Dynamic response characteristics of two transport models tested in the National Transonic Facility
NASA Technical Reports Server (NTRS)
Young, Clarence P., Jr.
1993-01-01
This paper documents recent experiences with measuring the dynamic response characteristics of a commercial transport and a military transport model during full scale Reynolds number tests in the National Transonic Facility. Both models were limited in angle of attack while testing at full scale Reynolds number and cruise Mach number due to pitch or stall buffet response. Roll buffet (wing buzz) was observed for both models at certain Mach numbers while testing at high Reynolds number. Roll buffet was more severe and more repeatable for the military transport model at cruise Mach number. Miniature strain-gage type accelerometers were used for the first time for obtaining dynamic data as a part of the continuing development of miniature dynamic measurements instrumentation for cryogenic applications. This paper presents the results of vibration measurements obtained for both the commercial and military transport models and documents the experience gained in the use of miniature strain gage type accelerometers.
NASA Technical Reports Server (NTRS)
Greenberg, Harry
1947-01-01
A frequency-response method for determining the critical control-gearing and hunting oscillations of airplanes with automatic pilots is presented. The method is graphical and has several advantages over the standard numerical procedure based on Routh's discriminant. The chief advantage of the method is that direct use can be made of the measured response characteristics of the automatic pilot. This feature is especially useful in determining the existence, amplitude, and frequency of the hunting oscillations that may be present when the automatic pilot has nonlinear dynamic characteristics. Several examples are worked out to illustrate the application of the frequency-response method in determining the effect of automatic-pilot lag or lead on critical control gearing and in determining the amplitude and frequency hunting. It is shown that the method may be applied to the case of a control geared to airplane motions about two axes.
Dynamic response and transfer characteristics of joint neurons in somatosensory thalamus of the cat.
Yin, T C; Williams, W J
1976-05-01
1. The dynamic response of neurons sensitive to knee joint rotation in the cat somatosensory thalamus was studied during sinusoidal variation of joint angle. The input sine waves were applied with a precise voltage-controlled, electromechanical actuator. The average rate of discharge of a single cell was considered as the output parameter. Describing functions of the sensory system were extracted by correlation and spectral analysis techniques. The effects of anesthetic, bias angle, and excursion angle were investigated. Discrete and swept sinusoidal waveforms between 0.1 and 7.0 Hz were used as inputs.2. The majority of joint cells in the thalamus were rapidly adapting and had frequency-response curves that were characterized as highpass filters. Although the major features of the response curves for individual cells were very similar, they could not all be fit with a single transfer function. The describing function of all the rapidly adapting cells averaged together was well fit by a transfer function that could be termed velocity sensitive in the bandwidth between 0.1 and 6.5 Hz. Most of these phasic cells showed a phase-locking tendency, particularly at high frequencies.3. The dynamics of the response for the rapidly adapting cells was relatively independent of anesthetic, bias angle, and excursion angle. Threshold and saturation effects were exhibited by some cells for very small (less than 1 degree) and large (greater than 10 degrees) input amplitudes, respectively. In addition a few (17%) showed a bidirectional response, i.e., responded at both flexion and extension of the limb. The anesthetic had a strong effect in depressing the spontaneous discharge of the cells and seemed to change the character of the tonic response by introducing a bursting component.4. The transfer characteristic of the thalamic cells was found to be a single-pole low-pass filter plus a time delay. The optimized value for the filter was found to have a corner frequency of 6.0 Hz with
Dynamic response characteristics of dual flow-path integrally bladed rotors
NASA Astrophysics Data System (ADS)
Beck, Joseph A.; Brown, Jeffrey M.; Scott-Emuakpor, Onome E.; Cross, Charles J.; Slater, Joseph C.
2015-02-01
New turbine engine designs requiring secondary flow compression often look to dual flow-path integrally bladed rotors (DFIBRs) since these stages have the ability to perform work on the secondary, or bypassed, flow-field. While analogous to traditional integrally bladed rotor stages, DFIBR designs have many differences that result in unique dynamic response characteristics that must be understood to avoid fatigue. This work investigates these characteristics using reduced-order models (ROMs) that incorporate mistuning through perturbations to blade frequencies. This work provides an alternative to computationally intensive geometric-mistuning approaches for DFIBRs by utilizing tuned blade mode reductions and substructure coupling in cyclic coordinates. Free and forced response results are compared to full finite element model (FEM) solutions to determine if any errors are related to the reduced-order model formulation reduction methods. It is shown that DFIBRs have many more frequency veering regions than their single flow-path integrally blade rotor (IBR) counterparts. Modal families are shown to transition between system, inner-blade, and outer-blade motion. Furthermore, findings illustrate that while mode localization of traditional IBRs is limited to a single or small subset of blades, DFIBRs can have modal energy localized to either an inner- or outer-blade set resulting in many blades responding above tuned levels. Lastly, ROM forced response predictions compare well to full FEM predictions for the two test cases shown.
NASA Astrophysics Data System (ADS)
Wang, Bo; Zheng, Jun; Si, Shuaishuai; Qian, Nan; Li, Haitao; Li, Jipeng; Deng, Zigang
2016-07-01
Off-centre operation of high-temperature superconducting (HTS) maglev systems caused by inevitable conditions such as the misregistration of vehicle, crosswind and curve negotiation, may change the distribution of the trapped flux in the HTS bulks and the magnetic interaction between HTS bulks and the PMG. It impacts on the performance of HTS maglev, and more seriously makes the maglev vehicle overturned. Therefore, understanding the performance of the HTS maglev in off-center operation is very important. In this paper, the dynamic response characteristics of a cryostat with twenty-four onboard YBaCuO superconductor bulks were experimentally investigated at different eccentric distances under loads before the initial FC process. Parameters such as vibration accelerations, displacement, natural frequency and dynamic stiffness were acquired and analyzed via the B&K vibration analyzer and laser displacement sensors. Results suggest that the natural frequency and dynamic stiffness of the maglev vehicle would be obviously reduced with the eccentric distance, posing negative effects on the stability of HTS maglev.
Evaluation of space shuttle main engine fluid dynamic frequency response characteristics
NASA Technical Reports Server (NTRS)
Gardner, T. G.
1980-01-01
In order to determine the POGO stability characteristics of the space shuttle main engine liquid oxygen (LOX) system, the fluid dynamic frequency response functions between elements in the SSME LOX system was evaluated, both analytically and experimentally. For the experimental data evaluation, a software package was written for the Hewlett-Packard 5451C Fourier analyzer. The POGO analysis software is documented and consists of five separate segments. Each segment is stored on the 5451C disc as an individual program and performs its own unique function. Two separate data reduction methods, a signal calibration, coherence or pulser signal based frequency response function blanking, and automatic plotting features are included in the program. The 5451C allows variable parameter transfer from program to program. This feature is used to advantage and requires only minimal user interface during the data reduction process. Experimental results are included and compared with the analytical predictions in order to adjust the general model and arrive at a realistic simulation of the POGO characteristics.
Nikolelis, D P; Krull, U J
1990-07-01
The dynamic response characteristics of a carbon dioxide gas sensor were studied to determine the potential for application of the device to the kinetic assay of substrate(s) under pseudo first-order kinetics. The dependence of the time constant on the concentration of carbon dioxide was determined by using convolution mathematics to analyse potentiometric changes caused by abrupt alterations of gas concentration. The operational conditions of the CO2 sensor were optimised for the development of enzyme electrodes, so that the mass-transport phenomena occurring during the course of the enzymic reactions were enhanced. As a result, the kinetic analysis of substrate(s) was performed more rapidly (2-6 min), with greater sensitivity and with an improved detection limit (10-5 M). A kinetic reaction-rate method for the determination of aspartame in dietary foodstuffs is proposed as a rapid and inexpensive alternative to a classical high-performance liquid chromatographic method. PMID:2121066
Structural-dynamic-response characteristics of Darrieus vertical-axis wind turbines
Sullivan, W.N.
1981-01-01
Operational experience at Sandia National Laboratories (SNL) with Darrieus-type vertical axis wind turbines (VAWTs) has indicated that a variety of dynamic issues can affect structural performance of the system. The observation and analysis of structural dynamic responses in the VAWT have been divided among three major aspects of the system; namely rotor vibrations, torsional response of the drive train, and transverse vibrations of the cables. This division is not arbitrary, but is rather because the response of these subsystems can be accurately decoupled from each other in most circumstances. This paper will present only a brief summary of the efforts now underway at SNL in the area of structural dynamics. The emphasis will be on discussing the status of our analytical tools, the quantity and quality of existing experimental confirmation data, and the implications structural dynamic issues have on rotor design.
NASA Astrophysics Data System (ADS)
Wang, Zuo-Cai; Xin, Yu; Ren, Wei-Xin
2016-08-01
This paper proposes a new nonlinear joint model updating method for shear type structures based on the instantaneous characteristics of the decomposed structural dynamic responses. To obtain an accurate representation of a nonlinear system's dynamics, the nonlinear joint model is described as the nonlinear spring element with bilinear stiffness. The instantaneous frequencies and amplitudes of the decomposed mono-component are first extracted by the analytical mode decomposition (AMD) method. Then, an objective function based on the residuals of the instantaneous frequencies and amplitudes between the experimental structure and the nonlinear model is created for the nonlinear joint model updating. The optimal values of the nonlinear joint model parameters are obtained by minimizing the objective function using the simulated annealing global optimization method. To validate the effectiveness of the proposed method, a single-story shear type structure subjected to earthquake and harmonic excitations is simulated as a numerical example. Then, a beam structure with multiple local nonlinear elements subjected to earthquake excitation is also simulated. The nonlinear beam structure is updated based on the global and local model using the proposed method. The results show that the proposed local nonlinear model updating method is more effective for structures with multiple local nonlinear elements. Finally, the proposed method is verified by the shake table test of a real high voltage switch structure. The accuracy of the proposed method is quantified both in numerical and experimental applications using the defined error indices. Both the numerical and experimental results have shown that the proposed method can effectively update the nonlinear joint model.
Failure characteristics of the isolated distal radius in response to dynamic impact loading.
Burkhart, Timothy A; Andrews, David M; Dunning, Cynthia E
2012-06-01
We examined the mechanical response of the distal radius pre-fracture and at fracture under dynamic impact loads. The distal third of eight human cadaveric radii were potted and placed in a custom designed pneumatic impact system. The distal intra-articular surface of the radius rested against a model scaphoid and lunate, simulating 45° of wrist extension. The scaphoid and lunate were attached to a load cell that in turn was attached to an impact plate. Impulsive impacts were applied at increasing energy levels, in 10 J increments, until fracture occurred. Three 45° stacked strain gauge rosettes were affixed along the length of the radius quantifying the bone strains. The mean (SD) fracture energy was 45.5 (16) J. The mean (SD) resultant impact reaction force (IRFr) at failure was 2,142 (1,229) N, resulting in high compressive strains at the distal (2,718 (1,698) µε) and proximal radius (3,664 (1,890) µε). We successfully reproduced consistent fracture patterns in response to dynamic loads. The fracture energy and forces reported here are lower and the strains are higher than those previously reported and can likely be attributed to the controlled, incremental, dynamic nature of the applied loads. PMID:22083972
Characteristics and control response of the TOPAZ II Reactor System Real-time Dynamic Simulator
Kwok, K.S.
1993-11-12
A dynamic simulator of the TOPAZ II reactor system has been developed for the Nuclear Electric Propulsion Space Test Program. The simulator combines first-principle modeling and empirical correlations in its algorithm to attain the modeling accuracy and computational through-put that are required for real-time execution. The overall execution time of the simulator for each time step is 15 ms when no data is written to the disk, and 18 ms when nine double precision data points are written to the disk once in every time step. The simulation program has been tested and it is able to handle a step decrease of $8 worth of reactivity. It also provides simulations of fuel, emitter, collector, stainless steel, and ZrH moderator failures. Presented in this paper are the models used in the calculations, a sample simulation session, and a discussion of the performance and limitations of the simulator. The simulator has been found to provide realistic real-time dynamic response of the TOPAZ II reactor system under both normal and casualty conditions.
Research of dynamical Characteristics of slow deformation Waves as Massif Responses on Explosions
NASA Astrophysics Data System (ADS)
Hachay, Olga; Khachay, Oleg; Shipeev, Oleg
2013-04-01
The research of massif state with use of approaches of open system theory [1-3] was developed for investigation the criterions of dissipation regimes for real rock massifs, which are under heavy man-caused influence. For realization of that research we used the data of seismic catalogue of Tashtagol mine. As a result of the analyze of that data we defined character morphology of phase trajectories of massif response, which was locally in time in a stable state: on the phase plane with coordinates released by the massif during the dynamic event energy E and lg(dE/dt) there is a local area as a ball of twisted trajectories and some not great bursts from that ball, which are not greater than 105 joules. In some time intervals that burst can be larger, than 105 joules, achieving 106 joules and yet 109 joules. [3]. Evidently there are two reciprocal depend processes: the energy accumulation in the attracted phase trajectories area and resonance fault of the accumulated energy. But after the fault the system returns again to the same attracted phase trajectories area. For analyzing of the thin structure of the chaotic area we decided to add the method of processing of the seismic monitoring data by new parameters. We shall consider each point of explosion as a source of seismic or deformation waves. Using the kinematic approach of seismic information processing we shall each point of the massif response use as a time point of the first arrival of the deformation wave for calculation of the wave velocity, because additionally we know the coordinates of the fixed response and the coordinates of explosion. The use of additional parameter-velocity of slow deformation wave propagation allowed us with use method of phase diagrams identify their hierarchic structure, which allow us to use that information for modeling and interpretation the propagation seismic and deformation waves in hierarchic structures. It is researched with use of that suggested processing method the thin
Quasi-Static and Dynamic Response Characteristics of F-4 Bias-Ply and Radial-Belted Main Gear Tires
NASA Technical Reports Server (NTRS)
Davis, Pamela A.
1997-01-01
An investigation was conducted at Langley Research Center to determine the quasi-static and dynamic response characteristics of F-4 military fighter 30x11.5-14.5/26PR bias-ply and radial-belted main gear tires. Tire properties were measured by the application of vertical, lateral, and fore-and-aft loads. Mass moment-of-inertia data were also obtained. The results of the study include quasi-static load-deflection curves, free-vibration time-history plots, energy loss associated with hysteresis, stiffness and damping characteristics, footprint geometry, and inertia properties of each type of tire. The difference between bias-ply and radial-belted tire construction is given, as well as the advantages and disadvantages of each tire design. Three simple damping models representing viscous, structural, and Coulomb friction are presented and compared with the experimental data. The conclusions discussed contain a summary of test observations.
Jung, HoHyun; Chun, Keyoung Jin; Hong, Jaesoo; Lim, Dohyung
2015-01-01
Balance is important in daily activities and essential for maintaining an independent lifestyle in the elderly. Recent studies have shown that balance rehabilitation training can improve the balance ability of the elderly, and diverse balance rehabilitation training equipment has been developed. However, there has been little research into optimized strategies for balance rehabilitation training. To provide an optimized strategy, we analyzed the balance characteristics of participants in response to the rotation of a base plate on multiple axes. Seven male adults with no musculoskeletal or nervous system-related diseases (age: 25.5±1.7 years; height: 173.9±6.4 cm; body mass: 71.3±6.5 kg; body mass index: 23.6±2.4 kg/m2) were selected to investigate the balance rehabilitation training using customized rehabilitation equipment. Rotation of the base plate of the equipment was controlled to induce dynamic rotation of participants in the anterior–posterior, right-diagonal, medial–lateral, and left-diagonal directions. We used a three-dimensional motion capture system employing infrared cameras and the Pedar Flexible Insoles System to characterize the major lower-extremity joint angles, center of body mass, and center of pressure. We found statistically significant differences between the changes in joint angles in the lower extremities in response to dynamic rotation of the participants (P<0.05). The maximum was greater with anterior–posterior and medial–lateral dynamic rotation than with that in other directions (P<0.05). However, there were no statistically significant differences in the frequency of center of body mass deviations from the base of support (P>0.05). These results indicate that optimizing rotation control of the base plate of balance rehabilitation training equipment to induce anterior–posterior and medial–lateral dynamic rotation preferentially can lead to effective balance training. Additional tests with varied speeds and ranges of
NASA Technical Reports Server (NTRS)
Free, April M.; Flowers, George T.; Trent, Victor S.
1993-01-01
Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotor-dynamic model and assess the dynamic behavior of a magnetic bearing rotor system which includes the effects of auxiliary bearings. Of particular interest is the effects of introducing sideloading into such a system during failure of the magnetic bearing. A model is developed from an experimental test facility and a number of simulation studies are performed. These results are presented and discussed.
NASA Technical Reports Server (NTRS)
Free, April M.; Flowers, George T.; Trent, Victor S.
1995-01-01
Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotordynamic model which describes the dynamic behavior of a flexible rotor system with magnetic bearings including auxiliary bearings. The model is based upon an experimental test facility. Some simulation studies are presented to illustrate the behavior of the model. In particular, the effects of introducing sideloading from the magnetic bearing when one coil fails is studied.
NASA Astrophysics Data System (ADS)
Wang, B.; Zheng, J.; Che, T.; Zheng, B. T.; Si, S. S.; Deng, Z. G.
2015-12-01
The permanent magnet guideway (PMG) is very important for the performance of the high temperature superconducting (HTS) system in terms of electromagnetic force and operational stability. The dynamic response characteristics of a HTS maglev model levitating on two types of PMG, which are the normal PMG with iron flux concentration and Halbach-type PMG, were investigated by experiments. The dynamic signals for different field-cooling heights (FCHs) and loading/unloading processes were acquired and analyzed by a vibration analyzer and laser displacement sensors. The resonant frequency, stiffness and levitation height of the model were discussed. It was found that the maglev model on the Halbach-type PMG has higher resonant frequency and higher vertical stiffness compared with the normal PMG. However, the low lateral stiffness of the model on the Halbach-type PMG indicates poor lateral stability. Besides, the Halbach-type PMG has better loading capacity than the normal PMG. These results are helpful to design a suitable PMG for the HTS system in practical applications.
NASA Technical Reports Server (NTRS)
Murphy, A. C.
1981-01-01
Experimental data and correlative analytical results on the flutter and gust response characteristics of a torsion-free-wing (TFW) fighter airplane model are presented. TFW consists of a combined wing/boom/canard surface and was tested with the TFW free to pivot in pitch and with the TFW locked to the fuselage. Flutter and gust response characteristics were measured in the Langley Transonic Dynamics Tunnel with the complete airplane model mounted on a cable mount system that provided a near free flying condition. Although the lowest flutter dynamic pressure was measured for the wing free configuration, it was only about 20 deg less than that for the wing locked configuration. However, no appreciable alleviation of the gust response was measured by freeing the wing.
NASA Astrophysics Data System (ADS)
Wang, Hao; Chen, Chunchao; Xing, Chenxi; Li, Aiqun
2014-09-01
A 3D finite element (FE) model for the Sutong cable-stayed bridge (SCB) is established based on ANSYS. The dynamic characteristics of the bridge are analyzed using a subspace iteration method. Based on recorded wind data, the measured spectra expression is presented using the nonlinear least-squares regression method. Turbulent winds at the bridge site are simulated based on the spectral representation method and the FFT technique. The influence of some key structural parameters and measures on the dynamic characteristics of the bridge are investigated. These parameters include dead load intensity, as well as vertical, lateral and torsional stiffness of the steel box girder. In addition, the influence of elastic stiffness of the connection device employed between the towers and the girder on the vibration mode of the steel box girder is investigated. The analysis shows that all of the vertical, lateral and torsional buffeting displacement responses reduce gradually as the dead load intensity increases. The dynamic characteristics and the structural buffeting displacement response of the SCB are only slightly affected by the vertical and torsional stiffness of the steel box girder, and the lateral and torsional buffeting displacement responses reduce gradually as the lateral stiffness increases. These results provide a reference for dynamic analysis and design of super-long-span cable-stayed bridges.
Roditaki, A.; Nikolelis, D.P.; Papastathopoulos, D.S. )
1993-03-01
The performance and dynamic response characteristics of the potentiometric carbon dioxide gas sensor with an alternative to the commercially available silicon rubber membrane are studied in this paper. This study was performed in the course to choose a low cost membrane and possibly to further optimize the time response of this sensor. The membrane used was a microporous Teflon membrane which is used in ammonia gas sensors. The results have shown that the CO[sub 2] gas-sensing probe with the Teflon membrane shows similar performance characteristics as the silicon rubber membrane, but improved stability with time. Convolution mathematics were also used to study the dynamic response characteristics of the gas sensor with the Teflon membrane and the results have shown that practically similar time constants are obtained as when a silicon rubber membrane is used. Therefore, the less costly membrane can replace the silicon rubber membrane when CO[sub 2] is being monitored and a gas-sensing probe can be constructed through this means, by using a Teflon membrane and a 1 mM NaHCO[sub 3]-100 mM NaCl internal filling solution. 10 refs., 5 figs.
Dynamic and Performance Characteristics of Baseball Bats
ERIC Educational Resources Information Center
Bryant, Fred O.; And Others
1977-01-01
The dynamic and performance characteristics of wooden and aluminum baseball bats were investigated in two phases; the first dealing with the velocity of the batted balls, and the second with a study of centers of percussion and impulse response at the handle. (MJB)
NASA Astrophysics Data System (ADS)
Humeau, Anne; Koitka, Audrey; Saumet, Jean-Louis; L'Huillier, Jean-Pierre
2003-10-01
The laser Doppler flowmetry technique has recently been used to report a significant transient increase of the cutaneous blood flow signal when a local non-noxious pressure is applied progressively on the skin (11.1 Pa/s). The present work analyses the dynamic characteristics of this vasodilatory reflex response on anaesthetised rats. A de-noising algorithm using wavelets is proposed to obtain accurate values of these dynamic characteristics. The blood flow peak and the time to reach this peak are computed on the de-noised recordings. The results show that the mean time to reach the peak of perfusion is 85.3 s (time t = 0 at the beginning of the pressure application). The mean peak value is 188.3 arbitrary units (a.u.), whereas the mean value of the perfusion before the pressure application is 113.4 a.u. The mean minimum value obtained at the end of the experiment is 60.7 a.u. This latter value is, on the average, reached 841.3 s after the beginning of the pressure application. The comparison of the dynamic characteristics, computed with the de-noising algorithm on signals obtained in other situations, will give a better understanding on some cutaneous lesions such as those present on diabetic people.
NASA Astrophysics Data System (ADS)
Hachay, Olga; Khachay, Oleg; Shipeev, Oleg
2015-04-01
As a result of long-term natural geomechanics and geophysical observation data on mines of complex ore rocks, generalization of the non-linear reaction of rock massif to heavy dynamic influences have been established. In addition, pendulum type waves have been observed and the sources of them have been located inside geoblocks of different hierarchic levels (Oparin et al., 2010). At the same time, these waves propagate with wide low (compared with seismic waves) velocity values (Kurlenja et al., 1993; Oparin et al., 2006). Research into the massif state with the use of the dynamic systems theory approach (Naimark et al., 2009; Chulichkov, 2003; Hachay et al., 2010) has been developed to ascertain the criteria of dissipative regimes changing for real rock massifs, which are under heavy man-caused influence. To realize such research we used the data from the seismic record of the Tashtagol mine for the two-year period from June 2006 up to June 2008. We used the space-time coordinates for all dynamic massif event responses, which occurred during that period inside the mine space and for the explosions - values fixed by seismic station energy (Hachay et al., 2010). The phase diagrams of the massif state for the northern and southern parts of the mine space were plotted in coordinates Ev(t) and d(Ev(t))/dt, t - time - in parts of 24 hours, Ev - the dissipated massive seismic energy - in joules. Hachay et al., (2010) analysed the morphology of seismic response phase trajectories on the explosion influences during different serial intervals in the southern part of the mine. In that period, according to data for different explosions in the mine, the majority of the total energy had been injected into the southern part of the mine. Moreover, at the end of 2007, just in the southern part, the strongest rock burst during the whole history of the working mine happened. We developed a new processing method of seismological information in real, which we can use directly in the
NASA Astrophysics Data System (ADS)
Humeau, Anne; Koitka, Audrey; Abraham, Pierre; Saumet, Jean-Louis; L'Huillier, Jean-Pierre
2004-09-01
In the biomedical field, the laser Doppler flowmetry (LDF) technique is a non-invasive method to monitor skin perfusion. On the skin of healthy humans, LDF signals present a significant transient increase in response to a local and progressive pressure application. This vasodilatory reflex response may have important implications for cutaneous pathologies involved in various neurological diseases and in the pathophysiology of decubitus ulcers. The present work analyses the dynamic characteristics of these signals on young type 1 diabetic patients, and on healthy age-matched subjects. To obtain accurate dynamic characteristic values, a de-noising wavelet-based algorithm is first applied to LDF signals. All the de-noised signals are then normalised to the same value. The blood flow peak and the time to reach this peak are then calculated on each computed signal. The results show that a large vasodilation is present on signals of healthy subjects. The mean peak occurs at a pressure of 3.2 kPa approximately. However, a vasodilation of limited amplitude appears on type 1 diabetic patients. The maximum value is visualised, on the average, when the pressure is 1.1 kPa. The inability for diabetic patients to increase largely their cutaneous blood flow may bring explanations to foot ulcers.
Response characteristics of the human torsional vestibuloocular reflex
NASA Technical Reports Server (NTRS)
Peterka, Robert J.
1992-01-01
The characteristics of the response dynamics of the human torsional vestibuloocular reflex were studied during controlled rotations about an earth-horizontal axis. The results extended the frequency range to 2 Hz and identified the nonlinearity of the amplitude response.
NASA Technical Reports Server (NTRS)
Sadoff, Melvin
1958-01-01
The results of a fixed-base simulator study of the effects of variable longitudinal control-system dynamics on pilot opinion are presented and compared with flight-test data. The control-system variables considered in this investigation included stick force per g, time constant, and dead-band, or stabilizer breakout force. In general, the fairly good correlation between flight and simulator results for two pilots demonstrates the validity of fixed-base simulator studies which are designed to complement and supplement flight studies and serve as a guide in control-system preliminary design. However, in the investigation of certain problem areas (e.g., sensitive control-system configurations associated with pilot- induced oscillations in flight), fixed-base simulator results did not predict the occurrence of an instability, although the pilots noted the system was extremely sensitive and unsatisfactory. If it is desired to predict pilot-induced-oscillation tendencies, tests in moving-base simulators may be required. It was found possible to represent the human pilot by a linear pilot analog for the tracking task assumed in the present study. The criterion used to adjust the pilot analog was the root-mean-square tracking error of one of the human pilots on the fixed-base simulator. Matching the tracking error of the pilot analog to that of the human pilot gave an approximation to the variation of human-pilot behavior over a range of control-system dynamics. Results of the pilot-analog study indicated that both for optimized control-system dynamics (for poor airplane dynamics) and for a region of good airplane dynamics, the pilot response characteristics are approximately the same.
NASA Astrophysics Data System (ADS)
Song, P.; Xiao, C.; Gu, X. H.
2011-09-01
Three energy release models of aluminized explosive with combustion effects were compared and analyzed, including Miller-Extension model, Additional energy model, Ignition and growth model (Lee-Tarver model). The Ignition and growth model is one three-form equation of reaction rate, which can describe unsteady detonation process of non-ideal explosives well. So, in this paper, the energy release model of aluminized explosive based on the Lee-Tarver rate equation was utilized and an internal-blast dynamic model of concrete was established. Moreover, the smoothed particle hydrodynamics (SPH) method was adopted to research blast field and damage effects of concrete, which widens SPH method for study on explosion of non-ideal explosive in a confined medium, and provides an important way to evaluate the damage effect of internal-blast of concrete.
Dynamic alarm response procedures
Martin, J.; Gordon, P.; Fitch, K.
2006-07-01
The Dynamic Alarm Response Procedure (DARP) system provides a robust, Web-based alternative to existing hard-copy alarm response procedures. This paperless system improves performance by eliminating time wasted looking up paper procedures by number, looking up plant process values and equipment and component status at graphical display or panels, and maintenance of the procedures. Because it is a Web-based system, it is platform independent. DARP's can be served from any Web server that supports CGI scripting, such as Apache{sup R}, IIS{sup R}, TclHTTPD, and others. DARP pages can be viewed in any Web browser that supports Javascript and Scalable Vector Graphics (SVG), such as Netscape{sup R}, Microsoft Internet Explorer{sup R}, Mozilla Firefox{sup R}, Opera{sup R}, and others. (authors)
Relations between structural and dynamic thermal characteristics of building walls
Kossecka, E.; Kosny, J.
1996-10-01
The effect of internal thermal structure on dynamic characteristics of walls is analyzed. The concept of structure factors is introduced and the conditions they impose on response factors are given. Simple examples of multilayer walls, representing different types of thermal resistance and capacity distribution, are analyzed to illustrate general relations between structure factors and response factors. The idea of the ``thermally equivalent wall``, a plane multilayer structure, with dynamic characteristics similar to those of a complex structure, in which three-dimensional heat flow occurs, is presented.
Dynamic characteristics of peripheral jet ACV. II - Pitching motion
NASA Astrophysics Data System (ADS)
Mori, T.; Maeda, H.
The dynamic pitching characteristics of peripheral jet ACV (Air Cushion Vehicle) which have a stability curtain are investigated analytically and experimentally. The measured values of moment, lift and cushion pressure are compared with numerical results noting applicability to the pitching motion. The response of ACV to the sinusoidal pitching oscillation of the ground is also studied.
Uses And Characteristics Of Dynamic Tradeoff Evaluation
NASA Technical Reports Server (NTRS)
Schwuttke, Ursula M.
1995-01-01
Report discusses basic concepts, some applications, and performance characteristics of dynamic tradeoff evaluation (DTE). Basic concepts of DTE also described in "Dynamic Restructuring of Problems in Artificial Intelligence" (NPO-18488). DTE is method of enhancing real-time performance of artificial-intelligence system such as might be used to monitor data from multiple sensors in factory, aircraft, spacecraft, or other complex system of equipment. Report presents evaluation of DTE as applied to spacecraft-monitoring problems.
Dynamic characteristics of multisensory facilitation and inhibition.
