conventional spin relaxation.
2016-01-01
Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829
Static Analysis for Systems Biology
Nielson, Flemming; Nielson, Hanne Riis; Rosa, D. Schuch da
2004-01-01
This paper shows how static analysis techniques can help understanding biological systems. Based on a simple example we illustrate the outcome of performing three different analyses extracting information of increasing precision. We conclude by reporting on the potential impact and exploitation o...... of these techniques in systems biology....
A systematic review on dynamic versus static distal tibiofibular fixation.
Inge, S Y; Pull Ter Gunne, A F; Aarts, C A M; Bemelman, M
2016-12-01
In the last couple of years dynamic fixation for syndesmosis injuries, using a suture-button technique, raised more interest due to its advantages over the static fixation. In the current systematic review suture-button fixation is compared to the traditionally applied static fixation in unstable ankle fractures accompanied with distal tibiofibular syndesmosis injury, including the functional outcome, post-operative complications, reoperation rate, recurrent diastasis and financial aspects. A computerized literature search using PubMed/MEDLINE and EMBASE was conducted in search of suitable articles between January 2006 and February 2016. A total of 4 suture-button studies, 5 suture-button vs. static fixation studies and 1 study discussing the financial aspects were identified. The AOFAS of 104 patients treated with the suture-button device was 91.08 points with an average study-follow up of 24.85 months. The AOFAS of 106 patients treated with a static fixation device was 87.95 with an average follow-up of 24.78 months. Removal of the suture-button device was reported in 10.5% of 229 patients and removal of the screws in 38.5%. Dynamic fixation demonstrated to be a viable alternative to the static fixation device, with lower reoperation rates and less complications. They can accurately stabilize the ruptured syndesmosis without device breakage or loss of reduction. 1A economic/decision. Copyright Â© 2016 Elsevier Ltd. All rights reserved.
LAVENDER AROMATERAPHY AS A RELAXANT
IGA Prima Dewi AP
2013-02-01
Full Text Available Aromatherapy is a kind of treatment that used aroma with aromatherapy essential oil. Extraction process from essential oil generally doing in three methods, there are distilling with water (boiled, distilling with water and steam, and distilling with steam. One of the most favorite aroma is lavender. The main content from lavender is linalyl acetate and linalool (C10H18O. Linalool is main active contents in lavender which can use for anti-anxiety (relaxation. Based on some research, the conclusion indicates that essential oil from lavender can give relaxation (carminative, sedative, reduce anxiety level and increasing mood.
Statistical mechanics of violent relaxation
Spergel, David N.; Hernquist, Lars
1992-01-01
We propose a functional that is extremized through violent relaxation. It is based on the Ansatz that the wave-particle scattering during violent dynamical processes can be approximated as a sequence of discrete scattering events that occur near a particle's perigalacticon. This functional has an extremum whose structure closely resembles that of spheroidal stellar systems such as elliptical galaxies. The results described here, therefore, provide a simple framework for understanding the physical nature of violent relaxation and support the view that galaxies are structured in accord with fundamental statistical principles.
Active optomechanics through relaxation oscillations
Princepe, Debora; Frateschi, Newton
2014-01-01
We propose an optomechanical laser based on III-V compounds which exhibits self-pulsation in the presence of a dissipative optomechanical coupling. In such a laser cavity, radiation pressure drives the mechanical degree of freedom and its back-action is caused by the mechanical modulation of the cavity loss rate. Our numerical analysis shows that even in a wideband gain material, such dissipative coupling couples the mechanical oscillation with the laser relaxation oscillations process. Laser self-pulsation is observed for mechanical frequencies below the laser relaxation oscillation frequency under sufficiently high optomechanical coupling factor.
Thermal relaxation and mechanical relaxation of rice gel
丁玉琴; 赵思明; 熊善柏
2008-01-01
Rice gel was prepared by simulating the production processes of Chinese local rice noodles,and the properties of thermal relaxation and mechanical relaxation during gelatinization were studied by differential scanning calorimetry(DSC) measurement and dynamic rheometer.The results show that during gelatinization,the molecular chains of rice starch undergo the thermal relaxation and mechanical relaxation.During the first heating and high temperature holding processes,the starch crystallites in the rice slurry melt,and the polymer chains stretch and interact,then viscoelastic gel forms.The cooling and low temperatures holding processes result in reinforced networks and decrease the viscoelasticity of the gel.During the second heating,the remaining starch crystallites further melt,the network is reinforced,and the viscoelasticity increases.The viscoelasticity,the molecular conformation and texture of the gel are adjusted by changing the temperature,and finally construct the gel with the textural characteristics of Chinese local rice noodle.
Application of the compensated arrhenius formalism to dielectric relaxation.
Petrowsky, Matt; Frech, Roger
2009-12-17
The temperature dependence of the dielectric rate constant, defined as the reciprocal of the dielectric relaxation time, is examined for several groups of organic solvents. Early studies of linear alcohols using a simple Arrhenius equation found that the activation energy was dependent on the chain length of the alcohol. This paper re-examines the earlier data using a compensated Arrhenius formalism that assumes the presence of a temperature-dependent static dielectric constant in the exponential prefactor. Scaling temperature-dependent rate constants to isothermal rate constants so that the dielectric constant dependence is removed results in calculated energies of activation E(a) in which there is a small increase with chain length. These energies of activation are very similar to those calculated from ionic conductivity data using compensated Arrhenius formalism. This treatment is then extended to dielectic relaxation data for n-alkyl bromides, n-nitriles, and n-acetates. The exponential prefactor is determined by dividing the temperature-dependent rate constants by the Boltzmann term exp(-E(a)/RT). Plotting the prefactors versus the static dielectric constant places the data on a single master curve for each group of solvents.
RESEARCH NOTE Static dielectric constant of the polarizable NCC water model
Millot, Jean-Christophe Soetens Marilia T. C. Martins Costa Claude
The static dielectric constant epsilon0 of the ab initio water model NCC including polarizability (Niesar, U., Corongiu, G., Clementi, E., Kneller, G. R., and Bhattacharya, D. K., 1990, J. phys. Chem., 94, 7949) has been computed by molecular dynamics simulation at 25oC and a density of 1gcm-3. The long range electrostatic interactions are taken into account by the reaction field method. Values of 100 8 and 8ps are found for the static dielectric constant and dielectric relaxation time, respectively.
Wind Tunnel to Atmospheric Mapping for Static Aeroelastic Scaling
Heeg, Jennifer; Spain, Charles V.; Rivera, J. A.
2004-01-01
Wind tunnel to Atmospheric Mapping (WAM) is a methodology for scaling and testing a static aeroelastic wind tunnel model. The WAM procedure employs scaling laws to define a wind tunnel model and wind tunnel test points such that the static aeroelastic flight test data and wind tunnel data will be correlated throughout the test envelopes. This methodology extends the notion that a single test condition - combination of Mach number and dynamic pressure - can be matched by wind tunnel data. The primary requirements for affecting this extension are matching flight Mach numbers, maintaining a constant dynamic pressure scale factor and setting the dynamic pressure scale factor in accordance with the stiffness scale factor. The scaling is enabled by capabilities of the NASA Langley Transonic Dynamics Tunnel (TDT) and by relaxation of scaling requirements present in the dynamic problem that are not critical to the static aeroelastic problem. The methodology is exercised in two example scaling problems: an arbitrarily scaled wing and a practical application to the scaling of the Active Aeroelastic Wing flight vehicle for testing in the TDT.
Stability of Rocket Flight during Burning
T. N. Srivastava
1967-10-01
Full Text Available Stability of the rocket motion during burning is discussed taking into consideration gravity, aerodynamic forces and torques. Conditions for stabilizing the rocket motion are investigated. Analysis for initial and final phases of burning is given separately. Stability regions of the projected motions on two dimensional co-ordinate planes are obtained and thereby stability region of the actual motion is derived. Stability diagrams illustrate statically and dynamically stable and unstable regions.
Relaxation Kinetic Study of Eudragit® NM30D Film Based on Complex Modulus Formalism.
Penumetcha, Sai Sumana; Byrn, Stephen R; Morris, Kenneth R
2015-10-01
This study is aimed at resolving and characterizing the primary (α) and secondary relaxations (β) in Eudragit® NM30D film based on apparent activation energies derived from complex modulus formalism using dielectric analysis (DEA). The glass transition (T g) of the film was determined using differential scanning calorimetry (DSC). The α relaxation corresponding to T g and the β relaxations occurring below T g were probed using DEA. The occurrence of α and β relaxations in Eudragit® NM30D film was elucidated using the complex modulus of the dielectric response employing loss modulus and permittivity data. Activation energies of these relaxations and the fundamental frequency so determined support the assignment of the relaxation pattern in the Eudragit® NM30D film. DEA methodology of the complex modulus formalism is a useful tool for differentiating the α and β relaxation kinetics in Eudragits® not easily studied using traditional thermal methods such as DSC. The kinetics associated with α and β relaxations so determined will provide formulation design support for solid orals that incorporate Eudragit® polymers. As mobility changes can affect stability and diffusion, the dipolar α and β relaxations revealed through DEA analysis may enable a better correlation to functionality of Eudragit® based pharmaceutical dosage forms.
Dielectric relaxation of samarium aluminate
Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T.P. [Bose Institute, Department of Physics, Kolkata (India)
2014-03-15
A ceramic SmAlO{sub 3} (SAO) sample is synthesized by the solid-state reaction technique. The Rietveld refinement of the X-ray diffraction pattern has been done to find the crystal symmetry of the sample at room temperature. An impedance spectroscopy study of the sample has been performed in the frequency range from 50 Hz to 1 MHz and in the temperature range from 313 K to 573 K. Dielectric relaxation peaks are observed in the imaginary parts of the spectra. The Cole-Cole model is used to analyze the dielectric relaxation mechanism in SAO. The temperature-dependent relaxation times are found to obey the Arrhenius law having an activation energy of 0.29 eV, which indicates that polaron hopping is responsible for conduction or dielectric relaxation in this material. The complex impedance plane plot of the sample indicates the presence of both grain and grain-boundary effects and is analyzed by an electrical equivalent circuit consisting of a resistance and a constant-phase element. The frequency-dependent conductivity spectra follow a double-power law due to the presence of two plateaus. (orig.)
Choosing a skeletal muscle relaxant.
See, Sharon; Ginzburg, Regina
2008-08-01
Skeletal muscle relaxants are widely used in treating musculoskeletal conditions. However, evidence of their effectiveness consists mainly of studies with poor methodologic design. In addition, these drugs have not been proven to be superior to acetaminophen or nonsteroidal anti-inflammatory drugs for low back pain. Systematic reviews and meta-analyses support using skeletal muscle relaxants for short-term relief of acute low back pain when nonsteroidal anti-inflammatory drugs or acetaminophen are not effective or tolerated. Comparison studies have not shown one skeletal muscle relaxant to be superior to another. Cyclobenzaprine is the most heavily studied and has been shown to be effective for various musculoskeletal conditions. The sedative properties of tizanidine and cyclobenzaprine may benefit patients with insomnia caused by severe muscle spasms. Methocarbamol and metaxalone are less sedating, although effectiveness evidence is limited. Adverse effects, particularly dizziness and drowsiness, are consistently reported with all skeletal muscle relaxants. The potential adverse effects should be communicated clearly to the patient. Because of limited comparable effectiveness data, choice of agent should be based on side-effect profile, patient preference, abuse potential, and possible drug interactions.
Onsager relaxation of toroidal plasmas
Samain, A.; Nguyen, F.
1997-01-01
The slow relaxation of isolated toroidal plasmas towards their thermodynamical equilibrium is studied in an Onsager framework based on the entropy metric. The basic tool is a variational principle, equivalent to the kinetic equation, involving the profiles of density, temperature, electric potential, electric current. New minimization procedures are proposed to obtain entropy and entropy production rate functionals. (author). 36 refs.
Diagonalization-free implementation of spin relaxation theory for large spin systems
Kuprov, Ilya
2010-01-01
The Liouville space spin relaxation theory equations are reformulated in such a way as to avoid the computationally expensive Hamiltonian diagonalization step, replacing it by numerical evaluation of the integrals in the generalized cumulant expansion. The resulting algorithm is particularly useful in the cases where the static part of the Ha-miltonian is dominated by interactions other than Zeeman (e.g. in quadrupolar reson-ance, low-field EPR and Spin Chemistry). When used together with state space re-striction tools, the algorithm reported is capable of computing full relaxation supero-perators for NMR systems with more than 15 spins.
Faster radial strain relaxation in InAs-GaAs core-shell heterowires
Kavanagh, Karen L. [Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Saveliev, Igor; Blumin, Marina; Ruda, Harry E. [Centre for Advanced Nanotechnology, University of Toronto, 170 College Street, Toronto, Ontario M5S 3E4 (Canada); Swadener, Greg [Mechanical Engineering and Design, Aston University, Aston Triangle, Birmingham B4 7ET (United Kingdom)
2012-02-15
The structure of wurtzite and zinc blende InAs-GaAs (001) core-shell nanowires grown by molecular beam epitaxy on GaAs (001) substrates has been investigated by transmission electron microscopy. Heterowires with InAs core radii exceeding 11 nm, strain relax through the generation of misfit dislocations, given a GaAs shell thickness greater than 2.5 nm. Strain relaxation is larger in radial directions than axial, particularly for shell thicknesses greater than 5.0 nm, consistent with molecular statics calculations that predict a large shear stress concentration at each interface corner.
Diffusion-relaxation distribution functions of sedimentary rocks in different saturation states.
Hürlimann, M D; Flaum, M; Venkataramanan, L; Flaum, C; Freedman, R; Hirasaki, G J
2003-01-01
We present diffusion-relaxation distribution functions measured on four rock cores that were prepared in a succession of different saturation states of brine and crude oil. The measurements were performed in a static gradient field at a Larmor frequency of 1.76 MHz. The diffusion-relaxation distribution functions clearly separate the contributions from the two fluid phases. The results can be used to identify the wetting and non-wetting phase, to infer fluid properties of the phases, and to obtain additional information on the geometrical arrangement of the phases. We also observe effects due to restricted diffusion and susceptibility induced internal gradients.
A comparative study of the effect of soft and hard cervical collars on static postural
Minoo Khalkhali Zavieh
2013-01-01
Full Text Available AbstractBackground and Aim: Using cervical collars is one of the treatment methods for releaving cervical pain. The effect of limb orthotics on proprioception and postural stability has been suggested. There is not sufficient studies about the effect of cervical collars on static and dynamic stability, and the effect of soft and hard collars have not been compared with one another. The objective of this study is investigating and comparing the immediate effect of soft and hard cervical collars on static postural stability in healthy young subjects. Methods & Materials: In standing position on firm surface with closed eyes, both soft and hard collars decreased the stability and there was not any significant difference among collars. In standing positions on soft surface with closed and opened eyes, using none of the soft and hard collars did not change the stability. This quasi experimental study through repeated measure method has been conducted on 65 healthy young male and female college students. Static stability was evaluated by modified Clinical Test for Sensory Interaction and Balance (CTSIB in conditions without collar and by soft and hard cervical collars and were compared between the conditions. Results: Conclusion: Our results suggest that in static conditions, without vision, both collars decrease the stability in healthy young subjects. So considering the evaluation of stability and prevention of balance disturbance during the collar prescription seems to be necessary.
Simultaneous Stabilization of SISO Plants Using Static Output Feedback
1997-01-01
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14 CFR 23.177 - Static directional and lateral stability.
2010-01-01
... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES..., as shown by the tendency to recover from a wings level sideslip with the rudder free, must be... sideslip for these tests must be appropriate to the type of airplane. At larger angles of sideslip, up...
Determination of Static and Dynamic Stability Derivatives Using Beggar
2008-03-01
Ballistic Range Tests of Rolling Aircrafts Models. Technical report, National Aeronautics and Space Administration, January 1961. 6. Boyce , William E. and...Richard C. DiPrima . Elementary Differential Equations and Boundary Value Problems. Wiley, 7th edition, 2000. 7. Chapman, Gary T. and Leslie A. Yates
Static Postural Stability Is Normal in Dyslexic Children.
Brown, Brian; And Others
1985-01-01
An experiment on 15 dyslexic and 23 carefully matched control subjects (10- to 12-year-old males), examining their ability to maintain standing posture with eyes open and closed and with standard and tandem foot placement, revealed no differences under any condition tested and no differences in use of visual information to maintain their posture.…
Static Analysis of Dynamic Languages
Madsen, Magnus
on the behaviour of these languages. A common theme is the reliance on static program analysis to over-approximate the behaviour of programs written in these languages. Specifically, the use of whole-program dataflow analysis. The research challenge of this line of work is the adaption of existing- and invention......Dynamic programming languages are highly popular and widely used. Java- Script is often called the lingua franca of the web and it is the de facto standard for client-side web programming. On the server-side the PHP, Python and Ruby languages are prevalent. What these languages have in common...... is an expressive power which is not easily captured by any static type system. These, and similar dynamic languages, are often praised for their ease-of-use and flexibility. Unfortunately, this dynamism comes at a great cost: The lack of a type system implies that most errors are not discovered until run...
Static Behaviour of Bucket Foundations
Larsen, Kim André
. The monopod concept is investigated in this thesis, regarding the static behaviour from loads relevant to offshore wind turbines. The main issue in this concept is the rotational stiffness of the foundation and the combined capacity dominated by moments. The vertical bearing capacity of bucket foundations...... theory is proposed. The proposed expression applies to plane strain as well as axis-symmetric stress conditions for foundations with smooth or rough bases. A thorough experimental investigation of the static behaviour of bucket foundations subjected to combined loading is carried out. Laboratory tests...... as well as large-scale tests on bucket foundations subjected to low vertical load are performed during this work. Numerical simulations of the tests performed are carried out using the Mohr Coulomb material model and the commercial finite element code ABAQUS. Based on the present work, the finite element...
Static behaviour of induced seismicity
Mignan, Arnaud
2015-01-01
The standard paradigm to describe seismicity induced by fluid injection is to apply nonlinear diffusion dynamics in a poroelastic medium. I show that the spatiotemporal behaviour and rate evolution of induced seismicity can, instead, be expressed by geometric operations on a static stress field produced by volume change at depth. I obtain laws similar in form to the ones derived from poroelasticity while requiring a lower description length. Although fluid flow is known to occur in the ground, it is not pertinent to the behaviour of induced seismicity. The proposed model is equivalent to the static stress model for tectonic foreshocks generated by the Non- Critical Precursory Accelerating Seismicity Theory. This study hence verifies the explanatory power of this theory outside of its original scope.
Static Behaviour of Bucket Foundations
Larsen, Kim André
. The monopod concept is investigated in this thesis, regarding the static behaviour from loads relevant to offshore wind turbines. The main issue in this concept is the rotational stiffness of the foundation and the combined capacity dominated by moments. The vertical bearing capacity of bucket foundations...... theory is proposed. The proposed expression applies to plane strain as well as axis-symmetric stress conditions for foundations with smooth or rough bases. A thorough experimental investigation of the static behaviour of bucket foundations subjected to combined loading is carried out. Laboratory tests...... method is concluded to be a superior method in estimating the post peak behaviour as well as the combined capacity of bucket foundations in relation to the offshore wind turbine problem....
Statics of historic masonry constructions
Como, Mario
2016-01-01
This successful book, which is now appearing in its second edition, presents a comprehensive new Statics of Masonry Constructions. Masonry constructions are the great majority of the buildings in Europe’s historic centres and the most important monuments in its architectural heritage. Given the age of these constructions, the demand for safety assessments and restoration projects is pressing and constant. The book you hold in hands contributes to fill this demand. The second edition integrates the original text of the first edition with new developments, widening and revisions, due to recent research studies achievements. The result is a book that gives a complete picture of the behaviour of the Masonry Constructions. First of all, it gives the fundamentals of its Statics, based on the no-tension assumption, and then it develops the Limit Analysis for the Masonry Constructions. In this framework, through an interdisciplinary approach combining Engineering and Architecture, the book also investigates the sta...
Equivalent Relaxations of Optimal Power Flow
Bose, S; Low, SH; Teeraratkul, T; Hassibi, B
2015-03-01
Several convex relaxations of the optimal power flow (OPF) problem have recently been developed using both bus injection models and branch flow models. In this paper, we prove relations among three convex relaxations: a semidefinite relaxation that computes a full matrix, a chordal relaxation based on a chordal extension of the network graph, and a second-order cone relaxation that computes the smallest partial matrix. We prove a bijection between the feasible sets of the OPF in the bus injection model and the branch flow model, establishing the equivalence of these two models and their second-order cone relaxations. Our results imply that, for radial networks, all these relaxations are equivalent and one should always solve the second-order cone relaxation. For mesh networks, the semidefinite relaxation and the chordal relaxation are equally tight and both are strictly tighter than the second-order cone relaxation. Therefore, for mesh networks, one should either solve the chordal relaxation or the SOCP relaxation, trading off tightness and the required computational effort. Simulations are used to illustrate these results.
