Polyatomic gases with dynamic pressure: Maximum entropy principle and shock structure
Pavić-Čolić, Milana; Simić, Srboljub
2016-01-01
This paper is concerned with the analysis of polyatomic gases within the framework of kinetic theory. Internal degrees of freedom are modeled using a single continuous variable corresponding to the molecular internal energy. Non-equilibrium velocity distribution function, compatible with macroscopic field variables, is constructed using the maximum entropy principle. A proper collision cross section is constructed which obeys the micro-reversibility requirement. The source term and entropy production rate are determined in the form which generalizes the results obtained within the framework of extended thermodynamics. They can be adapted to appropriate physical situations due to the presence of parameters. They are also compared with the results obtained using BGK approximation. For the proposed model the shock structure problem is thoroughly analyzed.
2011-01-10
...: Establishing Maximum Allowable Operating Pressure or Maximum Operating Pressure Using Record Evidence, and... facilities of their responsibilities, under Federal integrity management (IM) regulations, to perform... system, especially when calculating Maximum Allowable Operating Pressure (MAOP) or Maximum Operating...
The inverse maximum dynamic flow problem
BAGHERIAN; Mehri
2010-01-01
We consider the inverse maximum dynamic flow (IMDF) problem.IMDF problem can be described as: how to change the capacity vector of a dynamic network as little as possible so that a given feasible dynamic flow becomes a maximum dynamic flow.After discussing some characteristics of this problem,it is converted to a constrained minimum dynamic cut problem.Then an efficient algorithm which uses two maximum dynamic flow algorithms is proposed to solve the problem.
Maximum Matchings via Glauber Dynamics
Jindal, Anant; Pal, Manjish
2011-01-01
In this paper we study the classic problem of computing a maximum cardinality matching in general graphs $G = (V, E)$. The best known algorithm for this problem till date runs in $O(m \\sqrt{n})$ time due to Micali and Vazirani \\cite{MV80}. Even for general bipartite graphs this is the best known running time (the algorithm of Karp and Hopcroft \\cite{HK73} also achieves this bound). For regular bipartite graphs one can achieve an $O(m)$ time algorithm which, following a series of papers, has been recently improved to $O(n \\log n)$ by Goel, Kapralov and Khanna (STOC 2010) \\cite{GKK10}. In this paper we present a randomized algorithm based on the Markov Chain Monte Carlo paradigm which runs in $O(m \\log^2 n)$ time, thereby obtaining a significant improvement over \\cite{MV80}. We use a Markov chain similar to the \\emph{hard-core model} for Glauber Dynamics with \\emph{fugacity} parameter $\\lambda$, which is used to sample independent sets in a graph from the Gibbs Distribution \\cite{V99}, to design a faster algori...
49 CFR 195.406 - Maximum operating pressure.
2010-10-01
... 49 Transportation 3 2010-10-01 2010-10-01 false Maximum operating pressure. 195.406 Section 195... HAZARDOUS LIQUIDS BY PIPELINE Operation and Maintenance § 195.406 Maximum operating pressure. (a) Except for surge pressures and other variations from normal operations, no operator may operate a pipeline at a...
Dynamical maximum entropy approach to flocking
Cavagna, Andrea; Giardina, Irene; Ginelli, Francesco; Mora, Thierry; Piovani, Duccio; Tavarone, Raffaele; Walczak, Aleksandra M.
2014-04-01
We derive a new method to infer from data the out-of-equilibrium alignment dynamics of collectively moving animal groups, by considering the maximum entropy model distribution consistent with temporal and spatial correlations of flight direction. When bird neighborhoods evolve rapidly, this dynamical inference correctly learns the parameters of the model, while a static one relying only on the spatial correlations fails. When neighbors change slowly and the detailed balance is satisfied, we recover the static procedure. We demonstrate the validity of the method on simulated data. The approach is applicable to other systems of active matter.
Kuracina Richard
2015-06-01
Full Text Available The article deals with the measurement of maximum explosion pressure and the maximum rate of exposure pressure rise of wood dust cloud. The measurements were carried out according to STN EN 14034-1+A1:2011 Determination of explosion characteristics of dust clouds. Part 1: Determination of the maximum explosion pressure pmax of dust clouds and the maximum rate of explosion pressure rise according to STN EN 14034-2+A1:2012 Determination of explosion characteristics of dust clouds - Part 2: Determination of the maximum rate of explosion pressure rise (dp/dtmax of dust clouds. The wood dust cloud in the chamber is achieved mechanically. The testing of explosions of wood dust clouds showed that the maximum value of the pressure was reached at the concentrations of 450 g / m3 and its value is 7.95 bar. The fastest increase of pressure was observed at the concentrations of 450 g / m3 and its value was 68 bar / s.
2010-10-01
... distribution systems. (a) No person may operate a low-pressure distribution system at a pressure high enough to...) No person may operate a low pressure distribution system at a pressure lower than the minimum... 49 Transportation 3 2010-10-01 2010-10-01 false Maximum and minimum allowable operating...
49 CFR 192.621 - Maximum allowable operating pressure: High-pressure distribution systems.
2010-10-01
... STANDARDS Operations § 192.621 Maximum allowable operating pressure: High-pressure distribution systems. (a) No person may operate a segment of a high pressure distribution system at a pressure that exceeds the... segment of a distribution system otherwise designed to operate at over 60 p.s.i. (414 kPa) gage,...
Study of maximum pressure for composite hepta-tubular powders
M. C. Gupta
1959-10-01
Full Text Available In this paper the expressions for maximum pressure occurring positions in the case of composite hepta-tubular powers used in conventional guns and the corresponding conditions have been derived under certain conditions, viz., the value of n, the ratio of specific heats, has been assumed to be the same for both the charges and the covolume corrections have not been neglected.
Maximum bubble pressure rheology of low molecular mass organogels.
Fei, Pengzhan; Wood, Steven J; Chen, Yan; Cavicchi, Kevin A
2015-01-13
Maximum bubble pressure rheology is used to characterize organogels of 0.25 wt % 12-hydroxystearic acid (12-HSA) in mineral oil, 3 wt % (1,3:2,4) dibenzylidene sorbitol (DBS) in poly(ethylene glycol), and 1 wt % 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS) in poly(ethylene glycol). The maximum pressure required to inflate a bubble at the end of capillary inserted in a gel is measured. This pressure is related to the gel modulus in the case of elastic cavitation and the gel modulus and toughness in the case of irreversible fracture. The 12-HSA/mineral oil gels are used to demonstrate that this is a facile technique useful for studying time-dependent gel formation and aging and the thermal transition from a gel to a solution. Comparison is made to both qualitative gel tilting measurements and quantitative oscillatory shear rheology to highlight the utility of this measurement and its complementary nature to oscillatory shear rheology. The DBS and DMDBS demonstrate the generality of this measurement to measure gel transition temperatures.
Radiation Pressure Acceleration: the factors limiting maximum attainable ion energy
Bulanov, S S; Schroeder, C B; Bulanov, S V; Esirkepov, T Zh; Kando, M; Pegoraro, F; Leemans, W P
2016-01-01
Radiation pressure acceleration (RPA) is a highly efficient mechanism of laser-driven ion acceleration, with with near complete transfer of the laser energy to the ions in the relativistic regime. However, there is a fundamental limit on the maximum attainable ion energy, which is determined by the group velocity of the laser. The tightly focused laser pulses have group velocities smaller than the vacuum light speed, and, since they offer the high intensity needed for the RPA regime, it is plausible that group velocity effects would manifest themselves in the experiments involving tightly focused pulses and thin foils. However, in this case, finite spot size effects are important, and another limiting factor, the transverse expansion of the target, may dominate over the group velocity effect. As the laser pulse diffracts after passing the focus, the target expands accordingly due to the transverse intensity profile of the laser. Due to this expansion, the areal density of the target decreases, making it trans...
46 CFR 52.01-55 - Increase in maximum allowable working pressure.
2010-10-01
... 46 Shipping 2 2010-10-01 2010-10-01 false Increase in maximum allowable working pressure. 52.01-55... POWER BOILERS General Requirements § 52.01-55 Increase in maximum allowable working pressure. (a) When the maximum allowable working pressure of a boiler has been established, an increase in the pressure...
Payoff-monotonic game dynamics and the maximum clique problem.
Pelillo, Marcello; Torsello, Andrea
2006-05-01
Evolutionary game-theoretic models and, in particular, the so-called replicator equations have recently proven to be remarkably effective at approximately solving the maximum clique and related problems. The approach is centered around a classic result from graph theory that formulates the maximum clique problem as a standard (continuous) quadratic program and exploits the dynamical properties of these models, which, under a certain symmetry assumption, possess a Lyapunov function. In this letter, we generalize previous work along these lines in several respects. We introduce a wide family of game-dynamic equations known as payoff-monotonic dynamics, of which replicator dynamics are a special instance, and show that they enjoy precisely the same dynamical properties as standard replicator equations. These properties make any member of this family a potential heuristic for solving standard quadratic programs and, in particular, the maximum clique problem. Extensive simulations, performed on random as well as DIMACS benchmark graphs, show that this class contains dynamics that are considerably faster than and at least as accurate as replicator equations. One problem associated with these models, however, relates to their inability to escape from poor local solutions. To overcome this drawback, we focus on a particular subclass of payoff-monotonic dynamics used to model the evolution of behavior via imitation processes and study the stability of their equilibria when a regularization parameter is allowed to take on negative values. A detailed analysis of these properties suggests a whole class of annealed imitation heuristics for the maximum clique problem, which are based on the idea of varying the parameter during the imitation optimization process in a principled way, so as to avoid unwanted inefficient solutions. Experiments show that the proposed annealing procedure does help to avoid poor local optima by initially driving the dynamics toward promising regions in
Maximum Pressure Evaluation during Expulsion of Entrapped Air from Pressurized Pipelines
Diana Maria Bucur
2017-01-01
Full Text Available Pressurized pipeline systems may have a wide operating regime. This paper presents the experimental analysis of the transient flow in a horizontal pipe containing an air pocket, which allows the ventilation of the air after the pressurization of the hydraulic system, through an orifice placed at the downstream end. The measurements are made on a laboratory set-up, for different supply pressures and various geometries of water column length, air pocket and expulsion orifice diameter. Dimensional analysis is carried out in order to determine a relation between the parameters influencing the maximum pressure value. A two equations model is obtained and a criterion is established for their use. The equations are validated with experimental data from the present laboratory set-up and with other data available in the literature. The results presented as non-dimensional quantities variations show a good agreement with the previous experimental and analytical researches.
The role of pressure anisotropy on the maximum mass of cold compact stars
Karmakar, S.; Mukherjee, S.; Sharma, R.; Maharaj, S.D.
2007-01-01
We study the physical features of a class of exact solutions for cold compact anisotropic stars. The effect of pressure anisotropy on the maximum mass and surface redshift is analysed in the Vaidya-Tikekar model. It is shown that maximum compactness, redshift and mass increase in the presence of anisotropic pressures; numerical values are generated which are in agreement with observation.
Generalized degeneracy, dynamic monopolies and maximum degenerate subgraphs
Zaker, Manouchehr
2012-01-01
A graph $G$ is said to be a $k$-degenerate graph if any subgraph of $G$ contains a vertex of degree at most $k$. Let $\\kappa$ be any non-negative function on the vertex set of $G$. We first define a $\\kappa$-degenerate graph. Next we give an efficient algorithm to determine whether a graph is $\\kappa$-degenerate. We revisit the concept of dynamic monopolies in graphs. The latter notion is used in formulation and analysis of spread of influence such as disease or opinion in social networks. We consider dynamic monopolies with (not necessarily positive) but integral threshold assignments. We obtain a sufficient and necessary relationship between dynamic monopolies and generalized degeneracy. As applications of the previous results we consider the problem of determining the maximum size of $\\kappa$-degenerate (or $k$-degenerate) induced subgraphs in any graph. We obtain some upper and lower bounds for the maximum size of any $\\kappa$-degenerate induced subgraph in general and regular graphs. All of our bounds ar...
Maximum Allowable Dynamic Load of Mobile Manipulators with Stability Consideration
Heidary H. R.
2015-09-01
Full Text Available High payload to mass ratio is one of the advantages of mobile robot manipulators. In this paper, a general formula for finding the maximum allowable dynamic load (MADL of wheeled mobile robot is presented. Mobile manipulators operating in field environments will be required to manipulate large loads, and to perform such tasks on uneven terrain, which may cause the system to reach dangerous tip-over instability. Therefore, the method is expanded for finding the MADL of mobile manipulators with stability consideration. Moment-Height Stability (MHS criterion is used as an index for the system stability. Full dynamic model of wheeled mobile base and mounted manipulator is considered with respect to the dynamic of non-holonomic constraint. Then, a method for determination of the maximum allowable loads is described, subject to actuator constraints and by imposing the stability limitation as a new constraint. The actuator torque constraint is applied by using a speed-torque characteristics curve of a typical DC motor. In order to verify the effectiveness of the presented algorithm, several simulation studies considering a two-link planar manipulator, mounted on a mobile base are presented and the results are discussed.
On the Law of Equal Pressure Maximum%等压最大值定律
王子佳
2011-01-01
This paper states the law of equal pressure maximum, including： the law of gas temperature T＇s equal pressure maximum; the law of gas volume X＇s equal pressure maximum; the law of gas cubage V＇s equal pressure maximum; the law of unit gas volume X＇s equal pressure maximum.%阐述了等压最大值定律，包括：（1）瓦斯温度T等压最大值定律，（2）瓦斯量N等压最大值定律，（3）瓦斯容积V等压最大值定律，（4）单位容积瓦斯量x等压最大值定律4种．
Dynamic pressures in porous media
Balcerak, Ernie
2012-12-01
Understanding the relationship between fluid pressures and water content (saturation) in soils or other porous media can be important in a wide range of practical areas, including oil recovery, infiltration and flooding during extreme weather events, and environmental remediation. The relationship between fluid pressures and saturation in porous media has been reported to be dynamic—to depend on the flow rate as saturation changes. However, previous studies designed to understand the dynamic component of this relationship have been highly contradictory. To learn more, Hou et al. conducted experiments to quantify the relationship between pressure and rate of saturation change using a small-volume system with highly characterized fluid selective microsensors. Their analyses corrected for two often-overlooked experimental artifacts: gas pressure gradients and sensor response rate. When the researchers applied these corrections, they found that the dependence of pressure on the rate of saturation change may be much less significant than previously thought. (Water Resources Research, doi:10.1029/2012WR012434, 2012)
49 CFR 192.619 - Maximum allowable operating pressure: Steel or plastic pipelines.
2010-10-01
... operate a segment of steel or plastic pipeline at a pressure that exceeds a maximum allowable operating... design pressure of the weakest element in the segment, determined in accordance with subparts C and D of... K of this part, if any variable necessary to determine the design pressure under the design...
Approximating the maximum weight clique using replicator dynamics.
Bomze, I R; Pelillo, M; Stix, V
2000-01-01
Given an undirected graph with weights on the vertices, the maximum weight clique problem (MWCP) is to find a subset of mutually adjacent vertices (i.e., a clique) having the largest total weight. This is a generalization of the classical problem of finding the maximum cardinality clique of an unweighted graph, which arises as a special case of the MWCP when all the weights associated to the vertices are equal. The problem is known to be NP-hard for arbitrary graphs and, according to recent theoretical results, so is the problem of approximating it within a constant factor. Although there has recently been much interest around neural-network algorithms for the unweighted maximum clique problem, no effort has been directed so far toward its weighted counterpart. In this paper, we present a parallel, distributed heuristic for approximating the MWCP based on dynamics principles developed and studied in various branches of mathematical biology. The proposed framework centers around a recently introduced continuous characterization of the MWCP which generalizes an earlier remarkable result by Motzkin and Straus. This allows us to formulate the MWCP (a purely combinatorial problem) in terms of a continuous quadratic programming problem. One drawback associated with this formulation, however, is the presence of "spurious" solutions, and we present characterizations of these solutions. To avoid them we introduce a new regularized continuous formulation of the MWCP inspired by previous works on the unweighted problem, and show how this approach completely solves the problem. The continuous formulation of the MWCP naturally maps onto a parallel, distributed computational network whose dynamical behavior is governed by the so-called replicator equations. These are dynamical systems introduced in evolutionary game theory and population genetics to model evolutionary processes on a macroscopic scale.We present theoretical results which guarantee that the solutions provided by
Maximum, minimum, and optimal mutation rates in dynamic environments
Ancliff, Mark; Park, Jeong-Man
2009-12-01
We analyze the dynamics of the parallel mutation-selection quasispecies model with a changing environment. For an environment with the sharp-peak fitness function in which the most fit sequence changes by k spin flips every period T , we find analytical expressions for the minimum and maximum mutation rates for which a quasispecies can survive, valid in the limit of large sequence size. We find an asymptotic solution in which the quasispecies population changes periodically according to the periodic environmental change. In this state we compute the mutation rate that gives the optimal mean fitness over a period. We find that the optimal mutation rate per genome, k/T , is independent of genome size, a relationship which is observed across broad groups of real organisms.
The role of pressure anisotropy on the maximum mass of cold compact stars
Karmakar, S.; Mukherjee, S.; Sharma, R.; Maharaj, S. D.
2007-06-01
We study the physical features of a class of exact solutions for cold compact anisotropic stars. The effect of pressure anisotropy on the maximum mass and surface red-shift is analysed in the Vaidya--Tikekar model. It is shown that maximum compactness, red-shift and mass increase in the presence of anisotropic pressures; numerical values are generated which are in agreement with observation.
The role of pressure anisotropy on the maximum mass of cold compact stars
S Karmakar; S Mukherjee; S Sharma; S D Maharaj
2007-06-01
We study the physical features of a class of exact solutions for cold compact anisotropic stars. The effect of pressure anisotropy on the maximum mass and surface red-shift is analysed in the Vaidya–Tikekar model. It is shown that maximum compactness, red-shift and mass increase in the presence of anisotropic pressures; numerical values are generated which are in agreement with observation.
R. van Mastrigt (Ron)
1990-01-01
textabstractThe contractility of the urinary bladder can be adequately described in terms of the parameters P0 (isometric pressure) and Vmax (maximum contraction velocity). In about 12% of urodynamic evaluations of patients these clinically relevant parameters can be calculated from pressure and flo
IN VITRO COMPARISON OF MAXIMUM PRESSURE DEVELOPED BY IRRIGATION SYSTEMS IN A KIDNEY MODEL.
Proietti, Silvia; Dragos, Laurian; Somani, Bhaskar K; Butticè, Salvatore; Talso, Michele; Emiliani, Esteban; Baghdadi, Mohammed; Giusti, Guido; Traxer, Olivier
2017-04-05
To evaluate in vitro the maximum pressure generated in an artificial kidney model when people of different levels of strengths used various irrigation systems. Fifteen people were enrolled and divided in 3 groups based on their strengths. Individual strength was evaluated according to the maximum pressure each participant was able to achieve using an Encore™ Inflator. The irrigation systems evaluated were: T-FlowTM Dual Port, HilineTM, continuous flow single action pumping system (SAPSTM) with the system close and open, Irri-flo IITM, a simple 60-ml syringe and PeditrolTM . Each irrigation system was connected to URF-V2 ureteroscope, which was inserted into an artificial kidney model. Each participant was asked to produce the maximum pressure possible with every irrigation device. Pressure was measured with the working channel (WC) empty, with a laser fiber and a basket inside. The highest pressure was achieved with the 60 ml-syringe system and the lowest with SAPS continuous version system (with continuous irrigation open), compared to the other irrigation devices (p< 0.0001). Irrespective of the irrigation system, there was a significant difference in the pressure between the WC empty and when occupied with the laser fiber or the basket inside it (p<0.0001). The stratification between the groups showed that the most powerful group could produce the highest pressure in the kidney model with all the irrigation devices in almost any situation. The exception to this was the T-Flow system, which was the only device where no statistical differences were detected among these groups. The use of irrigation systems can often generate excessive pressure in an artificial kidney model, especially with an unoccupied WC of the ureteroscope. Depending on the strength of force applied, very high pressure can be generated by most irrigation devices irrespective of whether the scope is occupied or not.
Approximate maximum-entropy moment closures for gas dynamics
McDonald, James G.
2016-11-01
Accurate prediction of flows that exist between the traditional continuum regime and the free-molecular regime have proven difficult to obtain. Current methods are either inaccurate in this regime or prohibitively expensive for practical problems. Moment closures have long held the promise of providing new, affordable, accurate methods in this regime. The maximum-entropy hierarchy of closures seems to offer particularly attractive physical and mathematical properties. Unfortunately, several difficulties render the practical implementation of maximum-entropy closures very difficult. This work examines the use of simple approximations to these maximum-entropy closures and shows that physical accuracy that is vastly improved over continuum methods can be obtained without a significant increase in computational cost. Initially the technique is demonstrated for a simple one-dimensional gas. It is then extended to the full three-dimensional setting. The resulting moment equations are used for the numerical solution of shock-wave profiles with promising results.
40 CFR 147.1803 - Existing Class I and III wells authorized by rule-maximum injection pressure.
2010-07-01
... authorized by rule-maximum injection pressure. 147.1803 Section 147.1803 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER PROGRAMS (CONTINUED) STATE, TRIBAL, AND EPA-ADMINISTERED...—maximum injection pressure. The owner or operator shall limit injection pressure to the lesser of: (a) A...
Theoretical research on aggregative dynamic pressure damper
HU Jun-hua; CAO Shu-ping; LUO Xiao-hui; NIU Zi-hua; XIN Ji-song
2009-01-01
To broaden the frequency width and increase the damping coefficient of a dynamic pressure damper, we designed an aggregative dynamic pressure damper (ADPD). Combined with the advantages of traditional dynamic pressure dampers (TDPD), ADPD can not only increase the damping coefficient in wide frequency range for valve control system, but also absorb partial pressure pulsations and impacts in the low and high frequency fields. Based on the theoretical research and the analysis compared with TDPD, we concluded that the ADPD was superior to the TDPD in the middle high frequency field, and the main parameters influencing the performance of the damper were the damping stiffness, orifice flow coefficient, pre-charge pressure, and the volume of the damper accumulator.
2015-01-01
Background: Muscle weakness especially weakness of the respiratory muscles is a complication of chronic kidney disease. The cause of muscle weakness is the accumulation of excessive amounts of urea and other toxins. The aim of this study was to assess the effect of hemodialysis on respiratory muscle strength by measuring maximum inspiratory (PI max) and expiratory pressure (PE max). Materials and Methods: A cross sectional study was carried out on 31 patients with chronic kidney disease at Mo...
Li, X.; Chin, L. P.; Tankin, R. S.; Jackson, T.; Stutrud, J.; Switzer, G.
1991-07-01
Measurements were made of the droplet size and velocity distributions in a hollow cone spray from a pressure atomizer using a phase/Doppler particle analyzer. The maximum entropy principle is used to predict these distributions. The constraints imposed in this model involve conversation of mass, momentum, and energy. Estimates of the source terms associated with these constraints are made based on physical reasoning. Agreement between the measurements and the predictions is very good.
Dynamic Product Assembly and Inventory Control for Maximum Profit
Neely, Michael J
2010-01-01
We consider a manufacturing plant that purchases raw materials for product assembly and then sells the final products to customers. There are M types of raw materials and K types of products, and each product uses a certain subset of raw materials for assembly. The plant operates in slotted time, and every slot it makes decisions about re-stocking materials and pricing the existing products in reaction to (possibly time-varying) material costs and consumer demands. We develop a dynamic purchasing and pricing policy that yields time average profit within epsilon of optimality, for any given epsilon>0, with a worst case storage buffer requirement that is O(1/epsilon). The policy can be implemented easily for large M, K, yields fast convergence times, and is robust to non-ergodic system dynamics.
Tune optimization for maximum dynamic acceptance; 1, formulation
Talman, R
1998-01-01
In order to combine the acceptance limitation due to a mechanical obstacle at radius rmech with that due to magnetic imperfections present in the lattice, a quantity eda to be called ``dynamic accepta nce'' is introduced. Using lowest order theory (with transfer matrices and no Hamiltionian) perturbed linear betatron motion is calculated and used to derive the dependence eda(rmech). Being in analyt ic form, this acceptance reduction provides a figure of merit that can be used to optimize the lattice tunes (thereby refining the prescription ``stay away from low order resonances''). Apart from its definition as an acceptance rather than an aperture, what distinguishes eda(rmech )from the commonly employed ``dynamic aperture'' is its dependence on rmech and the importance of this distinction fad es as rmech becomes large. In this Part~I the method is formulated and, to demonstrate the method, optimal fractional tunes are found with only random errors present-the loss of acceptance is dominate d by sextupole erro...
Leaf Dynamics of Panicum maximum under Future Climatic Changes.
Carlos Henrique Britto de Assis Prado
Full Text Available Panicum maximum Jacq. 'Mombaça' (C4 was grown in field conditions with sufficient water and nutrients to examine the effects of warming and elevated CO2 concentrations during the winter. Plants were exposed to either the ambient temperature and regular atmospheric CO2 (Control; elevated CO2 (600 ppm, eC; canopy warming (+2°C above regular canopy temperature, eT; or elevated CO2 and canopy warming (eC+eT. The temperatures and CO2 in the field were controlled by temperature free-air controlled enhancement (T-FACE and mini free-air CO2 enrichment (miniFACE facilities. The most green, expanding, and expanded leaves and the highest leaf appearance rate (LAR, leaves day(-1 and leaf elongation rate (LER, cm day(-1 were observed under eT. Leaf area and leaf biomass were higher in the eT and eC+eT treatments. The higher LER and LAR without significant differences in the number of senescent leaves could explain why tillers had higher foliage area and leaf biomass in the eT treatment. The eC treatment had the lowest LER and the fewest expanded and green leaves, similar to Control. The inhibitory effect of eC on foliage development in winter was indicated by the fewer green, expanded, and expanding leaves under eC+eT than eT. The stimulatory and inhibitory effects of the eT and eC treatments, respectively, on foliage raised and lowered, respectively, the foliar nitrogen concentration. The inhibition of foliage by eC was confirmed by the eC treatment having the lowest leaf/stem biomass ratio and by the change in leaf biomass-area relationships from linear or exponential growth to rectangular hyperbolic growth under eC. Besides, eC+eT had a synergist effect, speeding up leaf maturation. Therefore, with sufficient water and nutrients in winter, the inhibitory effect of elevated CO2 on foliage could be partially offset by elevated temperatures and relatively high P. maximum foliage production could be achieved under future climatic change.
Leaf Dynamics of Panicum maximum under Future Climatic Changes.
Britto de Assis Prado, Carlos Henrique; Haik Guedes de Camargo-Bortolin, Lívia; Castro, Érique; Martinez, Carlos Alberto
2016-01-01
Panicum maximum Jacq. 'Mombaça' (C4) was grown in field conditions with sufficient water and nutrients to examine the effects of warming and elevated CO2 concentrations during the winter. Plants were exposed to either the ambient temperature and regular atmospheric CO2 (Control); elevated CO2 (600 ppm, eC); canopy warming (+2°C above regular canopy temperature, eT); or elevated CO2 and canopy warming (eC+eT). The temperatures and CO2 in the field were controlled by temperature free-air controlled enhancement (T-FACE) and mini free-air CO2 enrichment (miniFACE) facilities. The most green, expanding, and expanded leaves and the highest leaf appearance rate (LAR, leaves day(-1)) and leaf elongation rate (LER, cm day(-1)) were observed under eT. Leaf area and leaf biomass were higher in the eT and eC+eT treatments. The higher LER and LAR without significant differences in the number of senescent leaves could explain why tillers had higher foliage area and leaf biomass in the eT treatment. The eC treatment had the lowest LER and the fewest expanded and green leaves, similar to Control. The inhibitory effect of eC on foliage development in winter was indicated by the fewer green, expanded, and expanding leaves under eC+eT than eT. The stimulatory and inhibitory effects of the eT and eC treatments, respectively, on foliage raised and lowered, respectively, the foliar nitrogen concentration. The inhibition of foliage by eC was confirmed by the eC treatment having the lowest leaf/stem biomass ratio and by the change in leaf biomass-area relationships from linear or exponential growth to rectangular hyperbolic growth under eC. Besides, eC+eT had a synergist effect, speeding up leaf maturation. Therefore, with sufficient water and nutrients in winter, the inhibitory effect of elevated CO2 on foliage could be partially offset by elevated temperatures and relatively high P. maximum foliage production could be achieved under future climatic change.
Constrained maximum likelihood modal parameter identification applied to structural dynamics
El-Kafafy, Mahmoud; Peeters, Bart; Guillaume, Patrick; De Troyer, Tim
2016-05-01
A new modal parameter estimation method to directly establish modal models of structural dynamic systems satisfying two physically motivated constraints will be presented. The constraints imposed in the identified modal model are the reciprocity of the frequency response functions (FRFs) and the estimation of normal (real) modes. The motivation behind the first constraint (i.e. reciprocity) comes from the fact that modal analysis theory shows that the FRF matrix and therefore the residue matrices are symmetric for non-gyroscopic, non-circulatory, and passive mechanical systems. In other words, such types of systems are expected to obey Maxwell-Betti's reciprocity principle. The second constraint (i.e. real mode shapes) is motivated by the fact that analytical models of structures are assumed to either be undamped or proportional damped. Therefore, normal (real) modes are needed for comparison with these analytical models. The work done in this paper is a further development of a recently introduced modal parameter identification method called ML-MM that enables us to establish modal model that satisfies such motivated constraints. The proposed constrained ML-MM method is applied to two real experimental datasets measured on fully trimmed cars. This type of data is still considered as a significant challenge in modal analysis. The results clearly demonstrate the applicability of the method to real structures with significant non-proportional damping and high modal densities.
Moes, C.C.M.
2007-01-01
The pressure distribution and the location of the points of maximum pressure, usually below the ischial tuberosities, was measured for subjects sitting on a flat, hard and horizontal support, and varying angle of the rotation of the pelvis. The pressure data were analyzed for force- and pressure-rel
Towards a shock tube method for the dynamic calibration of pressure sensors.
Downes, Stephen; Knott, Andy; Robinson, Ian
2014-08-28
In theory, shock tubes provide a pressure change with a very fast rise time and calculable amplitude. This pressure step could provide the basis for the calibration of pressure transducers used in highly dynamic applications. However, conventional metal shock tubes can be expensive, unwieldy and difficult to modify. We describe the development of a 1.4 MPa (maximum pressure) shock tube made from unplasticized polyvinyl chloride pressure tubing which provides a low-cost, light and easily modifiable basis for establishing a method for determining the dynamic characteristics of pressure sensors.
Ungar, Eugene K.; Richards, W. Lance
2015-01-01
The aircraft-based Stratospheric Observatory for Infrared Astronomy (SOFIA) is a platform for multiple infrared astronomical observation experiments. These experiments carry sensors cooled to liquid helium temperatures. The liquid helium supply is contained in large (i.e., 10 liters or more) vacuum-insulated dewars. Should the dewar vacuum insulation fail, the inrushing air will condense and freeze on the dewar wall, resulting in a large heat flux on the dewar's contents. The heat flux results in a rise in pressure and the actuation of the dewar pressure relief system. A previous NASA Engineering and Safety Center (NESC) assessment provided recommendations for the wall heat flux that would be expected from a loss of vacuum and detailed an appropriate method to use in calculating the maximum pressure that would occur in a loss of vacuum event. This method involved building a detailed supercritical helium compressible flow thermal/fluid model of the vent stack and exercising the model over the appropriate range of parameters. The experimenters designing science instruments for SOFIA are not experts in compressible supercritical flows and do not generally have access to the thermal/fluid modeling packages that are required to build detailed models of the vent stacks. Therefore, the SOFIA Program engaged the NESC to develop a simplified methodology to estimate the maximum pressure in a liquid helium dewar after the loss of vacuum insulation. The method would allow the university-based science instrument development teams to conservatively determine the cryostat's vent neck sizing during preliminary design of new SOFIA Science Instruments. This report details the development of the simplified method, the method itself, and the limits of its applicability. The simplified methodology provides an estimate of the dewar pressure after a loss of vacuum insulation that can be used for the initial design of the liquid helium dewar vent stacks. However, since it is not an exact
Moes, C.C.M.
2007-01-01
The pressure distribution and the location of the points of maximum pressure, usually below the ischial tuberosities, was measured for subjects sitting on a flat, hard and horizontal support, and varying angle of the rotation of the pelvis. The pressure data were analyzed for force- and
Benício, Kadja; Dias, Fernando A. L.; Gualdi, Lucien P.; Aliverti, Andrea; Resqueti, Vanessa R.; Fregonezi, Guilherme A. F.
2015-01-01
OBJECTIVE: To assess the influence of diaphragmatic activation control (diaphC) on Sniff Nasal-Inspiratory Pressure (SNIP) and Maximum Relaxation Rate of inspiratory muscles (MRR) in healthy subjects. METHOD: Twenty subjects (9 male; age: 23 (SD=2.9) years; BMI: 23.8 (SD=3) kg/m2; FEV1/FVC: 0.9 (SD=0.1)] performed 5 sniff maneuvers in two different moments: with or without instruction on diaphC. Before the first maneuver, a brief explanation was given to the subjects on how to perform the sniff test. For sniff test with diaphC, subjects were instructed to perform intense diaphragm activation. The best SNIP and MRR values were used for analysis. MRR was calculated as the ratio of first derivative of pressure over time (dP/dtmax) and were normalized by dividing it by peak pressure (SNIP) from the same maneuver. RESULTS: SNIP values were significantly different in maneuvers with and without diaphC [without diaphC: -100 (SD=27.1) cmH2O/ with diaphC: -72.8 (SD=22.3) cmH2O; p<0.0001], normalized MRR values were not statistically different [without diaphC: -9.7 (SD=2.6); with diaphC: -8.9 (SD=1.5); p=0.19]. Without diaphC, 40% of the sample did not reach the appropriate sniff criteria found in the literature. CONCLUSION: Diaphragmatic control performed during SNIP test influences obtained inspiratory pressure, being lower when diaphC is performed. However, there was no influence on normalized MRR. PMID:26578254
Takeda, Osamu; Iwamoto, Hirone; Sakashita, Ryota; Iseki, Chiaki; Zhu, Hongmin
2017-07-01
A surface tension measurement method based on the maximum bubble pressure (MBP) method was developed in order to precisely determine the surface tension of molten silicates in this study. Specifically, the influence of viscosity on surface tension measurements was quantified, and the criteria for accurate measurement were investigated. It was found that the MBP apparently increased with an increase in viscosity. This was because extra pressure was required for the flowing liquid inside the capillary due to viscous resistance. It was also expected that the extra pressure would decrease by decreasing the fluid velocity. For silicone oil with a viscosity of 1000 \\hbox {mPa}{\\cdot }\\hbox {s}, the error on the MBP could be decreased to +1.7 % by increasing the bubble detachment time to 300 \\hbox {s}. However, the error was still over 1 % even when the bubble detachment time was increased to 600 \\hbox {s}. Therefore, a true value of the MBP was determined by using a curve-fitting technique with a simple relaxation function, and that was succeeded for silicone oil at 1000 \\hbox {mPa}{\\cdot } \\hbox {s} of viscosity. Furthermore, for silicone oil with a viscosity as high as 10 000 \\hbox {mPa}{\\cdot }\\hbox {s}, the apparent MBP approached a true value by interrupting the gas introduction during the pressure rising period and by re-introducing the gas at a slow flow rate. Based on the fundamental investigation at room temperature, the surface tension of the \\hbox {SiO}2-40 \\hbox {mol}%\\hbox {Na}2\\hbox {O} and \\hbox {SiO}2-50 \\hbox {mol}%\\hbox {Na}2\\hbox {O} melts was determined at a high temperature. The obtained value was slightly lower than the literature values, which might be due to the influence of viscosity on surface tension measurements being removed in this study.
Effect of consolidation ratios on maximum dynamic shear modulus of sands
Yuan Xiaoming; Sun Jing; Sun Rui
2005-01-01
The dynamic shear modulus (DSM) is the most basic soil parameter in earthquake or other dynamic loading conditions and can be obtained through testing in the field or in the laboratory. The effect of consolidation ratios on the maximum DSM for two types of sand is investigated by using resonant column tests. And, an increment formula to obtain the maximum DSM for cases of consolidation ratio kc＞1 is presented. The results indicate that the maximum DSM rises rapidly when kc is near 1 and then slows down, which means that the power function of the consolidation ratio increment kc-1 can be used to describe the variation of the maximum DSM due to kc＞1. The results also indicate that the increase in the maximum DSM due to kc＞1 is significantly larger than that predicted by Hardin and Black's formula.
Dynamic material strength measurement utilizing magnetically applied pressure-shear
Alexander C.S.
2012-08-01
Full Text Available Magnetically applied pressure-shear (MAPS is a recently developed technique used to measure dynamic material strength developed at Sandia National Laboratories utilizing magneto-hydrodynamic (MHD drive pulsed power systems. MHD drive platforms generate high pressures by passing a large current through a pair of parallel plate conductors which, in essence, form a single turn magnet coil. Lorentz forces resulting from the interaction of the self-generated magnetic field and the drive current repel the plates and result in a high pressure ramp wave propagating in the conductors. This is the principle by which the Sandia Z Machine operates for dynamic material testing. MAPS relies on the addition of a second, external magnetic field applied orthogonally to both the drive current and the self-generated magnetic field. The interaction of the drive current and this external field results in a shear wave being induced directly in the conductors. Thus both longitudinal and shear stresses are generated. These stresses are coupled to a sample material of interest where shear strength is probed by determining the maximum transmissible shear stress in the state defined by the longitudinal compression. Both longitudinal and transverse velocities are measured via a specialized velocity interferometer system for any reflector (VISAR. Pressure and shear strength of the sample are calculated directly from the VISAR data. Results of tests on several materials at modest pressures (∼10GPa will be presented and discussed.
Dynamic active earth pressure on retaining structures
Deepankar Choudhury; Santiram Chatterjee
2006-12-01
Earth-retaining structures constitute an important topic of research in civil engineering, more so under earthquake conditions. For the analysis and design of retaining walls in earthquake-prone zones, accurate estimation of dynamic earth pressures is very important. Conventional methods either use pseudo-static approaches of analysis even for dynamic cases or a simple single-degree of freedom model for the retaining wall–soil system. In this paper, a simpliﬁed two-degree of freedom mass–spring–dashpot (2-DOF) dynamic model has been proposed to estimate the active earth pressure at the back of the retaining walls for translation modes of wall movement under seismic conditions. The horizontal zone of inﬂuence on dynamic earth force on the wall is estimated. Results in terms of displacement, velocity and acceleration-time history are presented for some typical cases, which show the ﬁnal movement of the wall in terms of wall height, which is required for the design. The non-dimensional design chart proposed in the present study can be used to compute the total dynamic earth force on the wall under different input ground motion and backﬁll conditions. Finally, the results obtained have been compared with those of the available Scott model and the merits of the present results have been discussed.
Computational design of hepatitis C vaccines using maximum entropy models and population dynamics
Hart, Gregory; Ferguson, Andrew
Hepatitis C virus (HCV) afflicts 170 million people and kills 350,000 annually. Vaccination offers the most realistic and cost effective hope of controlling this epidemic. Despite 20 years of research, no vaccine is available. A major obstacle is the virus' extreme genetic variability and rapid mutational escape from immune pressure. Improvements in the vaccine design process are urgently needed. Coupling data mining with spin glass models and maximum entropy inference, we have developed a computational approach to translate sequence databases into empirical fitness landscapes. These landscapes explicitly connect viral genotype to phenotypic fitness and reveal vulnerable targets that can be exploited to rationally design immunogens. Viewing these landscapes as the mutational ''playing field'' over which the virus is constrained to evolve, we have integrated them with agent-based models of the viral mutational and host immune response dynamics, establishing a data-driven immune simulator of HCV infection. We have employed this simulator to perform in silico screening of HCV immunogens. By systematically identifying a small number of promising vaccine candidates, these models can accelerate the search for a vaccine by massively reducing the experimental search space.
High Temperature Dynamic Pressure Measurements Using Silicon Carbide Pressure Sensors
Okojie, Robert S.; Meredith, Roger D.; Chang, Clarence T.; Savrun, Ender
2014-01-01
Un-cooled, MEMS-based silicon carbide (SiC) static pressure sensors were used for the first time to measure pressure perturbations at temperatures as high as 600 C during laboratory characterization, and subsequently evaluated in a combustor rig operated under various engine conditions to extract the frequencies that are associated with thermoacoustic instabilities. One SiC sensor was placed directly in the flow stream of the combustor rig while a benchmark commercial water-cooled piezoceramic dynamic pressure transducer was co-located axially but kept some distance away from the hot flow stream. In the combustor rig test, the SiC sensor detected thermoacoustic instabilities across a range of engine operating conditions, amplitude magnitude as low as 0.5 psi at 585 C, in good agreement with the benchmark piezoceramic sensor. The SiC sensor experienced low signal to noise ratio at higher temperature, primarily due to the fact that it was a static sensor with low sensitivity.
Vasile Cojocaru
2016-12-01
Full Text Available Several methods can be used in the FEM studies to apply the loads on a plain bearing. The paper presents a comparative analysis of maximum stress obtained for three loading scenarios: resultant force applied on the shaft – bearing assembly, variable pressure with sinusoidal distribution applied on the bearing surface, variable pressure with parabolic distribution applied on the bearing surface.
Kiviet, J.F.; Phillips, G.D.A.
2014-01-01
In dynamic regression models conditional maximum likelihood (least-squares) coefficient and variance estimators are biased. Using expansion techniques an approximation is obtained to the bias in variance estimation yielding a bias corrected variance estimator. This is achieved for both the standard
Maximum Likelihood Dynamic Factor Modeling for Arbitrary "N" and "T" Using SEM
Voelkle, Manuel C.; Oud, Johan H. L.; von Oertzen, Timo; Lindenberger, Ulman
2012-01-01
This article has 3 objectives that build on each other. First, we demonstrate how to obtain maximum likelihood estimates for dynamic factor models (the direct autoregressive factor score model) with arbitrary "T" and "N" by means of structural equation modeling (SEM) and compare the approach to existing methods. Second, we go beyond standard time…
Jingtao Shi
2013-01-01
Full Text Available This paper is concerned with the relationship between maximum principle and dynamic programming for stochastic recursive optimal control problems. Under certain differentiability conditions, relations among the adjoint processes, the generalized Hamiltonian function, and the value function are given. A linear quadratic recursive utility portfolio optimization problem in the financial engineering is discussed as an explicitly illustrated example of the main result.
Hodder, Joanne N; Keir, Peter J
2013-10-01
Muscle specific maximal voluntary isometric contractions (MVIC) are commonly used to elicit reference amplitudes to normalize electromyographic signals (EMG). It has been questioned whether this is appropriate for normalizing EMG from dynamic contractions. This study compares EMG amplitude when shoulder muscle activity from dynamic contractions is normalized to isometric and isokinetic maximal excitation as well as a hybrid approach currently used in our laboratory. Anterior, middle and posterior deltoid, upper and lower trapezius, pectoralis major, latissimus dorsi and infraspinatus were monitored during (1) manually resisted MVICs, and (2) maximum voluntary dynamic concentric contractions (MVDC) on an isokinetic dynamometer. Dynamic contractions were performed (a) at 30°/s about the longitudinal, frontal and sagittal axes of the shoulder, and (b) during manual bi-rotation of a tilted wheel at 120°/s. EMG from the wheel task was normalized to the maximum excitation from (i) the muscle specific MVIC, (ii) from any MVIC (MVICALL), (iii) for any MVDC, (iv) from any exertion (maximum experimental excitation, MEE). Mean EMG from the wheel task was up to 45% greater when normalized to muscle specific isometric contractions (method i) than when normalized to MEE (method iv). Seventy-five percent of MEE's occurred during MVDCs. This study presents an 20 useful and effective process for obtaining the greatest excitation from the shoulder muscles when normalizing dynamic efforts.
Igarashi, Yasuhiko; Hori, Takane; Murata, Shin; Sato, Kenichiro; Baba, Toshitaka; Okada, Masato
2016-12-01
We constructed a model to predict the maximum tsunami height by a Gaussian process (GP) that uses pressure gauge data from the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) in the Nankai trough. We found a greatly improved generalization error of the maximum tsunami height by our prediction model. The error is about one third of that by a previous method, which tends to make larger predictions, especially for large tsunami heights (>10 m). These results indicate that GP enables us to get a more accurate prediction of tsunami height by using pressure gauge data.
Molecular dynamics of liquid SiO2 under high pressure
Rustad, James R.; Yuen, David A.; Spera, Frank J.
1990-01-01
The molecular dynamics of pure SiO2 liquids was investigated up to pressures of 20 GPa at 4000 K using 252, 498, 864, and 1371 particles. The results obtained suggest that the pressure-induced maxima in the self-diffusion coefficients of both oxygen and silicon are dependent on the system size. In the case of larger systems, the maximum decreases and shifts to lower pressures. Changes in the velocity autocorrelation function with increasing pressure are described. The populations of anomalously coordinated silicon and oxygen are then discussed as a function of pressure and system size.
Molecular dynamics of liquid SiO2 under high pressure
Rustad, James R.; Yuen, David A.; Spera, Frank J.
1990-01-01
The molecular dynamics of pure SiO2 liquids was investigated up to pressures of 20 GPa at 4000 K using 252, 498, 864, and 1371 particles. The results obtained suggest that the pressure-induced maxima in the self-diffusion coefficients of both oxygen and silicon are dependent on the system size. In the case of larger systems, the maximum decreases and shifts to lower pressures. Changes in the velocity autocorrelation function with increasing pressure are described. The populations of anomalously coordinated silicon and oxygen are then discussed as a function of pressure and system size.
Ungar, Eugene K.
2014-01-01
The aircraft-based Stratospheric Observatory for Infrared Astronomy (SOFIA) is a platform for multiple infrared observation experiments. The experiments carry sensors cooled to liquid helium (LHe) temperatures. A question arose regarding the heat input and peak pressure that would result from a sudden loss of the dewar vacuum insulation. Owing to concerns about the adequacy of dewar pressure relief in the event of a sudden loss of the dewar vacuum insulation, the SOFIA Program engaged the NASA Engineering and Safety Center (NESC). This report summarizes and assesses the experiments that have been performed to measure the heat flux into LHe dewars following a sudden vacuum insulation failure, describes the physical limits of heat input to the dewar, and provides an NESC recommendation for the wall heat flux that should be used to assess the sudden loss of vacuum insulation case. This report also assesses the methodology used by the SOFIA Program to predict the maximum pressure that would occur following a loss of vacuum event.
Shin, Dong In; Lim, Eun Mo; Huh, Nam Su [Seoul National Univ. of Science and Technology, Seoul (Korea, Republic of); Choi, Shin Beom; Yu, Je Yong; Kim, Ji Ho; Choi, Suhn [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-10-15
A structural integrity of steam generator tubes of nuclear power plants is one of crucial parameters for safe operation of nuclear power plants. Thus, many studies have been made to provide engineering methods to assess integrity of defective tubes of commercial nuclear power plants considering its operating environments and defect characteristics. As described above, the geometric and operating conditions of steam generator tubes in integral reactor are significantly different from those of commercial reactor. Therefore, the structural integrity assessment of defective tubes of integral reactor taking into account its own operating conditions and geometric characteristics, i. e., external pressure and helically coiled shape, should be made to demonstrate compliance with the current design criteria. Also, ovality is very specific characteristics of the helically coiled tube because it is occurred during the coiling processes. The wear, occurring from FIV (Flow Induced Vibration) and so on, is main degradation of steam generator tube. In the present study, maximum external pressure of helically coiled steam generator tube with wear is predicted based on the detailed 3-dimensional finite element analysis. As for shape of wear defect, the rectangular shape is considered. In particular, the effect of ovality on the maximum external pressure of helically coiled tubes with rectangular shaped wear is investigated. In the present work, the maximum external pressure of helically coiled steam generator tube with rectangular shaped wear is investigated via detailed 3-D FE analyses. In order to cover a practical range of geometries for defective tube, the variables affecting the maximum external pressure were systematically varied. In particular, the effect of tube ovality on the maximum external pressure is evaluated. It is expected that the present results can be used as a technical backgrounds for establishing a practical structural integrity assessment guideline of
Jumper, John M; Sosnick, Tobin R
2016-01-01
To address the large gap between time scales that can be easily reached by molecular simulations and those required to understand protein dynamics, we propose a new methodology that computes a self-consistent approximation of the side chain free energy at every integration step. In analogy with the adiabatic Born-Oppenheimer approximation in which the nuclear dynamics are governed by the energy of the instantaneously-equilibrated electronic degrees of freedom, the protein backbone dynamics are simulated as preceding according to the dictates of the free energy of an instantaneously-equilibrated side chain potential. The side chain free energy is computed on the fly; hence, the protein backbone dynamics traverse a greatly smoothed energetic landscape, resulting in extremely rapid equilibration and sampling of the Boltzmann distribution. Because our method employs a reduced model involving single-bead side chains, we also provide a novel, maximum-likelihood type method to parameterize the side chain model using...
Ariane Martins
2010-08-01
Full Text Available The relationship between force and balance show controversy results and has directimplications in exercise prescription practice. The objective was to investigate the relationshipbetween maximum dynamic force (MDF of inferior limbs and the static and dynamic balances.Participated in the study 60 individuals, with 18 to 24 years old, strength training apprentices.The MDF was available by mean the One Maximum Repetition (1MR in “leg press” and “kneeextension” and motor testes to available of static and dynamic balances. The correlation testsand multiple linear regression were applied. The force and balance variables showed correlationin females (p=0.038. The corporal mass and static balance showed correlation for the males(p=0.045. The explication capacity at MDF and practices time were small: 13% for staticbalance in males, 18% and 17%, respectively, for static and dynamic balance in females. Inconclusion: the MDF of inferior limbs showed low predictive capacity for performance in staticand dynamic balances, especially for males.
CFD modeling of the IRIS pressurizer dynamic
Sanz, Ronny R.; Montesinos, Maria E.; Garcia, Carlos; Bueno, Elizabeth D.; Mazaira, Leorlen R., E-mail: rsanz@instec.cu, E-mail: mmontesi@instec.cu, E-mail: cgh@instec.cu, E-mail: leored1984@gmail.com [Instituto Superior de Tecnologias y Ciencias Aplicadas (InSTEC), La Habana (Cuba); Bezerra, Jair L.; Lira, Carlos A.B. Oliveira, E-mail: jair.lima@ufpe.br, E-mail: cabol@ufpe.br [Universida Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear
2015-07-01
Integral layout of nuclear reactor IRIS makes possible the elimination of the spray system, which is usually used to mitigate in-surge transient and also help to Boron homogenization. The study of transients with deficiencies in the Boron homogenization in this technology is very important, because they can cause disturbances in the reactor power and insert a strong reactivity in the core. The detailed knowledge of the behavior of multiphase multicomponent flows is challenging due to the complex phenomena and interactions at the interface. In this context, the CFD modeling is employed in the design of equipment in the nuclear industry as it allows predicting accidents or predicting their performance in dissimilar applications. The aim of the present research is to model the IRIS pressurizer's dynamic using the commercial CFD code CFX. A symmetric tri dimensional model equivalent to 1/8 of the total geometry was adopted to reduce mesh size and minimize processing time. The model considers the coexistence of four phases and also takes into account the heat losses. The relationships for interfacial mass, energy, and momentum transport are programmed and incorporated into CFX. Moreover, two subdomains and several additional variables are defined to monitoring the boron dilution sequences and condensation-evaporation rates in different control volumes. For transient states a non - equilibrium stratification in the pressurizer is considered. This paper discusses the model developed and the behavior of the system for representative transients sequences. The results of analyzed transients of IRIS can be applied to the design of pressurizer internal structures and components. (author)
Kai Yan
2015-01-01
Full Text Available A predictive model for droplet size and velocity distributions of a pressure swirl atomizer has been proposed based on the maximum entropy formalism (MEF. The constraint conditions of the MEF model include the conservation laws of mass, momentum, and energy. The effects of liquid swirling strength, Weber number, gas-to-liquid axial velocity ratio and gas-to-liquid density ratio on the droplet size and velocity distributions of a pressure swirl atomizer are investigated. Results show that model based on maximum entropy formalism works well to predict droplet size and velocity distributions under different spray conditions. Liquid swirling strength, Weber number, gas-to-liquid axial velocity ratio and gas-to-liquid density ratio have different effects on droplet size and velocity distributions of a pressure swirl atomizer.
Bubble cloud dynamics in a high-pressure spherical resonator
Anderson, Phillip Andrew
A bubble cloud is a population of bubbles confined to a region within a fluid. Bubble clouds play a large role in a variety of naturally occurring phenomena and man-made applications (e.g., ocean noise, cavitation damage, sonoluminescence, ultrasonic cleaning, drug delivery, lithotripsy). It is important, therefore, to understand the behavior of bubble clouds so that their effects may be enhanced or diminished as desired. This work explores and characterizes the properties of bubble clouds nucleated inside a high-pressure spherical acoustic resonator, in connection with recent interest in acoustic inertial confinement fusion (acoustic ICF). A laser system was developed to repeatably nucleate a cloud of bubbles inside the resonator. The resulting events were then observed, primarily with schlieren imaging methods. Preliminary studies of the bubble cloud dynamics showed the sensitivity of the initial cloud to nucleation parameters including the phase of nucleation, the laser energy, and the acoustic power. After many acoustic cycles, some bubble clouds are observed to evolve into a tight cluster. The formation of these clusters correlates with initial bubble distributions which have a large cloud interaction parameter, β. Cluster dynamics are seen to be largely driven by reconverging shock waves from previous collapses reflected from the resonator's interior surface. Initial expansion of the cluster boundary is on the order of 8 mm/µs and the maximum radius approaches 3 mm. Shock pressures are estimated to be > 10 GPa at a radius of 100 µm using weak shock theory.