Wang, W Y; Hu, L; Valentini, E; Xie, X B; Cui, H Y; Hu, Y
2012-10-01
Multimodal integration, which mainly refers to multisensory facilitation and multisensory inhibition, is the process of merging multisensory information in the human brain. However, the neural mechanisms underlying the dynamic characteristics of multimodal integration are not fully understood. The objective of this study is to investigate the basic mechanisms of multimodal integration by assessing the intermodal influences of vision, audition, and somatosensory sensations (the influence of multisensory background events to the target event). We used a timed target detection task, and measured both behavioral and electroencephalographic responses to visual target events (green solid circle), auditory target events (2 kHz pure tone) and somatosensory target events (1.5 ± 0.1 mA square wave pulse) from 20 normal participants. There were significant differences in both behavior performance and ERP components when comparing the unimodal target stimuli with multimodal (bimodal and trimodal) target stimuli for all target groups. Significant correlation among reaction time and P3 latency was observed across all target conditions. The perceptual processing of auditory target events (A) was inhibited by the background events, while the perceptual processing of somatosensory target events (S) was facilitated by the background events. In contrast, the perceptual processing of visual target events (V) remained impervious to multisensory background events. PMID:24082962
Nonlinear Dynamic Characteristics of Oil-in-Water Emulsions
NASA Astrophysics Data System (ADS)
Yin, Zhaoqi; Han, Yunfeng; Ren, Yingyu; Yang, Qiuyi; Jin, Ningde
2016-08-01
In this article, the nonlinear dynamic characteristics of oil-in-water emulsions under the addition of surfactant were experimentally investigated. Firstly, based on the vertical upward oil-water two-phase flow experiment in 20 mm inner diameter (ID) testing pipe, dynamic response signals of oil-in-water emulsions were recorded using vertical multiple electrode array (VMEA) sensor. Afterwards, the recurrence plot (RP) algorithm and multi-scale weighted complexity entropy causality plane (MS-WCECP) were employed to analyse the nonlinear characteristics of the signals. The results show that the certainty is decreasing and the randomness is increasing with the increment of surfactant concentration. This article provides a novel method for revealing the nonlinear dynamic characteristics, complexity, and randomness of oil-in-water emulsions with experimental measurement signals.
Dynamic characteristics of magnetically-levitated vehicle systems.
Cai, Y.; Chen, S. S.; Energy Technology
1997-11-01
The dynamic response of magnetically levitated (maglev) ground transportation systems has important consequences for safety and ride quality, guideway design, and system costs. Ride quality is determined by vehicle response and by environmental factors such as humidity and noise. The dynamic response of the vehicles is the key element in determining ride quality, while vehicle stability is an important safety related element. To design a guideway that provides acceptable ride quality in the stable region, vehicle dynamics must be understood. Furthermore, the trade off between guideway smoothness and levitation and control systems must be considered if maglev systems are to be economically feasible. The link between the guideway and the other maglev components is vehicle dynamics. For a commercial maglev system, vehicle dynamics must be analyzed and tested in detail. This report, which reviews various aspects of the dynamic characteristics, experiments and analysis, and design guidelines for maglev systems, discusses vehicle stability, motion dependent magnetic force components, guideway characteristics, vehicle/ guideway interaction, ride quality, suspension control laws, aerodynamic loads and other excitations, and research needs.
A review of dynamic characteristics of magnetically levitated vehicle systems
Cai, Y.; Chen, S.S.
1995-11-01
The dynamic response of magnetically levitated (maglev) ground transportation systems has important consequences for safety and ride quality, guideway design, and system costs. Ride quality is determined by vehicle response and by environmental factors such as humidity and noise. The dynamic response of the vehicles is the key element in determining ride quality, while vehicle stability is an important safety-related element. To design a guideway that provides acceptable ride quality in the stable region, vehicle dynamics must be understood. Furthermore, the trade-off between guideway smoothness and levitation and control systems must be considered if maglev systems are to be economically feasible. The link between the guideway and the other maglev components is vehicle dynamics. For a commercial maglev system, vehicle dynamics must be analyzed and tested in detail. This report, which reviews various aspects of the dynamic characteristics, experiments and analysis, and design guidelines for maglev systems, discusses vehicle stability, motion dependent magnetic force components, guideway characteristics, vehicle/ guideway interaction, ride quality, suspension control laws, aerodynamic loads and other excitations, and research needs.
Estimations of the smoothing operator response characteristics
NASA Technical Reports Server (NTRS)
Yatskiv, Y. S.
1974-01-01
The mean response characteristic of the graphical smoothing method is discussed. The method is illustrated by analysis of latitude observations at Washington from 1915.9 to 1941.0. Spectral density, frequency distribution, and distribution functions are also discussed.
Teacher Characteristics for Culturally Responsive Pedagogy
ERIC Educational Resources Information Center
Rychly, Laura; Graves, Emily
2012-01-01
Culturally responsive pedagogy, as defined by one of the most prominent authors in the field, Geneva Gay (2002), is "using the cultural characteristics, experiences, and perspectives of ethnically diverse students as conduits for teaching them more effectively". Culturally responsive pedagogy can be thought of, then, as teaching practices that…
Dynamic response of aircraft structure
NASA Technical Reports Server (NTRS)
1975-01-01
The physical and mathematical problems associated with the response of elastic structures to random excitations such as occurs during buffeting and other transonic phenomena were discussed. The following subjects were covered: (1) general dynamic system consisting of the aircraft structure, the aerodynamic driving forces due to separated flow, and the aerodynamic forces due to aircraft structural motion, (2) structural and aerodynamic quantities of the dynamic system with special emphasis given to the description of the aerodynamic forces, and including a treatment of similarity laws, scaling effects, and wind tunnel testing, and (3) methods for data processing of fluctuating pressure recordings and techniques for response analysis for random excitation. A general buffeting flutter model, which takes into account the interactions between the separated and motion induced flows was presented. Relaxations of this model leading to the forced vibration model were explained.
Dynamic characteristics of two-phase media
Fedotovskiy, V.S.; Sinyavskiy, V.F.; Terenik, L.V.; Spirov, V.S.
1990-01-01
This paper presents the results of investigations into the effective dynamic properties of heterogeneous media formed by a liquid and rigid spherical or cylindrical inclusions contained in it. Oscillations of a pipeline with a two-phase mixture in the general case having a non-uniform distribution of phases over the cross section are considered. Relations are obtained for the effective mass and hydrodynamic damping that determine the frequencies and dynamic-response factors. Oscillations of the bundles of elastic rods in a liquid are considered as in a two-phase mixture formed by a liquid and cylindrical inclusions and which has equivalent inertia and viscous properties.
Dynamic response of cavitating turbomachines
NASA Technical Reports Server (NTRS)
Ng, S. L.
1976-01-01
Stimulated by the pogo instability encountered in many liquid propellant rockets, the dynamic behavior of cavitating inducers is discussed. An experimental facility where the upstream and downstream flows of a cavitating inducer could be perturbed was constructed and tested. The upstream and downstream pressure and mass flow fluctuations were measured. Matrices representing the transfer functions across the inducer pump were calculated from these measurements and from the hydraulic system characteristics for two impellers in various states of cavitation. The transfer matrices when plotted against the perturbing frequency showed significant departure from steady state or quasi-steady predictions especially at higher frequencies.
Dynamic and attitude control characteristics of an International Space Station
NASA Technical Reports Server (NTRS)
Sutter, Thomas R.; Cooper, Paul A.; Young, John W.; Mccutchen, Don K.
1987-01-01
The structural dynamic characteristics of the International Space Station (ISS), the interim reference configuration established for NASA's Space Station developmental program, are discussed, and a finite element model is described. Modes and frequencies of the station below 2.0 Hz are derived, and the dynamic response of the station is simulated for an external impulse load corresponding to a failed shuttle-docking maneuver. A three-axis attitude control system regulates the ISS orientation, with control moment gyros responding to attitude and attitude rate signals. No instabilities were found in the attitude control system.
The experimental investigation of bounce characteristics of ACV responsive skirt
NASA Astrophysics Data System (ADS)
Zhou, W. L.; Ma, T.
This paper presents some experimental results on the bounce characteristics of the bag-finger responsive skirt and on skirt frequency response under cushion pressure excitation obtained in a large-scale box facility. The influence of some parameters on the amplitude and frequency of the skirt bounce motion and the amplitude of the cushion pressure oscillation were explored, and the corresponding bounce boundary curves are given. Some interesting nonlinear phenomena related to the skirt instability in the time domain response are presented. The mechanism for skirt bounce and the important parameters affecting skirt dynamic stability are examined, and some means for eliminating skirt bounce are introduced.
Dynamic response of flexible retaining walls
Younan, A.H.; Veletsos, A.S.; Bandyopadhyay, K.
1997-01-01
Making use of an extension of a recently proposed, relatively simple, approximate method of analysis, a critical evaluation is made of the response to horizontal ground shaking of flexible walls retaining a uniform, linear, viscoelastic stratum of constant thickness and semiinfinite extent in the horizontal direction. Both cantilever and top-supported walls are examined. Following a detailed description of the method and of its rate of convergence, comprehensive numerical solutions are presented that elucidate the action of the system and the effects of the various parameters involved. The parameters varied include the flexibility of the wall, the condition of top support, and the characteristics of the ground motion. The effects of both harmonic base motions and an actual earthquake record are examined. Special attention is paid to the effects of long-period, effectively static excitations. A maximum dynamic response is then expressed as the product of the corresponding static response and an appropriate amplification or deamplification factor. The response quantities examined include the displacements of the wall relative to the moving base, the dynamic wall pressures, and the total wall force, base shear and base moment.
Simulated dynamic response of a servovalve controlled hydraulic actuator
NASA Technical Reports Server (NTRS)
Babcock, Dale A.
1990-01-01
A general purpose math model of a servovalve controlled hydraulic actuator system is derived. The system consists of a linear actuator with unequal piston areas, a single stage servovalve, a gas charged hydraulic accumulator, and the interconnecting piping. The state equations are integrated using the Advanced Continuous Simulation Language (ACSL) for determining the system's dynamic response characteristics. Using this generalized hydraulic actuator system model, response characteristics were determined for various servovalve commands.
NASA Technical Reports Server (NTRS)
Corliss, L. D.
1982-01-01
The helicopter configuration with an rpm-governed gas-turbine engine was examined. A wide range of engine response time, vehicle damping and sensitivity, and excess power levels was studied. The data are compared with the existing handling-qualities specifications, MIL-F-83300 and AGARD 577, and in general show a need for higher minimums when performing such NOE maneuvers as a dolphin and bob-up task.
Dynamic Characteristics of a Simple Brayton Cryocycle
NASA Astrophysics Data System (ADS)
Kutzschbach, A.; Kauschke, M.; Haberstroh, Ch.; Quack, H.
2006-04-01
The goal of the overall program is to develop a dynamic numerical model of helium refrigerators and the associated cooling systems based on commercial simulation software. The aim is to give system designers a tool to search for optimum control strategies during the construction phase of the refrigerator with the help of a plant "simulator". In a first step, a simple Brayton refrigerator has been investigated, which consists of a compressor, an after-cooler, a counter-current heat exchanger, a turboexpander and a heat source. Operating modes are "refrigeration" and "liquefaction". Whereas for the steady state design only component efficiencies are needed and mass and energy balances have to be calculated, for the dynamic calculation one needs also the thermal masses and the helium inventory. Transient mass and energy balances have to be formulated for many small elements and then solved simultaneously for all elements. Starting point of the simulation of the Brayton cycle is the steady state operation at design conditions. The response of the system to step and cyclic changes of the refrigeration or liquefaction rate are calculated and characterized.
NASA Technical Reports Server (NTRS)
Licht, L.
1970-01-01
A sixteen-inch rotor, weighing approximately twenty-one pounds, was supported by air-lubricated foil bearings. In physical size and in mass distribution, the rotor closely matched that of an experimental Brayton cycle turboalternator unit. The rotor was stable in both vertical horizontal attitudes at speeds up to 50,000 rpm. A detailed description of the experimental apparatus and of the foil bearing design are given. The paper contains data on response of the rotor to rotating imbalance, symmetric and asymmetric, and to excitation by means of a vibrator (shake table). It is concluded that the gas-lubricated foil bearing suspension is free from fractional frequency whirl and suffers no loss of load capacity when excited at frequency equal to half the rotational speed. In contrast to rigid gas bearings, the foil bearing imposes no stringent requirements with respect to dimensional tolerances, cleanliness, or limitations of journal motion within the narrow confines of bearing clearance.
Dynamic response of active twist rotor blades
NASA Astrophysics Data System (ADS)
Cesnik, Carlos E. S.; Shin, Sang Joon; Wilbur, Matthew L.
2001-02-01
Dynamic characteristics of active twist rotor (ATR) blades are investigated analytically and experimentally in this paper. The ATR system is intended for vibration and potentially for noise reductions in helicopters through individual blade control. An aeroelastic model is developed to identify frequency response characteristics of the ATR blade with integral, generally anisotropic, strain actuators embedded in its composite construction. An ATR prototype blade was designed and manufactured to experimentally study the vibration reduction capabilities of such systems. Several bench and hover tests were conducted and those results are presented and discussed here. Selected results on sensitivity of the ATR system to collective setting (i.e. blade loading), blade rpm (i.e. centrifugal force and blade station velocity), and media density (i.e. altitude) are presented. They indicated that the twist actuation authority of the ATR blade is independent of the collective setting up to approximately 10P, and dependent on rotational speed and altitude near the torsional resonance frequency due to its dependency on the aerodynamic damping. The proposed model captures very well the physics and sensitivities to selected test parameters of the ATR system. The numerical result of the blade torsional loads show an average error of 20% in magnitude and virtually no difference in phase for the blade frequency response. Overall, the active blade model is in very good agreement with the experiments and can be used to analyze and design future active helicopter blade systems.
Spectral response of multilayer optical structures to dynamic mechanical loading
NASA Astrophysics Data System (ADS)
Scripka, David; LeCroy, Garrett; Summers, Christopher J.; Thadhani, Naresh N.
2015-05-01
A computational study of Distributed Bragg Reflectors (DBR) and Optical Microcavities (OMC) was conducted to ascertain their potential as time-resolved mesoscale sensors due to their unique structure-driven spectral characteristics. Shock wave propagation simulations of polymer-based DBRs and glass/ceramic-based OMCs were coupled with spectral response calculations to demonstrate the combined dynamic mechanical and spectral response of the structures. Clear spectral shifts in both structures are predicted as a function of dynamic loading magnitude. Potential applications of the structures include high spatial and temporal resolution surface maps of material states, and in-situ probing of material interfaces during dynamic loading.
Response characteristics of selected personnel neutron dosimeters
McDonald, J.C.; Fix, J.J.; Hadley, R.T.; Holbrook, K.L.; Yoder, R.C.; Roberson, P.L.; Endres, G.W.R.; Nichols, L.L.; Schwartz, R.B.
1983-09-01
Performance characteristics of selected personnel neutron dosimeters in current use at Department of Energy (DOE) facilities were determined from their evaluation of neutron dose equivalent received after irradiations with specific neutron sources at either the National Bureau of Standards (NBS) or the Pacific Northwest Laboratory (PNL). The characteristics assessed included: lower detection level, energy response, precision and accuracy. It was found that when all of the laboratories employed a common set of calibrations, the overall accuracy was approximately +-20%, which is within uncertainty expected for these dosimeters. For doses above 80 mrem, the accuracy improved to better than 10% when a common calibration was used. Individual differences found in this study may reflect differences in calibration technique rather than differences in the dose rates of actual calibration standards. Second, at dose rates above 100 mrem, the precision for the best participants was generally below +-10% which is also within expected limits for these types of dosimeters. The poorest results had a standard deviation of about +-25%. At the lowest doses, which were sometimes below the lower detection limit, the precision often approached or exceeded +-100%. Third, the lower level of detection for free field /sup 252/Cf neutrons generally ranged between 20 and 50 mrem. Fourth, the energy dependence study provided a characterization of the response of the dosimeters to neutron energies far from the calibration energy. 11 references, 22 figures, 26 tables.
Torsional optokinetic nystagmus: normal response characteristics
Farooq, S J; Proudlock, F A; Gottlob, I
2004-01-01
Background/aims: Few studies have investigated normal response characteristics of torsional optokinetic nystagmus (tOKN). The authors have investigated the effect of stimulus velocity and central/peripheral stimulation on tOKN. Methods: Torsional OKN was elicited using a sinusoidal grating rotating at velocities of 3°/s to 1000°/s in clockwise and anticlockwise directions. To investigate the effect of central stimulation, stimulus size was varied from 2.86° to 50.8°. An artificial scotoma placed over a 50.8° stimulus was varied from 2.86° to 43.2° to investigate peripheral stimulation. Eight subjects participated in each experiment and torsional eye movements were recorded using video-oculography. The mean slow phase velocity (MSPV) and gain were calculated. Results: The maximum gain occurred in response to 8°/s stimulation. The MSPV increased up to a stimulus velocity of 200°/s achieving a maximum of 3°/s in both directions. MSPV was linearly correlated with the log of stimulus velocity. The smallest field size, rotating at 40°/s, evoked 10% of the gain elicited by the largest display. When the most peripheral stimulus was used, the gain was maintained at 50% of the gain evoked when the full display was used. Conclusions: A wide range of stimulus velocities can elicit tOKN and peripheral field stimulation contributes significantly to its response. PMID:15148215
Morphological characteristics of motile plants for dynamic motion
NASA Astrophysics Data System (ADS)
Song, Kahye; Yeom, Eunseop; Kim, Kiwoong; Lee, Sang Joon
2014-11-01
Most plants have been considered as non-motile organisms. However, plants move in response to environmental changes for survival. In addition, some species drive dynamic motions in a short period of time. Mimosa pudica is a plant that rapidly shrinks its body in response to external stimuli. It has specialized organs that are omnidirectionally activated due to morphological features. In addition, scales of pinecone open or close up depending on humidity for efficient seed release. A number of previous studies on the dynamic motion of plants have been investigated in a biochemical point of view. In this study, the morphological characteristics of those motile organs were investigated by using X-ray CT and micro-imaging techniques. The results show that the dynamic motions of motile plants are supported by structural features related with water transport. These studies would provide new insight for better understanding the moving mechanism of motile plant in morphological point of view. This research was financially supported by the Creative Research Initiative of the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of Korea (Grant Number: 2008-0061991).
Dynamic characteristics of peripheral jet ACV. III - Coupling motion of heaving and pitching
NASA Astrophysics Data System (ADS)
Mori, T.; Maeda, H.
The paper presents the dynamic characteristics of peripheral jet ACV (Air Cushion Vehicle) which has two degrees of freedom, i.e., heaving and pitching motion. The experiments are carried out for an ACV model, noting that the experimental results agree considerably with the analytical values. Furthermore, the response characteristics of ACV induced by the ground board oscillations of various modes are also investigated.
Landscape response to changes in dynamic topography
NASA Astrophysics Data System (ADS)
Ruetenik, Gregory A.; Moucha, Robert; Hoke, Gregory D.
2015-04-01
Dynamic topography is characterized by broad wavelength, low amplitude undulations of the Earth's surface maintained by stresses arising from mantle convection. Earth's topography is thus an aggregate of both dynamic and isostatic topography that is modulated by surface processes and changes in topography and/or the climate can be recorded in the offshore sedimentary record. However, it is generally difficult to deconvolve this record into contributions from changes in climate, isostatic topography, and dynamic topography. Herein, we use a landscape evolution model that is capable of producing simulations at the necessary scale and resolution for quantifying landscape response to moderate changes in dynamic topography in the presence of flexural unloading and loading due to erosion and deposition. We demonstrate that moderate changes in dynamic topography coupled with flexural response imposed on a landscape with pre-existing relief and drainage divide, disequilibrates the landscape resulting in a measurable increase in erosion rates and corresponding sedimentary flux to the margin. The magnitude and timing of this erosional response to dynamic topography is dependent on several key landscape evolution parameters, most notably the erosion (advection) coefficient and effective elastic thickness. Moreover, to maximize this response, we find that changes in dynamic topography must be slow enough and long-lived for given rates of erosion otherwise the landscape will not have sufficient time to generate a response. Lastly, this anomalous flux can persist for a significant amount of time beyond the influence of dynamic topography change as the landscape strives to re-equilibrate.
Simulation and Experimental Investigation of Structural Dynamic Frequency Characteristics Control
Zhang, Xingwu; Chen, Xuefeng; You, Shangqin; He, Zhengjia; Li, Bing
2012-01-01
In general, mechanical equipment such as cars, airplanes, and machine tools all operate with constant frequency characteristics. These constant working characteristics should be controlled if the dynamic performance of the equipment demands improvement or the dynamic characteristics is intended to change with different working conditions. Active control is a stable and beneficial method for this, but current active control methods mainly focus on vibration control for reducing the vibration amplitudes in the time domain or frequency domain. In this paper, a new method of dynamic frequency characteristics active control (DFCAC) is presented for a flat plate, which can not only accomplish vibration control but also arbitrarily change the dynamic characteristics of the equipment. The proposed DFCAC algorithm is based on a neural network including two parts of the identification implement and the controller. The effectiveness of the DFCAC method is verified by several simulation and experiments, which provide desirable results. PMID:22666072
Dynamic electrical response of solar cells
NASA Technical Reports Server (NTRS)
Catani, J. P.
1981-01-01
The dynamic response of a solar generator is of primary importance as much for the design and development of electrical power conditioning hardware as for the analysis of electromagnetic compatibility. A mathematical model of photo-batteries was developed on the basis of impedance measurements performed under differing conditions of temperature, light intensity, before and after irradiation. This model was compared with that derived from PN junction theory and to static measurements. These dynamic measurements enabled the refinement of an integration method capable of determining, under normal laboratory conditions, the dynamic response of a generator to operational lighting conditions.
Numerical investigation of bubble nonlinear dynamics characteristics
Shi, Jie Yang, Desen; Shi, Shengguo; Hu, Bo; Zhang, Haoyang; Jiang, Wei
2015-10-28
The complicated dynamical behaviors of bubble oscillation driven by acoustic wave can provide favorable conditions for many engineering applications. On the basis of Keller-Miksis model, the influences of control parameters, including acoustic frequency, acoustic pressure and radius of gas bubble, are discussed by utilizing various numerical analysis methods, Furthermore, the law of power spectral variation is studied. It is shown that the complicated dynamic behaviors of bubble oscillation driven by acoustic wave, such as bifurcation and chaos, further the stimulated scattering processes are revealed.
Numerical investigation of bubble nonlinear dynamics characteristics
NASA Astrophysics Data System (ADS)
Shi, Jie; Yang, Desen; Zhang, Haoyang; Shi, Shengguo; Jiang, Wei; Hu, Bo
2015-10-01
The complicated dynamical behaviors of bubble oscillation driven by acoustic wave can provide favorable conditions for many engineering applications. On the basis of Keller-Miksis model, the influences of control parameters, including acoustic frequency, acoustic pressure and radius of gas bubble, are discussed by utilizing various numerical analysis methods, Furthermore, the law of power spectral variation is studied. It is shown that the complicated dynamic behaviors of bubble oscillation driven by acoustic wave, such as bifurcation and chaos, further the stimulated scattering processes are revealed.
Dynamic characteristics and seismic stability of expanded polystyrene geofoam embankments
NASA Astrophysics Data System (ADS)
Amini, Zahra A.
Expanded Polystyrene (EPS) geofoam has become a preferred material in various construction applications due to its light weight. Application of EPS accelerates the projects particularly on soft soils. The focus of this research is on the application of the EPS in embankments and its behavior mainly under harmonic vibration. The goal of this study was to investigate dynamic characteristics of freestanding vertical EPS geofoam embankment and address potential seismic issues that result from the distinguished dynamic behavior of such systems due to the layered and discrete block structure. A series of experimental studies on EPS 19 and a commercially available adhesive was conducted. Two-dimensional numerical analyses were performed to replicate the response of EPS geofoam embankment to horizontal and vertical harmonic motions. The results of the analyses have shown that for some acceleration amplitude levels interlayer sliding is expected to occur in EPS geofoam embankments almost immediately after the start of the base excitation; however, as a highly efficient energy dissipation mechanism sliding ceases rapidly. Shear keys and adhesive may be used to prevent interlayer sliding if they cover the proper extent of area of the embankment. EPS blocks placed in the corners of the embankment and at the edges of the segment prohibited from sliding may experience high stress concentrations. The embankment may show horizontal sway and rocking once sliding is prevented.
Dynamic Response Testing in an Electrically Heated Reactor Test Facility
NASA Technical Reports Server (NTRS)
Bragg-Sitton, Shannon M.; Morton, T. J.
2006-01-01
Non-nuclear testing can be a valuable tool in development of a space nuclear power or propulsion system. In a non-nuclear test bed, electric heaters are used to simulate the heat from nuclear fuel. Standard testing allows one to fully assess thermal, heat transfer, and stress related attributes of a given system, but fails to demonstrate the dynamic response that would be present in an integrated, fueled reactor system. The integration of thermal hydraulic hardware tests with simulated neutronic response provides a bridge between electrically heated testing and full nuclear testing. By implementing a neutronic response model to simulate the dynamic response that would be expected in a fueled reactor system, one can better understand system integration issues, characterize integrated system response times and response characteristics, and assess potential design improvements at a relatively small fiscal investment. Initial system dynamic response testing was demonstrated on the integrated SAFE-100a heat pipe cooled, electrically heated reactor and heat exchanger hardware, utilizing a one-group solution to the point kinetics equations to simulate the expected neutronic response of the system (Bragg-Sitton, 2005). The current paper applies the same testing methodology to a direct drive gas cooled reactor system, demonstrating the applicability of the testing methodology to any reactor type and demonstrating the variation in system response characteristics in different reactor concepts. In each testing application, core power transients were controlled by a point kinetics model with reactivity feedback based on core average temperature; the neutron generation time and the temperature feedback coefficient are provided as model inputs. Although both system designs utilize a fast spectrum reactor, the method of cooling the reactor differs significantly, leading to a variable system response that can be demonstrated and assessed in a non-nuclear test facility.
Spatiotemporal characteristics of calcium dynamics in astrocytes
NASA Astrophysics Data System (ADS)
Kang, Minchul; Othmer, Hans G.
2009-09-01
Although Cai2+ waves in networks of astrocytes in vivo are well documented, propagation in vivo is much more complex than in culture, and there is no consensus concerning the dominant roles of intercellular and extracellular messengers [inositol 1,4,5-trisphosphate (IP3) and adenosine-5'-triphosphate (ATP)] that mediate Cai2+ waves. Moreover, to date only simplified models that take very little account of the geometrical struture of the networks have been studied. Our aim in this paper is to develop a mathematical model based on realistic cellular morphology and network connectivity, and a computational framework for simulating the model, in order to address these issues. In the model, Cai2+ wave propagation through a network of astrocytes is driven by IP3 diffusion between cells and ATP transport in the extracellular space. Numerical simulations of the model show that different kinetic and geometric assumptions give rise to differences in Cai2+ wave propagation patterns, as characterized by the velocity, propagation distance, time delay in propagation from one cell to another, and the evolution of Ca2+ response patterns. The temporal Cai2+ response patterns in cells are different from one cell to another, and the Cai2+ response patterns evolve from one type to another as a Cai2+ wave propagates. In addition, the spatial patterns of Cai2+ wave propagation depend on whether IP3, ATP, or both are mediating messengers. Finally, two different geometries that reflect the in vivo and in vitro configuration of astrocytic networks also yield distinct intracellular and extracellular kinetic patterns. The simulation results as well as the linear stability analysis of the model lead to the conclusion that Cai2+ waves in astrocyte networks are probably mediated by both intercellular IP3 transport and nonregenerative (only the glutamate-stimulated cell releases ATP) or partially regenerative extracellular ATP signaling.
Celebi, Mehmet; Huang, Moh; Shakal, Antony; Hooper, John; Klemencic, Ron
2012-01-01
A 64-story, performance-based design building with reinforced concrete core shear-walls and unique dynamic response modification features (tuned liquid sloshing dampers and buckling-restrained braces) has been instrumented with a monitoring array of 72 channels of accelerometers. Ambient vibration data recorded are analyzed to identify modes and associated frequencies and damping. The low-amplitude dynamic characteristics are considerably different than those computed from design analyses, but serve as a baseline against which to compare with future strong shaking responses. Such studies help to improve our understanding of the effectiveness of the added features to the building and help improve designs in the future.
Finite element simulation of pipe dynamic response
Slagis, G.C.; Litton, R.W.
1996-12-01
Nonlinear finite element dynamic analyses of the response of a pipe span to controlled-displacement, sinusoidal vibration have been performed. The objective of this preliminary study is to compare strain and acceleration response data to those generated by Beaney in the Berkeley Nuclear Laboratories experiments. Results for an unpressurized, 5 Hz, carbon steel pipe are in good agreement with the experiments. Hence, it appears that analytical simulation will be useful to assess seismic margins. Recommendations for additional studies are provided. The analyses confirm the test results--dynamic response is greatly attenuated by material plasticity. Analytical strains and accelerations are about 30% higher than test data. There are several possible explanations for the differences. To assess the effect of frequency on response, the length of the pipe span was increased. Analysis of the longer, 2 Hz, pipe span shows significantly greater cyclic strains than the 5 Hz span at the same input excitation levels.
Dynamic Response Testing in an Electrically Heated Reactor Test Facility
NASA Astrophysics Data System (ADS)
Bragg-Sitton, Shannon M.; Morton, T. J.
2006-01-01
Non-nuclear testing can be a valuable tool in the development of a space nuclear power or propulsion system. In a non-nuclear test bed, electric heaters are used to simulate the heat from nuclear fuel. Standard testing allows one to fully assess thermal, heat transfer, and stress related attributes of a given system, but fails to demonstrate the dynamic response that would be present in an integrated, fueled reactor system. The integration of thermal hydraulic hardware tests with simulated neutronic response provides a bridge between electrically heated testing and fueled nuclear testing. By implementing a neutronic response model to simulate the dynamic response that would be expected in a fueled reactor system, one can better understand system integration issues, characterize integrated system response times and response characteristics, and assess potential design improvements at a relatively small fiscal investment. Initial system dynamic response testing was demonstrated on the integrated SAFE-100a heat pipe (HP) cooled, electrically heated reactor and heat exchanger hardware, utilizing a one-group solution to the point kinetics equations to simulate the expected neutronic response of the system. Reactivity feedback calculations were then based on a bulk reactivity feedback coefficient and measured average core temperature. This paper presents preliminary results from similar dynamic testing of a direct drive gas cooled reactor system (DDG), demonstrating the applicability of the testing methodology to any reactor type and demonstrating the variation in system response characteristics in different reactor concepts. Although the HP and DDG designs both utilize a fast spectrum reactor, the method of cooling the reactor differs significantly, leading to a variable system response that can be demonstrated and assessed in a non-nuclear test facility. Planned system upgrades to allow implementation of higher fidelity dynamic testing are also discussed. Proposed DDG
Effective reconstruction of dynamics of medium response spectrum
NASA Astrophysics Data System (ADS)
Trofimov, Vyacheslav A.; Varentsova, Svetlana A.