Static Analysis of Mobile Programs
2017-02-01
PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) Air...and then use static analysis to verify them. In the end we pursued this idea successfully for several differnet properties and developed novel...difficult to develop with enough precision. In [3], we establish a connection between compositional analyses and modular lattices, which require
An Eigenstructure Assignment for a Static Synchronous Compensator
Ahmad N. Al-Husban
2009-01-01
Full Text Available Problem statement: Power flow through an AC transmission line is influenced by three basic electrical parameters, which are line impedance, magnitudes and phase-shift angle between the sending and receiving voltages. Therefore, the change in any of the three basic parameters means a change in the power flow through the transmission line. The aims of this research paper are: increase the power transfer capability of transmission systems, minimize the transmission losses, support a good voltage profile and retain system stability under large disturbances. Study the use of eigenstructure techniques for state feedback control of the power system static compensator. Therefore, the mathematical analysis was performed for eigenvector assignment, power flow transmission line and for the static compensator analysis based on the transformation of the three-phase into d-q frame. Approach: A novel control method for regulating the power system in case of abnormal conditions was carried out. The system considered is a static synchronous compensator. The study includes a detailed mathematical analysis of the impact of the shunt compensator on the power flow; investigation of the system constraints and their effects on the static compensator control; in addition simulation of static compensator to control a transmitted active power flow on the transmission line. The conducted method provides a way of constructing the state feedback gain matrix to satisfy a certain prescribed performance. Results: The solutions of the obtained equation were conducted using the computer simulation method for both open-loop and static compensator techniques. The result shows fast tracking of the power flow transient response when using the static compensator technique comparing with open-loop technique. However, the same trend of the behavior was observed for all cases. Conclusion: A new method for developing a parameterized feedback matrix that assigns a closed-loop prespecified
A Numerical Study of Automated Dynamic Relaxation for Nonlinear Static Tensioned Structures.
1987-10-01
RS Munn). New London. C F; Code TA131 (De lit Crui7). New Londonl. CT: Lib (Code 4533), Newport, RI OCNR Code 1121 (EA Silva ). Arlington. VA; Code...WELLSPRING (C0MM IL iZarecor. Nlarshall. VA WESTERN INSTRUMENT (CORP Ventura . (A WESTINGHOUSE ELE-(’TRIC(OR’ librars . Pgittsbu, . P’A: ( xtec Di\\) I it
Organic semiconductors: What makes the spin relax?
Bobbert, Peter A.
2010-04-01
Spin relaxation in organic materials is expected to be slow because of weak spin-orbit coupling. The effects of deuteration and coherent spin excitation show that the spin-relaxation time is actually limited by hyperfine fields.
Relaxation Techniques to Manage IBS Symptoms
... the Day Art of IBS Gallery Contact Us Relaxation Techniques to Manage IBS Symptoms Details Content Last Updated: ... Topic Psychological Treatments Understanding Stress Cognitive Behavioral Therapy Relaxation Techniques for IBS You’ve been to the doctor ...
Static or dynamic intramedullary nailing of femur and tibia.
Omerovic, Djemil; Lazovic, Faruk; Hadzimehmedagic, Amel
2015-04-01
The basic principle of non-surgical fracture treatment is to restore the original anatomical position of fractured fragments by different techniques, without direct access to the bone and without further traumatizing of tissues. Intramedullary nailing is synthesis and consolidation of fracture fragments with the main goal to gain strength and permanent placement of the implants. Two techniques of intramedullary osteosynthesis are used: with dynamic or with static intramedullary nail. Dynamization include conversion of static nail by removing screws from the longest fragment. The aim of this study is to determine whether there is a difference in the speed and quality of healing of the type A and B fractures of the femur and tibia treated by static or dynamic intramedullary nails and to compare the results. The study was conducted at the Clinic for Orthopaedics and Traumatology, Clinical Center University Sarajevo from January 2004 to June 2009. The study was retrospective-prospective, manipulative, controlled and it was conducted on a total of 129 patients with closed fractures of the diaphysis of the femur and tibia type A and type B, with different segments of bone, regardless of sex and age structure, with the exception of children under 14 years of age. Precisely there were 47 patients with femoral fractures and 82 patients with tibial fractures. The average number of weeks of healing femoral and tibial fractures was slightly in advantage of static intramedullary osteosynthesis, it was 17.08 weeks (SD=3.382). The average number of weeks of healing in 23 patients with fractures of the femur, treated by dynamic intramedullary osteosynthesis was 17.83 (SD=2.978). We can conclude that static intramedullary nailing osteosynthesis unable movements between fragments which directly stimulates bone formation and formation of minimal callus. Static intramedullary osteosynthesis resolve the problem of stabilizing the fracture, limb shortening and rotation of fragments.
Trivedi, C. M.; Rana, V. A.; Hudge, P. G.; Kumbharkhane, A. C.
2016-08-01
Complex permittivity spectra of binary mixtures of varying concentrations of β-picoline and Methanol (MeOH) have been obtained using time domain reflectometry (TDR) technique over frequency range 10 MHz to 25 GHz at 283.15, 288.15, 293.15 and 298.15 K temperatures. The dielectric relaxation parameters namely static permittivity (ɛ0), high frequency limit permittivity (ɛ∞1) and the relaxation time (τ) were determined by fitting complex permittivity data to the single Debye/Cole-Davidson model. Complex nonlinear least square (CNLS) fitting procedure was carried out using LEVMW software. The excess permittivity (ɛ0E) and the excess inverse relaxation time (1/τ)E which contain information regarding molecular structure and interaction between polar-polar liquids were also determined. From the experimental data, parameters such as effective Kirkwood correlation factor (geff), Bruggeman factor (fB) and some thermo dynamical parameters have been calculated. Excess parameters were fitted to the Redlich-Kister polynomial equation. The values of static permittivity and relaxation time increase nonlinearly with increase in the mol-fraction of MeOH at all temperatures. The values of excess static permittivity (ɛ0E) and the excess inverse relaxation time (1/τ)E are negative for the studied β-picoline — MeOH system at all temperatures.
A Pedagogical Model of Static Friction
Pickett, Galen T
2015-01-01
While dry Coulombic friction is an elementary topic in any standard introductory course in mechanics, the critical distinction between the kinetic and static friction forces is something that is both hard to teach and to learn. In this paper, I describe a geometric model of static friction that may help introductory students to both understand and apply the Coulomb static friction approximation.
30 CFR 18.26 - Static electricity.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Static electricity. 18.26 Section 18.26 Mineral... § 18.26 Static electricity. Nonmetallic rotating parts, such as belts and fans, shall be provided with a means to prevent an accumulation of static electricity. ...
In-Flight Pitot-Static Calibration
Foster, John V. (Inventor); Cunningham, Kevin (Inventor)
2016-01-01
A GPS-based pitot-static calibration system uses global output-error optimization. High data rate measurements of static and total pressure, ambient air conditions, and GPS-based ground speed measurements are used to compute pitot-static pressure errors over a range of airspeed. System identification methods rapidly compute optimal pressure error models with defined confidence intervals.
Static Analysis Alert Audits: Lexicon and Rules
2016-11-04
DISTRIBUTION STATEMENT A] This material has been approved for public release and unlimited distribution. REV-03.18.2016.0 Static Analysis Alert Audits...unlimited distribution. Background: Automatic Alert Classification Static Analysis Tool(s) Alerts Alert Consolidation (SCALe) Potential Rule...Automatic Alert Classification Static Analysis Tool(s) Alerts Alert Consolidation (SCALe) Potential Rule Violations Auditing Determinations ML
A broadband damper design inspired by cartilage-like relaxation mechanisms
Liu, Lejie; Usta, Ahmet D.; Eriten, Melih
2017-10-01
In this study, we introduce a broadband damper design inspired by the cartilage-like relaxation mechanisms. In particular, we study broadband (static to 10 kHz) dissipative properties of model cartilage systems by probe-based static and dynamic indentation, and validate that fractional Zener models can simulate the empirical data up to a desirable accuracy within the frequency range of interest. Utilizing these observations, we design a composite damper design where a poroelastic layer is sandwiched between two hard materials, and load transfer occurs across interfaces with multiple length scales. Modeling those interfaces with fractional Zener elements in parallel configuration, and manipulating the distribution of the Zener elements across different peak relaxation frequencies, we obtain a relatively constant loss factor within an unprecedented frequency range (3-3 kHz). We also discuss how these findings can be employed in a practical damping design.
Plasmon-mediated energy relaxation in graphene
Ferry, D. K. [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706 (United States); Somphonsane, R. [Department of Physics, King Mongkut' s Institute of Technology, Ladkrabang, Bangkok 10520 (Thailand); Ramamoorthy, H.; Bird, J. P. [Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260-1500 (United States)
2015-12-28
Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.
Surface properties and exponential stress relaxations of mammalian meibum films.
Eftimov, Petar; Yokoi, Norihiko; Tonchev, Vesselin; Nencheva, Yana; Georgiev, Georgi As
2017-03-01
The surface properties of meibomian secretion (MGS), the major constituent of the tear film (TF) lipid layer, are of key importance for TF stability. The interfacial properties of canine, cMGS, and feline, fMGS, meibum films were studied using a Langmuir surface balance. These species were selected because they have blinking frequency and TF stability similar to those of humans. The sample's performance during dynamic area changes was evaluated by surface pressure (π)-area (A) isocycles and the layer structure was monitored with Brewster angle microscopy. The films' dilatational rheology was probed via the stress-relaxation technique. The animal MGS showed similar behavior both between each other and with human MGS (studied previously). They form reversible, non-collapsible, multilayer thick films. The relaxations of canine, feline, and human MGS films were well described by double exponential decay reflecting the presence of two processes: (1) fast elastic process, with characteristic time τ 100 s-emphasizing the meibum layers viscoelasticity. The temperature decrease from 35 to 25 °C resulted in decreased thickness and lateral expansion of all MGS layers accompanied with increase of the π/A hysteresis and of the elastic process contribution to π relaxation transients. Thus, MGS films of mammals with similar blinking frequency and TF stability have similar surface properties and stress relaxations unaltered by the interspecies MGS compositional variations. Such knowledge may impact the selection of animal mimics of human MGS and on a better understanding of lipid classes' impact on meibum functionality.
Collisionless Relaxation of Stellar Systems
Kandrup, H E
1998-01-01
The objective of the work summarised here has been to exploit and extend ideas from plasma physics and accelerator dynamics to formulate a unified description of collisionless relaxation that views violent relaxation, Landau damping, and phase mixing as (manifestations of) a single phenomenon. This approach embraces the fact that the collisionless Boltzmann equation (CBE), the basic object of the theory, is an infinite-dimensional Hamiltonian system, with the distribution function f playing the role of the fundamental dynamical variable, and that, interpreted appropriately, an evolution described by the other Hamiltonian system. Equilibrium solutions correspond to extremal points of the Hamiltonian subject to the constraints associated with Liouville's Theorem. Stable equilibria correspond to energy minima. The evolution of a system out of equilibrium involves (in general nonlinear) phase space oscillations which may -- or may not -- interfere destructively so as to damp away.
Collisionless Relaxation of Stellar Systems
Kandrup, Henry E.
1999-08-01
The objective of the work summarized here has been to exploit and extend ideas from plasma physics and accelerator dynamics to formulate a unified description of collisionless relaxation of stellar systems that views violent relaxation, Landau damping, and phase mixing as (manifestations of) a single phenomenon. This approach embraces the fact that the collisionless Boltzmann equation (CBE), the basic object of the theory, is an infinite-dimensional Hamiltonian system, with the distribution function f playing the role of the fundamental dynamical variable, and that, interpreted appropriately, an evolution described by the CBE is no different fundamentally from an evolution described by any other Hamiltonian system. Equilibrium solutions f0 correspond to extremal points of the Hamiltonian subject to the constraints associated with Liouville's Theorem. Stable equilibria correspond to energy minima. The evolution of a system out of equilibrium involves (in general nonlinear) phase space oscillations which may - or may not - interfere destructively so as to damp away.
Kinetic activation-relaxation technique
Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand
2011-10-01
We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).
Kinetic activation-relaxation technique.
Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand
2011-10-01
We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).
Brief relaxation training program for hospital employees.
Balk, Judith L; Chung, Sheng-Chia; Beigi, Richard; Brooks, Maria
2009-01-01
Employee stress leads to attrition, burnout, and increased medical costs. We aimed to assess if relaxation training leads to decreased stress levels based on questionnaire and thermal biofeedback. Thirty-minute relaxation training sessions were conducted for hospital employees and for cancer patients. Perceived Stress levels and skin temperature were analyzed before and after relaxation training.
POS Tagging Using Relaxation Labelling
Padro, L
1995-01-01
Relaxation labelling is an optimization technique used in many fields to solve constraint satisfaction problems. The algorithm finds a combination of values for a set of variables such that satisfies -to the maximum possible degree- a set of given constraints. This paper describes some experiments performed applying it to POS tagging, and the results obtained. It also ponders the possibility of applying it to word sense disambiguation.
Spin relaxation in metallic ferromagnets
Berger, L.
2011-02-01
The Elliott theory of spin relaxation in metals and semiconductors is extended to metallic ferromagnets. Our treatment is based on the two-current model of Fert, Campbell, and Jaoul. The d→s electron-scattering process involved in spin relaxation is the inverse of the s→d process responsible for the anisotropic magnetoresistance (AMR). As a result, spin-relaxation rate 1/τsr and AMR Δρ are given by similar formulas, and are in a constant ratio if scattering is by solute atoms. Our treatment applies to nickel- and cobalt-based alloys which do not have spin-up 3d states at the Fermi level. This category includes many of the technologically important magnetic materials. And we show how to modify the theory to apply it to bcc iron-based alloys. We also treat the case of Permalloy Ni80Fe20 at finite temperature or in thin-film form, where several kinds of scatterers exist. Predicted values of 1/τsr and Δρ are plotted versus resistivity of the sample. These predictions are compared to values of 1/τsr and Δρ derived from ferromagnetic-resonance and AMR experiments in Permalloy.
Relaxation response in femoral angiography.
Mandle, C L; Domar, A D; Harrington, D P; Leserman, J; Bozadjian, E M; Friedman, R; Benson, H
1990-03-01
Immediately before they underwent femoral angiography, 45 patients were given one of three types of audiotapes: a relaxation response tape recorded for this study, a tape of contemporary instrumental music, or a blank tape. All patients were instructed to listen to their audiotape during the entire angiographic procedure. Each audiotape was played through earphones. Radiologists were not told the group assignment or tape contents. The patients given the audiotape with instructions to elicit the relaxation response (n = 15) experienced significantly less anxiety (P less than .05) and pain (P less than .001) during the procedure, were observed by radiology nurses to exhibit significantly less pain (P less than .001) and anxiety (P less than .001), and requested significantly less fentanyl citrate (P less than .01) and diazepam (P less than .01) than patients given either the music (n = 14) or the blank (n = 16) control audiotapes. Elicitation of the relaxation response is a simple, inexpensive, efficacious, and practical method to reduce pain, anxiety, and medication during femoral angiography and may be useful in other invasive procedures.
Measurement of relaxation times by NMR-CT of electric superconductivity
Shimizu, Koji; Yoshitoshi, Motosada (Shimadzu Corp., Kyoto (Japan)); Narise, Shoji; Hirakawa, Kogi
1984-08-01
Relaxation curves of T/sub 1/ in various tissues of the brain in patients with cerebral tumor and in healthy controls were obtained by saturation-recovery and inversion-recovery methods, whereby T/sub 1/ values were calculated. The results obtained were in good agreement with in vitro measurement results of excised brain tissues. Prolongation of T/sub 1/ values was evidently observed with increasing the strength of static magnetic field.
On the Relaxation Dynamics of Disordered Systems
Dobramysl, Ulrich
We investigate the properties of two distinct disordered systems: the two-species predator-prey Lotka-Volterra model with rate variability, and an elastic line model to simulate vortex lines in type-II superconductors. We study the effects of intrinsic demographic variability with inheritance in the reaction rates of the Lotka-Volterra model via zero-dimensional Monte Carlo simulations as well as two-dimensional lattice simulations. Individuals of each species are assigned inheritable predation efficiencies during their creation, leading to evolutionary dynamics and thus population-level optimization. We derive an effective subspecies mean-field theory and compare its results to our numerical data. Furthermore, we introduce environmental variability via quenched spatial reaction-rate randomness. We investigate the competing effects and relative importance of the two types of variability, and find that both lead to a remarkable enhancement of the species densities, while the aforementioned optimization effects are essentially neutral in the densities. Additionally, we collected extinction time histograms for small systems and find a marked increase in the stability of the populations against extinction due to the presence of variability. We employ an elastic line model to investigate the steady-state properties and non-equilibrium relaxation kinetics of magnetic vortex lines in disordered type-II superconductors. To this end, we developed a versatile and efficient Langevin molecular dynamics simulation code, allowing us to do a careful study of samples with or without vortex-vortex interactions or disorder allows us to disentangle the various complex relaxational features present in this system and investigate their origin. In particular, we compare disordered samples with randomly distributed point defects versus correlated columnar defects. We extract two-time quantities such as the mean-square displacement, the height and density correlations, to investigate the
Spin-liquid behavior and weak static magnetism in pyrochlore Pr2Ir2O7
Heffner, R H [Los Alamos National Laboratory; Maclaughlin, D E [NON LANL; Nakatsuji, S [NON LANL; Machida, Y [NON LANL
2008-01-01
Muon spin relaxation experiments have been performed in powder samples of the pyrochlore iridate Pr{sub 2}Ir{sub 2}O{sub 7} for temperatures in the range 0.02-250 K. Two-component muon spin relaxation functions are observed up to {approx}> 150 K, indicating static magnetism with a freezing temperature T{sub f} of this value or higher. The static muon spin relaxation rate {Delta}. suggests weak-moment freezing ({approx} 10{sup -1} {micro}{sub B} at T = 0), probably due to Ir{sup 4+} spin ordering as in isostructural Y{sub 2}Ir{sub 2}O{sub 7}. The temperature dependence of {Delta} is highly unusual, decreasing smoothly by orders of magnitude but remaining nonzero for T < T{sub f}. The smoothness of {Delta}(T) suggests that Pr{sup 3+} moments do not order down to 0.025 K. The dynamic relaxation rate {Lambda} increases markedly below {approx}20 K, indicating a shift of spin fluctuation noise power to low frequencies in the spin-liquid state. At low temperatures {Lambda} is strong and temperature-independent, indicative of numerous low-lying spin excitations as is common in frustrated antiferromagnets.
A Minimum Leakage Quasi-Static RAM Bitcell
Adam Teman
2011-05-01
Full Text Available As SRAMs continue to grow and comprise larger percentages of the area and power consumption in advanced systems, the need to minimize static currents becomes essential. This brief presents a novel 9T Quasi-Static RAM Bitcell that provides aggressive leakage reduction and high write margins. The quasi-static operation method of this cell, based on internal feedback and leakage ratios, minimizes static power while maintaining sufficient, albeit depleted, noise margins. This paper presents the concept of the novel cell, and discusses the stability of the cell under hold, read and write operations. The cell was implemented in a low-power 40 nm TSMC process, showing as much as a 12× reduction in leakage current at typical conditions, as compared to a standard 6T or 8T bitcell at the same supply voltage. The implemented cell showed full functionality under global and local process variations at nominal and low voltages, as low as 300 mV.
Zhu, Ming; Liu, Tingting; Wang, Shu; Zhang, Kesheng
2017-08-01
Existing two-frequency reconstructive methods can only capture primary (single) molecular relaxation processes in excitable gases. In this paper, we present a reconstructive method based on the novel decomposition of frequency-dependent acoustic relaxation spectra to capture the entire molecular multimode relaxation process. This decomposition of acoustic relaxation spectra is developed from the frequency-dependent effective specific heat, indicating that a multi-relaxation process is the sum of the interior single-relaxation processes. Based on this decomposition, we can reconstruct the entire multi-relaxation process by capturing the relaxation times and relaxation strengths of N interior single-relaxation processes, using the measurements of acoustic absorption and sound speed at 2N frequencies. Experimental data for the gas mixtures CO2-N2 and CO2-O2 validate our decomposition and reconstruction approach.
Static Charge Development on Explosives .
K. Raha
1991-01-01
Full Text Available Static charge development character of some of the important explosive crystals have been predicted on the basis of their crystal class and symmetry. Among the important mechanism of charge development, the piezoelectric and pyroelectric characters have been considered. Ammonium trinitrate, ammonium nitrate, m-dinitro-benzene, trinitro-toluene, styphnic acid, beeta-lead styphnate, 4,4'dinitro-dipheny1, a-hexamethylenetetranitramine, nitroguanidine, picric acid, dimethylnitramine, a-lead azide and beeta-lead azide are pyroelectric in nature, whereas pentaerythritol tetranitrate, picryliodide, hexamethylenetranitramine, tetranitromethane and trinitroethane are piezoelectric in nature.