Maximum Simplified Dynamic Model of Grass Field Ecosystem With Two Variables
曾庆存; 卢佩生; 曾晓东
1994-01-01
Based on general consideration and analysis, a maximum simplified dynamic model of grass field ecosystem with a single species is developed. The model consists of two variables: grass biomass of grass field per unit area and soil wetness, and is suitable for describing their mutual interaction. Other factors such as physical-chemical characteristics of soil, precipitation, irrigation, sunlight, temperature and consumers, are taken into account as parameters in the dynamical system. Qualitative analysis of the model shows that grass biomass of a possible ecological regime is determined by the stable equilibrium state of the dynamical system. For the grass species interacting weakly with soil wetness the grass biomass continuously depends on the precipitation. While, for a species interacting strongly with soil wetness, grass biomass is abundant if precipitation is larger than some critical value; otherwise, it becomes a desertification regime with very little or even zero grass biomass. The model also sh
Dynamic soil feedbacks on the climate of the mid-Holocene and the Last Glacial Maximum
M. Stärz
2013-05-01
Full Text Available State-of-the-art general circulation models (GCMs are tested and challenged by the ability to reproduce paleoclimate key intervals. In order to account for climate changes associated with soil dynamics we have developed a soil scheme, which is asynchronously coupled to a state-of-the-art atmosphere ocean GCM with dynamic vegetation. We test the scheme for conditions representative of a warmer (mid-Holocene, 6 kyr before present, BP and colder (Last Glacial Maximum, 21 kyr BP than pre-industrial climate. The computed change of physical soil properties (i.e. albedo, water storage capacity, and soil texture for these different climates leads to amplified global climate anomalies. Especially regions like the transition zone of desert/savannah and taiga/tundra, exhibit an increased response as a result of the modified soil treatment. In comparison to earlier studies, the inclusion of the soil feedback pushes our model simulations towards the warmer end in the range of mid-Holocene studies and beyond current estimates of global cooling during the Last Glacial Maximum based on PMIP2 (Paleoclimate Modelling Intercomparison Project 2 studies. The main impact of the interactive soil scheme on the climate response is governed by positive feedbacks, including dynamics of vegetation, snow, sea ice, local water recycling, which might amplify forcing factors ranging from orbital to tectonic timescales.
Possible dynamical explanations for Paltridge's principle of maximum entropy production
Virgo, Nathaniel, E-mail: nathanielvirgo@gmail.com; Ikegami, Takashi, E-mail: nathanielvirgo@gmail.com [Ikegami Laboratory, University of Tokyo (Japan)
2014-12-05
Throughout the history of non-equilibrium thermodynamics a number of theories have been proposed in which complex, far from equilibrium flow systems are hypothesised to reach a steady state that maximises some quantity. Perhaps the most celebrated is Paltridge's principle of maximum entropy production for the horizontal heat flux in Earth's atmosphere, for which there is some empirical support. There have been a number of attempts to derive such a principle from maximum entropy considerations. However, we currently lack a more mechanistic explanation of how any particular system might self-organise into a state that maximises some quantity. This is in contrast to equilibrium thermodynamics, in which models such as the Ising model have been a great help in understanding the relationship between the predictions of MaxEnt and the dynamics of physical systems. In this paper we show that, unlike in the equilibrium case, Paltridge-type maximisation in non-equilibrium systems cannot be achieved by a simple dynamical feedback mechanism. Nevertheless, we propose several possible mechanisms by which maximisation could occur. Showing that these occur in any real system is a task for future work. The possibilities presented here may not be the only ones. We hope that by presenting them we can provoke further discussion about the possible dynamical mechanisms behind extremum principles for non-equilibrium systems, and their relationship to predictions obtained through MaxEnt.
Dynamic Programming and Error Estimates for Stochastic Control Problems with Maximum Cost
Bokanowski, Olivier, E-mail: boka@math.jussieu.fr [Laboratoire Jacques-Louis Lions, Université Paris-Diderot (Paris 7) UFR de Mathématiques - Bât. Sophie Germain (France); Picarelli, Athena, E-mail: athena.picarelli@inria.fr [Projet Commands, INRIA Saclay & ENSTA ParisTech (France); Zidani, Hasnaa, E-mail: hasnaa.zidani@ensta.fr [Unité de Mathématiques appliquées (UMA), ENSTA ParisTech (France)
2015-02-15
This work is concerned with stochastic optimal control for a running maximum cost. A direct approach based on dynamic programming techniques is studied leading to the characterization of the value function as the unique viscosity solution of a second order Hamilton–Jacobi–Bellman (HJB) equation with an oblique derivative boundary condition. A general numerical scheme is proposed and a convergence result is provided. Error estimates are obtained for the semi-Lagrangian scheme. These results can apply to the case of lookback options in finance. Moreover, optimal control problems with maximum cost arise in the characterization of the reachable sets for a system of controlled stochastic differential equations. Some numerical simulations on examples of reachable analysis are included to illustrate our approach.
Stysley, Paul; Coyle, Barry; Clarke, Greg; Poulios, Demetrios; Kay, Richard
2015-01-01
The Global Ecosystems Dynamics Investigation (GEDI) is a planned mission sending a LIDAR instrument to the International Space Station that will employ three NASA laser transmitters. This instrument will produce parallel tracks on the Earth's surface that will provide global 3D vegetation canopy measurements. To meet the mission goals a total of 5 High Output Maximum Efficiency Resonator lasers will to be built (1 ETU + 3 Flight + 1 spare) in-house at NASA-GSFC. This presentation will summarize the HOMER design, the testing the design has completed in the past, and the plans to successfully build the units needed for the GEDI mission.
Dynamics of a multi-mode maximum entangled coherent state over an amplitude damping channel
A. E1 Allati; Y. Hassouni; N. Metwally
2011-01-01
The dynamics of the maximum entangled coherent state traveling through an amplitude damping channel is investigated.For small values of the transmissivity rate,the traveling state is very fragile to this noise channel,which suffers from the phase flip error with high probability. The entanglement decays smoothly for larger values of the transmissivity rate and speedily for smaller values of this rate.As the number of modes increases,the traveling state over this noise channel quickly loses its entanglement.The odd and even states vanish at the same value of field intensity.
Dynamics of multi-modes maximum entangled coherent state over amplitude damping channel
Allati, A El; Metwally, N
2012-01-01
The dynamics of maximum entangled coherent state travels through an amplitude damping channel is investigated. For small values of the transmissivity rate the travelling state is very fragile to this noise channel, where it suffers from the phase flip error with high probability. The entanglement decays smoothly for larger values of the transmissivity rate and speedily for smaller values of this rate. As the number of modes increases, the travelling state over this noise channel loses its entanglement hastily. The odd and even states vanish at the same value of the field intensity.
Magnetospheric Cavity Modes Driven by Solar Wind Dynamic Pressure Fluctuations
Claudepierre, S G; Elkington, S R; Lotko, W; Hudson, M K; 10.1029/2009GL039045
2010-01-01
We present results from Lyon-Fedder-Mobarry (LFM) global, three-dimensional magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere interaction. We use these simulations to investigate the role that solar wind dynamic pressure fluctuations play in the generation of magnetospheric ultra-low frequency (ULF) pulsations. The simulations presented in this study are driven with idealized solar wind input conditions. In four of the simulations, we introduce monochromatic ULF fluctuations in the upstream solar wind dynamic pressure. In the fifth simulation, we introduce a continuum of ULF frequencies in the upstream solar wind dynamic pressure fluctuations. In this numerical experiment, the idealized nature of the solar wind driving conditions allows us to study the magnetospheric response to only a fluctuating upstream dynamic pressure, while holding all other solar wind driving parameters constant. The simulation results suggest that ULF fluctuations in the solar wind dynamic pressure can drive magnet...
Dynamic High-Pressure Behavior of Hierarchical Heterogeneous Geological Materials
2016-04-01
pressure -density Hugoniot plots for simulations using the ‘mix 5’ option, as will be presented later. The volume weighted option for mixed cells (refered...AFRL-AFOSR-VA-TR-2016-0150 Dynamic High- Pressure Behavior of Geological Materials Naresh Thadhani GEORGIA TECH RESEARCH CORPORATION Final Report 04...31-12-2015 4. TITLE AND SUBTITLE Dynamic High- Pressure Behavior of Hierarchical Heterogeneous Geological Materials 5a. CONTRACT NUMBER 5b. GRANT
SU-E-T-444: Gravity Effect On Maximum Leaf Speed in Dynamic IMRT Treatments
Olasolo, J; Pellejero, S; Gracia, M; Gallardo, N; Martin, ML; Lozares, S; Maneru, F; Bragado, L; Miquelez, S [Complejo Hospitalario de Navarra, Pamplona (Spain); Artacho, JM [Universidad de Zaragoza, Zaragoza (Spain)
2015-06-15
Purpose: A leaf sequencing algorithm has been recently developed in our department. Our purpose is to utilize this algorithm to reduce treatment time by studying the feasibility of using several maximum leaf speeds depending on gantry angle and leaf thickness (0.5 or 1 cm at isocenter). To do so, the gravity effect on MLC performance has been examined by means of analysing the dynalog files. Methods: Leaf position errors has been ascertained according to gantry angle and leaf speed in MLC Millenium120 (Varian). In order to do this, the following test has been designed: all leaves move in synchrony, with same speed and 1 cm gap between opposite leaves. This test is implemented for 18 different speeds: 0.25-0.5-0.75-1-1.25-1.5-1.75-2-2.1-2.2-2.3-2.4-2.5-2.6-2.7-2.8-2.9-3.0 cm/s and 8 gantry angles: 0-45-90-135-180-225-270-315. Collimator angle is 2 degrees in all cases since it is the most usual one in IMRT treatments in our department. Dynamic tolerance is 2 mm. Dynalogs files of 10 repetitions of the test are analysed with a Mathlab in-house developed software and RMS error and 95th percentiles are calculated. Varian recommends 2.5 cm/s as the maximum leaf speed for its segmentation algorithm. In our case, we accept this speed in the most restrictive situation: gantry angle 270 and 1 cm leaf thickness. Maximum speeds for the rest of the cases are calculated by keeping the difference between 95th percentile and dynamic tolerance. In this way, beam hold-off probability does not increase. Results: Maximum speeds every 45 degrees of gantry rotation have been calculated for both leaf thickness. These results are 2.9-2.9-2.9-2.9-2.7-2.6-2.6-2.7 cm/s for 0.5 cm leaf thickness and 2.7-2.7-2.7-2.7-2.6-2.5-2.5-2.6 cm/s for 1 cm leaf thickness. Conclusion: Gravity effect on MLC positioning has been studied. Maximum leaf speed according to leaf thickness and gantry angle have been calculated which reduces treatment time.
Thermodynamics, maximum power, and the dynamics of preferential river flow structures on continents
A. Kleidon
2012-06-01
Full Text Available The organization of drainage basins shows some reproducible phenomena, as exemplified by self-similar fractal river network structures and typical scaling laws, and these have been related to energetic optimization principles, such as minimization of stream power, minimum energy expenditure or maximum "access". Here we describe the organization and dynamics of drainage systems using thermodynamics, focusing on the generation, dissipation and transfer of free energy associated with river flow and sediment transport. We argue that the organization of drainage basins reflects the fundamental tendency of natural systems to deplete driving gradients as fast as possible through the maximization of free energy generation, thereby accelerating the dynamics of the system. This effectively results in the maximization of sediment export to deplete topographic gradients as fast as possible and potentially involves large-scale feedbacks to continental uplift. We illustrate this thermodynamic description with a set of three highly simplified models related to water and sediment flow and describe the mechanisms and feedbacks involved in the evolution and dynamics of the associated structures. We close by discussing how this thermodynamic perspective is consistent with previous approaches and the implications that such a thermodynamic description has for the understanding and prediction of sub-grid scale organization of drainage systems and preferential flow structures in general.
A. Kleidon
2013-01-01
Full Text Available The organization of drainage basins shows some reproducible phenomena, as exemplified by self-similar fractal river network structures and typical scaling laws, and these have been related to energetic optimization principles, such as minimization of stream power, minimum energy expenditure or maximum "access". Here we describe the organization and dynamics of drainage systems using thermodynamics, focusing on the generation, dissipation and transfer of free energy associated with river flow and sediment transport. We argue that the organization of drainage basins reflects the fundamental tendency of natural systems to deplete driving gradients as fast as possible through the maximization of free energy generation, thereby accelerating the dynamics of the system. This effectively results in the maximization of sediment export to deplete topographic gradients as fast as possible and potentially involves large-scale feedbacks to continental uplift. We illustrate this thermodynamic description with a set of three highly simplified models related to water and sediment flow and describe the mechanisms and feedbacks involved in the evolution and dynamics of the associated structures. We close by discussing how this thermodynamic perspective is consistent with previous approaches and the implications that such a thermodynamic description has for the understanding and prediction of sub-grid scale organization of drainage systems and preferential flow structures in general.
THE GENERALIZED MAXIMUM LIKELIHOOD METHOD APPLIED TO HIGH PRESSURE PHASE EQUILIBRIUM
Lúcio CARDOZO-FILHO
1997-12-01
Full Text Available The generalized maximum likelihood method was used to determine binary interaction parameters between carbon dioxide and components of orange essential oil. Vapor-liquid equilibrium was modeled with Peng-Robinson and Soave-Redlich-Kwong equations, using a methodology proposed in 1979 by Asselineau, Bogdanic and Vidal. Experimental vapor-liquid equilibrium data on binary mixtures formed with carbon dioxide and compounds usually found in orange essential oil were used to test the model. These systems were chosen to demonstrate that the maximum likelihood method produces binary interaction parameters for cubic equations of state capable of satisfactorily describing phase equilibrium, even for a binary such as ethanol/CO2. Results corroborate that the Peng-Robinson, as well as the Soave-Redlich-Kwong, equation can be used to describe phase equilibrium for the following systems: components of essential oil of orange/CO2.Foi empregado o método da máxima verossimilhança generalizado para determinação de parâmetros de interação binária entre os componentes do óleo essencial de laranja e dióxido de carbono. Foram usados dados experimentais de equilíbrio líquido-vapor de misturas binárias de dióxido de carbono e componentes do óleo essencial de laranja. O equilíbrio líquido-vapor foi modelado com as equações de Peng-Robinson e de Soave-Redlich-Kwong usando a metodologia proposta em 1979 por Asselineau, Bogdanic e Vidal. A escolha destes sistemas teve como objetivo demonstrar que o método da máxima verosimilhança produz parâmetros de interação binária, para equações cúbicas de estado capazes de descrever satisfatoriamente até mesmo o equilíbrio para o binário etanol/CO2. Os resultados comprovam que tanto a equação de Peng-Robinson quanto a de Soave-Redlich-Kwong podem ser empregadas para descrever o equilíbrio de fases para o sistemas: componentes do óleo essencial de laranja/CO2.
Evaluating CO2 and CH4 dynamics of Alaskan ecosystems during the Holocene Thermal Maximum
He, Yujie; Jones, Miriam C.; Zhuang, Qianlai; Bochicchio, Christopher; Felzer, B. S.; Mason, Erik; Yu, Zicheng
2014-01-01
The Arctic has experienced much greater warming than the global average in recent decades due to polar amplification. Warming has induced ecological changes that have impacted climate carbon-cycle feedbacks, making it important to understand the climate and vegetation controls on carbon (C) dynamics. Here we used the Holocene Thermal Maximum (HTM, 11–9 ka BP, 1 ka BP = 1000 cal yr before present) in Alaska as a case study to examine how ecosystem Cdynamics responded to the past warming climate using an integrated approach of combining paleoecological reconstructions and ecosystem modeling. Our paleoecological synthesis showed expansion of deciduous broadleaf forest (dominated by Populus) into tundra and the establishment of boreal evergreen needleleaf and mixed forest during the second half of the HTM under a warmer- and wetter-than-before climate, coincident with the occurrence of the highest net primary productivity, cumulative net ecosystem productivity, soil C accumulation and CH4 emissions. These series of ecological and biogeochemical shifts mirrored the solar insolation and subsequent temperature and precipitation patterns during HTM, indicating the importance of climate controls on C dynamics. Our simulated regional estimate of CH4 emission rates from Alaska during the HTM ranged from 3.5 to 6.4 Tg CH4 yr−1 and highest annual NPP of 470 Tg C yr−1, significantly higher than previously reported modern estimates. Our results show that the differences in static vegetation distribution maps used in simulations of different time slices have greater influence on modeled C dynamics than climatic fields within each time slice, highlighting the importance of incorporating vegetation community dynamics and their responses to climatic conditions in long-term biogeochemical modeling.
Modeling the Mass Action Dynamics of Metabolism with Fluctuation Theorems and Maximum Entropy
Cannon, William; Thomas, Dennis; Baxter, Douglas; Zucker, Jeremy; Goh, Garrett
The laws of thermodynamics dictate the behavior of biotic and abiotic systems. Simulation methods based on statistical thermodynamics can provide a fundamental understanding of how biological systems function and are coupled to their environment. While mass action kinetic simulations are based on solving ordinary differential equations using rate parameters, analogous thermodynamic simulations of mass action dynamics are based on modeling states using chemical potentials. The latter have the advantage that standard free energies of formation/reaction and metabolite levels are much easier to determine than rate parameters, allowing one to model across a large range of scales. Bridging theory and experiment, statistical thermodynamics simulations allow us to both predict activities of metabolites and enzymes and use experimental measurements of metabolites and proteins as input data. Even if metabolite levels are not available experimentally, it is shown that a maximum entropy assumption is quite reasonable and in many cases results in both the most energetically efficient process and the highest material flux.
Man, E. A.; Sera, D.; Mathe, L.; Schaltz, E.; Rosendahl, L.
2016-03-01
Characterization of thermoelectric generators (TEG) is widely discussed and equipment has been built that can perform such analysis. One method is often used to perform such characterization: constant temperature with variable thermal power input. Maximum power point tracking (MPPT) methods for TEG systems are mostly tested under steady-state conditions for different constant input temperatures. However, for most TEG applications, the input temperature gradient changes, exposing the MPPT to variable tracking conditions. An example is the exhaust pipe on hybrid vehicles, for which, because of the intermittent operation of the internal combustion engine, the TEG and its MPPT controller are exposed to a cyclic temperature profile. Furthermore, there are no guidelines on how fast the MPPT must be under such dynamic conditions. In the work discussed in this paper, temperature gradients for TEG integrated in several applications were evaluated; the results showed temperature variation up to 5°C/s for TEG systems. Electrical characterization of a calcium-manganese oxide TEG was performed at steady-state for different input temperatures and a maximum temperature of 401°C. By using electrical data from characterization of the oxide module, a solar array simulator was emulated to perform as a TEG. A trapezoidal temperature profile with different gradients was used on the TEG simulator to evaluate the dynamic MPPT efficiency. It is known that the perturb and observe (P&O) algorithm may have difficulty accurately tracking under rapidly changing conditions. To solve this problem, a compromise must be found between the magnitude of the increment and the sampling frequency of the control algorithm. The standard P&O performance was evaluated experimentally by using different temperature gradients for different MPPT sampling frequencies, and efficiency values are provided for all cases. The results showed that a tracking speed of 2.5 Hz can be successfully implemented on a TEG
Maximum entropy reconstructions of dynamic signaling networks from quantitative proteomics data.
Locasale, Jason W; Wolf-Yadlin, Alejandro
2009-08-26
Advances in mass spectrometry among other technologies have allowed for quantitative, reproducible, proteome-wide measurements of levels of phosphorylation as signals propagate through complex networks in response to external stimuli under different conditions. However, computational approaches to infer elements of the signaling network strictly from the quantitative aspects of proteomics data are not well established. We considered a method using the principle of maximum entropy to infer a network of interacting phosphotyrosine sites from pairwise correlations in a mass spectrometry data set and derive a phosphorylation-dependent interaction network solely from quantitative proteomics data. We first investigated the applicability of this approach by using a simulation of a model biochemical signaling network whose dynamics are governed by a large set of coupled differential equations. We found that in a simulated signaling system, the method detects interactions with significant accuracy. We then analyzed a growth factor mediated signaling network in a human mammary epithelial cell line that we inferred from mass spectrometry data and observe a biologically interpretable, small-world structure of signaling nodes, as well as a catalog of predictions regarding the interactions among previously uncharacterized phosphotyrosine sites. For example, the calculation places a recently identified tumor suppressor pathway through ARHGEF7 and Scribble, in the context of growth factor signaling. Our findings suggest that maximum entropy derived network models are an important tool for interpreting quantitative proteomics data.
Oxygen Escape from Venus During High Dynamic Pressure ICMEs
McEnulty, Tess; Luhmann, J. G.; Brain, D. A.; Fedorov, A.; Jian, L. K.; Russell, C. T.; Zhang, T.; Möstl, C.; Futaana, Y.; de Pater, I.
2013-10-01
Previous studies using data from Pioneer Venus suggested that oxygen ion escape flux may be enhanced by orders of magnitude during Interplanetary Coronal Mass Ejections. However, this large enhancement has been ambiguous in Venus Express ion data - with some analyses showing no flux enhancement or a small enhancement (within 2 times undisturbed cases). One possible explanation is that high escape flux may be due to high dynamic pressure in the solar wind, and the dynamic pressure has been lower during the VEX time period. So, we focus on ICMEs with the largest dynamic pressure and with VEX sampling of the escaping ions during the sheath of the ICMEs (during which the highest dynamic pressures in the solar wind occur). We will show the characteristics of these large events measured by VEX, and compare them to the largest ICMEs measured by PVO. We will then discuss estimates of the oxygen ion escape flux during these events.
Dynamic surface pressure measurements on a square cylinder with pressure sensitive paint
McGraw, C.M.; Khalil, G.; Callis, J.B. [University of Washington, Department of Chemistry, Seattle, WA (United States); Bell, J.H. [Ames Research Center, National Aeronautics and Space Administration, Moffett Field, CA (United States)
2006-02-01
The dynamic and static surface pressure on a square cylinder during vortex shedding was measured with pressure sensitive paints (PSPs) at three angles of incidence and a Reynolds number of 8.9 x 10{sup 4}. Oscillations in the phosphorescence intensity of the PSP that occurred at the vortex shedding frequency were observed. From these phosphorescent oscillations, the time-dependent changes in pressure distribution were calculated. This work extends PSP's useful range to dynamic systems where oscillating pressure changes are on the order of 230 Pa and occur at frequencies in the range of 95-125 Hz. (orig.)
A Maximum a Posteriori Estimation Framework for Robust High Dynamic Range Video Synthesis.
Li, Yuelong; Lee, Chul; Monga, Vishal
2017-03-01
High dynamic range (HDR) image synthesis from multiple low dynamic range exposures continues to be actively researched. The extension to HDR video synthesis is a topic of significant current interest due to potential cost benefits. For HDR video, a stiff practical challenge presents itself in the form of accurate correspondence estimation of objects between video frames. In particular, loss of data resulting from poor exposures and varying intensity makes conventional optical flow methods highly inaccurate. We avoid exact correspondence estimation by proposing a statistical approach via maximum a posterior estimation, and under appropriate statistical assumptions and choice of priors and models, we reduce it to an optimization problem of solving for the foreground and background of the target frame. We obtain the background through rank minimization and estimate the foreground via a novel multiscale adaptive kernel regression technique, which implicitly captures local structure and temporal motion by solving an unconstrained optimization problem. Extensive experimental results on both real and synthetic data sets demonstrate that our algorithm is more capable of delivering high-quality HDR videos than current state-of-the-art methods, under both subjective and objective assessments. Furthermore, a thorough complexity analysis reveals that our algorithm achieves better complexity-performance tradeoff than conventional methods.
Jiang Zhu
2014-01-01
Full Text Available Some delta-nabla type maximum principles for second-order dynamic equations on time scales are proved. By using these maximum principles, the uniqueness theorems of the solutions, the approximation theorems of the solutions, the existence theorem, and construction techniques of the lower and upper solutions for second-order linear and nonlinear initial value problems and boundary value problems on time scales are proved, the oscillation of second-order mixed delat-nabla differential equations is discussed and, some maximum principles for second order mixed forward and backward difference dynamic system are proved.
Noncontact Monitoring of Respiration by Dynamic Air-Pressure Sensor.
Takarada, Tohru; Asada, Tetsunosuke; Sumi, Yoshihisa; Higuchi, Yoshinori
2015-01-01
We have previously reported that a dynamic air-pressure sensor system allows respiratory status to be visually monitored for patients in minimally clothed condition. The dynamic air-pressure sensor measures vital information using changes in air pressure. To utilize this device in the field, we must clarify the influence of clothing conditions on measurement. The present study evaluated use of the dynamic air-pressure sensor system as a respiratory monitor that can reliably detect change in breathing patterns irrespective of clothing. Twelve healthy volunteers reclined on a dental chair positioned horizontally with the sensor pad for measuring air-pressure signals corresponding to respiration placed on the seat back of the dental chair in the central lumbar region. Respiratory measurements were taken under 2 conditions: (a) thinly clothed (subject lying directly on the sensor pad); and (b) thickly clothed (subject lying on the sensor pad covered with a pressure-reducing sheet). Air-pressure signals were recorded and time integration values for air pressure during each expiration were calculated. This information was compared with expiratory tidal volume measured simultaneously by a respirometer connected to the subject via face mask. The dynamic air-pressure sensor was able to receive the signal corresponding to respiration regardless of clothing conditions. A strong correlation was identified between expiratory tidal volume and time integration values for air pressure during each expiration for all subjects under both clothing conditions (0.840-0.988 for the thinly clothed condition and 0.867-0.992 for the thickly clothed condition). These results show that the dynamic air-pressure sensor is useful for monitoring respiratory physiology irrespective of clothing.
Polyunsaturation in lipid membranes: dynamic properties and lateral pressure profiles.
Ollila, Samuli; Hyvönen, Marja T; Vattulainen, Ilpo
2007-03-29
We elucidate the influence of unsaturation on single-component membrane properties, focusing on their dynamical aspects and lateral pressure profiles across the membrane. To this end, we employ atomistic molecular dynamics simulations to study five different membrane systems with varying degrees of unsaturation, starting from saturated membranes and systematically increasing the level of unsaturation, ending up with a bilayer of phospholipids containing the docosahexaenoic acid. For an increasing level of unsaturation, we find considerable effects on dynamical properties, such as accelerated dynamics of the phosphocholine head groups and glycerol backbones and speeded up rotational dynamics of the lipid molecules. The lateral pressure profile is found to be altered by the degree of unsaturation. For an increasing number of double bonds, the peak in the middle of the bilayer decreases. This is compensated for by changes in the membrane-water interface region in terms of increasing peak heights of the lateral pressure profile. Implications of the findings are briefly discussed.
Dynamic interface pressure distributions of two transtibial prosthetic socket concepts.
Dumbleton, Tim; Buis, Arjan W P; McFadyen, Angus; McHugh, Brendan F; McKay, Geoff; Murray, Kevin D; Sexton, Sandra
2009-01-01
In this study, we investigated and compared the dynamic interface pressure distribution of hands-off and hands-on transtibial prosthetic systems by means of pressure mapping. Of the 48 established unilateral amputees recruited, half (n = 24) had been wearing pressure-cast prostheses (IceCast Compact) and the other half (n = 24) had been wearing hand-cast sockets of the patellar tendon bearing design. We measured the dynamic pressure profile of more than 90% of the area within each prosthetic socket by means of four Tekscan F-Scan socket transducer arrays. We compared the interface pressure between socket concepts. We found that the distribution of dynamic pressure at the limb-socket interface was similar for the two intervention (socket prescription) groups. However, a significant difference was found in the magnitude of the interface pressure between the two socket concepts; the interface pressures recorded in the hands-off sockets were higher than those seen in the hands-on concept. Despite the differences in interface pressure, the level of satisfaction with the sockets was similar between subject groups. The sockets instrumented for this study had been in daily use for at least 6 months, with no residual-limb health problems.
Air Entrainment in Dynamic Wetting: Knudsen Effects and the Influence of Ambient Air Pressure
Sprittles, James E
2015-01-01
Recent experiments on coating flows and liquid drop impact both demonstrate that wetting failures caused by air entrainment can be suppressed by reducing the ambient gas pressure. Here, it is shown that non-equilibrium effects in the gas can account for this behaviour, with ambient pressure reductions increasing the gas' mean free path and hence the Knudsen number $Kn$. These effects first manifest themselves through Maxwell slip at the gas' boundaries so that for sufficiently small $Kn$ they can be incorporated into a continuum model for dynamic wetting flows. The resulting mathematical model contains flow structures on the nano-, micro- and milli-metre scales and is implemented into a computational platform developed specifically for such multiscale phenomena. The coating flow geometry is used to show that for a fixed gas-liquid-solid system (a) the increased Maxwell slip at reduced pressures can substantially delay air entrainment, i.e. increase the `maximum speed of wetting', (b) unbounded maximum speeds ...
Dynamics of inner ear pressure change caused by intracranial pressure manipulation in the guinea pig
Thalen, EO; Wit, HP; Segenhout, JM; Albers, FWJ
2001-01-01
Previous studies have shown that pressure changes in the cerebrospinal fluid compartment are transmitted to the inner ear. The main route for pressure transfer is the cochlear aqueduct, about which little is known with regard to its dynamic properties. In the present study, sudden intracranial press
Dynamics of inner ear pressure change caused by intracranial pressure manipulation in the guinea pig
Thalen, EO; Wit, HP; Segenhout, JM; Albers, FWJ
Previous studies have shown that pressure changes in the cerebrospinal fluid compartment are transmitted to the inner ear. The main route for pressure transfer is the cochlear aqueduct, about which little is known with regard to its dynamic properties. In the present study, sudden intracranial
Osmosis-based pressure generation: dynamics and application.
Bruhn, Brandon R; Schroeder, Thomas B H; Li, Suyi; Billeh, Yazan N; Wang, K W; Mayer, Michael
2014-01-01
This paper describes osmotically-driven pressure generation in a membrane-bound compartment while taking into account volume expansion, solute dilution, surface area to volume ratio, membrane hydraulic permeability, and changes in osmotic gradient, bulk modulus, and degree of membrane fouling. The emphasis lies on the dynamics of pressure generation; these dynamics have not previously been described in detail. Experimental results are compared to and supported by numerical simulations, which we make accessible as an open source tool. This approach reveals unintuitive results about the quantitative dependence of the speed of pressure generation on the relevant and interdependent parameters that will be encountered in most osmotically-driven pressure generators. For instance, restricting the volume expansion of a compartment allows it to generate its first 5 kPa of pressure seven times faster than without a restraint. In addition, this dynamics study shows that plants are near-ideal osmotic pressure generators, as they are composed of many small compartments with large surface area to volume ratios and strong cell wall reinforcements. Finally, we demonstrate two applications of an osmosis-based pressure generator: actuation of a soft robot and continuous volume delivery over long periods of time. Both applications do not need an external power source but rather take advantage of the energy released upon watering the pressure generators.
Osmosis-based pressure generation: dynamics and application.
Brandon R Bruhn
Full Text Available This paper describes osmotically-driven pressure generation in a membrane-bound compartment while taking into account volume expansion, solute dilution, surface area to volume ratio, membrane hydraulic permeability, and changes in osmotic gradient, bulk modulus, and degree of membrane fouling. The emphasis lies on the dynamics of pressure generation; these dynamics have not previously been described in detail. Experimental results are compared to and supported by numerical simulations, which we make accessible as an open source tool. This approach reveals unintuitive results about the quantitative dependence of the speed of pressure generation on the relevant and interdependent parameters that will be encountered in most osmotically-driven pressure generators. For instance, restricting the volume expansion of a compartment allows it to generate its first 5 kPa of pressure seven times faster than without a restraint. In addition, this dynamics study shows that plants are near-ideal osmotic pressure generators, as they are composed of many small compartments with large surface area to volume ratios and strong cell wall reinforcements. Finally, we demonstrate two applications of an osmosis-based pressure generator: actuation of a soft robot and continuous volume delivery over long periods of time. Both applications do not need an external power source but rather take advantage of the energy released upon watering the pressure generators.
Prediction of Dynamic Wellbore Pressure in Gasified Fluid Drilling
Wang Zhiming; Ping Liqiu; Zou Ke
2007-01-01
The basis of designing gasified drilling is to understand the behavior of gas/liquid two-phase flow in the wellbore. The equations of mass and momentum conservation and equation of fluid flow in porous media were used to establish a dynamic model to predict weIlbore pressure according to the study results of Ansari and Beggs-Brill on gas-liquid two-phase flow. The dynamic model was solved by the finite difference approach combined with the mechanistic steady state model. The mechanistic dynamic model was numerically implemented into a FORTRAN 90 computer program and could simulate the coupled flow of fluid in wellbore and reservoir. The dynamic model revealed the effects of wellhead back pressure and injection rate of gas/liquid on bottomhole pressure. The model was validated against full-scale experimental data, and its 5.0% of average relative error could satisfy the accuracy requirements in engineering design.
High-pressure dynamics of hydrated protein in bioprotective trehalose environment
Diallo, S. O.; Zhang, Q.; O'Neill, H.; Mamontov, E.
2014-10-01
We present a pressure-dependence study of the dynamics of lysozyme protein powder immersed in deuterated α ,α -trehalose environment via quasielastic neutron scattering (QENS). The goal is to assess the baroprotective benefits of trehalose on biomolecules by comparing the findings with those of a trehalose-free reference study. While the mean-square displacement of the trehalose-free protein (hydrated to dD2O≃ 40 w%) as a whole, is reduced by increasing pressure, the actual observable relaxation dynamics in the picoseconds to nanoseconds time range remains largely unaffected by pressure—up to the maximum investigated pressure of 2.78(2) Kbar. Our observation is independent of whether or not the protein is mixed with the deuterated sugar. This suggests that the hydrated protein's conformational states at atmospheric pressure remain unaltered by hydrostatic pressures, below 2.78 Kbar. We also found the QENS response to be totally recoverable after ambient pressure conditions are restored. Small-angle neutron diffraction measurements confirm that the protein-protein correlation remains undisturbed. We observe, however, a clear narrowing of the QENS response as the temperature is decreased from 290 to 230 K in both cases, which we parametrize using the Kohlrausch-Williams-Watts stretched exponential model. Only the fraction of protons that are immobile on the accessible time window of the instrument, referred to as the elastic incoherent structure factor, is observably sensitive to pressure, increasing only marginally but systematically with increasing pressure.
Population Dynamics Following the Last Glacial Maximum in Two Sympatric Lizards in Northern China
Yanfu QU; Qun ZHAO; Hongliang LU; Xiang JI
2014-01-01
Phylogeographic studies ofEremias lizards (Lacertidae) in East Asia have been limited, and the impact of major climatic events on their population dynamics remains poorly known. This study aimed to investigate population histories and refugia during the Last Glacial Maximum of two sympatricEremias lizards (E. argus andE. brenchleyi) inhabiting northern China. We sequenced partial mitochondrial DNA from theND4 gene for 128 individuals ofE. argus from nine localities, and 46 individuals ofE. brenchleyi from ifve localities. Forty-fourND4 haplotypes were determined fromE. argus samples, and 33 fromE. brenchleyi samples. Population expansion events began about 0.0044 Ma inE. argus, and 0.031 Ma inE. brenchleyi. The demographic history ofE. brenchleyi indicates a long-lasting population decline since the most recent common ancestor, while that ofE. argusindicates a continuous population growth. Among-population structure was signiifcant in both species, and there were multiple refugia across their range. Intermittent gene flow occurred among expanded populations across multiple refugia during warmer phases of the glacial period, and this may explain why the effective population size has remained relatively stable inE. brenchleyi and grown inE. argus.
Maximum-Likelihood Adaptive Filter for Partially Observed Boolean Dynamical Systems
Imani, Mahdi; Braga-Neto, Ulisses M.
2017-01-01
Partially-observed Boolean dynamical systems (POBDS) are a general class of nonlinear models with application in estimation and control of Boolean processes based on noisy and incomplete measurements. The optimal minimum mean square error (MMSE) algorithms for POBDS state estimation, namely, the Boolean Kalman filter (BKF) and Boolean Kalman smoother (BKS), are intractable in the case of large systems, due to computational and memory requirements. To address this, we propose approximate MMSE filtering and smoothing algorithms based on the auxiliary particle filter (APF) method from sequential Monte-Carlo theory. These algorithms are used jointly with maximum-likelihood (ML) methods for simultaneous state and parameter estimation in POBDS models. In the presence of continuous parameters, ML estimation is performed using the expectation-maximization (EM) algorithm; we develop for this purpose a special smoother which reduces the computational complexity of the EM algorithm. The resulting particle-based adaptive filter is applied to a POBDS model of Boolean gene regulatory networks observed through noisy RNA-Seq time series data, and performance is assessed through a series of numerical experiments using the well-known cell cycle gene regulatory model.
Analysis of dynamic foot pressure distribution and ground reaction forces
Ong, F. R.; Wong, T. S.
2005-04-01
The purpose of this study was to assess the relationship between forces derived from in-shoe pressure distribution and GRFs during normal gait. The relationship served to demonstrate the accuracy and reliability of the in-shoe pressure sensor. The in-shoe pressure distribution from Tekscan F-Scan system outputs vertical forces and Centre of Force (COF), while the Kistler force plate gives ground reaction forces (GRFs) in terms of Fz, Fx and Fy, as well as vertical torque, Tz. The two systems were synchronized for pressure and GRFs measurements. Data was collected from four volunteers through three trials for both left and right foot under barefoot condition with the in-shoe sensor. The forces derived from pressure distribution correlated well with the vertical GRFs, and the correlation coefficient (r2) was in the range of 0.93 to 0.99. This is a result of extended calibration, which improves pressure measurement to give better accuracy and reliability. The COF from in-shoe sensor generally matched well with the force plate COP. As for the maximum vertical torque at the forefoot during toe-off, there was no relationship with the pressure distribution. However, the maximum torque was shown to give an indication of the rotational angle of the foot.
Nayak, Chitresh; Singh, Amit; Chaudhary, Himanshu; Unune, Deepak Rajendra
2017-08-01
Technological advances in prosthetics have attracted the curiosity of researchers in monitoring design and developments of the sockets to sustain maximum pressure without any soft tissue damage, skin breakdown, and painful sores. Numerous studies have been reported in the area of pressure measurement at the limb/socket interface, though, the relation between amputee's physiological parameters and the pressure developed at the limb/socket interface is still not studied. Therefore, the purpose of this work is to investigate the effects of patient-specific physiological parameters viz. height, weight, and stump length on the pressure development at the transtibial prosthetic limb/socket interface. Initially, the pressure values at the limb/socket interface were clinically measured during stance and walking conditions for different patients using strain gauges placed at critical locations of the stump. The measured maximum pressure data related to patient's physiological parameters was used to develop an artificial neural network (ANN) model. The effects of physiological parameters on the pressure development at the limb/socket interface were examined using the ANN model. The analyzed results indicated that the weight and stump length significantly affects the maximum pressure values. The outcomes of this work could be an important platform for the design and development of patient-specific prosthetic socket which can endure the maximum pressure conditions at stance and ambulation conditions.
Pressure Dynamic Characteristics of Pressure Controlled Ventilation System of a Lung Simulator
Yan Shi
2014-01-01
Full Text Available Mechanical ventilation is an important life support treatment of critically ill patients, and air pressure dynamics of human lung affect ventilation treatment effects. In this paper, in order to obtain the influences of seven key parameters of mechanical ventilation system on the pressure dynamics of human lung, firstly, mechanical ventilation system was considered as a pure pneumatic system, and then its mathematical model was set up. Furthermore, to verify the mathematical model, a prototype mechanical ventilation system of a lung simulator was proposed for experimental study. Last, simulation and experimental studies on the air flow dynamic of the mechanical ventilation system were done, and then the pressure dynamic characteristics of the mechanical system were obtained. The study can be referred to in the pulmonary diagnostics, treatment, and design of various medical devices or diagnostic systems.
Dynamic tire pressure sensor for measuring ground vibration.
Wang, Qi; McDaniel, James Gregory; Wang, Ming L
2012-11-07
This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application.
R. O'ishi
2013-07-01
Full Text Available When the climate is reconstructed from paleoevidence, it shows that the Last Glacial Maximum (LGM, ca. 21 000 yr ago is cold and dry compared to the present-day. Reconstruction also shows that compared to today, the vegetation of the LGM is less active and the distribution of vegetation was drastically different, due to cold temperature, dryness, and a lower level of atmospheric CO2 concentration (185 ppm compared to a preindustrial level of 285 ppm. In the present paper, we investigate the influence of vegetation change on the climate of the LGM by using a coupled atmosphere-ocean-vegetation general circulation model (AOVGCM, the MIROC-LPJ. The MIROC-LPJ is different from earlier studies in the introduction of a bias correction method in individual running GCM experiments. We examined four GCM experiments (LGM and preindustrial, with and without vegetation feedback and quantified the strength of the vegetation feedback during the LGM. The result shows that global-averaged cooling during the LGM is amplified by +13.5 % due to the introduction of vegetation feedback. This is mainly caused by the increase of land surface albedo due to the expansion of tundra in northern high latitudes and the desertification in northern middle latitudes around 30° N to 60° N. We also investigated how this change in climate affected the total terrestrial carbon storage by using offline Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM. Our result shows that the total terrestrial carbon storage was reduced by 597 PgC during the LGM, which corresponds to the emission of 282 ppm atmospheric CO2. In the LGM experiments, the global carbon distribution is generally the same whether the vegetation feedback to the atmosphere is included or not. However, the inclusion of vegetation feedback causes substantial terrestrial carbon storage change, especially in explaining the lowering of atmospheric CO2 during the LGM.
R. O'ishi
2012-11-01
Full Text Available When the climate is reconstructed from paleoevidence, it shows that the Last Glacial Maximum (LGM, ca. 21 000 yr ago is cold and dry compared to the present day. Reconstruction also shows that compared to today, the vegetation of the LGM is less active and the distribution of vegetation was drastically different, due to cold temperature, dryness, and a lower level of atmospheric CO_{2} level (185 ppm compared to a preindustrial level of 285 ppm. In the present paper, we investigate the influence of vegetation change on the climate of the LGM by using a coupled atmosphere-ocean-vegetation general circulation model (GCM, the MIROC-LPJ. We examined four GCM experiments (LGM and preindustrial, with and without vegetation feedback and quantified the strength of the vegetation feedback during the LGM. The result shows global-averaged cooling during the LGM is amplified by +13.5% due to the introduction of vegetation feedback. This is mainly caused by the increase of land surface albedo due to the expansion of tundra in northern high latitudes and the desertification in northern middle latitudes around 30° N to 60° N. We also investigated how this change in climate affected the total terrestrial carbon storage by using a separated Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM. Our result shows that the total terrestrial carbon storage was reduced by 653 PgC during the LGM, which corresponds to the emission of 308 ppm atmospheric CO_{2}. The carbon distribution during the LGM that is predicted from using an atmospheric-ocean-vegetation (AOV GCM and using the LPJ-DGVM after an atmospheric-ocean (AO GCM, is generally the same, but the difference is not negligible for explaining the lowering of atmospheric CO_{2} during the LGM.
Optic Fiber-Based Dynamic Pressure Sensor
Jiu-Lin Gan; Hai-Wen Cai; Jian-Xin Geng; Zheng-Qing Pan; Rong-Hui Qu; Zu-Jie Fang
2008-01-01
Weigh-in-Motion(WIM) technique is the process of measuring the dynamic tire forces of a moving vehicle and estimating the corresponding tire loads of the static vehicle. Compared with the static weigh station, WIM station is an efficient and cost effective choice that will minimize unneccessary stops and delay for truckers. The way to turn birefringence of single-mode fiber into a prime quality for a powerful and reliable sensor is shown. Preliminary results for the development of a weigh-in-motion (WIM) technique based on sagnac-loop sensor are presented. After a brief description of the sensor and its principle of operation, the theoretical model is developed. Then, a full characterization made in static conditions is presented.
Finger and Palm Dynamic Pressure Monitoring for Basketball Shooting
Chiao-Fang Hung
2017-01-01
Full Text Available This study verified general inferences on the finger and palm pressure distribution of a basketball player in the moment before that player shoots a basketball through a scientific qualitative testing method. We mounted the sensor on the hands of college basketball players and monitored the dynamic pressure of each player’s hand while the player threw a basketball. The dynamic pressure distribution of the fingers and palm of a basketball player throwing a ball can be verified. According to the experimental results, college basketball players typically use the index finger to control the direction and power of force in the moment before shooting a basketball. This study successfully used a scientific qualitative test method to monitor the dynamic pressure of the fingers and palms of basketball players and verified the general inference that a typical basketball player mainly uses the index finger to control the direction and power of force in the moment before throwing a ball. In the future, this study, measuring the dynamic pressure distribution of the fingers and palm, can be applied to simulate hand manipulation in many biomedical and robotic applications.
Modeling the pressure inactivation dynamics of Escherichia coli
Yamamoto K.
2005-01-01
Full Text Available Escherichia coli, as a model microorganism, was treated in phosphate-buffered saline under high hydrostatic pressure between 100 and 300 MPa, and the inactivation dynamics was investigated from the viewpoint of predictive microbiology. Inactivation data were curve fitted by typical predictive models: logistic, Gompertz and Weibull functions. Weibull function described the inactivation curve the best. Two parameters of Weibull function were calculated for each holding pressure and their dependence on holding pressure was obtained by interpolation. With the interpolated parameters, inactivation curves were simulated and compared with the experimental data sets.
A Direct Two-Dimensional Pressure Formulation in Molecular Dynamics
YD, Sumith
2016-01-01
Two-dimensional (2D) pressure field estimation in molecular dynamics (MD) simulations has been done using three-dimensional (3D) pressure field calculations followed by averaging, which is computationally expensive due to 3D convolutions. In this work, we develop a direct 2D pressure field estimation method which is much faster than 3D methods without losing accuracy. The method is validated with MD simulations on two systems: a liquid film and a cylindrical drop of argon suspended in surrounding vapor.
Molecular dynamics study of helium bubble pressure in titanium
Zhang Bao-Ling; Wang Jun; Hou Qing
2011-01-01
In this paper, the pressure state of the helium bubble in titanium is simulated by a molecular dynamics (MD) method. First, the possible helium/vacancy ratio is determined according to therelation between the bubble pressure and helium/vacancy ratio; then the dependences of the helium bubble pressure on the bubble radius at different temperatures are studied. It is shown that the product of the bubble pressure and the radius is approximately a constant, a result justifying the pressure-radius relation predicted by thermodynamics-based theory for gas bubble. Furthermore, a state equation of the helium bubble is established based on the MD calculations. Comparison between the results obtained by the state equation and corresponding experimental data shows that the state equation can describe reasonably the state of helium bubble and thus could be used for Monte Carlo simulations of the evolution of helium bubble in metals.
Irrigation dynamic pressure-assisted hydrodissection during cataract surgery
Masuda Y
2017-02-01
Full Text Available Yoichiro Masuda,1 Hisaharu Iwaki,2 Noriko Kato,1 Genichiro Takahashi,1 Kotaro Oki,3 Hiroshi Tsuneoka4 1Department of Ophthalmology, The Jikei University, Katsushika Medical Center, 2Iwaki Eye Clinic, 3Oki Eye Surgery Center, 4Department of Ophthalmology, The Jikei University, School of Medicine, Tokyo, Japan Abstract: The irrigation dynamic pressure-assisted hydrodissection technique (irrigation-hydro [iH] does not require performing manual hydrodissection using a syringe and cannula to achieve cortical-capsular cleavage during cataract surgery. Since the iH technique uses the phaco tip to intentionally vacuum the intraocular fluid in order to induce the irrigation dynamic pressure for cortical-capsular cleavage, there is a reduction in the intraocular pressure (IOP from the bottle-height-dependent hydrostatic pressure. Thus, since the peak irrigation pressure derived from the phaco tip sleeve will be limited by the height of the irrigation fluid bottle, this is advantageous in helping to avoid excessively high IOP during cortical-capsular hydrodissection. Using this technique, we were able to effectively perform phacoemulsification without complications in 607 of 609 cataract eyes. Our findings show that utilization of the iH technique would be of benefit to patients, as it prevents high-pressure hydrodissection-related complications, such as capsular block syndrome and tears in the anterior hyaloid membrane during cataract surgery. Keywords: cataract surgery, hydrodissection, irrigation pressure, hydrodissection-related complication, capsular block syndrome, anterior hyaloid membrane tear, FLACS
Water dynamics and retrogradation of ultrahigh pressurized wheat starch.
Doona, Christopher J; Feeherry, Florence E; Baik, Moo-Yeol
2006-09-06
The water dynamics and retrogradation kinetics behavior of gelatinized wheat starch by either ultrahigh pressure (UHP) processing or heat are investigated. Wheat starch completely gelatinized in the condition of 90, 000 psi at 25 degrees C for 30 min (pressurized gel) or 100 degrees C for 30 min (heated gel). The physical properties of the wheat starches were characterized in terms of proton relaxation times (T2 times) measured using time-domain nuclear magnetic resonance spectroscopy and evaluated using commercially available continuous distribution modeling software. Different T2 distributions in both micro- and millisecond ranges between pressurized and heated wheat starch gels suggest distinctively different water dynamics between pressurized and heated wheat starch gels. Smaller water self-diffusion coefficients were observed for pressurized wheat starch gels and are indicative of more restricted translational proton mobility than is observed with heated wheat starch gels. The physical characteristics associated with changes taking place during retrogradation were evaluated using melting curves obtained with differential scanning calorimetry. Less retrogradation was observed in pressurized wheat starch, and it may be related to a smaller quantity of freezable water in pressurized wheat starch. Starches comprise a major constituent of many foods proposed for commercial potential using UHP, and the present results furnish insight into the effect of UHP on starch gelatinization and the mechanism of retrogradation during storage.
Flantua, S.G.A.; Hooghiemstra, H.; van Boxel, J.H.; Cabrera, M.; González-Carranza, Z.; González-Arango, C.; Stevens, W.D.; Montiel, O.M.; Raven, P.H.
2014-01-01
We provide an innovative pollen-driven connectivity framework of the dynamic altitudinal distribution of North Andean biomes since the Last Glacial Maximum (LGM). Altitudinally changing biome distributions reconstructed from a pollen record from Lake La Cocha (2780 m) are assessed in terms of their
Cavalli, Andrea; Camilloni, Carlo; Vendruscolo, Michele
2013-03-07
In order to characterise the dynamics of proteins, a well-established method is to incorporate experimental parameters as replica-averaged structural restraints into molecular dynamics simulations. Here, we justify this approach in the case of interproton distance information provided by nuclear Overhauser effects by showing that it generates ensembles of conformations according to the maximum entropy principle. These results indicate that the use of replica-averaged structural restraints in molecular dynamics simulations, given a force field and a set of experimental data, can provide an accurate approximation of the unknown Boltzmann distribution of a system.
Lateral Pressure of RC Silos with Static and Dynamic Granular Materials
Lingkai Meng
2015-01-01
This paper aims at analyzing material⁃induced lateral pressure of RC cylinder silo in both static and dynamic condition using the finite element method (FEM).In the finite element software ABAQUS, concrete material is modeled by concrete damaged plasticity model, and stored materials in silo is modeled by the hypoplastic theory.In terms of numerical model, shell elements (S4R) and solid elements (C3D8) are applied for model silo wall and stored materials respectively. The interaction between silo wall and stored materials is simulated by Coulomb friction model and penalty contact constrain provided by ABAQUS.The numerical results are verified with the existing experimental data that are designed to ensure the validation of such numerical model using FEM and it obtains good agreements between numerical results and experimental data. Then the material parameters are analyzed in both static and dynamic condition.According to the analysis, it is clear that critical friction angle, initial void ratio and minimum void ratio have an obvious effect on static lateral pressure while all the material parameters affect dynamic lateral pressure at different levels. In addition, differences of silo wall between elastic and plastic state are analyzed in dynamic condition. The numerical results show that it contributes to increasing dynamic pressure when silo wall enters into the plastic state. Finally, this paper discusses the time⁃history lateral pressure at different heights along silo wall, and analytical results indicate that larger acceleration values play main roles in producing the maximum lateral pressure at higher part of the silo wall.
Two methods for absolute calibration of dynamic pressure transducers
Swift, G. W.; Migliori, A.; Garrett, S. L.; Wheatley, J. C.
1982-12-01
Two techniques are described for absolute calibration of a dynamic pressure transducer from 0 to 400 Hz in 1-MPa helium gas. One technique is based on a comparison to a mercury manometer; the other is based on the principle of reciprocity. The two techniques agree within the instrumental uncertainties of 1%.
Dynamic Mode Decomposition of Fast Pressure Sensitive Paint Data
Mohd Y. Ali
2016-06-01
Full Text Available Fast-response pressure sensitive paint (PSP is used in this work to measure and analyze the acoustic pressure field in a rectangular cavity. The high spatial resolution and fast frequency response of PSP effectively captures the spatial and temporal detail of surface pressure resulting in the acoustic pressure field. In this work, a high-speed camera is used to generate a continuous time record of the acoustic pressure fluctuations with PSP. Since the level of the acoustic pressure is near the resolution limit of the sensor system, advanced analysis techniques are used to extract the spatial modes of the pressure field. Both dynamic mode decomposition (DMD and proper orthogonal decomposition (POD are compared with phase averaging for data analysis. While all three techniques effectively extract the pressure field and reduce the impact of sensor noise, DMD and POD are more robust techniques that can be applied to aperiodic or multi-frequency signals. Furthermore, DMD is better than POD at suppressing noise in particular regions of the spectrum and at effectively separating spectral energy when multiple acoustic excitation frequencies are present.
Richtmyer-Meshkov unstable dynamics influenced by pressure fluctuations
Bhowmick, A. K.; Abarzhi, S. I.
2016-11-01
We theoretically study the effect of pressure fluctuations on the Richtmyer-Meshkov (RM) unstable interface in approximation of ideal incompressible immiscible fluids and two-dimensional flow. Pressure fluctuations are treated as an effective acceleration directed from the heavy to light fluid with inverse square time dependence. The group theory approach is applied to analyze large-scale coherent dynamics, solve the complete set of the governing equations, and find regular asymptotic solutions describing RM bubbles. A strong effect is found, for the first time to our knowledge, of pressure fluctuations on the interface morphology and dynamics. In the linear regime, a nearly flat bubble gets more curved, and its velocity increases for strong pressure fluctuations and decreases otherwise. In the nonlinear regime, solutions form a one-parameter family parameterized by the bubble front curvature. For the fastest stable solution in the family, the RM bubble is curved for strong pressure fluctuations and is flattened otherwise. The flow is characterized by the intense motion of the fluids in the vicinity of the interface, effectively no motion away from the interface, and presence of shear at the interface leading to formation of smaller scale vortical structures. Our theoretical results agree with and explain existing experiments and simulations and identify new qualitative and quantitative characteristics to evaluate the strength of pressure fluctuations in experiments and simulations.
Tyre pressure monitoring using a dynamical model-based estimator
Reina, Giulio; Gentile, Angelo; Messina, Arcangelo
2015-04-01
In the last few years, various control systems have been investigated in the automotive field with the aim of increasing the level of safety and stability, avoid roll-over, and customise handling characteristics. One critical issue connected with their integration is the lack of state and parameter information. As an example, vehicle handling depends to a large extent on tyre inflation pressure. When inflation pressure drops, handling and comfort performance generally deteriorate. In addition, it results in an increase in fuel consumption and in a decrease in lifetime. Therefore, it is important to keep tyres within the normal inflation pressure range. This paper introduces a model-based approach to estimate online tyre inflation pressure. First, basic vertical dynamic modelling of the vehicle is discussed. Then, a parameter estimation framework for dynamic analysis is presented. Several important vehicle parameters including tyre inflation pressure can be estimated using the estimated states. This method aims to work during normal driving using information from standard sensors only. On the one hand, the driver is informed about the inflation pressure and he is warned for sudden changes. On the other hand, accurate estimation of the vehicle states is available as possible input to onboard control systems.