2008-10-01
A new algorithm is suggested to visualize the dynamics of medium response spectrum in terahertz diapason by the singly measured set of partially intersected integral characteristics of the signal. The algorithm is based on SVD method and window sliding method. The analysis, we carried out, demonstrates many advantages of the new algorithm in com-parison with the Gabor-Fourier approach, which allows obtaining the dynamics of only one spectral line for one set of measurements. Among which it is necessary to mention the possibility to get the dynamics of many spectral components simultaneously for one set of measurements as well and therefore to get the complete information about the spectrum dynamics. This allows to identify specific materials with known spectral lines and to distinguish materials with similar spectra, which is of great importance for the detection and identification of different chemicals, pharmaceutical substances and explosives. To demonstrate the efficiency of a proposed algorithm, we compare spectrum dynamics of chocolate and soap, which possess the similar spectra. Our investigation shows that their dynamics widely vary in spec-tral lines. The proposed algorithm can be also applied to voice identification and to reconstruction of a laser beam profile with a great number of local maxima. Developed algorithm allows to measure the characteristic time of medium responce. It is very important for various problems of spectroscopy.
Dynamic-tensile-extrusion response of fluoropolymers
Brown, Eric N; Trujillo, Carl P; Gray, George T
2009-01-01
The current work applies the recently developed Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) technique to polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE). Similar to the Taylor Impact Rod, Dynamic-Tensile-Extrusion is a strongly integrated test, probing a wide range of strain rates and stress states. However, the stress state is primarily tensile enabling investigation of dynamic tensile failure modes. Here we investigate the influence of this propensity to neck or not between PCTFE and PTFE on their response under dynamic tensile extrusion loading. The results of the Dyn-Ten-Ext technique are compared with two classic techniques. Both polymers have been investigated using Tensile Split Hopkinson Pressure Bar. The quasistatic and dynamic responses of both fluoro-polymers have been extensively characterized. The two polymers exhibit significantly different failure behavior under tensile loading at moderate strain rates. Polytetrafluoroethylene resists formation of a neck and exhibits significant strain hardening. Independent of temperature or strain rate, PTFE sustains true strains to failure of approximately 1.5. Polychlorotrifluoroethylene, on the other hand, consistently necks at true strains of approximately 0.05.
Dynamic response of tunnels in jointed rocks
Heuze, F.E.; Shaffer, R.J.; Walton, O.R.; Maddix, D.M.
1993-09-01
The current proposed site for an underground nuclear waste repository is at Yucca Mountain, Nevada. The host rock is a jointed tuff. The question is: how will the repository behave under strong earthquake motion. The basic requirement for analysis is an ability to follow the dynamic motion of a multiplicity of discrete particles, i.e., rock blocks separated by joints and faults. The authors describe the application of the discrete element method (DEM) to the dynamic analysis of the response of tunnels in jointed rocks to earthquake loading. In situations where large motions of many blocks and collapse occur, the discontinuum-based DEM approach appears superior to other methods of analysis.
Dynamics and control characteristics of a reference Space Station configuration
NASA Technical Reports Server (NTRS)
Sutter, Thomas R.; Cooper, Paul A.; Young, John W.
1988-01-01
This paper describes the structural dynamic characteristics of a NASA reference space station configuration as defined in the November 1987 Space Station Program - Systems Engineering and Integration Engineering Data Book. The modes and frequencies of the station below 2.0 Hz were obtained and selected results along with rigid body properties are presented. A three-axis attitude control system using control moment gyros responding to attitude and attitude rate signals is used to regulate the orientation of the station. The stability of the control system with non-collocated sensors is investigated for both compensated and uncompensated control signals. Results from a closed-loop simulation of a commanded attitude change about three axes, and from a closed-loop simulation of the response of the station to an externally applied unit force impulse at the docking port are presented. These simulation results are used to evaluate the possible degree of control/structures interaction which could occur during normal operation of the station.
Spectral characteristics of ventricular response to atrial fibrillation.
Hayano, J; Yamasaki, F; Sakata, S; Okada, A; Mukai, S; Fujinami, T
1997-12-01
To investigate the spectral characteristics of the fluctuation in ventricular response during atrial fibrillation (AF), R-R interval time series obtained from ambulatory electrocardiograms were analyzed in 45 patients with chronic AF and in 30 age-matched healthy subjects with normal sinus rhythm (SR). Although the 24-h R-R interval spectrum during SR showed a 1/f noise-like downsloping linear pattern when plotted as log power against log frequency, the spectrum during AF showed an angular shape with a breakpoint at a frequency of 0.005 +/- 0.002 Hz, by which the spectrum was separated into long-term and short-term components with different spectral characteristics. The short-term component showed a white noise-like flat spectrum with a spectral exponent (absolute value of the regression slope) of 0.05 +/- 0.08 and an intercept at 10(-2) Hz of 4.9 +/- 0.3 log(ms2/Hz). The long-term component had a 1/f noise-like spectrum with a spectral exponent of 1.26 +/- 0.40 and an intercept at 10(-4) Hz of 7.0 +/- 0.3 log(ms2/Hz), which did not differ significantly from those for the spectrum during SR in the same frequency range [spectral exponent, 1.36 +/- 0.06; intercept at 10(-4) Hz, 7.1 +/- 0.3 log(ms2/Hz)]. The R-R intervals during AF may be a sequence of uncorrelated values over the short term (within several minutes). Over the longer term, however, the R-R interval fluctuation shows the long-range negative correlation suggestive of underlying regulatory processes, and spectral characteristics indistinguishable from those for SR suggest that the long-term fluctuations during AF and SR may originate from similar dynamics of the cardiovascular regulatory systems. PMID:9435618
Solar dynamic heat receiver thermal characteristics in low earth orbit
NASA Technical Reports Server (NTRS)
Wu, Y. C.; Roschke, E. J.; Birur, G. C.
1988-01-01
A simplified system model is under development for evaluating the thermal characteristics and thermal performance of a solar dynamic spacecraft energy system's heat receiver. Results based on baseline orbit, power system configuration, and operational conditions, are generated for three basic receiver concepts and three concentrator surface slope errors. Receiver thermal characteristics and thermal behavior in LEO conditions are presented. The configuration in which heat is directly transferred to the working fluid is noted to generate the best system and thermal characteristics. as well as the lowest performance degradation with increasing slope error.
Dynamic response of a single flexible cylinder in waves
Duggal, A.S.; Niedzwecki, J.M.
1995-05-01
A large-scale experimental study to investigate the dynamic response of a single flexible cylinder in waves is presented. The cylinder was designed to exhibit the dynamic characteristics of a TLP riser or tendon in approximately 1,000 m of water. Instrumentation provided detailed information on the inline and transverse curvature along the length of the cylinder. Wave loading mechanisms and the resulting response were investigated and compared with previous studies of rigid cylinders in oscillating flow. It was found that the complicated multifrequency response at large Keulegan-Carpenter numbers could be explained by introducing the depth dependence of the Keulegan-Carpenter number. The predicted inline response was shown to be reasonable for the wave frequency component of the measured inline response. Similarities between the measured transverse response and the high-frequency inline response were also shown. Probability density functions of the measured curvature were non-Gaussian, leading to significantly higher probabilities of curvature than would be predicted based on assuming a Gaussian process.
A study on the dynamic characteristics of rocket structure
NASA Astrophysics Data System (ADS)
Kim, K. O.; Lee, J. M.; Kim, J. H.; Kim, S. J.
The dynamic characteristics of a rocket structure are studied in various aspects. Modeling of the structure used by the finite element method is performed, and analysis of stress under various loading condition is carried out. In particular, stresses and deflections are investigated for the structure subjected to internal pressure, thermal load, and aerodynamic forces during flight. Natural frequencies and mode shapes are also calculated.
Flow characteristics of the dynamic "EPA flux chamber"
Technology Transfer Automated Retrieval System (TEKTRAN)
A dynamic flux chamber, commonly referred as the “EPA chamber”, is one method that has been adapted to investigate spatial gas emission on feedlot surfaces. However, the flow characteristics within the chamber have not been evaluated to determine if it can be effectively used outside of its origina...
Design of helicopter rotor blades for optimum dynamic characteristics
NASA Technical Reports Server (NTRS)
Peters, D. A.; Ko, T.; Korn, A.; Rossow, M. P.
1985-01-01
The mass and stiffness distributions for helicopter rotor blades are tailored in such a way to give a predetermined placement of blade natural frequencies. The optimal design is pursued with respect of minimum weight, sufficient inertia, and reasonable dynamic characteristics. Finite element techniques are used as a tool. Rotor types include hingeless, articulated, and teetering.
Dynamical plasma response during driven magnetic reconnection.
Egedal, J; Fasoli, A; Nazemi, J
2003-04-01
Direct measurements of a collisionless current channel during driven magnetic reconnection are obtained for the first time on the Versatile Toroidal Facility. The size of the diffusion region is found to scale with the electron drift orbit width, independent of the ion mass and plasma density. Based on experimental observations, analytic expressions governing the dynamical evolution of the current profile and the formation of the electrostatic potential that develops in response to the externally imposed reconnection drive are established. This time response is closely linked to the presence of ion polarization currents. PMID:12689297
Rapid Cellular Identification by Dynamic Electromechanical Response
Nikiforov, Maxim; Jesse, Stephen; Kalinin, Sergei V; Reukov, Vladimir V; Vertegel, Alexey; Thompson, Gary L
2009-01-01
Coupling between electrical and mechanical phenomena is ubiquitous in living systems. Here, we demonstrate rapid identification of cellular organisms using difference in electromechanical activity in a broad frequency range. Principal component analysis of the dynamic electromechanical response spectra bundled with neural network based recognition provides a robust identification algorithm based on their electromechanical signature, and allows unambiguous differentiation of model Micrococcus Lysodeikticus and Pseudomonas Fluorescens system. This methodology provides a universal pathway for biological identification obviating the need for well-defined analytical models of Scanning Probe Microscopy response.
Dynamic response to rotating-seat runout in non-contacting face seals
NASA Technical Reports Server (NTRS)
Etsion, I.
1980-01-01
The dynamic response of a flexibly mounted ring to runout of the rotating seat in mechanical face seals is analyzed assuming small perturbations. It is found that tracking ability of the stator depends only on its dynamic characteristics and operating conditions and is not affected by the amount of runout. Three different modes of dynamic response are shown and the condition for parallel tracking is presented.
Psychosocial Characteristics Mediating the Response: An Exploratory Study.
ERIC Educational Resources Information Center
Witmer, J. Melvin; And Others
1983-01-01
Examined the psychosocial characteristics that cognitively mediate between life stressors and the stress response in 235 subjects. Results from the five instruments used showed self-esteem was by far the most important characteristic discriminating between good and poor copers. Other factors were external control, life pace and irrational beliefs.…
Energy deposition and dynamic response of materials
NASA Astrophysics Data System (ADS)
Perry, Frank C.
1993-07-01
We are exploring new applications of the technology of energy deposition and dynamic response. Early studies involved analytical solutions of the coupled thermal and elastic response of materials to pulsed energy deposition. Experiments designed to test the theory led to determinations of thermal pressure coefficients for a variety of materials and an understanding of the effects of the time dependence of the energy source on dynamic response. Subsequent experiments at higher deposited energies required analysis by an energy deposition-wave propagation code to explain the observed elastic-plastic behavior. Instrumentation included laser interferometry and holographic interferometry for multi- dimensional response. A possible application of this technology to Biomedical Science is a technique to measure ion transport in biological material. It requires a combination of holographic interferometry and spectroscopy, namely, Resonant Holographic Interferometry Spectroscopy (RHIS). The technique involves the absorption and refraction of light near absorption lines. Stress waves arising from the absorbed light can be assessed with the energy deposition-wave propagation code. Such calculations will require the inclusion of appropriate biomaterial properties.
Numerical and Experimental Dynamic Characteristics of Thin-Film Membranes
NASA Technical Reports Server (NTRS)
Young, Leyland G.; Ramanathan, Suresh; Hu, Jia-Zhu; Pai, P. Frank
2004-01-01
Presented is a total-Lagrangian displacement-based non-linear finite-element model of thin-film membranes for static and dynamic large-displacement analyses. The membrane theory fully accounts for geometric non-linearities. Fully non-linear static analysis followed by linear modal analysis is performed for an inflated circular cylindrical Kapton membrane tube under different pressures, and for a rectangular membrane under different tension loads at four comers. Finite element results show that shell modes dominate the dynamics of the inflated tube when the inflation pressure is low, and that vibration modes localized along four edges dominate the dynamics of the rectangular membrane. Numerical dynamic characteristics of the two membrane structures were experimentally verified using a Polytec PI PSV-200 scanning laser vibrometer and an EAGLE-500 8-camera motion analysis system.
Dynamic energy absorption characteristics of hollow microlattice structures
Liu, YL; Schaedler, TA; Chen, X
2014-10-01
Hollow microlattice structures are promising candidates for advanced energy absorption and their characteristics under dynamic crushing are explored. The energy absorption can be significantly enhanced by inertial stabilization, shock wave effect and strain rate hardening effect. In this paper we combine theoretical analysis and comprehensive finite element method simulation to decouple the three effects, and then obtain a simple model to predict the overall dynamic effects of hollow microlattice structures. Inertial stabilization originates from the suppression of sudden crushing of the microlattice and its contribution scales with the crushing speed, v. Shock wave effect comes from the discontinuity across the plastic shock wave front during dynamic loading and its contribution scales with e. The strain rate effect increases the effective yield strength upon dynamic deformation and increases the energy absorption density. A mechanism map is established that illustrates the dominance of these three dynamic effects at a range of crushing speeds. Compared with quasi-static loading, the energy absorption capacity a dynamic loading of 250 m/s can be enhanced by an order of magnitude. The study may shed useful insight on designing and optimizing the energy absorption performance of hollow microlattice structures under various dynamic loads. (C) 2014 Elsevier Ltd. All rights reserved.
G-seat system step input and sinusoidal response characteristics
NASA Technical Reports Server (NTRS)
Showalter, T. W.; Miller, R. J.
1978-01-01
The step input and sinusoidal response characteristics of a pneumatically driven computer controlled G set are examined in this study. The response data show that this system can be modeled as a first order system with an 0.08 sec time lag and a 0.53 sec time constant.
The dynamic inelastic response of delaminated plates
Addessio, F.L.; Williams, T.O.
1996-12-01
A generalized theory for laminated plates with delaminations is used to consider the influence of inelastic deformations on the dynamic behavior of composite plates with delaminations. The laminate model is based on a generalized displacement formulation implemented at the layer level. The delamination behavior can be modeled using any general interfacial fracture law: however, for the current work a linear model is employed. The interfacial displacement jumps are expressed in an internally consistent fashion in terms of the fundamental unknown interfacial tractions. The current theory imposes no restrictions on the size, location, distribution, or direction of growth of the delaminations. The proposed theory is used to consider the inelastic, dynamic response of delaminated plates in cylindrical bending subjected to a ramp and hold type of loading. The individual layers in the current study are assumed to be either titanium or aluminum. The inelastic response of both materials is modeled using the unified viscoplastic theory of Bodner and Partom. It is shown that the presence of both inelastic behavior and delamination can have a significant influence on the plate response. In particular it is shown that these mechanisms are strongly interactive. This result emphasizes the need to consider both mechanisms simultaneously.
Simulating the dynamic response of magnesium alloys
NASA Astrophysics Data System (ADS)
Lloyd, Jeffrey; Becker, Richard
Unlike several conventional metals, the mechanical response of magnesium is severely anisotropic for quasistatic and dynamic loading conditions. In this work we present a crystal-based strength model that is the same order of magnitude in computational cost as rate-dependent isotropic strength models, yet is able to capture essential features exhibited by textured magnesium polycrystals. The model demarcates plastic deformation into contributions from basal slip, extension twinning, and non-basal slip mechanisms. Comparisons are made between model predictions and experiments for two magnesium alloys with differing processing histories. The model is then used to explore and quantify the dependence of metallurgical and processing variations for several dynamic experiments that probe propensity for localization and failure under complex loading conditions.
NASA Astrophysics Data System (ADS)
Noroozi, S.; Rahman, A. G. A.; Dupac, M.; Vinney, J. E.
Current methods of evaluating the performance of Energy Storing and Returning (ESR) prosthesis are subjective and rely on VO2 consumption. Current prosthetic feet are designed for specific applications and the majority are designed for walking and moderate running. These mechanical feet have fixed mechanical and dynamic characteristics. They have to be selected to meet the requirement of the task and any use outside the domain of the task can result in extreme/severe lack of gait symmetry and loss of energy. Poor gait symmetry results is excess consumption of energy, back pain or fatigue. To investigate if a multipurpose foot can be designed to passively adapt to the walking or running condition one must first understand the different dynamics that are involved and are required from the task specific foot. Static tests have shown these feet to have non-linear stiffness, making the prediction of their dynamic response difficult. The most reliable method to test for dynamic characteristics is drop and modal testing. A method approach has been developed as part of this research to test and compare the dynamic characteristics of three different types of foot (natural frequency, mode shapes and damping). This is needed to explore the differences in the responses of these feet that allow one to be used for walking, one to be used for running and one to be used for sprinting with ease.
Signature of ergodicity in the dynamic response of amorphous systems
Chamberlin, R.V. ); Boehmer, R.; Sanchez, E.; Angell, C.A. )
1992-09-01
We have analyzed dynamical measurements from materials near their liquid-glass transition. The primary response is accurately characterized by a model for dispersive excitations on specific distributions of independently relaxing domains. Liquids have an equilibrium (Gaussian) distribution of domain sizes, which changes abruptly to a locally random (Poisson-like) distribution in the glass. When quenched to a temperature initially in the glass phase, after a definite anneal time, the Poisson-like distribution changes abruptly back to the Gaussian distribution characteristic of a liquid.
Study on Dynamic Characteristics of Ammonia Refrigerator System
NASA Astrophysics Data System (ADS)
Nakashima, Minoru; Ikegami, Yasuyuki; Hirao, Yasuhiro; Sudoh, Gaku; Shingoh, Masashi; Uehara, Haruo
The dynamic characteristics of ammonia refrigerator system are observed when the expansion valve's opening is slightly changed. The refrigerator system is constructed with the reciprocal compressor, the plate type heat exchanger for the condenser and the evaporator, and the expansion valve. A simple simulation model for this refrigerator system is proposed to develop the computer-simulator of this ammonia refrigerator system and those simulation results are compared to above experimental results. For the development of the computer-simulator, simple but useful models, which can represent the dynamic characteristics of the refrigerator, are adopted for each components of the refrigerator system. The simulation shows the overall good agreement with experiment, without the time constant in the variation of the temperature at the evaporator outlet.
Electromagnetic Elasto-Plastic Dynamic Response of Conductive Plate
NASA Astrophysics Data System (ADS)
Gao, Yuanwen
2010-05-01
Electromagnetic elasto-plastic dynamic response of a conductive plate in a magnetic pulse field are studied in this paper, the influence of the strain rate effect is investigated for the electromagnetic elasto-plastic deformation of the conductive plate. Basic governing equations are derived for electromagnetic field (eddy current), the elasto-plastic transient dynamic response and the heat transfer of a conductive rectangular plate, and then an appropriate numerical code is developed based on the finite element method to quantitatively simulate the magneto-elasto-plastic mechanical behaviors of the conductive rectangular plate. The Johnson-Cook model is employed to study the strain rate effect and temperature effect on the deformation of the plate. The dynamic response is explained with some characteristic curves of deformation, the eddy current, and the configurations, the temperature of the conductive plate. The numerical results indicate that the strain rate effect has to be considered for the conductive plates, especially for those with high strain rate sensitivity. Comparison of the influence of the temperature effect on the deformation of the plate with that of the strain rate effect shows that the influence of the temperature effect on the deformation of a plate is not significant.
Comparisons of the dynamic characteristics of magnetorheological and hydraulic dampers
NASA Astrophysics Data System (ADS)
Zhang, Yi; Oyadiji, S. O.
2015-04-01
A magnetorheological (MR) damper can adapt its dynamic performance to the vibration environment by controlling the current applied. Compared to other types of dampers, the MR damper has a wider range of dynamic characteristics. Two different dampers: hydraulic, and MR dampers were tested under forced sinusoidal excitations of low to high frequencies. Also, different currents were applied on the MR damper to investigate its performance under varying electromagnetic fields. The results reveal that the two dampers have nonlinear dynamic characteristics and that characteristics of the hydraulic damper are different from those of the MR damper. The hydraulic damper provides slight nonlinear damping force whereas the MR damper shows a strong nonlinear property. In addition, the hydraulic damper is designed to provide an asymmetric damping force of rebound and compression whereas the MR damper provides a symmetric damping force. In the experiments conducted, the excitation frequency was varied from 3 Hz to 11 Hz and the amplitude from 2.5 mm to 12 mm. For the hydraulic damper, the lowest compression damping force only increases by about 0.54 kN while the rebound force increases by about 1.9 kN. In contrast, the variations of compression and rebound forces of the MR damper are 1.9 and 2.0 kN, respectively. Furthermore, the damping force of the MR damper increases as the current increases from 0 to 0.75 A.
Evaluating the Dynamic Characteristics of Retrofitted RC Beams
NASA Astrophysics Data System (ADS)
Ghods, Amir S.; Esfahani, Mohamad R.; Moghaddasie, Behrang
2008-07-01
The aim of this experimental study was to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete members strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of 8 reinforced concrete beams with similar dimensions were made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading was applied with four-point-bending setup in order to generate different damage levels in the specimens while dynamic testing was conducted to monitor the changes in dynamic characteristics of the specimens. In order to investigate the effect of CFRP on static and dynamic properties of specimens, some of the beams were loaded to half of their ultimate load carrying capacity and then were retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrated elevated load carrying capacity, higher flexural stiffness and lower displacement ductility. By increasing the damage level in specimens, frequencies of the beams were decreased and after strengthening these values were improved significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to move toward the location of the damage in each case.
Evaluating the Dynamic Characteristics of Retrofitted RC Beams
Ghods, Amir S.; Esfahani, Mohamad R.; Moghaddasie, Behrang
2008-07-08
The aim of this experimental study was to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete members strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of 8 reinforced concrete beams with similar dimensions were made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading was applied with four-point-bending setup in order to generate different damage levels in the specimens while dynamic testing was conducted to monitor the changes in dynamic characteristics of the specimens. In order to investigate the effect of CFRP on static and dynamic properties of specimens, some of the beams were loaded to half of their ultimate load carrying capacity and then were retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrated elevated load carrying capacity, higher flexural stiffness and lower displacement ductility. By increasing the damage level in specimens, frequencies of the beams were decreased and after strengthening these values were improved significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to move toward the location of the damage in each case.
Dynamics of active cellular response under stress
NASA Astrophysics Data System (ADS)
de, Rumi; Zemel, Assaf; Safran, Samuel
2008-03-01
Forces exerted by and on adherent cells are important for many physiological processes such as wound healing and tissue formation. In addition, recent experiments have shown that stem cell differentiation is controlled, at least in part, by the elasticity of the surrounding matrix. Using a simple theoretical model that includes the forces due to both the mechanosensitive nature of cells and the elastic response of the matrix, we predict the dynamics of orientation of cells. The model predicts many features observed in measurements of cellular forces and orientation including the increase with time of the forces generated by cells in the absence of applied stress and the consequent decrease of the force in the presence of quasi-static stresses. We also explain the puzzling observation of parallel alignment of cells for static and quasi-static stresses and of nearly perpendicular alignment for dynamically varying stresses. In addition, we predict the response of the cellular orientation to a sinusoidally varying applied stress as a function of frequency. The dependence of the cell orientation angle on the Poisson ratio of the surrounding material can be used to distinguish systems in which cell activity is controlled by stress from those where cell activity is controlled by strain. Reference: Nature Physics, vol. 3, pp 655 (2007).
Dynamic Response and Dynamic Failure Mode of a Weak Intercalated Rock Slope Using a Shaking Table
NASA Astrophysics Data System (ADS)
Fan, Gang; Zhang, Jianjing; Wu, Jinbiao; Yan, Kongming
2016-08-01
A large-scale shaking table test was performed to study the dynamic response of slopes parallel to geological bedding (bedding slopes) and slopes that cross-cut geological bedding (counter-bedding slopes). The test results show that the acceleration amplification coefficients increase with increasing elevation and, when the input earthquake amplitude is greater than 0.3 g, both bedding and counter-bedding slopes begin to show nonlinear dynamic response characteristics. With increasing elevation, the displacement of the bedding slope surface increases greatly. Conversely, the displacement of the counter-bedding slope surface increases first and then decreases; the slope develops a bulge at the relative elevation of 0.85. The displacement of the bedding slope surface is greater than that of the counter-bedding slope. The counter-bedding slope is more seismically stable compared with the bedding slope. Based on the Hilbert-Huang transform and marginal spectrum theories, the processes that develop dynamic damage of the bedding and counter-bedding slopes are identified. It is shown that the dynamic failure mode of the bedding slope is mainly represented by vertical tensile cracks at the rear of the slope, bedding slide of the strata along the weak intercalation, and rock collapse from the slope crest. However, the dynamic failure mode of the counter-bedding slope is mainly represented by staggered horizontal and vertical fissures, extrusion of the weak intercalation, and breakage at the slope crest.
Transient response characteristics in a biomolecular integral controller.
Sen, Shaunak
2016-04-01
The cellular behaviour of perfect adaptation is achieved through the use of an integral control element in the underlying biomolecular circuit. It is generally unclear how integral action affects the important aspect of transient response in these biomolecular systems, especially in light of the fact that it typically deteriorates the transient response in engineering contexts. To address this issue, the authors investigated the transient response in a computational model of a simple biomolecular integral control system involved in bacterial signalling. They find that the transient response can actually speed up as the integral gain parameter increases. On further analysis, they find that the underlying dynamics are composed of slow and fast modes and the speed-up of the transient response is because of the speed-up of the slow-mode dynamics. Finally, they note how an increase in the integral gain parameter also leads to a decrease in the amplitude of the transient response, consistent with the overall improvement in the transient response. These results should be useful in understanding the overall effect of integral action on system dynamics, particularly for biomolecular systems. PMID:26997660
Dynamic characteristics of a vibrating beam with periodic variation in bending stiffness
NASA Technical Reports Server (NTRS)
Townsend, John S.
1987-01-01
A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. Using a perturbation expansion technique the free vibration solution is obtained in a closed-form, and the effects of system parameters on beam response are explored. It is found that periodic stiffness acts to modulate the modal displacements from the characteristic shape of a simple sine wave. The results are verified by a finite element solution and through experimental testing.
Dynamic characteristics of a vibrating beam with periodic variation in bending stiffness
NASA Technical Reports Server (NTRS)
Townsend, John S.
1987-01-01
A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. The effects of system parameters on beam response are explored with a perturbation expansion technique. It is found that periodic stiffness acts to modulate the modal displacements from the characteristic shape of a simple sine wave. The results are verified by a finite element solution and through experimental testing.
NASA Astrophysics Data System (ADS)
Long, Xu; Ge, Fei; Wang, Lei; Hong, Youshi
2009-06-01
This paper investigates the effects of structure parameters on dynamic responses of submerged floating tunnel (SFT) under hydrodynamic loads. The structure parameters includes buoyancy-weight ratio (BWR), stiffness coefficients of the cable systems, tunnel net buoyancy and tunnel length. First, the importance of structural damp in relation to the dynamic responses of SFT is demonstrated and the mechanism of structural damp effect is discussed. Thereafter, the fundamental structure parameters are investigated through the analysis of SFT dynamic responses under hydrodynamic loads. The results indicate that the BWR of SFT is a key structure parameter. When BWR is 1.2, there is a remarkable trend change in the vertical dynamic response of SFT under hydrodynamic loads. The results also indicate that the ratio of the tunnel net buoyancy to the cable stiffness coefficient is not a characteristic factor affecting the dynamic responses of SFT under hydrodynamic loads.
Evaluation of allergic response using dynamic thermography
NASA Astrophysics Data System (ADS)
Rokita, E.; Rok, T.; Tatoń, G.
2015-03-01
Skin dynamic termography supplemented by a mathematical model is presented as an objective and sensitive indicator of the skin prick test result. Termographic measurements were performed simultaneously with routine skin prick tests. The IR images were acquired every 70 s up to 910 s after skin prick. In the model histamine is treated as the principal mediator of the allergic reaction. Histamine produces vasolidation and the engorged vessels are responsible for an increase in skin temperature. The model parameters were determined by fitting the analytical solutions to the spatio-temporal distributions of the differences between measured and baseline temperatures. The model reproduces experimental data very well (coefficient of determination = 0.805÷0.995). The method offers a set of parameters to describe separately skin allergic reaction and skin reactivity. The release of histamine after allergen injection is the best indicator of allergic response. The diagnostic parameter better correlates with the standard evaluation of a skin prick test (correlation coefficient = 0.98) than the result of the thermographic planimetric method based on temperature and heated area determination (0.81). The high sensitivity of the method allows for determination of the allergic response in patients with the reduced skin reactivity.
Fluctuations and Response in Geophysical Fluid Dynamics
NASA Astrophysics Data System (ADS)
Lucarini, Valerio
The climate is a complex, chaotic, non-equilibrium system featuring a limited horizon of predictability, variability on a vast range of temporal and spatial scales, instabilities resulting into energy transformations, and mixing and dissipative processes resulting into entropy production. Despite great progresses, we still do not have a complete theory of climate dynamics able to account for instabilities, equilibration processes, response to changing parameters of the system, and multiscale effects. We will outline some possible applications of the response theory developed by Ruelle for non-equilibrium statistical mechanical systems, showing how it allows for setting on firm ground and on a coherent framework concepts like climate sensitivity, climate response, and climate tipping points, and to construct parametrizations for unresolved processes. We will show results for comprehensive global climate models. The results are promising in terms of suggesting new ways for approaching the problem of climate change prediction and for using more efficiently the enormous amounts of data produced by modeling groups around the world. Ref: V. Lucarini, R. Blender, C. Herbert, F. Ragone, S. Pascale, J. Wouters, Mathematical and Physical Ideas for Climate Science, Reviews of Geophysics 52, 809-859 (2014)
User's Manual for Computer Program ROTOR. [to calculate tilt-rotor aircraft dynamic characteristics
NASA Technical Reports Server (NTRS)
Yasue, M.