Static Analysis for Dynamic XML
Christensen, Aske Simon; Møller, Anders; Schwartzbach, Michael Ignatieff
2002-01-01
We describe the summary graph lattice for dataflow analysis of programs that dynamically construct XML documents. Summary graphs have successfully been used to provide static guarantees in the JWIG language for programming interactive Web services. In particular, the JWIG compiler is able to check...... validity of dynamically generated XHTML documents and to type check dynamic form data. In this paper we present summary graphs and indicate their applicability for various scenarios. We also show that the expressive power of summary graphs is similar to that of the regular expression types from XDuce......, but that the extra structure in summary graphs makes them more suitable for certain program analyses....
Static Analysis for Dynamic XML
Christensen, Aske Simon; Møller, Anders; Schwartzbach, Michael Ignatieff
2002-01-01
We describe the summary graph lattice for dataflow analysis of programs that dynamically construct XML documents. Summary graphs have successfully been used to provide static guarantees in the JWIG language for programming interactive Web services. In particular, the JWIG compiler is able to check...... validity of dynamically generated XHTML documents and to type check dynamic form data. In this paper we present summary graphs and indicate their applicability for various scenarios. We also show that the expressive power of summary graphs is similar to that of the regular expression types from XDuce...
Static Validation of Security Protocols
Bodei, Chiara; Buchholtz, Mikael; Degano, P.;
2005-01-01
We methodically expand protocol narrations into terms of a process algebra in order to specify some of the checks that need to be made in a protocol. We then apply static analysis technology to develop an automatic validation procedure for protocols. Finally, we demonstrate that these techniques ...... suffice to identify several authentication flaws in symmetric and asymmetric key protocols such as Needham-Schroeder symmetric key, Otway-Rees, Yahalom, Andrew secure RPC, Needham-Schroeder asymmetric key, and Beller-Chang-Yacobi MSR...
The application of polymethylene waxes as conditioning agent in hair relaxers.
Vermeulen, Shani; Van Rensburg, Audrey Jansen; Van Der Merwe, Belinda; Shalvoy, Richard; Willford, Suzanne
2004-01-01
Hair relaxers are harsh chemical treatments that leave the hair dull, dry and limp. There is a constant need for improvement of these products to make them milder and incorporate conditioning properties. Because of the high pH of relaxer or hair straightening systems, most quaternized (conditioning) ingredients are unstable and slowly break down to release ammonia over time, having no conditioning effects by the time the consumers use them. This paper discusses the partial substitution of the fatty alcohols that are traditionally used in relaxer systems with polymethylene wax and the benefits derived from using them. The study included the investigation of synergies among the ingredients, the stabilities of the various systems and comparisons with commercially available systems. The polymethylene wax, used in combination with the mineral oil gel and phosphate salt, coats the hair during the relaxing process, leaving it shiny, soft and conditioned as opposed to the poor condition of the hair relaxed by traditional, commercially available NaOH and LiOH relaxers. An additional benefit of using polymethylene wax in relaxer systems is that the conditioning agents that are normally added to the neutralizing shampoo to repair or mask the damage as a result of the relaxing process can be omitted.
Time of relaxation in dusty plasma model
Timofeev, A. V.
2015-11-01
Dust particles in plasma may have different values of average kinetic energy for vertical and horizontal motion. The partial equilibrium of the subsystems and the relaxation processes leading to this asymmetry are under consideration. A method for the relaxation time estimation in nonideal dusty plasma is suggested. The characteristic relaxation times of vertical and horizontal motion of dust particles in gas discharge are estimated by analytical approach and by analysis of simulation results. These relaxation times for vertical and horizontal subsystems appear to be different. A single hierarchy of relaxation times is proposed.
Analysis of Static Instability of an Asymmetric, Rotating Sand-Wich Beam
P. R. Dash
2012-01-01
Full Text Available The static stability of an asymmetric, rotating sandwich beam subjected to an axial pulsating load has been investigated for pinned-pinned and fixed-free boundary conditions. The equations of motion and associated boundary conditions have been obtained by using the Hamilton's energy principle. Then, these equations of motion and the associated boundary conditions have been nondimensionalised. A set of Hill's equations are obtained from the nondimensional equations of motion by the application of the general Galerkin method. The static buckling loads have been obtained from Hill's equations. The influences of geometric parameters and rotation parameters on the nondimensional static buckling loads have been investigated.
Immiscible multicomponent lattice Boltzmann model for fluids with high relaxation time ratio
Tao Jiang; Qiwei Gong; Ruofan Qiu; Anlin Wang
2014-10-01
An immiscible multicomponent lattice Boltzmann model is developed for fluids with high relaxation time ratios, which is based on the model proposed by Shan and Chen (SC). In the SC model, an interaction potential between particles is incorporated into the discrete lattice Boltzmann equation through the equilibrium velocity. Compared to the SC model, external forces in our model are discretized directly into the discrete lattice Boltzmann equation, as proposed by Guo et al. We develop it into a new multicomponent lattice Boltzmann (LB) model which has the ability to simulate immiscible multicomponent fluids with relaxation time ratio as large as 29.0 and to reduce `spurious velocity’. In this work, the improved model is validated and studied using the central bubble case and the rising bubble case. It finds good applications in both static and dynamic cases for multicomponent simulations with different relaxation time ratios.
Relaxation Study of N-Submitted Amides with Alcohol Mixtures by Time Domain Reflectometry
A. Arunkumar
2016-08-01
Full Text Available Using Time Domain Reflectometry (TDR, dielectric relaxation studies have been carried out on binary mixtures of amides (N-methylacetamide, N,N-dimethylacetamide with alcohols (1-butanol, 1-pentanol for various concentrations over the frequency range from 10 MHz to 10 GHz at 303 K. The Kirkwood correlation factor and excess dielectric constant properties were determined and discussed to yield information on the molecular interactions of the systems. The relaxation time is vary with the chain length of alcohols and substituted amides are noticed. The Bruggeman plot shows a deviation from linearity. This deviation was attributed to some sort of molecular interaction which may take place between the alcohols and substituted amides. The excess static permittivity and excess inverse relaxation time values vary from negative to positive for all the systems indicating the solute-solvent interaction to exist between alcohols and substituted amides for all the dynamics of the mixture.
Relaxation transition due to different cooling processes in a superconducting levitation system
Zhou, You-He; Zhang, Xing-Yi; Zhou, Jun
2008-06-01
We present an experimental study of relaxation of vertical and horizontal force components in a high-temperature superconducting levitation system, with different initial cooling process after fixing the levitated body in an expected position statically. In the experiment, the bulk YBaCuO cylinder superconductor and the permanent magnet disk are employed. For a selected levitation height (LH) and a lateral displacement (LD) of the system, the experimental results show that the relaxations of the vertical and horizontal forces are strongly dependent on the initial cooling height (CH). With CH decreasing, the transition of the lateral force from repulsion to attraction is found as well as the changing characteristics with time from decrease to increase. Additionally, when LH is fixed at the CH, the transition phenomenon is also observed in the levitation force behavior and their relaxation under different LDs.
5 Things To Know About Relaxation Techniques for Stress
... X Y Z 5 Things To Know About Relaxation Techniques for Stress Share: When you’re under stress, ... creating the relaxation response through regular use of relaxation techniques could counteract the negative effects of stress. Relaxation ...
Electrowetting -- from statics to dynamics.
Chen, Longquan; Bonaccurso, Elmar
2014-08-01
More than one century ago, Lippmann found that capillary forces can be effectively controlled by external electrostatic forces. As a simple example, by applying a voltage between a conducting liquid droplet and the surface it is sitting on we are able to adjust the wetting angle of the drop. Since Lippmann's findings, electrocapillary phenomena - or electrowetting - have developed into a series of tools for manipulating microdroplets on solid surfaces, or small amounts of liquids in capillaries for microfluidic applications. In this article, we briefly review some recent progress of fundamental understanding of electrowetting and address some still unsolved issues. Specifically, we focus on static and dynamic electrowetting. In static electrowetting, we discuss some basic phenomena found in DC and AC electrowetting, and some theories about the origin of contact angle saturation. In dynamic electrowetting, we introduce some studies about this rather recent area. At last, we address some other capillary phenomena governed by electrostatics and we give an outlook that might stimulate further investigations on electrowetting.
Comparative statics of games between relatives.
Milchtaich, Igal
2006-03-01
According to Hamilton's theory of kin selection, species tend to evolve behavior such that each organism appears to be attempting to maximize its inclusive fitness. In particular, two neighbors are likely to help each other if the cost of doing so is less than the benefit multiplied by r, their coefficient of relatedness. Since the latter is less than unity, mutual altruism benefits both neighbors. However, is it theoretically possible that acting so as to maximize the inclusive, rather than personal, fitness may harm both parties. This may occur in strategic symmetric pairwise interactions (more specifically, nxn games), in which the outcome depends on both sides' actions. In this case, the equilibrium outcome may be less favorable to the interactants' personal fitness than if each of them acted so as to maximize the latter. This paper shows, however, that such negative effect of relatedness on fitness is incompatible with evolutionary stability. If the symmetric equilibrium strategies are evolutionarily stable, a higher coefficient of relatedness can only entail higher personal fitness for the two neighbors. This suggests that negative comparative statics as above are not likely to occur in nature.
Plasma Relaxation in Hall Magnetohydrodynamics
Shivamoggi, B K
2011-01-01
Parker's formulation of isotopological plasma relaxation process in magnetohydrodynamics (MHD) is extended to Hall MHD. The torsion coefficient alpha in the Hall MHD Beltrami condition turns out now to be proportional to the "potential vorticity." The Hall MHD Beltrami condition becomes equivalent to the "potential vorticity" conservation equation in two-dimensional hydrodynamics if the Hall MHD Lagrange multiplier beta is taken to be proportional to the "potential vorticity" as well. The winding pattern of the magnetic field lines in Hall MHD then appears to evolve in the same way as "potential vorticity" lines in 2D hydrodynamics.
Spectral Estimation of NMR Relaxation
Naugler, David G.; Cushley, Robert J.
2000-08-01
In this paper, spectral estimation of NMR relaxation is constructed as an extension of Fourier Transform (FT) theory as it is practiced in NMR or MRI, where multidimensional FT theory is used. nD NMR strives to separate overlapping resonances, so the treatment given here deals primarily with monoexponential decay. In the domain of real error, it is shown how optimal estimation based on prior knowledge can be derived. Assuming small Gaussian error, the estimation variance and bias are derived. Minimum bias and minimum variance are shown to be contradictory experimental design objectives. The analytical continuation of spectral estimation is constructed in an optimal manner. An important property of spectral estimation is that it is phase invariant. Hence, hypercomplex data storage is unnecessary. It is shown that, under reasonable assumptions, spectral estimation is unbiased in the context of complex error and its variance is reduced because the modulus of the whole signal is used. Because of phase invariance, the labor of phasing and any error due to imperfect phase can be avoided. A comparison of spectral estimation with nonlinear least squares (NLS) estimation is made analytically and with numerical examples. Compared to conventional sampling for NLS estimation, spectral estimation would typically provide estimation values of comparable precision in one-quarter to one-tenth of the spectrometer time when S/N is high. When S/N is low, the time saved can be used for signal averaging at the sampled points to give better precision. NLS typically provides one estimate at a time, whereas spectral estimation is inherently parallel. The frequency dimensions of conventional nD FT NMR may be denoted D1, D2, etc. As an extension of nD FT NMR, one can view spectral estimation of NMR relaxation as an extension into the zeroth dimension. In nD NMR, the information content of a spectrum can be extracted as a set of n-tuples (ω1, … ωn), corresponding to the peak maxima
Relaxing Chosen-Ciphertext Security
Canetti, Ran; Krawczyk, Hugo; Nielsen, Jesper Buus
2003-01-01
Security against adaptive chosen ciphertext attacks (or, CCA security) has been accepted as the standard requirement from encryption schemes that need to withstand active attacks. In particular, it is regarded as the appropriate security notion for encryption schemes used as components within...... “for most practical purposes.” We propose a relaxed variant of CCA security, called Replayable CCA (RCCA) security. RCCA security accepts as secure the non-CCA (yet arguably secure) schemes mentioned above; furthermore, it suffices for most existing applications of CCA security. We provide three...
Structures and Stabilization Mechanisms in Chemically Stabilized Ceramics
Gai-Boyes, Pratibha L.; Saltzberg, Michael A.; Vega, Alexander
1993-09-01
Structural complexities and disorder in chemically stabilized cristobalites (CSC), which are room temperature silica-based ceramics, prepared by a wet chemical route, are described. CSC displays many of the structural characteristics of the high temperature cristobalite, elucidated by HREM and X-ray diffraction. In-situ electron diffraction and NMR results suggest that the disorder is structural and is static.
Madhukar N Shinde; Ravindra B Talware; Pravin G Hudge; Yogesh S Joshi; Ashok C Kumbharkhane
2012-02-01
The complex permittivity, static dielectric constant and relaxation time for 1,3-propanediol, 1,4-dioxane and their mixtures have been studied using time domain reﬂectometry (TDR). The excess permittivity, excess inverse relaxation time and Kirkwood correlation factor have also been determined at various concentrations of dioxane. Hydrogen bonded theory was applied to compute the correlation terms for the mixtures. The Bruggeman model for the nonlinear case has been ﬁtted to the dielectric data for mixtures.
The Predictive Validity of the Static-99, Static-99R, and Static-2002/R: Which One to Use?
Reeves, Sophie G; Ogloff, James R P; Simmons, Melanie
2017-06-01
The use of Static tools (Static-99, Static-99R, Static-2002, and Static-2002R) in risk decision making involving sexual offenders is widespread internationally. This study compared the predictive accuracy and incremental validity of four Static risk measures in a sample of 621 Australian sexual offenders. Results indicated that approximately 45% of the sample recidivated (with 18.8% committing sexual offenses). All of the Static measures investigated yielded moderate predictive validity for sexual recidivism, which was comparable with other Australian and overseas studies. Area under the curve (AUC) values for the four measures across the 5-, 10-, and 15-year intervals ranged from .67 to .69. All of the Static measures discriminated quite well between low-risk and high-risk sexual offenders but less well for the moderate risk categories. When pitted together, none of the tools accounted for additional variance in sexual recidivism, above and beyond what the other measures accounted for. The overall results provide support for the use of Static measures as a component of risk assessment and decision making with Australian sexual offending populations. The limitations of this study and recommendations for further research are also discussed.
Static and dynamic properties of large polymer melts in equilibrium
Hsu, Hsiao-Ping; Kremer, Kurt
2016-04-01
We present a detailed study of the static and dynamic behaviors of long semiflexible polymer chains in a melt. Starting from previously obtained fully equilibrated high molecular weight polymer melts [G. Zhang et al., ACS Macro Lett. 3, 198 (2014)], we investigate their static and dynamic scaling behaviors as predicted by theory. We find that for semiflexible chains in a melt, results of the mean square internal distance, the probability distributions of the end-to-end distance, and the chain structure factor are well described by theoretical predictions for ideal chains. We examine the motion of monomers and chains by molecular dynamics simulations using the ESPResSo++ package. The scaling predictions of the mean squared displacement of inner monomers, center of mass, and relations between them based on the Rouse and the reptation theory are verified, and related characteristic relaxation times are determined. Finally, we give evidence that the entanglement length Ne,PPA as determined by a primitive path analysis (PPA) predicts a plateau modulus, GN 0 = /4 5 ( ρ k B T / N e ) , consistent with stresses obtained from the Green-Kubo relation. These comprehensively characterized equilibrium structures, which offer a good compromise between flexibility, small Ne, computational efficiency, and small deviations from ideality, provide ideal starting states for future non-equilibrium studies.
Carson, William; Lindemuth, Kathleen; Mich, John; White, K. Preston; Parker, Peter A.
2009-01-01
Probabilistic engineering design enhances safety and reduces costs by incorporating risk assessment directly into the design process. In this paper, we assess the format of the quantitative metrics for the vehicle which will replace the Space Shuttle, the Ares I rocket. Specifically, we address the metrics for in-flight measurement error in the vector position of the motor nozzle, dictated by limits on guidance, navigation, and control systems. Analyses include the propagation of error from measured to derived parameters, the time-series of dwell points for the duty cycle during static tests, and commanded versus achieved yaw angle during tests. Based on these analyses, we recommend a probabilistic template for specifying the maximum error in angular displacement and radial offset for the nozzle-position vector. Criteria for evaluating individual tests and risky decisions also are developed.
Statics learning from engineering examples
Emri, Igor
2016-01-01
This textbook introduces and explains the basic concepts on which statics is based utilizing real engineering examples. The authors emphasize the learning process by showing a real problem, analyzing it, simplifying it, and developing a way to solve it. This feature teaches students intuitive thinking in solving real engineering problems using the fundamentals of Newton’s laws. This book also: · Stresses representation of physical reality in ways that allow students to solve problems and obtain meaningful results · Emphasizes identification of important features of the structure that should be included in a model and which features may be omitted · Facilitates students' understanding and mastery of the "flow of thinking" practiced by professional engineers.
Dielectric properties of SPC/E and TIP4P under the static electric field and microwave field
Li, Di; Jia, Guo-zhu
2016-05-01
Nonequilibrium molecular dynamics simulations of the SPC/E and TIP4P models have been performed both in the absence and presence of the static electric field (0-3×109 V/m) and the microwave field (2.45 G, 0-3×109 V/m). The radial distribution function, dielectric constant, polarizability, dielectric relaxation time, hydrogen bonding and diffusion coefficient were investigated. Significant alteration in the static electric field has effect on the tetrahedral structure of water; the interaction between microwave and water depends on the hydrogen bonding. The 3×107 V/m is threshold intensity, as the intensity of the static electric field increases the decline of the dielectric constant becomes more pronounced, and the polarizability obviously increased with the increase of microwave field. And the life of hydrogen bonding is oscillatory under the high static electric field strength.
The condition for dynamic stability
Hof, AL; Gazendam, MGJ; Sinke, WE
The well-known condition for standing stability in static situations is that the vertical projection of the centre of mass (CoM) should be within the base of support (BoS). On the basis of a simple inverted pendulum model, an extension of this rule is proposed for dynamical situations: the position
The condition for dynamic stability
Hof, AL; Gazendam, MGJ; Sinke, WE
2005-01-01
The well-known condition for standing stability in static situations is that the vertical projection of the centre of mass (CoM) should be within the base of support (BoS). On the basis of a simple inverted pendulum model, an extension of this rule is proposed for dynamical situations: the position
赵国鹏; 韩民晓; 刘进军
2012-01-01
Based on the small-signal dynamic model of the indirect current control, a design method of the interface inductor and the DC side capacitor of static synchronous compensator (STATCOM) is proposed. The design method bases on the system stability. This paper presents the models of two types of indirect current control (phase-shift control, phase and amplitude control). In the phase-shift control, the design relationship of the interface inductor and the DC side capacitor is obtained by using the pole-zero map. In the phase and amplitude control, an analysis of the influences of parameters on the current control loop and the voltage control loop is obtained by using the transfer functions and the bode diagrams. The parameters which have a small influence on the system stability are ignored. The equation of the phase margin is simplified. Then, this paper proposes the design methods of the interface inductor and the DC side capacitor. Finally, simulation and experimental results verify the above dynamic model and the design methods.%基于间接电流控制方法的小信号动态模型，提出一种应用相位裕量设计静止无功发生器（STATCOM）连接电抗器和直流侧电容参数的方法。本文分别建立两种间接电流控制方法（相位控制方法，相位和幅值控制方法）的小信号动态模型，在相位控制方法中利用零极点分布特征得出连接电抗器和直流侧电容的设计关系，在相位和幅值控制方法中，利用传递函数和基于伯德图的频域分析方法定性分析了系统各参数对电流环和电压环稳定性的影响，在此基础上忽略对稳定性影响小的参数，简化包含系统各参数的相位裕量表达式，给出基于相位裕量的连接电抗器和直流侧电容的设计方法。最后，仿真和实验表明了动态模型和参数设计方法的正确性。
Relaxation of liquid bridge after droplets coalescence
Jiangen Zheng
2016-11-01
Full Text Available We investigate the relaxation of liquid bridge after the coalescence of two sessile droplets resting on an organic glass substrate both experimentally and theoretically. The liquid bridge is found to relax to its equilibrium shape via two distinct approaches: damped oscillation relaxation and underdamped relaxation. When the viscosity is low, damped oscillation shows up, in this approach, the liquid bridge undergoes a damped oscillation process until it reaches its stable shape. However, if the viscous effects become significant, underdamped relaxation occurs. In this case, the liquid bridge relaxes to its equilibrium state in a non-periodic decay mode. In depth analysis indicates that the damping rate and oscillation period of damped oscillation are related to an inertial-capillary time scale τc. These experimental results are also testified by our numerical simulations with COMSOL Multiphysics.