Computational Fluid Dynamics Analysis of High Injection Pressure Blended Biodiesel
Khalid, Amir; Jaat, Norrizam; Faisal Hushim, Mohd; Manshoor, Bukhari; Zaman, Izzuddin; Sapit, Azwan; Razali, Azahari
2017-08-01
Biodiesel have great potential for substitution with petrol fuel for the purpose of achieving clean energy production and emission reduction. Among the methods that can control the combustion properties, controlling of the fuel injection conditions is one of the successful methods. The purpose of this study is to investigate the effect of high injection pressure of biodiesel blends on spray characteristics using Computational Fluid Dynamics (CFD). Injection pressure was observed at 220 MPa, 250 MPa and 280 MPa. The ambient temperature was kept held at 1050 K and ambient pressure 8 MPa in order to simulate the effect of boost pressure or turbo charger during combustion process. Computational Fluid Dynamics were used to investigate the spray characteristics of biodiesel blends such as spray penetration length, spray angle and mixture formation of fuel-air mixing. The results shows that increases of injection pressure, wider spray angle is produced by biodiesel blends and diesel fuel. The injection pressure strongly affects the mixture formation, characteristics of fuel spray, longer spray penetration length thus promotes the fuel and air mixing.
Irrigation dynamic pressure-assisted hydrodissection during cataract surgery.
Masuda, Yoichiro; Iwaki, Hisaharu; Kato, Noriko; Takahashi, Genichiro; Oki, Kotaro; Tsuneoka, Hiroshi
2017-01-01
The irrigation dynamic pressure-assisted hydrodissection technique (irrigation-hydro [iH]) does not require performing manual hydrodissection using a syringe and cannula to achieve cortical-capsular cleavage during cataract surgery. Since the iH technique uses the phaco tip to intentionally vacuum the intraocular fluid in order to induce the irrigation dynamic pressure for cortical-capsular cleavage, there is a reduction in the intraocular pressure (IOP) from the bottle-height-dependent hydrostatic pressure. Thus, since the peak irrigation pressure derived from the phaco tip sleeve will be limited by the height of the irrigation fluid bottle, this is advantageous in helping to avoid excessively high IOP during cortical-capsular hydrodissection. Using this technique, we were able to effectively perform phacoemulsification without complications in 607 of 609 cataract eyes. Our findings show that utilization of the iH technique would be of benefit to patients, as it prevents high-pressure hydrodissection-related complications, such as capsular block syndrome and tears in the anterior hyaloid membrane during cataract surgery.
Irrigation dynamic pressure-assisted hydrodissection during cataract surgery
Masuda, Yoichiro; Iwaki, Hisaharu; Kato, Noriko; Takahashi, Genichiro; Oki, Kotaro; Tsuneoka, Hiroshi
2017-01-01
The irrigation dynamic pressure-assisted hydrodissection technique (irrigation-hydro [iH]) does not require performing manual hydrodissection using a syringe and cannula to achieve cortical-capsular cleavage during cataract surgery. Since the iH technique uses the phaco tip to intentionally vacuum the intraocular fluid in order to induce the irrigation dynamic pressure for cortical-capsular cleavage, there is a reduction in the intraocular pressure (IOP) from the bottle-height-dependent hydrostatic pressure. Thus, since the peak irrigation pressure derived from the phaco tip sleeve will be limited by the height of the irrigation fluid bottle, this is advantageous in helping to avoid excessively high IOP during cortical-capsular hydrodissection. Using this technique, we were able to effectively perform phacoemulsification without complications in 607 of 609 cataract eyes. Our findings show that utilization of the iH technique would be of benefit to patients, as it prevents high-pressure hydrodissection-related complications, such as capsular block syndrome and tears in the anterior hyaloid membrane during cataract surgery. PMID:28243054
Sahoo, B. D., E-mail: bdsahoo@barc.gov.in; Joshi, K. D.; Gupta, Satish C. [Applied Physics Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)
2015-06-24
Structural and lattice dynamical stability of the LaF3 has been analyzed as a function of hydrostatic compression through first principle electronic band structure calculations. The comparison of enthalpies of various plausible structures calculated at various pressures suggests a phase transition from ambient condition tysonite structure (space group P-3c1) to a primitive orthorhombic structure (space group Pmmn) at a pressure of ∼19.5 GPa, in line with the experimental value of 16 GPa. Further, it is predicted that this phase will remain stable up to 100 GPa (the maximum pressure up to which calculations have been performed in the present work). The theoretically determined equation of state displays a good agreement with experimental data. Various physical quantities such as zero pressure equilibrium volume, bulk modulus, and pressure derivative of bulk modulus have been derived from the theoretically determined equation of state and compared with the available experimental data. Our lattice dynamic calculations correctly demonstrate that at zero pressure the tysonite structure is lattice dynamically stable whereas the Pmmn structure is unstable lattice dynamically. Further, at transition pressure the theoretically calculated phonon spectra clearly show that the Pmmn phase emerges as lattice dynamically stable phase whereas the tysonite structure becomes unstable dynamically, supporting our static lattice calculations.
On structural and lattice dynamic stability of LaF3 under high pressure: A first principle study
Sahoo, B. D.; Joshi, K. D.; Gupta, Satish C.
2015-06-01
Structural and lattice dynamical stability of the LaF3 has been analyzed as a function of hydrostatic compression through first principle electronic band structure calculations. The comparison of enthalpies of various plausible structures calculated at various pressures suggests a phase transition from ambient condition tysonite structure (space group P-3c1) to a primitive orthorhombic structure (space group Pmmn) at a pressure of ˜19.5 GPa, in line with the experimental value of 16 GPa. Further, it is predicted that this phase will remain stable up to 100 GPa (the maximum pressure up to which calculations have been performed in the present work). The theoretically determined equation of state displays a good agreement with experimental data. Various physical quantities such as zero pressure equilibrium volume, bulk modulus, and pressure derivative of bulk modulus have been derived from the theoretically determined equation of state and compared with the available experimental data. Our lattice dynamic calculations correctly demonstrate that at zero pressure the tysonite structure is lattice dynamically stable whereas the Pmmn structure is unstable lattice dynamically. Further, at transition pressure the theoretically calculated phonon spectra clearly show that the Pmmn phase emerges as lattice dynamically stable phase whereas the tysonite structure becomes unstable dynamically, supporting our static lattice calculations.
Rezende, L. C.; Arenque, B.; von Randow, C.; Moura, M. S.; Aidar, S. D.; Buckeridge, M. S.; Menezes, R.; Souza, L. S.; Ometto, J. P.
2013-12-01
The Caatinga biome in the semi-arid region of northeastern Brazil is extremely important due to its biodiversity and endemism. This biome, which is under high anthropogenic influences, presents high levels of environmental degradation, land use being among the main causes of such degradation. The simulations of land cover and the vegetation dynamic under different climate scenarios are important features for prediction of environmental risks and determination of sustainable pathways for the planet in the future. Modeling of the vegetation can be performed by use of dynamic global vegetation models (DGVMs). The DGVMs simulate the surface processes (e.g. transfer of energy, water, CO2 and momentum); plant physiology (e.g. photosynthesis, stomatal conductance) phenology; gross and net primary productivity, respiration, plant species classified by functional traits; competition for light, water and nutrients, soil characteristics and processes (e.g. nutrients, heterotrophic respiration). Currently, most of the parameters used in DGVMs are static pre-defined values, and the lack of observational information to aid choosing the most adequate values for these parameters is particularly critical for the semi-arid regions in the world. Through historical meteorological data and measurements of carbon assimilation we aim to calibrate the maximum carboxylation velocity (Vcmax), for the native species Poincianella microphylla, abundant in the Caatinga region. The field data (collected at Lat: 90 2' S, Lon: 40019' W) displayed two contrasting meteorological conditions, with precipitations of 16 mm and 104 mm prior to the sampling campaigns (April 9-13, 2012 and February 4-8, 2013; respectively). Calibration (obtaining values of Vcmax more suitable for vegetation of Caatinga) has been performed through an algorithm of pattern recognition: Classification And Regression Tree (CART) and calculation of the vapor pressure deficit (VPD), which was used as attribute for discrimination
Dynamics of non-stationary processes that follow the maximum of the Rényi entropy principle.
Shalymov, Dmitry S; Fradkov, Alexander L
2016-01-01
We propose dynamics equations which describe the behaviour of non-stationary processes that follow the maximum Rényi entropy principle. The equations are derived on the basis of the speed-gradient principle originated in the control theory. The maximum of the Rényi entropy principle is analysed for discrete and continuous cases, and both a discrete random variable and probability density function (PDF) are used. We consider mass conservation and energy conservation constraints and demonstrate the uniqueness of the limit distribution and asymptotic convergence of the PDF for both cases. The coincidence of the limit distribution of the proposed equations with the Rényi distribution is examined.
ZHANG Hong-lie; ZHANG Guo-yin; YAO Ai-hong
2010-01-01
This paper presents an algorithm that combines the chaos optimization algorithm with the maximum entropy(COA-ME)by using entropy model based on chaos algorithm,in which the maximum entropy is used as the second method of searching the excellent solution.The search direction is improved by chaos optimization algorithm and realizes the selective acceptance of wrong solution.The experimental result shows that the presented algorithm can be used in the partitioning of hardware/software of reconfigurable system.It effectively reduces the local extremum problem,and search speed as well as performance of partitioning is improved.
Fulgueras, Alyssa Marie; Poudel, Jeeban; Kim, Dong Sun; Cho, Jungho [Kongju National University, Cheonan (Korea, Republic of)
2016-01-15
The separation of ethylenediamine (EDA) from aqueous solution is a challenging problem because its mixture forms an azeotrope. Pressure-swing distillation (PSD) as a method of separating azeotropic mixture were investigated. For a maximum-boiling azeotropic system, pressure change does not greatly affect the azeotropic composition of the system. However, the feasibility of using PSD was still analyzed through process simulation. Experimental vapor liquid equilibrium data of water-EDA system was studied to predict the suitability of thermodynamic model to be applied. This study performed an optimization of design parameters for each distillation column. Different combinations of operating pressures for the low- and high-pressure columns were used for each PSD simulation case. After the most efficient operating pressures were identified, two column configurations, low-high (LP+HP) and high-low (HP+ LP) pressure column configuration, were further compared. Heat integration was applied to PSD system to reduce low and high temperature utility consumption.
Dynamic damper pressure fluctuation in the pumping systems
O.V. Korolyov
2016-05-01
Full Text Available Inertial part of any devices and equipment (e.g., pumps, hung or mounted on the resilient frame and being under the influence of the disturbing force that works at a constant frequency, may be subject to fluctuations, especially near of the resonance area. For elimination these fluctuations, you can resort to the use of a dynamic damper. Aim: The aim of the work is an analytical study of various dynamic dampers to reduce pressure fluctuation problems in pumping systems. Materials and Methods: A comparative analysis of efficiency of functioning was carried out for two types of dynamic dampers - hydraulic and mechanical. Results: The technique for calculating of dynamic damper of fluid pressure fluctuations in the hydraulic and mechanical pumps is presented. Algorithms of calculations are reported to engineering applications and implemented in the production process. The calculations show that the use of dynamic mechanical dampers is expedient at high frequency pumps, and, with increasing frequency of the pump by 6 times, winning in the dimensions of the damper in 3.5 times.
DYNAMICAL BEHAVIOR OF VISCOELASTIC CYLINDRICAL SHELLS UNDER AXIAL PRESSURES
程昌钧; 张能辉
2001-01-01
The hypotheses of the Kármán-Donnell theory of thin shells with large deflections and the Boltzmann laws for isotropic linear, viscoelastic materials, the constitutive equations of shallow shells are first derived. Then the governing equations for the deflection equations of elastic thin plates. Introducing proper assumptions, an approximate theory for viscoelastic cylindrical shells under axial pressures can be obtained. Finally, the dynamical behavior is studied in detail by using several numerical methods. Dynamical properties,such as, hyperchaos , chaos, strange attractor, limit cycle etc., are discovered.
Pressure effects on dynamics behavior of multiwall boron nitride nanotubes
Talebian, Taha [Faculty of Engineering, Neyshabur Branch, Islamic Azad University, Neyshabur (Iran, Islamic Republic of)
2016-01-15
The dynamic behavior of Multiwall boron nitride nanotubes (MWBNNTs) is investigated by employing multiple elastic shells model. The influences of van der Waals interactions on layers are shown as nonlinear functions of the interlayer distance of MWBNNTs. Governing equations are solved by using the developed finite element method and by employing time history diagrams. The radial wave speed from the outermost layer to the innermost layer is computed. The effects of geometrical factors such as diameter-to-thickness ratio on dynamic behavior of MWBNNTs are determined. The magnification aspects of MWBNNTs are computed, and the effects of surrounding pressures on wave speed and magnification aspect of MWBNNTs are discussed.
Lee, C.-H.; Herget, C. J.
1976-01-01
This short paper considers the parameter-identification problem of general discrete-time, nonlinear, multiple input-multiple output dynamic systems with Gaussian white distributed measurement errors. Knowledge of the system parameterization is assumed to be available. Regions of constrained maximum likelihood (CML) parameter identifiability are established. A computation procedure employing interval arithmetic is proposed for finding explicit regions of parameter identifiability for the case of linear systems.
Material deformation dynamics at ultrahigh pressures and strain rates
Remington, B. A.; Park, H. S.; Maddox, B. R.; May, M. J.; Pollaine, S. M.; Prisbrey, S. T.; Rudd, R. E.; Hawreliak, J. A.; Perry, T. S.; Comley, A. J.; Wark, J. S.; Meyers, M. A.
2010-11-01
Solid-state dynamics experiments at extreme pressures, up to 10 Mbar, and strain rates (1.e6 -1.e8 1/s) are being developed for the NIF laser. The experimental methods are being developed on the Omega laser facility. VISAR measurements establish the ramped, high-pressure conditions. Recovery experiments offer a look at the residual microstructure. Dynamic diffraction measurements allow phase, shear stress (strength), and possibly twin volume fraction and dislocation density to be inferred. Constitutive models for material strength at these conditions by comparing 2D simulations with experiments measuring the Rayleigh-Taylor instability evolution in solid-state samples of vanadium and tantalum. The material deformation likely falls into the phonon drag regime. We estimate of the (microscopic) phonon drag coefficient, by relating to the (macroscopic) effective lattice viscosity.
Dynamic Optimization of a Polymer Flooding Process Based on Implicit Discrete Maximum Principle
Yang Lei
2012-01-01
Full Text Available Polymer flooding is one of the most important technologies for enhanced oil recovery (EOR. In this paper, an optimal control model of distributed parameter systems (DPSs for polymer injection strategies is established, which involves the performance index as maximum of the profit, the governing equations as the fluid flow equations of polymer flooding, and some inequality constraints as polymer concentration and injection amount limitation. The optimal control model is discretized by full implicit finite-difference method. To cope with the discrete optimal control problem (OCP, the necessary conditions for optimality are obtained through application of the calculus of variations and Pontryagin’s discrete maximum principle. A modified gradient method with new adjoint construction is proposed for the computation of optimal injection strategies. The numerical results of an example illustrate the effectiveness of the proposed method.
PPOOLEX experiments on dynamic loading with pressure feedback
Puustinen, M.; Laine, J.; Raesaenen, A. (Lappeenranta Univ. of Technology, Nuclear Safety Research Unit (Finland))
2011-01-15
This report summarizes the results of the dynamic loading experiments (DYN series) carried out with the scaled down, two compartment PPOOLEX test facility designed and constructed at LUT. Steam was blown into the dry well compartment and from there through the DN200 vertical blowdown pipe to the condensation pool filled with sub-cooled water. The main purpose of the experiments was to study dynamic loads caused by different condensation modes. Particularly, the effect of counterpressure on loads due to pressure oscillations induced by chugging was of interest. Before the experiments the condensation pool was filled with isothermal water so that the blowdown pipe outlet was submerged by 1.03-1.11 m. The initial temperature of the pool water varied from 11 deg. C to 63 deg. C, the steam flow rate from 290 g/s to 1220 g/s and the temperature of incoming steam from 132 deg. C to 182 deg. C. Non-condensables were pushed from the dry well into the gas space of the wet well with a short discharge of steam before the recorded period of the experiments. As a result of this procedure, the system pressure was at an elevated level in the beginning of the actual experiments. An increased counterpressure was used in the last experiment of the series. The diminishing effect of increased system pressure on chugging intensity and on measured loads is evident from the results of the last experiment. The highest pressure pulses both inside the blowdown pipe and in the condensation pool were about half of those measured with a lower system pressure but otherwise with similar test parameters. The experiments on dynamic loading gave expected results. The loads experienced by pool structures depended strongly on the steam mass flow rate, pool water temperature and system pressure. The DYN experiments indicated that chugging and condensation within the blowdown pipe cause significant dynamic loads in case of strongly sub-cooled pool water. The level of pool water temperature is decisive
PPOOLEX experiments on dynamic loading with pressure feedback
Puustinen, M.; Laine, J.; Raesaenen, A. (Lappeenranta Univ. of Technology, Nuclear Safety Research Unit (Finland))
2011-01-15
This report summarizes the results of the dynamic loading experiments (DYN series) carried out with the scaled down, two compartment PPOOLEX test facility designed and constructed at LUT. Steam was blown into the dry well compartment and from there through the DN200 vertical blowdown pipe to the condensation pool filled with sub-cooled water. The main purpose of the experiments was to study dynamic loads caused by different condensation modes. Particularly, the effect of counterpressure on loads due to pressure oscillations induced by chugging was of interest. Before the experiments the condensation pool was filled with isothermal water so that the blowdown pipe outlet was submerged by 1.03-1.11 m. The initial temperature of the pool water varied from 11 deg. C to 63 deg. C, the steam flow rate from 290 g/s to 1220 g/s and the temperature of incoming steam from 132 deg. C to 182 deg. C. Non-condensables were pushed from the dry well into the gas space of the wet well with a short discharge of steam before the recorded period of the experiments. As a result of this procedure, the system pressure was at an elevated level in the beginning of the actual experiments. An increased counterpressure was used in the last experiment of the series. The diminishing effect of increased system pressure on chugging intensity and on measured loads is evident from the results of the last experiment. The highest pressure pulses both inside the blowdown pipe and in the condensation pool were about half of those measured with a lower system pressure but otherwise with similar test parameters. The experiments on dynamic loading gave expected results. The loads experienced by pool structures depended strongly on the steam mass flow rate, pool water temperature and system pressure. The DYN experiments indicated that chugging and condensation within the blowdown pipe cause significant dynamic loads in case of strongly sub-cooled pool water. The level of pool water temperature is decisive
Bulgakov, V. K.; Strigunov, V. V.
2009-05-01
The Pontryagin maximum principle is used to prove a theorem concerning optimal control in regional macroeconomics. A boundary value problem for optimal trajectories of the state and adjoint variables is formulated, and optimal curves are analyzed. An algorithm is proposed for solving the boundary value problem of optimal control. The performance of the algorithm is demonstrated by computing an optimal control and the corresponding optimal trajectories.
Upper-Thermospheric Observations and Neutral-Gas Dynamics at High Latitudes During Solar Maximum.
1987-01-01
aeasFPIgure 6.5, ecep orB> oniios -40 TO~ -- 12 p . p’ T5 .ww i - IO RFS 5 183 maximum antisunward neutral winds located in the center of the polar cap. The...Solar flux variability in the *- Schumann-Runge continuum as a function of solar cycle 21. J. Geophys. Res., 85, 6063 - 6068, 1980c. Torr, M. R., P. G
Molecular Dynamics Simulations of a Pressure-induced Glass Transition
Shumway, S L; Jonsson, H; Shumway, Shelly L.; Clarke, Andrew S.
1994-01-01
We simulate the compression of a two-component Lennard-Jones liquid at a variety of constant temperatures using a molecular dynamics algorithm in an isobaric-isothermal ensemble. The viscosity of the liquid increases with pressure, undergoing a broadened transition into a structurally arrested, amorphous state. This transition, like the more familiar one induced by cooling, is correlated with a significant increase in icosahedral ordering. In fact, the structure of the final state, as measured by an analysis of the bonding, is essentially the same in the glassy, frozen state whether produced by squeezing or by cooling under pressure. We have computed an effective hard-sphere packing fraction at the transition, defining the transition pressure or temperature by a cutoff in the diffusion constant, analogous to the traditional laboratory definition of the glass transition by an arbitrary, low cutoff in viscosity. The packing fraction at this transition point is not constant, but is consistently higher for runs c...
Synchronous monitoring of muscle dynamics and muscle force for maximum isometric tetanus
Zakir Hossain, M.; Grill, Wolfgang
2010-03-01
Skeletal muscle is a classic example of a biological soft matter . At both macro and microscopic levels, skeletal muscle is exquisitely oriented for force generation and movement. In addition to the dynamics of contracting and relaxing muscle which can be monitored with ultrasound, variations in the muscle force are also expected to be monitored. To observe such force and sideways expansion variations synchronously for the skeletal muscle a novel detection scheme has been developed. As already introduced for the detection of sideways expansion variations of the muscle, ultrasonic transducers are mounted sideways on opposing positions of the monitored muscle. To detect variations of the muscle force, angle of pull of the monitored muscle has been restricted by the mechanical pull of the sonic force sensor. Under this condition, any variation in the time-of-flight (TOF) of the transmitted ultrasonic signals can be introduced by the variation of the path length between the transducers. The observed variations of the TOF are compared to the signals obtained by ultrasound monitoring for the muscle dynamics. The general behavior of the muscle dynamics and muscle force shows almost an identical concept. Since muscle force also relates the psychological boosting-up effects, the influence of boosting-up on muscle force and muscle dynamics can also be quantified form this study. Length-tension or force-length and force-velocity relationship can also be derived quantitatively with such monitoring.
Hubbard, L; Ziemer, B; Sadeghi, B; Javan, H; Lipinski, J; Molloi, S [University of California, Irvine, CA (United States)
2015-06-15
Purpose: To evaluate the accuracy of dynamic CT myocardial perfusion measurement using first pass analysis (FPA) and maximum slope models. Methods: A swine animal model was prepared by percutaneous advancement of an angioplasty balloon into the proximal left anterior descending (LAD) coronary artery to induce varying degrees of stenosis. Maximal hyperaemia was achieved in the LAD with an intracoronary adenosine drip (240 µg/min). Serial microsphere and contrast (370 mg/mL iodine, 30 mL, 5mL/s) injections were made over a range of induced stenoses, and dynamic imaging was performed using a 320-row CT scanner at 100 kVp and 200 mA. The FPA CT perfusion technique was used to make vessel-specific myocardial perfusion measurements. CT perfusion measurements using the FPA and maximum slope models were validated using colored microspheres as the reference gold standard. Results: Perfusion measurements using the FPA technique (P-FPA) showed good correlation with minimal offset when compared to perfusion measurements using microspheres (P- Micro) as the reference standard (P -FPA = 0.96 P-Micro + 0.05, R{sup 2} = 0.97, RMSE = 0.19 mL/min/g). In contrast, the maximum slope model technique (P-MS) was shown to underestimate perfusion when compared to microsphere perfusion measurements (P-MS = 0.42 P -Micro −0.48, R{sup 2} = 0.94, RMSE = 3.3 mL/min/g). Conclusion: The results indicate the potential for significant improvements in accuracy of dynamic CT myocardial perfusion measurement using the first pass analysis technique as compared with the standard maximum slope model.
Chen, José Enrique; Nurbakhsh, Babak; Layton, Gillian; Bussmann, Markus; Kishen, Anil
2014-08-01
Complexities in root canal anatomy and surface adherent biofilm structures remain as challenges in endodontic disinfection. The ability of an irrigant to penetrate into the apical region of a canal, along with its interaction with the root canal walls, will aid in endodontic disinfection. The aim of this study was to qualitatively examine the irrigation dynamics of syringe irrigation with different needle tip designs (open-ended and closed-ended), apical negative pressure irrigation with the EndoVac® system, and passive ultrasonic-assisted irrigation, using a computational fluid dynamics model. Syringe-based irrigation with a side-vented needle showed a higher wall shear stress than the open-ended but was localised to a small region of the canal wall. The apical negative pressure mode of irrigation generated the lowest wall shear stress, while the passive-ultrasonic irrigation group showed the highest wall shear stress along with the greatest magnitude of velocity.
Dynamic CT in patients with normal pressure hydrocephalus
Horibe, Kunio; Akagi, Katsuhito; Go, Junto; Kohmura, Eiji; Yamazaki, Mami
1984-11-01
In order to elucidate the cerebral circulation before and after shunt in patients with normal pressure hydrocephalus(NPH), a comparative study of 12 cases was performed using dynamic CT. In the effective shunt group, blood flow in the frontal gray matter and PVL was improved. The improvement in PVL was particularly marked. On the other hand, in the non-effective group, blood flow in the frontal gray matter was reduced compared with that before operation. In regard to predicting the effectiveness of the shunt from the features of preoperative dynamic CT study in NPH, it is suggested that blood flow in the frontal gray matter was lower in the effective shunt group than in the non-effective group. This cerebral circulation study using dynamic CT, which can be easily manipulated, is non-invasive, and is thought to be a useful method when highly reproducible parameters are chosen. (Author).
Molecular dynamics study of helium bubble pressure in titanium
Zhang, Bao-Ling; Wang, Jun; Hou, Qing
2011-03-01
In this paper, the pressure state of the helium bubble in titanium is simulated by a molecular dynamics (MD) method. First, the possible helium/vacancy ratio is determined according to therelation between the bubble pressure and helium/vacancy ratio; then the dependences of the helium bubble pressure on the bubble radius at different temperatures are studied. It is shown that the product of the bubble pressure and the radius is approximately a constant, a result justifying the pressure-radius relation predicted by thermodynamics-based theory for gas bubble. Furthermore, a state equation of the helium bubble is established based on the MD calculations. Comparison between the results obtained by the state equation and corresponding experimental data shows that the state equation can describe reasonably the state of helium bubble and thus could be used for Monte Carlo simulations of the evolution of helium bubble in metals. Project supported by the National Natural Science Foundation of China (Grant No. 10775101) and National Magnetic Confinement Fusion Program of China (Grant No. 2009GB106004).
V. Niranjan
2014-09-01
Full Text Available This paper introduces a new approach for enhancing the bandwidth of a low voltage CMOS current mirror. The proposed approach is based on utilizing body effect in a MOS transistor by connecting its gate and bulk terminals together for signal input. This results in boosting the effective transconductance of MOS transistor along with reduction of the threshold voltage. The proposed approach does not affect the DC gain of the current mirror. We demonstrate that the proposed approach features compatibility with widely used series-resistor technique for enhancing the current mirror bandwidth and both techniques have been employed simultaneously for maximum bandwidth enhancement. An important consequence of using both techniques simultaneously is the reduction of the series-resistor value for achieving the same bandwidth. This reduction in value is very attractive because a smaller resistor results in smaller chip area and less noise. PSpice simulation results using 180 nm CMOS technology from TSMC are included to prove the unique results. The proposed current mirror operates at 1Volt consuming only 102 µW and maximum bandwidth extension ratio of 1.85 has been obtained using the proposed approach. Simulation results are in good agreement with analytical predictions.
Wirz, D; Becker, R; Li, S Feng; Friederich, N F; Müller, W
2002-01-01
In vitro dynamic pressure measurements in the healthy and pathologically altered knee joint help to improve our understanding of the loading pattern on femorotibial surfaces. The aim of the study was to evaluate a piezoresistive pressure measuring system. A human cadaveric knee was mounted in a material-testing machine (Bionix 858) using a specially designed knee-holding device. Axial loading of the knee, flexed at 20o, at 500 N, 1000N and 1500 N was then carried out. For the static investigations, the piezoresistive measuring system (Tekscan), was compared with the FUJI measuring system. In addition, dynamic measurements were also performed with the Tekscan System. With the exception of the lateral compartment at a load of 1500 N, no differences in maximum pressures were observed between the two systems. Nor were there any differences with regard to contact surfaces, either in the medial or lateral compartment (p > 0.05). However, the reproducibility of the data was significantly higher with the Tekscan System (p Tekscan System proved to be more reliable than the FUJI System, and permits simultaneous measurements in both compartments. The Tekscan System is suitable for dynamic measurement of the femorotibial joint, and permits measurements to be made under more physiological conditions.
Molecular dynamics of water at high temperatures and pressures
Brodholt, John; Wood, Bernard
1990-09-01
There are currently no precise P-V-T data for water at pressures above 8.9 kbars and temperatures above 900°C. Many petrological processes in the lower crust and upper mantle take place under more extreme conditions, however and petrologists commonly rely on empirical equations of state such as the modified Redlich-Kwong equation (MRK) to extrapolate the low pressure data. In this study we have taken an alternative approach and attempted to simulate the P-V-T properties of water using molecular dynamics. The TIP4P intermolecular potential for H 2O ( JORGENSEN et al., 1983) has had considerable success predicting the properties of water at low temperatures and pressures up to 10 kbar ( MADURA et al., 1988). We have extended its application by making molecular dynamics (MD) simulations at a density of 1.0 g/cc from 300 to 2300 K and 0.5 to 40 kbars. The results agree with the P-V-T data of BURNHAM et al. (1969) (up to 10 kbars) with an average error of under 2%. This is a much better concordance than is obtained with any of the currently used versions of MRK. At 300 kbars and 2000 K the MD simulations predict densities within 8% of those obtained in the shock wave experiments of KORMER (1968). This is a very good agreement given the fact that water ionizes to some extent at high pressures ( MITCHELL and NELLIS, 1982) and we have made no provisions for this effect. We conclude that molecular dynamics simulations provide the possibility of estimating P-V-T properties in the upper mantle P-T regime with very good accuracy.
Material dynamics under extreme conditions of pressure and strain rate
Remington, B A; Allen, P; Bringa, E; Hawreliak, J; Ho, D; Lorenz, K T; Lorenzana, H; Meyers, M A; Pollaine, S W; Rosolankova, K; Sadik, B; Schneider, M S; Swift, D; Wark, J; Yaakobi, B
2005-09-06
Solid state experiments at extreme pressures (10-100 GPa) and strain rates ({approx}10{sup 6}-10{sup 8}s{sup -1}) are being developed on high-energy laser facilities, and offer the possibility for exploring new regimes of materials science. These extreme solid-state conditions can be accessed with either shock loading or with a quasi-isentropic ramped pressure drive. Velocity interferometer measurements establish the high pressure conditions. Constitutive models for solid-state strength under these conditions are tested by comparing 2D continuum simulations with experiments measuring perturbation growth due to the Rayleigh-Taylor instability in solid-state samples. Lattice compression, phase, and temperature are deduced from extended x-ray absorption fine structure (EXAFS) measurements, from which the shock-induced {alpha}-{omega} phase transition in Ti and the {alpha}-{var_epsilon} phase transition in Fe are inferred to occur on sub-nanosec time scales. Time resolved lattice response and phase can also be measured with dynamic x-ray diffraction measurements, where the elastic-plastic (1D-3D) lattice relaxation in shocked Cu is shown to occur promptly (< 1 ns). Subsequent large-scale molecular dynamics (MD) simulations elucidate the microscopic dynamics that underlie the 3D lattice relaxation. Deformation mechanisms are identified by examining the residual microstructure in recovered samples. The slip-twinning threshold in single-crystal Cu shocked along the [001] direction is shown to occur at shock strengths of {approx}20 GPa, whereas the corresponding transition for Cu shocked along the [134] direction occurs at higher shock strengths. This slip-twinning threshold also depends on the stacking fault energy (SFE), being lower for low SFE materials. Designs have been developed for achieving much higher pressures, P > 1000 GPa, in the solid state on the National Ignition Facility (NIF) laser.
2010-01-01
International audience; A drill-string is a slender structure that drills rock to search for oil. The nonlinear interaction between the bit and the rock is of great importance for the drill-string dynamics. The interaction model has uncertainties, which are modeled using the nonparametric probabilistic approach. This paper deals with a procedure to perform the identification of the dispersion parameter of the probabilistic model of uncertainties of a bit-rock interaction model. The bit-rock i...
Chen Aijun
2007-01-01
A dynamic weight function method is presented for dynamic stress intensity factors of circular disk with a radial edge crack under external impulsive pressure. The dynamic stresses in a circular disk are solved under abrupt step external pressure using the eigenfunction method.The solution consists of a quasi-static solution satisfying inhomogeneous boundary conditions and a dynamic solution satisfying homogeneous boundary conditions. By making use of FourierBessel series expansion, the history and distribution of dynamic stresses in the circular disk are derived. Furthermore, the equation for stress intensity factors under uniform pressure is used as the reference case, the weight function equation for the circular disk containing an edge crack is worked out, and the dynamic stress intensity factor equation for the circular disk containing a radial edge crack can be given. The results indicate that the stress intensity factors under sudden step external pressure vary periodically with time, and the ratio of the maximum value of dynamic stress intensity factors to the corresponding static value is about 2.0.
Silver, R.N.; Gubernatis, J.E.; Sivia, D.S. (Los Alamos National Lab., NM (USA)); Jarrell, M. (Ohio State Univ., Columbus, OH (USA). Dept. of Physics)
1990-01-01
In this article we describe the results of a new method for calculating the dynamical properties of the Anderson model. QMC generates data about the Matsubara Green's functions in imaginary time. To obtain dynamical properties, one must analytically continue these data to real time. This is an extremely ill-posed inverse problem similar to the inversion of a Laplace transform from incomplete and noisy data. Our method is a general one, applicable to the calculation of dynamical properties from a wide variety of quantum simulations. We use Bayesian methods of statistical inference to determine the dynamical properties based on both the QMC data and any prior information we may have such as sum rules, symmetry, high frequency limits, etc. This provides a natural means of combining perturbation theory and numerical simulations in order to understand dynamical many-body problems. Specifically we use the well-established maximum entropy (ME) method for image reconstruction. We obtain the spectral density and transport coefficients over the entire range of model parameters accessible by QMC, with data having much larger statistical error than required by other proposed analytic continuation methods.
Analysis of the flight dynamics of the Solar Maximum Mission (SMM) off-sun scientific pointing
Pitone, D. S.; Klein, J. R.; Twambly, B. J.
1990-01-01
Algorithms are presented which were created and implemented by the Goddard Space Flight Center's (GSFC's) Solar Maximum Mission (SMM) attitude operations team to support large-angle spacecraft pointing at scientific objectives. The mission objective of the post-repair SMM satellite was to study solar phenomena. However, because the scientific instruments, such as the Coronagraph/Polarimeter (CP) and the Hard X-ray Burst Spectrometer (HXRBS), were able to view objects other than the Sun, attitude operations support for attitude pointing at large angles from the nominal solar-pointing attitudes was required. Subsequently, attitude support for SMM was provided for scientific objectives such as Comet Halley, Supernova 1987A, Cygnus X-1, and the Crab Nebula. In addition, the analysis was extended to include the reverse problem, computing the right ascension and declination of a body given the off-Sun angles. This analysis led to the computation of the orbits of seven new solar comets seen in the field-of-view (FOV) of the CP. The activities necessary to meet these large-angle attitude-pointing sequences, such as slew sequence planning, viewing-period prediction, and tracking-bias computation are described. Analysis is presented for the computation of maneuvers and pointing parameters relative to the SMM-unique, Sun-centered reference frame. Finally, science data and independent attitude solutions are used to evaluate the larg-angle pointing performance.
Analysis of the flight dynamics of the Solar Maximum Mission (SMM) off-sun scientific pointing
Pitone, D. S.; Klein, J. R.; Twambly, B. J.
Algorithms are presented which were created and implemented by the Goddard Space Flight Center's (GSFC's) Solar Maximum Mission (SMM) attitude operations team to support large-angle spacecraft pointing at scientific objectives. The mission objective of the post-repair SMM satellite was to study solar phenomena. However, because the scientific instruments, such as the Coronagraph/Polarimeter (CP) and the Hard X-ray Burst Spectrometer (HXRBS), were able to view objects other than the Sun, attitude operations support for attitude pointing at large angles from the nominal solar-pointing attitudes was required. Subsequently, attitude support for SMM was provided for scientific objectives such as Comet Halley, Supernova 1987A, Cygnus X-1, and the Crab Nebula. In addition, the analysis was extended to include the reverse problem, computing the right ascension and declination of a body given the off-Sun angles. This analysis led to the computation of the orbits of seven new solar comets seen in the field-of-view (FOV) of the CP. The activities necessary to meet these large-angle attitude-pointing sequences, such as slew sequence planning, viewing-period prediction, and tracking-bias computation are described. Analysis is presented for the computation of maneuvers and pointing parameters relative to the SMM-unique, Sun-centered reference frame. Finally, science data and independent attitude solutions are used to evaluate the larg-angle pointing performance.
Efficient and exact maximum likelihood quantisation of genomic features using dynamic programming.
Song, Mingzhou; Haralick, Robert M; Boissinot, Stéphane
2010-01-01
An efficient and exact dynamic programming algorithm is introduced to quantise a continuous random variable into a discrete random variable that maximises the likelihood of the quantised probability distribution for the original continuous random variable. Quantisation is often useful before statistical analysis and modelling of large discrete network models from observations of multiple continuous random variables. The quantisation algorithm is applied to genomic features including the recombination rate distribution across the chromosomes and the non-coding transposable element LINE-1 in the human genome. The association pattern is studied between the recombination rate, obtained by quantisation at genomic locations around LINE-1 elements, and the length groups of LINE-1 elements, also obtained by quantisation on LINE-1 length. The exact and density-preserving quantisation approach provides an alternative superior to the inexact and distance-based univariate iterative k-means clustering algorithm for discretisation.
B. Schoser; Fong, E. (Edward); Geberhiwot, T. (Tarekegn); Hughes, D. (Derralynn); Kissel, J.T. (John T.); Madathil, S.C. (Shyam C.); Orlikowski, D. (David); Polkey, M.I. (Michael I.); M. Roberts (Mark); H.A.W.M. Tiddens (Harm); Young, P. (Peter)
2017-01-01
textabstractRespiratory muscle strength is a proven predictor of long-term outcome of neuromuscular disease (NMD), including amyotrophic lateral sclerosis, Duchenne muscular dystrophy, and spinal muscular atrophy. Maximal inspiratory pressure (MIP), a sensitive measure of respiratory muscle
Dynamic isolation technologies in negative pressure isolation wards
Xu, Zhonglin
2017-01-01
This book presents novel design principles and technologies for dynamic isolation based on experimental studies. These approaches have now become the local standard in Beijing and are currently being promoted for use nationwide. Further, the book provides details of measures and guidelines for the design process. Departing from the traditional understanding that isolation wards should be designed with high negative pressure, airtight doors and fresh air, it establishes the basis for designing biological clean rooms, including isolation wards, using a simple and convenient scientific approach. This book is intended for designers, engineers, researchers, hospital management staff and graduate students in heating ventilation air conditioning (HVAC), air cleaning technologies and related areas.
Dynamic response of nuclear fuel assembly excited by pressure pulsations
Zeman V.
2012-12-01
Full Text Available The paper deals with dynamic load calculation of the hexagonal type nuclear fuel assembly caused by spatial motion of the support plates in the reactor core. The support plate motion is excited by pressure pulsations generated by main circulation pumps in the coolant loops of the primary circuit of the nuclear power plant. Slightly different pumps revolutions generate the beat vibrations which causes an amplification of fuel assembly component dynamic deformations and fuel rods coating abrasion. The cyclic and central symmetry of the fuel assembly makes it possible the system decomposition into six identical revolved fuel rod segments which are linked with central tube and skeleton by several spacer grids in horizontal planes.The modal synthesis method with condensation of the fuel rod segments is used for calculation of the normal and friction forces transmitted between fuel rods and spacer grids cells.
Calandrini, V. [Centre de Biophysique Moleculaire, Rue Charles Sadron, 45071 Orleans (France); Synchrotron Soleil, L' Orme de Merisiers, B.P. 48, 91192 Gif-sur-Yvette (France); Hamon, V. [Centre de Biophysique Moleculaire, Rue Charles Sadron, 45071 Orleans (France); Hinsen, K. [Centre de Biophysique Moleculaire, Rue Charles Sadron, 45071 Orleans (France); Synchrotron Soleil, L' Orme de Merisiers, B.P. 48, 91192 Gif-sur-Yvette (France); Calligari, P. [Centre de Biophysique Moleculaire, Rue Charles Sadron, 45071 Orleans (France); Institut Laue-Langevin, 6 Rue Jules Horowitz, B.P. 156, 38042 Grenoble (France); Laboratoire Leon Brillouin, CEA Saclay, 91191 Gif-sur-Yvette (France); Bellissent-Funel, M.-C. [Laboratoire Leon Brillouin, CEA Saclay, 91191 Gif-sur-Yvette (France); Kneller, G.R. [Centre de Biophysique Moleculaire, Rue Charles Sadron, 45071 Orleans (France); Synchrotron Soleil, L' Orme de Merisiers, B.P. 48, 91192 Gif-sur-Yvette (France)], E-mail: kneller@cnrs-orleans.fr
2008-04-18
This paper presents a study of the influence of non-denaturing hydrostatic pressure on the relaxation dynamics of lysozyme in solution, which combines molecular dynamics simulations and quasielastic neutron scattering experiments. We compare results obtained at ambient pressure and at 3 kbar. Experiments have been performed at pD 4.6 and at a protein concentration of 60 mg/ml. For both pressures we checked the monodispersity of the protein solution by small angle neutron scattering. To interpret the simulation results and the experimental data, we adopt the fractional Ornstein-Uhlenbeck process as a model for the internal relaxation dynamics of the protein. On the experimental side, global protein motions are accounted for by the model of free translational diffusion, neglecting the much slower rotational diffusion. We find that the protein dynamics in the observed time window from about 1 to 100 ps is slowed down under pressure, while its fractal characteristics is preserved, and that the amplitudes of the motions are reduced by about 20%. The slowing down of the relaxation is reduced with increasing q-values, where more localized motions are seen.
Modeling plasma pressure anisotropy's effect on Saturn's global magnetospheric dynamics
Tilley, M.; Harnett, E. M.; Winglee, R.
2014-12-01
A 3D multi-fluid, multi-scale plasma model with a complete treatment of plasma pressure anisotropy is employed to study global magnetospheric dynamics at Saturn. Cassini has observed anisotropies in the Saturnian magnetosphere, and analyses have showed correlations between anisotropy and plasma convection, ring current structure and intensity, confinement of plasma to the equatorial plane, as well as mass transport to the outer magnetosphere. The energization and transport of plasma within Saturn's magnetosphere is impactful upon the induced magnetic environments and atmospheres of potentially habitable satellites such as Enceladus and Titan. Recent efforts to couple pressure anisotropy with 3D multi-fluid plasma modeling have shown a significant move towards matching observations for simulations of Earth's magnetosphere. Our approach is used to study the effects of plasma pressure anisotropy on global processes of the Saturnian magnetosphere such as identifying the effect of pressure anisotropy on the centrifugal interchange instability. Previous simulation results have not completely replicated all aspects of the structure and formation of the interchange 'fingers' measured by Cassini at Saturn. The related effects of anisotropy, in addition to those mentioned above, include contribution to formation of MHD waves (e.g. reduction of Alfvén wave speed) and formation of firehose and mirror instabilities. An accurate understanding of processes such as the interchange instability is required if a complete picture of mass and energy transport at Saturn is to be realized. The results presented here will detail how the inclusion of a full treatment of pressure anisotropy for idealized solar wind conditions modifies the interchange structure and shape of the tail current sheet. Simulation results are compared to observations made by Cassini.
Maximum-Likelihood Sequence Detector for Dynamic Mode High Density Probe Storage
Kumar, Naveen; Ramamoorthy, Aditya; Salapaka, Murti
2009-01-01
There is an ever increasing need for storing data in smaller and smaller form factors driven by the ubiquitous use and increased demands of consumer electronics. A new approach of achieving a few Tb per in2 areal densities, utilizes a cantilever probe with a sharp tip that can be used to deform and assess the topography of the material. The information may be encoded by means of topographic profiles on a polymer medium. The prevalent mode of using the cantilever probe is the static mode that is known to be harsh on the probe and the media. In this paper, the high quality factor dynamic mode operation, which is known to be less harsh on the media and the probe, is analyzed for probe based high density data storage purposes. It is demonstrated that an appropriate level of abstraction is possible that obviates the need for an involved physical model. The read operation is modeled as a communication channel which incorporates the inherent system memory due to the intersymbol interference and the cantilever state ...
Zhaoyong Mao
2016-01-01
Full Text Available This paper addresses the power generation control system of a new drag-type Vertical Axis Turbine with several retractable blades. The returning blades can be entirely hidden in the drum, and negative torques can then be considerably reduced as the drum shields the blades. Thus, the power efficiency increases. Regarding the control, a Linear Quadratic Tracking (LQT optimal control algorithm for Maximum Power Point Tracking (MPPT is proposed to ensure that the wave energy conversion system can operate highly effectively under fluctuating conditions and that the tracking process accelerates over time. Two-dimensional Computational Fluid Dynamics (CFD simulations are performed to obtain the maximum power points of the turbine’s output. To plot the tip speed ratio curve, the least squares method is employed. The efficacy of the steady and dynamic performance of the control strategy was verified using Matlab/Simulink software. These validation results show that the proposed system can compensate for power fluctuations and is effective in terms of power regulation.
Optimization of stomatal conductance for maximum carbon gain under dynamic soil moisture
Manzoni, Stefano; Vico, Giulia; Palmroth, Sari; Porporato, Amilcare; Katul, Gabriel
2013-12-01
Optimization theories explain a variety of forms and functions in plants. At the leaf scale, it is often hypothesized that carbon gain is maximized, thus providing a quantifiable objective for a mathematical definition of optimality conditions. Eco-physiological trade-offs and limited resource availability introduce natural bounds to this optimization process. In particular, carbon uptake from the atmosphere is inherently linked to water losses from the soil as water is taken up by roots and evaporated. Hence, water availability in soils constrains the amount of carbon that can be taken up and assimilated into new biomass. The problem of maximizing photosynthesis at a given water availability by modifying stomatal conductance, the plant-controlled variable to be optimized, has been traditionally formulated for short time intervals over which soil moisture changes can be neglected. This simplification led to a mathematically open solution, where the undefined Lagrange multiplier of the optimization (equivalent to the marginal water use efficiency, λ) is then heuristically determined via data fitting. Here, a set of models based on different assumptions that account for soil moisture dynamics over an individual dry-down are proposed so as to provide closed analytical expressions for the carbon gain maximization problem. These novel solutions link the observed variability in λ over time, across soil moisture changes, and at different atmospheric CO2 concentrations to water use strategies ranging from intensive, in which all soil water is consumed by the end of the dry-down period, to more conservative, in which water stress is avoided by reducing transpiration.
Constant pressure and temperature discrete-time Langevin molecular dynamics.
Grønbech-Jensen, Niels; Farago, Oded
2014-11-21
We present a new and improved method for simultaneous control of temperature and pressure in molecular dynamics simulations with periodic boundary conditions. The thermostat-barostat equations are built on our previously developed stochastic thermostat, which has been shown to provide correct statistical configurational sampling for any time step that yields stable trajectories. Here, we extend the method and develop a set of discrete-time equations of motion for both particle dynamics and system volume in order to seek pressure control that is insensitive to the choice of the numerical time step. The resulting method is simple, practical, and efficient. The method is demonstrated through direct numerical simulations of two characteristic model systems-a one-dimensional particle chain for which exact statistical results can be obtained and used as benchmarks, and a three-dimensional system of Lennard-Jones interacting particles simulated in both solid and liquid phases. The results, which are compared against the method of Kolb and Dünweg [J. Chem. Phys. 111, 4453 (1999)], show that the new method behaves according to the objective, namely that acquired statistical averages and fluctuations of configurational measures are accurate and robust against the chosen time step applied to the simulation.
Mukhopadhyay, B.; Fritz, M.; Mackowiak, P.; Vu, T. C.; Ehrmann, O.; Lang, K.-D.; Ngo, H.-D.
2013-05-01
Design, simulation, fabrication, and characterization of novel MEMS pressure sensors with new back-side-direct-exposure packaging concept are presented. The sensor design is optimized for harsh environments e.g. space, military, offshore and medical applications. Unbreakable connection between the active side of the Si-sensor and the protecting glass capping was realized by anodic bonding using a thin layer of metal. To avoid signal corruption of the measured pressure caused by an encapsulation system, the media has direct contact to the backside of the Si membrane and can deflect it.
Quantum molecular dynamics simulations of beryllium at high pressures
Desjarlais, Michael; Knudson, Marcus
2008-03-01
The phase boundaries and high pressure melt properties of beryllium have been the subject of several recent experimental and theoretical studies. The interest is motivated in part by the use of beryllium as an ablator material in inertial confinement fusion capsule designs. In this work, the high pressure melt curve, Hugoniot crossings, sound speeds, and phase boundaries of beryllium are explored with DFT based quantum molecular dynamics calculations. The entropy differences between the various phases of beryllium are extracted in the vicinity of the melt curve and agree favorably with earlier theoretical work on normal melting. High velocity flyer plate experiments with beryllium targets on Sandia's Z machine have generated high quality data for the Hugoniot, bulk sound speeds, and longitudinal sound speeds. This data provides a tight constraint on the pressure for the onset of shock melting of beryllium and intriguing information on the solid phase prior to melt. The results of the QMD calculations and the experimental results will be compared, and implications for the HCP and BCC phase boundaries of beryllium will be presented.
Combustion dynamics of low vapour pressure nanofuel droplets
Pandey, Khushboo; Chattopadhyay, Kamanio; Basu, Saptarshi
2017-07-01
Multiscale combustion dynamics, shape oscillations, secondary atomization, and precipitate formation have been elucidated for low vapour pressure nanofuel [n-dodecane seeded with alumina nanoparticles (NPs)] droplets. Dilute nanoparticle loading rates (0.1%-1%) have been considered. Contrary to our previous studies of ethanol-water blend (high vapour pressure fuel), pure dodecane droplets do not exhibit internal boiling after ignition. However, variation in surface tension due to temperature causes shape deformations for pure dodecane droplets. In the case of nanofuels, intense heat release from the enveloping flame leads to the formation of micron-size aggregates (of alumina NPS) which serve as nucleation sites promoting heterogeneous boiling. Three boiling regimes (A, B, and C) have been identified with varying bubble dynamics. We have deciphered key mechanisms responsible for the growth, transport, and rupture of the bubbles. Bubble rupture causes ejections of liquid droplets termed as secondary atomization. Ejection of small bubbles (mode 1) resembles the classical vapour bubble collapse mechanism near a flat free surface. However, large bubbles induce severe shape deformations as well as bulk oscillations. Rupture of large bubbles results in high speed liquid jet formation which undergoes Rayleigh-Plateau tip break-up. Both modes contribute towards direct fuel transfer from the droplet surface to flame envelope bypassing diffusion limitations. Combustion lifetime of nanofuel droplets consequently has two stages: stage I (where bubble dynamics are dominant) and stage II (formation of gelatinous mass due to continuous fuel depletion; NP agglomeration). In the present work, variation of flame dynamics and spatio-temporal heat release (HR) have been analysed using high speed OH* chemiluminescence imaging. Fluctuations in droplet shape and flame heat release are found to be well correlated. Droplet flame is bifurcated in two zones (I and II). Flame response is
Pan, Zhao; Whitehead, Jared; Thomson, Scott; Truscott, Tadd
2016-08-01
Obtaining pressure field data from particle image velocimetry (PIV) is an attractive technique in fluid dynamics due to its noninvasive nature. The application of this technique generally involves integrating the pressure gradient or solving the pressure Poisson equation using a velocity field measured with PIV. However, very little research has been done to investigate the dynamics of error propagation from PIV-based velocity measurements to the pressure field calculation. Rather than measure the error through experiment, we investigate the dynamics of the error propagation by examining the Poisson equation directly. We analytically quantify the error bound in the pressure field, and are able to illustrate the mathematical roots of why and how the Poisson equation based pressure calculation propagates error from the PIV data. The results show that the error depends on the shape and type of boundary conditions, the dimensions of the flow domain, and the flow type.
Pan, Zhao; Thomson, Scott; Truscott, Tadd
2016-01-01
Obtaining pressure field data from particle image velocimetry (PIV) is an attractive technique in fluid dynamics due to its noninvasive nature. The application of this technique generally involves integrating the pressure gradient or solving the pressure Poisson equation using a velocity field measured with PIV. However, very little research has been done to investigate the dynamics of error propagation from PIV-based velocity measurements to the pressure field calculation. Rather than measure the error through experiment, we investigate the dynamics of the error propagation by examining the Poisson equation directly. We analytically quantify the error bound in the pressure field, and are able to illustrate the mathematical roots of why and how the Poisson equation based pressure calculation propagates error from the PIV data. The results show that the error depends on the shape and type of boundary conditions, the dimensions of the flow domain, and the flow type.
Pan, Zhao; Whitehead, Jared; Thomson, Scott; Truscott, Tadd
2016-08-01
Obtaining pressure field data from particle image velocimetry (PIV) is an attractive technique in fluid dynamics due to its noninvasive nature. The application of this technique generally involves integrating the pressure gradient or solving the pressure Poisson equation using a velocity field measured with PIV. However, very little research has been done to investigate the dynamics of error propagation from PIV-based velocity measurements to the pressure field calculation. Rather than measure the error through experiment, we investigate the dynamics of the error propagation by examining the Poisson equation directly. We analytically quantify the error bound in the pressure field, and are able to illustrate the mathematical roots of why and how the Poisson equation based pressure calculation propagates error from the PIV data. The results show that the error depends on the shape and type of boundary conditions, the dimensions of the flow domain, and the flow type.
Tadashi Wakayama
Full Text Available Nasal obstruction is a common problem in continuous positive airway pressure (CPAP therapy for obstructive sleep apnea and limits treatment compliance. The purpose of this study is to model the effects of nasal obstruction on airflow parameters under CPAP using computational fluid dynamics (CFD, and to clarify quantitatively the relation between airflow velocity and pressure loss coefficient in subjects with and without nasal obstruction.We conducted an observational cross-sectional study of 16 Japanese adult subjects, of whom 9 had nasal obstruction and 7 did not (control group. Three-dimensional reconstructed models of the nasal cavity and nasopharynx with a CPAP mask fitted to the nostrils were created from each subject's CT scans. The digital models were meshed with tetrahedral cells and stereolithography formats were created. CPAP airflow simulations were conducted using CFD software. Airflow streamlines and velocity contours in the nasal cavities and nasopharynx were compared between groups. Simulation models were confirmed to agree with actual measurements of nasal flow rate and with pressure and flow rate in the CPAP machine.Under 10 cmH2O CPAP, average maximum airflow velocity during inspiration was 17.6 ± 5.6 m/s in the nasal obstruction group but only 11.8 ± 1.4 m/s in the control group. The average pressure drop in the nasopharynx relative to inlet static pressure was 2.44 ± 1.41 cmH2O in the nasal obstruction group but only 1.17 ± 0.29 cmH2O in the control group. The nasal obstruction and control groups were clearly separated by a velocity threshold of 13.5 m/s, and pressure loss coefficient threshold of approximately 10.0. In contrast, there was no significant difference in expiratory pressure in the nasopharynx between the groups.This is the first CFD analysis of the effect of nasal obstruction on CPAP treatment. A strong correlation between the inspiratory pressure loss coefficient and maximum airflow velocity was found.