1974-01-01
A detailed description of a computer program to calculate tilt-rotor aircraft dynamic characteristics is presented. This program consists of two parts: (1) the natural frequencies and corresponding mode shapes of the rotor blade and wing are developed from structural data (mass distribution and stiffness distribution); and (2) the frequency response (to gust and blade pitch control inputs) and eigenvalues of the tilt-rotor dynamic system, based on the natural frequencies and mode shapes, are derived. Sample problems are included to assist the user.
Photonic water dynamically responsive to external stimuli.
Sano, Koki; Kim, Youn Soo; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Aida, Takuzo
2016-01-01
Fluids that contain ordered nanostructures with periodic distances in the visible-wavelength range, anomalously exhibit structural colours that can be rapidly modulated by external stimuli. Indeed, some fish can dynamically change colour by modulating the periodic distance of crystalline guanine sheets cofacially oriented in their fluid cytoplasm. Here we report that a dilute aqueous colloidal dispersion of negatively charged titanate nanosheets exhibits structural colours. In this 'photonic water', the nanosheets spontaneously adopt a cofacial geometry with an ultralong periodic distance of up to 675 nm due to a strong electrostatic repulsion. Consequently, the photonic water can even reflect near-infrared light up to 1,750 nm. The structural colour becomes more vivid in a magnetic flux that induces monodomain structural ordering of the colloidal dispersion. The reflective colour of the photonic water can be modulated over the entire visible region in response to appropriate physical or chemical stimuli. PMID:27572806
Static & Dynamic Response of 2D Solids
Energy Science and Technology Software Center (ESTSC)
1996-07-15
NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surfacemore » contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.« less
Dynamic Assessment and Response to Intervention
Grigorenko, Elena L.
2013-01-01
This article compares and contrasts the main features of dynamic testing and assessment (DT/A) and response to intervention (RTI). The comparison is carried out along the following lines: (a) historical and empirical roots of both concepts, (b) premises underlying DT/A and RTI, (c) terms used in these concepts, (d) use of these concepts, (e) evidence in support of DT/A and RTI, and (f) expectations associated with each of the concepts. The main outcome of this comparison is a conclusion that both approaches belong to one family of methodologies in psychology and education whose key feature is in blending assessment and intervention in one holistic activity. Because DT/A has been around much longer than RTI, it makes sense for the proponents of RTI to consider both the accomplishments and frustrations that have accumulated in the field of DT/A. PMID:19073895
Dynamic response of damaged angleplied fiber composites
NASA Technical Reports Server (NTRS)
Chamis, C. C.; Sinclair, J. H.; Lark, R. F.
1979-01-01
An investigation was conducted to determine the effects of low level damage induced by monotonic load, cyclic load and/or residual stresses on the vibration frequencies and damping factors of fiber composite angleplied laminates. Two different composite systems were studied - low modulus fiber and ultra high modulus fiber composites. The results obtained showed that the frequencies and damping factors of angleplied laminates made from low modulus fiber composites are sensitive to low level damage while those made from ultra high modulus composites are not. Also, vibration tests may not be sufficiently sensitive to assess concentrated local damage in angleplied laminates. And furthermore, dynamic response determined from low-velocity impact coupled with the Fast Fourier Transform and packaged in a minicomputer can be a convenient procedure for assessing low-level damage in fiber composite angleplied laminates.
Dynamic response of Hovercraft lift fans
NASA Astrophysics Data System (ADS)
Moran, D. D.
1981-08-01
Hovercraft lift fans are subjected to varying back pressure due to wave action and craft motions when these vehicles are operating in a seaway. The oscillatory back pressure causes the fans to perform dynamically, exhibiting a hysteresis type of response and a corresponding degradation in mean performance. Since Hovercraft motions are influenced by variations in lift fan pressure and discharge, it is important to understand completely the nature of the dynamic performance of lift fans in order to completely solve the Hovercraft seakeeping problem. The present study was performed to determine and classify the instabilities encountered in a centrifugal fan operating against time-varying back pressure. A model-scale experiment was developed in which the fan discharge was directed into a flow-measuring device, terminating in a rotating valve which produced an oscillatory back pressure superimposed upon a mean aerodynamic resistance. Pressure and local velocity were measured as functions of time at several locations in the fan volute. The measurements permitted the identification of rotating (or propagating) stall in the impeller. One cell and two cell configurations were classified and the transient condition connecting these two configurations was observed. The mechanisms which lead to rotating stall in a centrifugal compressor are presented and discussed with specific reference to Hovercraft applications.
Static and dynamic characteristics of parallel-grooved seals
NASA Technical Reports Server (NTRS)
Iwatsubo, Takuzo; Yang, Bo-Suk; Ibaraki, Ryuji
1987-01-01
Presented is an analytical method to determine static and dynamic characteristics of annular parallel-grooved seals. The governing equations were derived by using the turbulent lubrication theory based on the law of fluid friction. Linear zero- and first-order perturbation equations of the governing equations were developed, and these equations were analytically investigated to obtain the reaction force of the seals. An analysis is presented that calculates the leakage flow rate, the torque loss, and the rotordynamic coefficients for parallel-grooved seals. To demonstrate this analysis, we show the effect of changing number of stages, land and groove width, and inlet swirl on stability of the boiler feed water pump seals. Generally, as the number of stages increased or the grooves became wider, the leakage flow rate and rotor-dynamic coefficients decreased and the torque loss increased.
Dynamic characteristics of the LLNL Precision Engineering Research Lathe
Franse, J.; Roblee, J.W.; Modemann, K.
1988-08-31
The dynamic characteristics of the Precision Engineering Research Lathe (PERL) have been investigated experimentally, up to a frequency of 1000 Hz. In successive tests, the exciting force was applied to either the X slide or the (non-rotating) spindle, and in the X or Z direction. These are the critical directions for turning operations on this T base type lathe. Each of these tests was furthermore done with the servo system active and with the servo system off (slides clamped, control loops open). The applied force fluctuations and the resulting relative displacement, between a capacitive probe mounted on the X slide and the spindle, were measured during the experiments. From these data, the relative dynamic compliances between the tool and the workpiece, in the Z and X directions, have been determined. The most important resonant frequencies, modes, and compliances are reported. Their consequences with regard to the surface quality of diamond turned parts are also discussed. 3 refs., 11 figs.
The Tendency to Omit Items: Another Deviant Response Characteristic.
ERIC Educational Resources Information Center
Hattie, John
1983-01-01
It is argued that the tendency to omit items is a deviant response characteristic. Three studies using a self-actualization measure are outlined. Persons who omitted items did so because of fatigue, confusion with some items, unpreparedness to disclose information, and/or because they may not trust the researcher with certain information.…
NASA Astrophysics Data System (ADS)
Haberman, Keith
2001-07-01
A micromechanically based constitutive model for the dynamic inelastic behavior of brittle materials, specifically "Dionysus-Pentelicon marble" with distributed microcracking is presented. Dionysus-Pentelicon marble was used in the construction of the Parthenon, in Athens, Greece. The constitutive model is a key component in the ability to simulate this historic explosion and the preceding bombardment form cannon fire that occurred at the Parthenon in 1678. Experiments were performed by Rosakis (1999) that characterized the static and dynamic response of this unique material. A micromechanical constitutive model that was previously successfully used to model the dynamic response of granular brittle materials is presented. The constitutive model was fitted to the experimental data for marble and reproduced the experimentally observed basic uniaxial dynamic behavior quite well. This micromechanical constitutive model was then implemented into the three dimensional nonlinear lagrangain finite element code Dyna3d(1998). Implementing this methodology into the three dimensional nonlinear dynamic finite element code allowed the model to be exercised on several preliminary impact experiments. During future simulations, the model is to be used in conjunction with other numerical techniques to simulate projectile impact and blast loading on the Dionysus-Pentelicon marble and on the structure of the Parthenon.
Response Characteristics of a Linear Rotorcraft Vibration Model
NASA Technical Reports Server (NTRS)
Kunz, Donald L.
1982-01-01
A fully coupled vibration model, consisting of a rotor with only flapping degrees of freedom plus pylon and fuselage pitching motion, was used in a parametric study undertaken to investigate the response characteristics of a simplified helicopter. Among the parameters studied were uncoupled body frequency, blade stiffness, hinge offset, advance ratio, and mast height. Results from the harmonic balance solution of the equations of motion show how each of these quantities affects the response of the model. The results also indicate that there is a potential for reducing vibration response through the judicious definition of the design parameters.
Achieving reliable communication in dynamic emergency responses.
Chipara, Octav; Plymoth, Anders N; Liu, Fang; Huang, Ricky; Evans, Brian; Johansson, Per; Rao, Ramesh; Griswold, William G
2011-01-01
Emergency responses require the coordination of first responders to assess the condition of victims, stabilize their condition, and transport them to hospitals based on the severity of their injuries. WIISARD is a system designed to facilitate the collection of medical information and its reliable dissemination during emergency responses. A key challenge in WIISARD is to deliver data with high reliability as first responders move and operate in a dynamic radio environment fraught with frequent network disconnections. The initial WIISARD system employed a client-server architecture and an ad-hoc routing protocol was used to exchange data. The system had low reliability when deployed during emergency drills. In this paper, we identify the underlying causes of unreliability and propose a novel peer-to-peer architecture that in combination with a gossip-based communication protocol achieves high reliability. Empirical studies show that compared to the initial WIISARD system, the redesigned system improves reliability by as much as 37% while reducing the number of transmitted packets by 23%. PMID:22195075
Achieving Reliable Communication in Dynamic Emergency Responses
Chipara, Octav; Plymoth, Anders N.; Liu, Fang; Huang, Ricky; Evans, Brian; Johansson, Per; Rao, Ramesh; Griswold, William G.
2011-01-01
Emergency responses require the coordination of first responders to assess the condition of victims, stabilize their condition, and transport them to hospitals based on the severity of their injuries. WIISARD is a system designed to facilitate the collection of medical information and its reliable dissemination during emergency responses. A key challenge in WIISARD is to deliver data with high reliability as first responders move and operate in a dynamic radio environment fraught with frequent network disconnections. The initial WIISARD system employed a client-server architecture and an ad-hoc routing protocol was used to exchange data. The system had low reliability when deployed during emergency drills. In this paper, we identify the underlying causes of unreliability and propose a novel peer-to-peer architecture that in combination with a gossip-based communication protocol achieves high reliability. Empirical studies show that compared to the initial WIISARD system, the redesigned system improves reliability by as much as 37% while reducing the number of transmitted packets by 23%. PMID:22195075
Structural dynamic characteristics of a Space Station Freedom first assembly flight concept
NASA Technical Reports Server (NTRS)
Kaszubowski, Martin J.; Martinovic, Zoran N.; Cooper, Paul A.
1990-01-01
A study has been conducted of the dynamic characteristics of the first flight of NASA's Space Station Freedom and its response to a typical preboost excitation; the FEM model of the structure used encompasses 88 flexible modes below 5 Hz. The low frequency modes of the system are noted to have been dominated by the relatively low stiffness of such components as the photovoltaic arrays, thermal radiators, and alpha joint. The spacecraft backbone-forming truss was stiffer, exhibiting no deformation below 3 Hz. Reboost forcing-function response was moderate.
Dynamic response of cantilever retaining walls
Veletsos, A.S.; Younan, A.H.; Bandyopadhyay, K.
1996-10-01
A critical evaluation is made of the response to horizontal ground shaking of flexible cantilever retaining walls that are elastically constrained against rotation at their base. The retained medium is idealized as a uniform, linear, viscoelastic stratum of constant thickness and semi-infinite extent in the horizontal direction. The parameters varied include the flexibilities of the wall and its base, the properties of the retained medium, and the characteristics of the ground motion. In addition to long-period, effectively static excitations, both harmonic base motions and an actual earthquake record are considered. The response quantities examined include the displacements of the wall relative to the moving base, the wall pressures, and the associated shears and bending moments. The method of analysis employed is described only briefly, emphasis being placed on the presentation and interpretation of the comprehensive numerical solutions. It is shown that, for realistic wall flexibilities, the maximum wall forces are significantly lower than those obtained for fixed-based rigid walls and potentially of the same order of magnitude as those computed by the Mononobe-Okabe method.
The Dynamic Characteristic and Hysteresis Effect of an Air Spring
NASA Astrophysics Data System (ADS)
Löcken, F.; Welsch, M.
2015-02-01
In many applications of vibration technology, especially in chassis, air springs present a common alternative to steel spring concepts. A design-independent and therefore universal approach is presented to describe the dynamic characteristic of such springs. Differential and constitutive equations based on energy balances of the enclosed volume and the mountings are given to describe the nonlinear and dynamic characteristics. Therefore all parameters can be estimated directly from physical and geometrical properties, without parameter fitting. The numerically solved equations fit very well to measurements of a passenger car air spring. In a second step a simplification of this model leads to a pure mechanical equation. While in principle the same parameters are used, just an empirical correction of the effective heat transfer coefficient is needed to handle some simplification on this topic. Finally, a linearization of this equation leads to an analogous mechanical model that can be assembled from two common spring- and one dashpot elements in a specific arrangement. This transfer into "mechanical language" enables a system description with a simple force-displacement law and a consideration of the nonobvious hysteresis and stiffness increase of an air spring from a mechanical point of view.
Characteristic ion distributions in the dynamic auroral transition region
NASA Astrophysics Data System (ADS)
Zeng, W.; Horwitz, J. L.; Tu, J.-N.
2006-04-01
A Dynamic Fluid Kinetic (DyFK) simulation is conducted to study the H+/O+ flows and distribution functions in the high-latitude dynamic transition region, specifically from 1000 km to about 4000 km altitude. Here, the collisional-to-collisionless transition region is that region where Coulomb collisions have significant but not dominant effects on the ion distributions. In this study, a simulation flux tube, which extends from 120 km to 3 RE altitude, is assumed to experience a pulse of auroral effects for approximately 20 minutes, including both soft electron precipitation and transverse wave heating, and then according to different geophysical circumstances, either to relax following the cessation of such auroral effects or to be heated further continuously by waves with power at higher frequencies. Our principal purpose in this investigation is to elicit the characteristic ion distribution functions in the auroral transition region, where both collisions and kinetic processes play significant roles. The characteristics of the simulated O+ and H+ velocity distributions, such as kidney bean shaped H+ distributions, and O+ distributions having cold cores with upward folded conic wings, resemble those observed by satellites at similar altitudes and geographic conditions. From the simulated distribution function results under different geophysical conditions, we find that O+-O+ and O+-H+ collisions, in conjunction with the kinetic and auroral processes, are key factors in the velocity distributions up to 4000 km altitude, especially for the low speed portions, for both O+ and H+ ions.
Strength and dynamic characteristics analyses of wound composite axial impeller
NASA Astrophysics Data System (ADS)
Wang, Jifeng; Olortegui-Yume, Jorge; Müller, Norbert
2012-03-01
A low cost, light weight, high performance composite material turbomachinery impeller with a uniquely designed blade patterns is analyzed. Such impellers can economically enable refrigeration plants to use water as a refrigerant (R718). A strength and dynamic characteristics analyses procedure is developed to assess the maximum stresses and natural frequencies of these wound composite axial impellers under operating loading conditions. Numerical simulation using FEM for two-dimensional and three-dimensional impellers was investigated. A commercially available software ANSYS is used for the finite element calculations. Analysis is done for different blade geometries and then suggestions are made for optimum design parameters. In order to avoid operating at resonance, which can make impellers suffer a significant reduction in the design life, the designer must calculate the natural frequency and modal shape of the impeller to analyze the dynamic characteristics. The results show that using composite Kevlar fiber/epoxy matrix enables the impeller to run at high tip speed and withstand the stresses, no critical speed will be matched during start-up and shut-down, and that mass imbalances of the impeller shall not pose a critical problem.
Frequency-domain correction of sensor dynamic error for step response.
Yang, Shuang-Long; Xu, Ke-Jun
2012-11-01
To obtain accurate results in dynamic measurements it is required that the sensors should have good dynamic performance. In practice, sensors have non-ideal dynamic characteristics due to their small damp ratios and low natural frequencies. In this case some dynamic error correction methods can be adopted for dealing with the sensor responses to eliminate the effect of their dynamic characteristics. The frequency-domain correction of sensor dynamic error is a common method. Using the existing calculation method, however, the correct frequency-domain correction function (FCF) cannot be obtained according to the step response calibration experimental data. This is because of the leakage error and invalid FCF value caused by the cycle extension of the finite length step input-output intercepting data. In order to solve these problems the data splicing preprocessing and FCF interpolation are put forward, and the FCF calculation steps as well as sensor dynamic error correction procedure by the calculated FCF are presented in this paper. The proposed solution is applied to the dynamic error correction of the bar-shaped wind tunnel strain gauge balance so as to verify its effectiveness. The dynamic error correction results show that the adjust time of the balance step response is shortened to 10 ms (shorter than 1/30 before correction) after frequency-domain correction, and the overshoot is fallen within 5% (less than 1/10 before correction) as well. The dynamic measurement accuracy of the balance is improved significantly. PMID:23206091
Frequency-domain correction of sensor dynamic error for step response
NASA Astrophysics Data System (ADS)
Yang, Shuang-Long; Xu, Ke-Jun
2012-11-01
To obtain accurate results in dynamic measurements it is required that the sensors should have good dynamic performance. In practice, sensors have non-ideal dynamic characteristics due to their small damp ratios and low natural frequencies. In this case some dynamic error correction methods can be adopted for dealing with the sensor responses to eliminate the effect of their dynamic characteristics. The frequency-domain correction of sensor dynamic error is a common method. Using the existing calculation method, however, the correct frequency-domain correction function (FCF) cannot be obtained according to the step response calibration experimental data. This is because of the leakage error and invalid FCF value caused by the cycle extension of the finite length step input-output intercepting data. In order to solve these problems the data splicing preprocessing and FCF interpolation are put forward, and the FCF calculation steps as well as sensor dynamic error correction procedure by the calculated FCF are presented in this paper. The proposed solution is applied to the dynamic error correction of the bar-shaped wind tunnel strain gauge balance so as to verify its effectiveness. The dynamic error correction results show that the adjust time of the balance step response is shortened to 10 ms (shorter than 1/30 before correction) after frequency-domain correction, and the overshoot is fallen within 5% (less than 1/10 before correction) as well. The dynamic measurement accuracy of the balance is improved significantly.
The nonlinear forced response characteristics of contained fluids in microgravity
NASA Technical Reports Server (NTRS)
Vanschoor, M. C.; Crawley, E. F.
1992-01-01
An experimental study of the change in the lateral slosh behavior of contained fluids between earth and space is presented. The experimental apparatus used to determine the slosh characteristics is described and a nonlinear analytic model of a coupled fluid/spacecraft system is outlined. The forced response characteristics of silicon oil and distilled water in cylinder tanks with either a flat or spherical bottom are reported and discussed. A comparison of the measured earth and space results identifies and highlights the effects of gravity on the linear and nonlinear slosh behavior of these fluids.
NASA Technical Reports Server (NTRS)
Fasanella, E. L.; Mcgehee, J. R.; Pappas, M. S.
1977-01-01
An experimental and analytical investigation was conducted to determine which characteristics of a light aircraft landing gear influence gear dynamic behavior significantly. The investigation focused particularly on possible modification for load control. Pseudostatic tests were conducted to determine the gear fore-and-aft spring constant, axial friction as a function of drag load, brake pressure-torque characteristics, and tire force-deflection characteristics. To study dynamic tire response, vertical drops were conducted at impact velocities of 1.2, 1.5, and 1.8 m/s onto a level surface; to determine axial-friction effects, a second series of vertical drops were made at 1.5 m/s onto surfaces inclined 5 deg and 10 deg to the horizontal. An average dynamic axial-friction coefficient of 0.15 was obtained by comparing analytical data with inclined surface drop test data. Dynamic strut bending and associated axial friction were found to be severe for the drop tests on the 10 deg surface.
Dynamic characteristics of a simple bursting neuron model
NASA Astrophysics Data System (ADS)
Nakajima, Koji; Sato, Shigeo; Hayakawa, Yoshihiro
We present a simple neuron model that shows a rich property in spite of the simple structure derived from the simplification of the Hindmarsh-Rose, the Morris-Lecar, and the Hodgkin-Huxley models. The model is a typical example whose characteristics can be discussed through the concept of potential with active areas. A potential function is able to provide a global landscape for dynamics of a model, and the dynamics is explained in connection with the disposition of the active areas on the potential, and hence we are able to discuss the global dynamic behaviors and the common properties among these realistic models. The obtained outputs are broadly classified as simple oscillations, spiking, bursting, and chaotic oscillations. The bursting outputs are classified as with spike undershoot and without spike undershoot, and the bursts without spike undershoot are classified as with tapered and without tapered. We show the parameter dependence of these outputs and discuss the connection between these outputs and the potential with active areas.
Dynamic Characteristic Analysis of Spinal Motor Control Between 11- and 15-Year-Old Children.
Chow, Daniel H; Lau, Newman M
2016-07-01
Spinal motor control can provide substantial insight for the causes of spinal musculoskeletal disorders. Its dynamic characteristics however, have not been fully investigated. The objective of this study is to explore the dynamic characteristics of spinal motor control via the fractional Brownian motion mathematical technique. Spinal curvatures and repositioning errors of different spinal regions in 64 children age 11- or 15-years old during upright stance were measured and compared for the effects of age and gender. With the application of the fractional Brownian motion analytical technique to the changes of spinal curvatures, distinct persistent movement behaviors could be determined, which could be interpreted physiologically as open-loop behaviors. Moreover, it was found that the spinal motor control of 15-year-old children was better than that of 11-year-old children with smaller repositioning error and less curvature variability as well as shorter response time and smaller curvature deformation. PMID:26314089
Dynamic characteristics of piezoelectric shear deformable composite plates
NASA Astrophysics Data System (ADS)
Kolar, Ramesh
2004-07-01
Layered composites have attracted attention for their high specific stiffness, high specific strength, and application specific tailoring of their properties. It is also recognized that layered composites are prone to delamination failure in addition to other failure modes. Consideration of transverse shear on the deformation behavior of the composites is an important aspect in the study of delamination mode failure of such plates. In this paper, we consider the effects of including the transverse shear deformation on the vibration characteristics of layered piezoelectric composites. The formulation is based on the Raleigh-Ritz method using the beam characteristic functions. MATLAB based symbollic math tool box is used in evaluating th eintegrals resulting from the Raleigh Ritz approach. Various commonly occuring boundary conditions are discussed. Results are provided showing the effects of the shear deformation on the dynamics of layered laminated composites. The effects of laminate thickness, fiber orientation, and the plate aspect ratios on the free vibration characteristics of the composite laminates are given to demonstrate the methodology described.
Dynamical theory of active cellular response to external stress.
De, Rumi; Safran, Samuel A
2008-09-01
We present a comprehensive, theoretical treatment of the orientational response to external stress of active, contractile cells embedded in a gel-like elastic medium. The theory includes both the forces that arise from the deformation of the matrix as well as forces due to the internal regulation of the stress fibers and focal adhesions of the cell. We calculate the time-dependent response of both the magnitude and the direction of the elastic dipole that characterizes the active forces exerted by the cell, for various situations. For static or quasistatic external stress, cells orient parallel to the stress while for high frequency dynamic external stress, cells orient nearly perpendicular. Both numerical and analytical calculations of these effects are presented. In addition we predict the relaxation time for the cellular response for both slowly and rapidly varying external stresses; several characteristic scaling regimes for the relaxation time as a function of applied frequency are predicted. We also treat the case of cells for which the regulation of the stress fibers and focal adhesions is controlled by strain (instead of stress) and show that the predicted dependence of the cellular orientation on the Poisson ratio of the matrix can differentiate strain vs stress regulation of cellular response. PMID:18851081
Dynamical theory of active cellular response to external stress
NASA Astrophysics Data System (ADS)
de, Rumi; Safran, Samuel A.
2008-09-01
We present a comprehensive, theoretical treatment of the orientational response to external stress of active, contractile cells embedded in a gel-like elastic medium. The theory includes both the forces that arise from the deformation of the matrix as well as forces due to the internal regulation of the stress fibers and focal adhesions of the cell. We calculate the time-dependent response of both the magnitude and the direction of the elastic dipole that characterizes the active forces exerted by the cell, for various situations. For static or quasistatic external stress, cells orient parallel to the stress while for high frequency dynamic external stress, cells orient nearly perpendicular. Both numerical and analytical calculations of these effects are presented. In addition we predict the relaxation time for the cellular response for both slowly and rapidly varying external stresses; several characteristic scaling regimes for the relaxation time as a function of applied frequency are predicted. We also treat the case of cells for which the regulation of the stress fibers and focal adhesions is controlled by strain (instead of stress) and show that the predicted dependence of the cellular orientation on the Poisson ratio of the matrix can differentiate strain vs stress regulation of cellular response.
Dynamic response of reverse Taylor impact based on DIC technology
NASA Astrophysics Data System (ADS)
Liu, Jiancheng; Pi, Aiguo; Wu, Haijun; Huang, Fenglei
2015-09-01
Reverse ballistic impact test, which can obtain the response data of rod/projectile more comprehensive and quantitative than forward impact test, was widely used for the measurement of material dynamic and structure response. Based on the DIC technology and traditional optical measurement (high-speed camera measurement), the Taylor experiment of reverse ballistic with different length-diameter ratio and different impact velocities were carried out by 57 mm compression-shear type light-gas gun, which provides the instantaneous response data of the Taylor rod in microsecond level. Then, the transient structural deformation of the specimen and the characteristics of plastic wave propagation were analysed by DIC technology and compared with traditional optical measurement. Applying the theory of reverse Taylor impact deformation and combining with the simulation results by LS-DYNA, the rules of structure deformation and plastic wave propagation were obtained. The method above can be applied for the structure response of penetrator under the condition of reverse ballistic penetration.
A computational analysis of motor synergies by dynamic response decomposition
Alessandro, Cristiano; Carbajal, Juan Pablo; d'Avella, Andrea
2014-01-01
Analyses of experimental data acquired from humans and other vertebrates have suggested that motor commands may emerge from the combination of a limited set of modules. While many studies have focused on physiological aspects of this modularity, in this paper we propose an investigation of its theoretical foundations. We consider the problem of controlling a planar kinematic chain, and we restrict the admissible actuations to linear combinations of a small set of torque profiles (i.e., motor synergies). This scheme is equivalent to the time-varying synergy model, and it is formalized by means of the dynamic response decomposition (DRD). DRD is a general method to generate open-loop controllers for a dynamical system to solve desired tasks, and it can also be used to synthesize effective motor synergies. We show that a control architecture based on synergies can greatly reduce the dimensionality of the control problem, while keeping a good performance level. Our results suggest that in order to realize an effective and low-dimensional controller, synergies should embed features of both the desired tasks and the system dynamics. These characteristics can be achieved by defining synergies as solutions to a representative set of task instances. The required number of synergies increases with the complexity of the desired tasks. However, a possible strategy to keep the number of synergies low is to construct solutions to complex tasks by concatenating synergy-based actuations associated to simple point-to-point movements, with a limited loss of performance. Ultimately, this work supports the feasibility of controlling a non-linear dynamical systems by linear combinations of basic actuations, and illustrates the fundamental relationship between synergies, desired tasks and system dynamics. PMID:24474915
Dynamic characteristics of an assembly of prop-fan blades
NASA Technical Reports Server (NTRS)
Srinivasan, A. V.; Kielb, R. E.; Lawrence, C.
1986-01-01
In contrast to conventional propellers, propfan blades are thin and highly swept-back, thereby giving rise to large bending and twisting deformations and complex vibratory characteristics. Aerodynamic performance depends on the extent of steady state deformation, and the aeroelastic response depends on the vibratory frequency and mode shape. Attention is presently given to the principal results of structural analyses for a five-bladed propfan assembly; these results are compared with test data. The results encompass both steady deformations and vibratory frequencies and mode shapes in a vacuum centrifugal environment.
Dynamic bioactive stimuli-responsive polymeric surfaces
NASA Astrophysics Data System (ADS)
Pearson, Heather Marie
This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of --COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface anticoagulant attributes, PE and PTFE surfaces were functionalized with pH-responsive poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) polyelectrolyte tethers terminated with NH2 and COOH groups. The goal of these studies was to develop switchable stimuli-responsive polymeric surfaces that interact with biological environments and display simultaneous antimicrobial and anticoagulant properties. Antimicrobial AMP was covalently attached to --COOH terminal ends of protected PAA, while anticoagulant heparin (HEP) was attached to terminal --NH2 groups of P2VP. When pH < 2.3, the P2VP segments are protonated and extend, but for pH > 5.5, they collapse while the PAA segments extend. Such surfaces, when exposed to Staphylococcus aureus, inhibit bacterial growth due to the presence of AMP, as well as are effective anticoagulants due to the presence of covalently attached HEP. Comparison of these "dynamic" pH responsive surfaces with "static" surfaces terminated with AMP entities show significant enhancement of longevity and surface activity against microbial film formation. The last portion of this dissertation focuses on the covalent attachment of living T1 and Φ11 bacteriophages (phages) on PE and PTFE surface
Fluid mechanics of dynamic stall. II - Prediction of full scale characteristics
NASA Technical Reports Server (NTRS)
Ericsson, L. E.; Reding, J. P.
1988-01-01
Analytical extrapolations are made from experimental subscale dynamics to predict full scale characteristics of dynamic stall. The method proceeds by establishing analytic relationships between dynamic and static aerodynamic characteristics induced by viscous flow effects. The method is then validated by predicting dynamic test results on the basis of corresponding static test data obtained at the same subscale flow conditions, and the effect of Reynolds number on the static aerodynamic characteristics are determined from subscale to full scale flow conditions.