Cross relaxation in nitroxide spin labels
Marsh, Derek
2016-11-01
Cross relaxation, and mI -dependence of the intrinsic electron spin-lattice relaxation rate We , are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of 14N- and 15N-nitroxide spin labels. Both prove important in spin-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We , the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate We is mI -dependent.
Stretched exponential relaxation of piezovoltages in wet bovine bone.
Xu, Lianyun; Hou, Zhende; Fu, Donghui; Qin, Qing-Hua; Wang, Yihan
2015-01-01
It is important to determine the amplitude and variation characteristics of piezovoltage in wet bone, which can, in turn, be taken as a basis for studying whether electrical signals induced by external forces can affect the growth of bone cells. This work measured the characteristics of piezoelectric effects under dynamic and static loading. The results show that the variations of piezovoltage in wet bone in both loading and load holding periods follow a stretched exponential relaxation law, and the relaxation time constants of the piezovoltages are much larger than those of dry bone. This finding means that the active time of piezovoltage in wet bone is much longer than that of dry bone. Regardless of the loading and load holding processes, continuously increasing deformation in wet bone caused piezoelectric charges to be continuously induced and increased the dielectric constant of wet bone along with the deformation process. In general, compared with piezovoltage in dry bone, that in wet bone had lower amplitude and could exist for a longer duration. It can be inferred, therefore, that piezoelectricity might create coupling with the streaming potential in bone by changing the thickness of the double electrode layer. Copyright © 2014 Elsevier Ltd. All rights reserved.
Utilizing RELAX NG Schemas in XML Editors
Schmied, Martin
2008-01-01
This thesis explores the possibilities of utilizing RELAX NG schemata in the process of editing XML documents. The ultimate goal of this thesis is to prototype a system supporting user while editing XML document with bound RELAX NG schema inside the Eclipse IDE. Such a system comprises two major components -- an integration of RELAX NG validator and an autocompletion engine. Design of the autocompletion engine represents the main contribution of this thesis, because similar systems are almost...
Temperature relaxation in dense plasma mixtures
Faussurier, Gérald; Blancard, Christophe
2016-09-01
We present a model to calculate temperature-relaxation rates in dense plasma mixtures. The electron-ion relaxation rates are calculated using an average-atom model and the ion-ion relaxation rates by the Landau-Spitzer approach. This method allows the study of the temperature relaxation in many-temperature electron-ion and ion-ion systems such as those encountered in inertial confinement fusion simulations. It is of interest for general nonequilibrium thermodynamics dealing with energy flows between various systems and should find broad use in present high energy density experiments.
Baryogenesis via Elementary Goldstone Higgs Relaxation
Gertov, Helene; Pearce, Lauren; Yang, Louis
2016-01-01
We extend the relaxation mechanism to the Elementary Goldstone Higgs frame- work. Besides studying the allowed parameter space of the theory we add the minimal ingredients needed for the framework to be phenomenologically viable. The very nature of the extended Higgs sector allows to consider very flat scalar potential directions along which the relaxation mechanism can be implemented. This fact translates into wider regions of applicability of the relaxation mechanism when compared to the Standard Model Higgs case. Our results show that, if the electroweak scale is not fundamental but radiatively generated, it is possible to generate the observed matter-antimatter asymmetry via the relaxation mechanism.
Dielectric relaxation studies in polyvinyl butyral
Mehendru, P. C.; Kumar, Naresh; Arora, V. P.; Gupta, N. P.
1982-10-01
Dielectric measurements have been made in thick films (˜100 μm) of polyvinyl butyral (PVB) having degree of polymerization n=1600, in the frequency range 100 Hz-100 KHz and temperature range 300-373 K. The results indicated that PVB was in the amorphous phase and observed dielectric dispersion has been assigned as the β-relaxation process. The β relaxation is of Debye type with symmetrical distribution of relaxation times. The dielectric relaxation strength Δɛ and the distribution parameters β¯ increase with temperature. The results can be qualitatively explained by assuming the hindered rotation of the side groups involving hydroxyl/acetate groups.
Relaxation and Visualization Strategies for Story Telling
冯灵林
2012-01-01
The importance of training students to tell or retell story is self - evident for mastering English language. The following activity introduces relaxation and visualization strategies for story telling.
Tsen CL
2015-04-01
Full Text Available Chui-Lien Tsen,1 Yu-Harn Horng,1 Shwu-Jiuan Sheu1,2 1Department of Ophthalmology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; 2School of Medicine, National Yang-Ming University, Taipei, Taiwan Background: We describe the anatomical and functional outcomes of eyes that underwent a modified technique of relaxing retinotomy, dashed line relaxing retinotomy, in the management of retinal detachment with anterior proliferative vitreoretinopathy.Methods: We retrospectively reviewed 54 consecutive eyes in 52 patients who received pars plana vitrectomy with relaxing retinotomy during retinal detachment repair. Perfluorocarbon liquid (PFCL was used as a standard procedure to stabilize the retina during retinotomy to prevent slippage or inversion of the posterior flap. If PFCL was not available due to economic reasons, dashed line relaxing retinotomy was performed instead. Best-corrected visual acuity, slit-lamp biomicroscopy, intraocular pressure measurement, lens status, and fundus examination were analyzed. We excluded patients who were followed up <4 months.Results: Regarding anatomical success rates and visual outcomes, we found no significant differences between patients treated with intraoperative PFCL and those treated with dashed line relaxing retinotomy without PFCL.Conclusion: Compared to the simple and efficient PFCL-assisted relaxing retinotomy, dashed relaxing retinotomy is not the first choice when PFCL is available. Based on our results, this modified technique may offer an alternative in patients with anterior proliferative vitreoretinopathy for whom PFCL is not available. Keywords: perfluorocarbon liquid, PFCL
G. Chen
2011-08-01
Full Text Available The purpose of this paper is to present new concepts for designing fully-compliant statically-balanced mechanisms without prestressing assembly. A statically-balanced compliant mechanism can ideally provide zero stiffness and energy free motion like a traditional rigid-body mechanism. These characteristics are important in design of compliant mechanisms where low actuation force, accurate force transmission or high-fidelity force feedback are primary concerns. Typically, static balancing of compliant mechanisms has been achieved by means of prestressing assembly. However, this can often lead to creep and stress relaxation arising in the flexible members. In this paper two concepts are presented which eliminate the need for prestressing assembly of compliant mechanisms: (1 a weight compensator which employs a constant-force compliant mechanism, (2 a near-zero-stiffness mechanism which combines two multistable mechanisms. In addition to the advantages provided by statically-balanced compliant mechanisms, two other notable features of these statically-balanced mechanisms are their ability to be monolithically fabricated and to return to their as-fabricated position without any disassembly when not in use.
Quasi-Static Analysis of LaRC THUNDER Actuators
Campbell, Joel F.
2007-01-01
An analytic approach is developed to predict the shape and displacement with voltage in the quasi-static limit of LaRC Thunder Actuators. The problem is treated with classical lamination theory and Von Karman non-linear analysis. In the case of classical lamination theory exact analytic solutions are found. It is shown that classical lamination theory is insufficient to describe the physical situation for large actuators but is sufficient for very small actuators. Numerical results are presented for the non-linear analysis and compared with experimental measurements. Snap-through behavior, bifurcation, and stability are presented and discussed.
Statics of levitated vehicle model with hybrid magnets
Desheng LI; Zhiyuan LU; Tianwu DONG
2009-01-01
By studying the special characteristics of permanent and electronic magnets, a levitated vehicle model with hybrid magnets is established. The mathematical model of the vehicle is built based on its dynamics equation by studying its machine structure and working principle. Based on the model, the basic characteristics and the effect between the excluding forces from permanent magnets in three different spatial directions are analyzed, statics characteristics of the interference forces in three different spatial directions are studied, and self-adjusting equilibrium characteristics and stabilization are analyzed. Based on the structure above, the vehicle can levitate steadily by control system adjustment.
Gyroscopic stabilization of non-conservative systems
Kirillov, Oleg N. [Dynamics Group, Department of Mechanical Engineering, Technical University of Darmstadt, Hochschulstr. 1, 64289 Darmstadt (Germany) and Institute of Mechanics, Moscow State Lomonosov University, Michurinskii pr. 1, 119192 Moscow (Russian Federation)]. E-mail: kirillov@dyn.tu-darmstadt.de
2006-11-20
Gyroscopic stabilization of a linear conservative system, which is statically unstable, can be either improved or destroyed by weak damping and circulatory forces. This is governed by Whitney umbrella singularity of the boundary of the asymptotic stability domain of the perturbed system.
Static and non-static black holes with the Liouville mode
Moskalets, T. M.; Nurmagambetov, A. J.
2017-03-01
We present a new class of static and non-static quasi-spherical black hole solutions in four-dimensional Minkowski and Anti-de Sitter spaces and briefly discuss its employing in the Gauge/Gravity duality.
Xingwen Zhu
2015-01-01
Full Text Available Smoothing analysis process of distributive red-black Jacobi relaxation in multigrid method for solving 2D Stokes flow is mainly investigated on the nonstaggered grid by using local Fourier analysis (LFA. For multigrid relaxation, the nonstaggered discretizing scheme of Stokes flow is generally stabilized by adding an artificial pressure term. Therefore, an important problem is how to determine the zone of parameter in adding artificial pressure term in order to make stabilization of the algorithm for multigrid relaxation. To end that, a distributive red-black Jacobi relaxation technique for the 2D Stokes flow is established. According to the 2h-harmonics invariant subspaces in LFA, the Fourier representation of the distributive red-black Jacobi relaxation for discretizing Stokes flow is given by the form of square matrix, whose eigenvalues are meanwhile analytically computed. Based on optimal one-stage relaxation, a mathematical relation of the parameter in artificial pressure term between the optimal relaxation parameter and related smoothing factor is well yielded. The analysis results show that the numerical schemes for solving 2D Stokes flow by multigrid method on the distributive red-black Jacobi relaxation have a specified convergence parameter zone of the added artificial pressure term.
Martínez-Morales, José L.
The master equations in the Euclidean Schwarzschild-Tangherlini space-time of a small static perturbation are studied. For each harmonic mode on the sphere there are two solutions that behave differently at infinity. One solution goes like the power 2-l-n of the radial variable, the other solution goes like the power l. These solutions occur in power series. The second main statement of the paper is that any eigentensor of the Lichnerowicz operator in a Euclidean Schwarzschild space-time with an eigenvalue different from zero is essentially singular at infinity. Possible applications of the stability of instantons are discussed. We present the analysis of a small static perturbation of the Euclidean Schwarzschild-Tangherlini metric tensor. The higher order perturbations will appear later. We determine independently the static perturbations of the Schwarzschild quantum black hole in dimension 1+n≥4, where the system of equations is reduced to master equations — ordinary differential equations. The solutions are hypergeometric functions which in some cases can be reduced to polynomials. In the same Schwarzschild background, we analyze static perturbations of the scalar mode and show that there does not exist any static perturbation that is regular everywhere outside the event horizon and is well-behaved at the spatial infinity. This confirms the uniqueness of the spherically symmetric static empty quantum black hole, within the perturbation framework. Our strategy for treating the stability problem is also applicable to other symmetric quantum black holes with a nonzero cosmological constant.
Automatically Discovering Relaxed Lyapunov Functions for Polynomial Dynamical Systems
Liu, Jiang; Zhao, Hengjun
2011-01-01
The notion of Lyapunov function plays a key role in design and verification of dynamical systems, as well as hybrid and cyber-physical systems. In this paper, to analyze the asymptotic stability of a dynamical system, we generalize standard Lyapunov functions to relaxed Lyapunov functions (RLFs), by considering higher order Lie derivatives of certain functions along the system's vector field. Furthermore, we present a complete method to automatically discovering polynomial RLFs for polynomial dynamical systems (PDSs). Our method is complete in the sense that it is able to discover all polynomial RLFs by enumerating all polynomial templates for any PDS.
A case of endophthalmitis associated with limbal relaxing incision
Aravind Haripriya
2012-01-01
Full Text Available Limbal relaxing incisions (LRIs are considered a relatively safe procedure with rapid stabilization and absence of infectious complications. Do we need to readdress this last impression? We report a case of nocardia endophthalmitis associated with an exudate at the site of an LRI in a patient who underwent routine cataract surgery. This case, to the best of our knowledge, is the first report of its kind, stressing the need for a cautious approach to the adoption of this method of astigmatic correction.
Nuclear relaxation via paramagnetic impurities
Dzheparov, F S; Jacquinot, J F
2002-01-01
First part of the work contains a calculation of the kinetics of nuclear relaxation via paramagnetic impurities for systems with arbitrary (including fractal) space dimension d basing on ideas, which run current for 3d objects now. A new mean-field-type theory is constructed in the second part of the work. It reproduces all results of the first part for integer d and gives a possibility to describe the process for longer time, when a crossover to Balagurov-Waks asymptotics starts to develop. Solutions of the equations of the new theory are constructed for integer d. To obtain the solutions a method of calculation of the low-energy and long-wave asymptotics for T matrix of potential scattering out of the mass shell for singular repulsive potentials is developed
Relaxing Chosen-Ciphertext Security
Canetti, Ran; Krawczyk, Hugo; Nielsen, Jesper Buus
2003-01-01
Security against adaptive chosen ciphertext attacks (or, CCA security) has been accepted as the standard requirement from encryption schemes that need to withstand active attacks. In particular, it is regarded as the appropriate security notion for encryption schemes used as components within...... general protocols and applications. Indeed, CCA security was shown to suffice in a large variety of contexts. However, CCA security often appears to be somewhat too strong: there exist encryption schemes (some of which come up naturally in practice) that are not CCA secure, but seem sufficiently secure...... “for most practical purposes.” We propose a relaxed variant of CCA security, called Replayable CCA (RCCA) security. RCCA security accepts as secure the non-CCA (yet arguably secure) schemes mentioned above; furthermore, it suffices for most existing applications of CCA security. We provide three...
STATIC VERSUS PNF STRETCHING IN HAMSTRING FLEXIBILITY-A COMPARATIVE STUDY
Venkata Naga Prahalada Karnati
2015-06-01
Full Text Available Background: Stretching used as a technique for injury prevention in the clinical settings, the study aimed to determine the early findings of hamstring tightness with both groups in the population, now a days the sedentary activities like prolonged sitting might cause hamstring tightness and change in path kinematics of gait intern lead to postural defects and back pain, understanding of the stretching helps clinician to make decisions for rehabilitation. Methods: Across-sectional study, counterbalanced with repeated-measures , one group with static stretch – (double hamstring stretch and hurdlers stretch for 3 times,30seconds subsequently in another group PNF contract relax(agonist contraction technique for 10 seconds position and 10 seconds stretch repeated for 3 times. Results: The results from data and statistical analysis by using t-test, SPSS obtained by using goniometer are tabulated in terms of mean, standard deviation and p-value in both groups. In experimental group flexion with PNF showed improvement 9.27±1.91(right side, 9.53±2.42(left side and static stretching showed 7.8±2.91(right side, 7.47±1.96(left side this proves that PNF has consistent improvement than static stretching. Conclusions: Static and proprioceptive neuromuscular facilitation stretching both have produced greater improvement but compared with PNF contract relax(agonist stretching showed significant change in hamstring flexibility compared with control group . The effect sizes, however corresponding to these stretching-induced changes were small, which suggests the need for practitioners to consider a risk-to-benefit ratio when incorporating static or proprioceptive neuromuscular facilitation stretching.
Model Checking as Static Analysis: Revisited
Zhang, Fuyuan; Nielson, Flemming; Nielson, Hanne Riis
2012-01-01
We show that the model checking problem of the μ-calculus can be viewed as an instance of static analysis. We propose Succinct Fixed Point Logic (SFP) within our logical approach to static analysis as an extension of Alternation-free Least Fixed Logic (ALFP). We generalize the notion...
Static domain wall in braneworld gravity
Abdalla, M.C.B.; Carlesso, P.F. [UNESP, Universidade Estadual Paulista, Instituto de Fisica Teiorica, Rua Dr. Bento Teobaldo Ferraz 271, Bloco II, Barra-Funda, Caixa Postal 70532-2, Sao Paulo, SP (Brazil); Hoff da Silva, J.M. [UNESP, Universidade Estadual Paulista, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil)
2014-01-15
In this paper we consider a static domain wall inside a 3-brane. Different from the standard achievement obtained in General Relativity, the analysis performed here gives a consistency condition for the existence of static domain walls in a braneworld gravitational scenario. Also the behavior of the domain wall's gravitational field in the newtonian limit is shown. (orig.)
Static Complexity Analysis of Higher Order Programs
Avery, James Emil; Kristiansen, Lars; Moyen, Jean-Yves
2009-01-01
The overall goal of the research presented in this paper is to find^M automatic methods for static complexity analysis of higher order^M programs.......The overall goal of the research presented in this paper is to find^M automatic methods for static complexity analysis of higher order^M programs....
Static balance and developmental coordination disorder
Geuze, RH
2003-01-01
The development of static balance is a basic characteristic of normal motor development. Most of the developmental motor tests include a measure of static balance. Children with a developmental coordination disorder (DCD) often fail this item. Twenty-four children at risk for DCD with balance proble
Comparing Techniques for Certified Static Analysis
Cachera, David; Pichardie, David
2009-01-01
A certified static analysis is an analysis whose semantic validity has been formally proved correct with a proof assistant. The recent increasing interest in using proof assistants for mechanizing programming language metatheory has given rise to several approaches for certification of static analysis. We propose a panorama of these techniques and compare their respective strengths and weaknesses.
Nuclear magnetic relaxation by the dipolar EMOR mechanism: Three-spin systems
Chang, Zhiwei; Halle, Bertil
2016-07-01
In aqueous systems with immobilized macromolecules, including biological tissue, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have developed a non-perturbative theory that can describe relaxation by the dipolar EMOR mechanism over the full range of exchange rates, dipole couplings, and Larmor frequencies. Here, we implement the general dipolar EMOR theory for a macromolecule-bound three-spin system, where one, two, or all three spins exchange with the bulk solution phase. In contrast to the previously studied two-spin system with a single dipole coupling, there are now three dipole couplings, so relaxation is affected by distinct correlations as well as by self-correlations. Moreover, relaxation can now couple the magnetizations with three-spin modes and, in the presence of a static dipole coupling, with two-spin modes. As a result of this complexity, three secondary dispersion steps with different physical origins can appear in the longitudinal relaxation dispersion profile, in addition to the primary dispersion step at the Larmor frequency matching the exchange rate. Furthermore, and in contrast to the two-spin system, longitudinal relaxation can be significantly affected by chemical shifts and by the odd-valued ("imaginary") part of the spectral density function. We anticipate that the detailed studies of two-spin and three-spin systems that have now been completed will provide the foundation for developing an approximate multi-spin dipolar EMOR theory sufficiently accurate and computationally efficient to allow quantitative molecular-level interpretation of frequency-dependent water-proton longitudinal relaxation data from biophysical model systems and soft biological tissue.
Structural and magnetic relaxations of mechanically alloyed Fe-Mo
Jiraskova, Y.; Bursik, J.; Turek, I.; Cizek, J.; Prochazka, I.
2014-10-01
The Fe-Mo sample mechanically alloyed for 250 h under air atmosphere was exposed to a series of isothermal and isochronal treatments with the aim to follow changes in the structure and magnetic properties regarding relaxations of strains and defects and stability of chemical composition. For this purpose x-ray diffraction, positron annihilation, scanning and transmission electron microscopy, and Mössbauer spectrometry were applied and supplemented by magnetic measurements. The temperatures for the magnetic studies were selected from the thermomagnetic curve of the as-prepared sample. The time interval of isothermal treatments was chosen from 0-300 min. The Mo content in the bcc-Fe(Mo) phase has substantially exceeded the equilibrium solubility limit but it has been found to decrease under the thermal treatment which was reflected by decreasing lattice parameters. The small crystallite size of approximately 10 nm in the initial state starts to grow only after a certain amount of strains induced by severe deformation, due to mechanical alloying being released. This was also reflected in the magnetic parameters. From their time dependences at selected temperatures the characteristic relaxation times were obtained and used for a calculation of the activation enthalpy of relaxation processes.
Relaxation path of metastable nanoclusters in oxide dispersion strengthened materials
Ribis, J.; Thual, M. A.; Guilbert, T.; de Carlan, Y.; Legris, A.
2017-02-01
ODS steels are a promising class of structural materials for sodium cooled fast reactor application. The ultra-high density of the strengthening nanoclusters dispersed within the ferritic matrix is responsible of the excellent creep properties of the alloy. Fine characterization of the nanoclusters has been conducted on a Fe-14Cr-0.3Ti-0.3Y2O3 ODS material using High Resolution and Energy Filtered Transmission Electron Microscopy. The nanoclusters exhibit a cubic symmetry possibly identified as f.c.c and display a non-equilibrium YTiCrO chemical composition thought to be stabilized by a vacancy supersaturation. These nanoclusters undergo relaxation towards the Y2Ti2O7-like state as they grow. A Cr shell is observed around the relaxed nano-oxides, this size-dependent shell may form after the release of Cr by the particles. The relaxation energy barrier appears to be higher for the smaller particles probably owing to a volume/surface ratio effect in reason to the full coherency of the nanoclusters.