Full Dynamic-Range Pressure Sensor Matrix Based on Optical and Electrical Dual-Mode Sensing.
Wang, Xiandi; Que, Miaoling; Chen, Mengxiao; Han, Xun; Li, Xiaoyi; Pan, Caofeng; Wang, Zhong Lin
2017-01-06
Pressure sensor matrix (PSM) with full dynamic range can accurately detect and spatially map pressure profile. A 100 × 100 large-scale PSM gives both electrical and optical signals by itself without applying an external power. The device represents a major step toward digital imaging and visible display of pressure distribution covers a large dynamic range.
Vilmos Simon
2013-01-01
The aim of this study is to define optimal tooth modifications,introduced by appropriately chosen head-cutter geometry and machine tool setting,to simultaneously minimize tooth contact pressure and angular displacement error of the driven gear (transmission error) of face-hobbed spiral bevel gears.As a result of these modifications,the gear pair becomes mismatched,and a point contact replaces the theoretical line contact.In the applied loaded tooth contact analysis it is assumed that the point contact under load is spreading over a surface along the whole or part of the “potential” contact line.A computer program was developed to implement the formulation provided above.By using this program the influence of tooth modifications introduced by the variation in machine tool settings and in head cutter data on load and pressure distributions,transmission errors,and fillet stresses is investigated and discussed.The correlation between the ease-off obtained by pinion tooth modifications and the corresponding tooth contact pressure distribution is investigated and the obtained results are presented.
Dynamic high pressure-induced gelation in milk protein model systems.
Venir, E; Marchesini, G; Biasutti, M; Innocente, N
2010-02-01
The structure-functional properties of milk proteins are relevant in food formulation. Recently, there has been growing interest in dynamic high-pressure homogenization effects on the rheological-structural properties of food macromolecules and proteins. The aim of this work was to evaluate the effects of different homogenization pressures on rheological properties of milk protein model systems. For this purpose, sodium caseinate (SC) and whey protein concentrate (WPC) were dispersed at different concentrations (1, 2, and 4%), pasteurized, and then homogenized at 0, 18MPa (conventional pressure, CP), 100MPa (high pressure, HP), and 150MPa (HP+). Differences in viscosity were observed between WPC and casein dispersions according to concentration, heat treatment, and homogenization pressure. Mechanical spectra described the characteristic behavior of solutions except for the WPC 4% pasteurized sample, in which a network formed but was broken after homogenization. Dispersions with different ratios of WPC and SC were also made. In these systems, pasteurization alone did not determine network formation, whereas homogenization alone promoted cold gelation. A total concentration of at least 4% was required for homogenization-induced gelation in pasteurized and unpasteurized samples. Gels with higher elastic modulus (G') were obtained in more concentrated samples, and a bell-shaped behavior with the maximum value at HP was observed. The HP treatment produced stronger gels than the CP treatment. Similar G' values were obtained when different concentrations, pasteurization conditions, and homogenization pressures were combined. Therefore, by setting appropriate process conditions, systems or gels with tailored characteristics may be obtained from dispersions of milk proteins. Copyright 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
Whole-body mathematical model for simulating intracranial pressure dynamics
Lakin, William D. (Inventor); Penar, Paul L. (Inventor); Stevens, Scott A. (Inventor); Tranmer, Bruce I. (Inventor)
2007-01-01
A whole-body mathematical model (10) for simulating intracranial pressure dynamics. In one embodiment, model (10) includes 17 interacting compartments, of which nine lie entirely outside of intracranial vault (14). Compartments (F) and (T) are defined to distinguish ventricular from extraventricular CSF. The vasculature of the intracranial system within cranial vault (14) is also subdivided into five compartments (A, C, P, V, and S, respectively) representing the intracranial arteries, capillaries, choroid plexus, veins, and venous sinus. The body's extracranial systemic vasculature is divided into six compartments (I, J, O, Z, D, and X, respectively) representing the arteries, capillaries, and veins of the central body and the lower body. Compartments (G) and (B) include tissue and the associated interstitial fluid in the intracranial and lower regions. Compartment (Y) is a composite involving the tissues, organs, and pulmonary circulation of the central body and compartment (M) represents the external environment.
Manifestation of constrained dynamics in a low pressure spark
Auluck, S K H
2013-01-01
Some features of neutron emission from dense plasma focus suggest that the participating deuterons have energy in the range of 105 eV and have a directionality of toroidal motion. Theoretical models of these devices assume that the plasma evolves through a purely irrotational flow and thus fail to predict such solenoidal flow on the scale of the plasma dimensions. Predictions of a relaxation theory are consistent with experimental data [S K H Auluck, Physics of Plasmas,18, 032508 (2011)], but the assumptions upon which it is based are not compatible with known features of these devices. There is thus no satisfactory theoretical construct which provides the necessity for solenoidal flow in these devices. This paper proposes such theoretical construct, namely, the principle of constrained dynamics, and describes an experiment which provides support for this idea. The experiment consisted of low inductance, self-breaking spark discharge in helium at a pressure ~100 hPa between two pointed electrodes separated by...
Nonlinear radiation pressure dynamics in an optomechanical crystal
Krause, Alex G; Ludwig, Max; Safavi-Naeini, Amir H; Chan, Jasper; Marquardt, Florian; Painter, Oskar
2015-01-01
Utilizing a silicon nanobeam optomechanical crystal, we investigate the attractor diagram arising from the radiation pressure interaction between a localized optical cavity at $\\lambda = 1552$nm and a mechanical resonance at $\\omega/2\\pi = 3.72$GHz. At a temperature of $T \\approx 10$K, highly nonlinear driving of mechanical motion is observed via continuous wave optical pumping. Introduction of a time-dependent (modulated) optical pump is used to steer the system towards an otherwise inaccessible dynamically stable attractor in which mechanical self-oscillation occurs for an optical pump red-detuned from the cavity resonance. An analytical model incorporating thermo-optic effects due to optical absorption heating is developed, and found to accurately predict the measured device behavior.
Dynamic range and sensitivity of field emission pressure sensors with non-silicon membranes
Badi, N., E-mail: nbadi@uh.edu [Center for Advanced Materials (CAM), University of Houston, Houston, TX 77204-5004 (United States); Physics Department, University of Houston, Houston, TX 77204-5005 (United States); Bensaoula, A. [Physics Department, University of Houston, Houston, TX 77204-5005 (United States); Nair, A.M. [Center for Advanced Materials (CAM), University of Houston, Houston, TX 77204-5004 (United States)
2013-11-15
We report on the dynamic range and sensitivity simulations of a functional field emission-based pressure sensor. The device comprises a titanium nitride membrane acting as the anode in front of a flat boron nitride cold cathode emitter. We previously reported the problem of non-linearity of these sensors and studied their performance for different membrane geometries and membranes using different materials such as Si, Ti, Ta, and TiN [N. Badi et al., Appl. Surf. Sci. 256 (2010) 4990–4994]. Of the materials investigated, TiN seems to have the most desirable characteristics with respect to linearity. In this paper we report on the effects of membrane dimensions on the sensor operation. Results show how a sensor having a TiN membrane of standard dimension can be tuned during operation to have maximum dynamic range without affecting the sensitivity. The membrane dimensions have a strong effect on the device dynamic range. Small portions of the entire range could however be selected by changing the device operating voltage. We also have shown that smaller area membranes result in devices with better response in terms of constant sensitivity, as compared to those with thicker membranes. The device can be operated over its entire dynamic range by tuning the operating voltage of the device to keep the sensitivity a constant.
Molecular Dynamics Simulations of Liquid Phosphorus at High Temperature and Pressure
WU Yan-Ning; ZHAO Gang; LIU Chang-Song; ZHU Zhen-Gang
2008-01-01
By performing ab initio molecular dynamics simulations, we have investigated the mierostructure, dynam-ical and electronic properties of liquid phosphorus (P) under high temperature and pressure. In our simulations, the calculated coordination number (CN) changes discontinuously with density, and seems to increase rapidly after liquid P is compressed to 2.5 g/cm3. Under compression, liquid P shows the first-order liquid-liquid phase transition from the molecular liquid composed of the tetrahedral P4 molecules to complex polymeric form with three-dimensional network structure, accompanied by the nonmetal to metal transition of the electronic structure. The order parameters Q6 and Q4 are sensitive to the microstructural change of liquid P. By calculating diffusion coefficients, we show the dynamical anomaly of liquid P by compression. At lower temperatures, a maximum exists at the diffusion coefficients as a function of density; at higher temperatures, the anomalous behavior is weakened. The excess entropy shows the same phenom-ena as the diffusion coefficients. By analysis of the angle distribution functions and angular limited triplet correlation functions, we can clearly find that the Peierls distortion in polymeric form of liquid P is reduced by further compression.
Riley, Pete; Mikic, Z.; Linker, J. A.
2003-01-01
In this study we describe a series of MHD simulations covering the time period from 12 January 1999 to 19 September 2001 (Carrington Rotation 1945 to 1980). This interval coincided with: (1) the Sun s approach toward solar maximum; and (2) Ulysses second descent to the southern polar regions, rapid latitude scan, and arrival into the northern polar regions. We focus on the evolution of several key parameters during this time, including the photospheric magnetic field, the computed coronal hole boundaries, the computed velocity profile near the Sun, and the plasma and magnetic field parameters at the location of Ulysses. The model results provide a global context for interpreting the often complex in situ measurements. We also present a heuristic explanation of stream dynamics to describe the morphology of interaction regions at solar maximum and contrast it with the picture that resulted from Ulysses first orbit, which occurred during more quiescent solar conditions. The simulation results described here are available at: http://sun.saic.com.
Evaluating road surface conditions using dynamic tire pressure sensor
Zhao, Yubo; Wu, H. Felix; McDaniel, J. Gregory; Wang, Ming L.
2014-03-01
In order to best prioritize road maintenance, the level of deterioration must be known for all roads in a city's network. Pavement Condition Index (PCI) and International Roughness Index (IRI) are two standard methods for obtaining this information. However, IRI is substantially easier to measure. Significant time and money could be saved if a method were developed to estimate PCI from IRI. This research introduces a new method to estimate IRI and correlate IRI with PCI. A vehicle-mounted dynamic tire pressure sensor (DTPS) system is used. The DTPS measures the signals generated from the tire/road interaction while driving. The tire/road interaction excites surface waves that travel through the road. DTPS, which is mounted on the tire's valve stem, measures tire/road interaction by analyzing the pressure change inside the tire due to the road vibration, road geometry and tire wall vibration. The road conditions are sensible to sensors in a similar way to human beings in a car. When driving on a smooth road, tire pressure stays almost constant and there are minimal changes in the DTPS data. When driving on a rough road, DTPS data changes drastically. IRI is estimated from the reconstructed road profile using DTPS data. In order to correlate IRI with PCI, field tests were conducted on roads with known PCI values in the city of Brockton, MA. Results show a high correlation between the estimated IRI values and the known PCI values, which suggests that DTPS-based IRI can provide accurate predictions of PCI.
Dynamic CT study of normal-pressure hydrocephalus
Tamaki, Norihiko; Kojima, Noriaki; Shirakuni, Takayuki; Matsumoto, Satoshi
1984-08-01
A dynamic CT study was performed in 14 patients with presumed normal-pressure hydrocephalus, of which diagnosis had been made by clinical symptomatology, CT findings, the results of the continuous monitoring of intracranial pressure, and CT cisternographic findings. It is demonstrated by serial CT scans that the cerebral arteries and arterioles were initially filled with contrast media, which were followed by the symmetrical and homogeneous staining of the cortical gray matter and basal ganglia, the diencephalia, and then the white matter. The venous system was stained in the late phase. The contrast media was finally cleared out from the intracranial space. Thus, the staining of the cerebral vessels and brain parenchym showed a uniform pattern in all cases. Functional CT images revealed that the patients with normal-pressure hydrocephalus who responded well to the shunt procedure had areas of prolonged mean circulation time scattered diffusely not only in the paraventricular structures, but also in the cortical gray matter of all the cerebral hemispheres. Following the shunt procedure, the hemodynamic conditions improved in almost all the areas mentioned above, but especially in the frontal and temporal gray matters and the paraventricular structures. In the patients who did not benefit from the shunt operation, however, there was no special abnormality of hemodynamic distribution. The analysis of the mean circulation time in the region of interest demonstrated that a significant improvement in cerebral hemodynamics was noted in the regions of the frontal and temporal gray matters, the periventricular white matter, and the caudate nucleus in patients who benefitted from the shunt operation. In patients who did not improve after the ventriculo-peritoneal shunt, however, there was no statistically significant difference between pre- and post-shunt mean circulation times. (J.P.N.).
Delocalization of Electrons in Strong Insulators at High Dynamic Pressures
William J. Nellis
2011-06-01
Full Text Available Systematics of material responses to shock flows at high dynamic pressures are discussed. Dissipation in shock flows drives structural and electronic transitions or crossovers, such as used to synthesize metallic liquid hydrogen and most probably Al2O3 metallic glass. The term “metal” here means electrical conduction in a degenerate system, which occurs by band overlap in degenerate condensed matter, rather than by thermal ionization in a non-degenerate plasma. Since H2 and probably disordered Al2O3 become poor metals with minimum metallic conductivity (MMC virtually all insulators with intermediate strengths do so as well under dynamic compression. That is, the magnitude of strength determines the split between thermal energy and disorder, which determines material response. These crossovers occur via a transition from insulators with electrons localized in chemical bonds to poor metals with electron energy bands. For example, radial extents of outermost electrons of Al and O atoms are 7 a0 and 4 a0, respectively, much greater than 1.7 a0 needed for onset of hybridization at 300 GPa. All such insulators are Mott insulators, provided the term “correlated electrons” includes chemical bonds.
Phase Synchronization of Pressure-Flow Fluctuations: A measure of cerebral autoregulation dynamics
Chen, Z; Ivanov, P C; Novák, V; Stanley, H E
2006-01-01
We employ a synchronization method to investigate the relationship between the blood flow velocities (BFV) in the middle cerebral arteries (MCA) and beat-to-beat blood pressure (BP) recorded from a finger in healthy and post-stroke subjects during four different physiologic conditions: supine, head-up tilt, hyperventilation and CO$_2$ rebreathing in upright position. To evaluate whether instantaneous BP changes are synchronized with changes in the BFV, we compare dynamical patterns in the instantaneous phases of these signals, obtained from the Hilbert transform, as a function of time. We find that in post-stroke subjects the instantaneous phase increments of BP and BFV exhibit well pronounced patterns that remain stable in time for all four physiologic conditions, while in healthy subjects these patterns are different, less pronounced and more variable. Further, we show that the instantaneous phase increments of BP and BFV are cross-correlated even within a single heartbeat cycle. The maximum correlation str...
Dynamics of apokamp-type atmospheric pressure plasma jets
Sosnin, Eduard A.; Panarin, Victor A.; Skakun, Victor S.; Baksht, Evgeny Kh.; Tarasenko, Victor F.
2017-02-01
The paper describes a new discharge source of atmospheric pressure plasma jets (APPJs) in air with no gas supply through the discharge region. In this discharge mode, plasma jets develop from the bending point of a bright current channel between two electrodes and are therefore termed an apokamp (from Greek `off' and `bend'). The apokamp can represent single plasma jets of length up 6 cm or several jets, and the temperature of such jets can range from more than 1000 °C at their base to 100-250 °C at their tip. Apokamps are formed at maximum applied voltage of positive polarity, provided that the second electrode is capacitively decoupled with ground. According to high-speed photography with time resolution from several nanoseconds to several tens of nanoseconds, the apokamp consists of a set of plasma bullets moving with a velocity of 100-220 km/s, which excludes the convective mechanism of plasma decay. Estimates on a 100-ns scale show that the near-electrode zones and the zones from which apokamps develop are close in temperature.
Nair, Sandeep P.; Shiau, Deng-Shan; Principe, Jose C.; Iasemidis, Leonidas D.; Pardalos, Panos M.; Norman, Wendy M.; Carney, Paul R.; Sackellares, J. Chris
2009-01-01
Analysis of intracranial electroencephalographic (iEEG) recordings in patients with temporal lobe epilepsy (TLE) has revealed characteristic dynamical features that distinguish the interictal, ictal, and postictal states and inter-state transitions. Experimental investigations into the mechanisms underlying these observations require the use of an animal model. A rat TLE model was used to test for differences in iEEG dynamics between well-defined states and to test specific hypotheses: 1) the short-term maximum Lyapunov exponent (STLmax), a measure of signal order, is lowest and closest in value among cortical sites during the ictal state, and highest and most divergent during the postictal state; 2) STLmax values estimated from the stimulated hippocampus are the lowest among all cortical sites; and 3) the transition from the interictal to ictal state is associated with a convergence in STLmax values among cortical sites. iEEGs were recorded from bilateral frontal cortices and hippocampi. STLmax and T-index (a measure of convergence/divergence of STLmax between recorded brain areas) were compared among the four different periods. Statistical tests (ANOVA and multiple comparisons) revealed that ictal STLmax was lower (p < 0.05) than other periods, STLmax values corresponding to the stimulated hippocampus were lower than those estimated from other cortical regions, and T-index values were highest during the postictal period and lowest during the ictal period. Also, the T-index values corresponding to the preictal period were lower than those during the interictal period (p < 0.05). These results indicate that a rat TLE model demonstrates several important dynamical signal characteristics similar to those found in human TLE and support future use of the model to study epileptic state transitions. PMID:19100262
van der Horst, Arjen; Van't Veer, Marcel; van der Sligte, Robin A M; Rutten, Marcel C M; Pijls, Nico H J; van de Vosse, Frans N
2013-03-01
Measurement of coronary pressure and absolute flow dynamics have shown great potential in discerning different types of coronary circulatory disease. In the present study, the feasibility of assessing pressure and flow dynamics with a combination of two thermal methods, developed in combination with a pressure-sensor-tipped guide wire, was evaluated in an in vitro coronary model. A continuous infusion thermodilution method was employed to determine the average flow, whereas a thermal anemometric method was utilized to assess the pressure and flow dynamics, simultaneously. In the latter method, the electrical power supplied to an element, kept at constant temperature above ambient temperature, was used as a measure for the shear rate. It was found that, using a single calibration function, the method was able to assess coronary pressure and flow dynamics for different flow amplitudes, heart rates, and different pressure wires. However, due to the fact that the thermal anemometric method cannot detect local shear rate reversal, the method was unable to reliably measure flow dynamics close to zero. Nevertheless, the combined methodology was able to reliably assess diastolic hemodynamics. The diastolic peak flow and average diastolic resistance could be determined with a small relative error of (8 ± 7)% and (7 ± 5)%, respectively.
Effect of temperature and pressure on the dynamics of nanoconfined propane
Gautam, Siddharth, E-mail: gautam.25@osu.edu; Liu, Tingting, E-mail: gautam.25@osu.edu; Welch, Susan; Cole, David [School of Earth Sciences, The Ohio State University, 275 Mendenhall Laboratory, 125 S Oval Mall, Columbus, OH 43210 (United States); Rother, Gernot [Geochemistry and Interfacial Science Group, Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Jalarvo, Niina [Jülich Center for Neutron Sciences (JCNS-1), Forschungszentrum Jülich Outstation at Spallation Neutron Source(SNS), Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Mamontov, Eugene [Spallation Neutron Source (SNS), Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)
2014-04-24
We report the effect of temperature and pressure on the dynamical properties of propane confined in nanoporous silica aerogel studied using quasielastic neutron scattering (QENS). Our results demonstrate that the effect of a change in the pressure dominates over the effect of temperature variation on the dynamics of propane nano-confined in silica aerogel. At low pressures, most of the propane molecules are strongly bound to the pore walls, only a small fraction is mobile. As the pressure is increased, the fraction of mobile molecules increases. A change in the mechanism of motion, from continuous diffusion at low pressures to jump diffusion at higher pressures has also been observed.
Geometry optimization for micro-pressure sensor considering dynamic interference.
Yu, Zhongliang; Zhao, Yulong; Li, Lili; Tian, Bian; Li, Cun
2014-09-01
Presented is the geometry optimization for piezoresistive absolute micro-pressure sensor. A figure of merit called the performance factor (PF) is defined as a quantitative index to describe the comprehensive performances of a sensor including sensitivity, resonant frequency, and acceleration interference. Three geometries are proposed through introducing islands and sensitive beams into typical flat diaphragm. The stress distributions of sensitive elements are analyzed by finite element method. Multivariate fittings based on ANSYS simulation results are performed to establish the equations about surface stress, deflection, and resonant frequency. Optimization by MATLAB is carried out to determine the dimensions of the geometries. Convex corner undercutting is evaluated. Each PF of the three geometries with the determined dimensions is calculated and compared. Silicon bulk micromachining is utilized to fabricate the prototypes of the sensors. The outputs of the sensors under both static and dynamic conditions are tested. Experimental results demonstrate the rationality of the defined performance factor and reveal that the geometry with quad islands presents the highest PF of 210.947 Hz(1/4). The favorable overall performances enable the sensor more suitable for altimetry.
Dynamic Sublimation Pressure and the Catastrophic Breakup of Comet ISON
Steckloff, Jordan K; Bowling, Timothy; Melosh, H Jay; Minton, David; Lisse, Carey M; Battams, Karl
2015-01-01
Previously proposed mechanisms have difficulty explaining the disruption of Comet C/2012 S1 (ISON) as it approached the Sun. We describe a novel cometary disruption mechanism whereby comet nuclei fragment and disperse through dynamic sublimation pressure, which induces differential stresses within the interior of the nucleus. When these differential stresses exceed its material strength, the nucleus breaks into fragments. We model the sublimation process thermodynamically and propose that it is responsible for the disruption of Comet ISON. We estimate the bulk unconfined crushing strength of Comet ISON's nucleus and the resulting fragments to be 0.5 Pa and 1-9 Pa respectively, assuming typical Jupiter Family Comet (JFC) albedos. However, if Comet ISON has an albedo similar to Pluto, this strength estimate drops to 0.2 Pa for the intact nucleus and 0.6-4 Pa for its fragments. Regardless of assumed albedo, these are similar to previous strength estimates of JFCs. This suggests that, if Comet ISON is representat...
Valenti, Davide; Denaro, Giovanni; Spagnolo, Bernardo; Conversano, Fabio; Brunet, Christophe
2015-01-01
During the last few years theoretical works have shed new light and proposed new hypotheses on the mechanisms which regulate the spatio-temporal behaviour of phytoplankton communities in marine pelagic ecosystems. Despite this, relevant physical and biological issues, such as effects of the time-dependent mixing in the upper layer, competition between groups, and dynamics of non-stationary deep chlorophyll maxima, are still open questions. In this work, we analyze the spatio-temporal behaviour of five phytoplankton populations in a real marine ecosystem by using a one-dimensional reaction-diffusion-taxis model. The study is performed, taking into account the seasonal variations of environmental variables, such as light intensity, thickness of upper mixed layer and profiles of vertical turbulent diffusivity, obtained starting from experimental findings. Theoretical distributions of phytoplankton cell concentration was converted in chlorophyll concentration, and compared with the experimental profiles measured in a site of the Tyrrhenian Sea at four different times (seasons) of the year, during four different oceanographic cruises. As a result we find a good agreement between theoretical and experimental distributions of chlorophyll concentration. In particular, theoretical results reveal that the seasonal changes of environmental variables play a key role in the phytoplankton distribution and determine the properties of the deep chlorophyll maximum. This study could be extended to other marine ecosystems to predict future changes in the phytoplankton biomass due to global warming, in view of devising strategies to prevent the decline of the primary production and the consequent decrease of fish species.
Metz, Johan A Jacob; Staňková, Kateřina; Johansson, Jacob
2016-03-01
This paper should be read as addendum to Dieckmann et al. (J Theor Biol 241:370-389, 2006) and Parvinen et al. (J Math Biol 67: 509-533, 2013). Our goal is, using little more than high-school calculus, to (1) exhibit the form of the canonical equation of adaptive dynamics for classical life history problems, where the examples in Dieckmann et al. (J Theor Biol 241:370-389, 2006) and Parvinen et al. (J Math Biol 67: 509-533, 2013) are chosen such that they avoid a number of the problems that one gets in this most relevant of applications, (2) derive the fitness gradient occurring in the CE from simple fitness return arguments, (3) show explicitly that setting said fitness gradient equal to zero results in the classical marginal value principle from evolutionary ecology, (4) show that the latter in turn is equivalent to Pontryagin's maximum principle, a well known equivalence that however in the literature is given either ex cathedra or is proven with more advanced tools, (5) connect the classical optimisation arguments of life history theory a little better to real biology (Mendelian populations with separate sexes subject to an environmental feedback loop), (6) make a minor improvement to the form of the CE for the examples in Dieckmann et al. and Parvinen et al.
The research of the maximum wind speed in Tomsk and calculations of dynamic load on antenna systems
Belan, B.; Belan, S.; Romanovskiy, O.; Girshtein, A.; Yanovich, A.; Baidali, S.; Terehov, S.
2017-01-01
The work is concerned with calculations and analysis of the maximum wind speed in Tomsk city. The data for analysis were taken from the TOR-station located in the north-eastern part of the city. The TOR-station sensors to measure a speed and a direction of wind are installed on the 10-meter meteorological mast. Wind is measured by M-63, which uses the standard approach and the program with one-minute averaging for wind gusts recording as well. According to the measured results in the research performed, the estimation of the dynamic and wind load on different types of antenna systems was performed. The work shows the calculations of wind load on ten types of antenna systems, distinguished by their different constructions and antenna areas. For implementation of calculations, we used methods developed in the Central Research and Development Institute of Building Constructions named after V.A. Kucherenko. The research results could be used for design engineering of the static antenna systems and mobile tracking systems for the distant objects.
Stokes, Chris R.; Tarasov, Lev; Dyke, Arthur S.
2012-09-01
The North American Ice Sheet Complex played a major role in global sea level fluctuations during the Late Quaternary but our knowledge of its dynamics is based mostly on its demise from the Last Glacial Maximum (LGM), a period characterised by non-linear behaviour in the form of punctuated ice margin recession, episodic ice streaming and major shifts in the location of ice divides. In comparison, knowledge of the pre-LGM ice complex is poorly constrained, largely because of the fragmentary nature of the evidence relating to ice sheet build-up. In this paper, we explore the inception and growth of ice (120-20 ka) using a glacial systems model which has been calibrated against a large and diverse set of data relating to the deglacial interval. We make use of calibration data prior to the LGM but its scarcity introduces greater uncertainty, which is partly alleviated by our large ensemble analysis. Results suggest that, following the last interglaciation (Oxygen Isotope Stage: OIS 5e), the ice complex initiated over the north-eastern Canadian Arctic and in the Cordillera within a few thousand years. It then underwent rapid growth to an OIS 5 maximum at ˜110 ka (5d) and covered ˜70% of the area occupied by the LGM ice cover (although only 30% by volume). An OIS 5 minimum is modelled at ˜80 ka (5a), before a second phase of rapid growth at the start of OIS 4, which culminated in a large ice complex at ˜65 ka (almost as large as at the LGM). Subsequent deglaciation was rapid (maximum modelled sea level contribution of >16 cm per century) and resulted in an OIS 3 minimum between ca 55-60 ka. Thereafter, the ice complex grew towards its LGM configuration, interrupted by several phases of successively less significant mass loss. Our results support and extend previous inferences based on geological evidence and reinforce the notion of a highly dynamic pre-LGM ice complex (e.g. with episodes of ±10 s m of eustatic sea level equivalent in ice increases towards the LGM
Disotell, Kevin J.; Nikoueeyan, Pourya; Naughton, Jonathan W.; Gregory, James W.
2016-05-01
Recognizing the need for global surface measurement techniques to characterize the time-varying, three-dimensional loading encountered on rotating wind turbine blades, fast-responding pressure-sensitive paint (PSP) has been evaluated for resolving unsteady aerodynamic effects in incompressible flow. Results of a study aimed at demonstrating the laser-based, single-shot PSP technique on a low Reynolds number wind turbine airfoil in static and dynamic stall are reported. PSP was applied to the suction side of a Delft DU97-W-300 airfoil (maximum thickness-to-chord ratio of 30 %) at a chord Reynolds number of 225,000 in the University of Wyoming open-return wind tunnel. Static and dynamic stall behaviors are presented using instantaneous and phase-averaged global pressure maps. In particular, a three-dimensional pressure topology driven by a stall cell pattern is detected near the maximum lift condition on the steady airfoil. Trends in the PSP-measured pressure topology on the steady airfoil were confirmed using surface oil visualization. The dynamic stall case was characterized by a sinusoidal pitching motion with mean angle of 15.7°, amplitude of 11.2°, and reduced frequency of 0.106 based on semichord. PSP images were acquired at selected phase positions, capturing the breakdown of nominally two-dimensional flow near lift stall, development of post-stall suction near the trailing edge, and a highly three-dimensional topology as the flow reattaches. Structural patterns in the surface pressure topologies are considered from the analysis of the individual PSP snapshots, enabled by a laser-based excitation system that achieves sufficient signal-to-noise ratio in the single-shot images. The PSP results are found to be in general agreement with observations about the steady and unsteady stall characteristics expected for the airfoil.
Dynamical Generation of a Repulsive Vector Contribution to the Quark Pressure
Restrepo, Tulio E; Pinto, Marcus Benghi; Ferrari, Gabriel N
2014-01-01
Lattice QCD results for the coefficient $c_2$ appearing in the Taylor expansion of the pressure show that this quantity raises with the temperature towards the Stefan-Boltzmann limit. On the other hand, model approximations predict that when a vector repulsion, parametrized by $G_V$, is present this coefficient reaches a maximum just after $T_c$ and then deviates from the lattice predictions. Recently, this discrepancy has been used as a guide to constrain the (presently unknown) value of $G_V$ within the framework of effective models at large-$N_c$ (LN). In the present investigation we show that, due to finite $N_c$ effects, $c_2$ may also develop a maximum even when $G_V=0$ since a vector repulsive term can be dynamically generated by exchange type of radiative corrections. Here we apply the the Optimized Perturbation Theory (OPT) method to the two flavor Polyakov--Nambu--Jona-Lasinio model (at $G_V=0$) and compare the results with those furnished by lattice simulations an by the LN approximation at $G_V=0$...
Martinez, N.
2016-09-06
Water and protein dynamics on a nanometer scale were measured by quasi-elastic neutron scattering in the piezophile archaeon Thermococcus barophilus and the closely related pressure-sensitive Thermococcus kodakarensis, at 0.1 and 40 MPa. We show that cells of the pressure sensitive organism exhibit higher intrinsic stability. Both the hydration water dynamics and the fast protein and lipid dynamics are reduced under pressure. In contrast, the proteome of T. barophilus is more pressure sensitive than that of T. kodakarensis. The diffusion coefficient of hydration water is reduced, while the fast protein and lipid dynamics are slightly enhanced with increasing pressure. These findings show that the coupling between hydration water and cellular constituents might not be simply a master-slave relationship. We propose that the high flexibility of the T. barophilus proteome associated with reduced hydration water may be the keys to the molecular adaptation of the cells to high hydrostatic pressure.
Martinez, N.; Michoud, G.; Cario, A.; Ollivier, J.; Franzetti, B.; Jebbar, M.; Oger, P.; Peters, J.
2016-09-01
Water and protein dynamics on a nanometer scale were measured by quasi-elastic neutron scattering in the piezophile archaeon Thermococcus barophilus and the closely related pressure-sensitive Thermococcus kodakarensis, at 0.1 and 40 MPa. We show that cells of the pressure sensitive organism exhibit higher intrinsic stability. Both the hydration water dynamics and the fast protein and lipid dynamics are reduced under pressure. In contrast, the proteome of T. barophilus is more pressure sensitive than that of T. kodakarensis. The diffusion coefficient of hydration water is reduced, while the fast protein and lipid dynamics are slightly enhanced with increasing pressure. These findings show that the coupling between hydration water and cellular constituents might not be simply a master-slave relationship. We propose that the high flexibility of the T. barophilus proteome associated with reduced hydration water may be the keys to the molecular adaptation of the cells to high hydrostatic pressure.
Dynamic Foot Pressure as a Countermeasure to Muscle Atrophy
Kyparos, A.; Layne, C. S.; Martinez, D. A.; Clarke, M. S. F.; Feeback, D. L.
2002-01-01
Mechanical unloading of skeletal muscle (SKM) as a consequence of space flight or ground-based analogues, such as human bedrest and rodent hindlimb suspension (HLS) models, induces SKM atrophy particularly affecting the anti-gravity musculature of the lower limbs. In the context of manned space flight, the subsequent loss of muscle strength and functionality will pose operational implications jeopardizing mission success. Exercise, currently the primary muscle degradation countermeasure, has not proven completely effective in preventing muscle atrophy. It is therefore imperative that some other forms of in- flight countermeasure be also developed to supplement the prescribed exercise regimen the astronauts follow during spaceflight. Previous work in both humans and rats has shown that mechanical stimulation of the soles of the feet increases neuromuscular activation in the lower limb musculature and that such stimulation results in the limited prevention of atrophy in the soleus muscle of unloaded rats. This study was designed to investigate the effect of cutaneous mechanoreceptor stimulation on hindlimb unloading- induced SKM atrophy in rats. It was hypothesized that mechanical stimulation of the plantar surface of the rat foot during hindlimb suspension (HLS), utilizing a novel stimulation paradigm known as Dynamic Foot Pressure (DFP), would attenuate unloading-induced SKM atrophy. Mature adult male Wistar rats were randomly assigned to four groups of 10 rats each as follows: sedentary controls (Ctrl), hindlimb suspended only (HLS), hindlimb suspended wearing an inflatable boot (HLS-IFL) and hindlimb suspended rats wearing a non-inflatable boot (HLS-NIFL). The stimulation of mechanoreceptors was achieved by applying pressure to the plantar surface of the foot during the 10-day period of HLS using a custom-built boot. The anti-atrophic effects of DFP application was quantified directly by morphological (muscle wet weight, myofiber cross-sectional area
Effect of change in large and fast solar wind dynamic pressure on geosynchronous magnetic field
Borodkova N L; Liu Jing-Bo; Huang Zhao-Hui; Zastenker G N; Wang Chi; Eiges P E
2006-01-01
We present a comparison of changes in large and sharp solar wind dynamic pressure, observed by several spacecraft,with fast disturbances in the magnetospheric magnetic field, measured by the geosynchronous satellites. More than 260 changes in solar wind pressure during the period 1996-2003 are selected for this study. Large statistics show that an increase (a decrease) in dynamic pressure always results in an increase (a decrease) in the magnitude of geosynchronous magnetic field. The amplitude of response to the geomagnetic field strongly depends on the location of observer relative to the noon meridian, the value of pressure before disturbance, and the change in amplitude of pressure.
Effect of the shape of mouth pressure variation on dynamic oscillation threshold of a clarinet model
Bergeot, Baptiste; Vergez, Christophe
2014-01-01
Simple models of clarinet instruments based on iterated maps have been used in the past to successfully estimate the threshold of oscillation of this instrument as a function of a constant blowing pressure. However, when the blowing pressure gradually increases through time, the oscillations appear at a much higher value, called dynamic oscillation threshold, than what is predicted in the static case. This is known as bifurcation delay, a phenomenon studied in [1,2] for a clarinet model. In particular the dynamic oscillation threshold is predicted analytically when the blowing pressure is linearly increased. However, the mouth pressure cannot grow indefinitely. During a note attack, after an increasing phase, the musician stabilizes the mouth pressure. In the present work, the analytical prediction of the dynamic oscillation threshold is extended to a situations in which the mouth pressure approaches a steady state pressure according to an exponential time profile. The predictions still show a good agreement ...
Change in blood pressure in recovery phase after combined (static & dynamic) exercise
桑村, 由美; 志内, 哲也; 野村, 千景; 幸田, 貴美子; 小原, 繁
1997-01-01
It is well known that systolic blood pressure (SBP) elevate but diastolic blood pressure (DBP) do not elevate during dynamic exercise and in statlc isometrlc exercise DBP show respectable elevation. However，changes in SBP and DBP in recovery phase after exercise is unclear.In this study we measured SBP and DBP by auscultatory recording method during recovery phase for 10 minutes. Resting blood pressure was determined immediately before exercise. The exercise was a dynamic (p...
Ab-initio molecular dynamics simulation on nano-system under external pressure
JI; Min; SUN; Deyan; GONG; Xingao
2004-01-01
A new constant-pressure molecular dynamics (MD) method is developed to simulate the dynamic behavior and structure transition of finite system under external pressure. In this method, no artificial parameter is introduced and the computation overheads are very small. As an application, a hard-soft transition of single wall carbon nanotube (SWCNT) under external pressure is found, which is in agreement with the experiments.
R.Nagendra Babu
2010-08-01
Full Text Available Geometric discontinuities cause a large variation of stress and produce a significant increase in stress. The high stress due to the variation of geometry is called as ‘stress concentration’. This will increase when the loads are further applied. There are many investigators who have studied the stress distribution around the notches, grooves, and other irregularities of various machine components. This paper analyses the effects of thermal and fatigue load on a steam turbine rotor under the operating conditions. Stresses due to thermal and dynamic loads of High Pressure Steam Turbine Rotor of 210MW power station are found in two stages. A source code is developed for calculating the nominal stress at each section of HPT rotor. Maximum stress is obtained using FEA at the corresponding section. Thermal and Fatigue Stress Concentration Factors at each section are calculated. It is observed that the SCFdue to the combined effect of thermal and dynamic loads at the temperatures beyond 5400C is exceeding the safe limits.
A new dynamic method for measuring hydrogen partial pressure in molten aluminum alloy
Sun Qian
2011-02-01
Full Text Available Hydrogen partial pressure is an important parameter to calculate hydrogen concentration levels in molten aluminum alloy. A new dynamic method for measuring hydrogen partial pressure in molten aluminum alloy is studied. Dynamic and rapid measurement is realized through changing the volume of the vacuum chamber and calculating the pressure difference ΔP between the theoretical and measured pressures in the vacuum chamber. Positive ΔP indicates hydrogen transmits from melt to vacuum chamber and negative ΔP means the reverse. When ΔP is equal to zero, hydrogen transmitted from both sides reached a state of dynamical equilibrium and the pressure in the vacuum chamber is equal to the hydrogen partial pressure in the molten aluminum alloy. Compared with other existing measuring methods, the new method can significantly shorten the testing time and reduce measuring cost.
Novel Method for Processing the Dynamic Calibration Signal of Pressure Sensor
Zhongyu Wang
2015-07-01
Full Text Available Dynamic calibration is one of the important ways to acquire the dynamic performance parameters of a pressure sensor. This research focuses on the processing method for the output of calibrated pressure sensor, and mainly attempts to solve the problem of extracting the true information of step response under strong interference noise. A dynamic calibration system based on a shock tube is established to excite the time-domain response signal of a calibrated pressure sensor. A key processing on difference modeling is applied for the obtained signal, and several generating sequences are established. A fusion process for the generating sequences is then undertaken, and the true information of the step response of the calibrated pressure sensor can be obtained. Finally, by implementing the common QR decomposition method to deal with the true information, a dynamic model characterizing the dynamic performance of the calibrated pressure sensor is established. A typical pressure sensor was used to perform calibration tests and a frequency-domain experiment for the sensor was also conducted. Results show that the proposed method could effectively filter strong interference noise in the output of the sensor and the corresponding dynamic model could effectively characterize the dynamic performance of the pressure sensor.
Novel Method for Processing the Dynamic Calibration Signal of Pressure Sensor.
Wang, Zhongyu; Li, Qiang; Wang, Zhuoran; Yan, Hu
2015-07-21
Dynamic calibration is one of the important ways to acquire the dynamic performance parameters of a pressure sensor. This research focuses on the processing method for the output of calibrated pressure sensor, and mainly attempts to solve the problem of extracting the true information of step response under strong interference noise. A dynamic calibration system based on a shock tube is established to excite the time-domain response signal of a calibrated pressure sensor. A key processing on difference modeling is applied for the obtained signal, and several generating sequences are established. A fusion process for the generating sequences is then undertaken, and the true information of the step response of the calibrated pressure sensor can be obtained. Finally, by implementing the common QR decomposition method to deal with the true information, a dynamic model characterizing the dynamic performance of the calibrated pressure sensor is established. A typical pressure sensor was used to perform calibration tests and a frequency-domain experiment for the sensor was also conducted. Results show that the proposed method could effectively filter strong interference noise in the output of the sensor and the corresponding dynamic model could effectively characterize the dynamic performance of the pressure sensor.
The correlations of ions density with geomagnetic activity and solar dynamic pressure in cusp region
GUO JianGuang; SHI JianKui; ZHANG TieLong; LIU ZhenXing; A. FAZAKERLEY; H. R(E)ME; Ⅰ. DANDOURAS; E. LUCEK
2007-01-01
A statistical study of the properties of ions (O+, He+ and H+) measured by the Cluster-Ⅱ in cusp region as a function of the solar wind dynamic pressure and geomagnetic index Kp respectively was made during the summer and fall of 2001 -2003. The main results are that: (1) O+ ion density responds in a significant way to geomagnetic index Kp, and He+ ion density is not correlated with geomagnetic index Kp,both of them have a significant positive correlation with solar wind dynamic pressure; (2) H+ ion density is also observed to increase with solar wind dynamic pressure, and not correlated with geomagnetic index Kp.
Dynamical analysis of high-pressure supercritical carbon dioxide jet in well drilling
DU Yu-kun; WANG Rui-he; NI Hong-jian; HUANG Zhi-yuan; LI Mu-kun
2013-01-01
This paper presents the design of an experimental setup and mathematical and physical models to determine the dynamical characteristics of the high-pressure supercritical carbon dioxide (SC-CO2) jet with a highly potential applications in the well drilling.The effects of three major factors on the wellbore dynamical characteristics of the high-pressure SC-CO2 jet,i.e.,the nozzle diameter,the standoff distance and the jet pressure are determined.It is indicated that the pressure of CO2 reduces severely in the SC-CO2 jet impact process.It is also found that the bottom-hole pressure and the temperature increase as the nozzle diameter increases but decrease with the increase of the standoff distance.The higher the jet pressure at the wellbore inlet is,the higher the pressure and the lower the temperature at the bottom-hole will be.
High Speed Pressure Sensitive Paint for Dynamic Testing
Pena, Carolina; Chism, Kyle; Hubner, Paul
2016-11-01
Pressure sensitive paint (PSP) allows engineers to obtain accurate, high-spatial-resolution measurements of pressure fields over a structure. The pressure is directly related to the luminescence emitted by the paint due to oxygen quenching. Fast PSP has a higher surface area due to its porosity compared to conventional PSP, which enables faster diffusion and measurements to be acquired three orders of magnitude faster than with conventional PSP. A fast time response is needed when testing vibrating structures due to fluid-structure interaction. The goal of this summer project was to set-up, test and analyze the pressure field of an impinging air jet on a vibrating cantilever beam using Fast PSP. Software routines were developed for the processing of the emission images, videos of a static beam coated with Fast PSP were acquired with the air jet on and off, and the intensities of these two cases were ratioed and calibrated to pressure. Going forward, unsteady pressures on a vibrating beam will be measured and presented. Eventually, the long-term goal is to integrate luminescent pressure and strain measurement techniques, simultaneously using Fast PSP and a luminescent photoelastic coating on vibrating structures. Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.
Bergeot, Baptiste; Vergez, Christophe; Gazengel, Bruno
2012-01-01
Reed instruments are modeled as self-sustained oscillators driven by the pressure inside the mouth of the musician. A set of nonlinear equations connects the control parameters (mouth pressure, lip force) to the system output, hereby considered as the mouthpiece pressure. Clarinets can then be studied as dynamical systems, their steady behavior being dictated uniquely by the values of the control parameters. Considering the resonator as a lossless straight cylinder is a dramatic yet common simplification that allows for simulations using nonlinear iterative maps. In this paper, we investigate analytically the effect of a time-varying blowing pressure on the behavior of this simplified clarinet model. When the control parameter varies, results from the so-called dynamic bifurcation theory are required to properly analyze the system. This study highlights the phenomenon of bifurcation delay and defines a new quantity, the dynamic oscillation threshold. A theoretical estimation of the dynamic oscillation thresho...
Camps-Roach, Geremy; O'Carroll, Denis M.; Newson, Timothy A.; Sakaki, Toshihiro; Illangasekare, Tissa H.
2010-08-01
The macroscopic flow equations used to predict two-phase flow typically utilizes a capillary pressure-saturation relationship determined under equilibrium conditions. Theoretical reasoning, experimental evidence, and numerical modeling results have indicated that when one fluid phase replaces another fluid, this relationship may not be unique but may depend on the rate at which the phase saturations change in response to changes in phase pressures. This nonuniqueness likely depends on a variety of factors including soil-fluid properties and possibly physical scale. To quantify this dependency experimentally, direct measurements of equilibrium and dynamic capillary pressure-saturation relationships were developed for two Ottawa sands with different grain sizes using a 20 cm long column. A number of replicate air-water experiments were conducted to facilitate statistical comparison of capillary pressure-saturation relationships. Water and air pressures and phase saturations were measured at three different vertical locations in the sand column under different desaturation rates (1) to measure local capillary pressure-saturation relationships (static and dynamic); (2) to quantify the dynamic coefficient τ, a measure of the magnitude of observed dynamic effects, as a function of water saturation for different grain sizes and desaturation rates; (3) to investigate the importance of grain size on measured dynamic effects; and (4) to assess the importance of sample scale on the magnitude of dynamic effects in capillary pressure. A comparison of the static and dynamic Pc-Sw relationships showed that at a given water saturation, capillary pressure measured under transient water drainage conditions is statistically larger than capillary pressure measured under equilibrium or static conditions, consistent with thermodynamic theory. The dynamic coefficient τ, used in the expression relating the static and dynamic capillary pressures to the desaturation rate was dependant on
Simulation Study of AC Contactor Dynamic Contacts Contact Pressure Based on ADAMS
Gu Yungao
2015-01-01
Full Text Available A multi-body dynamics simulation model of CJ20-25 AC contactor was established with Pro/E（Pro/Engineerin this paper. A coupling simulation with machine, electric, magnetic on the contactor has been achieved in this model. Dynamic parameters which were called use the secondary development technology of ADAMS. The dynamic contact pressure signal of an AC contactor was obtained with ADAMS’s own simultaneous solution such as electromagnetic suction, kinematics and dynamics equations. The simulation results and actual measurement of contactor contact pressure signals are very similar. However, the complexity of the measured contacts vibration is greater than the simulation results because the actual working condition is more complex. This result provides a theoretical foundation to the dynamic contacts contact pressure test.
Anisotropic pressure molecular dynamics for atomic fluid systems
Romero-Bastida, M [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Avenida Universidad 1001, Chamilpa, Cuernavaca, Morelos 62209 (Mexico); Lopez-Rendon, R [Departamento de QuImica, Universidad Autonoma Metropolitana-Iztapalapa, Av San Rafael Atlixco 186, 09340 Mexico DF (Mexico)
2007-07-20
The MTK equations (Martyna G J, Tobias D J and Klein M L 1994 J. Chem. Phys. 101 4177-89), which simulate the constant-pressure, constant-temperature NPT ensemble, have been modified to simulate an anisotropic pressure along a single coordinate axis, thus rendering the NP{sub zz}T ensemble. The necessary theory of non-Hamiltonian systems is briefly reviewed in order to analytically prove that the proposed equations indeed sample the desired ensemble. A previously derived geometric integrator for the MTK equations is modified to take into account the anisotropic pressure and volume fluctuations. We choose a Lennard-Jones fluid as an illustrative example. The density distribution function, as well as various thermodynamic and interfacial properties of the model system in a liquid-vapour coexistence state, was computed to test the robustness of the proposed equations of motion to simulate the NP{sub zz}T ensemble.
Static and dynamic tensile behaviour of aluminium processed by high pressure torsion
Verleysen, P.; Oelbrandt, W.; Naghdy, S.; Kestens, L.
2015-01-01
High pressure torsion (HPT) is a severe plastic deformation technique in which a small, disk-like sample is subjected to a torsional deformation under a high hydrostatic pressure. In present study, the static and dynamic tensile behaviour of commercially pure aluminium (99.6 wt%) processed by HPT is
Comparison of Iterative Methods for Computing the Pressure Field in a Dynamic Network Model
Mogensen, Kristian; Stenby, Erling Halfdan; Banerjee, Srilekha
1999-01-01
In dynamic network models, the pressure map (the pressure in the pores) must be evaluated at each time step. This calculation involves the solution of a large number of nonlinear algebraic systems of equations and accounts for more than 80 of the total CPU-time. Each nonlinear system requires...
Changes in Land Surface Water Dynamics since the 1990s and Relation to Population Pressure
Prigent, C.; Papa, F.; Aires, F.; Jimenez, C.; Rossow, W. B.; Matthews, E.
2012-01-01
We developed a remote sensing approach based on multi-satellite observations, which provides an unprecedented estimate of monthly distribution and area of land-surface open water over the whole globe. Results for 1993 to 2007 exhibit a large seasonal and inter-annual variability of the inundation extent with an overall decline in global average maximum inundated area of 6% during the fifteen-year period, primarily in tropical and subtropical South America and South Asia. The largest declines of open water are found where large increases in population have occurred over the last two decades, suggesting a global scale effect of human activities on continental surface freshwater: denser population can impact local hydrology by reducing freshwater extent, by draining marshes and wetlands, and by increasing water withdrawals. Citation: Prigent, C., F. Papa, F. Aires, C. Jimenez, W. B. Rossow, and E. Matthews (2012), Changes in land surface water dynamics since the 1990s and relation to population pressure, in section 4, insisting on the potential applications of the wetland dataset.
Dynamics in the vicinity of (101955) Bennu: solar radiation pressure effects in equatorial orbits
Chanut, T. G. G.; Aljbaae, S.; Prado, A. F. B. A.; Carruba, V.
2017-09-01
Here, we study the dynamical effects of the solar radiation pressure (SRP) on a spacecraft that will survey the near-Earth rotating asteroid (101955) Bennu when the projected shadow is accounted for. The spacecraft's motion near (101955) Bennu is modelled in the rotating frame fixed at the centre of the asteroid, neglecting the Sun gravity effects. We calculate the SRP at the perihelion, semimajor axis and aphelion distances of the asteroid from the Sun. The goals of this work are to analyse the stability for both homogeneous and inhomogeneous mass distribution and study the effects of the SRP in equatorial orbits close to the asteroid (101955) Bennu. As results, we find that the mascon model divided into 10 equal layers seems to be the most suitable for this problem. We can highlight that the centre point E8, which was linearly stable in the case of the homogeneous mass distribution, becomes unstable in this new model changing its topological structure. For a Sun initial longitude ψ0 = -180°, starting with the spacecraft longitude λ = 0, the orbits suffer fewer impacts and some (between 0.4 and 0.5 km), remaining unwavering even if the maximum solar radiation is considered. When we change the initial longitude of the Sun to ψ0 = -135°, the orbits with initial longitude λ = 90° appear to be more stable. Finally, when the passage of the spacecraft in the shadow is accounted for, the effects of SRP are softened, and we find more stable orbits.
Pan Hao
2015-01-01
Full Text Available Dynamic yield strength of metals/alloys depends on loading pressure and rates sensitively. With the development of laser interferometer measurement system, extracting strength information from window/free surface velocity profiles in shock and ramp loading experiments is becoming an important method to investigate materials’ dynamic response under high pressure and high strain rates. Backwards characteristics analysis method (BCAM can analyze the velocity profiles more reasonable because it accounts for bending of the incoming characteristics due to impedance mismatch between the sample and window. Synthetic analyses of reverse impact experiment and graded-density impactor loading-releasing experiment suggest that BCAM can give more accurate results including sound speed-particle velocity and yield strength at high pressure than incremental impedance matching method. We use BCAM to analyze velocity profiles of Sn in shock-release experiments and obtain its shear modulus and yield strength at different shock pressure and investigate its phase transition and dynamic unloading response.
Rizzoni, G. (Michigan Univ., Ann Arbor, MI (USA). Dept. of Electrical Engineering and Computer Science)
1989-08-01
In-cylinder gas pressure has long been recognized as a fundamental measure of performance in the internal combustion engine. Among the issues that have been the subject of research in recent years is the study of the effects cyclic combustion variability has on the cycle-to-cycle and cylinder-to-cylinder fluctuations in combustion pressures. Some of the research problems pertaining to cyclic combustion variability are to reformulate from a perspective markedly different from the fluid dynamic and thermodynamic models which traditionally characterize this research: a system viewpoint is embraced to construct a stochastic model for the indicated pressure process and the dynamics of the internal combustion engine. First a deterministic model for the dynamics of the engine is described; then a stochastic model is proposed for the cylinder pressure process. The deterministic model and the stochastic representation are then tied together in a Kalman filter model. Experimental results are discussed to validate the models.
Dynamic Pressure of Seabed around Buried Pipelines in Shallow Water
Changjing Fu; Guoying Li; Tianlong Zhao; Donghai Guan
2015-01-01
Due to the obvious nonlinear effect caused by the shallow waves, the nonlinear wave loads have a great influence on the buried pipelines in shallow water. In order to ensure their stability, the forces on the pipelines that resulted from nonlinear waves should be considered thoroughly. Based on the Biot consolidation theory and the first-order approximate cnoidal wave theory, analytical solutions of the pore water pressure around the buried pipelines in shallow water caused by waves are first...
Analysis of pressure wave dynamics in fuel rail system
B Alzahabi
2008-09-01
Full Text Available A model of an amplified common rail fuel system is simulated in Matlab toanalyze the wave mechanics in the rail. The injectors are modeled as asystem of linear and non-linear ODE’s consisting of masses, a helical spring,compressibility effects from fluid volumes, and hydraulic flow throughorifices. The injector simulation then predicts the rate of oil consumption,which is then input into the rail model.The rail is modeled in three sections which are coupled together. The pointswhere the coupling occurs are the locations where the current firinginjector and the pump supply are connected to the rail. This allows themodel to control the pressure and velocity (as boundary conditions atthese points. The rail model is based on the 1D, undamped wave equation,in a non-dimensional form [1] (in the position variable, x. The Reduction ofOrder method was used to solve the wave equation with the Matlabfunction PDEPE.The model was run with two different sets of initial conditions - nominal(constant pressure and zero velocity, and worst case using a simplifiedrepresentation of the pressure and velocity distribution at start of injection.This was done to determine the effect of rail waves at the start of injection,on the output of the model. The variation in fuel delivery, due to the variationin rail pressure, was then evaluated at three operating conditions - Idle,Peak Torque (PT and High Speed Light Load (HSLL. The simulation outputis then compared to analytical solutions of two forms of simplifiedgeometry, using the product method to solve the system [1.