Design of helicopter rotor blades for optimum dynamic characteristics
NASA Technical Reports Server (NTRS)
Peters, D. A.; Ko, T.; Korn, A. E.; Rossow, M. P.
1983-01-01
The possibilities and limitations of tailoring blade mass and stiffness distributions to give an optimum blade design in terms of weight, inertia, and dynamic characteristics are discussed. The extent that changes in mass of stiffness distribution can be used to place rotor frequencies at desired locations is determined. Theoretical limits to the amount of frequency shift are established. Realistic constraints on blade properties based on weight, mass, moment of inertia, size, strength, and stability are formulated. The extent that the hub loads can be minimized by proper choice of E1 distribution, and the minimum hub loads which can be approximated by a design for a given set of natural frequencies are determined. Aerodynamic couplings that might affect the optimum blade design, and the relative effectiveness of mass and stiffness distribution on the optimization procedure are investigated.
Design of helicopter rotor blades for optimum dynamic characteristics
NASA Technical Reports Server (NTRS)
Peters, D. A.; Ko, T.; Korn, A. E.; Rossow, M. P.
1982-01-01
The possibilities and the limitations of tailoring blade mass and stiffness distributions to give an optimum blade design in terms of weight, inertia, and dynamic characteristics are investigated. Changes in mass or stiffness distribution used to place rotor frequencies at desired locations are determined. Theoretical limits to the amount of frequency shift are established. Realistic constraints on blade properties based on weight, mass moment of inertia size, strength, and stability are formulated. The extent hub loads can be minimized by proper choice of EL distribution is determined. Configurations that are simple enough to yield clear, fundamental insights into the structural mechanisms but which are sufficiently complex to result in a realistic result for an optimum rotor blade are emphasized.
Spontaneous Facial Mimicry in Response to Dynamic Facial Expressions
ERIC Educational Resources Information Center
Sato, Wataru; Yoshikawa, Sakiko
2007-01-01
Based on previous neuroscientific evidence indicating activation of the mirror neuron system in response to dynamic facial actions, we hypothesized that facial mimicry would occur while subjects viewed dynamic facial expressions. To test this hypothesis, dynamic/static facial expressions of anger/happiness were presented using computer-morphing…
Nonlinear dynamical model and response of avian cranial kinesis.
Meekangvan, Preeda; A Barhorst, Alan; Burton, Thomas D; Chatterjee, Sankar; Schovanec, Lawrence
2006-05-01
All modern birds have kinetic skulls in which the upper bill can move relative to the braincase, but the biomechanics and motion dynamics of cranial kinesis in birds are poorly understood. In this paper, we model the dynamics of avian cranial kinesis, such as prokinesis and proximal rhynchokinesis in which the upper jaw pivots around the nasal-frontal (N-F) hinge. The purpose of this paper is to present to the biological community an approach that demonstrates the application of sophisticated predictive mathematical modeling tools to avian kinesis. The generality of the method, however, is applicable to the advanced study of the biomechanics of other skeletal systems. The paper begins with a review of the relevant biological literature as well as the essential morphology of avian kinesis, especially the mechanical coupling of the upper and lower jaw by the postorbital ligament. A planar model of the described bird jaw morphology is then developed that maintains the closed kinematic topology of the avian jaw mechanism. We then develop the full nonlinear equations of motion with the assumption that the M. protractor pterygoideus and M. depressor mandibulae act on the quadrate as a pure torque, and the nasal frontal hinge is elastic with damping. The mechanism is shown to be a single degree of freedom device due to the holonomic constraints present in the quadrate-jugal bar-upper jaw-braincase-quadrate kinematic chain as well as the quadrate-lower jaw-postorbital ligament-braincase-quadrate kinematic chain. The full equations are verified via simulation and animation using the parameters of a Grey Heron (Ardea cinerea). Next we develop a simplified analytical model of the equations by power series expansion. We demonstrate that this model reproduces the dynamics of the full model to a high degree of fidelity. We proceed to use the harmonic balance technique to develop the frequency response characteristics of the jaw mechanism. It is shown that this avian cranial
Dynamic Response Analysis of Microflow Electrochemical Sensors with Two Types of Elastic Membrane.
Zhou, Qiuzhan; Wang, Chunhui; Chen, Yongzhi; Chen, Shuozhang; Lin, Jun
2016-01-01
The Molecular Electric Transducer (MET), widely applied for vibration measurement, has excellent sensitivity and dynamic response at low frequencies. The elastic membrane in the MET is a significant factor with an obvious effect on the performance of the MET in the low frequency domain and is the focus of this paper. In simulation experiments, the elastic membrane and the reaction cavity of the MET were analysed in a model based on the multiphysics finite element method. Meanwhile, the effects caused by the elastic membrane elements are verified in this paper. With the numerical simulation and practical experiments, a suitable elastic membrane can be designed for different cavity structures. Thus, the MET can exhibit the best dynamic response characteristics to measure the vibration signals. With the new method presented in this paper, it is possible to develop and optimize the characteristics of the MET effectively, and the dynamic characteristics of the MET can be improved in a thorough and systematic manner. PMID:27171086
Dynamic Response Analysis of Microflow Electrochemical Sensors with Two Types of Elastic Membrane
Zhou, Qiuzhan; Wang, Chunhui; Chen, Yongzhi; Chen, Shuozhang; Lin, Jun
2016-01-01
The Molecular Electric Transducer (MET), widely applied for vibration measurement, has excellent sensitivity and dynamic response at low frequencies. The elastic membrane in the MET is a significant factor with an obvious effect on the performance of the MET in the low frequency domain and is the focus of this paper. In simulation experiments, the elastic membrane and the reaction cavity of the MET were analysed in a model based on the multiphysics finite element method. Meanwhile, the effects caused by the elastic membrane elements are verified in this paper. With the numerical simulation and practical experiments, a suitable elastic membrane can be designed for different cavity structures. Thus, the MET can exhibit the best dynamic response characteristics to measure the vibration signals. With the new method presented in this paper, it is possible to develop and optimize the characteristics of the MET effectively, and the dynamic characteristics of the MET can be improved in a thorough and systematic manner. PMID:27171086
Parametric Optimization of Ares I Propellant Slosh Characteristics Using Frequency Response Criteria
NASA Technical Reports Server (NTRS)
Orr, Jeb S.; Hall, Charles E.
2009-01-01
A novel technique for developing propellant slosh damping requirements with respect to the stability characteristics of large flexible launch vehicles is presented. A numerical algorithm is devised which allows an automated software program to rapidly converge to pseudo-optimal solutions that minimize required propellant slosh damping for multiple tanks while maintaining constraints on the frequency response characteristics of a particular open-loop plant transfer function. An implementation of the algorithm using a high-order linear model of the Ares I plant dynamics considers all relevant dynamic interactions of flexible body modes, propellant slosh, and nozzle inertia effects. A high-resolution propellant damping requirements table is produced that can be used for baffle design. The method is demonstrated to provide exceptional speed and accuracy when compared with the alternative human-in-the-loop approach.
Dynamical response theory for driven-dissipative quantum systems
NASA Astrophysics Data System (ADS)
Campos Venuti, Lorenzo; Zanardi, Paolo
2016-03-01
We discuss dynamical response theory of driven-dissipative quantum systems described by Markovian master equations generating semigroups of maps. In this setting thermal equilibrium states are replaced by nonequilibrium steady states, and dissipative perturbations are considered in addition to the Hamiltonian ones. We derive explicit expressions for the linear dynamical response functions for generalized dephasing channels and for Davies thermalizing generators. We introduce the notion of maximal harmonic response and compute it exactly for a single-qubit channel. Finally, we analyze linear response near dynamical phase transitions in quasifree open quantum systems. It is found that the effect of the dynamical phase transition shows up in a peak at the edge of the spectrum in the imaginary part of the dynamical response function.
Dynamic characteristics of very-high-rate GPS observations for seismology
NASA Astrophysics Data System (ADS)
Ebinuma, Takuji; Kato, Teruyuki
2012-05-01
GPS observations with higher than once-per-second sampling are becoming increasingly important for seismology. A number of reports have shown that very-high-rate GPS receivers are capable of capturing dynamic ground displacements from significant earthquakes. The higher output rate, however, does not necessarily mean higher frequency content of the corresponding observations. In order to examine dynamic effects on very-high-rate GPS observations, the frequency response characteristics of several geodetic GPS receivers were evaluated using a GPS signal simulator in controlled laboratory conditions. The tested receivers include Trimble Net-R8, NovAtel OEMV, and TOPCON Net-G3A. The experiment results suggest that the dynamic characteristics of the signal tracking loops put a limit on the frequency of the received signals, and all the tested receivers except for Trimble show good signal tracking performance at up to 5 Hz under dynamic stress of 2 G acceleration. The power spectral densities of the kinematic solutions obtained from the simulated seismic motion of the 2008 Iwate-Miyagi Inland earthquake ( M w 6.8) are also evaluated. The power spectral densities of both the NovAtel and TOPCON receivers agree with the simulated ground displacement at up to 5 Hz. By contrast, the Trimble receiver provides a pronounced increase in spectral energy above 2 Hz.
Finite element analysis of dynamic characteristics of diamond circular saw blades
Wang, W.; Pang, S.S.; Yang, C.; Jerro, H.D.; Mirshams, R.A.
1997-07-01
The diamond circular saw is an extensively used tool in stone, construction and road maintenance industries for sawing stone and concrete. However, its vibration and noise have been nuisances to users, and little literature is available concerning this subject. The major aspects of this investigation include: the first thirty five natural frequencies and resonant modes of circular saw blades of two different diameters are computed using the finite element method; based on these thirty five natural frequencies and resonant modes, the harmonic analysis is carried out to obtain their response spectrum; and through analyzing the computational results, some conclusions on the dynamic characteristics of diamond circular saw blades are reached.
Dynamic Characteristics and Stability Analysis of Space Shuttle Main Engine Oxygen Pump
NASA Technical Reports Server (NTRS)
Gunter, Edgar J.; Branagan, Lyle
1991-01-01
The dynamic characteristics of the Space Shuttle high pressure oxygen pump are presented. Experimental data is presented to show the vibration spectrum and response under actual engine operation and also in spin pit testing for balancing. The oxygen pump appears to be operating near a second critical speed and is sensitive to self excited aerodynamic cross coupling forces in the turbine and pump. An analysis is presented to show the improvement in pump stability by the application of turbulent flow seals, preburner seals, and pump shaft cross sectional modifications.
Dynamic Characteristics of a Model and Prototype for 3D-RC Structure
NASA Astrophysics Data System (ADS)
Moniuddin, Md. Khaja; Vasanthalakshmi, G.; Chethan, K.; Babu, R. Ramesh
2016-06-01
Infill walls provide durable and economical partitions that have relatively excellent thermal and sound insulation with high fire resistance. Monolithic infilled walls are provided within RC structures without being analyzed as a combination of concrete and brick elements, although in reality they act as a single unit during earthquakes. The performance of such structures during earthquakes has proved to be superior in comparison to bare frames in terms of stiffness, strength and energy dissipation. To know the dynamic characteristics of monolithic infill wall panels and masonry infill, modal, response spectrum and time history analyses have been carried out on a model and prototype of a 3D RC structure for a comparative study.
Dynamic characteristics of power-tower space stations with 15-foot truss bays
NASA Technical Reports Server (NTRS)
Dorsey, J. T.
1986-01-01
A power tower space station concept which generates power with photovoltaic arrays and where the truss structure has a bay size of 15 ft is described. Rigid body and flexible body dynamic characteristics are presented for a 75-kW Initial Operating Capability (IOC) and 150-kW and 300-kW growth stations. The transient response of the IOC and 300-kW growth stations to shuttle dock, orbit reboost, and mobile remote manipulator system translation loads are studied. Displacements, accelerations, and bending moments at various locations on the IOC and 300-kW growth stations are presented.
Wind response characteristics of horizontal axis wind turbines
NASA Technical Reports Server (NTRS)
Thresher, R. W.; Holley, W. E.; Jafarey, N.
1981-01-01
It was the objective of the work reported here, and in the companion paper 1 . A broader examination of wind turbine dynamic response to turbulence, and attempts to ascertain the features of turbulence that wind turbines are most sensitive to were made. A statistical description of the wind input including all three wind components and allowing linear wind gradients across the rotor disk, was used together with quasi-static aerodynamic theory and an elementary structural model involving only a few degrees of freedom. The idea was to keep the turbine model simple and show the benefits of this type of statistical wind representation before attempting to use a more complex turbine model. As far as possible, the analysis was kept in the simplest form, while still preserving key physical responses.
Corticosteroid responsiveness and clinical characteristics in childhood difficult asthma
Bossley, C.J.; Saglani, S.; Kavanagh, C.; Payne, D.N.R.; Wilson, N.; Tsartsali, L.; Rosenthal, M.; Balfour-Lynn, I.M.; Nicholson, A.G.; Bush, A.
2012-01-01
This study describes the clinical characteristics and corticosteroid responsiveness of children with difficult asthma (DA). We hypothesised that complete corticosteroid responsiveness (defined as improved symptoms, normal spirometry, normal exhaled nitric oxide fraction (FeNO) and no bronchodilator responsiveness (BDR <12%)) is uncommon in paediatric DA. We report on 102 children, mean±SD age 11.6±2.8 yrs, with DA in a cross-sectional study. 89 children underwent spirometry, BDR and FeNO before and after 2 weeks of systemic corticosteroids (corticosteroid response study). Bronchoscopy was performed after the corticosteroid trial. Of the 102 patients in the cross-sectional study, 88 (86%) were atopic, 60 (59%) were male and 52 (51%) had additional or alternative diagnoses. Out of the 81 patients in the corticosteroid response study, nine (11%) were complete responders. Of the 75 patients with symptom data available, 37 (49%) responded symptomatically, which was less likely if there were smokers in the home (OR 0.31, 95% CI 0.02–0.82). Of the 75 patients with available spirometry data, 35 (46%) had normal spirometry, with associations being BAL eosinophilia (OR 5.43, 95% CI 1.13–26.07) and high baseline forced expiratory volume in 1 s (FEV1) (OR 1.08, 95% CI 1.02–1.12). Of these 75 patients, BDR data were available in 64, of whom 36 (56%) had <12% BDR. FeNO data was available in 70 patients, of whom 53 (75%) had normal FeNO. Airflow limitation data was available in 75 patients, of whom 17 (26%) had persistent airflow limitation, which was associated with low baseline FEV1 (OR 0.93, 95% CI 0.90–0.97). Only 11% of DA children exhibited complete corticosteroid responsiveness. The rarity of complete corticosteroid responsiveness suggests alternative therapies are needed for children with DA. PMID:19541710
Dispersion of Response Times Reveals Cognitive Dynamics
Holden, John G.; Van Orden, Guy C.; Turvey, Michael T.
2013-01-01
Trial to trial variation in word pronunciation times exhibits 1/f scaling. One explanation is that human performances are consequent on multiplicative interactions among interdependent processes – interaction dominant dynamics. This article describes simulated distributions of pronunciation times in a further test for multiplicative interactions and interdependence. Individual participant distributions of ≈1100 word pronunciation times are successfully mimicked for each participant in combinations of lognormal and power law behavior. Successful hazard function simulations generalize these results to establish interaction dominant dynamics, in contrast with component dominant dynamics, as a likely mechanism for cognitive activity. PMID:19348544
Dynamical Response of Networks Under External Perturbations: Exact Results
NASA Astrophysics Data System (ADS)
Chinellato, David D.; Epstein, Irving R.; Braha, Dan; Bar-Yam, Yaneer; de Aguiar, Marcus A. M.
2015-04-01
We give exact statistical distributions for the dynamic response of influence networks subjected to external perturbations. We consider networks whose nodes have two internal states labeled 0 and 1. We let nodes be frozen in state 0, in state 1, and the remaining nodes change by adopting the state of a connected node with a fixed probability per time step. The frozen nodes can be interpreted as external perturbations to the subnetwork of free nodes. Analytically extending and to be smaller than 1 enables modeling the case of weak coupling. We solve the dynamical equations exactly for fully connected networks, obtaining the equilibrium distribution, transition probabilities between any two states and the characteristic time to equilibration. Our exact results are excellent approximations for other topologies, including random, regular lattice, scale-free and small world networks, when the numbers of fixed nodes are adjusted to take account of the effect of topology on coupling to the environment. This model can describe a variety of complex systems, from magnetic spins to social networks to population genetics, and was recently applied as a framework for early warning signals for real-world self-organized economic market crises.
Structural characteristic responses for finite element model updating of structures
NASA Astrophysics Data System (ADS)
Zhou, Linren; Wang, Lei; Ou, Jinping
2014-04-01
The field measurements of structures are very important to the structural finite element (FE) model updating because the errors and uncertainties of a FE model are corrected directly through closing the discrepancies between the analytical responses from FE model and the measurements from field testing of a structure. Usually, the accurate and reliable field measurements are very limited. Therefore, it is very important to make full use of the limited and valuable field measurements in structural model updating to achieve a best result with the lowest cost. In this paper, structural FE model updating is investigated in the point of view of solving a mathematical problem, and different amount and category of structural dynamic responses and static responses are considered as constraints to explore their effects on the updated results of different degree and types of structural damages. The numerical studies are carried out on a space truss. Accounting for the numerical results, some inherent phenomena and connections taking account of the updating parameters, output responses and the updated results are revealed and discussed. Some useful and practicable suggestions about using the field measurements for FE model updating are provided to achieve efficient and reliable results.
Response characteristics of a low-dimensional model neuron.
Cartling, B
1996-11-15
It is shown that a low-dimensional model neuron with a response time constant smaller than the membrane time constant closely reproduces the activity and excitability behavior of a detailed conductance-based model of Hodgkin-Huxley type. The fast response of the activity variable also makes it possible to reduce the model to a one-dimensional model, in particular for typical conditions. As an example, the reduction to a single-variable model from a multivariable conductance-based model of a neocortical pyramidal cell with somatic input is demonstrated. The conditions for avoiding a spurious damped oscillatory response to a constant input are derived, and it is shown that a limit-cycle response cannot occur. The capability of the low-dimensional model to approximate higher-dimensional models accurately makes it useful for describing complex dynamics of nets of interconnected neurons. The simplicity of the model facilitates analytic studies, elucidations of neurocomputational mechanisms, and applications to large-scale systems. PMID:8888611
The dynamical characteristics and wave structure of typhoon Rananim (2004)
NASA Astrophysics Data System (ADS)
Ming, Jie; Ni, Yunqi; Shen, Xinyong
2009-05-01
Typhoon Rananim (2004) was one of the severest typhoons landfalling the Chinese mainland from 1996 to 2004. It brought serious damage and induced prodigious economical loss. Using a new generation of mesoscale model, named the Weather Research and Forecasting (WRF) modeling system, with 1.667 km grid horizontal spacing on the finest nested mesh, Rananim was successfully simulated in terms of track, intensity, eye, eyewall, and spiral rainbands. We compared the structures of Rananim to those of hurricanes in previous studies and observations to assess the validity of simulation. The three-dimensional (3D) dynamic and thermal structures of eye and eyewall were studied based on the simulated results. The focus was investigation of the characteristics of the vortex Rossby waves in the inner-core region. We found that the Rossby vortex waves propagate azimuthally upwind against the azimuthal mean tangential flow around the eyewall, and their period was longer than that of an air parcel moving within the azimuthal mean tangential flow. They also propagated outward against the boundary layer inflow of the azimuthal mean vortex. Futhermore, we studied the connection between the spiral potential vorticity (PV) bands and spiral rainbands, and found that the vortex Rossby waves played an important role in the formation process of spiral rainbands.
Measurement of human pilot dynamic characteristics in flight simulation
NASA Technical Reports Server (NTRS)
Reedy, James T.
1987-01-01
Fast Fourier Transform (FFT) and Least Square Error (LSE) estimation techniques were applied to the problem of identifying pilot-vehicle dynamic characteristics in flight simulation. A brief investigation of the effects of noise, input bandwidth and system delay upon the FFT and LSE techniques was undertaken using synthetic data. Data from a piloted simulation conducted at NASA Ames Research Center was then analyzed. The simulation was performed in the NASA Ames Research Center Variable Stability CH-47B helicopter operating in fixed-basis simulator mode. The piloting task consisted of maintaining the simulated vehicle over a moving hover pad whose motion was described by a random-appearing sum of sinusoids. The two test subjects used a head-down, color cathode ray tube (CRT) display for guidance and control information. Test configurations differed in the number of axes being controlled by the pilot (longitudinal only versus longitudinal and lateral), and in the presence or absence of an important display indicator called an 'acceleration ball'. A number of different pilot-vehicle transfer functions were measured, and where appropriate, qualitatively compared with theoretical pilot- vehicle models. Some indirect evidence suggesting pursuit behavior on the part of the test subjects is discussed.
Characteristics of seismoelectric interface responses at dipping boundaries
NASA Astrophysics Data System (ADS)
Kröger, B.; Kemna, A.
2012-04-01
When crossing an interface between two layers with different petrophysical properties, a seismic wave generates a time-varying charge separation which acts as a dipole radiating electromagnetic energy independently of the seismic wave. If we consider a monochromatic seismic source located above a horizontal interface between such media, the seismic wave traverses the interface and causes relative displacement of ions at the matrix-fluid interface in the pore space. The resulting electric field is due to the streaming current imbalance at the interface. This is equivalent to the case of an electrical dipole oscillating in phase with the seismic wave along such boundary. As a consequence, electromagnetic disturbances are radiated away from the dipole source and can be recorded at various receiver lines. This seismic-to-electromagnetic field conversion at petrophysical boundaries in the 1st Fresnel zone is the so-called seismoelectric interface response. Conceptual field models and theoretical modelling indicate that the interface response should be a multipole electrical source. Higher-order terms will diminish more rapidly with distance and therefore will leave the dipole term to dominate. Thus, a seismoelectric interface response emanating from a horizontal boundary in a homogeneous half-space is expected to exhibit symmetry and amplitude characteristics similar to those of a vertical electric dipole (VED) centred on the interface directly below the shot point. However, no general theoretical predictions concerning the characteristics, the shape and the morphology of the VED induced by seismic waves at dipping interfaces can be found in the literature. To gain insight into the spatio-temporal occurrence and evolution of the seismoelectric interface response for dipping interfaces we run several numerical simulations using different petrophysical parameter set-ups. For the modelling, we make use of a simplified time-domain formulation of the coupled physical problem
Response characteristics of esophageal balloon catheters handmade using latex and nonlatex materials
Cross, Troy J; Lalande, Sophie; Hyatt, Robert E; Johnson, Bruce D
2015-01-01
The measurement of esophageal pressure allows for the calculation of several important and clinically useful parameters of respiratory mechanics. Esophageal pressure is often measured with balloon-tipped catheters. These catheters may be handmade from natural latex condoms and polyethylene tubing. Given the potential of natural latex to cause allergic reaction, it is important to determine whether esophageal catheter balloons can be fabricated, by hand, using nonlatex condoms as construction materials. To determine the static and dynamic response characteristics of esophageal balloon catheters handmade from latex and nonlatex materials, six esophageal catheter balloons were constructed from each of the following condom materials: natural latex, synthetic polyisoprene, and polyurethane (18 total). Static compliance and working volume range of each balloon catheter was obtained from their pressure-volume characteristics in water. The dynamic response of balloon catheters were measured via a pressure “step” test, from which a third-order underdamped transfer function was modeled. The dynamic ranges of balloon catheters were characterized by the frequencies corresponding to ±5% amplitude- and phase-distortion (fA5% and fφ5%). Balloon catheters handmade from polyurethane condoms displayed the smallest working volume range and lowest static balloon compliance. Despite this lower compliance, fA5% and fφ5% were remarkably similar between all balloon materials. Our findings suggest that polyisoprene condoms are an ideal nonlatex construction material to use when fabricating esophageal catheter balloons by hand. PMID:26077619
Coastal Bacterioplankton Community Dynamics in Response to a Natural Disturbance
Rappé, Michael S.
2013-01-01
In order to characterize how disturbances to microbial communities are propagated over temporal and spatial scales in aquatic environments, the dynamics of bacterial assemblages throughout a subtropical coastal embayment were investigated via SSU rRNA gene analyses over an 8-month period, which encompassed a large storm event. During non-perturbed conditions, sampling sites clustered into three groups based on their microbial community composition: an offshore oceanic group, a freshwater group, and a distinct and persistent coastal group. Significant differences in measured environmental parameters or in the bacterial community due to the storm event were found only within the coastal cluster of sampling sites, and only at 5 of 12 locations; three of these sites showed a significant response in both environmental and bacterial community characteristics. These responses were most pronounced at sites close to the shoreline. During the storm event, otherwise common bacterioplankton community members such as marine Synechococcus sp. and members of the SAR11 clade of Alphaproteobacteria decreased in relative abundance in the affected coastal zone, whereas several lineages of Gammaproteobacteria, Betaproteobacteria, and members of the Roseobacter clade of Alphaproteobacteria increased. The complex spatial patterns in both environmental conditions and microbial community structure related to freshwater runoff and wind convection during the perturbation event leads us to conclude that spatial heterogeneity was an important factor influencing both the dynamics and the resistance of the bacterioplankton communities to disturbances throughout this complex subtropical coastal system. This heterogeneity may play a role in facilitating a rapid rebound of regions harboring distinctly coastal bacterioplankton communities to their pre-disturbed taxonomic composition. PMID:23409156
Electro-response characteristic of starch hydrogel crosslinked with Glutaraldehyde.
Gao, Ling-xiang; Chen, Jian-li; Han, Xue-wu; Yan, Shu-xian; Zhang, Yan; Zhang, Wei-qiang; Gao, Zi-wei
2015-01-01
The facile synthesis of the starch hydrogel with anisotropic microstructure and dynamic behaviors was developed in the presence (A-gel) and absence of DC electric field (B-gel). The microstructures of hydrogels were characterized by environmental scanning electron microscope. Their electro-responsive property of hydrogels was investigated with their storage modulus (G'). The result demonstrates that the G' of A-gel is greater than that of B-gel, and the modulus of A-gel increases along with the external field, which signifies positive electroresponse. In addition, the G' of A-gel and B-gel ((G'(A) and G'(B)) also continuously increases with increasing starch concentration, whereas both the maximum of modulus increment (ΔG' = G'(A)−G'(B) ) and that of modulus increment sensitivity (ΔG'/G'(B)) occur with the starch weight fraction at around 36.5%. To enhance the electro-responsive effects of the hydrogels, dielectric particles were dispersed in the hydrogel. It is found that BaTiO3/chitosan core-shell composite particles significantly enhance the electroresponse of the hydrogel. The mechanism of the electro-response mode is proposed. PMID:25849098
A novel approach to detecting breathing-fatigue cracks based on dynamic characteristics
NASA Astrophysics Data System (ADS)
Yan, Guirong; De Stefano, Alessandro; Matta, Emiliano; Feng, Ruoqiang
2013-01-01
During the service life of structures, breathing-fatigue cracks may occur in structural members due to dynamic loadings acting on them. These fatigue cracks, if undetected, might lead to a catastrophic failure of the whole structural system. Although a number of approaches have been proposed to detect breathing-fatigue cracks, some of them appear rather sophisticated or expensive (requiring complicated equipment), and others suffer from a lack of sensitivity. In this study, a simple and efficient approach to detecting breathing-fatigue cracks is developed based on dynamic characteristics of breathing cracks. First, considering that breathing cracks introduce bilinearity into structures, a simple system identification method for bilinear systems is proposed by taking best advantage of dynamic characteristics of bilinear systems. This method transfers nonlinear system identification into linear system identification by dividing impulse or free-vibration responses into different parts corresponding to each stiffness region according to the stiffness interface. In this way, the natural frequency of each region can be identified using any modal identification approach applicable to linear systems. Second, the procedure for identifying the existence of breathing fatigue cracks and quantifying the cracks qualitatively is proposed by looking for the difference in the identified natural frequency between regions. Third, through introducing Hilbert transform, the proposed procedure is extended to identify fatigue cracks in piecewise-nonlinear systems. The proposed system identification method and crack detection procedure have been successfully validated by numerical simulations and experimental tests.
Static & Dynamic Response of 3D Solids
Energy Science and Technology Software Center (ESTSC)
1996-07-15
NIKE3D is a large deformations 3D finite element code used to obtain the resulting displacements and stresses from multi-body static and dynamic structural thermo-mechanics problems with sliding interfaces. Many nonlinear and temperature dependent constitutive models are available.
Dispersion of Response Times Reveals Cognitive Dynamics
ERIC Educational Resources Information Center
Holden, John G.; Van Orden, Guy C.; Turvey, Michael T.
2009-01-01
Trial-to-trial variation in word-pronunciation times exhibits 1/f scaling. One explanation is that human performances are consequent on multiplicative interactions among interdependent processes-interaction dominant dynamics. This article describes simulated distributions of pronunciation times in a further test for multiplicative interactions and…
Kinematic/Dynamic Characteristics for Visual and Kinesthetic Virtual Environments
NASA Technical Reports Server (NTRS)
Bortolussi, Michael R. (Compiler); Adelstein, B. D.; Gold, Miriam
1996-01-01
Work was carried out on two topics of principal importance to current progress in virtual environment research at NASA Ames and elsewhere. The first topic was directed at maximizing the temporal dynamic response of visually presented Virtual Environments (VEs) through reorganization and optimization of system hardware and software. The final results of this portion of the work was a VE system in the Advanced Display and Spatial Perception Laboratory at NASA Ames capable of updating at 60 Hz (the maximum hardware refresh rate) with latencies approaching 30 msec. In the course of achieving this system performance, specialized hardware and software tools for measurement of VE latency and analytic models correlating update rate and latency for different system configurations were developed. The second area of activity was the preliminary development and analysis of a novel kinematic architecture for three Degree Of Freedom (DOF) haptic interfaces--devices that provide force feedback for manipulative interaction with virtual and remote environments. An invention disclosure was filed on this work and a patent application is being pursued by NASA Ames. Activities in these two areas are expanded upon below.
Identification of dynamic characteristics of flexible rotors as dynamic inverse problem
NASA Technical Reports Server (NTRS)
Roisman, W. P.; Vajingortin, L. D.