Superparamagnetic relaxation of weakly interacting particles
Mørup, Steen; Tronc, Elisabeth
1994-01-01
The influence of particle interactions on the superparamagnetic relaxation time has been studied by Mossbauer spectroscopy in samples of maghemite (gamma-Fe2O3) particles with different particle sizes and particle separations. It is found that the relaxation time decreases with decreasing particl...
Postextrasystolic relaxation in the dog heart
Kuijer, P.J.P.; Heethaar, R.M.; Herbschleb, J.N.; Zimmerman, A.N.E.; Meijler, F.L.
1978-01-01
Left ventricular relaxation was studied in 8 dogs using parameters derived from the left ventricular pressure: the fastest pressure fall and the time constant of pressure decline. Effects of extrasystolic rhythm interventions were examined on the relaxation parameters of the post-relative to the pre
Superparamagnetic relaxation in alpha-Fe particles
Bødker, Franz; Mørup, Steen; Pedersen, Michael Stanley;
1998-01-01
The superparamagnetic relaxation time of carbon-supported alpha-Fe particles with an average size of 3.0 Mm has been studied over a large temperature range by the use of Mossbauer spectroscopy combined with AC and DC magnetization measurements. It is found that the relaxation time varies with tem...
Cross relaxation in nitroxide spin labels
Marsh, Derek
2016-01-01
-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We, the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from...
Magnetization Transfer Induced Biexponential Longitudinal Relaxation
Prantner, Andrew M.; Bretthorst, G. Larry; Neil, Jeffrey J.; Garbow, Joel R.; Ackerman, Joseph J.H.
2009-01-01
Longitudinal relaxation of brain water 1H magnetization in mammalian brain in vivo is typically analyzed on a per voxel basis using a monoexponential model, thereby assigning a single relaxation time constant to all 1H magnetization within a given voxel. This approach was tested by obtaining inversion recovery data from grey matter of rats at 64 exponentially-spaced recovery times. Using Bayesian probability for model selection, brain water data were best represented by a biexponential function characterized by fast and slow relaxation components. At 4.7 T, the amplitude fraction of the rapidly relaxing component is 3.4 ± 0.7 % with a rate constant of 44 ± 12 s-1 (mean ± SD; 174 voxels from 4 rats). The rate constant of the slow relaxing component is 0.66 ± 0.04 s-1. At 11.7 T, the corresponding values are 6.9 ± 0.9 %, 19 ± 5 s-1, and 0.48 ± 0.02 s-1 (151 voxels from 4 rats). Several putative mechanisms for biexponential relaxation behavior were evaluated, and magnetization transfer between bulk water protons and non-aqueous protons was determined to be the source of biexponential longitudinal relaxation. MR methods requiring accurate quantification of longitudinal relaxation may need to take this effect explicitly into account. PMID:18759367
Windowing Waveform Relaxation of Initial Value Problems
Yao-lin Jiang
2006-01-01
We present a windowing technique of waveform relaxation for dynamic systems. An effective estimation on window length is derived by an iterative error expression provided here. Relaxation processes can be speeded up if one takes the windowing technique in advance. Numerical experiments are given to further illustrate the theoretical analysis.
Geerdink, J.B.W.; Hoekstra, A.G.
2009-01-01
We compare the Lattice BGK, the Multiple Relaxation Times and the Entropic Lattice Boltzmann Methods for time harmonic flows. We measure the stability, speed and accuracy of the three models for Reynolds and Womersley numbers that are representative for human arteries. The Lattice BGK shows
Dielectric and specific heat relaxations in vapor deposited glycerol
Kasina, A., E-mail: angeline.kasina@fys.kuleuven.be, E-mail: wubbenhorst@fys.kuleuven.be; Putzeys, T.; Wübbenhorst, M., E-mail: angeline.kasina@fys.kuleuven.be, E-mail: wubbenhorst@fys.kuleuven.be [Department of Physics and Astronomy, Soft Matter and Biophysics Section, KU Leuven, Leuven (Belgium)
2015-12-28
Recently [S. Capponi, S. Napolitano, and M. Wübbenhorst, Nat. Commun. 3, 1233 (2012)], vapor deposited glasses of glycerol have been found to recover their super-cooled liquid state via a metastable, ordered liquid (MROL) state characterized by a tremendously enhanced dielectric strength along with a slow-down of the relaxation rate of the structural relaxation. To study the calorimetric signature of this phenomenon, we have implemented a chip-based, differential AC calorimeter in an organic molecular beam deposition setup, which allows the simultaneous measurement of dielectric relaxations via interdigitated comb electrodes and specific heat relaxation spectra during deposition and as function of the temperature. Heating of the as-deposited glass just above the bulk T{sub g} and subsequent cooling/reheating revealed a step-wise increase in c{sub p} by in total 9%, indicating unambiguously that glycerol, through slow vapour deposition, forms a thermodynamically stable glass, which has a specific heat as low as that of crystalline glycerol. Moreover, these glasses were found to show excellent kinetic stability as well as evidenced by both a high onset-temperature and quasi-isothermal recovery measurements at −75 °C. The second goal of the study was to elucidate the impact of the MROL state on the specific heat and its relaxation to the super-cooled state. Conversion of “MROL glycerol” to its “normal” (ordinary liquid, OL) state revealed a second, small (∼2%) increase of the glassy c{sub p}, a little gain (<10%) in the relaxed specific heat, and no signs of deviations of τ{sub cal} from that of normal “bulk” glycerol. These findings altogether suggest that the MROL state in glycerol comprises largely bulk-type glycerol that coexist with a minor volume fraction (<10%) of PVD-induced structural anomalies with a crystal-like calorimetric signature. Based on the new calorimetric findings, we have proposed a new physical picture that assumes the
Static vortices in long Josephson junctions of exponentially varying width
Semerdjieva, E. G.; Boyadjiev, T. L.; Shukrinov, Yu. M.
2004-06-01
A numerical simulation is carried out for static vortices in a long Josephson junction with an exponentially varying width. At specified values of the parameters the corresponding boundary-value problem admits more than one solution. Each solution (distribution of the magnetic flux in the junction) is associated to a Sturm-Liouville problem, the smallest eigenvalue of which can be used, in a first approximation, to assess the stability of the vortex against relatively small spatiotemporal perturbations. The change in width of the junction leads to a renormalization of the magnetic flux in comparison with the case of a linear one-dimensional model. The influence of the model parameters on the stability of the states of the magnetic flux is investigated in detail, particularly that of the shape parameter. The critical curve of the junction is constructed from pieces of the critical curves for the different magnetic flux distributions having the highest critical currents for the given magnetic field.
Stress Relaxation in Entangled Polymer Melts
Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf
2010-01-01
We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements and into the t......We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements...... and into the terminal relaxation regime for Z=10. Using the known (Rouse) mobility of unentangled chains and the melt entanglement length determined via the primitive path analysis of the microscopic topological state of our systems, we have performed parameter-free tests of several different tube models. We find...
Stress and Relaxation in Relation to Personality
Harish Kumar Sharma
2011-09-01
Full Text Available Relaxation plays a significant role in facing stress. The aim of the present study is to see whether personality patterns determine an individual’s ability to relax. As a reaction to stress, coping is the best way to handle stress, which requires rational and conscious thinking. Does this ability to relax anyway facilitate coping reactions? A study was conducted on 100 college students. Results revealed that extraverts relax easily than introverts. In addition, if intelligence level is average or above average, relaxation does play a role in facilitating coping reactions. It suggests that in designing techniques of stress management, the personality and intelligence level must be taken into consideration to make techniques effective.
颗粒介质弹性的弛豫∗%Relaxation of granular elasticity
孙其诚; 刘传奇; 周公旦
2015-01-01
In granular materials, particles constitute a complex force chains network through contact with each other, and elastic energies are stored due to deformation of particles. This elastic behavior is macroscopic manifestation of inter-particle contacts. Elastic constants or elastic moduli are of fundamental importance for granular material. Due to the hyper-static property of inter-particle forces, the bulk elastic energy stored in the contacts is metastable in the viewpoint of energy landscape, i.e. a high energy state may approaches a more stable state (i.e. relatively lower state) under the action of external perturbations or internal stress, resulting in the elastic modulus reduction. This process is the so-called elasticity relaxation. It may be more obvious in granular materials. The time-dependent behavior of granular materials, especially the creep, has been studied in experiments and numerical simulations, while the stress relaxation has few reported investigations. Stress relaxation is defined as the process in vohich the initial strain is maintained and the stress decays with the time. From energetic viewpoint, elastic energy is stored in the deformation of particles. The granular system is in a metastable state when confined in a state easy to break the balance. Generally speaking, the shape and grading of particles, volume fraction, surface friction properties, initial structure features, ageing time, loading strain rate will all play important roles in stress relaxation. In this work, it is believed that the elastic relaxation is the only mechanism to describe the stress relaxation, and the mechanism of it is analyzed from the viewpoint of the potential energy surface. Stress relaxation is calculated by means of the so-called two-granular temperature theory (TGT) we developed previously (Sun Q et al. 2015 Sci. Rep. 5 9652). The stress decays fast at the beginning, then decreases gradually slowly to a stable value. The logarithmic fit is first proposed
Magnetic Resonance Fingerprinting with short relaxation intervals.
Amthor, Thomas; Doneva, Mariya; Koken, Peter; Sommer, Karsten; Meineke, Jakob; Börnert, Peter
2017-09-01
The aim of this study was to investigate a technique for improving the performance of Magnetic Resonance Fingerprinting (MRF) in repetitive sampling schemes, in particular for 3D MRF acquisition, by shortening relaxation intervals between MRF pulse train repetitions. A calculation method for MRF dictionaries adapted to short relaxation intervals and non-relaxed initial spin states is presented, based on the concept of stationary fingerprints. The method is applicable to many different k-space sampling schemes in 2D and 3D. For accuracy analysis, T1 and T2 values of a phantom are determined by single-slice Cartesian MRF for different relaxation intervals and are compared with quantitative reference measurements. The relevance of slice profile effects is also investigated in this case. To further illustrate the capabilities of the method, an application to in-vivo spiral 3D MRF measurements is demonstrated. The proposed computation method enables accurate parameter estimation even for the shortest relaxation intervals, as investigated for different sampling patterns in 2D and 3D. In 2D Cartesian measurements, we achieved a scan acceleration of more than a factor of two, while maintaining acceptable accuracy: The largest T1 values of a sample set deviated from their reference values by 0.3% (longest relaxation interval) and 2.4% (shortest relaxation interval). The largest T2 values showed systematic deviations of up to 10% for all relaxation intervals, which is discussed. The influence of slice profile effects for multislice acquisition is shown to become increasingly relevant for short relaxation intervals. In 3D spiral measurements, a scan time reduction of 36% was achieved, maintaining the quality of in-vivo T1 and T2 maps. Reducing the relaxation interval between MRF sequence repetitions using stationary fingerprint dictionaries is a feasible method to improve the scan efficiency of MRF sequences. The method enables fast implementations of 3D spatially resolved
Rood, A.; Hannink, G.; Lenting, A.; Groenen, K.; Koeter, S.; Verdonschot, N.J.; Kampen, A. van
2015-01-01
BACKGROUND: Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue fixa
Rood, A.; Hannink, G.; Lenting, A.; Groenen, K.; Koëter, S.; Verdonschot, N.J.J.; Kampen, van A.
2015-01-01
Background: Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue fixa
Barrientos, Eva; Pelayo, Fernández; Tanaka, Eiji; Lamela-Rey, María Jesús; Fernández-Canteli, Alfonso
2016-04-01
In this study, the dynamic and static compressive properties of the whole porcine temporomandibular joint (TMJ) disc were investigated. The aim of the study was to develop a new simple method for the evaluation of joint viscoelasticity, enabling examination of the load-bearing capacity and joint flexibility of the entire disc. For the experiments, a novel testing fixture that reproduces the condylar and fossa surfaces of the TMJ was developed to replicate TMJ disc geometry. Ten porcine discs were used in the experiments. Each disc was dissected from the TMJ and sinusoidal compressive strain was applied to obtain the storage and loss moduli. Static strain control tests were carried out to obtain the relaxation modulus. The result of static and dynamic tests indicated that the whole disc presented viscoelastic behavior under compression. Storage and loss moduli increased with frequency and the relaxation modulus decreased over time. The loss tangent showed less frequency dependence, with values ranging from 0.2 to 0.3, suggesting that the viscous properties of the disc cannot be neglected. These results provide a better understanding of whole disc mechanical compression behavior under realistic TMJ working conditions.
Aftershocks halted by static stress shadows
Toda, Shinji; Stein, Ross S.; Beroza, Gregory C.; Marsan, David
2012-06-01
Earthquakes impart static and dynamic stress changes to the surrounding crust. Sudden fault slip causes small but permanent--static--stress changes, and passing seismic waves cause large, but brief and oscillatory--dynamic--stress changes. Because both static and dynamic stresses can trigger earthquakes within several rupture dimensions of a mainshock, it has proven difficult to disentangle their contributions to the triggering process. However, only dynamic stress can trigger earthquakes far from the source, and only static stress can create stress shadows, where the stress and thus the seismicity rate in the shadow area drops following an earthquake. Here we calculate the stress imparted by the magnitude 6.1 Joshua Tree and nearby magnitude 7.3 Landers earthquakes that occurred in California in April and June 1992, respectively, and measure seismicity through time. We show that, where the aftershock zone of the first earthquake was subjected to a static stress increase from the second, the seismicity rate jumped. In contrast, where the aftershock zone of the first earthquake fell under the stress shadow of the second and static stress dropped, seismicity shut down. The arrest of seismicity implies that static stress is a requisite element of spatial clustering of large earthquakes and should be a constituent of hazard assessment.
Martian Atmospheric Pressure Static Charge Elimination Tool
Johansen, Michael R.
2014-01-01
A Martian pressure static charge elimination tool is currently in development in the Electrostatics and Surface Physics Laboratory (ESPL) at NASA's Kennedy Space Center. In standard Earth atmosphere conditions, static charge can be neutralized from an insulating surface using air ionizers. These air ionizers generate ions through corona breakdown. The Martian atmosphere is 7 Torr of mostly carbon dioxide, which makes it inherently difficult to use similar methods as those used for standard atmosphere static elimination tools. An initial prototype has been developed to show feasibility of static charge elimination at low pressure, using corona discharge. A needle point and thin wire loop are used as the corona generating electrodes. A photo of the test apparatus is shown below. Positive and negative high voltage pulses are sent to the needle point. This creates positive and negative ions that can be used for static charge neutralization. In a preliminary test, a floating metal plate was charged to approximately 600 volts under Martian atmospheric conditions. The static elimination tool was enabled and the voltage on the metal plate dropped rapidly to -100 volts. This test data is displayed below. Optimization is necessary to improve the electrostatic balance of the static elimination tool.
Domain Relaxation in Langmuir Films
Bernoff, Andrew J.; Alexander, James C.; Mann, Elizabeth K.; Mann, J. Adin; Zou, Lu; Wintersmith, Jacob R.
2007-11-01
We report on an experimental, theoretical and computational study of a molecularly thin polymer Langmuir layer domain on the surface of a subfluid. When stretched (by a transient stagnation flow), the Langmuir layer takes the form of a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape relaxes to the circular minimum energy configuration. The tether is never observed to rupture, even when it is more than a hundred times as long as it is thin. We model these experiments as a free boundary problem where motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. We process the digital images of the experiment to extract the domain shape, use one of these shapes as an initial condition for the numerical solution of a boundary-integral model of the underlying hydrodynamics, and compare the subsequent images of the experiment to the numerical simulation. The numerical evolutions verify that our hydrodynamical model can reproduce the observed dynamics. They also allow us to deduce the magnitude of the line tension in the system, often to within 1%.
Supervised Discrete Hashing With Relaxation.
Gui, Jie; Liu, Tongliang; Sun, Zhenan; Tao, Dacheng; Tan, Tieniu
2016-12-29
Data-dependent hashing has recently attracted attention due to being able to support efficient retrieval and storage of high-dimensional data, such as documents, images, and videos. In this paper, we propose a novel learning-based hashing method called ''supervised discrete hashing with relaxation'' (SDHR) based on ''supervised discrete hashing'' (SDH). SDH uses ordinary least squares regression and traditional zero-one matrix encoding of class label information as the regression target (code words), thus fixing the regression target. In SDHR, the regression target is instead optimized. The optimized regression target matrix satisfies a large margin constraint for correct classification of each example. Compared with SDH, which uses the traditional zero-one matrix, SDHR utilizes the learned regression target matrix and, therefore, more accurately measures the classification error of the regression model and is more flexible. As expected, SDHR generally outperforms SDH. Experimental results on two large-scale image data sets (CIFAR-10 and MNIST) and a large-scale and challenging face data set (FRGC) demonstrate the effectiveness and efficiency of SDHR.
Spin relaxation in organic semiconductors
Bobbert, Peter
2011-03-01
Intriguing magnetic field effects in organic semiconductor devices have been reported: anomalous magnetoresistance in organic spin valves and large effects of small magnetic fields on the current and luminescence of organic light-emitting diodes. Influences of isotopic substitution on these effects points at the role of hyperfine coupling. We performed studies of spin relaxation in organic semiconductors based on (i) coherent spin precession of the electron spin in an effective magnetic field consisting of a random hyperfine field and an applied magnetic field and (ii) incoherent hopping of charges. These ingredients are incorporated in a stochastic Liouville equation for the dynamics of the spin density matrix of single charges as well as pairs of charges. For single charges we find a spin diffusion length that depends on the magnetic field, explaining anomalous magnetoresistance in organic spin valves. For pairs of charges we show that the magnetic field influences formation of singlet bipolarons, in the case of like charges, and singlet and triplet excitons, in the case of opposite charges. We can reproduce different line shapes of reported magnetic field effects, including recently found effects at ultra-small fields.
Studies on irradiation stability of polystyrene by NMR
ZHAO Xin; SUN Wan-Fu; XIE Cheng-Xi
2004-01-01
The irradiation stability of polystyrene (PS) was studied by 13C and 1H NMR spectra, Nuclear Overhauser Relaxation (NOE) and 13C NMR spin-lattice relaxation time (T1). The results indicate that 13C and 1H NMR chemical shifts, NOE and T1 were almost invariant with the increase of irradiation dose. This shows that polystyrene is particularly stable within 2.5 kGy doses and the mechanism of its stability is discussed.
Pheromone Static Routing Strategy for Complex Networks
Ling, Xiang; Jiang, Rui; Hu, Mao-Bin
2011-01-01
In this paper, we adopt the concept of pheromone to generate a set of static paths that can reach the performance of global dynamic routing strategy [Phys. Rev. E 81, 016113(2010)]. In the test stage, pheromone is dropped to the nodes by packets forwarded by the global dynamic routing strategy. After that, static paths are generated according to the density of pheromone. The output paths can greatly improve traffic systems' overall capacity on different network structures, including scale-free networks, small-world networks and random graphs. Because the paths are static, the system needs much less computational resource than the global dynamic routing strategy.
Relaxation of a 1-D gravitational system
Valageas, P
2006-01-01
We study the relaxation towards thermodynamical equilibrium of a 1-D gravitational system. This OSC model shows a series of critical energies $E_{cn}$ where new equilibria appear and we focus on the homogeneous ($n=0$), one-peak ($n=\\pm 1$) and two-peak ($n=2$) states. Using numerical simulations we investigate the relaxation to the stable equilibrium $n=\\pm 1$ of this $N-$body system starting from initial conditions defined by equilibria $n=0$ and $n=2$. We find that in a fashion similar to other long-range systems the relaxation involves a fast violent relaxation phase followed by a slow collisional phase as the system goes through a series of quasi-stationary states. Moreover, in cases where this slow second stage leads to a dynamically unstable configuration (two peaks with a high mass ratio) it is followed by a new sequence ``violent relaxation/slow collisional relaxation''. We obtain an analytical estimate of the relaxation time $t_{2\\to \\pm 1}$ through the mean escape time of a particle from its potent...
V.Ts. Gnuni
2016-03-01
Full Text Available The non-conservative stability problem of pressing beam when two support billeting symmetrical on arbitrarily distance from the end is considered. It is show the possibility statical form loss of stability. The critical loads are determined.
Viciosa, M Teresa; Moura Ramos, Joaquim J; Diogo, Hermínio P
2016-12-01
The slow molecular mobility in the amorphous solid state of 3 active pharmaceutical drugs (cimetidine, nizatidine, and famotidine) has been studied using differential scanning calorimetry and the 2 dielectric-related techniques of dielectric relaxation spectroscopy and thermally stimulated depolarization currents. The glass-forming ability, the glass stability, and the tendency for crystallization from the equilibrium melt were investigated by differential scanning calorimetry, which also provided the characterization of the main relaxation of the 3 glass formers. The chemical instability of famotidine at the melting temperature and above it prevented the preparation of the amorphous for dielectric studies. In contrast, for cimetidine and nizatidine, the dielectric study yielded the main kinetic features of the α relaxation and of the secondary relaxations. According to the obtained results, nizatidine displays the higher fragility index of the 3 studied glass-forming drugs. The thermally stimulated depolarization current technique has proved useful to identify the Johari-Goldstein relaxation and to measure τβJG in the amorphous solid state, that is, in a frequency range which is not easily accessible by dielectric relaxation spectroscopy. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.