Dibbern, Andreas; Crisafulli, Jeffrey; Hagopia, Michael; McDougle, Stephen H.; Saulsberry, Regor L.
2009-01-01
Accurate dynamic pressure measurements are often difficult to make within small pyrotechnic devices, and transducer mounting difficulties can cause data anomalies that lead to erroneous conclusions. Delayed initial pressure response followed by data ringing has been observed when using miniaturized pressure transducer mounting adapters required to interface transducers to small test chambers. This delayed pressure response and ringing, combined with a high data acquisition rate, has complicated data analysis. This paper compares the output signal characteristics from different pressure transducer mounting options, where the passage distance from the transducer face to the pyrotechnic chamber is varied in length and diameter. By analyzing the data and understating the associated system dynamics, a more realistic understanding of the actual dynamic pressure variations is achieved. Three pressure transducer mounting configurations (elongated, standard, and face/flush mount) were simultaneously tested using NASA standard initiators in closed volume pressure bombs. This paper also presents results of these pressure transducer mounting configurations as a result of a larger NASA Engineering and Safety Center pyrovalve test project. Results from these tests indicate the improved performance of using face/flush mounted pressure transducers in this application. This type of mounting improved initial pressure measurement response time by approximately 19 s over standard adapter mounting, eliminating most of the lag time; provided a near step-function type initial pressure increase; and greatly reduced data ringing in high data acquisition rate systems. The paper goes on to discuss other issues associated with the firing and instrumentation that are important for the tester to understand.
Conversion of Dynamic High Pressures from Air to Water for a Spherical TNT Charge
A. K. Sharma
1996-01-01
Full Text Available A numerical method has been applied to convert the dynamic high pressures from air-to-water for a spherical TNT charge. Standard equation of scaling law in air for TNT has been utilised to make the necessary conversions. The investigations have been made by taking into consideration the ambient pressure values for the two media. The calculations have been performed under the scaled distances to get better results. Experimental measurements using indigenous blast pressure gauge have been undertaken by detonating spherical charges of TNT under the same scaled distances in water to check the correctness of results and direct application of this method. A fairly close agreement between the theoretically computed and the experimental values of the dynamic high pressures shows the practical utility of this approach in that it enables an estimate of the experimental shock wave pressures, without conducting underwater experiments.
Analysis and numerical simulation of dynamic effect on rock under high pressure water jet
LI Xiao-hong; SI Hu; WANG Dan-dan
2008-01-01
Based on continuum mechanics and rock dynamics, analyzed the micro-structure damage of rock and the impulsive effect under high pressure water jet and developed the dynamic model. Further, on the assumption of that rock was homogeneous and isotropic, a computational model was established based on nonlinear finite element and Arbitrary Lagrangian-Eulerian(ALE) method. The dynamic effect impacted on rock under high pressure water jet was simulated by the dynamic contact method. The propagation of stress wave in rock was numerically simulated at different impacting velocity. The results show that the propagation velocity of stress wave is proportional to the impacting velocity of high pressure water jet. The faster the impacting velocity is, the quicker the comedown of stress wave.
Pressure-produced ionization of nonideal plasma in a megabar range of dynamic pressures
Fortov, VE; Ternovoi, VY; Zhernokletov, MV; Mochalov, MA; Mikhailov, AL; Filimonov, AS; Pyalling, AA; Mintsev, VB; Gryaznov, VK; Iosilevskii, IL
2003-01-01
The low-frequency electrical conductivity of strongly nonideal hydrogen, helium, and xenon plasmas was measured in the megabar range of pressures. The plasmas in question were generated by the method of multiple shock compression in planar and cylindrical geometries, whereby it was possible to reduc
The dynamic pressure response to rapid dilatation of the resting urethra in healthy women
Bagi, P; Thind, P; Colstrup, H;
1993-01-01
beta e-t/tau beta, where Pequ, P alpha and P beta are constants, and tau alpha and tau beta are time constants; this equation has previously been demonstrated to describe the pressure decay following dilatation. On the basis of a theoretical model the elastic and viscous constants for the urethral...... tissues were computed. The results showed significant differences along the urethra, with the high-pressure zone showing the highest maximum and equilibrium pressures, fastest pressure decay and highest elastic coefficient. The pressure response represents an integrated stress response from...... the surrounding structures, which reflects the visco-elastic properties of the tissues involved. The findings seem therefore to correlate well with the anatomical findings, which have shown a high fibre density of the horseshoe-shaped rhabdosphincter in the mid-portion of the urethra. The method permits...
Kinkhabwala, Ali
2013-01-01
The most fundamental problem in statistics is the inference of an unknown probability distribution from a finite number of samples. For a specific observed data set, answers to the following questions would be desirable: (1) Estimation: Which candidate distribution provides the best fit to the observed data?, (2) Goodness-of-fit: How concordant is this distribution with the observed data?, and (3) Uncertainty: How concordant are other candidate distributions with the observed data? A simple unified approach for univariate data that addresses these traditionally distinct statistical notions is presented called "maximum fidelity". Maximum fidelity is a strict frequentist approach that is fundamentally based on model concordance with the observed data. The fidelity statistic is a general information measure based on the coordinate-independent cumulative distribution and critical yet previously neglected symmetry considerations. An approximation for the null distribution of the fidelity allows its direct conversi...
Dynamic effects of high-pressure pulsed water jet in low-permeability coal seams
LI Xiao-hong; ZHOU Dong-ping; LU Yi-yu; KANG Yong; ZHAO Yu; WANG Xiao-chuan
2009-01-01
Mine gas extraction in China is difficult due to the characteristics such as mi-cro-porosity, low-permeability and high adsorption of coal seams. The pulsed mechanism of a high-pressure pulsed water jet was studied through theoretical analysis, experiment and field measurement. The results show that high-pressure pulsed water jet has three dynamic properties. What's more, the three dynamic effects can be found in low-perme-ability coal seams. A new pulsed water jet with 200-1 000 Hz oscillation frequency and peak pressure 2.5 times than average pressure was introduced. During bubble collapsing, sound vibration and instantaneous high pressures over 100 MPa enhanced the cutting ability of the high-pressure jet. Through high-pressure pulsed water jet drilling and slotting, the exposure area of coal bodies was greatly enlarged and pressure of the coal seams rapidly decreased. Therefore, the permeability of coal seams was improved and gas ab-sorption rate also decreased. Application results show that gas adsorption rate decreased by 30%-40% and the penetrability coefficient increased 100 times. This proves that high-pressure pulsed water is more efficient than other conventional methods.
Dynamic response of vaporizing droplet to pressure oscillation
Yuan, Lei; Shen, Chibing; Zhang, Xinqiao
2017-02-01
Combustion instability is a major challenge in the development of the liquid propellant engines, and droplet vaporization is viewed as a potential mechanism for driving instabilities. Based on the previous work, an unsteady droplet heating and vaporization model was developed. The model and numerical method are validated by experimental data available in literature, and then the oscillatory vaporization of n-Heptane droplet exposed to unsteady harmonic nitrogen atmosphere was numerically investigated over a wide range of amplitudes and frequencies. Also, temperature variations inside the droplet were demonstrated under oscillation environments. It was found that the thermal wave is attenuated with significantly reduced wave intensities as it penetrates deep into droplet from the ambient gas. Droplet surface temperature exhibits smaller fluctuation than that of the ambient gas, and it exhibits a time lag with regard to the pressure variation. Furthermore, the mechanism leading to phase lag of vaporization rate with respect to pressure oscillation was unraveled. Results show that this phase lag varies during the droplet lifetime and it is strongly influenced by oscillation frequency, indicating droplet vaporization is only capable of driving combustion instability in some certain frequency domains. Instead, the amplitude of the oscillation does not have very significant effects. It is noteworthy that thermal inertia of the droplet also plays a considerable role in determining the phase lag.
Nathália Reis
2013-05-01
Full Text Available PURPOSE: To evaluate and correlate the amplitude of esophageal contractions triggered by swallowing water with dynamic extension and habitual, strong and weak sound intensity in total laryngectomees wearing a tracheoesophageal prosthesis. METHODS: Thirty total laryngectomees using tracheoesophageal voice with a phonatory prosthesis were evaluated by measuring the amplitude of contractions in the proximal, middle and distal esophagus and the pressure of the pharyngoesophageal transition by manometry. In order to measure vocal intensity the subject was asked to emit phonation of the vowel /a/ at habitual, strong and weak intensity which was captured with a sound pressure meter. Dynamic extension was calculated by subtracting strong intensity from weak intensity. RESULTS: A positive correlation was observed between contraction amplitude and dynamic extension in the proximal (rho: 0.45; p=0.01 and distal (rho: 0.41; p=0.02 esophagus There was no correlation with other parameters.. Total laryngectomees wearing a phonatory prosthesis with a dynamic extension above 21 dBNPS had greater contraction amplitude than laryngectomees with a dynamic extension below this value. CONCLUSIONS: There was a positive correlation between pressure amplitude in the proximal and distal esophagus and increased dynamic extension. The individuals with normal dynamic extension had greater contraction amplitude in the proximal esophagus than individuals with dynamic extension lower than the expected values for age.
无
2006-01-01
In order to clarify the damage mechanism of the subway structure, the dynamic soil-structure interaction and the dynamic forces acting on the structure, a series of shaking table tests and simulation analyses were performed. The seismic response of the structure and the dynamic forces acting on the structure due to sinusoidal and random waves were investigated with special attention to the dynamic soil-structure interaction. The result shows that the compression seismic soil pressures and extension seismic soil pressures simultaneously act on the sidewalls, and big shear stress also acts on the ceiling slab due to horizontal excitation. The seismic soil pressure could be approximated to hyperbola curve, and reached a peak value with increase of the shear strain of the model ground. In addition, a slide and exfoliation phenomenon between the structure and the surrounding ground was simulated, using the nonlinear analyses. The foundation is provided for amending the calculation method of seismic soil pressure and improving the anti-earthquake designing level of underground structure.
COMPUTATIONAL FLUID DYNAMICS RESEARCH ON PRESSURE LOSS OF CROSS-FLOW PERFORATED MUFFLER
HU Xiaodong; ZHOU Yiqi; FANG Jianhua; MAN Xiliang; ZHAO Zhengxu
2007-01-01
The pressure loss of cross-flow perforated muffler has been computed with the procedure of physical modeling, simulation and data processing. Three-dimensional computational fluid dynamics (CFD) has been used to investigate the relations of porosities, flow velocity and diameter of the holes with the pressure loss. Accordingly, some preliminary results have been obtained that pressure loss increases with porosity descent as nearly a hyperbolic trend, rising flow velocity of the input makes the pressure loss increasing with parabola trend, diameter of holes affects little about pressure loss of the muffler. Otherwise, the holes on the perforated pipes make the air flow gently and meanly,which decreases the air impact to the wall and pipes in the muffler. A practical perforated muffler is used to illustrate the available of this method for pressure loss computation, and the comparison shows that the computation results with the method of CFD has reference value for muffler design.
Local Dynamical Instabilities in Magnetized, Radiation Pressure Supported Accretion Disks
Blaes, Omer M; Blaes, Omer; Socrates, Aristotle
2000-01-01
We present a general linear dispersion relation which describes the coupled behavior of magnetorotational, photon bubble, and convective instabilities in weakly magnetized, differentially rotating accretion disks. We presume the accretion disks to be geometrically thin and supported vertically by radiation pressure. We fully incorporate the effects of a nonzero radiative diffusion length on the linear modes. In an equilibrium with purely vertical magnetic field, the vertical magnetorotational modes are completely unaffected by compressibility, stratification, and radiative diffusion. However, in the presence of azimuthal fields, which are expected in differentially rotating flows, the growth rate of all magnetorotational modes can be reduced substantially below the orbital frequency. This occurs if diffusion destroys radiation sound waves on the length scale of the instability, and the magnetic energy density of the azimuthal component exceeds the non-radiative thermal energy density. While sluggish in this c...
Kimmel, David G.; McGlaughon, Benjamin D.; Leonard, Jeremy; Paerl, Hans W.; Taylor, J. Christopher; Cira, Emily K.; Wetz, Michael S.
2015-05-01
Estuaries often have distinct zones of high chlorophyll a concentrations, known as chlorophyll maximum (CMAX). The persistence of these features is often attributed to physical (mixing and light availability) and chemical (nutrient availability) features, but the role of mesozooplankton grazing is rarely explored. We measured the spatial and temporal variability of the CMAX and mesozooplankton community in the eutrophic Neuse River Estuary, North Carolina. We also conducted grazing experiments to determine the relative impact of mesozooplankton grazing on the CMAX during the phytoplankton growing season (spring through late summer). The CMAX was consistently located upriver of the zone of maximum zooplankton abundance, with an average spatial separation of 18 km. Grazing experiments in the CMAX region revealed negligible effect of mesozooplankton on chlorophyll a during March, and no effect during June or August. These results suggest that the spatial separation of the peak in chlorophyll a concentration and mesozooplankton abundance results in minimal impact of mesozooplankton grazing, contributing to persistence of the CMAX for prolonged time periods. In the Neuse River Estuary, the low mesozooplankton abundance in the CMAX region is attributed to lack of a low salinity tolerant species, predation by the ctenophore Mnemiopsis leidyi, and/or physiologic impacts on mesozooplankton growth rates due to temperature (in the case of low wintertime abundances). The consequences of this lack of overlap result in exacerbation of the effects of eutrophication; namely a lack of trophic transfer to mesozooplankton in this region and the sinking of phytodetritus to the benthos that fuels hypoxia.
Dan N. Dumitriu
2015-09-01
Full Text Available A Danaher Thomson linear actuator with ball screw drive and a realtime control system are used here to induce vertical displacements under the driver/user seat of an in-house dynamic car simulator. In order to better support the car simulator and to dynamically protect the actuator’s ball screw drive, a layer of coil springs is used to support the whole simulator chassis. More precisely, one coil spring is placed vertically under each corner of the rectangular chassis. The paper presents the choice of the appropriate coil springs, so that to minimize as much as possible the ball screw drive task of generating linear motions, corresponding to the vertical displacements and accelerations encountered by a driver during a real ride. For this application, coil springs with lower spring constant are more suited to reduce the forces in the ball screw drive and thus to increase the ball screw drive life expectancy.
1990-12-01
34pyro-", "piezo-" means "to press" in the Greek language and the piezoelectric effect is caused by applying pressure to the material. In 1881, the...LINKING THE BASIC * 180 ’CALL COMMANDS TO THE QUATECH MACHINE LANGUAGE 1 9 0 200 ADC.SETUP=&H3:SETCTM=&H6 210 SETC0=&H9 220 INADC12.B=&HC:SEGADDR...H3CA)+256*PEEK(&H3CB) 270 DEF SEG=CSEG2 280 GOSUB 330 ’QUATECH BOARD SETUP 290 GOSUB 860 ’DATA FILE SETUP 300 GOSUB 1010 ’ AQUIRE DATA 310 320 END 330
Jian Zhao
2017-01-01
Full Text Available Partial shading (PS is an unavoidable condition which significantly reduces the efficiency and stability of a photovoltaic (PV system. With PS, the system usually exhibits multiple-peak output power characteristics, but single-peak is also possible under special PS conditions. In fact it is shown that the partial shading condition (PSC is the necessary but not sufficient condition for multiple-peak. Based on circuit analysis, this paper shows that the number of peak points can be determined by short-circuit currents and maximum-power point currents of all the arrays in series. Then the principle is established based on which the number of the peak points is to be determined. Furthermore, based on the dynamic characteristic of solar array, this paper establishes the rule for determination of the relative position of the global maximum power point (GMPP. In order to track the GMPP within an appropriate period, a reliable technique and the corresponding computer algorithm are developed for GMPP tracking (GMPPT control. It exploits a definable nonlinear relation has been found between variable environmental parameters and the output current of solar arrays at every maximum power point, obtained based on the dynamic performance corresponding to PSC. Finally, the proposed method is validated with MATLAB®/Simulink® simulations and actual experiments. It is shown that the GMPPT of a PV generation system is indeed realized efficiently in a realistic environment with partial shading conditions.
Teng, Lei; Zhang, Hongying; Dong, Yongkang; Zhou, Dengwang; Jiang, Taofei; Gao, Wei; Lu, Zhiwei; Chen, Liang; Bao, Xiaoyi
2016-09-15
A temperature-compensated distributed hydrostatic pressure sensor based on Brillouin dynamic gratings (BDGs) is proposed and demonstrated experimentally for the first time, to the best of our knowledge. The principle is to measure the hydrostatic pressure induced birefringence changes through exciting and probing the BDGs in a thin-diameter pure silica polarization-maintaining photonic crystal fiber. The temperature cross-talk to the hydrostatic pressure sensing can be compensated through measuring the temperature-induced Brillouin frequency shift (BFS) changes using Brillouin optical time-domain analysis. A distributed measurement of hydrostatic pressure is demonstrated experimentally using a 4-m sensing fiber, which has a high sensitivity, with a maximum measurement error less than 0.03 MPa at a 20-cm spatial resolution.
Bye, Jordan W; Freeman, Colin L; Howard, John D; Herz, Gregor; McGregor, James; Falconer, Robert J
2017-01-01
In this paper we demonstrate the application of pressure perturbation calorimetry (PPC) to the characterization of 2-propanol/water mixtures. PPC of different 2-propanol/water mixtures provides two useful measurements: (i) the change in heat (ΔQ); and (ii) the [Formula: see text] value. The results demonstrate that the ΔQ values of the mixtures deviate from that expected for a random mixture, with a maximum at ~20-25 mol% 2-propanol. This coincides with the concentration at which molecular dynamics (MD) simulations show a maximum deviation from random distribution, and also the point at which alcohol-alcohol hydrogen bonds become dominant over alcohol-water hydrogen bonds. Furthermore, the [Formula: see text] value showed transitions at 2.5 mol% 2-propanol and at approximately 14 mol% 2-propanol. Below 2.5 mol% 2-propanol the values of [Formula: see text] are negative; this is indicative of the presence of isolated 2-propanol molecules surrounded by water molecules. Above 2.5 mol% 2-propanol [Formula: see text] rises, reaching a maximum at ~14 mol% corresponding to a point where mixed alcohol-water networks are thought to dominate. The values and trends identified by PPC show excellent agreement not only with those obtained from MD simulations but also with results in the literature derived using viscometry, THz spectroscopy, NMR and neutron diffraction.
Line Emission from Radiation-Pressurized HII Region II: Dynamics and Population Synthesis
Verdolini, Silvia; Krumholz, Mark R; Matzner, Christopher D; Tielens, Alexander G G M
2013-01-01
Optical and infrared emission lines from HII regions are an important diagnostic used to study galaxies, but interpretation of these lines requires significant modeling of both the internal structure and dynamical evolution of the emitting regions. Most of the models in common use today assume that HII region dynamics are dominated by the expansion of stellar wind bubbles, and have neglected the contribution of radiation pressure to the dynamics, and in some cases also to the internal structure. However, recent observations of nearby galaxies suggest that neither assumption is justified, motivating us to revisit the question of how HII region line emission depends on the physics of winds and radiation pressure. In a companion paper we construct models of single HII regions including and excluding radiation pressure and winds, and in this paper we describe a population synthesis code that uses these models to simulate galactic collections of HII regions with varying physical parameters. We show that the choice...
Dynamic pressure model derived from an observation by Sakigake for Comet Halley on 31 December, 1985
Saito, Takao; Yumoto, Kiyohumi; Hirao, Kunio; Saito, Keiji; Nakagawa, Tomoko; Smith, Edward
1986-01-01
An outstanding disconnection event (DE)-like knot was observed on 31 Dec. 1985 in P/Halley's tail. Analysis of the Sakigake/IMF data reveals that comet Halley did not encounter the heliospheric neutral sheet on the day, demanding a new explanation of the DE-like event. During this event, the comet encountered a high-speed solar wind from a coronal hole tongue of the Sun. The event can be explained by a dynamic pressure model, according to which the DE-like plasmoid was caused by a sudden increase in the dynamic pressure of the solar wind. A simulation result is found to support this interpretation. The dynamic pressure model for a comet can be compared with the mechanism of a possible geotail disturbance during a spacecraft triggered auroral substorm.
Gouin, Henri; Ruggeri, Tommaso
2008-07-01
We present a classical approach to a mixture of compressible fluids when each constituent has its own temperature. The introduction of an average temperature together with the entropy principle dictates the classical Fick law for diffusion and also novel constitutive equations associated with the difference of temperatures between the components. The constitutive equations fit with results recently obtained through a Maxwellian iteration procedure in extended thermodynamics theory of multitemperature mixtures. The differences of temperatures between the constituents imply the existence of a dynamical pressure even if the fluids have a zero bulk viscosity. The nonequilibrium dynamical pressure can be measured and may be convenient in several physical situations, such as, for example, in cosmological circumstances where--as many authors assert--a dynamical pressure played a major role in the evolution of the early universe.
HUANG Wen-yao; YAN Shi-long; WU Hong-bo; YUAN Sheng-fang
2011-01-01
Dynamic pressure was applied on emulsion explosive by using an underwater explosion measuring apparatus, and the crystallization quantity was measured by dissolution method after emulsion explosive was pressed; the influence of emulsi fier content and type was analyzed. The experimental results show that emulsifier content and type have an important effect on crystallization quantity of emulsion explosive. The crystallization quantity will reduce with Span-80 content from 2% to 4%, so the demulsification and crystallization will decrease if the emulsifier content improves appropriately and the dynamic pressure resistance will increase. For emulsion explosive emulsified by T-152 and Span-80, the crystallization quantity with T-152 is less than that of Span-80 under the same dynamic pressure. This shows that the emulsifying effect of T-152 is better than Span-80.
A data base and analysis program for shuttle main engine dynamic pressure measurements
Coffin, T.
1986-01-01
A dynamic pressure data base management system is described for measurements obtained from space shuttle main engine (SSME) hot firing tests. The data were provided in terms of engine power level and rms pressure time histories, and power spectra of the dynamic pressure measurements at selected times during each test. Test measurements and engine locations are defined along with a discussion of data acquisition and reduction procedures. A description of the data base management analysis system is provided and subroutines developed for obtaining selected measurement means, variances, ranges and other statistics of interest are discussed. A summary of pressure spectra obtained at SSME rated power level is provided for reference. Application of the singular value decomposition technique to spectrum interpolation is discussed and isoplots of interpolated spectra are presented to indicate measurement trends with engine power level. Program listings of the data base management and spectrum interpolation software are given. Appendices are included to document all data base measurements.
Application of nonlinear dynamic techniques to high pressure plasma jets
Ghorui, S.; Das, A. K.
2010-02-01
Arcs and arc plasmas have been known and used for welding, cutting, chemical synthesis and multitude of other industrial applications for more than hundred years. Though a copious source of heat, light and active species, plasma arc is inherently unstable, turbulent and difficult to control. During recent years, primarily driven by the need of new and energy efficient materials processing, various research groups around the world have been studying new and innovative ways of looking at the issues related to arc dynamics, arc stabilization, species non equilibrium, flow and heat transfer in a stabilized arc plasma device. In this context, experimental determination of nature of arc instabilities using tools of non-linear dynamics, theoretical model formulation, prediction of instability behavior under given operating conditions and possible control methods for the observed instabilities in arcs are reviewed. Space selective probing of the zones inside arc plasma devices without disturbing the system is probably the best way to identify the originating zone of instabilities inside such devices. Existence of extremely high temperature and inaccessibility to direct experimentations due to mechanical obstructions make this task extremely difficult. Probing instabilities in otherwise inaccessible inner regions of the torches, using binary gas mixture as plasma gas is a novel technique that primarily rests on a process known as demixing in arcs. Once a binary gas mixture enters the constricted plasma column, the demixing process sets in causing spatial variations for each of the constituent gases depending on the diffusion coefficients and the gradient of the existing temperature field. By varying concentrations of the constituent gases in the feeding line, it is possible to obtain spatial variations of the plasma composition in a desired manner, enabling spatial probing of the associated zones. Detailed compositional description of different zones inside the torch may be
Riisgaard, Benjamin; Ngo, Tuan; Mendis, Priyan
2007-01-01
This paper provides dynamic increase factors (DIF) in compression for two different High Performance Concretes (HPC), 100 MPa and 160 MPa, respectively. In the experimental investigation 2 different Split Hopkinson Pressure Bars are used in order to test over a wide range of strain rates, 100 sec1...... to 700 sec-1. The results are compared with the CEB Model Code and the Spilt Hopkinson Pressure Bar technique is briefly de-scribed....
YIN Bing; DONG Shun-Le
2009-01-01
A molecular dynamics simulation is performed for water confined within carbon nanotubes with diameters 11.00 (A) and 12.38 (A).Under pressures from 0.1 MPa to 500MPa the simulations are carried out by cooling from 300K to 240 K.Water molecules tend to transform from disordered to ordered with different configurations (square,pentagonal,hexagonal and hexagonal plus a chain).It is concluded that denser structures may appear under high pressures.
Dynamic baroreflex control of blood pressure: influence of the heart vs. peripheral resistance.
Liu, Huang-Ku; Guild, Sarah-Jane; Ringwood, John V; Barrett, Carolyn J; Leonard, Bridget L; Nguang, Sing-Kiong; Navakatikyan, Michael A; Malpas, Simon C
2002-08-01
The aim in the present experiments was to assess the dynamic baroreflex control of blood pressure, to develop an accurate mathematical model that represented this relationship, and to assess the role of dynamic changes in heart rate and stroke volume in giving rise to components of this response. Patterned electrical stimulation [pseudo-random binary sequence (PRBS)] was applied to the aortic depressor nerve (ADN) to produce changes in blood pressure under open-loop conditions in anesthetized rabbits. The stimulus provided constant power over the frequency range 0-0.5 Hz and revealed that the composite systems represented by the central nervous system, sympathetic activity, and vascular resistance responded as a second-order low-pass filter (corner frequency approximately 0.047 Hz) with a time delay (1.01 s). The gain between ADN and mean arterial pressure was reasonably constant before the corner frequency and then decreased with increasing frequency of stimulus. Although the heart rate was altered in response to the PRBS stimuli, we found that removal of the heart's ability to contribute to blood pressure variability by vagotomy and beta(1)-receptor blockade did not significantly alter the frequency response. We conclude that the contribution of the heart to the dynamic regulation of blood pressure is negligible in the rabbit. The consequences of this finding are examined with respect to low-frequency oscillations in blood pressure.
Dynamic Wave Pressures on Deeply Embedded Large Cylindrical Structures due to Random Waves
刘海笑; 唐云; 周锡礽
2003-01-01
The response of dynamic wave pressures on structures would be more complicated and bring about new phenomena under the dynamic interaction between soil and structure. In order to better understand the response characteristics on deeply embedded large cylindrical structures under random waves, and accordingly to offer valuable findings for engineering, the authors designed wave flume experiments to investigate comparatively dynamic wave pressures on a single and on continuous cylinders with two different embedment depths in response to two wave spectra.The time histories of the water surface elevation and the corresponding dynamic wave pressures exerted on the cylinder were analyzed in the frequency domain. By calculating the transfer function and spectral density for dynamic wave pressures along the height and around the circumference of the cylinder, experimental results of the single cylinder were compared with the theoretical results based on the linear diffraction theory, and detailed comparisons were also carried out between the single and continuous cylinders. Some new findings and the corresponding analysis are reported in present paper. The investigation on continuous cylinders will be used in particular for reference in engineering applications because information is scarce on studying such kind of problem both analytically and experimentally.
Dynamic Shock Compression of Copper to Multi-Megabar Pressure
Haill, T. A.; Furnish, M. D.; Twyeffort, L. L.; Arrington, C. L.; Lemke, R. W.; Knudson, M. D.; Davis, J.-P.
2015-11-01
Copper is an important material for a variety of shock and high energy density applications and experiments. Copper is used as a standard reference material to determine the EOS properties of other materials. The high conductivity of copper makes it useful as an MHD driver layer in high current dynamic materials experiments on Sandia National Laboratories Z machine. Composite aluminum/copper flyer plates increase the dwell time in plate impact experiments by taking advantage of the slower wave speeds in copper. This presentation reports on recent efforts to reinstate a composite Al/Cu flyer capability on Z and to extend the range of equation-of-state shock compression data through the use of hyper-velocity composite flyers and symmetric planar impact with copper targets. We will present results from multi-dimensional ALEGRA MHD simulations, as well as experimental designs and methods of composite flyer fabrication. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Halldorsdottir, Valgerdur G; Dave, Jaydev K; Leodore, Lauren M; Eisenbrey, John R; Park, Suhyun; Hall, Anne L; Thomenius, Kai; Forsberg, Flemming
2011-07-01
Our group has proposed the concept of subharmonic aided pressure estimation (SHAPE) utilizing microbubble-based ultrasound contrast agent signals for the noninvasive estimation of hydrostatic blood pressures. An experimental system for in vitro SHAPE was constructed based on two single-element transducers assembled confocally at a 60 degree angle to each other. Changes in the first, second and subharmonic amplitudes of five different ultrasound contrast agents were measured in vitro at static hydrostatic pressures from 0-186 mmHg, acoustic pressures from 0.35-0.60 MPa peak-to-peak and frequencies of 2.5-6.6 MHz. The most sensitive agent and optimal parameters for SHAPE were determined using linear regression analysis and implemented on a Logiq 9 scanner (GE Healthcare, Milwaukee, WI). This implementation of SHAPE was then tested under dynamic-flow conditions and compared to pressure-catheter measurements. Over the pressure range studied, the first and second harmonic amplitudes reduced approximately 2 dB for all contrast agents. Over the same pressure range, the subharmonic amplitudes decreased by 9-14 dB and excellent linear regressions were achieved with the hydrostatic pressure variations (r = 0.98, p scanner was modified to implement SHAPE on a convex transducer with a frequency range from 1.5-4.5 MHz and acoustic pressures from 0-3.34 MPa. Results matched the pressure catheter (r2 = 0.87). In conclusion, subharmonic contrast signals are a good indicator of hydrostatic pressure. Out of the five ultrasound contrast agents tested, Sonazoid was the most sensitive for subharmonic pressure estimation. Real-time SHAPE has been implemented on a commercial scanner and offers the possibility of allowing pressures in the heart and elsewhere to be obtained noninvasively.
Karlsson, J S; Ostlund, N; Larsson, B; Gerdle, B
2003-10-01
Frequency analysis of myoelectric (ME) signals, using the mean power spectral frequency (MNF), has been widely used to characterize peripheral muscle fatigue during isometric contractions assuming constant force. However, during repetitive isokinetic contractions performed with maximum effort, output (force or torque) will decrease markedly during the initial 40-60 contractions, followed by a phase with little or no change. MNF shows a similar pattern. In situations where there exist a significant relationship between MNF and output, part of the decrease in MNF may per se be related to the decrease in force during dynamic contractions. This study estimated force effects on the MNF shifts during repetitive dynamic knee extensions. Twenty healthy volunteers participated in the study and both surface ME signals (from the right vastus lateralis, vastus medialis, and rectus femoris muscles) and the biomechanical signals (force, position, and velocity) of an isokinetic dynamometer were measured. Two tests were performed: (i) 100 repetitive maximum isokinetic contractions of the right knee extensors, and (ii) five gradually increasing static knee extensions before and after (i). The corresponding ME signal time-frequency representations were calculated using the continuous wavelet transform. Compensation of the MNF variables of the repetitive contractions was performed with respect to the individual MNF-force relation based on an average of five gradually increasing contractions. Whether or not compensation was necessary was based on the shape of the MNF-force relationship. A significant compensation of the MNF was found for the repetitive isokinetic contractions. In conclusion, when investigating maximum dynamic contractions, decreases in MNF can be due to mechanisms similar to those found during sustained static contractions (force-independent component of fatigue) and in some subjects due to a direct effect of the change in force (force-dependent component of fatigue
D. A. Ganyushkin
2016-01-01
Full Text Available Glaciation of the Chikhachev ridge (South-Eastern Altai remains poorly known: field observations were not performed since the mid-twentieth century, available schemes and estimates of the glaciation and its scale made on the basis of remote sensing cover only a part of the glaciers, reconstructions of the Little Ice Age (LIA glaciations are absent. This research was based on interpretation of the satellite images: Landsat-4 (1989, Landsat-7 (2001, and Spot-5 (2011, as well as with the use of data of the field season of 2015. Characteristics of glaciations of the Chikhachev ridge as the whole and of its individual centers (Talduair massif, Mongun-Taiga-Minor massif, and southern part of the Chikhachev ridge were determined for the first time. Recent glaciation is represented by 7 glaciers with their total area of 1.12 km2 in the Talduair massif, by 5 glaciers with total area of 0.75 km2 in the Mongun-Taiga-Minor massif, and by 85 glaciers with total area of 29 km2 in the southern part of the Chikhachev ridge. Since the LIA maximum, areas of glaciers decreased by 61% in the Talduair massif, by 74% in the Mongun-Taiga-Minor massif, by 56% in the southern part of the Chikhachev ridge with simultaneous lifting of the firn line by 50 m, 65 m, and 70 m, respectively.The largest rates of the glacier contractions were determined for the period 1989–2011. Different mechanisms of the glacier retreats were shown by the example of the glacier complexes Burgastyn-Gol (one-sided retreat and disintegration and the Grigorjev glacier (gradual retreat of the tongue. Retreat of the Grigorjev glacier has been reconstructed for the period from the LIA maximum until 2015. Average rate of the retreat increased from 1,6 m/year in 1957–1989 up to 11,3 m/year in 2011–2015. The present-day scales of the glaciers and rates of their retreating do not significantly differ from estimations made by other researchers for the nearest centers of glaciation of the
[Mobile phone platform for wireless monitoring of human dynamic plantar pressure].
Wang, Hao; Han, Meng; Liu, Jing
2010-11-01
This paper constructed a plantar pressure sensing system based on Bluetooth communication of mobile phone with embedded Windows Mobile system. With the MCU (Microprocessor Control Unit) and Bluetooth module, the pressure sensor and the data acquisition circuit was designed and integrated, with software developed under Visual Studio 2008 environment. The real-time monitoring of human dynamic plantar pressure signal, and transferring, displaying and storing the recorded data on a mobile phone were achieved. This method offers an important measure to acquire human gait information via a pervasive and low cost way.
Suzuki, N
2002-01-01
First-principles calculations are performed for the lattice dynamics and electron-phonon interaction of the body-centred-cubic (bcc) phase of solid vanadium. A remarkable phonon anomaly is found, i.e. frequencies of the transverse mode around a quarter of the GAMMA-H line show softening with increasing pressure and become imaginary at pressures higher than approx 130 GPa. The superconducting transition temperatures T sub c of bcc vanadium estimated as a function of pressure increases at first linearly with pressure, and then the rate of increase of T sub c is abated around 80 GPa. This calculated pressure dependence of T sub c shows qualitatively the same behaviour as the experimental result.
Wang, Hui; Huang, Tao; Tu, Zong-Cai; Ruan, Chuan-Ying; Lin, Derong
2016-06-01
Insoluble dietary fiber from soybean residue (SIDF) was treated with dynamic high-pressure microfluidization (DHPM) and used as adsorbent for Pb(II) ion. The effects of pressure on the Pb(II) adsorption capacity, primary cilia structure and surface topography of SIDF were determined using a gastrointestinal simulated model in vitro. SIDF (at pH 7.0) showed maximum binding capacity (261.42 ± 2.77 μmol/g), which was about 1.13 times higher than that of untreated sample (233.47 ± 1.84 μmol/g), when pressure reached 80 MPa. However, the net adsorption value of SIDF in a simulated small intestine (~ 9 μmol/g) was significantly lower than that in the stomach (~ 48 μmol/g), because of the competitive adsorption of Pb(2+) by pancreatin, cholate and several enzymes in the small intestine. In addition, the adsorption capacity of SIDF exhibited good linear relationship with the physicochemical properties of total negative charges, and the adsorption behavior presumably occurred on the surface area of granules fiber.
Dynamic calibration of piezoelectric transducers for ballistic high-pressure measurement
Elkarous Lamine
2016-01-01
Full Text Available The development of a dynamic calibration standard for high-amplitude pressure piezoelectric transducers implies the implementation of a system which can provide reference pressure values with known characteristics and uncertainty. The reference pressure must be issued by a sensor, as a part of a measuring chain, with a guaranteed traceability to an international standard. However, this operation has not been completely addressed yet until today and is still calling further investigations. In this paper, we introduce an experimental study carried out in order to contribute to current efforts for the establishment of a reference dynamic calibration method. A suitable practical calibration method based on the calculation of the reference pressure by measurement of the displacement of the piston in contact with an oil-filled cylindrical chamber is presented. This measurement was achieved thanks to a high speed camera and an accelerometer. Both measurements are then compared. In the first way, pressure was generated by impacting the piston with a free falling weight and, in the second way, with strikers of known weights and accelerated to the impact velocities with an air gun. The aim of the experimental setup is to work out a system which may generate known hydraulic pressure pulses with high-accuracy and known uncertainty. Moreover, physical models were also introduced to consolidate the experimental study. The change of striker’s velocities and masses allows tuning the reference pressure pulses with different shapes and, therefore, permits to sweep a wide range of magnitudes and frequencies.
Dynamics of phenotypic reversibility of bacterial cells with oscillating hydrostatic pressure
Nepal, Sudip; Kumar, Pradeep
Bacterial cells encounter and respond to physiochemical fluctuations. The response depends on the extent and type of the stresses applied. The response of bacterial cells to the fluctuating stress is relatively unknown. Here, we have studied the response of wild type Escherichia coli (E. coli) under fluctuating hydrostatic pressures ranging from 1 atm to 500 atm. High pressure acts as a stress to E. coli since these bacteria are adapted to grow optimally at atmospheric pressure. Cell division of E. coli is inhibited at high pressures resulting in increase in the length of the cells. Cell-length is reversible in nature and bacterial cells revert back to normal size on a time scale that is proportional to the strength and time of continuous pressure applied upon relaxing the high pressure condition. We have studied the dynamics of cellular reversibility of E. coli under the conditions in which continuous pressure is applied and subsequently relaxed over different time scales. We have quantified the dynamics of cellular reversibility with different relaxation times. Furthermore, we propose a model to describe the reversibility of the bacterial cell with the relaxation time. Our theoretical model fits well to the experimental data. We further
Vortex dynamics and surface pressure fluctuations on a normal flat plate
Hemmati, Arman; Wood, David H.; Martinuzzi, Robert J.; Ferrari, Simon W.; Hu, Yaoping
2016-11-01
The effect of vortex formation and interactions on surface pressure fluctuations is examined in the wake of a normal flat plate by analyzing Direct Numerical Simulations at Re =1200. A novel local maximum score-based 3D method is used to track vortex development in the region close to the plate where the major contributions to the surface pressure are generated. Three distinct vortex shedding regimes are identified by changes in the lift and drag fluctuations. The instances of maximum drag coincide with impingement of newly formed vortices on the plate. This results in large and concentrated areas of rotational and strain contributions to generation of pressure fluctuations. Streamwise vortex straining and chordwise stretching are correlated with the large ratios of streamwise to chordwise normal stresses and regions of significant rotational contribution to the pressure. In contrast at the minimum drag, the vorticity field close to the plate is disorganized, and vortex roll-up occurs farther downstream. This leads to a uniform distribution of pressure. This study was supported by Alberta Innovates Technology Futures (AITF) and Natural Sciences and Engineering Research Council of Canada (NSERC).
Chi Se Hwan; Kim, Joo Hag; Hong, Jun Hwa; Kwon, Sun Chil; Lee, Bong Sang [Korea Atomic Energy Research Institute, Taejon (Korea)
1999-10-01
The dynamic fracture toughness (K{sub d}) of intermediate shell and its weld in SA 508 CI. 3 Yong Gwang 5 reactor pressure vessel was determined and evaluated. Precracked thirty six Charpy specimens were tested by using an instrumented impact tester. The purpose of present work is to evaluate and confirm the un-irradiated dynamic fracture toughness and to provide pre-irradiation baseline data for future evaluation on dynamic fracture toughness change during operation. 18 refs., 5 figs., 5 tabs. (Author)
Peng, Mingzeng; Li, Zhou; Liu, Caihong; Zheng, Qiang; Shi, Xieqing; Song, Ming; Zhang, Yang; Du, Shiyu; Zhai, Junyi; Wang, Zhong Lin
2015-03-24
A high-resolution dynamic tactile/pressure display is indispensable to the comprehensive perception of force/mechanical stimulations such as electronic skin, biomechanical imaging/analysis, or personalized signatures. Here, we present a dynamic pressure sensor array based on pressure/strain tuned photoluminescence imaging without the need for electricity. Each sensor is a nanopillar that consists of InGaN/GaN multiple quantum wells. Its photoluminescence intensity can be modulated dramatically and linearly by small strain (0-0.15%) owing to the piezo-phototronic effect. The sensor array has a high pixel density of 6350 dpi and exceptional small standard deviation of photoluminescence. High-quality tactile/pressure sensing distribution can be real-time recorded by parallel photoluminescence imaging without any cross-talk. The sensor array can be inexpensively fabricated over large areas by semiconductor product lines. The proposed dynamic all-optical pressure imaging with excellent resolution, high sensitivity, good uniformity, and ultrafast response time offers a suitable way for smart sensing, micro/nano-opto-electromechanical systems.
Ipsen, Andreas; Ebbels, Timothy M D
2014-10-01
In a recent article, we derived a probability distribution that was shown to closely approximate that of the data produced by liquid chromatography time-of-flight mass spectrometry (LC/TOFMS) instruments employing time-to-digital converters (TDCs) as part of their detection system. The approach of formulating detailed and highly accurate mathematical models of LC/MS data via probability distributions that are parameterized by quantities of analytical interest does not appear to have been fully explored before. However, we believe it could lead to a statistically rigorous framework for addressing many of the data analytical problems that arise in LC/MS studies. In this article, we present new procedures for correcting for TDC saturation using such an approach and demonstrate that there is potential for significant improvements in the effective dynamic range of TDC-based mass spectrometers, which could make them much more competitive with the alternative analog-to-digital converters (ADCs). The degree of improvement depends on our ability to generate mass and chromatographic peaks that conform to known mathematical functions and our ability to accurately describe the state of the detector dead time-tasks that may be best addressed through engineering efforts.
Ipsen, Andreas; Ebbels, Timothy M. D.
2014-10-01
In a recent article, we derived a probability distribution that was shown to closely approximate that of the data produced by liquid chromatography time-of-flight mass spectrometry (LC/TOFMS) instruments employing time-to-digital converters (TDCs) as part of their detection system. The approach of formulating detailed and highly accurate mathematical models of LC/MS data via probability distributions that are parameterized by quantities of analytical interest does not appear to have been fully explored before. However, we believe it could lead to a statistically rigorous framework for addressing many of the data analytical problems that arise in LC/MS studies. In this article, we present new procedures for correcting for TDC saturation using such an approach and demonstrate that there is potential for significant improvements in the effective dynamic range of TDC-based mass spectrometers, which could make them much more competitive with the alternative analog-to-digital converters (ADCs). The degree of improvement depends on our ability to generate mass and chromatographic peaks that conform to known mathematical functions and our ability to accurately describe the state of the detector dead time—tasks that may be best addressed through engineering efforts.
The Non-selfsimilar Riemann Problem for 2-D Zero-Pressure Flow in Gas Dynamics
Wenhua SUN; Wancheng SHENG
2007-01-01
The non-selfsimilar Riemann problem for two-dimensional zero-pressure flow in gas dynamics with two constant states separated by a convex curve is considered. By means of the generalized Rankine-Hugoniot relation and the generalized characteristic analysis method, the global solution involving delta shock wave and vacuum is constructed. The explicit solution for a special case is also given.
Plasma flow structures as analytical solution of a magneto-hydro-dynamic model with pressure
Paccagnella, R.
2012-03-01
In this work starting from a set of magnetohydrodynamic (MHD) equations that describe the dynamical evolution for the pressure driven resistive/interchange modes in a magnetic confinement system, global solutions for the plasma flow relevant for toroidal pinches like tokamaks and reversed field pinches (RFPs) are derived. Analytical solutions for the flow stream function associated with the dominant modes are presented.
Pressure-area isotherm of a lipid monolayer from molecular dynamics simulations
Baoukina, Svetlana; Monticelli, Luca; Marrink, Siewert J.; Tieleman, D. Peter
2007-01-01
We calculated the pressure-area isotherm of a dipalmitoyl-phosphatidylcholine (DPPC) lipid monolayer from molecular dynamics simulations using a coarse-grained molecular model. We characterized the monolayer structure, geometry, and phases directly from the simulations and compared the calculated
Andrałojć, Witold; Ravera, Enrico; Salmon, Loïc; Parigi, Giacomo; Al-Hashimi, Hashim M; Luchinat, Claudio
2016-02-17
Detecting conformational heterogeneity in biological macromolecules is a key for the understanding of their biological function. We here provide a comparison between two independent approaches to assess conformational heterogeneity: molecular dynamics simulations, performed without inclusion of any experimental data, and maximum occurrence (MaxOcc) distribution over the topologically available conformational space. The latter only reflects the extent of the averaging and identifies regions which are most compliant with the experimentally measured NMR Residual Dipolar Couplings (RDCs). The analysis was performed for the HIV-1 TAR RNA, consisting of two helical domains connected by a flexible bulge junction, for which four sets of RDCs were available as well as an 8.2 μs all-atom molecular dynamics simulation. A sample and select approach was previously applied to extract from the molecular dynamics trajectory conformational ensembles in agreement with the four sets of RDCs. The MaxOcc analysis performed here identifies the most likely sampled region in the conformational space of the system which, strikingly, overlaps well with the structures independently sampled in the molecular dynamics calculations and even better with the RDC selected ensemble.
Poyatos, A.; Bonaque, R.; Mallol, G.; Boix, J.
2012-07-01
The organization MACER, in collaboration with the Institute of Ceramic Technology, has developed the system ISOPRESS, an integrated control device that permits to equal automatically the maximum pressure applied on the powder contained in each of the holes of the mould. This system consists of a set of pressure transducers which are located in the isostatic punches of the mould itself. With them it is possible to register in real-time the evolution of the measured pressure of the oil contained in the compensation chamber of each punch. All the transducers are connected to a data acquisition system which transfers the pressure values to a PC which performs the signal processing to obtain the pressure maximum value reached during a pressing cycle, in each one of the holes. The system is completed with a control software especially developed, that permits to regulate individually the height of the first fall of each inferior punch to guarantee the uniformity of the pressure applied in all the holes. ISOPRESS, by assuring the constancy of the bulk density of all the pieces processed, guarantees a unique piece size and minimize production problems associated to the variability of the bulk density of the pieces. (Author)
Towards a standard for the dynamic measurement of pressure based on laser absorption spectroscopy
Douglass, K. O.; Olson, D. A.
2016-06-01
We describe an approach for creating a standard for the dynamic measurement of pressure based on the measurement of fundamental quantum properties of molecular systems. From the linewidth and intensities of ro-vibrational transitions we plan on making an accurate determination of pressure and temperature. The goal is to achieve an absolute uncertainty for time-varying pressure of 5% with a measurement rate of 100 kHz, which will in the future serve as a method for the traceable calibration of pressure sensors used in transient processes. To illustrate this concept we have used wavelength modulation spectroscopy (WMS), due to inherent advantages over direct absorption spectroscopy, to perform rapid measurements of carbon dioxide in order to determine the pressure. The system records the full lineshape profile of a single ro-vibrational transition of CO2 at a repetition rate of 4 kHz and with a systematic measurement uncertainty of 12% for the linewidth measurement. A series of pressures were measured at a rate of 400 Hz (10 averages) and from these measurements the linewidth was determined with a relative uncertainty of about 0.5% on average. The pressures measured using WMS have an average difference of 0.6% from the absolute pressure measured with a capacitance diaphragm sensor.
Towards a standard for the dynamic measurement of pressure based on laser absorption spectroscopy.
Douglass, K O; Olson, D A
2016-06-01
We describe an approach for creating a standard for the dynamic measurement of pressure based on the measurement of fundamental quantum properties of molecular systems. From the linewidth and intensities of ro-vibrational transitions we plan on making an accurate determination of pressure and temperature. The goal is to achieve an absolute uncertainty for time-varying pressure of 5 % with a measurement rate of 100 kHz, which will in the future serve as a method for the traceable calibration of pressure sensors used in transient processes. To illustrate this concept we have used wavelength modulation spectroscopy (WMS), due to inherent advantages over direct absorption spectroscopy, to perform rapid measurements of carbon dioxide in order to determine the pressure. The system records the full lineshape profile of a single ro-vibrational transition of CO2 at a repetition rate of 4 kHz and with a systematic measurement uncertainty of 12 % for the linewidth measurement. A series of pressures were measured at a rate of 400 Hz (10 averages) and from these measurements the linewidth was determined with a relative uncertainty of about 0.5 % on average. The pressures measured using WMS have an average difference of 0.6 % from the absolute pressure measured with a capacitance diaphragm sensor.
Modeling the dynamic response of pressures in a distributed helium refrigeration system
Brubaker, John Carl [Illinois Inst. of Technology, Chicago, IL (United States)
1997-12-01
A mathematical model is created of the dynamic response of pressures caused by flow inputs to an existing distributed helium refrigeration system. The dynamic system studied consists of the suction and discharge pressure headers and compressor portions of the refrigeration system used to cool the superconducting magnets of the Tevatron accelerator at the Fermi National Accelerator Laboratory. The modeling method involves identifying the system from data recorded during a series of controlled tests, with effort made to detect locational differences in pressure response around the four mile accelerator circumference. A review of the fluid mechanics associated with the system indicates linear time invariant models are suitable for the identification, particularly since the governing equations of one dimensional fluid flow are approximated by linear differential equations. An outline of the experimental design and the data acquisition system are given, followed by a detailed description of the modeling, which utilized the Matlab programming language and associated System Identification Toolbox. Two representations of the system are presented. One, a black box model, provides a multi-input, multi-output description assembled from the results of single input step function testing. This description indicates definite variation in pressure response with distance from the flow input location, and also suggests subtle differences in response with the input location itself. A second system representation is proposed which details the relation between continuous flow changes and pressure response, and provides explanation of a previously unappreciated pressure feedback internal to the system.
Evans, W J; Yoo, C; Lee, G W; Cynn, H; Lipp, M J; Visbeck, K
2007-02-23
We have developed a unique device, a dynamic diamond anvil cell (dDAC), which repetitively applies a time-dependent load/pressure profile to a sample. This capability allows studies of the kinetics of phase transitions and metastable phases at compression (strain) rates of up to 500 GPa/sec ({approx}0.16 s{sup -1} for a metal). Our approach adapts electromechanical piezoelectric actuators to a conventional diamond anvil cell design, which enables precise specification and control of a time-dependent applied load/pressure. Existing DAC instrumentation and experimental techniques are easily adapted to the dDAC to measure the properties of a sample under the varying load/pressure conditions. This capability addresses the sparsely studied regime of dynamic phenomena between static research (diamond anvil cells and large volume presses) and dynamic shock-driven experiments (gas guns, explosive and laser shock). We present an overview of a variety of experimental measurements that can be made with this device.
Modeling of fluid dynamics interacting with ductile fraction propagation in high pressure pipeline
Mihaela Popescu
2009-01-01
This paper presents a computational model for the fluid dynamics in a fractured ductile pipe under high pressure. The pressure profile in front of the crack tip, which is the driving source of crack propagation, is computed using a nonlinear wave equation. The solution is coupled with a one dimensional choked flow analysis behind the crack. The simulation utilizes a high order optimized prefactored com-pact-finite volume method in space, and low dispersion and dissipation Runge-Kutta in time. As the pipe fractures the rapid depressurization take place inside the pipe and the prop-agation of the crack-induced waves strongly influences the outflow dynamics. Consistent with the experimental observa-tion, the model predicts the expansion wave inside the pipe, and the reflection and outflow of the wave. The model also helps characterize the propagation of the crack dynamics and fluid flows around the tip of the crack.
Sahuquillo, J; Rubio, E; Codina, A; Molins, A; Guitart, J M; Poca, M A; Chasampi, A
1991-01-01
Fifty-four shunt-responsive patients were selected from a prospective protocol directed to study patients with suspected normal pressure hydrocephalus (NPH). Patients with gait disturbances, dementia, non-responsive L-Dopa Parkinsonism, urinary or faecal incontinence and an Evans ratio greater or equal to 0.30 on the CT scan were included in the study. As a part of their work-up all patients underwent intracranial pressure monitoring and hydrodynamic studies using Marmarou's bolus test. According to mean intracranial pressure (ICP) and the percentage of high amplitude B-waves, patients were subdivided in the following categories: 1) Active hydrocephalus (mean ICP above 15 mmHg), which is in fact no tone normal pressure hydrocephalus; 2) Compensated unstable hydrocephalus, when mean ICP was below 15 mmHg and B-waves were present in more than 25% of the total recording time and 3) Compensated stable hydrocephalus when ICP was lower or equal to 15 mmHg and beta waves were present in less than 25% of the total recording time. The majority of the patients in this study (70%) presented continuous high or intermittently raised ICP (active or unstable compensated hydrocephalus group). Mean resistance to outflow of CSF (Rout) was 38.8 mm Hg/ml/min in active hydrocephalus and 23.5 mm Hg/ml/min in the compensated group (Students t-test, p less than 0.05). Higher resistance to outflow was found in patients with obliterated cortical sulci and obliterated Sylvian cisterns in the CT scan. No statistically significant correlation was found when plotting the percentage of beta waves against pressure volume index (PVI), compliance or Rout. An exponential correlation was found when plotting beta waves against the sum of conductance to outflow and compliance calculated by PVI method (r = 0.79). Patients with the so-called normal pressure hydrocephalus syndrome have different ICP and CSF dynamic profiles. Additional studies taking into consideration these differences are necessary
J. Ponce
2010-09-01
Full Text Available
The effects of maximal dynamic exercise (sprint has been studied on the ECG of 100 greyhound who run in programmed 350 m races. Two ECG were taken in each animal: one before the race and the other after the effort. After the race there is a significant increase of the voltage in the waves P, R and T in DII, DIII and aVF, and the T waves are symetrical in 96% of the subjets. The highest voltage and duration of the P wawes represent the efficacy of the atrial function on the maintenance of the cardiac output. The increase of the amplitude of the R and T waves would be a consequence of the systolic volumen increase and the establishment of transitory myocardial ischemia. The average heart rate increases in 21.740"30.109 b.p.m., beeing the difference significant. When we analyse the ECG after exercise with the resting ECG in relation with age, weight, sex, category and rank we deduce that the differences arent related with those groups, except to the heart rate and age, observing that the capacity in increasing it decreases with age.
KEY WORDS: Oxygen deficit, anaerobic capacity, performance, validity, fitness.