1991-01-01
The problem of dynamic and balancing of flexible rotors were considered, which were set and solved as the problem of the identification of flexible rotor systems, which is the same as the inverse problem of the oscillation theory dealing with the task of the identifying the outside influences and system parameters on the basis of the known laws of motion. This approach to the problem allows the disclosure the picture of disbalances throughout the rotor-under-test (which traditional methods of flexible rotor balancing, based on natural oscillations, could not provide), and identify dynamic characteristics of the system, which correspond to a selected mathematical model. Eventually, various methods of balancing were developed depending on the special features of the machines as to their design, technology, and operation specifications. Also, theoretical and practical methods are given for the flexible rotor balancing at far from critical rotation frequencies, which does not necessarily require the knowledge forms of oscillation, dissipation, and elasticity and inertia characteristics, and to use testing masses.
Effects of cockpit lateral stick characteristics on handling qualities and pilot dynamics
NASA Technical Reports Server (NTRS)
Mitchell, David G.; Aponso, Bimal L.; Klyde, David H.
1992-01-01
This report presents the results of analysis of cockpit lateral control feel-system studies. Variations in feel-system natural frequency, damping, and command sensing reference (force and position) were investigated, in combination with variations in the aircraft response characteristics. The primary data for the report were obtained from a flight investigation conducted with a variable-stability airplane, with additional information taken from other flight experiments and ground-based simulations for both airplanes and helicopters . The study consisted of analysis of handling qualities ratings and extraction of open-loop, pilot-vehicle describing functions from sum-of-sines tracking data, including, for a limited subset of these data, the development of pilot models. The study confirms the findings of other investigators that the effects on pilot opinion of cockpit feel-system dynamics are not equivalent to a comparable level of added time delay, and until a more comprehensive set of criteria are developed, it is recommended that feel-system dynamics be considered a delay-inducing element in the aircraft response. The best correlation with time-delay requirements was found when the feel-system dynamics were included in the delay measurements, regardless of the command reference. This is a radical departure from past approaches.
DYNAMICAL RESPONSE OF QUASI ID MOTT INSULATORS.
ESSLER,F.H.L.TSVELIK,A.M.
2004-01-14
At low energies certain one dimensional Mott insulators can be described in terms of an exactly solvable quantum field theory, the U(1) Thirring model. Using exact results derived from integrability we determine dynamical properties like the frequency dependent optical conductivity and the single-particle Green's function. We discuss the effects of a small temperature and the effects on interchain tunneling in a model of infinitely many weakly coupled chains.
Maternal characteristics influence response to DHA during pregnancy.
Gould, J F; Anderson, A J; Yelland, L N; Gibson, R A; Makrides, M
2016-05-01
We explored the degree to which maternal and offspring outcomes resulting from consuming prenatal docosahexaenoic acid (DHA, 800mg/day) in a clinical trial were influenced by maternal characteristics. Among non-smokers, women who received DHA had heavier babies (adjusted mean difference (MD)=99g 95% CI 45-153, p<0.01; interaction p=0.01) and fewer low birth weight babies than control women (adjusted relative risk=0.43 95% CI 0.25-0.74, p<0.01; interaction p=0.01). From women who had not completed further education, children in the DHA group had higher cognitive scores at 18 months compared with control children (adjusted MD=3.15 95% CI 0.93-5.37, p=0.01; interaction p<0.01). Conversely, the children of women who completed further education in the DHA group had lower language scores than control children (adjusted MD -2.82 95% CI -4.90 to -0.73, p=0.01; interaction p=0.04). Our results support the notion that responsiveness to prenatal DHA may depend on the characteristics of specific population subgroups. PMID:27154359
Dynamics of T cell responses after stroke.
Gill, Dipender; Veltkamp, Roland
2016-02-01
T cells are integral to the pathophysiology of stroke. The initial inflammatory cascade leads to T cell migration, which results in deleterious and protective effects mediated through CD4(+), CD(8)+, γδ T cells and regulatory T cells, respectively. Cytokines are central to the T cell responses, with key roles established for TNF-α, IFN-γ, IL-17, IL-21 and IL-10. Through communication with the systemic immune system via neural and hormonal pathways, there is also transient immunosuppression after severe strokes. With time, the inflammatory process eventually transforms to one more conducive of repair and recovery, though some evidence also suggests ongoing chronic inflammation. The role of antigen-specific T cell responses requires further investigation. As our understanding develops, there is increasing scope to modulate the T cell response after stroke. PMID:26452204
Response of DP 600 products to dynamic impact loads
NASA Astrophysics Data System (ADS)
Clark, Deidra Darcell
The objective of this study was to compare the microstructural response of various DP 600 products subjected to low velocity, dynamic impact tests, typically encountered in a car crash. Since the response of steel is sensitive to its microstructure as controlled by the alloying elements, phase content, and processing; various DP 600 products may respond differently to crashes. The microstructure before and after dynamic impact deformation at 5 and 10 mph was characterized with regards to grain size, morphology, and phase content among vendors A, B, and C to evaluate efficiency in absorbing energy mechanisms during a crash simulated by dynamic impact testing in a drop tower.
Analysis of the dynamic characteristics of a slant-cracked cantilever beam
NASA Astrophysics Data System (ADS)
Ma, Hui; Zeng, Jin; Lang, Ziqiang; Zhang, Long; Guo, Yuzhu; Wen, Bangchun
2016-06-01
In this study, the dynamic characteristics of a slant-cracked cantilever beam are studied based on a new finite element (FE) model where both plane and beam elements are used to reduce the computational costs. Simulation studies show that the proposed model has the same system natural frequencies and vibration responses as those in the pure plane element model but is computationally more efficient. Based on the new model, the effects of loads such as gravity Fg, excitation force amplitude F0 and direction angles of excitation force φ, and crack parameters including slant crack angle θ, dimensionless crack depth s and dimensionless crack location p, on system dynamics have been analyzed. The results indicate that (1) the gravity has a more significant effect on the sub-harmonic resonance responses than on the super-harmonic resonance and resonance responses; (2) The amplitudes of the system responses at both excitation force frequencies fe and its harmonics such as 2fe and 3fe increase almost linearly with the increase of the excitation force amplitude F0; (3) Under the constant excitation force in the flexural direction, the tensile and compressive forces along the longitudinal direction can lead to opposite breathing behaviors of the crack within the super-harmonic and sub-harmonic resonance frequency regions; (4) Vibration is most severe under the straight crack angle (θ=90°) and near the straight crack angle such as θ=100° and 110°, and the vibration responses under smaller or larger crack angles such as θ=30° and θ=150° become weaker; (5) The resonance at 2fe is sensitive to the faint crack signals when s is small and p is large. In addition, the significant vibration responses at the multiple frequency of 3fe and the fractional frequency of 0.5fe can be regarded as a distinguishable feature of the serious crack with large s and small p.
Monitoring response to disturbance in dynamic rangelands
Technology Transfer Automated Retrieval System (TEKTRAN)
Arid and semi-arid rangelands worldwide provide important ecosystem services and see a diversity of land uses. To maintain the health of these lands, it is necessary to monitor rangeland conditions in response to management and disturbance. Spatial patterns from disturbance are superimposed on patte...
Dynamic brittle material response based on a continuum damage model
Chen, E.P.
1994-12-31
The response of brittle materials to dynamic loads was studied in this investigation based on a continuum damage model. Damage mechanism was selected to be interaction and growth of subscale cracks. Briefly, the cracks are activated by bulk tension and the density of activated cracks are described by a Weibull statistical distribution. The moduli of a cracked solid derived by Budiansky and O`Connell are then used to represent the global material degradation due to subscale cracking. This continuum damage model was originally developed to study rock fragmentation and was modified in the present study to improve on the post-limit structural response. The model was implemented into a transient dynamic explicit finite element code PRONTO 2D and then used for a numerical study involving the sudden stretching of a plate with a centrally located hole. Numerical results characterizing the dynamic responses of the material were presented. The effect of damage on dynamic material behavior was discussed.
The Response Dynamics of Recognition Memory: Sensitivity and Bias
ERIC Educational Resources Information Center
Koop, Gregory J.; Criss, Amy H.
2016-01-01
Advances in theories of memory are hampered by insufficient metrics for measuring memory. The goal of this paper is to further the development of model-independent, sensitive empirical measures of the recognition decision process. We evaluate whether metrics from continuous mouse tracking, or response dynamics, uniquely identify response bias and…
Dismissing Attachment Characteristics Dynamically Modulate Brain Networks Subserving Social Aversion
Krause, Anna Linda; Borchardt, Viola; Li, Meng; van Tol, Marie-José; Demenescu, Liliana Ramona; Strauss, Bernhard; Kirchmann, Helmut; Buchheim, Anna; Metzger, Coraline D.; Nolte, Tobias; Walter, Martin
2016-01-01
our observation of direct prediction of neuronal responses by individual attachment and trauma characteristics and reversely prediction of subjective experience by intrinsic functional connections. We consider these findings of activation of within-network and between-network connectivity modulated by inter-individual differences as substantial for the understanding of interpersonal processes, particularly in clinical settings. PMID:27014016
Frequency-response identification of XV-15 tilt-rotor aircraft dynamics
NASA Technical Reports Server (NTRS)
Tischler, Mark B.
1987-01-01
The timely design and development of the next generation of tilt-rotor aircraft (JVX) depend heavily on the in-depth understanding of existing XV-15 dynamics and the availability of fully validated simulation models. Previous studies have considered aircraft and simulation trim characteristics, but analyses of basic flight vehicle dynamics were limited to qualitative pilot evaluation. The present study has the following objectives: documentation and evaluation of XV-15 bare-airframe dynamics; comparison of aircraft and simulation responses; and development of a validated transfer-function description of the XV-15 needed for future studies. A nonparametric frequency-response approach is used which does not depend on assumed model order or structure. Transfer-function representations are subsequently derived which fit the frequency responses in the bandwidth of greatest concern for piloted handling-qualities and control-system applications.
On the dynamic response of four polymers
NASA Astrophysics Data System (ADS)
Bourne, N. K.; Gray, G. T., III; Millett, J. C. F.
2003-09-01
Il is a pressing objective to understand the mechanical behaviour of polymeric materiais at high strain rate for a range of industrial and defence applications. Some are used as the binder phase in plastic bonded explosives (PBXs) and propellants. Others are used either as components for structures or as the binder phase in various composite Systems. Such materials need to be understood so that their response may be understood and constitutive descriptions constructed. This work presents experimental data focused at the evaluation of the equation-of-statc (EOS) and strength behaviour of four selected polymers. The equation of state and the shear strength of each polymer were measured as a function of impact stress and this gives insight into the role of the microstructure and its relation to response.
Sediment characteristics and transportation dynamics of the Ganga River
NASA Astrophysics Data System (ADS)
Singh, Munendra; Singh, Indra Bir; Müller, German
2007-04-01
Understanding of river systems that have experienced various forcing mechanisms such as climate, tectonics, sea level fluctuations and their linkages is a major concern for fluvial scientists. The 2525-km-long Ganga River derives its fluvial flux from northern part of the Indian subcontinent and drops in the Ganga-Brahmaputra delta and the Bengal fan regions. This paper presents a study of the Ganga River sediments for their textural properties, grainsize characteristics, and transportation dynamics. A suite of recently deposited sediments (189 bedload samples and 27 suspended load samples) of the river and its tributaries was collected from 63 locations. Dry and wet sieve methods of grainsize analysis were performed and Folk and Ward's parameters were calculated. Transportation dynamics of the sediment load was assessed by means of channel hydrology, flow/sediment rating curves, bedform mechanics, grainsize images, and cumulative curves. Textural properties of the bedload sediments of the Ganga River tributaries originating from the Himalaya orogenic belt, the northern Indian craton and the Ganga alluvial plain regions are characterised by the predominance of fine to very fine sand, medium to fine sand, and very fine sand to clay, respectively. Downstream textural variations in the bedload and suspended load sediments of the Ganga River are, therefore, complex and are strongly influenced by lateral sediment inputs by the tributaries and channel slope. At the base of the Himalaya, a very sharp gravel-sand transition is present in which median grainsize of bedload sediments decreases from over - 0.16 Φ to 2.46 Φ within a distance of 35 km. Downstream decline in mean grainsize of bedload sediments in the upper Ganga River within the alluvial plain can be expressed by an exponential formula as: mean grainsize (in Φ) = 0.0024 × Distance (in kilometres from the Himalayan front) + 1.29. It is a result of selective transport phenomena rather than of abrasion, the
NGC1300 dynamics - II. The response models
NASA Astrophysics Data System (ADS)
Kalapotharakos, C.; Patsis, P. A.; Grosbøl, P.
2010-10-01
We study the stellar response in a spectrum of potentials describing the barred spiral galaxy NGC1300. These potentials have been presented in a previous paper and correspond to three different assumptions as regards the geometry of the galaxy. For each potential we consider a wide range of Ωp pattern speed values. Our goal is to discover the geometries and the Ωp supporting specific morphological features of NGC1300. For this purpose we use the method of response models. In order to compare the images of NGC1300 with the density maps of our models, we define a new index which is a generalization of the Hausdorff distance. This index helps us to find out quantitatively which cases reproduce specific features of NGC1300 in an objective way. Furthermore, we construct alternative models following a Schwarzschild-type technique. By this method we vary the weights of the various energy levels, and thus the orbital contribution of each energy, in order to minimize the differences between the response density and that deduced from the surface density of the galaxy, under certain assumptions. We find that the models corresponding to Ωp ~ 16 and 22 kms-1kpc-1 are able to reproduce efficiently certain morphological features of NGC1300, with each one having its advantages and drawbacks. Based on observations collected at the European Southern Observatory, Chile: programme ESO 69.A-0021. E-mail: ckalapot@phys.uoa.gr (CK); patsis@academyofathens.gr (PAP); pgrosbol@eso.org (PG)
Dynamic response of a piezoelectric flapping wing
NASA Astrophysics Data System (ADS)
Kumar, Alok; Khandwekar, Gaurang; Venkatesh, S.; Mahapatra, D. R.; Dutta, S.
2015-03-01
Piezo-composite membranes have advantages over motorized flapping where frequencies are high and certain coupling between bending and twisting is useful to generate lift and forward flight. We draw examples of fruit fly and bumble bee. Wings with Piezo ceramic PZT coating are realized. The passive mechanical response of the wing is characterized experimentally and validated using finite element simulation. Piezoelectric actuation with uniform electrode coating is characterized and optimal frequencies for flapping are identified. The experimental data are used in an empirical model and advanced ratio for a flapping insect like condition for various angular orientations is estimated.
Monitoring the intracellular calcium response to a dynamic hypertonic environment
NASA Astrophysics Data System (ADS)
Huang, Xiaowen; Yue, Wanqing; Liu, Dandan; Yue, Jianbo; Li, Jiaqian; Sun, Dong; Yang, Mengsu; Wang, Zuankai
2016-03-01
The profiling of physiological response of cells to external stimuli at the single cell level is of importance. Traditional approaches to study cell responses are often limited by ensemble measurement, which is challenging to reveal the complex single cell behaviors under a dynamic environment. Here we report the development of a simple microfluidic device to investigate intracellular calcium response to dynamic hypertonic conditions at the single cell level in real-time. Interestingly, a dramatic elevation in the intracellular calcium signaling is found in both suspension cells (human leukemic cell line, HL-60) and adherent cells (lung cancer cell line, A549), which is ascribed to the exposure of cells to the hydrodynamic stress. We also demonstrate that the calcium response exhibits distinct single cell heterogeneity as well as cell-type-dependent responses to the same stimuli. Our study opens up a new tool for tracking cellular activity at the single cell level in real time for high throughput drug screening.
Slow dynamics in features of synchronized neural network responses
Haroush, Netta; Marom, Shimon
2015-01-01
In this report trial-to-trial variations in the synchronized responses of neural networks are explored over time scales of minutes, in ex-vivo large scale cortical networks. We show that sub-second measures of the individual synchronous response, namely—its latency and decay duration, are related to minutes-scale network response dynamics. Network responsiveness is reflected as residency in, or shifting amongst, areas of the latency-decay plane. The different sensitivities of latency and decay durations to synaptic blockers imply that these two measures reflect aspects of inhibitory and excitatory activities. Taken together, the data suggest that trial-to-trial variations in the synchronized responses of neural networks might be related to effective excitation-inhibition ratio being a dynamic variable over time scales of minutes. PMID:25926787
NASA Astrophysics Data System (ADS)
Ainalis, Daniel; Rouillard, Vincent; Sek, Michael
2016-06-01
This paper describes the application of a practical analytical technique based on the random decrement method to estimate the rigid sprung mass dynamic characteristics (frequency response function) of road vehicles using only vibration response data during constant-speed operation. A brief history and development of the random decrement technique is presented, along with a summary of work undertaken on optimal parameter selection to establish the random decrement signature. Two approaches to estimate the dynamic characteristics from the random decrement signature are described and evaluated. A custom, single-wheeled vehicle (physical quarter car) was commissioned to undertake a series of on-the-road experiments at various nominally constant operating speeds. The vehicle, also instrumented as an inertial profilometer, simultaneously measured the longitudinal pavement profile to establish the vehicle's actual dynamic characteristics during operation. The main outcome of the paper is that the random decrement technique can be used to provide accurate estimates of the sprung mass mode of the vehicle's dynamic characteristics for both linear and nonlinear suspension systems of an idealised vehicle.
A set of measurement system for the dynamic laser scatter characteristics of target
NASA Astrophysics Data System (ADS)
Wei, Xiangquan; Huang, Jianming; Xiao, Yuzhi; Fan, Xiaoli
2015-12-01
It is an important measure to observe target by using laser sensor in the field of target detection. Exact and reliable dynamic laser scatter characteristics of observing target, can not only be used for the design and development of laser sensor as well as the research of algorithm for target capture, recognition and tracking, but also can offer reference bases for the test flow programming. A set of simulation, measurement system for the dynamic laser scatter characteristics of observing target is introduced in this paper. The simulation problem of dynamic laser scatter characteristics of observing target is solved, under the circumstance of laboratory with different azimuth angle and pitch angle of observation. The dynamic laser scatter characteristics of observing target can be obtained directly by such system, the test data can be used for the verification of the analyzing model for the laser scatter characteristics of observing target, and can also offer basis for the development of laser detecting sensor.
Dose response characteristics of special opti-chromic waveguides
NASA Astrophysics Data System (ADS)
Humprerys, K. C.; Kantz, A. D.
In 1981 Kronenberg, McLaughlin, and Siebentritt proposed measurement of radiation dosage using optical waveguides with leuco dye solutions. Based on this work, an opti-chromic system was proposed at the Fourth International Meeting on Radiation Processing. This opti-chromic system has been evaluated by McLaughlin and Radak. The opti-chromic waveguide system may be even more valuable for other applications which involve measurements with special requirements and configurations. The linearity of the radiation response can be enhanced by proper selection of leuco dye concentration, waveguide materials, organic activator solvents, and trace chemical additives. This paper presents experimental data resulting from an examination of the organic solvents TEP, DMSO, and n-propyl alcohol in relationship to stability, temperature characteristics, and radiation chemistry. The experimental data indicates that by varying the types and combinations of organic solvents, special opti-chromic waveguides can be fabricated to measure various radiation ranges under a variety of temperature ranges which have stability over time.
Dynamic Characteristics of Penor Peat Using MASW Method
NASA Astrophysics Data System (ADS)
Zainorabidin, A.; Said, M. J. M.
2016-07-01
The dynamic behaviour of soil affected the mechanical properties of soil such as shear wave velocity, shear modulus, damping ratio and poisson's ratio [1] which is becoming important aspect need to be considered for structures influences by dynamic movement. This study is to determine the dynamic behaviour of Penor peat such as shear wave velocity using MASW and estimation its shear modulus. Peat soils are very problematic soils since it's have high compressibility, low shear strength, high moisture content and low bearing capacity which is very not suitable materials to construct any foundation structures. Shear wave velocity ranges between 32.94 - 95.89 m/s and shear modulus are ranging between 0.93 - 8.01 MPa. The differences of both dynamic properties are due to the changes of peat density and affected by the fibre content, organic content, degree of degradation and moisture content.
Polar cusp: optical and particle characteristics-dynamics
Sandholt, P.E.; Egeland, A.; Asheim, S.; Lybekk, B.; Hardy, D.A.
1985-01-01
Photometric observations from two stations on Svalbard, Norway, were used to map the location and dynamics of polar-cusp auroras. Coordinated observations of low-energy electron precipitation from satellite HILAT and optical observations from the ground are discussed. Cases are presented showing the dynamical behavior of cusp auroras and the local magnetic field related to changes in the interplanetary magnetic field (IMF) and irregularities in the solar wind plasma. Dynamical phenomena with different time scales are studied. South and northward expansions of the midday sector of the auroral oval are discussed in relation to IMF variations and geomagnetic substorm activity. Intensifications and rapid poleward motions of discrete auroral structures in the cusp region are shown to be associated with local Pi type magnetic pulsations, each event lasting a few minutes. These small scale dynamical phenomena are discussed in relation to different models of plasma penetration across the dayside magnetopause, from the magnetosheath to the polar cusp region of the magnetosphere.
Dynamic Characteristics of Micro-Beams Considering the Effect of Flexible Supports
Zhong, Zuo-Yang; Zhang, Wen-Ming; Meng, Guang
2013-01-01
Normally, the boundaries are assumed to allow small deflections and moments for MEMS beams with flexible supports. The non-ideal boundary conditions have a significant effect on the qualitative dynamical behavior. In this paper, by employing the principle of energy equivalence, rigorous theoretical solutions of the tangential and rotational equivalent stiffness are derived based on the Boussinesq's and Cerruti's displacement equations. The non-dimensional differential partial equation of the motion, as well as coupled boundary conditions, are solved analytically using the method of multiple time scales. The closed-form solution provides a direct insight into the relationship between the boundary conditions and vibration characteristics of the dynamic system, in which resonance frequencies increase with the nonlinear mechanical spring effect but decrease with the effect of flexible supports. The obtained results of frequencies and mode shapes are compared with the cases of ideal boundary conditions, and the differences between them are contrasted on frequency response curves. The influences of the support material property on the equivalent stiffness and resonance frequency shift are also discussed. It is demonstrated that the proposed model with the flexible supports boundary conditions has significant effect on the rigorous quantitative dynamical analysis of the MEMS beams. Moreover, the proposed analytical solutions are in good agreement with those obtained from finite element analyses.
Development of study on the dynamic characteristics of deep water mooring system
NASA Astrophysics Data System (ADS)
Tang, You-Gang; Zhang, Su-Xia; Zhang, Ruo-Yu; Liu, Hai-Xiao
2007-09-01
To meet the needs of those exploiting deepwater resources, TLP and SPAR platforms are used in some areas and are considered excellent platforms in deep water. However, many problems remain to be resolved. The design of mooring systems is a key issue for deep water platforms. Environmental loads in deep water effect the physical characteristics of mooring line materials. The configuration and analysis of mooring systems involve nonlinearity due to this fluid-solid coupling, nonlinear hydrodynamic forces, and their effects on stability of motion. In this paper, some pivotal theories and technical questions are presented, including modeling of mooring lines, the theory and method of coupled dynamics analysis on the mooring system, and the development of methodologies for the study of nonlinear dynamics of mooring systems. Further study on mooring systems in deep water are recommended based on current knowledge, particularly dynamic parameters of different materials and cable configuration, interactions between seabed and cable, mechanisms of mooring system response induced by taut/slack mooring cables, discontinuous stiffness due to system materials, mooring construction, and motion instability, etc.
The isolation characteristics of an archetypal dynamical model with stable-quasi-zero-stiffness
NASA Astrophysics Data System (ADS)
Hao, Zhifeng; Cao, Qingjie
2015-03-01
In this paper, a single-degree-of-freedom geometrically nonlinear oscillator with stable-quasi-zero-stiffness (SQZS) is presented, which can be extensively applied in vibration isolation due to its high static load bearing capacity and low dynamic stiffness. This model comprises a lumped mass denoeing the isolated object and a pair of horizontal springs providing negative stiffness paralleled with a vertical linear spring to bear the load. The equation of motion of the system is formulated with an originally irrational nonlinearity based upon SD oscillator instead of the conventionally approximate Duffing system of polynomial type, which will produce results with a high precision unquestionably, especially for the prediction of a large displacement behaviour. The frequency response characteristics particularly for transmissibility of the model, subjected to harmonic forcing and vibrating base, are obtained by using an extended averaging approach to achieve the parameter optimization for maximum frequency band of isolation. Furthermore, numerical simulations are carried out to detect the complex dynamical phenomena of periodic, chaotic motions and coexistence of multiple solutions, and so on, in addition to verifying the analytical results. Finally, an interesting strategy is proposed to extend the frequency band of isolation by controlling the initial value within the attraction basin of a small amplitude attractor, which can be utilized for an effective isolation. The results presented herein provide an insight of dynamics into the SQZS mechanism for its application in vibration engineering.
Prolonged persistence of measles virus RNA is characteristic of primary infection dynamics
Lin, Wen-Hsuan W.; Kouyos, Roger D.; Adams, Robert J.; Grenfell, Bryan T.; Griffin, Diane E.
2012-01-01
Measles virus (MeV) is the poster child for acute infection followed by lifelong immunity. However, recent work shows the presence of MeV RNA in multiple sites for up to 3 mo after infection in a proportion of infected children. Here, we use experimental infection of rhesus macaques to show that prolonged RNA presence is characteristic of primary infection. We found that viral RNA persisted in the blood, respiratory tract, or lymph nodes four to five times longer than the infectious virus and that the clearance of MeV RNA from blood happened in three phases: rapid decline coincident with clearance of infectious virus, a rebound phase with increases up to 10-fold, and a phase of slow decrease to undetectable levels. To examine the effect of individual host immune factors on MeV load dynamics further, we developed a mathematical model that expressed viral replication and elimination in terms of the strength of MeV-specific T-cell responses, antibody responses, target cell limitations, and immunosuppressive activity of regulatory T cells. Based on the model, we demonstrate that viral dynamics, although initially regulated by T cells, require antibody to eliminate viral RNA. These results have profound consequences for our view of acute viral infections, the development of prolonged immunity, and, potentially, viral evolution. PMID:22872860
Dynamic response of trapped ultracold bosons on optical lattices
Batrouni, G.G.; Assaad, F.F.; Scalettar, R.T.; Denteneer, P.J.H.
2005-09-15
We study the dynamic response of ultracold bosons trapped in one-dimensional optical lattices using Quantum Monte Carlo simulations of the boson Hubbard model with a confining potential. The dynamic structure factor reveals the inhomogeneous nature of the low temperature state, which contains coexisting Mott insulator and superfluid regions. We present new evidence for local quantum criticality and discuss implications for the experimental excitation spectrum of {sup 87}Rb atoms confined in one dimension.
Capturing the dynamic nascent transcriptome during acute cellular responses: The serum response
Kirkconnell, Killeen S.; Paulsen, Michelle T.; Magnuson, Brian; Bedi, Karan
2016-01-01
ABSTRACT Dynamic regulation of gene expression via signal transduction pathways is of fundamental importance during many biological processes such as cell state transitioning, cell cycle progression and stress responses. In this study we used serum stimulation as a cell response paradigm to apply the nascent RNA Bru-seq technique in order to capture early dynamic changes in the nascent transcriptome. Our data provides an unprecedented view of the dynamics of genome-wide transcription during the first two hours of serum stimulation in human fibroblasts. While some genes showed sustained induction or repression, other genes showed transient or delayed responses. Surprisingly, the dynamic patterns of induction and suppression of response genes showed a high degree of similarity, suggesting that these opposite outcomes are triggered by a common set of signals. As expected, early response genes such as those encoding components of the AP-1 transcription factor and those involved in the circadian clock were immediately but transiently induced. Surprisingly, transcription of important DNA damage response genes and histone genes were rapidly repressed. We also show that RNA polymerase II accelerates as it transcribes large genes and this was independent of whether the gene was induced or not. These results provide a unique genome-wide depiction of dynamic patterns of transcription of serum response genes and demonstrate the utility of Bru-seq to comprehensively capture rapid and dynamic changes of the nascent transcriptome. PMID:27230646
Capturing the dynamic nascent transcriptome during acute cellular responses: The serum response.
Kirkconnell, Killeen S; Paulsen, Michelle T; Magnuson, Brian; Bedi, Karan; Ljungman, Mats
2016-01-01
Dynamic regulation of gene expression via signal transduction pathways is of fundamental importance during many biological processes such as cell state transitioning, cell cycle progression and stress responses. In this study we used serum stimulation as a cell response paradigm to apply the nascent RNA Bru-seq technique in order to capture early dynamic changes in the nascent transcriptome. Our data provides an unprecedented view of the dynamics of genome-wide transcription during the first two hours of serum stimulation in human fibroblasts. While some genes showed sustained induction or repression, other genes showed transient or delayed responses. Surprisingly, the dynamic patterns of induction and suppression of response genes showed a high degree of similarity, suggesting that these opposite outcomes are triggered by a common set of signals. As expected, early response genes such as those encoding components of the AP-1 transcription factor and those involved in the circadian clock were immediately but transiently induced. Surprisingly, transcription of important DNA damage response genes and histone genes were rapidly repressed. We also show that RNA polymerase II accelerates as it transcribes large genes and this was independent of whether the gene was induced or not. These results provide a unique genome-wide depiction of dynamic patterns of transcription of serum response genes and demonstrate the utility of Bru-seq to comprehensively capture rapid and dynamic changes of the nascent transcriptome. PMID:27230646
Identification of the dynamic characteristics of a viscoelastic, nonlinear adhesive joint
NASA Astrophysics Data System (ADS)
Naraghi, T.; Nobari, A. S.
2015-09-01
In this paper, the nonlinear mechanical characteristics of an adhesive (Sikaflex-252) are identified over frequency range, using eigenvalues of nonlinear system and inverse eigen-sensitivity method and experimental data. Sikaflex-252 is selected as an adhesive which is mainly used as a joining medium (joint) in structural applications. In order to simulate the viscoelastic behaviour of the adhesive, the frequency dependent Young's modulus and damping coefficient are assumed in identification process leading to the updating process being repeated for different ranges of frequencies to identify stiffness and damping properties of the adhesive. Using the optimum equivalent linear frequency response function (OELF) concept, in order to realize the nonlinear nature of the adhesive, modal tests are performed under two different random excitation levels which illustrate the stiffness softening characteristic of adhesive which can have serious implications regarding dynamic stability of structures. Furthermore, based on the identified characteristics, the paper examines the possibility of tuning of the Standard Linear Solid model (SLS), in representing the adhesive viscoelastic behaviour. Results of this attempt proved that the S.L.S. model with tuned parameters significantly improves the fidelity of finite element (FE) model to experimental results.