Le Chatelier's principle with multiple relaxation channels
Gilmore, R.; Levine, R. D.
1986-05-01
Le Chatelier's principle is discussed within the constrained variational approach to thermodynamics. The formulation is general enough to encompass systems not in thermal (or chemical) equilibrium. Particular attention is given to systems with multiple constraints which can be relaxed. The moderation of the initial perturbation increases as additional constraints are removed. This result is studied in particular when the (coupled) relaxation channels have widely different time scales. A series of inequalities is derived which describes the successive moderation as each successive relaxation channel opens up. These inequalities are interpreted within the metric-geometry representation of thermodynamics.
Neural control of muscle relaxation in echinoderms.
Elphick, M R; Melarange, R
2001-03-01
Smooth muscle relaxation in vertebrates is regulated by a variety of neuronal signalling molecules, including neuropeptides and nitric oxide (NO). The physiology of muscle relaxation in echinoderms is of particular interest because these animals are evolutionarily more closely related to the vertebrates than to the majority of invertebrate phyla. However, whilst in vertebrates there is a clear structural and functional distinction between visceral smooth muscle and skeletal striated muscle, this does not apply to echinoderms, in which the majority of muscles, whether associated with the body wall skeleton and its appendages or with visceral organs, are made up of non-striated fibres. The mechanisms by which the nervous system controls muscle relaxation in echinoderms were, until recently, unknown. Using the cardiac stomach of the starfish Asterias rubens as a model, it has been established that the NO-cGMP signalling pathway mediates relaxation. NO also causes relaxation of sea urchin tube feet, and NO may therefore function as a 'universal' muscle relaxant in echinoderms. The first neuropeptides to be identified in echinoderms were two related peptides isolated from Asterias rubens known as SALMFamide-1 (S1) and SALMFamide-2 (S2). Both S1 and S2 cause relaxation of the starfish cardiac stomach, but with S2 being approximately ten times more potent than S1. SALMFamide neuropeptides have also been isolated from sea cucumbers, in which they cause relaxation of both gut and body wall muscle. Therefore, like NO, SALMFamides may also function as 'universal' muscle relaxants in echinoderms. The mechanisms by which SALMFamides cause relaxation of echinoderm muscle are not known, but several candidate signal transduction pathways are discussed here. The SALMFamides do not, however, appear to act by promoting release of NO, and muscle relaxation in echinoderms is therefore probably regulated by at least two neuronal signalling systems acting in parallel. Recently, other
Stress Relaxation in Entangled Polymer Melts
Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf
2010-01-01
and into the terminal relaxation regime for Z=10. Using the known (Rouse) mobility of unentangled chains and the melt entanglement length determined via the primitive path analysis of the microscopic topological state of our systems, we have performed parameter-free tests of several different tube models. We find......We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements...
Spin relaxation in nanowires by hyperfine coupling
Echeverria-Arrondo, C. [Department of Physical Chemistry, Universidad del Pais Vasco UPV/EHU, 48080 Bilbao (Spain); Sherman, E.Ya. [Department of Physical Chemistry, Universidad del Pais Vasco UPV/EHU, 48080 Bilbao (Spain); IKERBASQUE Basque Foundation for Science, 48011 Bilbao, Bizkaia (Spain)
2012-08-15
Hyperfine interactions establish limits on spin dynamics and relaxation rates in ensembles of semiconductor quantum dots. It is the confinement of electrons which determines nonzero hyperfine coupling and leads to the spin relaxation. As a result, in nanowires one would expect the vanishing of this effect due to extended electron states. However, even for relatively clean wires, disorder plays a crucial role and makes electron localization sufficient to cause spin relaxation on the time scale of the order of 10 ns. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Compact vs. Exponential-Size LP Relaxations
Carr, R.D.; Lancia, G.
2000-09-01
In this paper we introduce by means of examples a new technique for formulating compact (i.e. polynomial-size) LP relaxations in place of exponential-size models requiring separation algorithms. In the same vein as a celebrated theorem by Groetschel, Lovasz and Schrijver, we state the equivalence of compact separation and compact optimization. Among the examples used to illustrate our technique, we introduce a new formulation for the Traveling Salesman Problem, whose relaxation we show equivalent to the subtour elimination relaxation.
Relaxation time in disordered molecular systems
Rocha, Rodrigo P. [Departamento de Física, Universidade Federal de Santa Catarina, 88040-900 Florianópolis-SC (Brazil); Freire, José A., E-mail: jfreire@fisica.ufpr.br [Departamento de Física, Universidade Federal do Paraná, 81531-990 Curitiba-PR (Brazil)
2015-05-28
Relaxation time is the typical time it takes for a closed physical system to attain thermal equilibrium. The equilibrium is brought about by the action of a thermal reservoir inducing changes in the system micro-states. The relaxation time is intuitively expected to increase with system disorder. We derive a simple analytical expression for this dependence in the context of electronic equilibration in an amorphous molecular system model. We find that the disorder dramatically enhances the relaxation time but does not affect its independence of the nature of the initial state.
Nuclear magnetic resonance relaxation in multiple sclerosis
Larsson, H B; Barker, G J; MacKay, A
1998-01-01
OBJECTIVES: The theory of relaxation processes and their measurements are described. An overview is presented of the literature on relaxation time measurements in the normal and the developing brain, in experimental diseases in animals, and in patients with multiple sclerosis. RESULTS...... AND CONCLUSION: Relaxation time measurements provide insight into development of multiple sclerosis plaques, especially the occurrence of oedema, demyelination, and gliosis. There is also evidence that normal appearing white matter in patients with multiple sclerosis is affected. What is now needed are fast...
Lifetime and residual strength of wood subjected to static and variable load
Nielsen, Lauge Fuglsang
1996-01-01
The DVM-theory (Damaged Viscoelastic Material) previously developed by the author to predict lifetime of wood subjected to static loads is further developed in this paper such that variable loads can also be considered. Lifetime (real time or number of cycles) is predicted as a function of load...... is successfully compared with data from experiments representing different wood products. Algorithms and master graphs are developed which can be used in fatigue design of wood products in general. These graphs are valid for any creep behavior (relaxation, moisture content) and materials quality (grading...
Analytic three-loop static potential
Lee, Roman N.; Smirnov, Alexander V.; Smirnov, Vladimir A.; Steinhauser, Matthias
2016-09-01
We present analytic results for the three-loop static potential of two heavy quarks. The analytic calculation of the missing ingredients is outlined, and results for the singlet and octet potential are provided.
Static Stress Analysis of Security Injection Tank
无
2011-01-01
The static structural analysis of the security injection tank is made to make sure whether the tank can withstand concerned loads or not on all conditions conforming to concerned code prescripts and design requirements. The tanks
Static Water Vapor Feed Electrolyzer Project
National Aeronautics and Space Administration — Development of a static vapor feed electrolyzer utilizing an advanced bipolar plate that produces sub-saturated H2 and O2 is proposed. This novel bipolar design can...
Static Water Vapor Feed Electrolyzer Project
National Aeronautics and Space Administration — Development of a static vapor feed electrolyzer utilizing an advanced bipolar plate that produces sub-saturated H2 and O2 is proposed. This novel bipolar design can...
On static equilibrium and balance puzzler
Dey, Samrat; Saikia, Dipankar; Kalita, Deepjyoti; Debbarma, Anamika; Wahab, Shaheen Akhtar; Sarma, Saurabh
2012-01-01
The principles of static equilibrium are of special interest to civil engineers. For a rigid body to be in static equilibrium the condition is that net force and net torque acting on the body should be zero. That clearly signifies that if equal weights are placed on either sides of a balance, the balance should be in equilibrium, even if its beam is not horizontal (we have considered the beam to be straight and have no thickness, an ideal case). Thus, although the weights are equal, they will appear different which is puzzling. This also shows that the concept of equilibrium is confusing, especially neutral equilibrium is confused to be stable equilibrium. The study not only throws more light on the concept of static equilibrium, but also clarifies that a structure need not be firm and steady even if it is in static equilibrium.
1H relaxation dispersion in solutions of nitroxide radicals: Influence of electron spin relaxation
Kruk, D.; Korpała, A.; Kubica, A.; Kowalewski, J.; Rössler, E. A.; Moscicki, J.
2013-03-01
The work presents a theory of nuclear (1H) spin-lattice relaxation dispersion for solutions of 15N and 14N radicals, including electron spin relaxation effects. The theory is a generalization of the approach presented by Kruk et al. [J. Chem. Phys. 137, 044512 (2012)], 10.1063/1.4736854. The electron spin relaxation is attributed to the anisotropic part of the electron spin-nitrogen spin hyperfine interaction modulated by rotational dynamics of the paramagnetic molecule, and described by means of Redfield relaxation theory. The 1H relaxation is caused by electron spin-proton spin dipole-dipole interactions which are modulated by relative translational motion of the solvent and solute molecules. The spectral density characterizing the translational dynamics is described by the force-free-hard-sphere model. The electronic relaxation influences the 1H relaxation by contributing to the fluctuations of the inter-molecular dipolar interactions. The developed theory is tested against 1H spin-lattice relaxation dispersion data for glycerol solutions of 4-oxo-TEMPO-d16-15N and 4-oxo-TEMPO-d16-14N covering the frequency range of 10 kHz-20 MHz. The studies are carried out as a function of temperature starting at 328 K and going down to 290 K. The theory gives a consistent overall interpretation of the experimental data for both 14N and 15N systems and explains the features of 1H relaxation dispersion resulting from the electron spin relaxation.
Hydrogen sulfide and vascular relaxation
SUN Yan; TANG Chao-shu; DU Jun-bao; JIN Hong-fang
2011-01-01
Objective To review the vasorelaxant effects of hydrogen sulfide (H2S) in arterial rings in the cardiovascular system under both physiological and pathophysiological conditions and the possible mechanisms involved.Data sources The data in this review were obtained from Medline and Pubmed sources from 1997 to 2011 using the search terms "hydrogen sulfide" and ""vascular relaxation".Study selection Articles describing the role of hydrogen sulfide in the regulation of vascular activity and its vasorelaxant effects were selected.Results H2S plays an important role in the regulation of cardiovascular tone.The vasomodulatory effects of H2S depend on factors including concentration,species and tissue type.The H2S donor,sodium hydrosulfide (NarS),causes vasorelaxation of rat isolated aortic rings in a dose-dependent manner.This effect was more pronounced than that observed in pulmonary arterial rings.The expression of KATP channel proteins and mRNA in the aortic rings was increased compared with pulmonary artery rings.H2S is involved in the pathogenesis of a variety of cardiovascular diseases.Downregulation of the endogenous H2S pathway is an important factor in the pathogenesis of cardiovascular diseases.The vasorelaxant effects of H2S have been shown to be mediated by activation of KATP channels in vascular smooth muscle cells and via the induction of acidification due to activation of the CI/HCO3 exchanger.It is speculated that the mechanisms underlying the vasoconstrictive function of H2S in the aortic rings involves decreased NO production and inhibition of cAMP accumulation.Conclusion H2S is an important endogenous gasotransmitter in the cardiovascular system and acts as a modulator of vascular tone in the homeostatic regulation of blood pressure.
Selected static foot assessments do not predict medial longitudinal arch motion during running.
Langley, Ben; Cramp, Mary; Morrison, Stewart C
2015-01-01
Static assessments of the foot are commonly advocated within the running community to classify the foot with a view to recommending the appropriate type of running shoe. The aim of this work was to determine whether selected static foot assessment could predict medial longitudinal arch (MLA) motion during running. Fifteen physically active males (27 ± 5 years, 1.77 ± 0.04 m, 80 ± 10 kg) participated in the study. Foot Posture Index (FPI-6), MLA angle and rearfoot angle were measured in a relaxed standing position. MLA motion was calculated using the position of retro-reflective markers tracked by a VICON motion analysis system, while participants ran barefoot on a treadmill at a self-selected pace (2.8 ± 0.5 m.s(-1)). Bivariate linear regression was used to determine whether the static measures predicted MLA deformation and MLA angles at initial contact, midsupport and toe off. All three foot classification measures were significant predictors of MLA angle at initial contact, midsupport and toe off (p static foot classification measures were significant predictors of MLA deformation during the stance phase of running. Selected static foot measures did not predict dynamic MLA deformation during running. Given that MLA deformation has theoretically been linked to running injuries, the clinical relevance of predicting MLA angle at discrete time points during the stance phase of running is questioned. These findings also question the validity of the selected static foot classification measures when looking to characterise the foot during running. This indicates that alternative means of assessing the foot to inform footwear selection are required.
Statics formulas and problems : engineering mechanics 1
Gross, Dietmar; Wriggers, Peter; Schröder, Jörg; Müller, Ralf
2017-01-01
This book contains the most important formulas and more than 160 completely solved problems from Statics. It provides engineering students material to improve their skills and helps to gain experience in solving engineering problems. Particular emphasis is placed on finding the solution path and formulating the basic equations. Topics include: - Equilibrium - Center of Gravity, Center of Mass, Centroids - Support Reactions - Trusses - Beams, Frames, Arches - Cables - Work and Potential Energy - Static and Kinetic Friction - Moments of Inertia.
Typification of Statice dichotoma Cav. (Plumbaginaceae
Ferrer-Gallego, P. Pablo
2013-12-01
Full Text Available A lectotype and an epitype are here designated for Statice dichotoma Cav. (Plumbaginaceae, an endemic taxon from the central part of the Iberian Peninsula, which is currently named Limonium dichotomum (Cav. KuntzeSe designan un lectótipo y un epítipo para Statice dichotoma Cav. (Plumbaginaceae, un taxon endémico del centro de la península Ibérica, actualmente denominado Limonium dichotomum (Cav. Kuntze.
Static Validation of a Voting Protocol
Nielsen, Christoffer Rosenkilde; Andersen, Esben Heltoft; Nielson, Hanne Riis
2005-01-01
The desired security properties of electronic voting protocols include verifiability, accuracy, democracy and fairness. In this paper we use a static program analysis tool to validate these properties for one of the classical voting protocols under appropriate assumptions. The protocol is formali......The desired security properties of electronic voting protocols include verifiability, accuracy, democracy and fairness. In this paper we use a static program analysis tool to validate these properties for one of the classical voting protocols under appropriate assumptions. The protocol...
Transient stability and emergency control
无
2009-01-01
Comparability of emergency control strategies with different instability modes is the key issue to decide which control strategy to be implemented. This paper considers that the essential factor causing instability should be used to form a unified standard to assess the effectiveness of control strategies with different instability modes. Thus a switching control stabilization principle was proposed based on elimination of the unbalanced energy between mechanical and electrical energies of generator sets. Along this way, the difficulty of seeking a Lyapunov function was circumvented. According to the principle, an emergency control algorithm framework was established to handle transient stability assessment, control location selection and control amount evaluation. Within the framework, this paper studied instability mode transition, then proposed an algorithm based on prediction function and a new approach to normalized stability margin stemmed from static EEAC method, which can increase comparability of various control locations. The simulations on the New-England System verified the proposed emergency control method for stabilizing transient stability.
“I think relax, relax and it flows a lot easier”: Exploring client-generated relax strategies
Dianne Cirone
2014-10-01
Full Text Available Background. Some adult stroke survivors participating in Cognitive Orientation to daily Occupational Performance (CO-OP treatment programs self-generated relax strategies that have not been explored in previous CO-OP publications. The objective of this study was to describe the process by which adults with stroke used relax strategies and to explore the outcomes associated with their use. Methods. Secondary analysis of transcripts of intervention sessions from five participants was conducted. Results. All five participants applied relax strategies after initially observing a breakdown in performance that was attributed to increased fatigue or tension. The relax strategies used by the participants during their occupations included general relaxation, physical modifications to reduce tension, mental preparation, and pacing. The application of these strategies seemed to result in improved skill performance, reduced fatigue, and transfer to other activities. Conclusion. The relax strategy warrants further investigation as a potentially important therapeutic tool to improve occupational performance in individuals who have had a stroke.
Buyukturan, B; Guclu-Gunduz, A; Buyukturan, O; Dadali, Y; Bilgin, S; Kurt, E E
2017-11-01
This study aims at evaluating and comparing the effects of cervical stability training to combined cervical and core stability training in patients with neck pain and cervical disc herniation. Fifty patients with neck pain and cervical disc herniation were included in the study, randomly divided into two groups as cervical stability and cervical-core stability. Training was applied three times a week in three phases, and lasted for a total duration of 8 weeks. Pain, activation and static endurance of deep cervical flexor muscles, static endurance of neck muscles, cross-sectional diameter of M. Longus Colli, static endurance of trunk muscles, disability and kinesiophobia were assessed. Pain, activation and static endurance of deep cervical flexors, static endurance of neck muscles, cross-sectional diameter of M. Longus Colli, static endurance of trunk muscles, disability and kinesiophobia improved in both groups following the training sessions (p stability group produced a greater increase in the right transverse diameter of M. Longus Colli (p core stability group (p stability training provided benefit to patients with cervical disc herniation. The addition of core stability training did not provide any additional significant benefit. Further research is required to investigate the efficacy of combining other techniques with cervical stability training in patients with cervical disc herniation. Both cervical stability training and its combination with core stability training were significantly and similarly effective on neck pain and neck muscle endurance in patients with cervical disc herniation. © 2017 European Pain Federation - EFIC®.
Average-atom treatment of relaxation time in x-ray Thomson scattering from warm dense matter.
Johnson, W R; Nilsen, J
2016-03-01
The influence of finite relaxation times on Thomson scattering from warm dense plasmas is examined within the framework of the average-atom approximation. Presently most calculations use the collision-free Lindhard dielectric function to evaluate the free-electron contribution to the Thomson cross section. In this work, we use the Mermin dielectric function, which includes relaxation time explicitly. The relaxation time is evaluated by treating the average atom as an impurity in a uniform electron gas and depends critically on the transport cross section. The calculated relaxation rates agree well with values inferred from the Ziman formula for the static conductivity and also with rates inferred from a fit to the frequency-dependent conductivity. Transport cross sections determined by the phase-shift analysis in the average-atom potential are compared with those evaluated in the commonly used Born approximation. The Born approximation converges to the exact cross sections at high energies; however, differences that occur at low energies lead to corresponding differences in relaxation rates. The relative importance of including relaxation time when modeling x-ray Thomson scattering spectra is examined by comparing calculations of the free-electron dynamic structure function for Thomson scattering using Lindhard and Mermin dielectric functions. Applications are given to warm dense Be plasmas, with temperatures ranging from 2 to 32 eV and densities ranging from 2 to 64 g/cc.
Brownian particle-kinetics in a superparamagnetic ferrofluid subjected to static magnetic-field
Trisnanto, Suko Bagus; Kitamoto, Yoshitaka
2017-01-01
The stochastic Brownian particle-kinetics in a superparamagnetic ferrofluid at room temperature is of significance in nullifying total magnetization vectors of the suspended particles. Correspondingly, the apparent magnetization response observed under static magnetic field shows no hysteresis loop, but being linear at a given finite field-difference. Owing to this superparamagnetism, we propose a differential magnetometry to analyze the static field-induced particle-kinetics and further to identify the effective field-strength in reorienting particle-moments toward the applied field direction. A polydispersive ferrofluid containing iron-oxide nanoparticles, in practice, is subjected to a very-low oscillatory-field, immediately after applying the static-field. For a given frequency, we confirm a decreasing ac susceptibility as dc field-strength increases, which suggests a statistically less fluctuating magnetization-vectors. Via numerical integration of ac susceptibility recorded, we furthermore estimate the nonlinear quasi-static magnetization at various measurement frequencies. The resulting nonlinearity is attributable to the contributing relaxation dynamics of the particles. More importantly, the difference between dc and ac susceptibilities is found to be field-strength and frequency-dependent. Its value is further maximized at an effective field-strength, from which we identified the coexisting energy-barriers.
Richardson Number, stability and turbulence- A coherent view
Varkey, M.J.
As turbulence in water is governed by vertical mobility controlled by static stability and horizontal mobility controlled by currents, the Richardson Number should give a measure of turbulence also. It is argued in this note that inverse...