Se han estudiado los efectos del ejercicio dinámico máximo (sprint sobre el ECG en 100 galgos greyhound que participaban en carreras programadas de 350 m. Se realizaron dos ECG en cada animal: uno antes de la carrera y otro postesfuerzo. Después de la carrera hay un aumento significativo del voltaje de las ondas P, R y T en DII, DIII y aVF, y las ondas T son simétricas en el 96% de los sujetos. El mayor voltaje y duración de las ondas P representan la eficacia de la función auricular para el mantenimiento del volumen minuto. El incremento de la amplitud de las ondas R y T sería consecuencia del aumento del volumen sistólico y de la instauración de isquemia miocárdica relativa transitoria. La
Strasser, Barbara; Schwarz, Joachim; Haber, Paul; Schobersberger, Wolfgang
2011-12-01
Aim of this study was to evaluate reliable guide values for heart rate (HF) and blood pressure (RR) with reference to defined sub maximum exertion considering age, gender and body mass. One hundred and eighteen healthy but non-trained subjects (38 women, 80 men) were included in the study. For interpretation, finally facts of 28 women and 59 men were used. We found gender differences for HF and RR. Further, we noted significant correlations between HF and age as well as between RR and body mass at all exercise levels. We established formulas for gender-specific calculation of reliable guide values for HF and RR on sub maximum exercise levels.
HOW SIGNIFICANT IS RADIATION PRESSURE IN THE DYNAMICS OF THE GAS AROUND YOUNG STELLAR CLUSTERS?
Silich, Sergiy; Tenorio-Tagle, Guillermo, E-mail: silich@inaoep.mx [Instituto Nacional de Astrofisica Optica y Electronica, AP 51, 72000 Puebla (Mexico)
2013-03-01
The impact of radiation pressure on the dynamics of the gas in the vicinity of young stellar clusters is thoroughly discussed. The radiation over the thermal/ram pressure ratio time evolution is calculated explicitly and the crucial roles of the cluster mechanical power, the strong time evolution of the ionizing photon flux, and the bolometric luminosity of the exciting cluster are stressed. It is shown that radiation has only a narrow window of opportunity to dominate the wind-driven shell dynamics. This may occur only at early stages of the bubble evolution and if the shell expands into a dusty and/or a very dense proto-cluster medium. The impact of radiation pressure on the wind-driven shell always becomes negligible after about 3 Myr. Finally, the wind-driven model results allow one to compare the model predictions with the distribution of thermal pressure derived from X-ray observations. The shape of the thermal pressure profile then allows us to distinguish between the energy and the momentum-dominated regimes of expansion and thus conclude whether radiative losses of energy or the leakage of hot gas from the bubble interior have been significant during bubble evolution.
How Significant is Radiation Pressure in the Dynamics of the Gas Around Young Stellar Clusters?
Silich, Sergiy
2013-01-01
The impact of radiation pressure on the dynamics of the gas in the vicinity of young stellar clusters is thoroughly discussed. The radiation over the thermal/ram pressure ratio time evolution is calculated explicitely and the crucial role of the cluster mechanical power and of the strong time evolution of the ionizing photon flux and of the bolometric luminosity of the exciting cluster is stressed. It is shown that radiation has only a narrow window of opportunity to dominate the wind-driven shell dynamics. This may occur only at early stages of the bubble evolution and if the shell expands into a dusty and/or a very dense proto-cluster medium. The impact of radiation pressure on the wind-driven shell becomes always negligible after about 3 Myr. Finally, the wind-driven model results allow one to compare the model predictions with the distribution of thermal pressure derived from X-ray observations. The shape of the thermal pressure profile allows then to distinguish between the energy and the momentum domina...
Dynamic Acousto-Elasticity: Pressure and Frequency Dependences in Berea Sandstone.
Riviere, J. V.; Pimienta, L.; Latour, S.; Fortin, J.; Schubnel, A.; Johnson, P. A.
2014-12-01
Nonlinear elasticity is studied at the laboratory scale with the goal of understanding observations at earth scales, for instance during strong ground motion, tidal forcing and earthquake slip processes. Here we report frequency and pressure dependences on elasticity when applying dynamic acousto-elasticity (DAE) of rock samples, analogous to quasi-static acousto-elasticity. DAE allows one to obtain the elastic behavior over the entire dynamic cycle, detailing the full nonlinear behavior under tension and compression, including hysteresis and memory effects. We perform DAE on a sample of Berea sandstone subject to 0.5MPa uniaxial load, with sinusoidal oscillating strain amplitudes ranging from 10-6 to 10-5 and at frequencies from 0.1 to 260Hz. In addition, the confining pressure is increased stepwise from 0 to 30MPa. We compare results to previous measurements made at lower (mHz) and higher (kHz) frequencies. Nonlinear elastic parameters corresponding to conditioning effects, third order elastic constants and fourth order elastic constants are quantitatively compared over the pressure and frequency ranges. We observe that the decrease in modulus due to conditioning increases with frequency, suggesting a frequency and/or strain-rate dependence that should be included in nonlinear elastic models of rocks. In agreement with previous measurements, nonlinear elastic effects also decrease with confining pressure, suggesting that nonlinear elastic sources such as micro-cracks, soft bonds and dislocations are turned off as the pressure increases.
Li, Qiang; Wang, Zhongyu; Wang, Zhuoran; Yan, Hu
2015-06-01
A shock tube is usually used to excite the dynamic characteristics of the pressure sensor used in an aircraft. This paper proposes a novel estimation method for determining the dynamic characteristic parameters of the pressure sensor. A preprocessing operation based on Grey Model [GM(1,1)] and bootstrap method (BM) is employed to analyze the output of a calibrated pressure sensor under step excitation. Three sequences, which include the estimated value sequence, upper boundary, and lower boundary, are obtained. The processing methods on filtering and modeling are used to explore the three sequences independently. The optimal estimated, upper boundary, and lower boundary models are then established. The three models are solved, and a group of dynamic characteristic parameters corresponding to the estimated intervals are obtained. A shock tube calibration test consisting of two experiments is performed to validate the performance of the proposed method. The results show that the relative errors of the dynamic characteristic parameters of time and frequency domains do not exceed 9% and 10%, respectively. Moreover, the nominal and estimated values of the parameters fall into the estimated intervals limited by the upper and lower values.
Dynamic distribution of gas pressure and emission around a driving roadway
Gao Jian-liang; Hou San-zhong [Henan Polytechnic University, Jiaozuo (China). School of Safety Science and Engineering
2007-11-15
The finite difference method was applied to simulate the dynamic variation of gas pressure in coal seams around a developing roadway and the gas emission rate on the airway surface. The gas pressure distribution advances with the advancement of the working face. The rate of emission of gas from the roadway surface decreases with the elapse of exposure time of the roadway surface. When the new working face is first exposed the emission of methane is highest and it then decreases sharply. 11 refs., 7 figs., 1 tab.
Shaebani, M Reza; Kertesz, Janos
2008-01-01
The contact dynamics method (CD) is an efficient simulation technique of dense granular media where unilateral and frictional contact problems for a large number of rigid bodies have to be solved. In this paper we present a modified version of the contact dynamics to generate homogeneous random packings of rigid grains. CD is coupled to an external pressure bath, which allows the variation of the size of a periodically repeated cell. We follow the concept of the Andersen dynamics and show how it can be applied within the framework of the contact dynamics method. The main challenge here is to handle the interparticle interactions properly, which are based on constraint forces in CD. We implement the proposed algorithm, perform test simulations and investigate the properties of the final packings.
Prosthetics socket that incorporates an air splint system focusing on dynamic interface pressure.
Razak, Nasrul Anuar Abd; Osman, Noor Azuan Abu; Gholizadeh, Hossein; Ali, Sadeeq
2014-08-01
The interface pressure between the residual limb and prosthetic socket has a significant effect on an amputee's satisfaction and comfort. This paper presents the design and performance of a new prosthetic socket that uses an air splint system. The air splint prosthetic socket system was implemented by combining the air splint with a pressure sensor that the transhumeral user controls through the use of a microcontroller. The modular construction of the system developed allows the FSR pressure sensors that are placed inside the air splint socket to determine the required size and fitting for the socket used. Fifteen transhumeral amputees participated in the study. The subject's dynamic pressure on the socket that's applied while wearing the air splint systems was recorded using F-socket transducers and microcontroller analysis. The values collected by the F-socket sensor for the air splint prosthetic socket system were determined accordingly by comparing the dynamic pressure applied using statically socket. The pressure volume of the air splint fluctuated and was recorded at an average of 38 kPa (2.5) to 41 kPa (1.3) over three hours. The air splint socket might reduce the pressure within the interface of residual limb. This is particularly important during the daily life activities and may reduce the pain and discomfort at the residual limb in comparison to the static socket. The potential development of an auto-adjusted socket that uses an air splint system as the prosthetic socket will be of interest to researchers involved in rehabilitation engineering, prosthetics and orthotics.
Lee, Nicholas Jabari Ouma
Parallel molecular dynamics (MD) simulations are performed to investigate pressure-induced solid-to-solid structural phase transformations in cadmium selenide (CdSe) nanorods. The effects of the size and shape of nanorods on different aspects of structural phase transformations are studied. Simulations are based on interatomic potentials validated extensively by experiments. Simulations range from 105 to 106 atoms. These simulations are enabled by highly scalable algorithms executed on massively parallel Beowulf computing architectures. Pressure-induced structural transformations are studied using a hydrostatic pressure medium simulated by atoms interacting via Lennard-Jones potential. Four single-crystal CdSe nanorods, each 44A in diameter but varying in length, in the range between 44A and 600A, are studied independently in two sets of simulations. The first simulation is the downstroke simulation, where each rod is embedded in the pressure medium and subjected to increasing pressure during which it undergoes a forward transformation from a 4-fold coordinated wurtzite (WZ) crystal structure to a 6-fold coordinated rocksalt (RS) crystal structure. In the second so-called upstroke simulation, the pressure on the rods is decreased and a reverse transformation from 6-fold RS to a 4-fold coordinated phase is observed. The transformation pressure in the forward transformation depends on the nanorod size, with longer rods transforming at lower pressures close to the bulk transformation pressure. Spatially-resolved structural analyses, including pair-distributions, atomic-coordinations and bond-angle distributions, indicate nucleation begins at the surface of nanorods and spreads inward. The transformation results in a single RS domain, in agreement with experiments. The microscopic mechanism for transformation is observed to be the same as for bulk CdSe. A nanorod size dependency is also found in reverse structural transformations, with longer nanorods transforming more
Sharma, Shobha; Gupta, Aditya; Dhabal, Debdas; Kashyap, Hemant K.
2016-10-01
In the present molecular dynamics study, we investigate the effects of increasing pressure on the structural morphology of trihexyl(tetradecyl)phosphonium bromide (P666,14+/Br-) and trihexyl(tetradecyl)phosphonium dicyanamide (P666,14+/DCA-) ionic liquids (ILs). Special attention was paid to how charge and polarity orderings, which are present in the microscopic structure of these ILs at ambient conditions, respond to very high external pressure. The simulated X-ray scattering structure functions, S(q)s, of the two systems reveal that both the characteristic orderings show appreciable responsiveness towards the applied pressure change. At a given pressure, a slight difference between the polarity ordering (PO), charge ordering (CO), and adjacency correlations (AC) for both the systems points towards different microscopic structure of the two ILs due to change in anion. Beyond a certain pressure, we observe emergence of a new low-q peak in the S(q)s of both the systems. The new peak is associated with formation of crystalline order in these systems at higher pressures and the real space length-scale corresponding to the crystalline order lies in between those of polarity- and charge-ordering. Beyond the transition pressure, the crystallinity of both the systems increases with increasing pressure and the corresponding length-scale shifts towards smaller values upon increasing pressure. We also observe that the extent of the usual polarity ordering decreases upon increasing pressure for both the P666,14+/Br- and P666,14+/DCA- systems. We demonstrate that the disappearance of the usual polarity peak is due to decreased polar-polar and apolar-apolar correlations and enhanced correlations between the charged and uncharged groups of the ions. This scenario is completely reversed for the components corresponding to the crystalline order, the polar-polar and apolar-apolar correlations are enhanced and polar-apolar correlations are diminished at higher pressure. In addition
Gian Paolo Beretta
2008-08-01
Full Text Available A rate equation for a discrete probability distribution is discussed as a route to describe smooth relaxation towards the maximum entropy distribution compatible at all times with one or more linear constraints. The resulting dynamics follows the path of steepest entropy ascent compatible with the constraints. The rate equation is consistent with the Onsager theorem of reciprocity and the fluctuation-dissipation theorem. The mathematical formalism was originally developed to obtain a quantum theoretical unification of mechanics and thermodinamics. It is presented here in a general, non-quantal formulation as a part of an effort to develop tools for the phenomenological treatment of non-equilibrium problems with applications in engineering, biology, sociology, and economics. The rate equation is also extended to include the case of assigned time-dependences of the constraints and the entropy, such as for modeling non-equilibrium energy and entropy exchanges.
Beretta, Gian P.
2008-09-01
A rate equation for a discrete probability distribution is discussed as a route to describe smooth relaxation towards the maximum entropy distribution compatible at all times with one or more linear constraints. The resulting dynamics follows the path of steepest entropy ascent compatible with the constraints. The rate equation is consistent with the Onsager theorem of reciprocity and the fluctuation-dissipation theorem. The mathematical formalism was originally developed to obtain a quantum theoretical unification of mechanics and thermodinamics. It is presented here in a general, non-quantal formulation as a part of an effort to develop tools for the phenomenological treatment of non-equilibrium problems with applications in engineering, biology, sociology, and economics. The rate equation is also extended to include the case of assigned time-dependences of the constraints and the entropy, such as for modeling non-equilibrium energy and entropy exchanges.
Dynamic compressive properties obtained from a split Hopkinson pressure bar test of Boryeong shale
Kang, Minju; Cho, Jung-Woo; Kim, Yang Gon; Park, Jaeyeong; Jeong, Myeong-Sik; Lee, Sunghak
2016-09-01
Dynamic compressive properties of a Boryeong shale were evaluated by using a split Hopkinson pressure bar, and were compared with those of a Hwangdeung granite which is a typical hard rock. The results indicated that the dynamic compressive loading reduced the resistance to fracture. The dynamic compressive strength was lower in the shale than in the granite, and was raised with increasing strain rate by microcracking effect as well as strain rate strengthening effect. Since the number of microcracked fragments increased with increasing strain rate in the shale having laminated weakness planes, the shale showed the better fragmentation performance than the granite at high strain rates. The effect of transversely isotropic plane on compressive strength decreased with increasing strain rate, which was desirable for increasing the fragmentation performance. Thus, the shale can be more reliably applied to industrial areas requiring good fragmentation performance as the striking speed of drilling or hydraulic fracturing machines increased. The present dynamic compressive test effectively evaluated the fragmentation performance as well as compressive strength and strain energy density by controlling the air pressure, and provided an important idea on which rock was more readily fragmented under dynamically processing conditions such as high-speed drilling and blasting.
Study of dynamic pressure roadway supporting scheme under condition of thick composite roof
Wei-Jun WANG; Li-Qiang LUO; Wei-Jian YU; Hai WU; Yan-Si QU
2013-01-01
This paper analyzed the strata behaviors of solid-coal roadway,gob-side entry driving and deformation law of surrounding rock in depth under high stress and thick composite roof based on the dynamic pressure roadway as engineering background in Fengcheng mining area,Jiangxi province.The results,both field measurement andnumerical simulation show that gob-side entry driving results the deformation of coal roadway main wall,however,entity-coal roadway driving results deformation of main roof and floor.The maintenance state of gob-side entry driving is better than entity-coal roadway,this situation is relevant to thick composite roof layered and easy collapse characteristics.At the same time,this paper put forward and proved proper dynamic pressure roadway supporting scheme under the surrounding rock condition and stress environment.
Bifurcation and Nonlinear Dynamic Analysis of Externally Pressurized Double Air Films Bearing System
Cheng-Chi Wang
2014-01-01
Full Text Available This paper studies the chaotic and nonlinear dynamic behaviors of a rigid rotor supported by externally pressurized double air films (EPDAF bearing system. A hybrid numerical method combining the differential transformation method and the finite difference method is used to calculate pressure distribution of EPDAF bearing system and bifurcation phenomenon of rotor center orbits. The results obtained for the orbits of the rotor center are in good agreement with those obtained using the traditional finite difference approach. The results presented summarize the changes which take place in the dynamic behavior of the EPDAF bearing system as the rotor mass and bearing number are increased and therefore provide a useful guideline for the bearing system.
Molecular dynamics study for the melting curve of MgO at high pressure
Liu Zi-Jiang; Cheng Xin-Lu; Zhang Hong; Cai Ling-Cang
2004-01-01
Shell-model molecular dynamics method is used to study the melting temperatures of MgO at elevated temperatures and high pressures using interaction potentials. Equations of state for MgO simulated by molecular dynamics are in good agreement with available experimental data. The pressure dependence of the melting curve of MgO has been calculated. The surface melting and superheating are considered in the correction of experimental data and the calculated values, respectively. The results of corrections are compared with those of previous work. The corrected melting temperature of MgO is consistent with corrected experimental measurements. The melting temperature of MgO up to 140GPa is calculated.
DYNAMIC CHARACTERISTICS OF ELECTRO-HYDRAULIC PROPORTIONAL PRESSURE-FLOW HYBRID VALVE
无
2007-01-01
The structure principles under the flow and pressure working conditions are studied, in order to investigate the dynamic characteristics of the electro-hydraulic proportional pressure-flow hybrid valve. According to the structure principles under the two different working conditions, the transfer functions under such conditions are derived. With the transfer functions, some structure elements that may affect its performance, are investigated, afterwards some principles of optimality and effective methods for improving the dynamic performance of the valve are proposed. The conclusions can be used to instruct engineering applications and products designing. The test results conform to the results of the theoretical analysis and simulation, which proves the correctness of the study and simulation works.
Hossein Sedighikamal; Reza Zarghami
2013-01-01
Pressure fluctuations signals of a lab-scale fluidized bed (15 cm inner diameter and 2 m height) at different superficial gas velocities were measured.Recurrence plot (RP) and recurrence rate (RR),and the simplest variable of recurrence quantification analysis (RQA) were used to analyze the pressure signals.Different patterns observed in RP reflect different dynamic behavior of the system under study.It was also found that the variance of RR (σ2RR) could reveal the peak dominant frequencies (PDF) of different dynamic systems:completely periodic,completely stochastic,Lorenz system,and fluidized bed.The results were compared with power spectral density.Additionally,the diagram of σ2RR provides a new technique for prediction of transition velocity from bubbling to turbulent fluidization regime.
Review of roadway control in soft surrounding rock under dynamic pressure
侯朝炯
2003-01-01
The basic characteristics of the soft rock roadway under the dynamic pressure are analyzed. At the same time, the three fundamental approaches for controlling the surrounding rock are proposed, which are improving the surrounding rock strength, lowering the rock mass stress and selecting the reasonable supporting technology. The research results are elucidated, including the distribution of the surrounding rock plastic zone, the movement and damage of the surrounding rock under the dynamic pressure, controlling the floor heave through reinforcing the roadway walls and corners, the new route to develop the roadway metal supporting technique, the key theory and technique for the bolt supporting in the coal roadway, the performance and prospect of the ZKD high-water-content quick-setting material, and so on. Finally, some personally views are put forward about the roadway metal supporting, bolt supporting, new material and the stress-relief under the high stress condition.
Interplay between lattice dynamics and the low-pressure phase of simple cubic polonium
Zaoui, A.; Belabbes, A.; Ahuja, R.; Ferhat, M.
2011-04-01
Low-pressure structural properties of simple cubic polonium are explored through first-principles density-functional theory based relativistic total energy calculations using pseudopotentials and plane-wave basis set, as well as linear-response theory. We have found that Po undergoes structural phase transition at low pressure near 2 GPa, where the element transforms from simple cubic to a mixture of two trigonal phases namely, hR1 (α=86°) and hR2 (α=97.9°) structures. The lattice dynamics calculations provide strong support for the observed phase transition, and show the dynamical stability (instability) of the hR2 (hR1) phase.
Regime change thresholds in flute-like instruments: influence of the mouth pressure dynamics
Terrien, Soizic; Vergez, Christophe; Fabre, Benoît
2014-01-01
Since they correspond to a jump from a given note to another one, the mouth pressure thresholds leading to regime changes are particularly important quantities in flute-like instruments. In this paper, a comparison of such thresholds between an artificial mouth, an experienced flutist and a non player is provided. It highlights the ability of the experienced player to considerabily shift regime change thresholds, and thus to enlarge its control in terms of nuances and spectrum. Based on recent works on other wind instruments and on the theory of dynamic bifurcations, the hypothe- sis is tested experimentally and numerically that the dynamics of the blowing pressure influences regime change thresholds. The results highlight the strong influence of this parameter on thresholds, suggesting its wide use by experienced musicians. Starting from these observations and from an analysis of a physical model of flute-like instruments, involving numerical continuation methods and Floquet stability analysis, a phenomenolo...
Dahle, H.K.; Celia, M.A.; Hassanizadeh, S.M.; Karlsen, K.H.
2002-07-01
New theories suggest that the relationship between capillary pressure and saturation should be enhanced by a dynamic term that is proportional to the time rate of change of saturation. This so-called dynamic capillary pressure formulation is supported by laboratory experiments, and can be included in various forms of the governing equations for two-phase flow in porous media. An extended model of two-phase flow in porous media may be developed based on fractional flow curves and a total pressure - saturation description that includes the dynamic capillary pressure terms. A dimensionless form of the resulting equation set provides an ideal tool to study the relative importance of the dynamic capillary pressure effect. This equation provides a rich set of mathematical research questions, and numerical solutions to the equation provide insights into the behavior of two-phase immiscible flow. For typical two-phase flow systems, dynamic capillary pressure acts to retard infiltration fronts, with responses dependent on system parameters including boundary conditions. Recent theoretical work suggests that the traditional algebraic relationship between capillary pressure and saturation may be inadequate. Instead, a so-called dynamic capillary pressure formulation is needed, where capillary pressure is defined as a thermodynamic variable, and the difference between phase pressures is only equal to the capillary pressure at equilibrium. Under dynamic conditions, the disequilibrium between phase-pressure differences and the capillary pressure is taken to be proportional to the time rate of change of saturation. A recent study by Hassanizadeh et al. presents experimental evidence, culled from the literature, to support this claim. Numerical simulations using dynamic pore-scale network models and upscaling also support the claim. Hassanizadeh et al. also presented numerical solutions for an enhanced version of Richards' equation that included the dynamic terms. A
Hooker, John C.
1990-01-01
A preliminary study of the applicability of nonlinear dynamic systems analysis techniques to low body negative pressure (LBNP) studies. In particular, the applicability of the heart rate delay map is investigated. It is suggested that the heart rate delay map has potential as a supplemental tool in the assessment of subject performance in LBNP tests and possibly in the determination of susceptibility to cardiovascular deconditioning with spaceflight.
Riemann problem for the zero-pressure flow in gas dynamics
李杰权; 荔炜
2001-01-01
The Riemann problem for zero-pressure flow in gas dynamics in one dimension and two dimensions is investigated. Through studying the generalized Rankine-Hugoniot conditions of delta-shock waves, the one-dimensional Riemann solution is proposed which exhibits four different structures when the initial density involves Dirac measure. For the two-dimensional case, the Riemann solution with two pieces of initial constant states separated at a smooth curve is obtained.
Interactions of Delta Shock Waves for Zero-Pressure Gas Dynamics with Energy Conservation Law
Wei Cai
2016-01-01
Full Text Available We study the interactions of delta shock waves and vacuum states for the system of conservation laws of mass, momentum, and energy in zero-pressure gas dynamics. The Riemann problems with initial data of three piecewise constant states are solved case by case, and four different configurations of Riemann solutions are constructed. Furthermore, the numerical simulations completely coinciding with theoretical analysis are shown.
SOME EXACT SOLUTIONS OF 3-DIMENSIONAL ZERO-PRESSURE GAS DYNAMICS SYSTEM
K.T.Joseph; Manas R. Sahoo
2011-01-01
The 3-dimensional zero-pressure gas dynamics system appears in the modeling for the large scale structure formation in the universe.The aim of this paper is to construct spherically symmetric solutions to the system.The radial component of the velocity and density satisfy a simpler one dimensional problem.First we construct explicit solutions of this one dimensional case with initial and boundary conditions.Then we get special radial solutions with different behaviours at the origin.
Vedsted, Pernille; Blangsted, Anne Katrine; Søgaard, Karen
2006-01-01
Dynamic muscle contractions have been shown to cause greater energy turnover and fatigue than static contractions performed at a corresponding force level. Therefore, we hypothesized that: (1) electro- (EMG) and mechanomyography (MMG), intramuscular pressure (IMP), and reduction in muscle oxygen...... similar in spite of major differences in the MMG and EMG responses of the muscle during contraction periods. This may relate to the surprisingly lower IMP in DYN than IST....
Li, Y.D., E-mail: ydli@ustc.edu [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Lu, Q.L. [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Wang, C.C., E-mail: ccwang@ahu.edu.cn [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Huang, S.G. [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Liu, C.S. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China)
2013-01-01
Based on the second-moment approximation of tight-binding scheme, constant-pressure molecular dynamics simulations are performed for liquid Cu during the glass transition under different pressures. By means of pair analysis technique and bond orientational order analysis we find that the dominant bond pairs are those related to fcc and hcp crystalline order not those representing icosahedral short-range order (ISRO) when the systems enter into glass transition region. Although these two kinds of bond pairs compete with each other, the system tends towards a mixture of crystalline bond pairs during glass formation. The effect on various bond pairs brought about by higher pressure is much less for liquids than for glasses. The experimental observation of a shoulder on the second peak of the structure factor for supercooled liquids might not merely attribute to ISRO, since supercooled liquid Cu exhibits such a shoulder, but does not display an enhanced icosahedral symmetry.
Molecular dynamics simulations of water on a hydrophilic silica surface at high air pressures
Zambrano, H.A.; Walther, Jens Honore; Jaffe, R.L.
2014-01-01
of air in water at different pressures. Using the calibrated force field, we conduct MD simulations to study the interface between a hydrophilic silica substrate and water surrounded by air at different pressures. We find that the static water contact angle is independent of the air pressure imposed......Wepresent a force field forMolecular Dynamics (MD) simulations ofwater and air in contactwith an amorphous silica surface. We calibrate the interactions of each species present in the systemusing dedicated criteria such as the contact angle of a water droplet on a silica surface, and the solubility...... on the system. Our simulations reveal the presence of a nanometer thick layer of gas at the water–silica interface. We believe that this gas layer could promote nucleation and stabilization of surface nanobubbles at amorphous silica surfaces. © 2014 Elsevier B.V. All rights reserved....
Theory for planetary exospheres: I. Radiation pressure effect on dynamical trajectories
Beth, Arnaud; Toublanc, Dominique; Dandouras, Iannis; Mazelle, Christian
2015-01-01
The planetary exospheres are poorly known in their outer parts, since the neutral densities are low compared with the instruments detection capabilities. The exospheric models are thus often the main source of information at such high altitudes. We present a new way to take into account analytically the additional effect of the radiation pressure on planetary exospheres. In a series of papers, we present with an Hamiltonian approach the effect of the radiation pressure on dynamical trajectories, density profiles and escaping thermal flux. Our work is a generalization of the study by Bishop and Chamberlain (1989). In this first paper, we present the complete exact solutions of particles trajectories, which are not conics, under the influence of the solar radiation pressure. This problem was recently partly solved by Lantoine and Russell (2011) and Biscani and Izzo (2014). We give here the full set of solutions, including solutions not previously derived, as well as simpler formulations for previously known cas...
The dynamic properties of shock-waves formed during laser ablation at sub-atmospheric pressures
Kapitan, D.; Coutts, D. W.
2002-01-01
The Sedov-Taylor-von Neumann (STN) theory has been shown to accurately describe the dynamic properties of shock-waves generated during pulsed-laser ablation of solid aluminium targets at visible wavelengths (510/578 nm) with 40 ns pulses with energies up to 3.5 mJ. A ballistic pendulum is used to measure the integrated recoil pressure in various inert atmospheres (He, Ne, Ar, Kr, Xe, N2, CO2, SF6) with pressures of 10-2 - 103 mbar. This recoil momentum is found to scale linearly with the background gas pressure P1 and with the square root of the molecular weight M1. More interestingly, the scaling with the ratio of heat capacities γ is verified to be a monotonically increasing function dependent on the form factor of the shock-wave. The validity of a modified STN theory which accounts for the piston mass is assessed.
A new cable truss support system for coal roadways affected by dynamic pressure
Hong Yan; Fulian He
2012-01-01
The support of coal roadways is seriously affected by intense dynamic pressures.This can lead to problems with large deformation of the roof and the two side walls of coal roadways.Rapid convergence of the walls and roof,a high damage rate to the bolts and cables,or even abrupt roof collapse or rib spalling can occur during the service period of these coal roadways.Analyzing the main support measures used in China leads to a proposed new cable truss supporting system.Thorough study of the entire structure shows the superiority of this design for roadways suffering under dynamic pressure.A corresponding mechanical model of the rock surrounding the cable truss system is described in this paper and formulas for calculating pre-tightening forces of the truss cable,and the minimum anchoring forces,were deduced.The new support system was applied to a typical roadway affected by intensive dynamic pressure that is located in the Xinyuan Coal Mine.The results show that the largest subsidence of the roof was 97 mm,the convergence of the two sides was less than 248 mm,and the average depth of the loose,fractured layer was only 6.12 mm.This proves that the new support system is feasible and effective.
Schiffer, Christian; Nielsen, Søren Bom
2016-08-01
With convergent plate boundaries at some distance, the sources of the lithospheric stress field of the North Atlantic Realm are mainly mantle tractions at the base of the lithosphere, lithospheric density structure and topography. Given this, we estimate horizontal deviatoric stresses using a well-established thin sheet model in a global finite element representation. We adjust the lithospheric thickness and the sub-lithospheric pressure iteratively, comparing modelled in plane stress with the observations of the World Stress Map. We find that an anomalous mantle pressure associated with the Iceland and Azores melt anomalies, as well as topography are able to explain the general pattern of the principle horizontal stress directions. The Iceland melt anomaly overprints the classic ridge push perpendicular to the Mid Atlantic ridge and affects the conjugate passive margins in East Greenland more than in western Scandinavia. The dynamic support of topography shows a distinct maximum of c. 1000 m in Iceland and amounts Greenland. Considering that large areas of the North Atlantic Realm have been estimated to be sub-aerial during the time of break-up, two components of dynamic topography seem to have affected the area: a short-lived, which affected a wider area along the rift system and quickly dissipated after break-up, and a more durable in the close vicinity of Iceland. This is consistent with the appearance of a buoyancy anomaly at the base of the North Atlantic lithosphere at or slightly before continental breakup, relatively fast dissipation of the fringes of this, and continued melt generation below Iceland.
Dynamics of liquid helium boil-off experiments with a step change in pressure
Cha, Y. S.; Niemann, R. C.; Hull, J. R.
The results of dynamic analysis of the effect of pressure variations during helium boil-off experiments are presented. A general solution of the diffusion equation with a time-dependent boundary condition is employed to describe the dynamic response of the liquid helium system under variable pressure conditions, and a solution is obtained for the special case when the system is subjected to a step change in pressure. The calculated temperature response of the liquid indicates that most of the experiments were not likely to have reached equilibrium as a result of the low thermal diffusivity of liquid helium. The initial rate of evaporation or condensation is large, and the rate decreases sharply with time. A method is proposed to account for the transient effect that is observed during calculation of the heat loss rate from a helium boil-off experiment. By assuming that there is no mixing at all, the present analysis provides an estimate of the upper (condensation) or lower (evaporation) bound of the heat loss rate as a result of a pressure increase or decrease in the system. A previously reported equilibrium analysis is expected to apply to situations where complete mixing occurred in the bulk liquid and provides the opposite limits.
Golub, M.; Lehofer, B.; Martinez, N.; Ollivier, J.; Kohlbrecher, J.; Prassl, R.; Peters, J.
2017-04-01
Lipid composition of human low-density lipoprotein (LDL) and its physicochemical characteristics are relevant for proper functioning of lipid transport in the blood circulation. To explore dynamical and structural features of LDL particles with either a normal or a triglyceride-rich lipid composition we combined coherent and incoherent neutron scattering methods. The investigations were carried out under high hydrostatic pressure (HHP), which is a versatile tool to study the physicochemical behavior of biomolecules in solution at a molecular level. Within both neutron techniques we applied HHP to probe the shape and degree of freedom of the possible motions (within the time windows of 15 and 100 ps) and consequently the flexibility of LDL particles. We found that HHP does not change the types of motion in LDL, but influences the portion of motions participating. Contrary to our assumption that lipoprotein particles, like membranes, are highly sensitive to pressure we determined that LDL copes surprisingly well with high pressure conditions, although the lipid composition, particularly the triglyceride content of the particles, impacts the molecular dynamics and shape arrangement of LDL under pressure.
Dynamic Response of High-Pressure Riser of Deepwater SBOP System
Kanhua Su
2012-08-01
Full Text Available The application of surface blowout preventer (SBOP drilling system in deepwater environments has been demonstrated that it can save operation cost and time. The high pressure small diameter casing plays the role of the conventional riser and bears the complex loading caused by the wave and current force and drilling platform motion. The coupled quasi-static and uncoupled dynamic analysis models of deepwater SBOP drilling system were established. The analysis results indicate that the uncoupled method without consider the lateral offset on the end of the high pressure riser nearly no affection to the riser analysis. However, the uncoupled method has a certain impact on the mechanical analysis of the subsea wellhead and the casing string under mudline. The lateral offset of the high pressure riser changes greatly in the different times, the bending moment of the upper and lower stress joint of riser is bigger. The platform long-term drift has a greater impact on the dynamic response analysis of the high pressure riser of SBOP system for deepwater drilling.
Chaotic dynamic characteristics of pressure fluctuation signals in hydro-turbine
Su, Wen Tao; An, Shi [School of Management, Harbin Institute of Technology, Harbin (China); Li, Xiao Bin; Lan, Chao Feng; Li, Feng Chen [School of Energy Science and Engineering, Harbin Institute of Technology, Harbin (China); Wang, Jian Sheng [Ministry of Education of China, Tianjin (China)
2016-11-15
The pressure fluctuation characteristics in a Francis hydro-turbine running at partial flow conditions were studied based on the chaotic dynamic methods. Firstly, the experimental data of pressure fluctuations in the draft tube at various flow conditions was de-noised using lifting wavelet transformation, then, for the de-noised signals, their spectrum distribution on the frequency domain, the energy variation and the energy partition accounting for the total energy was calculated. Hereby, for the flow conditions ranging from no cavitation to severe cavitation, the chaos dynamic features of fluctuation signals were analyzed, including the temporal-frequency distribution, phase trajectory, Lyapunov exponent and Poincaré map etc. It is revealed that, the main energy of pressure fluctuations in the draft tube locates at low-frequency region. As the cavitation grows, the amplitude of power spectrum at frequency domain becomes larger. For all the flow conditions, all the maximal Lyapunov exponents are larger than zero, and they increase with the cavitation level. Therefore, it is believed that there indeed exist the chaotic attractors in the pressure fluctuation signals for a hydro-turbine.
Nishida, S; Surblys, D; Yamaguchi, Y; Kuroda, K; Kagawa, M; Nakajima, T; Fujimura, H
2014-02-21
Molecular dynamics simulations of a nanoscale liquid droplet on a solid surface are carried out in order to examine the pressure tensor field around the multiphase interfaces, and to explore the validity of Young's equation. By applying the virial theorem to a hemicylindrical droplet consisting of argon molecules on a solid surface, two-dimensional distribution of the pressure tensor is obtained. Tensile principal pressure tangential to the interface is observed around the liquid-vapor transition layer, while both tensile and compressive principal pressure tangential to the interface exists around the solid-liquid transition layer due to the inhomogeneous density distribution. The two features intermix inside the overlap region between the transition layers at the contact line. The contact angle is evaluated by using a contour line of the maximum principal pressure difference. The interfacial tensions are calculated by using Bakker's equation and Young-Laplace equation to the pressure tensor distribution. The relation between measured contact angle and calculated interfacial tensions turns out to be consistent with Young's equation, which is known as the description of the force balance at the three-phase interface.
Sun, Tao; Zhang, Dong-Bo; Wentzcovitch, Renata M.
2014-03-01
The stability of cubic CaSiO3 perovskite (CaPv) at high temperatures and pressures is investigated by vibrational normal-mode analysis. We compute power spectra of mode autocorrelation functions using a recently developed hybrid approach combining ab initio molecular dynamics with lattice dynamics. These power spectra, together with the probability distributions of atomic displacements, indicate that cubic CaPv is stabilized at T ˜600 K and P ˜ 26 GPa. We then utilize the concept of phonon quasiparticles to characterize the vibrational properties of cubic CaPv at high temperature and obtain anharmonic phonon dispersions through the whole Brillouin zone. Such temperature-dependent phonon dispersions pave the way for more accurate calculations of free-energy, thermodynamic, and thermoelastic properties of cubic CaPv at Earth's lower mantle conditions.
Dynamic High Pressure Study of Chemistry and Physics of Molecular Materials
Jezowski, Sebastian Ryszard
Both temperature and pressure control and influence the packing of molecules in crystalline phases. Our molecular simulations indicate that at ambient pressure, the cubic polymorph of tetracyanoethylene, TCNE, is the energetically stable form up to ˜ 160 K. The observed transition from the cubic to the monoclinic polymorph occurs however only at temperatures above ˜ 318 K due to the large transition barrier. The temperature-induced phase transition in TCNE studied with high-resolution IR spectroscopy is explained in terms of the increased vibrational entropy in the crystals of the monoclinic polymorph. Based upon the inverted design of the Merril-Bassett Diamond Anvil Cell, an improved, second generation dynamic Diamond Anvil Cell was developed. Based on the fluorescence of ruby crystals, we were able to demonstrate that the pressure variation range can be further increased at least up to 7 kbar and that the dynamic pressure compression of up to 1400 GPa/s can be achieved. A new class of mechanophoric system, bis-anthracene, BA, and its photoisomer, PI, is shown to respond reversibly to a mild, static pressure induced by a Diamond Anvil Cell as well as to shear deformation based on absorption spectroscopic measurements. The forward reaction occurs upon illumination with light while the back-reaction may be accelerated upon heating or mechanical stress, coupled to a rehybridization on four equivalent carbon atoms. It is an intriguing result as high pressure stabilizes the photodimerized species in related systems. Our molecular volume simulations ruled out significant differences in the volumes between bis-anthracene and its photoisomer. Kinetic absorption measurements at several different pressures reveal a negative volume of activation in the exothermic back-reaction at room temperature. Through a series of temperature-dependent kinetic measurements it is shown that the barrier of activation for the back-reaction is reduced by more than an order of magnitude at
R. Spahni
2013-06-01
Full Text Available The development of northern high-latitude peatlands played an important role in the carbon (C balance of the land biosphere since the Last Glacial Maximum (LGM. At present, carbon storage in northern peatlands is substantial and estimated to be 500 ± 100 Pg C (1 Pg C = 1015 g C. Here, we develop and apply a peatland module embedded in a dynamic global vegetation and land surface process model (LPX-Bern 1.0. The peatland module features a dynamic nitrogen cycle, a dynamic C transfer between peatland acrotelm (upper oxic layer and catotelm (deep anoxic layer, hydrology- and temperature-dependent respiration rates, and peatland specific plant functional types. Nitrogen limitation down-regulates average modern net primary productivity over peatlands by about half. Decadal acrotelm-to-catotelm C fluxes vary between −20 and +50 g C m−2 yr−1 over the Holocene. Key model parameters are calibrated with reconstructed peat accumulation rates from peat-core data. The model reproduces the major features of the peat core data and of the observation-based modern circumpolar soil carbon distribution. Results from a set of simulations for possible evolutions of northern peat development and areal extent show that soil C stocks in modern peatlands increased by 365–550 Pg C since the LGM, of which 175–272 Pg C accumulated between 11 and 5 kyr BP. Furthermore, our simulations suggest a persistent C sequestration rate of 35–50 Pg C per 1000 yr in present-day peatlands under current climate conditions, and that this C sink could either sustain or turn towards a source by 2100 AD depending on climate trajectories as projected for different representative greenhouse gas concentration pathways.
LU Xiao-bing; WANG Shu-yun; ZHANG Jian-hong; SUN Guo-liang; SHI Zhong-min
2005-01-01
Centrifuge experiments are carried out to investigate the responses of suction bucket foundations under horizontal dynamic loading. The effects of loading amplitude, the size of the bucket and the structural weight on the dynamic responses are investigated. It is shown that, when the loading amplitude is over a critical value, the sand at the upper part around the bucket softens or even liquefies. The liquefaction index (excess pore pressure divided by initial effective stress. In this paper, the developmental degree of excess pore pressure is described by liquefaction index) decreases from the upper part to the lower part of the sand foundation in the vertical direction and decreases from near to far away from the bucket′s side wall in the horizontal direction. Large settlements of the bucket and the sand around the bucket are induced by the horizontal dynamic loading. The dynamic responses of the bucket of a smaller height (when the diameter is the same) are heavier. A cyclic crack some distance near the bucket occurs in the sand.
Algwari, Q. Th. [Centre for Plasma Physics, School of Maths and Physics, Queen' s University Belfast, University Road, Belfast, Northern Ireland BT7 1NN (United Kingdom); Electronic Department, College of Electronics Engineering, Mosul University, Mosul 41002 (Iraq); O' Connell, D. [Centre for Plasma Physics, School of Maths and Physics, Queen' s University Belfast, University Road, Belfast, Northern Ireland BT7 1NN (United Kingdom); York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)
2011-09-19
The excitation dynamics within the main plasma production region and the plasma jets of a kHz atmospheric pressure dielectric barrier discharge (DBD) jet operated in helium was investigated. Within the dielectric tube, the plasma ignites as a streamer-type discharge. Plasma jets are emitted from both the powered and grounded electrode end; their dynamics are compared and contrasted. Ignition of these jets are quite different; the jet emitted from the powered electrode is ignited with a slight time delay to plasma ignition inside the dielectric tube, while breakdown of the jet at the grounded electrode end is from charging of the dielectric and is therefore dependent on plasma production and transport within the dielectric tube. Present streamer theories can explain these dynamics.
Feng, S. D.; Jiao, W.; Jing, Q.; Qi, L.; Pan, S. P.; Li, G.; Ma, M. Z.; Wang, W. H.; Liu, R. P.
2016-11-01
Structural evolution in nanoscale Cu50Zr50 metallic glasses during high-pressure torsion is investigated using molecular dynamics simulations. Results show that the strong cooperation of shear transformations can be realized by high-pressure torsion in nanoscale Cu50Zr50 metallic glasses at room temperature. It is further shown that high-pressure torsion could prompt atoms to possess lower five-fold symmetries and higher potential energies, making them more likely to participate in shear transformations. Meanwhile, a higher torsion period leads to a greater degree of forced cooperative flow. And the pronounced forced cooperative flow at room temperature under high-pressure torsion permits the study of the shear transformation, its activation and characteristics, and its relationship to the deformations behaviors. This research not only provides an important platform for probing the atomic-level understanding of the fundamental mechanisms of high-pressure torsion in metallic glasses, but also leads to higher stresses and homogeneous flow near lower temperatures which is impossible previously.
Kavanaugh, J. L.
2009-03-01
In order to determine whether brief excursions, or "pulses," in subglacial water pressure inferred by Kavanaugh and Clarke (2000, 2001) occur, water pressures at the bed of Trapridge Glacier, Yukon, Canada, were recorded using an interface board that continuously monitored a pressure transducer. During the 231 day period between 16 July 2005 and 4 March 2006, more than 7000 pressure pulses were recorded, with magnitudes reaching nearly 3 times the flotation value. Comparison of the pressure pulse record with those from a number of other instruments installed in this soft-bedded glacier indicates that these pulses are generated by stress transients that compress the water within the borehole; calculations suggest that these transients are as large as 75 times the nominal driving stress. Both the magnitudes and interevent times for these pulses are well fitted by power law distributions that are remarkably similar to those exhibited by earthquakes. These similarities suggest that the ice-bed interface of a soft-bedded glacier behaves much like an earthquake fault and raises the possibility that such glaciers self-organize to a critical state. Further evidence for self-organized criticality (SOC) of soft-bedded glaciers is suggested by an examination of well-known ice dynamical properties and the rheological properties of subglacial sediments, which suggests that SOC might be a natural consequence of the rate-independent behavior of subglacial sediments.
Laser-Based Dynamic Compression of Geological Materials to Ultrahigh Pressures
Duffy, T. S.
2015-12-01
Laser-based dynamic compression provides new opportunities to study the structures and properties of geological materials to ultrahigh pressure conditions reaching 1 terapascal and beyond. By controlling the shape and duration of the incident laser pulse, either shock or ramp (shockless) loading can be produced. Samples can be compressed for ~10s of nanoseconds on spatial scales of ~1 millimeter. Diagnostics include velocity interferometry from which the stress-density response of the material can be determined and X-ray diffraction from which lattice-level structural information is obtained. Our experiments are being carried out at a suite of facilities including the Omega Laser (U. of Rochester), Linear Coherent Light Source (LCLS), and National Ignition Facility (Livermore). Using ramp compression we have constrained pressure-density states in a variety of materials including iron, magnesium oxide, and carbon. X-ray diffraction has been used as a diagnostic to probe the B1-B2 phase transition in MgO under both ramp and shock loading to multi-megabar pressures. We have also examined this same phase transition at more modest pressures on sodium chloride at the LCLS, observing both the B1-B2 transition upon compression and its back transformation upon release. X-ray diffraction measurements have also been used to study the melting curves and high-pressure phase stability of transition metals and alloys, including compositions relevant to the cores of Earth and super-Earth planets.
Zhang, Hong
2016-01-01
Saturation overshoot and pressure overshoot are studied by incorporating dynamic capillary pressure, capillary pressure hysteresis and hysteretic dynamic coefficient with a traditional fractional flow equation. Using the method of lines, the discretizations are constructed by applying Castillo-Grone's mimetic operators in the space direction and explicit trapezoidal integrator in the time direction. Convergence tests and conservation property of the schemes are presented. Computed profiles capture both the saturation overshoot and pressure overshoot phenomena. Comparisons between numerical results and experiments illustrate the effectiveness and different features of the models.
Eikje, Natalja Skrebova; Arase, Seiji
2008-02-01
The local microcirculatory dynamics underlying phenomenon of urticarial dermographism (UD) are not yet sufficiently elucidated in dermatological patients. A fiber optic laser Doppler flowmeter (LDF) was used to monitor skin blood flow (SBF) changes on the back of the patients with UD before and after application of the series of pressure stimuli (9.8×10 4, 14.7×10 4, 19.6×10 4 and 24.5×10 4 Pa). All patients acted as self-controls to assess their disease activity by means of SBF values based on response to pressure stimuli before and after treatment with antihistamines, when compared to baseline SBF. Throughout 30 minutes evaluation inter-subject SBF values at pressure-tested sites were noticeably distinguished as high, moderate and low. By LDF we could differentiate the highest development of vascular dynamics after 5 minutes, coming back to normal within about 30 minutes in one group of patients, and the vascular dynamics reaching its maximum in 15 minutes, but with no fade after 30 minutes, in another group of patients. All treatment regimens in both groups of patients by LDF produced a measurable reduction already during 1-2 days of therapy, accompanied by a reduction in SBF baseline values in patients with severe and moderate symptoms of UD.
Noda, Hiroyuki; Shimamoto, Toshihiko
2015-04-01
Fault mechanical behavior is presumably dictated by a pressure-sensitive friction law in the brittle regime where cataclastic deformation dominates, and by a pressure-insensitive flow law in the plastic regime where milonytes are generated. A fault constitutive law in the transitional regime is of great importance in considering earthquake cycles as evidenced by field observations of repeating brittle and ductile deformations [e.g., Sibson 1980]. Shimamoto and Noda [2014] proposed an empirical method of connecting the friction law and the flow law without introducing a new parameter, and demonstrated 2-D dynamic earthquake sequence simulations for a strike-slip fault [e.g., Lapusta et al., 2000] with the friction-to-flow law. A logarithmic rate- and state-dependent friction law (aging law) and a rate- and state-dependent flow law (power law) [Noda and Shimamoto, 2010] with a quartzite steady-state flow law (power exponent n = 4) [Hirth et al., 2001] were adopted for the friction law and the flow law, respectively. Our numerical models are realization of conceptual fault models [e.g., Scholz, 1988]. "Christmas tree" stress profiles appear as a result of evolution of the system, and fluctuate with time. During the interseismic periods, creep fronts penetrated into the locked depth, slow slip events were generated, and then nucleation of dynamic rupture took place either in the shallower or deeper creeping region. The dynamic ruptures spanned the locked depth, reaching the ground surface and extending downwards even deeper than the depth of maximum pre-stress where the deformation mode was in the transitional regime preseismically where S-C mylonitic texture was expected [Shimamoto, 1989]. The coseismic deformation was in the frictional regime because the pure flow law predicts tremendously high flow stress at high strain rate and "the weaker wins". Our simulations reproduced repeating overprint of brittle and ductile deformations. We attempt here to include pressure
Weippert, Matthias; Behrens, Kristin; Rieger, Annika; Stoll, Regina; Kreuzfeld, Steffi
2013-01-01
Aim was to elucidate autonomic responses to dynamic and static (isometric) exercise of the lower limbs eliciting the same moderate heart rate (HR) response. 23 males performed two kinds of voluntary exercise in a supine position at similar heart rates: static exercise (SE) of the lower limbs (static leg press) and dynamic exercise (DE) of the lower limbs (cycling). Subjective effort, systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), rate pressure product (RPP) and the time between consecutive heart beats (RR-intervals) were measured. Time-domain (SDNN, RMSSD), frequency-domain (power in the low and high frequency band (LFP, HFP)) and geometric measures (SD1, SD2) as well as non-linear measures of regularity (approximate entropy (ApEn), sample entropy (SampEn) and correlation dimension D2) were calculated. Although HR was similar during both exercise conditions (88±10 bpm), subjective effort, SBP, DBP, MAP and RPP were significantly enhanced during SE. HRV indicators representing overall variability (SDNN, SD 2) and vagal modulated variability (RMSSD, HFP, SD 1) were increased. LFP, thought to be modulated by both autonomic branches, tended to be higher during SE. ApEn and SampEn were decreased whereas D2 was enhanced during SE. It can be concluded that autonomic control processes during SE and DE were qualitatively different despite similar heart rate levels. The differences were reflected by blood pressure and HRV indices. HRV-measures indicated a stronger vagal cardiac activity during SE, while blood pressure response indicated a stronger sympathetic efferent activity to the vessels. The elevated vagal cardiac activity during SE might be a response mechanism, compensating a possible co-activation of sympathetic cardiac efferents, as HR and LF/HF was similar and LFP tended to be higher. However, this conclusion must be drawn cautiously as there is no HRV-marker reflecting "pure" sympathetic cardiac activity.
Pore-pressure sensitivities to dynamic strains: observations in active tectonic regions
Barbour, Andrew J.
2015-01-01
Triggered seismicity arising from dynamic stresses is often explained by the Mohr-Coulomb failure criterion, where elevated pore pressures reduce the effective strength of faults in fluid-saturated rock. The seismic response of a fluid-rock system naturally depends on its hydro-mechanical properties, but accurately assessing how pore-fluid pressure responds to applied stress over large scales in situ remains a challenging task; hence, spatial variations in response are not well understood, especially around active faults. Here I analyze previously unutilized records of dynamic strain and pore-pressure from regional and teleseismic earthquakes at Plate Boundary Observatory (PBO) stations from 2006 through 2012 to investigate variations in response along the Pacific/North American tectonic plate boundary. I find robust scaling-response coefficients between excess pore pressure and dynamic strain at each station that are spatially correlated: around the San Andreas and San Jacinto fault systems, the response is lowest in regions of the crust undergoing the highest rates of secular shear strain. PBO stations in the Parkfield instrument cluster are at comparable distances to the San Andreas fault (SAF), and spatial variations there follow patterns in dextral creep rates along the fault, with the highest response in the actively creeping section, which is consistent with a narrowing zone of strain accumulation seen in geodetic velocity profiles. At stations in the San Juan Bautista (SJB) and Anza instrument clusters, the response depends non-linearly on the inverse fault-perpendicular distance, with the response decreasing towards the fault; the SJB cluster is at the northern transition from creeping-to-locked behavior along the SAF, where creep rates are at moderate to low levels, and the Anza cluster is around the San Jacinto fault, where to date there have been no statistically significant creep rates observed at the surface. These results suggest that the strength
Berg, Ronan M G; Plovsing, Ronni R; Bailey, Damian M; Holstein-Rathlou, Niels-Henrik; Møller, Kirsten
2016-11-01
Previous studies have demonstrated that dynamic cerebral autoregulation to spontaneous fluctuations in blood pressure is enhanced following lipopolysaccharide (LPS) infusion, a human experimental model of early sepsis, whereas by contrast it is impaired in patients with severe sepsis or septic shock. In this study, we hypothesized that this pattern of response would be identical during induced changes in blood pressure. Dynamic cerebral autoregulation was assessed in nine healthy volunteers and six septic patients. The healthy volunteers underwent a 4-h intravenous infusion of LPS (total dose: 2 ng kg(-1) ). Mean arterial blood pressure (MAP, arterial transducer) and middle cerebral artery blood flow velocity (MCAv, transcranial Doppler ultrasound) were recorded continuously during thigh-cuff deflation-induced changes in MAP for the determination of a modified rate of regulation (RoR). This was performed before and after LPS infusion in healthy volunteers, and within 72 h following clinical diagnosis of sepsis in patients. In healthy volunteers, thigh-cuff deflation caused a MAP reduction of 16 (13-20) % at baseline and 18 (16-20) % after LPS, while the MAP reduction was 12 (11-13) % in patients (Psepsis, they remain inconclusive with regard to more advanced stages of disease, because thigh-cuff deflation failed to induce sufficient MAP reductions in patients. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.
Nonlinear fractal dynamics of human colonic pressure activity based upon the box-counting method.
Yan, Rongguo; Guo, Xudong
2013-01-01
The computational fractal dimension of human colonic pressure activity acquired by a telemetric capsule robot under normal physiological conditions was studied using the box-counting method. The fractal dimension is a numeric value that quantifies to measure how rough the signal is from nonlinear dynamics, rather than its amplitude or other linear statistical features. The colonic pressure activities from the healthy subject during three typical periods were analysed. The results showed that the activity might be fractal with a non-integer fractal dimension after it being integrated over time using the cumsum method, which was never revealed before. Moreover, the activity (after it being integrated) acquired soon after wakening up was the roughest (also the most complex one) with the largest fractal dimension, closely followed by that acquired during sleep with that acquired long time after awakening up (in the daytime) ranking third with the smallest fractal dimension. Fractal estimation might provide a new method to learn the nonlinear dynamics of human gastrointestinal pressure recordings.