Dynamic Stall Characteristics of Drooped Leading Edge Airfoils
NASA Technical Reports Server (NTRS)
Sankar, Lakshmi N.; Sahin, Mehmet; Gopal, Naveen
2000-01-01
Helicopters in high-speed forward flight usually experience large regions of dynamic stall over the retreating side of the rotor disk. The rapid variations in the lift and pitching moments associated with the stall process can result in vibratory loads, and can cause fatigue and failure of pitch links. In some instances, the large time lag between the aerodynamic forces and the blade motion can trigger stall flutter. A number of techniques for the alleviation of dynamic stall have been proposed and studied by researchers. Passive and active control techniques have both been explored. Passive techniques include the use of high solidity rotors that reduce the lift coefficients of individual blades, leading edge slots and leading edge slats. Active control techniques include steady and unsteady blowing, and dynamically deformable leading edge (DDLE) airfoils. Considerable amount of experimental and numerical data has been collected on the effectiveness of these concepts. One concept that has not received as much attention is the drooped-leading edge airfoil idea. It has been observed in wind tunnel studies and flight tests that drooped leading edge airfoils can have a milder dynamic stall, with a significantly milder load hysteresis. Drooped leading edge airfoils may not, however, be suitable at other conditions, e.g. in hover, or in transonic flow. Work needs to be done on the analysis and design of drooped leading edge airfoils for efficient operation in a variety of flight regimes (hover, dynamic stall, and transonic flow). One concept that is worthy of investigation is the dynamically drooping airfoil, where the leading edge shape is changed roughly once-per-rev to mitigate the dynamic stall.
Wind tunnel tests of the dynamic characteristics of the fluidic rudder
NASA Technical Reports Server (NTRS)
Belsterling, C. A.
1976-01-01
The fourth phase is given of a continuing program to develop the means to stabilize and control aircraft without moving parts or a separate source of power. Previous phases have demonstrated the feasibility of (1) generating adequate control forces on a standard airfoil, (2) controlling those forces with a fluidic amplifier and (3) cascading non-vented fluidic amplifiers operating on ram air supply pressure. The foremost objectives of the fourth phase covered under Part I of this report were to demonstrate a complete force-control system in a wind tunnel environment and to measure its static and dynamic control characteristics. Secondary objectives, covered under Part II, were to evaluate alternate configurations for lift control. The results demonstrate an overall response time of 150 msec, confirming this technology as a viable means for implementing low-cost reliable flight control systems.
NASA Astrophysics Data System (ADS)
Hashemi-Kia, M.; Cutchins, M. A.; Tinker, M. L.
1988-02-01
The effects of theoretical changes in mass and stiffness matrices on the dynamic characteristics of a model wing are considered. The NASTRAN computer code is utilized to find theoretical mass and stiffness matrices with their corresponding natural frequencies and mode shapes. The dynamic response is then calculated by using theoretical mass and stiffness matrices and theoretical modal data. Experimentally measured mode shapes and natural frequencies are used to improve the stiffness and mass matrices. The resulting improved stiffness and mass matrices are further used to calculate again the dynamic response for the model. Analysis of the computational results and experimental data show that the improved theoretical model represents the experimental model better than the original theoretical model. Other means of improving the theoretical model are summarized.
Dynamic response of a tank containing two liquids
NASA Astrophysics Data System (ADS)
Tang, Yu; Chang, Yao
1992-02-01
A study on the dynamic response of upright circular cylindrical liquid-storage tanks containing two different liquids under a horizontal base motion with arbitrary temporal variation is presented. Both rigid and flexible tanks are studied. The response functions examined include the base shear, base moments, and hydrodynamic pressure on the tank wall and base. Unlike the cases of tanks containing one liquid in which the response is controlled by one parameter, the responses of tanks that contain two different liquids are controlled by three parameters. For rigid tanks, the response functions are evaluated for a wide range of values for each parameter; the results are presented in tabular and graphic forms. The responses of flexible tanks containing two liquids are evaluated by an approximate approach which is an extension of the method used for evaluation of response functions for flexible tanks that contain only one liquid.
Navier-Stokes Simulation of the Canard-Wing-Body Longitudinal Dynamic Stability Characteristics
NASA Technical Reports Server (NTRS)
Tu, Eugene L.; VanDalsem, William R. (Technical Monitor)
1996-01-01
Many modern aircraft are canard-configured for aircraft control and improved aerodynamic performance. Canards can often enhance aircraft cruise performance, maneuverability and agility. For close-coupled canard configurations, the aerodynamic interaction between the canard and wing significantly changes the flow characteristics of the wing. In unsteady flow, such changes in the flow structure and performance of wings can be quite pronounced. Accurate modeling of the unsteady aerodynamics is essential for potential CFD design and analysis of such configurations. A time-accurate numerical simulation is performed to study the unsteady aerodynamic interaction between a canard and wing with emphasis on the effects of the canard on the configuration's dynamic response characteristics. The thin-layer Reynolds-averaged Navier-Stokes Equations with various turbulence models are used in this study. Computations are made on a generic, analytically-defined, close-coupled canard-wing-body configuration which has been the subject of numerous previously published experimental studies during the 1970's to mid-80's. More recently, a series of steady-flow simulations has been performed and published by the author. In the current study, the configuration is given prescribed ramp and oscillatory motions in order to predict characteristics such as the damping-in-pitch and oscillatory longitudinal stability parameters. The current computations are made at high-subsonic and transonic Mach numbers, moderate angles-of- attack from -4 to 20 degrees, and at various pitch rates and reduced frequencies. Comparisons of pressures and integrated force quantities (e.g. lift, drag, pitching moment and selected dynamic parameters) are made with other published computational results and available experimental data. Results showing the unsteady effects of the canard on surface pressures, integrated forces, canard-wing vortex interaction and vortex breakdown will be presented.
Study on Dynamic Response Measurement of the Submarine Pipeline by Full-Term FBG Sensors
Zhou, Jinghai; Sun, Li; Li, Hongnan
2014-01-01
The field of structural health monitoring is concerned with accurately and reliably assessing the integrity of a given structure to reduce ownership costs, increase operational lifetime, and improve safety. In structural health monitoring systems, fiber Bragg grating (FBG) is a promising measurement technology for its superior ability of explosion proof, immunity to electromagnetic interference, and high accuracy. This paper is a study on the dynamic characteristics of fiber Bragg grating (FBG) sensors applied to a submarine pipeline, as well as an experimental investigation on a laboratory model of the pipeline. The dynamic response of a submarine pipeline under seismic excitation is a coupled vibration of liquid and solid interaction. FBG sensors and strain gauges are used to monitor the dynamic response of a submarine pipeline model under a variety of dynamic loading conditions and the maximum working frequency of an FBG strain sensor is calculated according to its dynamic strain responses. Based on the theoretical and experimental results, it can be concluded that FBG sensor is superior to strain gauge and satisfies the demand of dynamic strain measurement. PMID:24971391
Study on dynamic response measurement of the submarine pipeline by full-term FBG sensors.
Zhou, Jinghai; Sun, Li; Li, Hongnan
2014-01-01
The field of structural health monitoring is concerned with accurately and reliably assessing the integrity of a given structure to reduce ownership costs, increase operational lifetime, and improve safety. In structural health monitoring systems, fiber Bragg grating (FBG) is a promising measurement technology for its superior ability of explosion proof, immunity to electromagnetic interference, and high accuracy. This paper is a study on the dynamic characteristics of fiber Bragg grating (FBG) sensors applied to a submarine pipeline, as well as an experimental investigation on a laboratory model of the pipeline. The dynamic response of a submarine pipeline under seismic excitation is a coupled vibration of liquid and solid interaction. FBG sensors and strain gauges are used to monitor the dynamic response of a submarine pipeline model under a variety of dynamic loading conditions and the maximum working frequency of an FBG strain sensor is calculated according to its dynamic strain responses. Based on the theoretical and experimental results, it can be concluded that FBG sensor is superior to strain gauge and satisfies the demand of dynamic strain measurement. PMID:24971391
Dynamic Characteristics Analysis of Analogue Networks Design Process
NASA Astrophysics Data System (ADS)
Zemliak, Alexander M.
The process of designing analogue circuits is formulated as a controlled dynamic system. For analysis of such system's properties it is suggested to use the concept of Lyapunov's function for a dynamic system. Various forms of Lyapunov's function are suggested. Analyzing the behavior of Lyapunov's function and its first derivative allowed us to determine significant correlation between this function's properties and processor time used to design the circuit. Numerical results prove the possibility of forecasting the behavior of various designing strategies and processor time based on the properties of Lyapunov's function for the process of designing the circuit.
Mathematical modeling of the aerodynamic characteristics in flight dynamics
NASA Technical Reports Server (NTRS)
Tobak, M.; Chapman, G. T.; Schiff, L. B.
1984-01-01
Basic concepts involved in the mathematical modeling of the aerodynamic response of an aircraft to arbitrary maneuvers are reviewed. The original formulation of an aerodynamic response in terms of nonlinear functionals is shown to be compatible with a derivation based on the use of nonlinear functional expansions. Extensions of the analysis through its natural connection with ideas from bifurcation theory are indicated.
mfERG Response Dynamics of the Aging Retina
Gerth, Christina; Sutter, Erich E.; Werner, John S.
2008-01-01
Purpose To determine age-related changes in retinal response dynamics derived from multifocal electroretinograms (mfERGs). Methods MfERG data were obtained from 70 subjects with normal phakic eyes, age 9 to 80 years. Whereas the first- and higher-order kernels resulting from the mfERG contain detailed information regarding the nonlinear response dynamics of the retina, they do not lend themselves directly to an easy and intuitive interpretation. To achieve a better appreciation of fast adaptive mechanisms and their changes with aging, regional averages of the kernel series were translated at different retinal eccentricities (0°−5°, 5°−15°, and 15°−25°) into responses generated in different contexts. Specifically, the effect of aging on responses to stimuli presented in isolation was compared with the effect on responses adapted by preceding stimuli (“forward” effect). The interference of the immediately following stimuli with the response generation (“backward effect”) was also considered. Results Age-related changes were found in the isolated flash response as well as in the backward and forward interactions between consecutive flash responses. Larger fractional changes with age were found in response density than in implicit time, and the rate of change with age was larger for responses to isolated flashes than for responses adapted by preceding flashes. Conclusions Senescent changes in the isolated flash response and in consecutive flash interactions derived from the binary kernel series indicate an aging process at an early stage in the visual system. Mechanisms of retinal adaptation may partially compensate for age-related reductions in the isolated flash response. PMID:14507891
Auditory virtual environment with dynamic room characteristics for music performances
NASA Astrophysics Data System (ADS)
Choi, Daniel Dhaham
A room-adaptive system was designed to simulate an electro-acoustic space that changes room characteristics in real-time according to the content of sound. In this specific case, the focus of the sound components is on the different styles and genres of music. This system is composed of real-time music recognition algorithms that analyze the different elements of music, determine the desired room characteristics, and output the acoustical parameters via multi-channel room simulation mechanisms. The system modifies the acoustic properties of a space and enables it to "improvise" its acoustical parameters based on the sounds of the music performances.
The dynamic adsorption characteristics of phenol by granular activated carbon.
Namane, A; Hellal, A
2006-09-01
The objective of the present work is to determine the operating conditions of an activated carbon filter, based on the characteristics of breakthrough curves. For this we apply the technical developed by Mickaels for the ionic exchange and applied by Luchkis for the adsorption, and which is the mass transfer zone. To reach our goal, an evaluation of the operating conditions (height of the bed, flow and concentration of effluent) on the characteristics of the mass transfer zone was made and an explanation of the mechanism of adsorption was given. Thereafter a modeling of the experimental results was done. PMID:16621251
NASA Technical Reports Server (NTRS)
Dvorak, S. D.; Hosny, W. M.; Steenken, W. G.; Taylor, J. H.
1987-01-01
A compressor test was conducted in which transient data were obtained for the purpose of identifying the high-speed post-stability characteristics. The transient, surge-cycle nature of high-speed post-stability operation precludes the possibility of obtaining the characteristics in a steady-state manner, as is possible during low-speed poststability operation, which is characterized by quasi-steady rotating-stall behavior. Specialized compressor instrumentation was developed and was used to obtain the necessary surge-cycle performance data, which were then digitized, filtered, and analyzed. The high-speed post-stability characteristics were obtained through the use of a maximum likelihood-parameter estimation technique. The estimated characteristics were found to be insensitive to the presence of measurement noise and unmodelled system dynamics, but the compressor time-response constants, which were also estimated, were more sensitive to these same disturbances.
Phase response curves elucidating the dynamics of coupled oscillators.
Granada, A; Hennig, R M; Ronacher, B; Kramer, A; Herzel, H
2009-01-01
Phase response curves (PRCs) are widely used in circadian clocks, neuroscience, and heart physiology. They quantify the response of an oscillator to pulse-like perturbations. Phase response curves provide valuable information on the properties of oscillators and their synchronization. This chapter discusses biological self-sustained oscillators (circadian clock, physiological rhythms, etc.) in the context of nonlinear dynamics theory. Coupled oscillators can synchronize with different frequency ratios, can generate toroidal dynamics (superposition of independent frequencies), and may lead to deterministic chaos. These nonlinear phenomena can be analyzed with the aid of a phase transition curve, which is intimately related to the phase response curve. For illustration purposes, this chapter discusses a model of circadian oscillations based on a delayed negative feedback. In a second part, the chapter provides a step-by-step recipe to measure phase response curves. It discusses specifications of this recipe for circadian rhythms, heart rhythms, neuronal spikes, central pattern generators, and insect communication. Finally, it stresses the predictive power of measured phase response curves. PRCs can be used to quantify the coupling strength of oscillations, to classify oscillator types, and to predict the complex dynamics of periodically driven oscillations. PMID:19216921
Dynamic Response Study of Flexible Nozzle in Solid Rocket Motor
NASA Astrophysics Data System (ADS)
Shi, Hongbin; Hou, Xiao
2002-01-01
system, solid rocket motor and control system must be examined jointly many times during the course of the flexible nozzle study. With the aim of acquiring the responses of flexible to different excitation, there is much experiment to be done. Those different excitation signals are accomplished when different forces applied to the supports in divergent section. While the deformation of the nozzle, especially the deformation of supports ,which attach control system to divergent section, relates directly to control problems. During the course of thrust vector control, the forces are applied in the shape of stronger impact force. In the condition of excitation force applied, the better we know about deformation of the divergent section, especially the local deformation of the supports in the divergent section, the more control is accurate. In fact, all control is accomplished in dynamic state. The information of swing angle not only includes displacement in the condition of control force applied but also includes velocity and acceleration where control force applied. Only all that deformation and deformation process are comprehend comprehensively, can control efficiency and control accuracy be improved. in which the flexible joint is simply treated as distributed spring. With finite element method, the dynamic responses of the flexible nozzle model is studied in condition of dynamic load applied in finite element method. The dynamic response Results are presented in this paper when triangular wave excitation, sine wave Excitation and arc sine wave excitation applied. displacement of sine wave and arc sine wave lag 0.025s than maximal load. Velocity response has also the property lagging than load, which is little than displacement hysteresis effect. Maximal velocity lag 0.005s than maximal load. in the condition of above three sorts load applied, acceleration response shows obvious property of oscillating. These results can play important in flexible nozzle structure
NASA Technical Reports Server (NTRS)
Lau, K.- M.; Kim, K.-M.; Yang, S.
1998-01-01
In this paper, we present a description of the internal dynamics and boundary forcing characteristics of two major components of the Asian summer monsoon (ASM), i.e., the South Asian (SAM) and the Southeast-East Asian monsoon (SEAM). The description is based on a new monsoon-climate paradigm in which the variability of ASM is considered as the outcome of the interplay of a "fast" and an "intermediate" monsoon subsystem, under the influenced of the "slow" varying external forcings. Two sets of regional monsoon indices derived from dynamically consistent rainfall and wind data are used in this study. For SAM, the internal dynamics is represented by that of a "classical" monsoon system where the anomalous circulation is governed by Rossby-wave dynamics, i.e., generation of anomalous vorticity induced by an off-equatorial heat source is balanced by planetary vorticity advection. On the other hand, the internal dynamics of SEAM is characterized by a "hybrid" monsoon system featuring multi-cellular meridional circulation over the East Asian section, extending from the deep tropics to midlatitudes. These meridional-cells link tropical heating to extratropical circulation system via the East Asian jetstream, and are responsible for the characteristic occurrences of zonally oriented anomalous rainfall patterns over East Asian and the subtropical western Pacific. In the extratropical regions, the major upper level vorticity balance is by anomalous vorticity advection and generation by the anomalous divergent circulation. A consequence of this is that compared to SAM, the SEAM is associated with stronger teleconnection patterns to regions outside the ASM. A strong SAM is linked to basin-scale sea surface temperature (SST) fluctuation with significant signal in the equatorial eastern Pacific. During the boreal spring SST warming in the Arabian Sea and the subtropical western Pacific may lead to a strong SAM. For SEAM, interannual variability is tied to SSTA over the Sea of
Dynamic response of the thermal data capture unit.
Bhutani, Nipun
2005-08-01
The dynamic response of a thermal data capture unit is calculated for a given missile flight test environment. Power spectral densities calculated from the analytical model were compared with the experimental results. Maximum peak displacements were used to calculate clearances required during the installation phase of system assembly.
Glassy Dynamics in the Adaptive Immune Response Prevents Autoimmune Disease
NASA Astrophysics Data System (ADS)
Sun, Jun; Earl, David J.; Deem, Michael W.
2005-09-01
The immune system normally protects the human host against death by infection. However, when an immune response is mistakenly directed at self-antigens, autoimmune disease can occur. We describe a model of protein evolution to simulate the dynamics of the adaptive immune response to antigens. Computer simulations of the dynamics of antibody evolution show that different evolutionary mechanisms, namely, gene segment swapping and point mutation, lead to different evolved antibody binding affinities. Although a combination of gene segment swapping and point mutation can yield a greater affinity to a specific antigen than point mutation alone, the antibodies so evolved are highly cross reactive and would cause autoimmune disease, and this is not the chosen dynamics of the immune system. We suggest that in the immune system’s search for antibodies, a balance has evolved between binding affinity and specificity.
Modeling and simulation of consumer response to dynamic pricing.
Valenzuela, J.; Thimmapuram, P.; Kim, J
2012-08-01
Assessing the impacts of dynamic-pricing under the smart grid concept is becoming extremely important for deciding its full deployment. In this paper, we develop a model that represents the response of consumers to dynamic pricing. In the model, consumers use forecasted day-ahead prices to shift daily energy consumption from hours when the price is expected to be high to hours when the price is expected to be low while maintaining the total energy consumption as unchanged. We integrate the consumer response model into the Electricity Market Complex Adaptive System (EMCAS). EMCAS is an agent-based model that simulates restructured electricity markets. We explore the impacts of dynamic-pricing on price spikes, peak demand, consumer energy bills, power supplier profits, and congestion costs. A simulation of an 11-node test network that includes eight generation companies and five aggregated consumers is performed for a period of 1 month. In addition, we simulate the Korean power system.
Dynamic responses of a two-dimensional flapping foil motion
NASA Astrophysics Data System (ADS)
Lu, Xi-Yun; Liao, Qin
2006-09-01
The investigation of a flapping foil, which is used as a basic mode of the flapping-based locomotion in insects, birds, and fish, is performed by solving the Navier-Stokes equations numerically. In this Brief Communication we provide insight into the understanding of dynamics of a flapping foil. A critical flapping Reynolds number based on the flapping frequency and amplitude, above which a forward flapping movement occurs, is predicted. The dynamics of the flapping foil are analyzed in two dynamic responses, i.e., an oscillatory movement and a steady movement, which depend on the density ratio between the foil and the surrounded fluid. The steady movement response is related to the forward flapping motion. The Strouhal number that governs a vortex shedding for the forward flapping foil is calculated and lies in the range where flying and swimming animals will be likely to tune for high propulsive efficiency.
The dynamic response of Coriolis mass flow meters
NASA Astrophysics Data System (ADS)
Cheesewright, R.; Clark, C.; Belhadj, A.; Hou, Y. Y.
2003-09-01
The speed of response of commercial Coriolis meters to a step change in mass flow rate corresponds to a time constant which may range from 0.1s to several seconds. This response is a result both of the dynamic response of the physical components of the meter and of the electronics and the computational algorithms used to convert that dynamic response into an estimate of the mass flow rate. A comprehensive investigation of the dynamic response is presented with a view to establishing the ultimate limits of the overall meter response. Attention is initially concentrated on a simple straight tube meter and analytical solutions are presented for the response to a step change in flow rate both for an undamped meter and for a meter with internal damping. These results are compared with results from a finite element model of the same meter and then the finite element modelling is extended to geometries typical of commercial meters. Finally, representative results are presented from an experimental study of the response of commercial meters to step changes in flow rate. A study of the essential components of the algorithm used in a meter leads to the conclusion that the time constant cannot be less than the period of one cycle of the meter drive. The analytical, finite element and experimental results all combine to show that the meters all respond in the period of one drive cycle but that the flow step induces fluctuations in the meter output which decay under the influence of the flow tube damping. It is the additional damping introduced in the signal processing to overcome these fluctuations which is responsible for the large observed time constants. Possible alternative approaches are discussed.
Dynamic characteristics of mixtures of plutonium, Nevada tuff, and water
Myers, W.; Rojas, S.; Kimpland, R.H.; Jaegers, P.J.; Sanchez, R.G.; Hayes, D.; Paternoster, R.; Anderson, R.; Stratton, W.
1996-02-01
One of the technical options being considered for long term disposition of weapons grade plutonium is geologic storage at Yucca Mountain. Multikilogram quantities of plutonium are to be vitrified, placed within a heavy steel container, and buried in the material know as Nevada tuff. It has been postulated that after ten thousand years, geologic and chemical processes would have disintegrated the steel container and created the possibility for plutonium to form mixtures with Nevada tuff and water that could lead to a nuclear explosion in the range of kilotons. A survey and description of critical homogeneous mixtures of plutonium, silicon dioxide, Nevada tuff, and water which also identified the mixture regimes where autocatalytic dynamic behavior is possible was completed. This study is a follow up of this survey and the major objective is to examine the dynamic behavior of the worst case critical and supercritical configurations of plutonium, water and Nevada tuff.
Nike Black Brant V high altitude dynamic instability characteristics
NASA Technical Reports Server (NTRS)
Montag, W. H.; Walker, L. L., Jr.
1979-01-01
Flight experience on the Nike Black Brant V has demonstrated the existence of plume induced flow separation over the fins and aft body of the Black Brant V motor. Modelling of the forces associated with this phenomenon as well as analysis of the resultant vehicle coning motion and its effect on the velocity vector heading are presented. A summary of Nike Black Brant V flight experience with high altitude dynamic instability is included.
Dynamic Monitoring Reveals Motor Task Characteristics in Prehistoric Technical Gestures
Pfleging, Johannes; Stücheli, Marius; Iovita, Radu; Buchli, Jonas
2015-01-01
Reconstructing ancient technical gestures associated with simple tool actions is crucial for understanding the co-evolution of the human forelimb and its associated control-related cognitive functions on the one hand, and of the human technological arsenal on the other hand. Although the topic of gesture is an old one in Paleolithic archaeology and in anthropology in general, very few studies have taken advantage of the new technologies from the science of kinematics in order to improve replicative experimental protocols. Recent work in paleoanthropology has shown the potential of monitored replicative experiments to reconstruct tool-use-related motions through the study of fossil bones, but so far comparatively little has been done to examine the dynamics of the tool itself. In this paper, we demonstrate that we can statistically differentiate gestures used in a simple scraping task through dynamic monitoring. Dynamics combines kinematics (position, orientation, and speed) with contact mechanical parameters (force and torque). Taken together, these parameters are important because they play a role in the formation of a visible archaeological signature, use-wear. We present our new affordable, yet precise methodology for measuring the dynamics of a simple hide-scraping task, carried out using a pull-to (PT) and a push-away (PA) gesture. A strain gage force sensor combined with a visual tag tracking system records force, torque, as well as position and orientation of hafted flint stone tools. The set-up allows switching between two tool configurations, one with distal and the other one with perpendicular hafting of the scrapers, to allow for ethnographically plausible reconstructions. The data show statistically significant differences between the two gestures: scraping away from the body (PA) generates higher shearing forces, but requires greater hand torque. Moreover, most benchmarks associated with the PA gesture are more highly variable than in the PT gesture
Dynamic Monitoring Reveals Motor Task Characteristics in Prehistoric Technical Gestures.
Pfleging, Johannes; Stücheli, Marius; Iovita, Radu; Buchli, Jonas
2015-01-01
Reconstructing ancient technical gestures associated with simple tool actions is crucial for understanding the co-evolution of the human forelimb and its associated control-related cognitive functions on the one hand, and of the human technological arsenal on the other hand. Although the topic of gesture is an old one in Paleolithic archaeology and in anthropology in general, very few studies have taken advantage of the new technologies from the science of kinematics in order to improve replicative experimental protocols. Recent work in paleoanthropology has shown the potential of monitored replicative experiments to reconstruct tool-use-related motions through the study of fossil bones, but so far comparatively little has been done to examine the dynamics of the tool itself. In this paper, we demonstrate that we can statistically differentiate gestures used in a simple scraping task through dynamic monitoring. Dynamics combines kinematics (position, orientation, and speed) with contact mechanical parameters (force and torque). Taken together, these parameters are important because they play a role in the formation of a visible archaeological signature, use-wear. We present our new affordable, yet precise methodology for measuring the dynamics of a simple hide-scraping task, carried out using a pull-to (PT) and a push-away (PA) gesture. A strain gage force sensor combined with a visual tag tracking system records force, torque, as well as position and orientation of hafted flint stone tools. The set-up allows switching between two tool configurations, one with distal and the other one with perpendicular hafting of the scrapers, to allow for ethnographically plausible reconstructions. The data show statistically significant differences between the two gestures: scraping away from the body (PA) generates higher shearing forces, but requires greater hand torque. Moreover, most benchmarks associated with the PA gesture are more highly variable than in the PT gesture
Loudness Change in Response to Dynamic Acoustic Intensity
ERIC Educational Resources Information Center
Olsen, Kirk N.; Stevens, Catherine J.; Tardieu, Julien
2010-01-01
Three experiments investigate psychological, methodological, and domain-specific characteristics of loudness change in response to sounds that continuously increase in intensity (up-ramps), relative to sounds that decrease (down-ramps). Timbre (vowel, violin), layer (monotone, chord), and duration (1.8 s, 3.6 s) were manipulated in Experiment 1.…
The response dynamics of recognition memory: Sensitivity and bias.
Koop, Gregory J; Criss, Amy H
2016-05-01
Advances in theories of memory are hampered by insufficient metrics for measuring memory. The goal of this paper is to further the development of model-independent, sensitive empirical measures of the recognition decision process. We evaluate whether metrics from continuous mouse tracking, or response dynamics, uniquely identify response bias and mnemonic evidence, and demonstrate 1 application of these metrics to the strength-based mirror-effect paradigm. In 4 studies, we show that response dynamics can augment our current analytic repertoire in a way that speaks to the psychological mechanisms underlying recognition memory. We manipulated familiarity and response bias via encoding strength and the proportion of targets at test (Experiment 1) and found that the initial degree of deviation of the mouse movement toward a response is a robust indicator of response bias. In order to better isolate measures of memory strength, we next minimized response bias through the use of 2-alternative forced-choice tests (Experiments 2 and 3). Changes in the direction of movement along the x-axis provided an indication of encoding strength. We conclude by applying these metrics to the typical strength-based mirror effect design (Experiment 4) in an attempt to further discriminate between differentiation and criterion-shift accounts. (PsycINFO Database Record PMID:26595069
Ultrasound Evaluation of Dynamic Responses of Female Pelvic Floor Muscles
Peng, Qiyu; Jones, Ruth; Shishido, Keiichi; Constantinou, Christos E.
2007-01-01
Ultrasound imaging of the pelvic floor carrys diagnostically important information about the dynamic response of the Pelvic Floor Muscles (PFM) to potentially incontinence-producing stress, which can not be readily captured and assimilated by the observer during the scanning process. We presented an approach based on motion tracking to quantatively analyze the dynamic parameters of PFM on the Ano-Rectal Angle (ARA). Perineal ultrasonography was performed on 22 asymptomatic females and 9 Stress Urinary Incontinent (SUI) patients with a broad age distribution and parity. The ventral-dorsal and cephalad-caudad movements of the ARA were resolved and kinematic parameters, in terms of displacement, trajectory, velocity and acceleration were analyzed. The results revealed the possible mechanisms of PFM responses to prevent the urine from incontinence in fast and stress events. The statistical analyses showed the PFM responses of the healthy subjects and the SUI patients are significantly different in both the supine and standing experiments. PMID:17210220
Studies of TLP dynamic response under wind, waves and current
NASA Astrophysics Data System (ADS)
Gu, Jia-yang; Yang, Jian-min; Lv, Hai-ning
2012-09-01
Investigated is the coupled response of a tension leg platform (TLP) for random waves. Inferred are the mass matrix, coupling stiffness matrix, damping matrix in the vibration differential equation and external load of TLP in moving coordinating system. Infinitesimal method is applied to divide columns and pontoons into small parts. Time domain motion equation is solved by Runge-Kutta integration scheme. Jonswap spectrum is simulated in the random wave, current is simulated by linear interpolation, and NPD spectrum is applied as wind spectrum. The Monte Carlo method is used to simulate random waves and fluctuated wind. Coupling dynamic response, change of tendon tension and riser tension in different sea conditions are analyzed by power spectral density (PSD). The influence of approach angle on dynamic response of TLP and tendon tension is compared.