Jedlovszky-Hajdu, Angela, E-mail: angela.hajdu@net.sote.hu [Laboratory of Nanochemistry, Department of Biophysics and Radiation Biology, Semmelweis University, Nagyvarad Sq 4, H-1089 Budapest (Hungary); Tombacz, Etelka, E-mail: tombacz@chem.u-szeged.hu [Department of Physical Chemistry and Material Science, University of Szeged, Aradi Vt. Sq 1, Szeged 6720 (Hungary); Banyai, Istvan, E-mail: banyai.istvan@science.unideb.hu [Department of Colloid and Environmental Chemistry, University of Debrecen (Hungary); Babos, Magor, E-mail: babosmagor@yahoo.com [Euromedic Diagnostics Szeged Ltd., Semmelweis St 6, Szeged 6720 (Hungary); Palko, Andras, E-mail: palko@radio.szote.u-szeged.hu [Faculty of Medicine, Department of Radiology, University of Szeged (Hungary)
2012-09-15
At the moment the biomedical applications of magnetic fluids are the subject of intensive scientific interest. In the present work, magnetite nanoparticles (MNPs) were synthesized and stabilized in aqueous medium with different carboxylic compounds (citric acid (CA), polyacrylic acid (PAA), and sodium oleate (NaOA)), in order to prepare well stabilized magnetic fluids (MFs). The magnetic nanoparticles can be used in the magnetic resonance imaging (MRI) as contrast agents. Magnetic resonance relaxation measurements of the above MFs were performed at different field strengths (i.e., 0.47, 1.5 and 9.4 T) to reveal the field strength dependence of their magnetic responses, and to compare them with that of ferucarbotran, a well-known superparamagnetic contrast agent. The measurements showed characteristic differences between the tested magnetic fluids stabilized by carboxylic compounds and ferucarbotran. It is worthy of note that our magnetic fluids have the highest r2 relaxivities at the field strength of 1.5 T, where the most of the MRI works in worldwide. - Highlights: Black-Right-Pointing-Pointer Magnetic resonance relaxation measurements were done at different field strengths. Black-Right-Pointing-Pointer Results show characteristic differences between the tested carboxylated MFs. Black-Right-Pointing-Pointer r1 and r2 relaxivities depend on the thickness of the protecting layer. Black-Right-Pointing-Pointer MFs have high r2/r1 ratios at each magnetic field.
Anomalous longitudinal relaxation of nuclear spins in CaF{sub 2}
Kropf, Chahan M. [Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, D-79104, Freiburg (Germany); Kohlrautz, Jonas; Haase, Juergen [University of Leipzig, Faculty of Physics and Earth Sciences, Linnestr. 5, 04103, Leipzig (Germany); Fine, Boris V. [Skolkovo Institute of Science and Technology, 100 Novaya Str., Skolkovo, Moscow Region, 143025 (Russian Federation); Institute for Theoretical Physics, University of Heidelberg, Philosophenweg 12, 69120, Heidelberg (Germany)
2017-06-15
We consider the effect of non-secular resonances for interacting nuclear spins in solids which were predicted theoretically to exist in the presence of strong static and strong radio-frequency magnetic fields. These resonances imply corrections to the standard secular approximation for the nuclear spin-spin interaction in solids, which, in turn, should lead to an anomalous longitudinal relaxation in nuclear magnetic resonance experiments. In this article, we investigate the feasibility of the experimental observation of this anomalous longitudinal relaxation in calcium fluoride (CaF{sub 2}) and conclude that such an observation is realistic. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Biomechanics of failed deglutitive upper esophageal sphincter relaxation in neurogenic dysphagia.
Williams, Rohan B H; Wallace, Karen L; Ali, Galib N; Cook, Ian J
2002-07-01
Our aims were to examine the etiology and biomechanical properties of the nonrelaxing upper esophageal sphincter (UES) and the relationship between UES opening and failed relaxation. We examined the relationships among swallowed bolus volume, intrabolus pressure, sagittal UES diameter, the pharyngeal swallow response, and geniohyoid shortening in 18 patients with failed UES relaxation, 23 healthy aged controls, and 15 with Zenker's diverticulum. Etiology of failed UES relaxation was 56% medullary disease, 33% Parkinson's or extrapyramidal disease; and 11% idiopathic. Extent of UES opening ranged from absent to normal and correlated with preservation of the pharyngeal swallow response (P = 0.012) and geniohyoid shortening (P = 0.046). Intrabolus pressure was significantly greater compared with aged controls (P < 0.001) or Zenker's diverticulum (P < 0.001). The bolus volume-dependent increase in intrabolus pressure evident in controls was not observed in failed UES relaxation. The nonrelaxing UES therefore displays a constant loss of sphincter compliance throughout the full, and potentially normal, range of expansion during opening. Adequacy of UES opening is influenced by the degree of preservation of the pharyngeal swallow response and hyolaryngeal traction. In contrast, the stenotic UES displays a static loss of compliance, only apparent once the limit of sphincter expansion is reached.
Shmyreva, Anna A; Safdari, Majid; Furó, István; Dvinskikh, Sergey V
2016-06-14
Orders of magnitude decrease of (207)Pb and (199)Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. The effect is magnetic-field dependent but independent of the spinning speed in the range 200-15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time.
Optically-detected spin-echo method for relaxation times measurements in a Rb atomic vapor
Gharavipour, M.; Affolderbach, C.; Gruet, F.; Radojičić, I. S.; Krmpot, A. J.; Jelenković, B. M.; Mileti, G.
2017-06-01
We introduce and demonstrate an experimental method, optically-detected spin-echo (ODSE), to measure ground-state relaxation times of a rubidium (Rb) atomic vapor held in a glass cell with buffer-gas. The work is motivated by our studies on high-performance Rb atomic clocks, where both population and coherence relaxation times (T 1 and T 2, respectively) of the ‘clock transition’ (52S1/2 | {F}g = 1,{m}F=0> ≤ftrightarrow | {F}g=2,{m}F=0> ) are relevant. Our ODSE method is inspired by classical nuclear magnetic resonance spin-echo method, combined with optical detection. In contrast to other existing methods, like continuous-wave double-resonance (CW-DR) and Ramsey-DR, principles of the ODSE method allow suppression of decoherence arising from the inhomogeneity of the static magnetic field across the vapor cell, thus enabling measurements of intrinsic relaxation rates, as properties of the cell alone. Our experimental result for the coherence relaxation time, specific for the clock transition, measured with the ODSE method is in good agreement with the theoretical prediction, and the ODSE results are validated by comparison to those obtained with Franzen, CW-DR and Ramsey-DR methods. The method is of interest for a wide variety of quantum optics experiments with optical signal readout.
Residual stress relaxation in typical weld joints and its effect on fatigue and crack growth
Liangbi LI; Zhengquan WAN; Zili WANG; Chunyan JI
2009-01-01
Many factors influence the fatigue and crack growth behavior of welded joints. Some structures often undergo fairly large static loading before they enter service or variable amplitude cyclic loading when they are in service. The combined effect of both applied stress and high initial residual stress is expected to cause the residual stresses relaxation. Only a few papers seem to deal with appropriate procedures for fatigue analysis and crack growth by considering the combined effect of variable amplitude cyclic loading with residual stresses relaxation. In this article, some typical welded connections in ship-shaped structures are investigated with 3-D elastic-plastic finite element analysis. The effect of residual stress relaxation, initial residual stress, and the applied load after variable amplitude cyclic loading is revealed, and a formula for predicting the residual stress at hot spot quantitatively is proposed. Based on the formula, an improved fatigue procedure is introduced. Moreover, crack growth of typical weld joints considering residual stresses relaxation is studied.
Measurement of interfacial area from NMR time dependent diffusion and relaxation measurements.
Fleury, M
2017-09-07
The interfacial area between two immiscible phases in porous media is an important parameter for describing and predicting 2 phase flow. Although present in several models, experimental investigations are sparse due to the lack of appropriate measurement techniques. We propose two NMR techniques for the measurement of oil-water interfacial area: (i) a time dependent NMR diffusion technique applicable in static conditions, similar to those used for the measurement of the solid specific surface of a porous media, and (ii) a fast relaxation technique applicable in dynamic conditions while flowing, based on an interfacial relaxation mechanism induced by the inclusion of paramagnetic salts in the water phase. For dodecane relaxing on doped water, we found an oil interfacial relaxivity of 1.8μm/s, large enough to permit the measurement of specific interfacial surface as small as 1000cm(2)/cm(3). We demonstrate both NMR techniques in drainage followed by imbibition, in a model porous media with a narrow pore size distribution. While flowing, we observe that the interfacial area is larger in imbibition than in drainage, implying a different organization of the oil phase. In a carbonate sample with a wide pore size distribution, we evidence the gradual invasion of the smallest pores as the oil-water pressure difference is increased. Copyright © 2017. Published by Elsevier Inc.
Slow spin relaxation in dipolar spin ice.
Orendac, Martin; Sedlakova, Lucia; Orendacova, Alzbeta; Vrabel, Peter; Feher, Alexander; Pajerowski, Daniel M.; Cohen, Justin D.; Meisel, Mark W.; Shirai, Masae; Bramwell, Steven T.
2009-03-01
Spin relaxation in dipolar spin ice Dy2Ti2O7 and Ho2Ti2O7 was investigated using the magnetocaloric effect and susceptibility. The magnetocaloric behavior of Dy2Ti2O7 at temperatures where the orientation of spins is governed by ``ice rules`` (T Tice) revealed thermally activated relaxation; however, the resulting temperature dependence of the relaxation time is more complicated than anticipated by a mere extrapolation of the corresponding high temperature data [1]. A susceptibility study of Ho2Ti2O7 was performed at T > Tice and in high magnetic fields, and the results suggest a slow relaxation of spins analogous to the behavior reported in a highly polarized cooperative paramagnet [2]. [1] J. Snyder et al., Phys. Rev. Lett. 91 (2003) 107201. [2] B. G. Ueland et al., Phys. Rev. Lett. 96 (2006) 027216.
Energy landscape of relaxed amorphous silicon
Valiquette, Francis; Mousseau, Normand
2003-09-01
We analyze the structure of the energy landscape of a well-relaxed 1000-atom model of amorphous silicon using the activation-relaxation technique (ART nouveau). Generating more than 40 000 events starting from a single minimum, we find that activated mechanisms are local in nature, that they are distributed uniformly throughout the model, and that the activation energy is limited by the cost of breaking one bond, independently of the complexity of the mechanism. The overall shape of the activation-energy-barrier distribution is also insensitive to the exact details of the configuration, indicating that well-relaxed configurations see essentially the same environment. These results underscore the localized nature of relaxation in this material.
Precession Relaxation of Viscoelastic Oblate Rotators
Frouard, Julien
2016-01-01
Various perturbations (collisions, close encounters, YORP) destabilise the rotation of a small body, leaving it in a non-principal spin state. Then the body experiences alternating stresses generated by the inertial forces. The ensuing inelastic dissipation reduces the kinetic energy, without influencing the angular momentum. This yields nutation relaxation, i.e., evolution of the spin towards rotation about the maximal-inertia axis. Knowledge of the timescales needed to damp the nutation is crucial in studies of small bodies' dynamics. In the past, nutation relaxation has been described by an empirical quality factor introduced to parameterise the dissipation rate and to evade the discussion of the actual rheological parameters and their role in dissipation. This approach is unable to describe the dependence of the relaxation rate upon the nutation angle, because we do not know the quality factor's dependence on the frequency (which is a function of the nutation angle). This leaves open the question of relax...
Two-Body Relaxation in Cosmological Simulations
Binney, J; Binney, James; Knebe, Alexander
2002-01-01
The importance of two-body relaxation in cosmological simulations is explored with simulations in which there are two species of particles. The cases of mass ratio sqrt(2):1 and 4:1 are investigated. Simulations are run with both a fixed softening length and adaptive softening using the publicly available codes GADGET and MLAPM, respectively. The effects of two-body relaxation are detected in both the density profiles of halos and the mass function of halos. The effects are more pronounced with a fixed softening length, but even in this case they are not so large as to suggest that results obtained with one mass species are significantly affected by two-body relaxation. The simulations that use adaptive softening are slightly less affected by two-body relaxation and produce slightly higher central densities in the largest halos. They run about three times faster than the simulations that use a fixed softening length.
Structural relaxation in annealed hyperquenched basaltic glasses
Guo, Xiaoju; Mauro, John C.; Potuzak, M.
2012-01-01
The enthalpy relaxation behavior of hyperquenched (HQ) and annealed hyperquenched (AHQ) basaltic glass is investigated through calorimetric measurements. The results reveal a common onset temperature of the glass transition for all the HQ and AHQ glasses under study, indicating that the primary r...... relaxation is activated at the same temperature regardless of the initial departure from equilibrium. The analysis of secondary relaxation at different annealing temperatures provides insights into the enthalpy recovery of HQ glasses.......The enthalpy relaxation behavior of hyperquenched (HQ) and annealed hyperquenched (AHQ) basaltic glass is investigated through calorimetric measurements. The results reveal a common onset temperature of the glass transition for all the HQ and AHQ glasses under study, indicating that the primary...
Vibrational energy relaxation in liquid oxygen
Everitt, K. F.; Egorov, S. A.; Skinner, J. L.
1998-09-01
We consider theoretically the relaxation from the first excited vibrational state to the ground state of oxygen molecules in neat liquid oxygen. The relaxation rate constant is related in the usual way to the Fourier transform of a certain quantum mechanical force-force time-correlation function. A result from Egelstaff allows one instead to relate the rate constant (approximately) to the Fourier transform of a classical force-force time-correlation function. This Fourier transform is then evaluated approximately by calculating three equilibrium averages from a classical molecular dynamics simulation. Our results for the relaxation times (at two different temperatures) are within a factor of 5 of the experimental relaxation times, which are in the ms range.
Analytical representations for relaxation functions of glasses
Hilfer, R.
2002-01-01
Analytical representations in the time and frequency domains are derived for the most frequently used phenomenological fit functions for non-Debye relaxation processes. In the time domain the relaxation functions corresponding to the complex frequency dependent Cole-Cole, Cole-Davidson and Havriliak-Negami susceptibilities are also represented in terms of $H$-functions. In the frequency domain the complex frequency dependent susceptibility function corresponding to the time dependent stretche...
Vibrational relaxation in very high temperature nitrogen
Hansen, C. Frederick
1991-01-01
Vibrational relaxation of N2 molecules is considered at temperatures up to 40,000 K in gas mixtures that contain electrons as well as heavy collision partners. The theory of vibrational relaxation due to N2-N2 collisions is fit to experimental data to 10,000 K by choice of the shape of the intermolecular potential and size of the collision cross section. These values are then used to extrapolate the theory to 40,000 K.
Anomalous enthalpy relaxation in vitreous silica
Yue, Yuanzheng
2015-01-01
scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....
Message passing with relaxed moment matching
Qi, Yuan; Guo, Yandong
2012-01-01
Bayesian learning is often hampered by large computational expense. As a powerful generalization of popular belief propagation, expectation propagation (EP) efficiently approximates the exact Bayesian computation. Nevertheless, EP can be sensitive to outliers and suffer from divergence for difficult cases. To address this issue, we propose a new approximate inference approach, relaxed expectation propagation (REP). It relaxes the moment matching requirement of expectation propagation by addin...
Protein dynamics from nuclear magnetic relaxation.
Charlier, Cyril; Cousin, Samuel F; Ferrage, Fabien
2016-05-01
Nuclear magnetic resonance is a ubiquitous spectroscopic tool to explore molecules with atomic resolution. Nuclear magnetic relaxation is intimately connected to molecular motions. Many methods and models have been developed to measure and interpret the characteristic rates of nuclear magnetic relaxation in proteins. These approaches shed light on a rich and diverse range of motions covering timescales from picoseconds to seconds. Here, we introduce some of the basic concepts upon which these approaches are built and provide a series of illustrations.
Lagrange relaxation and Dantzig-Wolfe decomposition
Vidal, Rene Victor Valqui
1989-01-01
The paper concerns a large-scale linear programming problem having a block-diagonal structure with coupling constraints. It is shown that there are deep connections between the Lagrange relaxation techniques and the Dantzig-Wolfe decomposition methods......The paper concerns a large-scale linear programming problem having a block-diagonal structure with coupling constraints. It is shown that there are deep connections between the Lagrange relaxation techniques and the Dantzig-Wolfe decomposition methods...
Lagrange relaxation and Dantzig-Wolfe decomposition
Vidal, Rene Victor Valqui
1989-01-01
The paper concerns a large-scale linear programming problem having a block-diagonal structure with coupling constraints. It is shown that there are deep connections between the Lagrange relaxation techniques and the Dantzig-Wolfe decomposition methods......The paper concerns a large-scale linear programming problem having a block-diagonal structure with coupling constraints. It is shown that there are deep connections between the Lagrange relaxation techniques and the Dantzig-Wolfe decomposition methods...
Shear-stress relaxation and ensemble transformation of shear-stress autocorrelation functions
Wittmer, J. P.; Xu, H.; Baschnagel, J.
2015-02-01
We revisit the relation between the shear-stress relaxation modulus G (t ) , computed at finite shear strain 0 0 with Geq being the static equilibrium shear modulus. G (t ) and C(t ) | γ thus must become different for solids and it is impossible to obtain Geq alone from C(t ) | γ as often assumed. We comment briefly on self-assembled transient networks where Geq(f ) must vanish for a finite scission-recombination frequency f . We argue that G(t ) =C (t ) | τ=C(t ) | γ should reveal an intermediate plateau set by the shear modulus Geq(f =0 ) of the quenched network.
Orientational relaxation in semiflexible dendrimers.
Kumar, Amit; Biswas, Parbati
2013-12-14
The orientational relaxation dynamics of semiflexible dendrimers are theoretically calculated within the framework of optimized Rouse-Zimm formalism. Semiflexibility is modeled through appropriate restrictions in the direction and orientation of the respective bond vectors, while the hydrodynamic interactions are included via the preaveraged Oseen tensor. The time autocorrelation function M(i)(1)(t) and the second order orientational autocorrelation function P(i)(2)(t) are analyzed as a function of the branch-point functionality and the degree of semiflexibility. Our approach of calculating M(i)(1)(t) is completely different from that of the earlier studies (A. Perico and M. Guenza J. Chem. Phys., 1985, 83, 3103; J. Chem. Phys., 1986, 84, 510), where the expression of M(i)(1)(t) obtained from earlier studies does not demarcate the flexible dendrimers from the semiflexible ones. The component of global motion of the time autocorrelation function exhibits a strong dependence on both degree of semiflexibility and branch-point functionality, while the component of pulsation motion depends only on the degree of semiflexibility. But it is difficult to distinguish the difference in the extent of pulsation motion among the compressed (0 qualitative behavior of P(i)(2)(t) obtained from our calculations closely matches with the expression for P(exact)(2)(t) in the earlier studies. Theoretically calculated spectral density, J(ω), is found to depend on the degree of semiflexibility and the branch-point functionality for the compressed and expanded conformations of semiflexible dendrimers as a function of frequency, especially in the high frequency regime, where J(ω) decays with frequency for both compressed and expanded conformations of semiflexible dendrimers. This decay of the spectral density occurs after displaying a cross-over behavior with the variation in the degree of semiflexibility in the intermediate frequency regime. The characteristic area increases with the
Dielectric relaxation spectroscopy of phlogopite mica
Kaur, Navjeet; Singh, Mohan; Singh, Anupinder [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Awasthi, A.M. [Thermodynamics Laboratory, UGC-DAE Consortium for Scientific Research, Indore 452001 (India); Singh, Lakhwant, E-mail: lakhwant@yahoo.com [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India)
2012-11-15
An in-depth investigation of the dielectric characteristics of annealed phlogopite mica has been conducted in the frequency range 0.1 Hz-10 MHz and over the temperature range 653-873 K through the framework of dielectric permittivity, electric modulus and conductivity formalisms. These formalisms show qualitative similarities in relaxation processes. The frequency dependence of the M Double-Prime and dc conductivity is found to obey an Arrhenius law and the activation energy of the phlogopite mica calculated both from dc conductivity and the modulus spectrum is similar, indicating that same type of charge carriers are involved in the relaxation phenomena. The electric modulus and conductivity data have been fitted with the Havriliak-Negami function. Scaling of M Prime , M Double-Prime , ac conductivity has also been performed in order to obtain insight into the relaxation mechanisms. The scaling behaviour indicates that the relaxation describes the same mechanism at different temperatures. The relaxation mechanism was also examined using the Cole-Cole approach. The study elaborates that the investigation regarding the temperature and frequency dependence of dielectric relaxation in the phlogopite mica will be helpful for various cutting edge applications of this material in electrical engineering.