Relationship between muscle stress and intramuscular pressure during dynamic muscle contractions.
Ward, Samuel R; Davis, Jennifer; Kaufman, Kenton R; Lieber, Richard L
2007-09-01
Intramuscular pressure (IMP) has been used to estimate muscle stress indirectly. However, the ability of this technique to estimate muscle stress under dynamic conditions is poorly characterized. Therefore, the purpose of this study was to determine the extent to which IMP is a valid surrogate for muscle stress during dynamic contractions. IMP and muscle stress were compared under steady-state isotonic conditions and during complex dynamic length changes. During concentric contractions the shape of the IMP-velocity curve mimicked the basic shape of the force-velocity curve but with much higher variability. For eccentric contractions, a precipitous drop in IMP was observed despite increased muscle stress. The dissociation between muscle stress and IMP during dynamic contractions was partially explained by sensor movement. When the muscle was not moving, IMP explained 89% +/- 5% of the variance in muscle force. However, when transducer movement occurred the linear relationship between IMP and stress was no longer observed. These findings demonstrate the difficulty in interpreting IMP under dynamic conditions when sensor movement occurs. They also illustrate the need to control transducer movement if muscle stress is to be inferred from IMP measurements such as might be desired during clinical gait testing.
Vos, J. J.; Kalmar, A. F.; Struys, M. M. R. F.; Wietasch, J. K. G.; Hendriks, H. G. D.; Scheeren, T. W. L.
2013-01-01
Dynamic preload variables to predict fluid responsiveness are based either on the arterial pressure waveform (APW) or on the plethysmographic waveform (PW). We compared the ability of APW-based variations in stroke volume (SVV) and pulse pressure (PPV) and of PW-based plethysmographic variability in
Vos, J. J.; Kalmar, A. F.; Struys, M. M. R. F.; Wietasch, J. K. G.; Hendriks, H. G. D.; Scheeren, T. W. L.
Dynamic preload variables to predict fluid responsiveness are based either on the arterial pressure waveform (APW) or on the plethysmographic waveform (PW). We compared the ability of APW-based variations in stroke volume (SVV) and pulse pressure (PPV) and of PW-based plethysmographic variability
Vos, J. J.; Kalmar, A. F.; Struys, M. M. R. F.; Wietasch, J. K. G.; Hendriks, H. G. D.; Scheeren, T. W. L.
2013-01-01
Dynamic preload variables to predict fluid responsiveness are based either on the arterial pressure waveform (APW) or on the plethysmographic waveform (PW). We compared the ability of APW-based variations in stroke volume (SVV) and pulse pressure (PPV) and of PW-based plethysmographic variability in
On the impact of radiation pressure on the dynamics and inner structure of dusty wind-driven shells
Martinez-Gonzalez, Sergio; Tenorio-Tagle, Guillermo
2014-01-01
Massive young stellar clusters are strong sources of radiation and mechanical energy. Their powerful winds and radiation pressure sweep-up interstellar gas into thin expanding shells which trap the ionizing radiation produced by the central clusters affecting the dynamics and the distribution of their ionized gas. Here we continue our comparison of the star cluster winds and radiation pressure effects on the dynamics of shells around young massive clusters. We calculate the impact that radiation pressure has on the distribution of matter and thermal pressure within such shells as well as on the density weighted ionization parameter $U_w$ and put our results on the diagnostic diagram which allows one to discriminate between the wind-dominated and radiation-dominated regimes. We found that model predicted values of the ionization parameter agree well with typical values found in local starburst galaxies. Radiation pressure may affect the inner structure and the dynamics of wind-driven shells only at the earlies...
Vérin, E; Similowski, T; Sériès, F
2003-01-01
Continuous positive airway pressure (CPAP) is the main treatment of the obstructive sleep apnoea syndrome (OSAS). We assessed its effects on the upper airway (UA) dynamics in response to bilateral anterior magnetic phrenic nerve stimulation (BAMPS) in 17 awake untreated OSAS patients (15 males; 52 +/- 7 years) whose effective CPAP (P(eff)) had been determined beforehand by a conventional titration sleep study. All twitch-related inspirations were flow-limited, flow first rising to a maximum (V(Imax)), then decreasing to a minimum (V(Imin)), and then increasing again (M-shaped pattern). Up to V(Imin), the relationship between driving pressure (P(d)) and flow (V) could adequately be fitted to a polynomial regression model (V = k(1)P(d) + k(2)P(d)(2); r(2) = 0.71-0.98, P < 0.0001). At atmospheric pressure V(Imax) was 700 +/- 377 ml s(-1), V(Imin) was 458 +/- 306 ml s(-1), k(1) was 154.5 +/- 63.9 ml s(-1) (cmH(2)O)(-1), and k(2) was 10.7 +/- 7.3 ml s(-1) (cmH(2)O)(-1). CPAP significantly increased V(Imax) and V(Imin) (peak values 1007 +/- 332 ml and 837 +/- 264 ml s(-1), respectively) as well as k(1) and k(2) (peak values 300.9 +/- 178.2 ml s(-1) (cmH(2)O)(-1) and 55.2 +/- 65.3 ml s(-1) (cmH(2)O)(-1), respectively). With increasing CPAP, k(1)/k(2) increased up to a peak value before decreasing. We defined as P(eff,stim) the CPAP value corresponding to the highest k(1)/k(2) value. P(eff,stim) was correlated with P(eff) (P(eff) = 7.0 +/- 2.0; P(eff,stim) = 6.4 +/- 2.6 cmH(2)O; r = 0.886; 95 % CI 0.696-0.960, P < 0.001). We conclude that CPAP improves UA dynamics in OSAS and that the therapeutic CPAP to apply can be predicted during wakefulness using BAMPS.
Wind Pressure Distribution and Wind-induced Dynamic Response for Spatial Groined Latticed Vaults
MA Jun; ZHOU Dai; BAO Yan
2008-01-01
The wind pressure distribution and wind-induced vibration responses of long-span spatial groined latticed vaults (SGLVs) were numerically simulated, which always are ones of the most important problems in the structural wind resistance design. Incompressible visco-fluid model was introduced, and the standard k-εtwo equation model and semi-implicit method for pressure linked equation (SIMPLE) were used to describe the flow turbulence. Furthermore, the structural dynamic equation was set up, which is solved by Newmark-β method. And several sort of wind-induced vibration coefficients such as the wind-induced vibration coefficient corresponding to the nodal displacement responses and wind loads were suggested. In the numerical simulation where the SGLV consisting of the cylindrical sectors with different curved surface was chosen as the example,the influence on the relative wind pressure distribution and structural wind-induced vibration responses of the closed or open SGLV caused by such parameters as the number of cylindrical sectors, structural curvature and the ratio of rise to span was investigated. Finally, some useful conclusions on the local wind pressure distribution on the structural surface and the wind-induced vibration coefficients of SGLV were developed.
Minecka, Aldona; Kamińska, Ewa; Tarnacka, Magdalena; Dzienia, Andrzej; Madejczyk, Olga; Waliłko, Patrycja; Kasprzycka, Anna; Kamiński, Kamil; Paluch, Marian
2017-08-01
In this paper, broadband dielectric spectroscopy was applied to investigate molecular dynamics of 1,2,3,4,6-penta-O-(trimethylsilyl)-D-glucopyranose (S-GLU) at ambient and elevated pressures. Our studies showed that apart from the structural relaxation, one well resolved asymmetric secondary process (initially labeled as β) is observed in the spectra measured at p = 0.1 MPa. Analysis with the use of the coupling model and criterion proposed by Ngai and Capaccioli indicated that the β-process in S-GLU is probably a Johari-Goldstein relaxation of intermolecular origin. Further high pressure experiments demonstrated that there are in fact two secondary processes contributing to the β-relaxation. Therefore, one can postulate that the coupling model is a necessary, but not sufficient criterion to identify the true nature of the given secondary relaxation process. The role of pressure experiments in better understanding of the molecular origin of local mobility seems to be much more important. Interestingly, our research also revealed that the structural relaxation in S-GLU is very sensitive to compression. It was reflected in an extremely high pressure coefficient of the glass transition temperature (dTg/dp = 412 K/GPa). According to the literature data, such a high value of dTg/dp has not been obtained so far for any H-bonded, van der Waals, or polymeric glass-formers.
Low-dimensional dynamical model for the diversity of pressure patterns used in canary song
Alonso, Leandro M.; Alliende, Jorge A.; Goller, F.; Mindlin, Gabriel B.
2009-04-01
During song production, oscine birds produce large air sac pressure pulses. During those pulses, energy is transferred to labia located at the juncture between the bronchii and the trachea, inducing the high frequency labial oscillations which are responsible for airflow modulations, i.e., the uttered sound. In order to generate diverse syllables, canaries (Serinus canaria) use a set of air sac pressure patterns with characteristic shapes. In this work we show that these different shapes can be approximated by the subharmonic solutions of a forced normal form. This simple model is built from identifying dynamical elements which allow to reproduce the shape of the pressure pattern corresponding to one syllable type. Remarkably, integrating that simple model for other parameters allows to recover the other pressure patterns used during song. Interpreting the diversity of these physiological gestures as subharmonic solutions of a simple nonlinear system allows us to account simultaneously for their morphological features as well as for the syllabic timing and suggests a strategy for the generation of complex motor patterns.
[Effect of dynamic high-pressure micro-fluidization on the structure of maize amylose].
Tu, Zong-Cai; Yin, Yue-Bin; Zhang, Qiu; Wang, Hui
2013-05-01
The effect of dynamic high-pressure micro-fluidization (DHPM) at 80, 120, 160, and 200 MPa on the structure of maize amylose was investigated using scanning electron microscopy (SEM), atomic force microscope (AFM), Xray diffraction, and FT-IR spectroscopy. SEM analysis showed that the surface appearances of maize amylose were altered and the starch granules were partially congregated together after DHPM treatment. AFM images showed that the treated starch molecules are cross-linked to each other and arranged in a close mesh structure. Xray diffraction spectra and IR spectra indicated that relative crystallinity declined gradually with the pressure increasing. The results provide a theoretical basis for starch modification of DHPM.
Porphyry-copper ore shells form at stable pressure-temperature fronts within dynamic fluid plumes.
Weis, P; Driesner, T; Heinrich, C A
2012-12-21
Porphyry-type ore deposits are major resources of copper and gold, precipitated from fluids expelled by crustal magma chambers. The metals are typically concentrated in confined ore shells within vertically extensive vein networks, formed through hydraulic fracturing of rock by ascending fluids. Numerical modeling shows that dynamic permeability responses to magmatic fluid expulsion can stabilize a front of metal precipitation at the boundary between lithostatically pressured up-flow of hot magmatic fluids and hydrostatically pressured convection of cooler meteoric fluids. The balance between focused heat advection and lateral cooling controls the most important economic characteristics, including size, shape, and ore grade. This self-sustaining process may extend to epithermal gold deposits, venting at active volcanoes, and regions with the potential for geothermal energy production.
Molecular Dynamics Simulation of Water Nanodroplets on Silica Surfaces at High Air Pressures
Zambrano, Harvey A; Jaffe, Richard Lawrence; Walther, Jens Honore
2010-01-01
e.g., nanobubbles. In the present work we study the role of air on the wetting of hydrophilic systems. We conduct molecular dynamics simulations of a water nanodroplet on an amorphous silica surface at different air pressures. The interaction potentials describing the silica, water, and air...... are obtained from the literature. The silica surface is modeled by a large 32 ⨯ 32 ⨯ 2 nm amorphous SiO2 structure consisting of 180000 atoms. The water consists of 18000 water molecules surrounded by N2 and O2 air molecules corresponding to air pressures of 0 bar (vacuum), 50 bar, 100 bar and 200 bar. We...... perform extensive simulations of the water- air equilibrium and calibrate the water-air interaction to match the experimental solubility of N2 and O2 in water. For the silica-water system we calibrate the water-silica interaction to match the experimental contact angle of 27º. We subsequently study...
Monte Carlo Simulation of Laser-Ablated Particle Splitting Dynamic in a Low Pressure Inert Gas
Ding, Xuecheng; Zhang, Zicai; Liang, Weihua; Chu, Lizhi; Deng, Zechao; Wang, Yinglong
2016-06-01
A Monte Carlo simulation method with an instantaneous density dependent mean-free-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas. The ablated-particle density and velocity distributions are analyzed. The force distributions acting on the ablated particles are investigated. The influence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed. The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa. This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles. supported by the Natural Science Foundation of Hebei Province, China (No. A2015201166) and the Natural Science Foundation of Hebei University, China (No. 2013-252)
Molecular Dynamics Simulation of Water Nanodroplets on Silica Surfaces at High Air Pressures
Zambrano, Harvey A; Jaffe, Richard Lawrence; Walther, Jens Honore
2010-01-01
e.g., nanobubbles. In the present work we study the role of air on the wetting of hydrophilic systems. We conduct molecular dynamics simulations of a water nanodroplet on an amorphous silica surface at different air pressures. The interaction potentials describing the silica, water, and air...... not been reached. Contact angle measurements of droplets on solid surfaces offer useful quantitative measurements of the physiochemical properties of the solid-liquid interface. For hydrophobic systems the properties the solid- liquid interface are now known to be strongly influenced by the presence of air...... are obtained from the literature. The silica surface is modeled by a large 32 ⨯ 32 ⨯ 2 nm amorphous SiO2 structure consisting of 180000 atoms. The water consists of 18000 water molecules surrounded by N2 and O2 air molecules corresponding to air pressures of 0 bar (vacuum), 50 bar, 100 bar and 200 bar. We...
Fluid description of Weibel-type instabilities via full pressure tensor dynamics
Sarrat, M.; Del Sarto, D.; Ghizzo, A.
2016-08-01
We discuss a fluid model for the description of Weibel-type instabilties based on the inclusion of the full pressure tensor dynamics. The linear analysis first performed by Basu B., Phys. Plasmas, 9, (2002) 5131, for the strong anisotropy limit of Weibel's instability is extended to include the coupling between pure Weibel's and current filamentation instability, and the potential of this fluid approach is further developed. It is shown to allow an easier interpretation of some physical features of these coupled modes, notably the role played by thermal effects. It can be used to identify the role of different closure conditions in pressure-driven instabilities which can be numerically investigated at a remarkably lower computational cost than with kinetic simulations.
Pressure tensor dynamics in the fluid description of Weibel-type instabilities
Sarrat, Mathieu; Del Sarto, Daniele; Ghizzo, Alain
2016-10-01
The study of Weibel-type instabilities triggered by temperature or momentum anisotropy normally requires a full kinetic treatement, though reduced kinetic models often provide an efficient alternative, both from a computational point of view and thanks to a simplified analysis that helps a better physical insight. We here show how, similarly to reduced kinetic models, an extended fluid model including the full pressure tensor dynamics provides a consistent description of Weibel-type modes in presence of two counterstreaming, non-relativistic beams with initially anisotropic pressures: focussing on propagation transverse and parallel to the beams we discuss the fluid dispersion relation of Weibel Instability-Current Filamentation Instability coupled modes and of the time resonant Weibel instability. This fluid analysis is shown to agree with the kinetic result and to allow the identification of some thermal effects, whose interpretation appeared more difficult in full kinetic descriptions.
Oh, Seungkyung
2012-01-01
We perform the largest currently available set of direct N-body calculations of young star cluster models to study the dynamical influence, especially through the ejections of the most massive star in the cluster, on the current relation between the maximum-stellar-mass and the star-cluster-mass. We vary several initial parameters such as the initial half-mass radius of the cluster, the initial binary fraction, and the degree of initial mass segregation. Two different pairing methods are used to construct massive binaries for more realistic initial conditions of massive binaries. We find that lower mass clusters (= 1000 Msun), no most-massive star escapes the cluster within 3 Myr regardless of the initial conditions if clusters have initial half-mass radii, r_0.5, >= 0.8 pc. However, a few of the initially smaller sized clusters (r_0.5 = 0.3 pc), which have a higher density, eject their most massive star within 3 Myr. If clusters form with a compact size and their massive stars are born in a binary system wit...
Tay, W. H.; Kausik, S. S.; Yap, S. L.; Wong, C. S., E-mail: cswong@um.edu.my [Plasma Technology Research Centre, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)
2014-04-15
The discharge dynamics in an atmospheric pressure dielectric barrier discharge (DBD) is studied in a DBD reactor consisting of a pair of stainless steel parallel plate electrodes. The DBD discharge has been generated by a 50 Hz ac high voltage power source. The high-speed intensified charge coupled device camera is used to capture the images of filaments occurring in the discharge gap. It is observed that frequent synchronous breakdown of micro discharges occurs across the discharge gap in the case of negative current pulse. The experimental results reveal that secondary emissions from the dielectric surface play a key role in the synchronous breakdown of plasma filaments.
Simmons, A; Williams, S C; Craggs, M; Andrew, C; Gregory, L; Allin, M; Mundy, A; Leaker, B
1997-01-01
Magnetic resonance imaging gives high quality images of the urinary bladder with excellent contrast. We report here the first application of dynamic, multi-slice, echo planar imaging to a study of urinary bladder emptying. Changes in urinary bladder volumes and rates of urine expulsion from the bladder have been measured simultaneously with bladder pressure. The method shows promise for clinical applications involving compromised bladder function, for reappraising bladder contraction strength-volume relationships, and for investigating the rate of change of length, three-dimensional shape, and wall tension in different parts of the bladder during micturition.
A. J. Komkoua Mbienda
2013-01-01
Lee and Kesler (LK, and Ambrose-Walton (AW methods for estimating vapor pressures ( are tested against experimental data for a set of volatile organic compounds (VOC. required to determine gas-particle partitioning of such organic compounds is used as a parameter for simulating the dynamic of atmospheric aerosols. Here, we use the structure-property relationships of VOC to estimate . The accuracy of each of the aforementioned methods is also assessed for each class of compounds (hydrocarbons, monofunctionalized, difunctionalized, and tri- and more functionalized volatile organic species. It is found that the best method for each VOC depends on its functionality.
DONG Guo-qing; CUI Ya-hui; WANG Zhong-ren; LIU Zhan-sheng; SHEN Ji-quan
2008-01-01
To study the misalignment of gear coupling, this paper analyzed the distortion of the tooth of gear coupling on the base of gear coupling's motion under parallel misalignment, and derived the specific expression of additive radial force, which produced by the rotor' torque. The motion differential equations of the large in-creased pressure wind tunnel rotor-gear coupling system were derived by the finite element method. Newmark integral method was applied to calculate the dynamic response of the system with parallel misalignment. The nu-merical results show that: under the effect of additive radial force, the static misalignment can arouse 2X fre-quency component lateral vibration; the dynamic misalignment can arouse2X,4X,6X multiple frequency compo-nents lateral vibration. The 2X frequency component is obvious. The additive radial force of the gear coupling can arouse lateral vibration with even multiple frequency components.
Atomic and dislocation dynamics simulations of plastic deformation in reactor pressure vessel steel
Monnet, Ghiath; Domain, Christophe; Queyreau, Sylvain; Naamane, Sanae; Devincre, Benoit
2009-11-01
The collective behavior of dislocations in reactor pressure vessel (RPV) steel involves dislocation properties on different phenomenological scales. In the multiscale approach, adopted in this work, we use atomic simulations to provide input data for larger scale simulations. We show in this paper how first-principles calculations can be used to describe the Peierls potential of screw dislocations, allowing for the validation of the empirical interatomic potential used in molecular dynamics simulations. The latter are used to compute the velocity of dislocations as a function of the applied stress and the temperature. The mobility laws obtained in this way are employed in dislocation dynamics simulations in order to predict properties of plastic flow, namely dislocation-dislocation interactions and dislocation interactions with carbides at low and high temperature.
Atomic and dislocation dynamics simulations of plastic deformation in reactor pressure vessel steel
Monnet, Ghiath, E-mail: ghiathmonnet@yahoo.f [EDF-R and D, MMC, Avenue des Renardieres, 77818 Moret sur Loing (France); Domain, Christophe; Queyreau, Sylvain; Naamane, Sanae [EDF-R and D, MMC, Avenue des Renardieres, 77818 Moret sur Loing (France); Devincre, Benoit [LEM, CNRS-ONERA, 29 av. de la division Leclerc, 92130 Chatillon (France)
2009-11-15
The collective behavior of dislocations in reactor pressure vessel (RPV) steel involves dislocation properties on different phenomenological scales. In the multiscale approach, adopted in this work, we use atomic simulations to provide input data for larger scale simulations. We show in this paper how first-principles calculations can be used to describe the Peierls potential of screw dislocations, allowing for the validation of the empirical interatomic potential used in molecular dynamics simulations. The latter are used to compute the velocity of dislocations as a function of the applied stress and the temperature. The mobility laws obtained in this way are employed in dislocation dynamics simulations in order to predict properties of plastic flow, namely dislocation-dislocation interactions and dislocation interactions with carbides at low and high temperature.
Shoushtari, Seyed Mohammad Hossein Jazayeri; Cartwright, Nick; Perrochet, Pierre; Nielsen, Peter
2017-01-01
of moisture content relative to the suction head was observed indicating that the response time of the moisture content to watertable motion is greater than that of the pore water pressure. The observed moisture-pressure dynamics are qualitatively reproduced using a hysteretic Richards' equation model. However, quantitative differences exist which are likely to be due to previous findings that demonstrated that the Richards' equation model is unable to accurately reproduce the observed watertable wave dispersion, particularly at shorter period oscillations.
Xiangwei Kong
2014-01-01
Full Text Available Investigation of surge pressure is of great significance to the circulation loss problem caused by unsteady operations in management pressure drilling (MPD operations. With full consideration of the important factors such as wave velocity, gas influx rate, pressure, temperature, and well depth, a new surge pressure model has been proposed based on the mass conservation equations and the momentum conservation equations during MPD operations. The finite-difference method, the Newton-Raphson iterative method, and the fourth-order explicit Runge-Kutta method (R-K4 are adopted to solve the model. Calculation results indicate that the surge pressure has different values with respect to different drill pipe tripping speeds and well parameters. In general, the surge pressure tends to increase with the increases of drill pipe operating speed and with the decrease of gas influx rate and wellbore diameter. When the gas influx occurs, the surge pressure is weakened obviously. The surge pressure can cause a significant lag time if the gas influx occurs at bottomhole, and it is mainly affected by pressure wave velocity. The maximum surge pressure may occur before drill pipe reaches bottomhole, and the surge pressure is mainly affected by drill pipe operating speed and gas influx rate.
Uwe Kortshagen; Joachim Heberlein; Steven L. Girshick
2009-06-01
This project was funded over two periods of three years each, with an additional year of no-cost extension. Research in the first funding period focused on the physics of uniform atmospheric pressure glow discharges, the second funding period was devoted to the study of the dynamics of nanometer-sized particles in plasmas.
Guinot, Pierre-Grégoire; Bernard, Eugénie; Levrard, Mélanie; Dupont, Hervé; Lorne, Emmanuel
2015-01-19
Gradual reduction of the dosage of norepinephrine (NE) in patients with septic shock is usually left to the physician's discretion. No hemodynamic indicator predictive of the possibility of decreasing the NE dosage is currently available at the bedside. The respiratory pulse pressure variation/respiratory stroke volume variation (dynamic arterial elastance (Eadyn)) ratio has been proposed as an indicator of vascular tone. The purpose of this study was to determine whether Eadyn can be used to predict the decrease in arterial pressure when decreasing the NE dosage in resuscitated sepsis patients. A prospective study was carried out in a university hospital intensive care unit. All consecutive patients with septic shock monitored by PICCO2 for whom the intensive care physician planned to decrease the NE dosage were enrolled. Measurements of hemodynamic and PICCO2 variables were obtained before/after decreasing the NE dosage. Responders were defined by a >15% decrease in mean arterial pressure (MAP). In total, 35 patients were included. MAP decreased by >15% after decreasing the NE dosage in 37% of patients (n = 13). Clinical characteristics appeared to be similar between responders and nonresponders. Eadyn was lower in responders than in nonresponders (0.75 (0.69 to 0.85) versus 1 (0. 83 to 1.22), P decrease in arterial pressure, with an area under the receiver-operating characteristic curve of 0.87 (95% confidence interval (95% CI): 0.72 to 0.96; P decrease in arterial pressure in response to NE dose reduction. Eadyn may constitute an easy-to-use functional approach to arterial-tone assessment, which may be helpful to identify patients likely to benefit from NE dose reduction.
High Pressure Sensing and Dynamics Using High Speed Fiber Bragg Grating Interrogation Systems
Rodriguez, G. [LANL; Sandberg, R. L. [LANL; Lalone, B. M. [NSTec; Marshall, B. R. [NSTec; Grover, M. [NSTec; Stevens, G. D. [NSTec; Udd, E. [Columbia Gorge Research
2014-06-01
Fiber Bragg gratings (FBGs) are developing into useful sensing tools for measuring high pressure dynamics in extreme environments under shock loading conditions. Approaches using traditional diode array coupled FBG interrogation systems are often limited to readout speeds in the sub-MHz range. For shock wave physics, required detection speeds approaching 100 MHz are desired. We explore the use of two types of FBG sensing systems that are aimed at applying this technology as embedded high pressure probes for transient shock events. Both approaches measure time resolved spectral shifts in the return light from short (few mm long) uniform FBGs at 1550 nm. In the first approach, we use a fiber coupled spectrometer to demultiplex spectral channels into an array (up to 12) of single element InGaAs photoreceivers. By monitoring the detectors during a shock impact event with high speed recording, we are able to track the pressure induced spectral shifting in FBG down to a time resolution of 20 ns. In the second approach, developed at the Special Technologies Lab, a coherent mode-locked fiber laser is used to illuminate the FBG sensor. After the sensor, wavelength-to-time mapping is accomplished with a chromatic dispersive element, and entire spectra are sampled using a single detector at the modelocked laser repetition rate of 50 MHz. By sampling with a 12 GHz InGaAs detector, direct wavelength mapping in time is recorded, and the pressure induced FBG spectral shift is sampled at 50 MHz. Here, the sensing systems are used to monitor the spectral shifts of FBGs that are immersed into liquid water and shock compressed using explosives. In this configuration, the gratings survive to pressures approaching 50 kbar. We describe both approaches and present the measured spectral shifts from the shock experiments.
Milena Biasi Ferlin
2006-04-01
Full Text Available Avaliou-se o efeito de dois resíduos de forragem pós-pastejo quanto às características morfogênicas de folhas e perfilhos e estrutura do relvado de Panicum maximum Jacq. cv. Tanzânia-I até os 35 dias após a desfolha, em duas estações do ano, verão e outono. Utilizou-se o delineamento de blocos completos casualizados, com os resíduos de forragem na parcela principal, estação do ano nas subparcelas e dias após o pastejo nas sub-subparcelas, com três repetições. Os resíduos de forragem não influenciaram as taxas de aparecimento e alongamento de folhas, bem como duração do alongamento de folhas nos perfilhos residuais e quantidade de perfilhos. Os números médios de lâminas foliares e de perfilhos basilares novos apresentam-se semelhantes no transcorrer dos dias de descanso no verão e outono. Já o número de perfilhos aéreos novos, no verão, decresceu com os dias de descanso e, no outono, manteve-se mais constante. No outono, o comprimento de lâminas foliares aumentou linearmente até o 35º dia de descanso. Já no verão, as lâminas foliares atingiram o crescimento máximo em torno de 30 dias.The effect of two forage residuals after grazing was evaluated as to morphogenic traits of leaves and tillers and forage structure of Panicum maximum Jacq. cv. Tanzania-I until the 35 days after defoliation, within two year seasons, summer and fall. The experimental design was a complete randomized blocks, with forage residuals in the main plots, year season in the sub-plot, and days after grazing in the sub-sub-plot, with three replications. The forage residuals did not affect the rates of appearance and lengthening of leaves in the residual tillers, and into the tillers quantity. The average number of leaf blades and new basal tillers keep a similar performance throughout the summer and autumn days. Therefore the number of new aerial tillers, during the summer, decreased as a function of days of rest being that in the fall
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.
Welch, Tyler; Keller, Thomas; Maldonado, Ruben; Metzger, Melodie; Mohr, Karen; Kvitne, Ronald
2017-12-01
The natural history of posterior cruciate ligament (PCL) deficiency includes the development of arthrosis in the patellofemoral joint (PFJ). The purpose of this biomechanical study was to evaluate the hypothesis that dynamic bracing reduces PFJ pressures in PCL- and combined PCL/posterolateral corner (PLC)-deficient knees. Controlled Laboratory Study. Eight fresh frozen cadaveric knees with intact cruciate and collateral ligaments were included. PFJ pressures and force were measured using a pressure mapping system via a lateral arthrotomy at knee flexion angles of 30°, 60°, 90°, and 120° in intact, PCL-deficient, and PCL/PLC-deficient knees under a combined quadriceps/hamstrings load of 400 N/200 N. Testing was then repeated in PCL- and PCL/PLC-deficient knees after application of a dynamic PCL brace. Application of a dynamic PCL brace led to a reduction in peak PFJ pressures in PCL-deficient knees. In addition, the brace led to a significant reduction in peak pressures in PCL/PLC-deficient knees at 60°, 90°, and 120° of flexion. Application of the dynamic brace also led to a reduction in total PFJ force across all flexion angles for both PCL- and PCL/PLC-deficient knees. Dynamic bracing reduces PFJ pressures in PCL- and combined PCL/PLC-deficient knees, particularly at high degrees of knee flexion.
2016-01-01
For 200 years, the ‘closed box’ analogy of intracranial pressure (ICP) has underpinned neurosurgery and neuro-critical care. Cushing conceptualised the Monro-Kellie doctrine stating that a change in blood, brain or CSF volume resulted in reciprocal changes in one or both of the other two. When not possible, attempts to increase a volume further increase ICP. On this doctrine’s “truth or relative untruth” depends many of the critical procedures in the surgery of the central nervous system. However, each volume component may not deserve the equal weighting this static concept implies. The slow production of CSF (0.35 ml/min) is dwarfed by the dynamic blood in and outflow (∼700 ml/min). Neuro-critical care practice focusing on arterial and ICP regulation has been questioned. Failure of venous efferent flow to precisely match arterial afferent flow will yield immediate and dramatic changes in intracranial blood volume and pressure. Interpreting ICP without interrogating its core drivers may be misleading. Multiple clinical conditions and the cerebral effects of altitude and microgravity relate to imbalances in this dynamic rather than ICP per se. This article reviews the Monro-Kellie doctrine, categorises venous outflow limitation conditions, relates physiological mechanisms to clinical conditions and suggests specific management options. PMID:27174995
Effects of sediment on the dynamic pressure of water and sediment on dams
无
2001-01-01
After a reservoir has been in operation for a period of time,a sediment layer is likely formed before the dam. Since studies of the effects of sediment layers on the hydrodynamic pressures of impounded water and the aseismic responses of dam are few,the dynamic effect of sediment may be applied neither in the seismic design of new dams nor in the assessment of earthquake safety of existing dams. However,a common practice of the action of sediment layers and foundation is based on a partial energy absorption boundary. It is shown that during a vertical harmonic ground motion,the sediment layer could alter the natural frequencies of reservoir. The dynamic pressure on a rigid vertical dam face caused by the vertical ground motion is obtained through a computational model and an experimental test by using a shaking table. With a change in the thickness of sediment,the frequency corresponding to the inertia amplification effect appears to vary gradually. The results are useful for further study of seismic responses of dams.
ZIANE, M.
2007-11-01
Full Text Available The aim of this paper is to study the dynamic behaviour of a plant constituted by an electrical power system and a gas discharge lamp, this latter, increasingly used in street lighting, remains a nonlinear load element. Various approaches are used to represent it, one is the approximation of the discharge represented by a hot "channel", which verifies the assumption of local thermodynamic equilibrium [LTE] or the polynomial form of the conductance variation. A calculation procedure, based on "channel" approximation of the high pressure mercury (HPM gas-discharge lamp, is developed to determine the physical and electric magnitudes, which characterize the dynamic behavior of the couple "lamp-electrical power system". The evolution of the lamp properties when principal parameters of the discharge (pressure of mercury, voltage supply, frequency are varying were studied and analyzed. We show the concordance between simulation, calculations and measurements for electric, energetic or irradiative characteristics. The model reproduces well the evolution of properties of the supply when principal parameters of the discharge vary.
Pick-up ion pressure gradients modulating the solar wind dynamics
Fahr, Hans J.; Fichtner, Horst
1995-01-01
Neutral interstellar atoms penetrate deeply into the inner heliosphere before they become ionized by various processes. As ions they are picked-up by the frozen-in magnetic fields and are convected outwards with the solar wind plasma. Thereby the primary plasma flow is mass, momentum, and energy-loaded. The dynamics of the distant multi-constituent solar wind is, however, not solely determined by these loading processes, but is also affected by the wave-mediated pick-up ion pressure gradients derivable from the pick-up ion distribution function. The action of the radial components of these pressures essentially counter balances the decelerating effect of the solar wind momentum loading, diminishing strongly the deceleration of the distant solar wind. Furthermore the latitudinal components of the pick-up ion pressures induce latitudinal forces acting on the multiconstituent solar plasma outflow and inducing nonradial bulk flow components. The enforced nonradial outflow geometry on the upwind hemisphere may partly be responsible for the magnetic flux deficit which was claimed since several years in the PIONEER-10 magnetic flux data.
Wang, Luying; Dumont, Randall S.; Dickson, James M.
2013-03-01
Nonequilibrium molecular dynamics (NEMD) simulations are presented to investigate the effect of water-membrane interactions on the transport properties of pressure-driven water flow passing through carbon nanotube (CNT) membranes. The CNT membrane is modified with different physical properties to alter the van der Waals interactions or the electrostatic interactions between water molecules and the CNT membranes. The unmodified and modified CNT membranes are models of simplified nanofiltration (NF) membranes at operating conditions consistent with real NF systems. All NEMD simulations are run with constant pressure difference (8.0 MPa) temperature (300 K), constant pore size (0.643 nm radius for CNT (12, 12)), and membrane thickness (6.0 nm). The water flow rate, density, and velocity (in flow direction) distributions are obtained by analyzing the NEMD simulation results to compare transport through the modified and unmodified CNT membranes. The pressure-driven water flow through CNT membranes is from 11 to 21 times faster than predicted by the Navier-Stokes equations. For water passing through the modified membrane with stronger van der Waals or electrostatic interactions, the fast flow is reduced giving lower flow rates and velocities. These investigations show the effect of water-CNT membrane interactions on water transport under NF operating conditions. This work can help provide and improve the understanding of how these membrane characteristics affect membrane performance for real NF processes.
Bershader, Daniel
1988-01-01
For some time now, NASA has had a program under way to aid in the validation of rotor performance and acoustics codes associated with the UH-60 rotary-wing aircraft; and to correlate results of such studies with those obtained from investigations of other selected aircraft rotor performance. A central feature of these studies concerns the dynamic measurement of surface pressure at various locations up to frequencies of 25 KHz. For this purpose, fast-response gauges of the Kulite type are employed. The latter need to be buried in the rotor; they record surface pressures which are transmitted by a pipette connected to the gauge. The other end of the pipette is cut flush with the surface. In certain locations, the pipette configuration includes a rather sharp right-angle bend. The natural question has arisen in this connection: In what way are the pipettes modifying the signals received at the rotor surface and subsequently transmitted to the sensitive Kulite transducer element. The basic details and results of the program performed and recently completed in the High Pressure Shock Tube Laboratory of the Department of Aeronautics and Astronautics at Stanford University are given.
Transient flow model and pressure dynamic features of tree-shaped fractal re- servoirs
TAN Xiao-hua; LI Xiao-ping
2014-01-01
A transient flow model of tree-shaped fractal reservoirs is built by embedding a fracture network simulated by a tree-shaped fractal network into a matrix system. The model can be solved using the Laplace conversion method. The dimensionless bottom hole pressure can be obtained using the Stehfest numerical inversion method. The bi-logarithmic type curves for the tree-shaped fractal reservoirs are thus obtained. The pressure transient responses under different fractal factors are discussed. The factors with a primary effect on the inter-porosity flow regime include the initial branch numberN, the length ratioα, and the branch angleθ. The diameter ratioβ has a significant effect on the fracture radial flow, the inter-porosity and the total system radial flow regimes. The total branch levelM of the network mainly influences the total system radial flow regime. The model presented in this paper provides a new methodology for analyzing and predicting the pressure dynamic characteristics of naturally fractured reservoirs.
Peer pressure is a double-edged sword in vaccination dynamics
Wu, Zhi-Xi; Zhang, Hai-Feng
2013-10-01
Whether or not to change behavior depends not only on the personal success of each individual, but also on the success and/or behavior of others. Using this as motivation, we incorporate the impact of peer pressure into a susceptible-vaccinated-infected-recovered (SVIR) epidemiological model, where the propensity to adopt a particular vaccination strategy depends both on individual success as well as on the strategies of neighbors. We show that plugging into the peer pressure is a double-edged sword, which, on the one hand, strongly promotes vaccination when its cost is below a critical value, but, on the other hand, it can also strongly impede it if the critical value is exceeded. We explain this by revealing a facilitated cluster formation process that is induced by the peer pressure. Due to this, the vaccinated individuals are inclined to cluster together and therefore become unable to efficiently inhibit the spread of the infectious disease if the vaccination is costly. If vaccination is cheap, however, they reinforce each other in using it. Our results are robust to variations of the SVIR dynamics on different population structures.
Wang, Luying; Dumont, Randall S; Dickson, James M
2013-03-28
Nonequilibrium molecular dynamics (NEMD) simulations are presented to investigate the effect of water-membrane interactions on the transport properties of pressure-driven water flow passing through carbon nanotube (CNT) membranes. The CNT membrane is modified with different physical properties to alter the van der Waals interactions or the electrostatic interactions between water molecules and the CNT membranes. The unmodified and modified CNT membranes are models of simplified nanofiltration (NF) membranes at operating conditions consistent with real NF systems. All NEMD simulations are run with constant pressure difference (8.0 MPa) temperature (300 K), constant pore size (0.643 nm radius for CNT (12, 12)), and membrane thickness (6.0 nm). The water flow rate, density, and velocity (in flow direction) distributions are obtained by analyzing the NEMD simulation results to compare transport through the modified and unmodified CNT membranes. The pressure-driven water flow through CNT membranes is from 11 to 21 times faster than predicted by the Navier-Stokes equations. For water passing through the modified membrane with stronger van der Waals or electrostatic interactions, the fast flow is reduced giving lower flow rates and velocities. These investigations show the effect of water-CNT membrane interactions on water transport under NF operating conditions. This work can help provide and improve the understanding of how these membrane characteristics affect membrane performance for real NF processes.
Lelandais, Thomas; Ravier, Edouard; Mourgues, Régis; Pochat, Stéphane; Strzerzynski, Pierre; Bourgeois, Olivier
2017-04-01
Tunnel valleys are elongated and overdeepened depressions up to hundreds of kilometers long, several kilometers wide and hundreds of meters deep, found in formerly glaciated areas. These drainage features are interpreted as the result of subglacial meltwater erosion beneath ice sheets and constitute a major component of the subglacial drainage system. Although tunnel valleys have been described worldwide in the past decades, their formation is still a matter of debate. Here, we present an innovative experimental approach simulating pressurized water flow in a subglacial environment in order to study the erosional processes occurring at the ice-bed interface. We use a sandbox partially covered by a circular, viscous and transparent lid (silicon putty), simulating an impermeable ice cap. Punctual injection of pressurized water in the substratum at the center of the lid simulates meltwater production beneath the ice cap. Surface images collected by six synchronized cameras allow to monitor the evolution of the experiment through time, using photogrammetry methods and DEM generation. UV markers placed in the silicon are used to follow the silicon flow during the drainage of water at the substratum-lid interface, and give the unique opportunity to simultaneously follow the formation of tunnel valleys and the evolution of ice dynamics. When the water pressure is low, groundwater circulates within the substratum only and no drainage landforms appear at the lid-substratum interface. By contrast, when the water pressure exceeds a threshold that is larger than the sum of glaciostatic and lithostatic pressures, additional water circulation occurs at the lid-substratum interface and drainage landforms develop from the lid margin. These landforms share numerous morphological criteria with tunnel valleys such as undulating longitudinal profiles, U-shaped cross-sectional profiles with flat floors, constant widths and abrupt flanks. Continuous generation of DEMs and flow velocity
A. Sluijs
2009-08-01
Full Text Available Late Paleocene and Early Eocene climates and ecosystems underwent significant change during several transient global warming phases, associated with rapidly increasing atmospheric carbon concentrations, of which the Paleocene-Eocene Thermal Maximum (PETM; ~55.5 Ma is best studied. While biotic response to the PETM as a whole (~170 kyrs has been relatively well documented, variations during the PETM have been neglected. Here we present organic dinoflagellate cyst (dinocyst distribution patterns across two stratigraphically expanded PETM sections from the New Jersey Shelf, Bass River and Wilson Lake. Many previously studied sites show a uniform abundance of the thermophilic and presumably heterotrophic taxon Apectodinium that spans the entire carbon isotope excursion (CIE of the PETM. In contrast, the New Jersey sections show large variations in abundances of many taxa during the PETM, including the new species Florentinia reichartii that we formally propose. We infer paleoecological preferences of taxa that show temporal abundance peaks, both qualitative and absolute quantitative, from empirical as well as statistical information, i.e., principle (PCA and canonical correspondence analyses (CCA. In the CCAs, we combine the dinocyst data with previously published environmental proxy data from these locations, such as TEX_{86} paleothermometry, magnetic susceptibility and sedimentary size fraction. The combined information supports previous inferences that sea level rose during the PETM, but also indicates a (regional increase in fresh-water runoff that started ~10 kyr after the onset of the CIE, and perhaps precession-paced cycles in sea surface productivity. The highly variable dinocyst assemblages of the PETM contrast with rather stable Upper Paleocene assemblages, which suggests that carbon input caused a dynamic climate state, at least regionally.
Theory for planetary exospheres: I. Radiation pressure effect on dynamical trajectories
Beth, A.; Garnier, P.; Toublanc, D.; Dandouras, I.; Mazelle, C.
2016-03-01
The planetary exospheres are poorly known in their outer parts, since the neutral densities are low compared with the instruments detection capabilities. The exospheric models are thus often the main source of information at such high altitudes. We present a new way to take into account analytically the additional effect of the radiation pressure on planetary exospheres. In a series of papers, we present with an Hamiltonian approach the effect of the radiation pressure on dynamical trajectories, density profiles and escaping thermal flux. Our work is a generalisation of the study by Bishop and Chamberlain (Bishop, J., Chamberlian, J.W. [1989]. Icarus 81, 145-163). In this first paper, we present the complete solutions of particles trajectories, which are not conics, under the influence of the solar radiation pressure with some assumptions. This problem is similar to the classical Stark problem (Stark, J. [1914]. Ann. Phys. 348, 965-982). This problem was largely tackled in the literature and more specifically, recently by Lantoine and Russell (Lantoine, G., Russell, R.P. [2011]. Celest. Mech. Dynam. Astron. 109, 333-366) and by Biscani and Izzo (Biscani, F., Izzo, D. [2014]. Mon. Not. R. Astron. Soc. 439, 810-822) as we will discuss in this paper. We give here the full set of solutions for the motion of a particle (in our case for an atom or a molecule), i.e. the space coordinates and the time solution for bounded and unbounded trajectories in terms of Jacobi elliptic functions. We thus provide here the complete set of solutions for this so-call Stark effect (Stark, J. [1914]. Ann. Phys. 348, 965-982) in terms of Jacobi elliptic functions (Jacobi, C.G.J. [1829]. Fundamenta nova theoriae functionum ellipticarum. Sumtibus fratrum), which may be used to model the trajectories of particles in planetary exospheres.
Coffin, T.
1986-01-01
A dynamic pressure data base and data base management system developed to characterize the Space Shuttle Main Engine (SSME) dynamic pressure environment is described. The data base represents dynamic pressure measurements obtained during single engine hot firing tesets of the SSME. Software is provided to permit statistical evaluation of selected measurements under specified operating conditions. An interpolation scheme is also included to estimate spectral trends with SSME power level. Flow dynamic environments in high performance rocket engines are discussed.
Coffin, T.
1986-01-01
A dynamic pressure data base and data base management system developed to characterize the Space Shuttle Main Engine (SSME) dynamic pressure environment is reported. The data base represents dynamic pressure measurements obtained during single engine hot firing tests of the SSME. Software is provided to permit statistical evaluation of selected measurements under specified operating conditions. An interpolation scheme is included to estimate spectral trends with SSME power level. Flow Dynamic Environments in High Performance Rocket Engines are described.
Microdomain Ca{sup 2+} dynamics in mammalian muscle following prolonged high pressure treatments
Schnee, S; Schuermann, S; Fink, R [Medical Biophysics, Institute of Physiology and Pathophysiology, University of Heidelberg, INF326, 69120 Heidelberg (Germany); Ludwig, H [Physical Chemistry, Institute of Molecular Biotechnology and Biopharmacy, University of Heidelberg, INF 366 (Germany); Wegner, F von; Friedrich, O, E-mail: oliver.friedrich@physiologie.uni-heidelberg.de
2008-07-15
High pressure (HP) applications are an important thermodynamic tool to influence cellular processes. Especially processes that undergo large volume changes, e.g. opening or closing of ion channels, are in particular susceptible to HP treatments. Such volume changes are extremely difficult to assess for intracellular ion channels, like ryanodine receptors (RyR) residing in the membrane of organelles. In skeletal muscle, RyR act as Ca{sup 2+} release channels. We previously showed that plasmalemmal Na{sup +} and Ca{sup 2+} ion channels were irreversibly altered after prolonged 20 MPa treatments. Here, changes in microdomain Ca{sup 2+} levels due to elementary Ca{sup 2+} release events (ECRE) were monitored using confocal fluorescence microscopy. We studied ECRE in mammalian skeletal muscle following 3 h HP treatments up to 30 MPa to clarify whether RyR induced intracellular microdomain Ca{sup 2+} dynamics was more susceptible to HP treatment compared to surface membrane ion currents. ECRE frequencies exponentially declined with pressure. ECRE amplitudes and rise times (RT) were quite robust towards HP treatments. In contrast, spatial and temporal ECRE extension showed a tendency towards larger values up to 20 MPa but declined for higher pressures. Activation volumes for pressure-induced persistent ECRE alterations were zero for RT but showed a bimodal behavior for event duration. It seems that although ECRE frequencies are markedly reduced, ECRE morphology is less affected by HP. In particular, RyR opening time is practically unaltered and the observed morphological ECRE changes might reflect alterations in local Ca{sup 2+} buffers and Ca{sup 2+} concentration profiles rather than involvement of RyR in mammalian skeletal muscle.
Barbarin, Y.; Lefrançois, A.; Magne, S.; Woirin, K.; Sinatti, F.; Osmont, A.; Luc, J.
2016-08-01
High pressure shock profiles are monitored using a long Fiber Bragg Grating (FBG). Such thin probe, with a diameter of typically 150 μm, can be inserted directly into targets for shock plate experiments. The shocked FBG's portion is stressed under compression, which increases its optical group index and shortens its grating period. Placed along the 2D symmetrical axis of the cylindrical target, the second effect is stronger and the reflected spectrum shifts towards the shorter wavelengths. The dynamic evolution of FBG spectra is recorded with a customized Arrayed Waveguide Grating (AWG) spectrometer covering the C+L band. The AWG provides 40 channels of 200-GHz spacing with a special flattop design. The output channels are fiber-connected to photoreceivers (bandwidth: DC - 400 MHz or 10 kHz - 2 GHz). The experimental setup was a symmetric impact, completed in a 110-mm diameter single-stage gas gun with Aluminum (6061T6) impactors and targets. The FBG's central wavelength was 1605 nm to cover the pressure range of 0 - 8 GPa. The FBG was 50-mm long as well as the target's thickness. The 20-mm thick impactor maintains a shock within the target over a distance of 30 mm. For the impact at 522 m/s, the sustained pressure of 3.6 GPa, which resulted in a Bragg shift of (26.2 +/- 1.5) nm, is measured and retrieved with respectively thin-film gauges and the hydrodynamic code Ouranos. The shock sensitivity of the FBG is about 7 nm/GPa, but it decreases with the pressure level. The overall spectra evolution is in good agreement with the numerical simulations.
Sands, William A; McNeal, Jeni R; Murray, Steven R; Stone, Michael H
2015-05-01
Athlete recovery-adaptation is crucial to the progress and performance of highly trained athletes. The purpose of this study was to assess peristaltic pulse dynamic compression (PPDC) in reducing short-term pressure-to-pain threshold (PPT) among Olympic Training Center athletes after morning training. Muscular tenderness and stiffness are common symptoms of fatigue and exercise-induced muscle microtrauma and edema. Twenty-four highly trained athletes (men = 12 and women = 12) volunteered to participate in this study. The athletes were randomly assigned to experimental (n = 12) and control (n = 12) groups. Pressure-to-pain threshold measurements were conducted with a manual algometer on 3 lower extremity muscles. Experimental group athletes underwent PPDC on both legs through computer-controlled circumferential inflated leggings that used a peristaltic-like pressure pattern from feet to groin. Pressures in each cell were set to factory defaults. Treatment time was 15 minutes. The control group performed the same procedures except that the inflation pump to the leggings was off. The experimental timeline included a morning training session, followed by a PPT pretest, treatment application (PPDC or control), an immediate post-test (PPT), and a delayed post-test (PPT) after the afternoon practice session. Difference score results showed that the experimental group's PPT threshold improved after PPDC treatment immediately and persisted the remainder of the day after afternoon practice. The control group showed no statistical change. We conclude that PPDC is a promising means of accelerating and enhancing recovery after the normal aggressive training that occurs in Olympic and aspiring Olympic athletes.
Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae.
Crary, F J; Clarke, J T; Dougherty, M K; Hanlon, P G; Hansen, K C; Steinberg, J T; Barraclough, B L; Coates, A J; Gérard, J-C; Grodent, D; Kurth, W S; Mitchell, D G; Rymer, A M; Young, D T
2005-02-17
The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms, but the relation between the solar wind and the dynamics of the outer planets' magnetospheres is poorly understood. Jupiter's magnetospheric dynamics and aurorae are dominated by processes internal to the jovian system, whereas Saturn's magnetosphere has generally been considered to have both internal and solar-wind-driven processes. This hypothesis, however, is tentative because of limited simultaneous solar wind and magnetospheric measurements. Here we report solar wind measurements, immediately upstream of Saturn, over a one-month period. When combined with simultaneous ultraviolet imaging we find that, unlike Jupiter, Saturn's aurorae respond strongly to solar wind conditions. But in contrast to Earth, the main controlling factor appears to be solar wind dynamic pressure and electric field, with the orientation of the interplanetary magnetic field playing a much more limited role. Saturn's magnetosphere is, therefore, strongly driven by the solar wind, but the solar wind conditions that drive it differ from those that drive the Earth's magnetosphere.
Probabilistic modelling of the high-pressure arc cathode spot displacement dynamic
Coulombe, S
2003-01-01
A probabilistic modelling approach for the study of the cathode spot displacement dynamic in high-pressure arc systems is developed in an attempt to interpret the observed voltage fluctuations. The general framework of the model allows to define simple, probabilistic displacement rules, the so-called cathode spot dynamic rules, for various possible surface states (un-arced metal, arced, contaminated) and to study the resulting dynamic of the cathode spot displacements over one or several arc passages. The displacements of the type-A cathode spot (macro-spot) in a magnetically rotating arc using concentric electrodes made up of either clean or contaminated metal surfaces is considered. Experimental observations for this system revealed a 1/f sup - sup t sup i sup l sup d sup e sup 1 signature in the frequency power spectrum (FPS) of the arc voltage for anchoring arc conditions on the cathode (e.g. clean metal surface), while it shows a 'white noise' signature for conditions favouring a smooth movement (e.g. ox...
Dynamic modeling and explicit/multi-parametric MPC control of pressure swing adsorption systems
Khajuria, Harish
2011-01-01
Pressure swing adsorption (PSA) is a flexible, albeit complex gas separation system. Due to its inherent nonlinear nature and discontinuous operation, the design of a model based PSA controller, especially with varying operating conditions, is a challenging task. This work focuses on the design of an explicit/multi-parametric model predictive controller for a PSA system. Based on a system involving four adsorbent beds separating 70% H2, 30% CH4 mixture into high purity hydrogen, the key controller objective is to fast track H2 purity to a set point value of 99.99%. To perform this task, a rigorous and systematic framework is employed. First, a high fidelity detailed dynamic model is built to represent the system\\'s real operation, and understand its dynamic behavior. The model is then used to derive appropriate linear models by applying suitable system identification techniques. For the reduced models, a model predictive control (MPC) step is formulated, where latest developments in multi-parametric programming and control are applied to derive a novel explicit MPC controller. To test the performance of the designed controller, closed loop simulations are performed where the dynamic model is used as the virtual plant. Comparison studies of the derived explicit MPC controller are also performed with conventional PID controllers. © 2010 Elsevier Ltd. All rights reserved.
P. T. Macklem
2006-12-01
Full Text Available This article reviews recent research in normal subjects exercising with and without expiratory flow limitation at 1 L·s–1 imposed by a Starling resistor in the expiratory line, and in patients with chronic obstructive pulmonary disease (COPD, using optoelectronic plethysmography to measure respiratory kinematics, combined with mouth, pleural and abdominal pressure measurements, to assess work of breathing and respiratory muscle performance. In normal subjects, flow-limited exercise resulted in the following: 1 Impaired exercise performance due to intolerable dyspnoea; 2 hypercapnia; 3 excessive respiratory muscle recruitment; 4 blood shifts from trunk to extremities; 5 a 10% reduction in cardiac output and a 5% reduction in arterial oxygen saturation, decreasing energy supplies to working respiratory and locomotor muscles. In both normal subjects and in COPD patients, dynamic hyperinflation did not always occur. Those patients that hyperinflated had worse lung function and less work of breathing, but better exercise performance than the others, in whom expiratory muscle recruitment prevented dynamic hyperinflation at the cost of increased work of breathing and excessive oxygen cost of breathing. This established an early competition between respiratory and locomotor muscles for available energy supplies. Dynamic hyperinflation is a better exercise strategy in chronic obstructive pulmonary disease than expiratory muscle recruitment, but the benefit it confers is small.