Dynamic Response Research of U Shaped Pipe with Viscoelastic Damping Layer
NASA Astrophysics Data System (ADS)
Guo, Yajuan; Meng, Guang; Li, Hongguang
The frequency dependency property of viscoelastic material leads to the dynamic analysis of compound structures which are complex and costly. Furthermore, using commercial finite element software, it is difficult to carry out the dynamic response analysis with this characteristic. Based on finite element iterative and modal strain energy (MSE) method, a mode superposition algorithm was proposed to solve the dynamic response of viscoelastic damping structure in this paper. Through iterative and MSE method, the modal frequency and loss factor for each mode can be obtained. Before calculating the next order modal frequency, the modal mode and corresponding load are extracted and the response of node was calculated at first in this algorithm. As a consequence, the node displacement response can be solved by summarizing the response results of each independent mode in the required frequency range. Numerical calculation of U shaped pipe with viscoelastic damping layer illustrates that the method is simple and practical. Moreover, the simulations with this method agree quite well with the experimental derived results. In the meantime, the damping layer parameters study shows that the position of the damping layer has an obvious effect of reducing the vibration response of U shaped pipe, but the width of the damping layer has little influence. The procedure proposed in this paper can be extended to analyze other more complex structures with viscoelastic material.
Dynamic characteristics of a space-station solar wing array
Dorsey, J.T.; Bush, H.G.
1984-06-01
Describes a solar-wing-array concept which meets space-station requirements for minimum fundamental frequency, component modularity, and growth potential. The basic wing-array design parameters are varied, and the resulting effects on the array vibration frequencies and mode shapes are assessed. The transient response of a free-free space station (incorporating a solar-wing-array point design) to a load applied at the space-station center is studied. The use of the transient response studies in identifying critically loaded structural members is briefly discussed.
Climate Creators. Dynamic Characteristics of People Who Create Positive Organizational Climate.
ERIC Educational Resources Information Center
Bedley, Gene
This book contains practical information on creating a positive work climate within an organization. Twenty separate characteristics of successful "climate creators" are discussed. Information is also included on: (1) climate; (2) climate creators; (3) dynamic characteristics of climate creators; (4) the challenge of creating a positive climate;…
Dynamic Resource Allocation in Disaster Response: Tradeoffs in Wildfire Suppression
Petrovic, Nada; Alderson, David L.; Carlson, Jean M.
2012-01-01
Challenges associated with the allocation of limited resources to mitigate the impact of natural disasters inspire fundamentally new theoretical questions for dynamic decision making in coupled human and natural systems. Wildfires are one of several types of disaster phenomena, including oil spills and disease epidemics, where (1) the disaster evolves on the same timescale as the response effort, and (2) delays in response can lead to increased disaster severity and thus greater demand for resources. We introduce a minimal stochastic process to represent wildfire progression that nonetheless accurately captures the heavy tailed statistical distribution of fire sizes observed in nature. We then couple this model for fire spread to a series of response models that isolate fundamental tradeoffs both in the strength and timing of response and also in division of limited resources across multiple competing suppression efforts. Using this framework, we compute optimal strategies for decision making scenarios that arise in fire response policy. PMID:22514605
Dynamic response tests of inertial and optical wind-tunnel model attitude measurement devices
NASA Technical Reports Server (NTRS)
Buehrle, R. D.; Young, C. P., Jr.; Burner, A. W.; Tripp, J. S.; Tcheng, P.; Finley, T. D.; Popernack, T. G., Jr.
1995-01-01
Results are presented for an experimental study of the response of inertial and optical wind-tunnel model attitude measurement systems in a wind-off simulated dynamic environment. This study is part of an ongoing activity at the NASA Langley Research Center to develop high accuracy, advanced model attitude measurement systems that can be used in a dynamic wind-tunnel environment. This activity was prompted by the inertial model attitude sensor response observed during high levels of model vibration which results in a model attitude measurement bias error. Significant bias errors in model attitude measurement were found for the measurement using the inertial device during wind-off dynamic testing of a model system. The amount of bias present during wind-tunnel tests will depend on the amplitudes of the model dynamic response and the modal characteristics of the model system. Correction models are presented that predict the vibration-induced bias errors to a high degree of accuracy for the vibration modes characterized in the simulated dynamic environment. The optical system results were uncorrupted by model vibration in the laboratory setup.
Prediction and measurement of human pilot dynamic characteristics
NASA Technical Reports Server (NTRS)
Hess, Ronald A.; Reedy, James T.
1988-01-01
An analytical and experimental study of human pilot control strategies in a manned rotorcraft simulation is described. The task simulated involves a low-speed, constant-altitude maneuvering task in which a head-down display is utilized to allow the pilot to track a moving hover point. The efficacy of the display law driving an 'acceleration symbol' is determined and the manner in which the prediction and measurement of pilot/vehicle dynamics can be made part of man/machine system evaluations is demonstrated.
Dynamic materials response at multiscales: Experiments and simulations
NASA Astrophysics Data System (ADS)
Luo, Sheng-Nian
One of the grand challenges in materials physics is dynamic responses to impulsive loading, including shock waves, radiation, and pulsed fields, due to their highly transient nature and extremely complex microstructure effects. Dynamic responses, such as plasticity, damage, cavitation, phase changes, and chemical reactions, are inherently multiscale and heavily dependent on microstructure. One has to resort to a suite of tools, including experiments, modeling and simulations, and theory. However, the gaps in spatial or temporal scales between experiments and simulations are still wide, while cross-scale theories are still in early development. To this end, we exploit large-scale molecular dynamics simulations, electron microscopy, and ultrafast synchrotron X-ray imaging and scattering, to probe materials response at length scales ranging from lattice to micron, and time scales, from picosecond to second. For examples, simultaneous, high-speed, X-ray imaging (mesoscale strain-field mapping) and diffraction measurements along with macroscopic measurements have been achieved. Based on classical nucleation theory and large-scale molecular dynamics simulations, we demonstrate the equivalence between length and time scales for nucleation events, which provides a framework to bridge different scales. Certainly, advancing multiscale science requires sustained, concerted, experimental, modeling and theoretical efforts. We have benefited from the colleagues at the Advanced Photon Source, and the Peac Institute of Multiscales Sciences.
The dynamic response of a viscoelastic biological tissue simulant
NASA Astrophysics Data System (ADS)
Shepherd, Christopher; Appleby-Thomas, Gareth; Hazell, Paul; Allsop, Derek
2009-06-01
The development and optimisation of new projectiles requires comparative techniques to assess ballistic performance. Porcine gelatin has found a substantial niche in the ballistics community as a tissue mimic. Primarily due to its elasticity, gelatin has been shown to deform in a similar manner to biological tissues. Bullet impacts typically occur in the 350-850 m/s range and consequently, knowledge of the high strain rate dynamic properties of both the projectile constituents and target materials is desirable if simulations are to allow the optimisation of projectile design. A large body of knowledge exists on the dynamic properties of projectiles, however relatively little data exists in the literature on the dynamic response of flesh simulants. The Hugoniot for a 20 wt% porcine gelatin, which exhibits a ballistic response similar to that of human tissues at room temperature, is determined in this paper using the plate impact technique. Up-Us and Up-P relationships are determined for impact velocities in the range of 200-900 m/s. Good agreement with the limited available data from the literature for similar concentrations is found and the dynamic response established at impact stresses up to 3 times higher than that observed elsewhere. Additionally, high frequency elastic properties are investigated using ultrasound and compared to those observed elsewhere.
Chemistry in interstellar space. [environment characteristics influencing reaction dynamics
NASA Technical Reports Server (NTRS)
Donn, B.
1973-01-01
The particular characteristics of chemistry in interstellar space are determined by the unique environmental conditions involved. Interstellar matter is present at extremely low densities. Large deviations from thermodynamic equilibrium are, therefore, to be expected. A relatively intense ultraviolet radiation is present in many regions. The temperatures are in the range from 5 to 200 K. Data concerning the inhibiting effect of small activation energies in interstellar clouds are presented in a table. A summary of measured activation energies or barrier heights for exothermic exchange reactions is also provided. Problems of molecule formation are discussed, taking into account gas phase reactions and surface catalyzed processes.
Dynamic response of underpasses for high-speed train lines
NASA Astrophysics Data System (ADS)
Vega, J.; Fraile, A.; Alarcon, E.; Hermanns, L.
2012-11-01
Underpasses are common in modern railway lines. Wildlife corridors and drainage conduits often fall into this category of partially buried structures. Their dynamic behavior has received far less attention than that of other structures such as bridges, but their large number makes their study an interesting challenge from the viewpoint of safety and cost savings. Here, we present a complete study of a culvert, including on-site measurements and numerical modeling. The studied structure belongs to the high-speed railway line linking Segovia and Valladolid in Spain. The line was opened to traffic in 2004. On-site measurements were performed for the structure by recording the dynamic response at selected points of the structure during the passage of high-speed trains at speeds ranging between 200 and 300 km/h. The measurements provide not only reference values suitable for model fitting, but also a good insight into the main features of the dynamic behavior of this structure. Finite element techniques were used to model the dynamic behavior of the structure and its key features. Special attention is paid to vertical accelerations, the values of which should be limited to avoid track instability according to Eurocode. This study furthers our understanding of the dynamic response of railway underpasses to train loads.
Analogy between the stimulus-response characteristics of neuronal and electrochemical cells
NASA Astrophysics Data System (ADS)
Okamoto, Hiroshi; Tanaka, Naoki; Naito, Masayoshi
1995-05-01
One of the simplest catalytically rhythmic reactions, an electrochemical oxidation of formic acid, is found to show a stimulus-response behavior analogous to that of a nerve. The response of a nerve cell has three important characteristics: a threshold, a refractory period and a response that depends on the slope of ramp stimulation. Formic acid oxidation has these characteristics and also shows a digital response to analogue stimulus. Such behavior is discussed in terms of a chemical reaction mechanisms.
Dynamic tuning of lattice plasmon lasers with long coherence characteristics
NASA Astrophysics Data System (ADS)
Hoang, Thang; Yang, Ankun; Schatz, George; Odom, Teri; Mikkelsen, Maiken
Here, we experimentally demonstrate dynamic tuning of an optically-pumped lattice plasmon laser based on arrays of gold nanoparticles and liquid gain materials [A. Yang, T.B. Hoang et al., Nature Communications 6, 6939 (2015)]. The structure consists of an array of 120 nm diameter gold disks with a height of 50 nm and 600 nm spacing. A liquid gain material composed of IR-140 dye molecules dissolved in a variety of organic solvents is placed on top of the disks and held in place by a thin glass coverslip. At a lasing wavelength of 860 nm, time-resolved measurements show a dramatic reduction of the decay time from 1 ns to less than 20 ps when the optical excitation power density increases from below to above the lasing threshold, indicating the transition from spontaneous to stimulated emission. By changing the dielectric environment surrounding the gold disks in real time, the lasing wavelength can be dynamically tuned over a 55 nm range. Finally, we will discuss recent experiments where we probe both the temporal and spatial coherence properties of the lattice plasmon laser. This advance of tunable plasmon lasers offer prospects to enhance and detect weak physical and chemical processes on the nanoscale in real time.
Dynamic characteristics of a magnetorheological pin joint for civil structures
NASA Astrophysics Data System (ADS)
Li, Yancheng; Li, Jianchun
2014-03-01
Magnetorheological (MR) pin joint is a novel device in which its joint moment resistance can be controlled in real-time by altering the applied magnetic field. The smart pin joint is intended to be used as a controllable connector between the columns and beams of a civil structure to instantaneously shift the structural natural frequencies in order to avoid resonance and therefore to reduce unwanted vibrations and hence prevent structural damage. As an intrinsically nonlinear device, modelling of this MR fluid based device is a challenging task and makes the design of a suitable control algorithm a cumbersome situation. Aimed at its application in civil structure, the main purpose of this paper is to test and characterise the hysteretic behaviour of MR pin joint. A test scheme is designed to obtain the dynamic performance of MR pin joint in the dominant earthquake frequency range. Some unique phenomena different from those of MR damper are observed through the experimental testing. A computationally-efficient model is proposed by introducing a hyperbolic element to accurately reproduce its dynamic behaviour and to further facilitate the design of a suitable control algorithm. Comprehensive investigations on the model accuracy and dependences of the proposed model on loading condition (frequency and amplitude) and input current level are reported in the last section of this paper.
NASA Astrophysics Data System (ADS)
Galea, Pauline; D'Amico, Sebastiano; Farrugia, Daniela
2014-11-01
Anchor Bay and surrounding regions are located on the northwest coast of the island of Malta, Central Mediterranean. The area is characterized by a coastal cliff environment having an outcropping layer of hard coralline limestone (UCL) resting on a thick (up to 50 m) layer of clays and marls (Blue Clay, BC). This configuration gives rise to coastal instability effects, in particular lateral spreading phenomena and rock falls. Previous and ongoing studies have identified both lateral spreading rates and vertical motions of several millimetres per year. The area is an interesting natural laboratory as coastal detachment processes in a number of different stages can be identified and are easily accessible. We investigate the site dynamic characteristics of this study area by recording ambient noise time-series at more than 30 points, over an area of 0.07 km2, using a portable three-component seismograph. The time-series are processed to give both horizontal-to-vertical spectral ratio graphs (H/V) as well as frequency-dependent polarisation analysis. The H/V graphs illustrate and quantify aspects of site resonance effects due both to underlying geology as well as to mechanical resonance of partly or wholly detached blocks. The polarization diagrams indicate the degree of linearity and predominant directions of vibrational effects. H/V curves closer to the cliff edge show complex responses at higher frequencies, characteristic of the dynamic behaviour of individual detached blocks. Particle motion associated with the higher frequencies shows strongly directional polarization and a high degree of linearity at well-defined frequencies, indicative of normal-mode vibration. The stable plateau areas, on the other hand, show simple, single-peak H/V curves representative of the underlying stratification and no predominant polarization direction. These results, which will be compared with those from other experiments in the area, have important implications for the
Salimi, S; Park, S Simon; Freiheit, T
2011-09-01
The vibration characteristics of shell structures such as eyes have been shown to vary with intraocular pressure (IOP). Therefore, vibration characteristics of the eye have the potential to provide improved correlation to IOP over traditional IOP measurements. As background to examine an improved IOP correlation, this paper develops a finite element model of an eye subject to vibration. The eye is modeled as a shell structure filled with inviscid pressurized fluid in which there is no mean flow. This model solves a problem of a fluid with coupled structural interactions of a generally spherically shaped shell system. The model is verified by comparing its vibrational characteristics with an experimental modal analysis of an elastic spherical shell filled with water. The structural dynamic effects due to change in pressure of the fluid are examined. It is shown that the frequency response of this fluid-solid coupled system has a clear increase in natural frequency as the fluid pressure rises. The fluid and structure interaction is important for accurate prediction of system dynamics. This model is then extended to improve its accuracy in modeling the eye by including the effect of the lens to study corneal vibration. The effect of biomechanical parameters such as the thicknesses of different parts of the eye and eye dimensions in altering measured natural frequencies is investigated and compared to the influence of biomechanical parameters in Goldmann applanation tonometry models. The dynamic response of the eye is found to be less sensitive to biomechanical parameters than the applanation tonometry model. PMID:22010744
Fluctuation-response relation unifies dynamical behaviors in neural fields
NASA Astrophysics Data System (ADS)
Fung, C. C. Alan; Wong, K. Y. Michael; Mao, Hongzi; Wu, Si
2015-08-01
Anticipation is a strategy used by neural fields to compensate for transmission and processing delays during the tracking of dynamical information and can be achieved by slow, localized, inhibitory feedback mechanisms such as short-term synaptic depression, spike-frequency adaptation, or inhibitory feedback from other layers. Based on the translational symmetry of the mobile network states, we derive generic fluctuation-response relations, providing unified predictions that link their tracking behaviors in the presence of external stimuli to the intrinsic dynamics of the neural fields in their absence.
Static and dynamic responses of an ultrathin adaptive secondary mirror
NASA Astrophysics Data System (ADS)
del Vecchio, Ciro; Brusa, Guido; Gallieni, Daniele; Lloyd-Hart, Michael; Davison, Warren B.
1999-09-01
We present the results of a compete set of static and dynamic runs of the FEA model of the MMT adaptive secondary. The thin mirror is the most delicate component of the MMT adaptive secondary unit, as it provides the deformable optical surface able to correct the incoming wavefront. The static performances are evaluated as a function of the various load cases arising form gravitational loads and from the forces deriving from the magnetic interactions between actuators. In addition, computations were performed to assess the dynamic response to the high bandwidth, adaptive correcting force.s In both cases, the performances of the adaptive mirror design are able to accommodate the severe specifications.
Fluctuation-response relation unifies dynamical behaviors in neural fields.
Fung, C C Alan; Wong, K Y Michael; Mao, Hongzi; Wu, Si
2015-08-01
Anticipation is a strategy used by neural fields to compensate for transmission and processing delays during the tracking of dynamical information and can be achieved by slow, localized, inhibitory feedback mechanisms such as short-term synaptic depression, spike-frequency adaptation, or inhibitory feedback from other layers. Based on the translational symmetry of the mobile network states, we derive generic fluctuation-response relations, providing unified predictions that link their tracking behaviors in the presence of external stimuli to the intrinsic dynamics of the neural fields in their absence. PMID:26382448
Note on dynamic response of large space structures
NASA Astrophysics Data System (ADS)
Elishakoff, I.; Abramovich, H.
1992-07-01
The dynamic behavior of large space structures, modeled as a Bresse-Timoshenko beam, was analyzed using the Bresse-Timoshenko beam model, but with the 4th-order derivative of the beam deflection with respect to time not included in the dynamical equations. In particular, the forced vibration response of symmetric large space structures was calculated for various parameters of the system. It is shown that a direct modal analysis yielding an exact solution is applicable due to the absence of the 4th-order time derivative in the Bresse-Timoshenko beam equations.
Dynamic characteristics of vibration isolation platforms considering the joints of the struts
NASA Astrophysics Data System (ADS)
Zhang, Jingrui; Guo, Zixi; Zhang, Yao
2016-09-01
This paper discusses the dynamic characteristics of the impacts and corresponding frictions generated by the clearances of joints of vibration isolation platforms for control moment gyroscopes (CMGs) on spacecraft. A contact force model is applied using a nonlinear contact force model, and the frictions in the joints are considered in the dynamic analysis. First, the dynamic characteristics of a single isolation strut with spherical joints were studied, and joints with different initial clearance sizes were separately analyzed. Then, dynamic models of the vibration isolation platform for a CMG cluster with both perfect joints and joints with clearances were established. During the numeral simulation, joints with different elastic moduli were used to study the nonlinear characteristics. Finally, the distributions of the collision points, which can serve as a reference for the reliability and lifetime of a platform, were given.
Population dynamics and mutualism: Functional responses of benefits and costs
Holland, J. Nathaniel; DeAngelis, Donald L.; Bronstein, Judith L.
2002-01-01
We develop an approach for studying population dynamics resulting from mutualism by employing functional responses based on density‐dependent benefits and costs. These functional responses express how the population growth rate of a mutualist is modified by the density of its partner. We present several possible dependencies of gross benefits and costs, and hence net effects, to a mutualist as functions of the density of its partner. Net effects to mutualists are likely a monotonically saturating or unimodal function of the density of their partner. We show that fundamental differences in the growth, limitation, and dynamics of a population can occur when net effects to that population change linearly, unimodally, or in a saturating fashion. We use the mutualism between senita cactus and its pollinating seed‐eating moth as an example to show the influence of different benefit and cost functional responses on population dynamics and stability of mutualisms. We investigated two mechanisms that may alter this mutualism's functional responses: distribution of eggs among flowers and fruit abortion. Differences in how benefits and costs vary with density can alter the stability of this mutualism. In particular, fruit abortion may allow for a stable equilibrium where none could otherwise exist.
Effect of drive mechanisms on dynamic characteristics of spacecraft tracking-drive flexible systems
NASA Astrophysics Data System (ADS)
Zhu, Shi-yao; Lei, Yong-jun; Wu, Xin-feng; Zhang, Da-peng
2015-05-01
Spacecraft tracking-drive flexible systems (STFS) consist of drive mechanisms and flexible structures, including solar array and a variety of large-scale antennas. The electromechanical interaction inside drive mechanisms makes it quite complicated to directly analyze the dynamic characteristics of an STFS. In this paper, an indirect dynamic characteristic analysis method for operating-state STFS is presented. The proposed method utilizes the structure dynamics approximation of drive mechanisms that converts the electromechanical model of an STFS into a structure dynamic model with elastic boundary conditions. The structure dynamics approximation and the dynamic characteristic analysis method are validated by experimental and analytical results, respectively. The analysis results indicate that the gear transmission ratio and viscous friction coefficient are the primary factors in approximating boundary stiffness and damping. Dynamic characteristics of an STFS with a large gear transmission ratio are close to that of a flexible structure with a cantilever boundary. Otherwise, torsion-mode natural frequencies of the STFS become smaller and corresponding modal damping ratios become larger, as a result of the local stiffness and damping features of drive mechanisms.
Dynamic characteristics of peripheral jet ACV. I - Heaving motion
NASA Astrophysics Data System (ADS)
Mori, T.; Maeda, H.
The theory of the dynamics of peripheral jet ACV is presented. The flow patterns under the bottom of the ACV are classified into two types, i.e. underfed and overfed regimes. The mathematical models associated with such regimes are presented and the equations of those models are derived. The forced heaving oscillation of a two-dimensional ACV model is investigated experimentally and variations of cushion pressure and lift force are measured and compared with the results obtained by the numerical calculation. The coincidence of these two results seems to be reasonable. The heaving motion of ACV which is induced by the simple harmonic oscillation of the ground board is also analyzed numerically.
Subsonic and Transonic Dynamic Stability Characteristics of the X-33
NASA Technical Reports Server (NTRS)
Tomek, D.; Boyden, R.
2000-01-01
Dynamic stability testing was conducted on a 2.5% scale model of the X-33 technology demonstrator sub-orbital flight-test vehicle. This testing was conducted at the NASA Langley Research Center (LaRC) l6-Foot Transonic Wind Tunnel with the LaRC High-speed Dynamic Stability system. Forced oscillation data were acquired for various configurations over a Mach number range of 0.3 to 1.15 measuring pitch, roll and yaw damping, as well as the normal force due to pitch rate and the cross derivatives. The test angle of attack range was from -2 to 24 degrees, except for those cases where load constraints limited the higher angles of attack at the higher Mach numbers. A variety of model configurations with and without control surfaces were employed, including a body alone configuration. Stable pitch damping is exhibited for the baseline configuration throughout the angle of attack range for Mach numbers 0.3, 0.8, and 1.15. Stable pitch damping is present for Mach numbers 0.9 and 0.6 with the exception of angles 2 and 16 degrees, respectively. Constant and stable roll damping were present for the baseline configuration over the range of Mach numbers up to an angle of attack of 16 degrees. The yaw damping for the baseline is somewhat stable and constant for the angle of attack range from -2 to 8 degrees, with the exception of Mach numbers 0.6 and 0.8. Yaw damping becomes highly unstable for all Mach numbers at angles of attack greater than 8 degrees.
Analysis of the dynamic response of pump-turbine impellers. Influence of the rotor
NASA Astrophysics Data System (ADS)
Egusquiza, Eduard; Valero, Carme; Presas, Alex; Huang, Xingxing; Guardo, Alfredo; Seidel, Ulrich
2016-02-01
This paper deals with the dynamic response of pump-turbine impellers. A pump-turbine impeller is a complex structure attached to a rotor and rotating inside a casing full of water with very small clearances between the rotating and the stationary parts. The dynamic response of this type of structures is very complex and it is very much affected by the connection to the rotor as well as by the added mass and boundary conditions. As a consequence its calculation presents several uncertainties. First, the dynamic response of pump-turbine impellers is introduced. Second an experimental investigation in a real impeller attached to the rotor and inside the machine was carried out. For this investigation, the impeller of an existing pump-turbine unit with an installed power of 110 MW and a diameter of 2.87 m was studied. For a better analysis of the experimental results a numerical model using FEM was also built-up. Frequencies and mode-shapes were identified numerically and experimentally and the characteristics of the structural response analyzed. To determine the influence of the rotor and supporting structures on the impeller response the results were compared with the ones obtained with the same impeller but suspended (non-connected to the rotor). Experimental and numerical simulation were also used for this case. The changes in the dynamic response due to the rotor connection were determined. Finally the results obtained are compared with the results from other pump-turbine impellers of different designs and general conclusions about the dynamics of this type of structures are given.
Fluid Compressibility Effects on the Dynamic Response of Hydrostatic Journal Bearings
NASA Technical Reports Server (NTRS)
Sanandres, Luis A.
1991-01-01
A theoretical analysis for the dynamic performance characteristics of laminar flow, capillar/orifice compensated hydrostatic journal bearings is presented. The analysis considers in detail the effect of fluid compressibility in the bearing recesses. At high frequency excitations beyond a break frequency, the bearing hydrostatic stiffness increases sharply and it is accompanied by a rapid decrease in direct damping. Also, the potential of pneumatic hammer instability (negative damping) at low frequencies is likely to occur in hydrostatic bearing applications handling highly compressible fluids. Useful design criteria to avoid undesirable dynamic operating conditions at low and high frequencies are determined. The effect of fluid recess compressibility is brought into perspective, and found to be of utmost importance on the entire frequency spectrum response and stability characteristics of hydrostatic/hybrid journal bearings.
Bartnikowski, Michal; Klein, Travis J; Melchels, Ferry P W; Woodruff, Maria A
2014-07-01
Tissue engineering focuses on the repair and regeneration of tissues through the use of biodegradable scaffold systems that structurally support regions of injury while recruiting and/or stimulating cell populations to rebuild the target tissue. Within bone tissue engineering, the effects of scaffold architecture on cellular response have not been conclusively characterized in a controlled-density environment. We present a theoretical and practical assessment of the effects of polycaprolactone (PCL) scaffold architectural modifications on mechanical and flow characteristics as well as MC3T3-E1 preosteoblast cellular response in an in vitro static plate and custom-designed perfusion bioreactor model. Four scaffold architectures were contrasted, which varied in inter-layer lay-down angle and offset between layers, while maintaining a structural porosity of 60 ± 5%. We established that as layer angle was decreased (90° vs. 60°) and offset was introduced (0 vs. 0.5 between layers), structural stiffness, yield stress, strength, pore size, and permeability decreased, while computational fluid dynamics-modeled wall shear stress was increased. Most significant effects were noted with layer offset. Seeding efficiencies in static culture were also dramatically increased due to offset (∼ 45% to ∼ 86%), with static culture exhibiting a much higher seeding efficiency than perfusion culture. Scaffold architecture had minimal effect on cell response in static culture. However, architecture influenced osteogenic differentiation in perfusion culture, likely by modifying the microfluidic environment. PMID:24473931
NASA Astrophysics Data System (ADS)
Trofimov, Vyacheslav A.; Varentsova, Svetlana A.
2009-05-01
A method, suggested by us earlier for identification of materials with close spectra in terahertz range of frequencies and based on the analysis of medium response spectral lines dynamics, is verified experimentally. The temporal dynamics of spectral lines allows to determine relaxation time of rotational transitions as well. A question about measurement time, that is sufficient for determining of material response characteristic time, is discussed. To demonstrate the efficiency of proposed method, we treat the response of soap and chocolate under the action of terahertz pulse with a few cycles. Our investigation shows that it is possible to identify these materials with high probability.
Hydrologic characteristics and suspended sediment dynamics in the Gradašica river basin
NASA Astrophysics Data System (ADS)
Kogoj, Mojca; Rusjan, Simon; Vidmar, Andrej; Mikoš, Matjaž
2013-04-01
Sediment transport in catchments is an important aspect of environmental research because of its role in the transport of sediment-associated nutrients, pesticides and other contaminants. High turbidity levels in water bodies affect stream morphology, aquatic organisms and their habitats, cause siltation of water reservoirs and have other side effects. For maintaining adequate water quality, reducing excessive soil erosion and proper estimation of the amount of transported material it is necessary to define and understand main factors that control sediment production and transport in rivers. Understanding the hydrological response of catchments on hydrometeorological phenomena and their influences on changes in suspended sediment concentrations require measurements of the processes at time scales that correspond to hydrological dynamics of a catchment. Our research aims to investigate hydrological and seasonal controls over suspended sediment production and obtain an insight into a suspended sediment concentration dynamics and total loads in a forested catchment. For this purpose, we study several factors actively controlling suspended sediment mobilization and transport in a small experimental catchment in Polhov Gradec mountainous area in the central part of Slovenia, drained by the Gradaščica river. Steep slopes, relatively high altitudes and abundance of precipitation (average yearly sums between 1600 to 1700 mm) result in a quick rise in the water level and consequently, in torrential response of the Gradaščica river. The studied headwaters lay on dolomite and limestone with a mainly natural land cover. The area is a subject to erosion with debris sources in the dolomite and additional catchment characteristics that contribute to high sediment transport rates. The main categories of factors that actively control sediment mobilization and transport from catchments, studied in our research, are hydrological and meteorological controls, physiographic factors
Characteristics of near response cells projecting to the oculomotor nucleus.
Zhang, Y; Mays, L E; Gamlin, P D
1992-04-01
1. Previous work has shown neurons just dorsal and lateral to the oculomotor nucleus that increase their firing rate with increases in the angle of ocular convergence. It has been suggested that the output of these midbrain near response cells might provide the vergence command needed by the medial rectus motoneurons. However, lens accommodation ordinarily accompanies convergence, and a subsequent study showed that only about one-half of these midbrain near response cells carried a signal related exclusively to vergence. One hypothesis suggested by this finding is that this subgroup of neurons might have a unique role in providing a "pure" vergence signal to the medial rectus motoneurons. 2. In the present study extracellular recordings were made from midbrain near response cells in monkeys while eye position and lens accommodation were measured. The monkeys viewed targets through an optical system that allowed the accommodative and ocular vergence demands to be manipulated independently. This approach was used to produce a partial dissociation of accommodative and vergence responses, so that an accommodative and vergence coefficient could be determined for each cell, by the use of the following equation FR = R0 + kda x AR + kdv x CR where FR is the firing rate of the near response cell, R0 is the predicted firing rate for a distant target, kda is the (dissociated) accommodation coefficient, AR is the accommodative response, kdv is the (dissociated) vergence coefficient, and CR is the convergence response. 3. The vergence and accommodation coefficients were determined for a large number of midbrain near response cells, including a subset that could be antidromically activated from the medial rectus subdivisions of the oculomotor nucleus. Some near response neurons were found with signals related exclusively to convergence (i.e., kdv greater than 0 and kda = 0), whereas several others had signals related exclusively to lens accommodation (i.e., kda greater than 0