Dielectric relaxation of gamma irradiated muscovite mica
Kaur, Navjeet [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Singh, Mohan, E-mail: mohansinghphysics@gmail.com [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Singh, Lakhwant [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Awasthi, A.M. [Thermodynamics Laboratory, UGC-DAE Consortium for Scientific Research, Indore 452001 (India); Lochab, S.P. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)
2015-03-15
Highlights: • The present article reports the effect of gamma irradiation on the dielectric relaxation characteristics of muscovite mica. • Dielectric and electrical relaxations have been analyzed in the framework of dielectric permittivity, electric modulus and Cole–Cole formalisms. • The frequency dependent electrical conductivity has been rationalized using Johnsher’s universal power law. • The experimentally measured electric modulus and conductivity data have been fitted using Havriliak–Negami dielectric relaxation function. - Abstract: In the present research, the dielectric relaxation of gamma irradiated muscovite mica was studied in the frequency range of 0.1 Hz–10 MHz and temperature range of 653–853 K, using the dielectric permittivity, electric modulus and conductivity formalisms. The dielectric constants (ϵ′ and ϵ′′) are found to be high for gamma irradiated muscovite mica as compared to the pristine sample. The frequency dependence of the imaginary part of complex electric modulus (M′′) and dc conductivity data conforms Arrhenius law with single value of activation energy for pristine sample and two values of activation energy for gamma irradiated mica sample. The experimentally assessed electric modulus and conductivity information have been interpreted by the Havriliak–Negami dielectric relaxation explanation. Using the Cole–Cole framework, an analysis of real and imaginary characters of the electric modulus for pristine and gamma irradiated sample was executed which reflects the non-Debye relaxation mechanism.
Rounded stretched exponential for time relaxation functions.
Powles, J G; Heyes, D M; Rickayzen, G; Evans, W A B
2009-12-01
A rounded stretched exponential function is introduced, C(t)=exp{(tau(0)/tau(E))(beta)[1-(1+(t/tau(0))(2))(beta/2)]}, where t is time, and tau(0) and tau(E) are two relaxation times. This expression can be used to represent the relaxation function of many real dynamical processes, as at long times, t>tau(0), the function converges to a stretched exponential with normalizing relaxation time, tau(E), yet its expansion is even or symmetric in time, which is a statistical mechanical requirement. This expression fits well the shear stress relaxation function for model soft soft-sphere fluids near coexistence, with tau(E)Cole-Cole plots for dielectric and shear stress relaxation (both the modulus and viscosity forms). It is shown that both the dielectric spectra and dynamic shear modulus imaginary parts approach the real axis with a slope equal to 0 at high frequency, whereas the dynamic viscosity has an infinite slope in the same limit. This indicates that inertial effects at high frequency are best discerned in the modulus rather than the viscosity Cole-Cole plot. As a consequence of the even expansion in time of the shear stress relaxation function, the value of the storage modulus derived from it at very high frequency exceeds that in the infinite frequency limit (i.e., G(infinity)).
Stress relaxation in viscous soft spheres.
Boschan, Julia; Vasudevan, Siddarth A; Boukany, Pouyan E; Somfai, Ellák; Tighe, Brian P
2017-09-27
We report the results of molecular dynamics simulations of stress relaxation tests in athermal viscous soft sphere packings close to their unjamming transition. By systematically and simultaneously varying both the amplitude of the applied strain step and the pressure of the initial condition, we access both linear and nonlinear response regimes and control the distance to jamming. Stress relaxation in viscoelastic solids is characterized by a relaxation time τ* that separates short time scales, where viscous loss is substantial, from long time scales, where elastic storage dominates and the response is essentially quasistatic. We identify two distinct plateaus in the strain dependence of the relaxation time, one each in the linear and nonlinear regimes. The height of both plateaus scales as an inverse power law with the distance to jamming. By probing the time evolution of particle velocities during relaxation, we further identify a correlation between mechanical relaxation in the bulk and the degree of non-affinity in the particle velocities on the micro scale.
On convex relaxation of graph isomorphism.
Aflalo, Yonathan; Bronstein, Alexander; Kimmel, Ron
2015-03-10
We consider the problem of exact and inexact matching of weighted undirected graphs, in which a bijective correspondence is sought to minimize a quadratic weight disagreement. This computationally challenging problem is often relaxed as a convex quadratic program, in which the space of permutations is replaced by the space of doubly stochastic matrices. However, the applicability of such a relaxation is poorly understood. We define a broad class of friendly graphs characterized by an easily verifiable spectral property. We prove that for friendly graphs, the convex relaxation is guaranteed to find the exact isomorphism or certify its inexistence. This result is further extended to approximately isomorphic graphs, for which we develop an explicit bound on the amount of weight disagreement under which the relaxation is guaranteed to find the globally optimal approximate isomorphism. We also show that in many cases, the graph matching problem can be further harmlessly relaxed to a convex quadratic program with only n separable linear equality constraints, which is substantially more efficient than the standard relaxation involving n2 equality and n2 inequality constraints. Finally, we show that our results are still valid for unfriendly graphs if additional information in the form of seeds or attributes is allowed, with the latter satisfying an easy to verify spectral characteristic.
Static analysis of function calls in Erlang
Dániel Horpácsi
2013-06-01
Full Text Available Functions and their relations can affect numerous properties and metrics of a functional program. To identify and represent the functions and their calling connections, software analysers commonly apply semantic function analysis, which derives the static call graph of the program, based on its source code. Function calls however may be dynamic and complex, making it difficult to statically identify the callee. Dynamic calls are determined just at run-time, static analysis therefore cannot be expected to fully identify every call. Nevertheless, by utilising the results of a properly performed data-flow analysis as well as taking ambiguous references into account, numerous dynamic calls are discoverable and representable. We consider cases where the identifiers of the callee are statically determined, but they flow into the call expression from a different program point, and also, we manage to handle function calls whose identifiers are not fully identifiable at compile-time. By utilising the improved reference analysis, we extend the static call graph with various information about dynamic function calls. We investigate such a function call analysis in the programming language Erlang.
A study of relaxation techniques for the transient analysis of digital circuits
Chia, W. K.
1985-06-01
In the VLSI microelectronics era, the cost of the immense CPU time and memory storage for a standard circuit simulator has become prohibitive. In order to achieve dramatic improvement in the performance of the circuit simulator, there are two principal points of departure from the standard simulation approach, namely, tearing decomposition and relaxation decomposition. This research is to study the numerical convergence and stability properties of several of the relaxation algorithms that have been proposed for the simulation of VLSI circuits. The time-point Gauss-Seidel method with prediction, the exploitation of latency and event scheduling algorithms are implemented into a general purpose circuit simulator SLATE-R (a Simulator with Latency and Tearing--Relaxed version). The performance of the SLATE-R program in the analysis of various types of integrated circuit technologies is studied.
The structure of precipitation fronts for finite relaxation time
Stechmann, Samuel N.; Majda, Andrew J. [New York University, Department of Mathematics and Center for Atmosphere Ocean Science, Courant Institute of Mathematical Sciences, New York, NY (United States)
2006-11-15
When convection is parameterized in an atmospheric circulation model, what types of waves are supported by the parameterization? Several studies have addressed this question by finding the linear waves of simplified tropical climate models with convective parameterizations. In this paper's simplified tropical climate model, convection is parameterized by a nonlinear precipitation term, and the nonlinearity gives rise to precipitation front solutions. Precipitation fronts are solutions where the spatial domain is divided into two regions, and the precipitation (and other model variables) changes abruptly at the boundary of the two regions. In one region the water vapor is below saturation and there is no precipitation, and in the other region the water vapor is above saturation level and precipitation is nonzero. The boundary between the two regions is a free boundary that moves at a constant speed. It is shown that only certain front speeds are allowed. The three types of fronts that exist for this model are drying fronts, slow moistening fronts, and fast moistening fronts. Both types of moistening fronts violate Lax's stability criterion, but they are robustly realizable in numerical experiments that use finite relaxation times. Remarkably, here it is shown that all three types of fronts are robustly realizable analytically for finite relaxation time. All three types of fronts may be physically unreasonable if the front spans an unrealistically large physical distance; this depends on various model parameters, which are investigated below. From the viewpoint of applied mathematics, these model equations exhibit novel phenomena as well as features in common with the established applied mathematical theories of relaxation limits for conservation laws and waves in reacting gas flows. (orig.)
The use of (double) relaxation oscillation SQUIDs as a sensor
Duuren, van M.J.; Brons, G.C.S.; Kattouw, H.; Flokstra, J.; Rogalla, H.
1997-01-01
Relaxation Oscillation SQUIDs (ROSs) and Double Relaxation Oscillation SQUIDs (DROSs) are based on relaxation oscillations that are induced in hysteretic dc SQUIDs by an external L-R shunt. The relaxation frequency of a ROS varies with the applied flux Φ, whereas the output of a DROS is a dc voltage
The use of (double) relaxation oscillation SQUIDs as a sensor
van Duuren, M.J.; Brons, G.C.S.; Kattouw, H.; Flokstra, Jakob; Rogalla, Horst
1997-01-01
Relaxation Oscillation SQUIDs (ROSs) and Double Relaxation Oscillation SQUIDs (DROSs) are based on relaxation oscillations that are induced in hysteretic dc SQUIDs by an external L-R shunt. The relaxation frequency of a ROS varies with the applied flux Φ, whereas the output of a DROS is a dc
From Flow Logic to Static Type Systems in Coordination Languages
De Nicola, Rocco; Gorla, Daniele; Hansen, René Rydhof;
2008-01-01
; therefore, the correctness properties cannot be statically enforced. By contrast, static analysis approaches based on Flow Logic usually guarantee properties statically. In this paper we show how to combine these two approaches to obtain a static type system for describing secure access to tuple spaces...
30 CFR 57.6602 - Static electricity dissipation during loading.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Static electricity dissipation during loading... MINES Explosives Extraneous Electricity-Surface and Underground § 57.6602 Static electricity dissipation... generates a static electricity hazard— (a) An evaluation of the potential static electricity hazard shall be...
Xiong, Jin; Ding, Hai-Yan; Meng, Yin-Shan; Gao, Chen; Zhang, Xue-Jing; Meng, Zhao-Sha; Zhang, Yi-Quan; Shi, Wei; Wang, Bing-Wu; Gao, Song
2017-02-01
A hydroxide-bridged centrosymmetric Dy(III) dimer with each Dy(III) being five-coordinated has been synthesized using bulky hindered phenolate ligands. Magnetic studies revealed that this compound exhibits a slow magnetic relaxation of a single-ion origin together with a step-like magnetic hysteresis of the magnetic coupled cluster. The thermal relaxation barrier of magnetization is 721 K in the absence of a static magnetic field, while the intramolecular magnetic interaction is very large among reported 4f-only dimers. CASSCF calculations with a larger active space were performed to understand the electronic structure of the compound. The thermal relaxation regime and the quantum tunneling regime are well separated, representing a good model to study the relaxation mechanism of SMMs with intramolecular Dy-Dy magnetic interactions.
Investigating Static and Dynamic Light Scattering
Sun, Yong
2011-01-01
A new size, static radii $R_{s}$, can be measured accurately using Static Light Scattering (SLS) technique when the Rayleigh-Gans-Debye approximation is valid for dilute homogenous spherical particles in dispersion. The method proposed in this work not only can measures the particle size distribution and average molar mass accurately but also enables us to explore Dynamic Light Scattering (DLS) technique further. Detailed investigation of the normalized time auto-correlation function of the scattered light intensity $g^{2)}(\\tau)$ shows that the measurements of DLS can be expected accurately and the static and hydrodynamic radii of nanoparticles are different. Only at some special conditions, the Z-average hydrodynamic radius can be measured accurately at a given scattering angle. The fact that the values of average hydrodynamic radius measured at different scattering angles are consistent or the values of polydispersity index are small does not mean the particle size distribution is narrow or monodisperse.
Static Analysis for JavaScript
Jensen, Simon Holm
Web applications present unique challenges to designers of static analysis tools. One of these challenges is the language JavaScript used for client side scripting in the browser. JavaScript is a complex language with many pitfalls and poor tool support compared to other languages....... This dissertation describes the design and implementation of a static analysis for JavaScript that can assist programmers in finding bugs in code during development. We describe the design of a static analysis tool for JavaScript, built using the monotone framework. This analysis infers detailed type information...... about programs. This information can be used to detect bugs such as null pointer dereferences and unintended type coercions. The analysis is sound, enabling it to prove the absence of certain program errors. JavaScript is usually run within the context of the browser and the DOM API. The major...
Pheromone Static Routing Strategy for Complex Networks
Hu, Mao-Bin; Henry, Y. K. Lau; Ling, Xiang; Jiang, Rui
2012-12-01
We adopt the concept of using pheromones to generate a set of static paths that can reach the performance of global dynamic routing strategy [Phys. Rev. E 81 (2010) 016113]. The path generation method consists of two stages. In the first stage, a pheromone is dropped to the nodes by packets forwarded according to the global dynamic routing strategy. In the second stage, pheromone static paths are generated according to the pheromone density. The output paths can greatly improve traffic systems' overall capacity on different network structures, including scale-free networks, small-world networks and random graphs. Because the paths are static, the system needs much less computational resources than the global dynamic routing strategy.
Statics and rotational dynamics of composite beams
Ghorashi, Mehrdaad
2016-01-01
This book presents a comprehensive study of the nonlinear statics and dynamics of composite beams and consists of solutions with and without active elements embedded in the beams. The static solution provides the initial conditions for the dynamic analysis. The dynamic problems considered include the analyses of clamped (hingeless) and articulated (hinged) accelerating rotating beams. Two independent numerical solutions for the steady state and the transient responses are presented. The author illustrates that the transient solution of the nonlinear formulation of accelerating rotating beam converges to the steady state solution obtained by the shooting method. Other key areas considered include calculation of the effect of perturbing the steady state solution, coupled nonlinear flap-lag dynamics of a rotating articulated beam with hinge offset and aerodynamic damping, and static and dynamic responses of nonlinear composite beams with embedded anisotropic piezo-composite actuators. The book is intended as a t...
Extending and Enhancing SAS (Static Analysis Suite)
Ho, David
2016-01-01
The Static Analysis Suite (SAS) is an open-source software package used to perform static analysis on C and C++ code, helping to ensure safety, readability and maintainability. In this Summer Student project, SAS was enhanced to improve ease of use and user customisation. A straightforward method of integrating static analysis into a project at compilation time was provided using the automated build tool CMake. The process of adding checkers to the suite was streamlined and simplied by developing an automatic code generator. To make SAS more suitable for continuous integration, a reporting mechanism summarising results was added. This suitability has been demonstrated by inclusion of SAS in the Future Circular Collider Software nightly build system. Scalability of the improved package was demonstrated by using the tool to analyse the ROOT code base.
Schlüter, Steffen [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis Oregon USA; Department Soil Physics, Helmholtz-Centre for Environmental Research-UFZ, Halle Germany; Berg, Steffen [Shell Global Solutions International B.V., Rijswijk Netherlands; Li, Tianyi [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis Oregon USA; Vogel, Hans-Jörg [Department Soil Physics, Helmholtz-Centre for Environmental Research-UFZ, Halle Germany; Institut für Agrar- und Ernährungswissenschaften, Martin-Luther-Universität Halle-Wittenberg, Halle Germany; Wildenschild, Dorthe [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis Oregon USA
2017-06-01
The relaxation dynamics toward a hydrostatic equilibrium after a change in phase saturation in porous media is governed by fluid reconfiguration at the pore scale. Little is known whether a hydrostatic equilibrium in which all interfaces come to rest is ever reached and which microscopic processes govern the time scales of relaxation. Here we apply fast synchrotron-based X-ray tomography (X-ray CT) to measure the slow relaxation dynamics of fluid interfaces in a glass bead pack after fast drainage of the sample. The relaxation of interfaces triggers internal redistribution of fluids, reduces the surface energy stored in the fluid interfaces, and relaxes the contact angle toward the equilibrium value while the fluid topology remains unchanged. The equilibration of capillary pressures occurs in two stages: (i) a quick relaxation within seconds in which most of the pressure drop that built up during drainage is dissipated, a process that is to fast to be captured with fast X-ray CT, and (ii) a slow relaxation with characteristic time scales of 1–4 h which manifests itself as a spontaneous imbibition process that is well described by the Washburn equation for capillary rise in porous media. The slow relaxation implies that a hydrostatic equilibrium is hardly ever attained in practice when conducting two-phase experiments in which a flux boundary condition is changed from flow to no-flow. Implications for experiments with pressure boundary conditions are discussed.
Purnell, Thomas
2004-05-01
In accordance with proper perception of linguistic sound units, past research has demonstrated some degree of acoustic and physiological stability. In contrast, articulatory stability has been thought to be inconsistent because articulations may vary so long as the vocal tract area function results in appropriate formant structure [Atal et al., J. Acoust. Soc. Am. 63, 1535-1555 (1978)]. However, if the area function for the constriction and its anterior region can maintain acoustic stability, articulatory stability should be observed in the relational behavior of four tongue pellets used in xray microbeam data. Previous work examined normalized pellet data in order to arrive at an average posture for each vowel [Hashi et al., J. Acoust. Soc. Am. 104, 2426-2437 (1998)]. But by assuming static (average) gestures, the research fell short of a correct postural characterization. This study of tongue pellet speed and normalized pellet displacement of front vowels spoken by ten microbeam database subjects reports that the tongue tip pellet speed maxima identify vowel edges (end of vowel onset, beginning of offset) while displacement of the three anterior pellets identify changes in formant structure (e.g., two stable regions in the Northern Cities English front low vowel).
Anomalous Enthalpy Relaxation in Vitreous Silica
Yuanzheng eYue
2015-08-01
Full Text Available It is a challenge to calorimetrically determine the glass transition temperature (Tg of vitreous silica. Here we demonstrate that this challenge mainly arises from the extreme sensitivity of the Tg to the hydroxyl content in vitreous silica, but also from the irreversibility of its glass transition when repeating the calorimetric scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling has impact on enthalpy relaxation in glass. Here we find that vitreous silica (as a strong system exhibits striking anomalies in both glass transition and enthalpy relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica.
Gd-HOPO Based High Relaxivity MRI Contrast Agents
Datta, Ankona; Raymond, Kenneth
2008-11-06
Tris-bidentate HOPO-based ligands developed in our laboratory were designed to complement the coordination preferences of Gd{sup 3+}, especially its oxophilicity. The HOPO ligands provide a hexadentate coordination environment for Gd{sup 3+} in which all he donor atoms are oxygen. Because Gd{sup 3+} favors eight or nine coordination, this design provides two to three open sites for inner-sphere water molecules. These water molecules rapidly exchange with bulk solution, hence affecting the relaxation rates of bulk water olecules. The parameters affecting the efficiency of these contrast agents have been tuned to improve contrast while still maintaining a high thermodynamic stability for Gd{sup 3+} binding. The Gd- HOPO-based contrast agents surpass current commercially available agents ecause of a higher number of inner-sphere water molecules, rapid exchange of inner-sphere water molecules via an associative mechanism, and a long electronic relaxation time. The contrast enhancement provided by these agents is at least twice that of commercial contrast gents, which are based on polyaminocarboxylate ligands.
Static Properties of the Multiple-Sine-Gordon Systems
Peyravi, M; Montakhab, Afshin
2010-01-01
In this paper, we examine some basic properties of the multiple-Sine-Gordon (MSG) systems, which constitute a generalization of the celebrated sine-Gordon (SG) system. We start by showing how MSG systems can be viewed as a general class of periodic functions. Next, periodic and step-like solutions of these systems are discussed in some details. In particular, we study the static properties of such systems by considering slope and phase diagrams. We also use concepts like energy density and pressure to characterize and distinguish such solutions. We interpret these solutions as an interacting many body system, in which kinks and antikinks behave as extended particles. Finally, we provide a linear stability analysis of periodic solutions which indicates short wavelength solutions to be stable.
Spectral analysis of viscous static compressible fluid equilibria
Nunez, Manuel [Departamento de Analisis Matematico, Universidad de Valladolid, Valladolid (Spain)
2001-05-25
It is generally assumed that the study of the spectrum of the linearized Navier-Stokes equations around a static state will provide information about the stability of the equilibrium. This is obvious for inviscid barotropic compressible fluids by the self-adjoint character of the relevant operator, and rather easy for viscous incompressible fluids by the compact character of the resolvent. The viscous compressible linearized system, both for periodic and homogeneous Dirichlet boundary problems, satisfies neither condition, but it does turn out to be the generator of an immediately continuous, almost stable semigroup, which justifies the analysis of the spectrum as predictive of the initial behaviour of the flow. As for the spectrum itself, except for a unique negative finite accumulation point, it is formed by eigenvalues with negative real part, and nonreal eigenvalues are confined to a certain bounded subset of complex numbers. (author)
Undrained Behaviour of Silt under Static and Cyclic Loading
YANG Shaoli; ROLF Sandven; LARS Grande
2002-01-01
In this study, the undrained behaviour of silt under low stress level is studied. An effective preparation methodfor built in silt samples in the triaxial test was firstly developed. By triaxial testing of samples at low confining pressures itwas found that silt easily loses stability and liquefies. Loose silt may show temporary liquefaction under static loading, anddevelop full liquefaction under cyclic loading. The most important factors influencing the silt behaviour are porosity, confin-ing pressure, consolidation state, cyclic loading level and number of cycles. The maximum obtainable shear stress is primarilya function of the confining pressure and the internal frictional angle. The actual structure of the silt material is the key factorin controlling its behaviour.