Effects of a solar wind dynamic pressure increase in the magnetosphere and in the ionosphere
L. Juusola
2010-10-01
Full Text Available On 17 July 2005, an earthward bound north-south oriented magnetic cloud and its sheath were observed by the ACE, SoHO, and Wind solar wind monitors. A steplike increase of the solar wind dynamic pressure during northward interplanetary magnetic field conditions was related to the leading edge of the sheath. A timing analysis between the three spacecraft revealed that this front was not aligned with the GSE y-axis, but had a normal (−0.58,0.82,0. Hence, the first contact with the magnetosphere occurred on the dawnside rather than at the subsolar point. Fortunately, Cluster, Double Star 1, and Geotail happened to be distributed close to the magnetopause in this region, which made it possible to closely monitor the motion of the magnetopause. After the pressure front had impacted the magnetosphere, the magnetopause was perceived first to move inward and then immediately to correct the overshoot by slightly expanding again such that it ended up between the Cluster constellation with Double Star 1 inside the magnetosphere and Geotail in the magnetosheath. Coinciding with the inward and subsequent outward motion, the ground-based magnetic field at low latitudes was observed to first strengthen and then weaken. As the magnetopause position stabilised, so did the ground-based magnetic field intensity, settling at a level slightly higher than before the pressure increase. Altogether the magnetopause was moving for about 15 min after its first contact with the front. The high latitude ionospheric signature consisted of two parts: a shorter (few minutes and less intense preliminary part comprised a decrease of AL and a negative variation of PC. A longer (about ten minutes and more intense main part of the signature comprised an increase of AU and a positive variation of PC. Measurements from several ground-based magnetometer networks (210 MM CPMN, CANMOS, CARISMA, GIMA, IMAGE, MACCS, SuperMAG, THEMIS, TGO were used to obtain information on the
Smolin, Nikolai; Winter, Roland
2008-01-24
It is now generally agreed that the hydration water and solvational properties play a crucial role in determining the dynamics and hence the functionality of proteins. We present molecular dynamics computer simulation studies on staphylococcal nuclease (SNase) at various temperatures and pressures as well as in different cosolvent solutions containing various concentrations of urea and glycerol. The aim is to provide a molecular level understanding of how different types of cosolvents (chaotropic and kosmotropic) as well as temperature and high hydrostatic pressure modify the structure and dynamics of the hydration water. Taken together, these three intrinsic thermodynamic variables, temperature, pressure, and chemical potential (or activity) of the solvent, are able to influence the stability and function of the protein by protein-solvent dynamic coupling in different ways. A detailed analysis of the structural and dynamical properties of the water and cosolvents at the protein surface (density profile, coordination numbers, hydrogen-bond distribution, average H-bond lifetimes (water-protein and water-water), and average residence time of water in the hydration shell) was carried out, and differences in the structural and dynamical properties of the hydration water in the presence of the different cosolvents and at temperatures between 300 and 400 K and pressures up to 5000 bar are discussed. Furthermore, the results obtained help understand various thermodynamic properties measured for the protein.
On the impact of radiation pressure on the dynamics and inner structure of dusty wind-driven shells
Martínez-González, Sergio; Silich, Sergiy; Tenorio-Tagle, Guillermo, E-mail: silich@inaoep.mx [Instituto Nacional de Astrofísica Óptica y Electrónica, AP 51, 72000 Puebla (Mexico)
2014-04-20
Massive young stellar clusters are strong sources of radiation and mechanical energy. Their powerful winds and radiation pressure sweep up interstellar gas into thin expanding shells that trap the ionizing radiation produced by the central clusters affecting the dynamics and the distribution of their ionized gas. Here we continue our comparison of the star cluster winds and radiation pressure effects on the dynamics of shells around young massive clusters. We calculate the impact that radiation pressure has on the distribution of matter and thermal pressure within such shells, as well as on the density-weighted ionization parameter U{sub w} , and put our results on the diagnostic diagram, which allows one to discriminate between the wind-dominated and radiation-dominated regimes. We found that model-predicted values of the ionization parameter agree well with typical values found in local starburst galaxies. Radiation pressure may affect the inner structure and the dynamics of wind-driven shells, but only during the earliest stages of evolution (before ∼3 Myr) or if a major fraction of the star cluster mechanical luminosity is dissipated or radiated away within the star cluster volume and thus the star cluster mechanical energy output is significantly smaller than star cluster synthetic models predict. However, even in these cases radiation dominates over the wind dynamical pressure only if the exciting cluster is embedded into a high-density ambient medium.
贺大军
2012-01-01
简要介绍了动压室和静压室合一的喷漆室的缺点以及设计和施工中的处理方法和其使用场合。%The shortcomings, design and the construction of the processing method and its application occasion of dynamic pressure chamber and static pressure chamber syncretic spray paint room were briefly introduced.
Chen, Yuxiang; Luo, Haoze; Li, Wuhua
2017-01-01
In this paper, a dynamic thermo-sensitive electrical parameter (DTSEP) for extracting the junction temperature of the trench gate/field-stop insulated gate bipolar transistor (IGBT) modules by using the maximum collector current falling rate is proposed. First, a theoretical model of the transient...
自动标准压力发生器动态控制准确度分析%Dynamic Control Accuracy Analysis of Automatic Digital Pressure Controller
李海兵; 麻锐; 卓华; 陈武卿
2014-01-01
An additional uncertainty of pressure generators can be introduced to account for control precision. This additional precision is on-ly needed when the controls are in dynamic mode and the operator is using the front panel to display. Herein a calculation method of control preci-sion is displayed for PACE6000 serials pressure generators. It is assumed that a piston gauge is used as standard while a high-precision digital pressure gauge is applied as reference, and when 0.01-class pressure calibrator is used as standard, the uncertainty analysis of 0.05-class digital pressure gauge is shown, and the MPEV ( maximum permissible error value) of inlet-pressure transducer must be ±0.008%.%自动标准压力发生器(以下简称发生器)性能的一个重要指标是准确度。当发生器处于动态控制模式及使用面板显示时需要考虑附加控制准确度。本文通过对PACE6000系列的发生器进行比对实验，以活塞式压力计为标准器，高准确度数字压力计为参考对象，得出了其控制准确度，最后给出了以0.01级数字压力发生器为标准器、0.05级数字压力计示值误差的测量不确定度分析，其内置压力传感器的最大允许误差须为依0.008%。
Brion, Natacha; Carbonnel, Vincent; Elskens, Marc; Claeys, Philippe; Verbanck, Michel A.
2017-04-01
In densely populated regions, human activities profoundly modify natural water circulation as well as water quality, with increased hydrological risks (floods, droughts,…) and chemical hazards (untreated sewage releases, industrial pollution,…) as consequence. In order to assess water and pollutants dynamics and their mass-balance in strongly modified river system, it is important to take into account high flow events as a significant fraction of water and pollutants loads may occur during these short events which are generally underrepresented in classical mass balance studies. A good example of strongly modified river systems is the Zenne river in and around the city of Brussels (Belgium).The Zenne River (Belgium) is a rather small but dynamic rain fed river (about 10 m3/s in average) that is under the influence of strong contrasting anthropogenic pressures along its stretch. While the upstream part of its basin is rather characterized by agricultural land-use, urban and industrial areas dominate the downstream part. In particular, the city of Brussels (1.1M inhabitants) discharges in the Zenne River amounts of wastewater that are large compared to the natural riverine flow. In order to assess water and pollutants dynamics and their mass-balance in the Zenne hydrographic network, we followed water flows and concentrations of several water quality tracers during several flood episodes with an hourly frequency and at different locations along the stretch of the River. These parameters were chosen as indicators of a whole range of pollutions and anthropogenic activities. Knowledge of the high-frequency pollutants dynamics during floods is required for establishing accurate mass-balances of these elements. We thus report here the dynamics of selected parameters during entire flood events, from the baseline to the decreasing phase and at hourly frequency. Dynamics at contrasting locations, in agricultural or urban environments are compared. In particular, the
Huang, Xiaoqin; Tu, Zongcai; Wang, Hui; Zhang, Qiuting; Hu, Yueming; Zhang, Lan; Niu, Peipei; Shi, Yan; Xiao, Hui
2013-12-01
The effect of dynamic high pressure microfluidisation (DHPM) pretreatment on the glycation of bovine serum albumin (BSA) was investigated. A detailed glycation map was obtained from high resolution mass spectrometry. Without DHPM pretreatment, only 7 glycation sites were identified, whereas the numbers were increased to 10, 11 and 11 when BSA-glucose was pretreated with DHPM at 50, 100 and 200 MPa, respectively, suggesting that DHPM pretreatment can significantly promote the Maillard reaction. Average degree of substitution per peptide molecule BSA (DSP) was used to further evaluate the glycation level under various DHPM conditions. All the DHPM pretreated samples exhibited elevated glycation level compared to the un-pretreated sample. With 100 MPa DHPM pretreatment, the protein showed the most significantly enhanced glycation extent. In addition, our results suggest that Maillard-type glycation followed by mass spectrometry analysis can be used to study the conformational changes when proteins are disturbed by external forces.
Dynamic property evaluation of aluminum alloy 2519A by split Hopkinson pressure bar
ZHANG Xin-ming; LI Hui-jie; LI Hui-zhong; GAO Hui; GAO Zhi-guo; LIU Ying; LIU Bo
2008-01-01
Impact behavior of aluminum alloy 2519A was investigated at strain rates of 600-7 000 s-1 and temperatures of 20-450 ℃ by a split Hopkinson pressure bar. The results show that the flow stress is dominated by temperature, and it increases with strain rate and decreases with deformation temperature. The serrated flow curves show the dynamic recrystallization occurs. The strain rate sensitivity exponents m determined are 0.066, 0.059 4, 0.059 0 and 0.057 3 at 20, 150, 300 and 450 ℃, respectively. Cowper- Symonds constitutive equation expressing the plastic flow behavior was calculated by analysis and regression of the experimental results. The fracture characteristics under the experimental conditions were observed by optical microscopy(OM) and scanning electron microscopy(SEM). It is determined that the tested material fails as a result of adiabatic shearing.
Dynamics of cathode spots in low-pressure arc plasma removing oxide layer on steel surfaces
Tang, Z. L.; Yang, K.; Liu, H. X.; Zhang, Y. C.; Li, H.; Zhu, X. D.
2016-03-01
The dynamics of cathode spots has been investigated in low-pressure arc plasma for removing oxide layer on low carbon steel surfaces. The motion of cathode spots was observed with a high speed camera, and the arc voltage was analyzed by fast Fourier transform. The spots move on clean steel surface as a random walk, and the low-frequency components dominated the voltage waveform. However, the spots on steel surfaces with oxide layer tend to burn on the rim of the eroded area formed in the previous arcing, and the low-frequency components decrease correspondingly. The "color" of the colored random noise for arc voltage varies from the approximate brown noise for clean steel surface to pink noise for thick oxide layer, where the edge effect of boundary is considered to play a significant role.
Dynamic neck development in a polymer tube under internal pressure loading
Lindgreen, Britta; Tvergaard, Viggo; Needleman, Alan
2008-01-01
and a short wave length imperfection. After some thinning down at the necks, the mode of deformation switches to neck propagation along the circumference of the tube. A case is shown in which the necks have propagated along the entire tube wall, so that network locking in the polymer results in high stiffness......The initiation and growth of necks in polymer tubes subjected to rapidly increasing internal pressure is analyzed numerically. Plane strain conditions are assumed to prevail in the axial direction. The polymer is characterized by a finite strain elastic-viscoplastic constitutive relation...... and the calculations are carried out using a dynamic finite element program. Numerical results for neck development are illustrated and discussed for tubes of various thicknesses. The sensitivity to the wave number of the thickness imperfections is studied with a focus on comparing a long wave length imperfection...
A regularized model for impact in explicit dynamics applied to the split Hopkinson pressure bar
Otto, Peter; De Lorenzis, Laura; Unger, Jörg F.
2016-10-01
In the numerical simulation of impact phenomena, artificial oscillations can occur due to an instantaneous change of velocity in the contact area. In this paper, a nonlinear penalty regularization is used to avoid these oscillations. A particular focus is the investigation of higher order methods in space and time to increase the computational efficiency. The spatial discretization is realized by higher order spectral element methods that are characterized by a diagonal mass matrix. The time integration scheme is based on half-explicit Runge-Kutta scheme of fourth order. For the conditionally stable scheme, the critical time step is influenced by the penalty regularization. A framework is presented to adjust the penalty stiffness and the time step for a specific mesh to avoid oscillations. The methods presented in this paper are applied to 1D-simulations of a split Hopkinson pressure bar, which is commonly used for the investigation of materials under dynamic loading.
An analysis of the cerebrospinal fluid dynamics in patients with normal pressure hydrocephalus
Mabe, Hideo; Nagai, Hajime (Nagoya City Univ. (Japan). Faculty of Medicine); Banno, Tatsuo
1994-07-01
Using a cine mode technique and a gradient-echo magnetic resonance (MR) sequencing, the MR signal intensity of the aqueduct has been evaluated in twelve patients suspected of normal pressure hydrocephalus (NPH). In patients with a substantial cerebrospinal fluid (CSF) circulation disturbance in the subarachnoid space, marked changes in the signal intensity of the aqueduct were seen during heart cycles, whereas in patients with less of a CSF circulation disturbance, changes in the signal intensity of the aqueduct were not as marked. Further, all patients manifesting marked changes in the signal intensity of the aqueduct showed a clinical improvement in their symptoms after undergoing a shunt. These results suggest that cine-mode MRI is useful for assessing the CSF dynamics and may be helpful in selecting patients who would benefit from shunt therapy. (author).
Argon metastable dynamics in a filamentary jet micro-discharge at atmospheric pressure
Niermann, B; Kuschel, T; Benedikt, J; Böke, M; Winter, J
2011-01-01
Space and time resolved concentrations of Ar ($^{3}P_2$) metastable atoms at the exit of an atmospheric pressure radio-frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. The discharge features a coaxial geometry with a hollow capillary as an inner electrode and a ceramic tube with metal ring as outer electrode. Absorption profiles of metastable atoms as well as optical emission measurements reveal the dynamics and the filamentary structure of the discharge. The average spatial distribution of Ar metastables is characterized with and without a target in front of the jet, showing that the target potential and therewith the electric field distribution substantially changes the filaments' expansion. Together with the detailed analysis of the ignition phase and the discharge's behavior under pulsed operation, the results give an insight into the excitation and de-excitation mechanisms.
Dipolar Relaxation Dynamics at the Active Site of an ATPase Regulated by Membrane Lateral Pressure.
Fischermeier, Elisabeth; Pospíšil, Petr; Sayed, Ahmed; Hof, Martin; Solioz, Marc; Fahmy, Karim
2017-01-24
The active transport of ions across biological membranes requires their hydration shell to interact with the interior of membrane proteins. However, the influence of the external lipid phase on internal dielectric dynamics is hard to access by experiment. Using the octahelical transmembrane architecture of the copper-transporting P1B -type ATPase from Legionella pneumophila as a model structure, we have established the site-specific labeling of internal cysteines with a polarity-sensitive fluorophore. This enabled dipolar relaxation studies in a solubilized form of the protein and in its lipid-embedded state in nanodiscs. Time-dependent fluorescence shifts revealed the site-specific hydration and dipole mobility around the conserved ion-binding motif. The spatial distribution of both features is shaped significantly and independently of each other by membrane lateral pressure. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Theoretical study of dynamics of arterial wall remodeling in response to changes in blood pressure.
Rachev, A; Stergiopulos, N; Meister, J J
1996-05-01
The dynamics of arterial wall remodeling was studied on the basis of a phenomenological mathematical model. Sustained hypertension was simulated by a step increase in blood pressure. Remodeling rate equations were postulated for the evolution of the geometrical dimensions that characterize the zero stress state of the artery. The driving stimuli are the deviations of the extreme values of the circumferential stretch ratios and the average stress from their values at the normotensive state. Arterial wall was considered to be a thick-walled tube made of nonlinear elastic incompressible material. Results showed that thickness increases montonically with time whereas the opening angle exhibits a biphasic pattern. Geometric characteristics reach asymptotically a new homeostatic steady state, in which the stress and strain distribution is practically identical with the distribution under normotensive conditions. The model predictions are in good agreement with published experimental findings.
Moebius, F.; Or, D.
2012-04-01
Many natural and engineering processes involve motion of fluid fronts in porous media, from infiltration and drainage in hydrology to reservoir management in petroleum engineering. Macroscopically smooth and continuous motion of displacement fronts involves numerous rapid interfacial jumps and local reconfigurations. Detailed observations of displacement processes in micromodels illustrate the wide array of fluid interfacial dynamics ranging from irregular jumping-pinning motions to gradual pore scale invasions. The pressure fluctuations associated with interfacial motions reflect not only pore geometry (as traditionally hypothesized) but there is a strong influence of boundary conditions (e.g., mean drainage rate). The time scales associated with waiting time distribution of individual invasion events and decay time of inertial oscillations (following a rapid interfacial jump) provide a means for distinguishing between displacement regimes. Direct observations using high-speed camera combined with concurrent pressure signal measurements were instrumental in clarifying influences of flow rates, pore size, and gravity on burst size distribution and waiting times. We compared our results with the early experimental and theoretical study on burst size and waiting time distribution during slow drainage processes of Måløy et al. [Måløy et al., 1992]. Results provide insights on critical invasion events that exert strong influence on macroscopic phenomena such as front morphology and residual phase entrapment behind leading to hysteresis. Måløy, K. J., L. Furuberg, J. Feder, and T. Jossang (1992), Dynamics of Slow Drainage in Porous-Media, Phys Rev Lett, 68(14), 2161-2164.
Effects of the van der Waals Force on the Dynamics Performance for a Micro Resonant Pressure Sensor
Lizhong Xu
2016-01-01
Full Text Available The micro resonant pressure sensor outputs the frequency signals where the distortion does not take place in a long distance transmission. As the dimensions of the sensor decrease, the effects of the van der Waals forces should be considered. Here, a coupled dynamic model of the micro resonant pressure sensor is proposed and its coupled dynamic equation is given in which the van der Waals force is considered. By the equation, the effects of the van der Waals force on the natural frequencies and vibration amplitudes of the micro resonant pressure sensor are investigated. Results show that the natural frequency and the vibrating amplitudes of the micro resonant pressure sensor are affected significantly by van der Waals force for a small clearance between the film and the base plate, a small initial tension stress of the film, and some other conditions.
Quantum molecular dynamics simulations of uranium at high pressure and temperature
Hood, R Q; Yang, L H; Moriarty, J A
2008-01-22
Constant-volume quantum molecular dynamics (QMD) simulations of uranium (U) have been carried out over a range of pressures and temperatures that span the experimentally observed solid orthorhombic {alpha}-U, body-centered cubic (bcc), and liquid phases, using an ab initio plane-wave pseudopotential method within the generalized gradient approximation of density functional theory. A robust U pseudopotential has been constructed for these simulations that treats the 14 valence and outer-core electrons per atom necessary to calculate accurate structural and thermodynamic properties up to 100 GPa. Its validity has been checked by comparing low-temperature results with experimental data and all-electron full-potential linear-muffin-tin-orbital calculations of several different uranium solid structures. Calculated QMD energies and pressures for the equation of state of uranium in the solid and liquid phases are given, along with results for the Grueneisen parameter and the specific heat. We also present results for the radial distribution function, bond-angle distribution function, electronic density of states, and liquid diffusion coefficient, as well as evidence for short-range order in the liquid.
Transonic Dynamics Tunnel Force and Pressure Data Acquired on the HSR Rigid Semispan Model
Schuster, David M.; Rausch, Russ D.
1999-01-01
This report describes the aerodynamic data acquired on the High Speed Research Rigid Semispan Model (HSR-RSM) during NASA Langley Transonic Dynamics Tunnel (TDT) Test 520 conducted from 18 March to 4 April, 1996. The purpose of this test was to assess the aerodynamic character of a rigid high speed civil transport wing. The wing was fitted with a single trailing edge control surface which was both steadily deflected and oscillated during the test to investigate the response of the aerodynamic data to steady and unsteady control motion. Angle-of-attack and control surface deflection polars at subsonic, transonic and low-supersonic Mach numbers were obtained in the tunnel?s heavy gas configuration. Unsteady pressure and steady loads data were acquired on the wing, while steady pressures were measured on the fuselage. These data were reduced using a variety of methods, programs and computer systems. The reduced data was ultimately compiled onto a CD-ROM volume which was distributed to HSR industry team members in July, 1996. This report documents the methods used to acquire and reduce the data, and provides an assessment of the quality, repeatability, and overall character of the aerodynamic data measured during this test.
Influence of dynamic pressure on deep underground soft rock roadway support and its application
Meng Qingbin; Han Lijun; Chen Yanlong; Fan Jiadong; Wen Shengyong; Yu Liyuan; Li Hao
2016-01-01
Due to high ground stress and mining disturbance, the deformation and failure of deep soft rock roadway is serious, and invalidation of the anchor net-anchor cable supporting structure occurs. The failure char-acteristics of roadways revealed with the help of the ground pressure monitoring. Theoretical analysis was adopted to analyze the influence of mining disturbance on stress distribution in surrounding rock, and the change of stress was also calculated. Considering the change of stress in surrounding rock of bot-tom extraction roadway, the displacement, plastic zone and distribution law of principal stress difference under different support schemes were studied by means of FLAC3D. The supporting scheme of U-shaped steel was proposed for bottom extraction roadway that underwent mining disturbance. We carried out a similarity model test to verify the effect of support in dynamic pressure. Monitoring results demonstrated the change rules of deformation and stress of surrounding rock in different supporting schemes. The supporting scheme of U-shaped steel had an effective control on deformation of surrounding rock. The scheme was successfully applied in underground engineering practice, and achieved good technical and economic benefits.
Dynamics and Conservation Management of a Wooded Landscape under High Herbivore Pressure
Adrian C. Newton
2013-01-01
Full Text Available We present the use of a spatially explicit model of woodland dynamics (LANDIS-II to examine the impacts of herbivory in the New Forest National Park, UK, in relation to its management for biodiversity conservation. The model was parameterized using spatial data and the results of two field surveys and then was tested with results from a third survey. Field survey results indicated that regeneration by tree species was found to be widespread but to occur at low density, despite heavy browsing pressure. The model was found to accurately predict the abundance and richness of tree species. Over the duration of the simulations (300 yr, woodland area increased in all scenarios, with or without herbivory. While the increase in woodland area was most pronounced under a scenario of no herbivory, values increased by more than 70% even in the presence of heavy browsing pressure. Model projections provided little evidence for the conversion of woodland areas to either grassland or heathland; changes in woodland structure and composition were consistent with traditional successional theory. These results highlight the need for multiple types of intervention when managing successional landscape mosaics and demonstrate the value of landscape-scale modelling for evaluating the role of herbivory in conservation management.
Zuo, Pingbing; Feng, Xueshang; Wang, Yi [SIGMA Weather Group, State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing (China); Xie, Yanqiong [College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing (China); Xu, Xiaojun, E-mail: pbzuo@spaceweather.ac.cn, E-mail: fengx@spaceweather.ac.cn [Space Science Institute, Macau University of Science and Technology, Macao (China)
2015-10-20
In this investigation, we first present a statistical result of the interplanetary sources of very strong solar wind dynamic pressure pulses (DPPs) detected by WIND during solar cycle 23. It is found that the vast majority of strong DPPs reside within solar wind disturbances. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears to be no systematic investigations on the response of GMFs to negative DPPs. Here, we study both the decompression effects of very strong negative DPPs and the compression from strong positive DPPs on GMFs at different magnetic local time sectors. In response to the decompression of strong negative DPPs, GMFs on the dayside near dawn and near dusk on the nightside, are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of the events when GOES is located at the midnight sector, the GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that under certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here, we find that a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at the midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, which are stronger at the noon sector.
Static and dynamic tensile behaviour of aluminium processed by high pressure torsion
Verleysen Patricia
2015-01-01
Full Text Available High pressure torsion (HPT is a severe plastic deformation technique in which a small, disk-like sample is subjected to a torsional deformation under a high hydrostatic pressure. In present study, the static and dynamic tensile behaviour of commercially pure aluminium (99.6 wt% processed by HPT is studied. The high strain rate tensile behaviour is characterized using a purpose-developed miniature split Hopkinson tensile bar setup by which strain rates up to 5 × 103 s−1 can be reached. During the tests, the deformation of a speckle pattern applied to the samples is recorded, by which local information on the strain is obtained using a digital image correlation technique. Electron back scatter diffraction images are used to investigate the microstructural evolution, more specifically the grain refinement obtained by HPT. The fracture surfaces of the tensile samples are studied by scanning electron microscopy. Results show that the imposed severe plastic deformation significantly increases the tensile strength, however, at the expense of ductility. The strain rate only has a minor influence on the materials tensile behaviour.
Jiang, Yan-Fei; Cantiello, Matteo; Bildsten, Lars; Quataert, Eliot; Blaes, Omer
2017-07-01
We use three-dimensional radiation magnetohydrodynamic simulations to study the effects of magnetic fields on the energy transport and structure of radiation pressure-dominated main sequence massive star envelopes at the region of the iron opacity peak. We focus on the regime where the local thermal timescale is shorter than the dynamical timescale, corresponding to inefficient convective energy transport. We begin with initially weak magnetic fields relative to the thermal pressure, from 100 to 1000 G in differing geometries. The unstable density inversion amplifies the magnetic field, increasing the magnetic energy density to values close to equipartition with the turbulent kinetic energy density. By providing pressure support, the magnetic field’s presence significantly increases the density fluctuations in the turbulent envelope, thereby enhancing the radiative energy transport by allowing photons to diffuse out through low-density regions. Magnetic buoyancy brings small-scale magnetic fields to the photosphere and increases the vertical energy transport, with the energy advection velocity proportional to the Alfvén velocity, although in all cases we study, photon diffusion still dominates the energy transport. The increased radiative and advective energy transport causes the stellar envelope to shrink by several scale heights. We also find larger turbulent velocity fluctuations compared with the purely hydrodynamic case, reaching ≈ 100 {{{km}}{{s}}}-1 at the stellar photosphere. The photosphere also shows vertical oscillations with similar averaged velocities and periods of a few hours. The increased turbulent velocity and oscillations will have strong impacts on the line broadening and periodic signals in massive stars.
Plantier, F., E-mail: frederic.plantier@univ-pau.fr; Missima, D.; Torré, J.-P. [Univ Pau and Pays Adour, CNRS, TOTAL - UMR 5150 – LFC-R - Laboratoire des Fluides Complexes et leurs Réservoirs, BP 1155 – PAU, F-64013 (France); Marlin, L. [Univ Pau and Pays Adour, IPRA FR2952 - Fédération de Recherche- Atelier de Physique Générale, BP 1155 – PAU, F-64013 (France)
2013-12-15
A novel prototype of calorimetric cell has been developed allowing experiments under pressure with an in situ agitation system and a dynamic control of the pressure inside the cell. The use of such a system opens a wide range of potential practical applications for determining properties of complex fluids in both pressurized and agitated conditions. The technical details of this prototype and its calibration procedure are described, and an application devoted to the determination of phase equilibrium and phase change enthalpy of gas hydrates is presented. Our results, obtained with a good precision and reproducibility, were found in fairly good agreement with those found in literature, illustrate the various interests to use this novel apparatus.
Van Allen Probes observations of EMIC events triggered by solar wind dynamic pressure enhancements
Lee, D. Y.; Cho, J.; Roh, S. J.; Shin, D. K.; Hwang, J.; Kim, K. C.; Choi, C.; Kletzing, C.; Wygant, J. R.; Thaller, S. A.; Larsen, B.; Skoug, R. M.
2015-12-01
Electromagnetic ion cyclotron (EMIC) waves are one of the key plasma waves that can affect charged particle dynamics in the Earth's inner magnetosphere. One of the generation mechanisms of EMIC waves has long been known to be due to magnetospheric compression due to impact by enhanced solar wind dynamic pressure Pdyn. With the Van Allen Probes observations, we have identified 4 EMIC wave events that are triggered by Pdyn enhancements under northward IMF, prolonged quiet time conditions. We find the following features of the EMIC events. (1) They are triggered immediately at the Pdyn impact and remain active during the same period as the enhanced Pdyn duration. (2) They occur in either H band or He band or both. (3) Two events occur inside the plasmasphere and the other two outside the plasmasphere. (4) The wave polarization, either R or L, are highly elliptical, being close to be linear. (5) The wave normal angles are quite large, well away from being field-aligned. (6) About 10 - 50 keV proton fluxes indicate enhanced flux state with ~90 deg-peaked anisotropy in velocity distribution after the Pdyn impact. (7) From low altitude NOAA POES satellite observations of particles we find no obvious evidence for relativistic electron precipitation due to these Pdyn-triggered EMIC events. We will discuss implications of these observations on wave generation mechanism and interaction with radiation belt electrons.
Lattice dynamics of CaSiO3 at high temperatures and pressures
Holiday, A.; Sun, T.; Zhang, D.; Wentzcovitch, R. M.
2012-12-01
Cubic CaSiO3-perovskite is a minor but important phase of the Earth's lower mantle. Its thermodynamics and elastic properties have been investigated by multiple techniques but its behavior at lower mantle conditions is still elusive. It is a mechanically unstable phase at low temperatures but it is stabilized at lower mantle temperatures. We have investigated its vibrational properties at high pressures and temperatures of the lower mantle. We have projected ionic velocities from ab initio molecular dynamics trajectories onto vibrational normal modes and computed the mode-mode correlation functions from which we extract phonon frequencies and life times at finite temperatures. These correlations clearly indicate that normal modes with imaginary frequencies at 0 K are stabilized with increasing temperature. To overcome the finite size effect inherent in molecular dynamics simulations, a renormalized second-order force constant matrix in real space is constructed from the phonon frequencies at finite temperature and the phonon polarization vectors. Phonon dispersions and vibrational density of states are then determined by Fourier interpolation using the renormalized force constant matrix. These temperature dependent dispersions allow us to investigate thermodynamics and thermal elastic properties at lower mantle conditions.
Lattice dynamics of cubic CaSiO3 perovskite at high temperatures and pressures
Sun, Tao; Zhang, Dong-Bo; Wentzcovitch, Renata M.
2013-03-01
Cubic CaSiO3-perovskite is a minor but important phase of the Earth's lower mantle. It is a mechanically unstable phase at low temperatures but it is stabilized at lower mantle temperatures. We have investigated its vibrational properties at high pressures and temperatures of the lower mantle. We have projected ionic velocities from ab initio molecular dynamics trajectories onto vibrational normal modes and computed the mode-mode correlation function from which we extract phonon frequencies and life times at finite temperatures. These correlations clearly indicate that normal modes with imaginary frequencies at 0 K are stabilized with increasing temperature. To overcome the finite size effect inherent in molecular dynamics simulations, a renormalized second-order force constant matrix in real space is constructed from the phonon frequencies at finite temperature and the phonon polarization vectors. Phonon dispersions and vibrational density of states are then determined by Fourier interpolation using the renormalized force matrix. These temperature dependent dispersions allow us to investigate thermodynamics and thermal elastic properties at lower mantle conditions. Supported by NSF Grants EAR-1047626 and EAR-0810272.
Abuzairi, Tomy; Okada, Mitsuru; Bhattacharjee, Sudeep; Nagatsu, Masaaki
2016-12-01
An experimental study on the dynamic behaviour of microcapillary atmospheric pressure plasma jets (APPJs) with 5 μm tip size for surfaces of different conductivity is reported. Electrical and spatio-temporal characteristics of the APPJs are monitored using high voltage probe, current monitor and high speed intensified charge couple device camera. From these experimental results, we presented a simple model to understand the electrical discharge characteristics of the capillary APPJs with double electrodes, and estimated the velocity of the ionization fronts in the jet and the electron density to be 3.5-4.2 km/s and 2-7 × 1017 m-3. By analyzing the dynamics of the microcapillary APPJs for different substrate materials, it was found that the surface irradiation area strongly depended on the substrate conductivity and permittivity, especially in the case of polymer-like substrate, surface irradiation area was significantly broadened probably due to the repelling behaviour of the plasma jets from the accumulated electrical charges on the polymer surface. The effect of applying a substrate bias in the range from -900 V to +900 V on the plasma irradiation onto the substrates was also investigated. From the knowledge of the present results, it is helpful for choosing the substrate materials for microscale surface modification.
Shashikumar, Supreeth P; Stanley, Matthew D; Sadiq, Ismail; Li, Qiao; Holder, Andre; Clifford, Gari D; Nemati, Shamim
2017-08-16
Sepsis remains a leading cause of morbidity and mortality among intensive care unit (ICU) patients. For each hour treatment initiation is delayed after diagnosis, sepsis-related mortality increases by approximately 8%. Therefore, maximizing effective care requires early recognition and initiation of treatment protocols. Antecedent signs and symptoms of sepsis can be subtle and unrecognizable (e.g., loss of autonomic regulation of vital signs), causing treatment delays and harm to the patient. In this work we investigated the utility of high-resolution blood pressure (BP) and heart rate (HR) times series dynamics for the early prediction of sepsis in patients from an urban, academic hospital, meeting the third international consensus definition of sepsis (sepsis-III) during their ICU admission. Using a multivariate modeling approach we found that HR and BP dynamics at multiple time-scales are independent predictors of sepsis, even after adjusting for commonly measured clinical values and patient demographics and comorbidities. Earlier recognition and diagnosis of sepsis has the potential to decrease sepsis-related morbidity and mortality through earlier initiation of treatment protocols. Copyright © 2017 Elsevier Inc. All rights reserved.
Bigikocin, Erman; Mert, Behic; Alpas, Hami
2011-09-01
Both static and dynamic high pressure applications provide interesting modifications in food structures which lead to new product formulations. In this study, the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP), on oil-in-water emulsions were identified and compared. Microfluidization was selected from among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared with the coarse emulsions. The stability of the emulsions was determined comparatively by using an analytical photo-centrifuge device employing novel analysis technology. Whey protein isolate (WPI) in combination with a food polysaccharide (xanthan gum, guar gum or locust bean gum) were used as emulsifying and stabilizing ingredients. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities, leading to distinctive improvements in emulsion stability. On the other hand, improvements in stability obtained with HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations containing higher oil content. Apart from these, HHP treatment was found to be relatively more contributive to the enhancements in viscoelastic properties.
王进廷; 张楚汉; 金峰
2004-01-01
Wave reflection and refraction in layered media is a topic closely related to seismology, acoustics, geophysics and earthquake engineering. Analytical solutions for wave reflection and refraction coefficients in multi-layered media subjected to P wave incidence from the elastic half-space are derived in terms of displacement potentials. The system is composed of ideal fluid, porous medium, and underlying elastic solid. By numerical examples, the effects of porous medium and the incident wave angle on the dynamic pressures of ideal fluid are analyzed. The results show that the existence of the porous medium, especially in the partially saturated case, may significantly affect the dynamic pressures of the overlying fluid.
Savin, Sergey; Büchner, Jörg; Zelenyi, Lev; Kronberg, Elena; Kozak, Lyudmila; Blecki, Jan; Lezhen, Liudmila; Nemecek, Zdenek; Safrankova, Jana; Skalsky, Alexander; Budaev, Vyacheslav; Amata, Ermanno
We explore interactions of Supersonic Plasma Streams (SPS) with the Earth magnetosphere in the context of the planetary and astrophysical magnetospheres and of that of laboratory plasmas. The interactions can be inherently non-local and non-equilibrium, and even explosive due to both solar wind (SW) induced and self-generated coherent structures in the multiscale system with the scales ranging from the micro to global scales. We concentrate on the main fundamental processes arising from the SPS cascading and interactions with surface and cavity resonances in the Earth’s magnetosphere, using multi-spacecraft data (SPECTR-R, DOUBLE STAR, CLUSTER, GEOTAIL, ACE, WIND etc.). We will address the following key problems to advance our understanding of anomalous transport and boundary dynamics: - generalizations of the SPS generation mechanisms, e.g., by bow shock (BS) surface or magnetosheath (MSH) cavity resonances, triggering by interplanetary shocks, solar wind (SW) dynamic pressure jumps, foreshock nonlinear structures, etc. - the clarification of BS rippling mechanisms requires base on the relevant databases from the CLUSTER/ DOUBLE STAR/ GEOTAIL/SPECTR-R/ ACE/ WIND spacecraft, which will be used for a statistical analysis targeting the SPS statistical features as extreme events. - substantial part of the SW kinetic energy can be pumped into the BS membrane and MSH cavity modes and initiate further cascades towards higher frequencies. Accordingly we present the multipoint studies of the SPS and of related nonlinear discrete cascades (carried generally by the SPS), along with the transformation of discrete cascades of the dynamic pressure into turbulent cascades. - investigation of spectral and bi-spectral cross-correlations in SW, foreshock, MSH and in vicinity of BS and magnetopause (MP) would demonstrate that both inflow and outflow into/ from magnetosphere can be modulated by the SPS and by the related outer magnetospheric resonances as well. We demonstrate in
Niebling, Michael J.; Toussaint, Renaud; Flekkøy, Eirik G.; Jørgen Måløy, Knut
2013-04-01
Stress induced by fluid or gases can cause diverse materials to break and fracture. Such hydraulic fractures are a natural and common phenomenon in the field of volcanism and are artificially initiated to enhance the recovery of natural gas and mineral oil by fracturing the reservoir rock with pressurized fluids. A procedure also known as fracking. Recently a new perspective on hydrofractures was added with the storage of supercritical CO2. In this respect two scenarios are considered. First it is one option to inject CO2 into existing hydrofractures, and second the injection of the CO2 can create additional fractures. The typical components for such fractures are a porous material and a compressible gas. The dynamics of such fractures and displacement patterns are simulated and studied in a rectangular Hele-Shaw cell filled with a dense but permeable two-dimensional granular layer. The model used, mixing highly deformable solid and fluid components, can simulate sedimentation problems [1,2], as well as hydrofracture or aerofracture ones. The emerging displacement patterns and fractures variate according to the properties of the injected fluid or gas and the characteristics of the granular phase [3]. The physics behind these variations is discussed and explained. The role of the fluid viscosity and system size shows to lead to a transition from fracturing to compaction, depending on the dynamics of convection versus diffusion of overpressure. The dependence of the obtained patterns on the injection pressure is also explored [4]. References: [1] Niebling, M.J., E.G. Flekkøy, K.J. Måløy, R. Toussaint, Sedimentation instabilities: impact of the fluid compressibility and viscosity, Phys. Rev. E 82, 051302, 2010. doi: 10.1103/PhysRevE.82.051302 [2] Niebling, M.J., E.G. Flekkøy, K.J. Måløy, R. Toussaint, Mixing of a granular layer falling through a fluid, Phys. Rev. E 82, 011301 (2010) doi: 10.1103/PhysRevE.82.011301 [3] Niebling, M., R. Toussaint, E.G. Flekk
Coffin, T.
1986-01-01
A dynamic pressure data base and data base management system developed to characterize the Space Shuttle Main Engine (SSME) dynamic pressure environment is presented. The data base represents dynamic pressure measurements obtained during single engine hot firing tests of the SSME. Software is provided to permit statistical evaluation of selected measurements under specified operating conditions. An interpolation scheme is also included to estimate spectral trends with SSME power level.
Gong, Mao-lei; Liu, Da-wei; Wang, Xiao-ting; Chen, Xiu-kai
2013-05-07
To explore the value of dynamic arterial elastance (Eadyn) in the predication of arterial pressure response to volume loading in shock patients. A total of 32 patients with pulse indicator continuous cardiac output (PICCO) monitoring at our intensive care unit from January 2011 to December 2012 were retrospectively studied. The decision of fluid replacement was based upon the presence of shock (mean arterial pressure (MAP) ≤ 65 mm Hg, systolic arterial pressure arterial pressure response to volume loading. Significantly different between MAP responders and MAP nonresponders, baseline Eadyn was an effective predictor of MAP increase after volume loading. The area under the ROC curve was 0.95 for the prediction of volume loading on MAP for Eadyn at baseline (P 0.85 predicted a MAP increase after volume administration with a sensitivity of 89.5% and a specificity of 92.3%. Baseline Eadyn may predict accurately arterial pressure response in MAP to volume loading in shock patients.
Zhang, Zi-Long; Chen, Xing-Peng; Yang, Jing; Xue, Bing; Li, Yong-Jin
2010-02-01
Based on the ideology of macro environmental economics, a function of environmental pressure represented by pollutant emission was built, and the relative importance of the driving factors in the dynamic changes of the relationships between economic growth and environmental pressure in Gansu Province in 1990 - 2005 was analyzed by using structural decomposition analysis (SDA) model combining with 'refined Laspeyres' method. In the study period, the environmental pressure in the Province was mainly caused by the emission of waste gases and solids in the process of economic growth, and showed a rapid increasing trend at the late stage of the period. Population factor had less impact on the increase of this environmental pressure, while economic growth factor had obvious impact on it. Technological progress did mitigate, but could not offset the impact of economic growth factor, and the impacts of economic growth and technological factors on the environmental pressure differed with the kinds of pollutants.
Dynamic Runner Forces and Pressure Fluctuations on the Draft Tube Wall of a Model Pump-Turbine
Kirschner, O.; Ruprecht, A.; Göde, E.; Riedelbauch, S.
2016-11-01
When Francis-turbines and pump-turbines operate at off-design conditions, typically a vortex rope develops. The vortex rope causes pressure oscillations leading to fluctuations of the forces affecting the runner. The presence of dynamic runner forces over a long period of time might damage the bearings and possibly the runner. In this experimental investigation, the fluctuating part of the runner forces and the pressure oscillations on the draft tube wall were measured on a model pump-turbine with a simplified straight cone draft tube in different operating conditions. The investigation focuses on the correlation of the pressure fluctuations frequency measured at the draft tube wall with the frequency of the fluctuating forces on the runner. The comparison between pressure fluctuations and dynamic forces shows a significant correlation in all operating points. For the comparison of different components in the spatial directions of the forces, the pressure fluctuations were separated in a synchronous part and a rotating part for operating points with higher amplitudes. The rotating pressure fluctuations correlate with the radial forces especially in the operating points with a rotating vortex rope. At frequencies with higher amplitudes in the pressure fluctuations caused by the vortex rope movement, there are also higher amplitudes in the radial forces at the same frequencies.
Ullán, Aurora; Zorzano, María-Paz; Javier Martín-Torres, Francisco; Valentín-Serrano, Patricia; Kahanpää, Henrik; Harri, Ari-Matti; Gómez-Elvira, Javier; Navarro, Sara
2017-05-01
The Rover Environmental Monitoring Station (REMS) instrument on-board the Mars Science Laboratory (MSL) has acquired unprecedented measurements of key environmental variables at the base of Gale Crater. The pressure measured by REMS shows modulations with a very structured pattern of short-time scale (of the order of seconds to several minutes) mild fluctuations (typically up to 0.2 Pa at daytime and 1 Pa at night-time). These dynamic pressure oscillations are consistent with wind, air and ground temperature modulations measured simultaneously by REMS. We detect the signals of a repetitive pattern of upslope/downslope winds, with maximal speeds of about 21 m/s, associated with thermal changes in the air and surface temperatures, that are initiated after sunset and finish with sunrise proving that Gale, a 4.5 km deep impact crater, is an active Aeolian environment. At nighttime topographic slope winds are intense with maximal activity from 17:00 through 23:00 Local Mean Solar Time, and simultaneous changes of surface temperature are detected. During the day, the wind modulations are related to convection of the planetary boundary layer, winds are softer with maximum wind speed of about 14 m/s. The ground temperature is modulated by the forced convection of winds, with amplitudes between 0.2 K and 0.5 K, and the air temperatures fluctuate with amplitudes of about 2 K. The analysis of more than one and a half Martian years indicates the year-to-year repeatability of these environmental phenomena. The wind pattern minimizes at the beginning of the south hemisphere winter (Ls 90) season and maximizes during late spring and early summer (Ls 270). The procedure that we present here is a useful tool to investigate in a semi-quantitative way the winds by: i) filling both seasonal and diurnal gaps where wind measurements do not exist, ii) providing an alternative way for comparisons through different measuring principia and, iii) filling the gap of observation of short
Nicolae, Andrei
The solid-state process has been successful in creating microcellular foams in a number of thermoplastic polymers using sub-critical CO2 in the 3-5 MPa range. In this process, the polymer film or sheet is first saturated with CO2 in a pressure vessel. The gas saturated film is then removed from the pressure vessel and heated in a suitable medium (liquid or hot air, for example) to create a microcellular structure. The time elapsed from depressurization of the pressure vessel to the heating of the gas-saturated film, known as the desorption time, is an important process parameter that can range from a few minutes in a laboratory environment to tens of minutes in a manufacturing environment. During the desorption time, the absorbed gas leaves the polymer film. This loss of gas becomes increasingly critical as the film thickness is reduced; polymer films below 0.010" in thickness are difficult or impossible to foam in the current solid-state batch process. To successfully foam thin films it is necessary for the polymer to retain the absorbed gas prior to heating. Towards this end, a dynamic seal was developed that allows a polymer film/filament to be smoothly drawn out of a pressure vessel while preventing the pressurized gas from escaping. The dynamic seal is based on the idea of using a liquid (e.g. water) to provide a seal and keep the pressurized gas from escaping. The liquid thus experiences the same pressure as the gas. Liquid leakage is controlled to within an acceptable limit by designing sufficient resistance to the flow. The early prototypes showed that a pressure of 5 MPa could be maintained in a small pressure vessel, while a 0.4 mm nylon fishing line was drawn through the seal. Water was used to seal the gas in this case. It was quickly apparent that the key challenge would be to move, or draw, the polymer film through the seal mechanism while keeping its integrity. The key is to strike a balance between sealing forces that keep the leakage rate low and
Dynamic response of brittle materials from penetration and split Hopkinson pressure bar experiments
Frew, Danny Joe
This research began with a study on the penetration of limestone targets with ogive-nose rod projectiles. Three sets of experiments were conducted with geometrically similar, steel rod projectiles that had length-to-diameter ratios of 10 and 7.1, 12.7, and 25.4-mm-diameters. Results from these penetration experiments and previously developed penetration models suggested that the limestone target exhibited strain-rate sensitivity. In order to investigate this hypothesis, an experimental/analytical program to study the dynamic material response of limestone was begun. As a first step, it was decided to focus on the dynamic material responses of brittle materials, such as limestone, under a state of one-dimensional stress. A split Hopkinson pressure bar (SHPB) facility was built at the Geotechnical and Structures Laboratory, U.S. Army Waterways Experiment Station. Early in the experimental program it became clear that new modifications had to be made to the traditional SHPB apparatus and experimental techniques. In addition, it was decided to model the responses of the SHPB apparatus and the sample under test in order to guide the experimental designs and minimize the experimental trials. The conventional split Hopkinson pressure bar apparatus was modified by shaping the incident pulse such that the samples are in dynamic stress equilibrium and have nearly constant strain rate over most of the test duration. A thin disk of annealed or hard C11000 copper is placed on the impact surface of the incident bar in order to shape the incident pulse. After impact by the striker bar, the copper disk deforms plastically and spreads the pulse in the incident bar. An analytical model and data show that a wide variety of incident strain pulses can be produced by varying the geometry of the copper disks and the length and striking velocity of the striker bar. The pulse shaping model predictions are in good agreement with measurements. Analytic models predict that a ramp stress pulse
Rosingh, HJ; Wit, HP; Albers, FWJ
1998-01-01
The hydrostatic pressure of the inner ear depends on the cerebrospinal fluid pressure through the cochlear aqueduct. The time-course of inner ear pressure change following rapid change in cerebrospinal fluid pressure is related to the aqueduct patency. In this study the patency of the cochlear aqued
A Study of the Fluid-Dynamic Pressure Fields on Compressor Reed Valves.
1985-12-01
nigher *A pressures. The total pressure ol the reservoir wnicn suppiieo the air was measured on either a lovi-incn mercury manometer or a3 -v)-incn... mercury manometer . This was the same manometer which was used to measure the total pressure of the reservoir. A pressure tap ran from this total
Rosingh, HJ; Wit, HP; Albers, FWJ
The hydrostatic pressure of the inner ear depends on the cerebrospinal fluid pressure through the cochlear aqueduct. The time-course of inner ear pressure change following rapid change in cerebrospinal fluid pressure is related to the aqueduct patency. In this study the patency of the cochlear
Y. Shi
2009-02-01
Full Text Available Determination of the radial profile of phase space density of relativistic electrons at constant adiabatic invariants is crucial for identifying the source for them within the outer radiation belt. The commonly used method is to convert flux observed at fixed energy to phase space density at constant first, second and third adiabatic invariants, which requires an empirical global magnetic field model and thus might produce some uncertainties in the final results. From a different perspective, in this paper we indirectly infer the shape of the radial profile of phase space density of relativistic electrons near the geosynchronous region by statistically examining the geosynchronous energetic flux response to 128 solar wind dynamic pressure enhancements during the years 2000 to 2003. We thus avoid the disadvantage of using empirical magnetic field models. Our results show that the flux response is species and energy dependent. For protons and low-energy electrons, the primary response to magnetospheric compression is an increase in flux at geosynchronous orbit. For relativistic electrons, the dominant response is a decrease in flux, which implies that the phase space density decreases toward increasing radial distance at geosynchronous orbit and leads to a local peak inside of geosynchronous orbit. The flux response of protons and non-relativistic electrons could result from a phase density that increases toward increasing radial distance, but this cannot be determined for sure due to the particle energization associated with pressure enhancements. Our results for relativistic electrons are consistent with previous results obtained using magnetic field models, thus providing additional confirmation that these results are correct and indicating that they are not the result of errors in their selected magnetic field model.
Kang, Shin K., E-mail: paengki1@tamu.edu; Hassan, Yassin A.
2016-05-15
Highlights: • The capabilities of steady RANS models were directly assessed for full axial scale experiment. • The importance of mesh and conjugate heat transfer was reaffirmed. • The rod inner-surface temperature was directly compared. • The steady RANS calculations showed a limitation in the prediction of circumferential distribution of the rod surface temperature. - Abstract: This study examined the capabilities and limitations of steady Reynolds-Averaged Navier–Stokes (RANS) approach for pressurized water reactor (PWR) rod bundle problems, based on the round robin benchmark of computational fluid dynamics (CFD) codes against the NESTOR experiment for a 5 × 5 rod bundle with typical split-type mixing vane grids (MVGs). The round robin exercise against the high-fidelity, broad-range (covering multi-spans and entire lateral domain) NESTOR experimental data for both the flow field and the rod temperatures enabled us to obtain important insights into CFD prediction and validation for the split-type MVG PWR rod bundle problem. It was found that the steady RANS turbulence models with wall function could reasonably predict two key variables for a rod bundle problem – grid span pressure loss and the rod surface temperature – once mesh (type, resolution, and configuration) was suitable and conjugate heat transfer was properly considered. However, they over-predicted the magnitude of the circumferential variation of the rod surface temperature and could not capture its peak azimuthal locations for a central rod in the wake of the MVG. These discrepancies in the rod surface temperature were probably because the steady RANS approach could not capture unsteady, large-scale cross-flow fluctuations and qualitative cross-flow pattern change due to the laterally confined test section. Based on this benchmarking study, lessons and recommendations about experimental methods as well as CFD methods were also provided for the future research.
Ariga, Katsuhiko; Nakanishi, Takashi; Terasaka, Yukiko; Tsuji, Hiromitsu; Sakai, Daisuke; Kikuchi, Jun-ichi
2005-02-01
The steroid cyclophanes with a cyclic core consisting of a 1,6,20,25-tetraaza[6.1.6.1]paracyclophane connected to four steroid moieties (cholic acid or cholanic acid) through a flexible l-lysine spacer were spread on water as Langmuir monolayers. The pi-A isotherm of the cholic-type steroid cyclophane includes a transition to the condensed phase with a limiting area of approximately 2 nm(2). This value is close to the cross-sectional area of the steroid cyclophane with a standing-up conformation of the cholic acid moieties, strongly suggesting that the cavity converts from a two-dimensional cavity to a three-dimensional cavity upon compressing the monolayer. Surface-reflective fluorescence spectroscopy of the monolayer using an aqueous fluorescent probe (6-(p-toluidino)naphthalene-2-sulfonate (TNS)) showed an abrupt increase in the TNS fluorescence intensity at a molecular area of 2 nm(2). Efficient binding of the guest probe would occur upon the completion of the three-dimensional cavity. Repeated compression and expansion induces periodic changes in the fluorescence intensity. This indicates a piezoluminescence effect through the catch and release of the TNS guest upon dynamic cavity formation. Analyses of the binding behavior of TNS to the steroid cyclophane resulted in binding constants in the range of approximately (5-9) x 10(4) M(-1) which are similar to that observed in lipid bilayer media (K = 5.1 x 10(4) M(-1)). The fluorescence intensity within the condensed phase was significantly increased with increasing pressure, suggesting that suppression of the molecular motion of the bound TNS may retard the nonemission process. Similar monolayer experiments were carried out with the monolayer of the cholanic-type steroid cyclophane that cannot form an open conformation on water. Both the phase transition in the pi-A isotherm and the change in the fluorescence intensity were negligible, confirming that the dynamic characteristic of the cavity is indispensable for
The dynamic scale display digital pressure gauge%动态刻度显示数字压力表
王浩
2014-01-01
The dynamic scale display digital pressure gauge provides an intuitive dynamic pressure scale display, which not only uses the same digital pressure gauge and general digital display pressure values, and can be used LED string light off analog disc mechanical pressure gauge pointer indicates the instant value of the pressure, with the LED lights steady visual analog display measuring signal set upper limit, lower limit value.%针对现有数字压力表在显示方面的不足，开发设计了一种能够同时具有两种显示方式的动态刻度显示数字压力表。它不仅能够和一般数字压力表一样采用数码管显示压力值，而且可以用LED灯串模拟圆盘式机械压力表指针指示即时压力值，用常亮LED灯直观地模拟显示设定测量信号的上限值、下限值。
Liao, Fuyuan; Jan, Yih-Kuen
2012-06-01
This paper presents a recurrence network approach for the analysis of skin blood flow dynamics in response to loading pressure. Recurrence is a fundamental property of many dynamical systems, which can be explored in phase spaces constructed from observational time series. A visualization tool of recurrence analysis called recurrence plot (RP) has been proved to be highly effective to detect transitions in the dynamics of the system. However, it was found that delay embedding can produce spurious structures in RPs. Network-based concepts have been applied for the analysis of nonlinear time series recently. We demonstrate that time series with different types of dynamics exhibit distinct global clustering coefficients and distributions of local clustering coefficients and that the global clustering coefficient is robust to the embedding parameters. We applied the approach to study skin blood flow oscillations (BFO) response to loading pressure. The results showed that global clustering coefficients of BFO significantly decreased in response to loading pressure (precurrence network approach can practically quantify the nonlinear dynamics of BFO.
Liu, Nigang; Su, Zhenpeng; Gao, Zhonglei; Zheng, Huinan; Wang, Yuming; Wang, Shui; Spence, H. E.; Reeves, G. D.; Baker, D. N.; Blake, J. B.; Funsten, H. O.; Wygant, J. R.
2017-01-01
Magnetospheric whistler mode waves are of great importance in the radiation belt electron dynamics. Here on the basis of the analysis of a rare event with the simultaneous disappearances of whistler mode plasmaspheric hiss, exohiss, and chorus triggered by a sudden decrease in the solar wind dynamic pressure, we provide evidences for the following physical scenarios: (1) nonlinear generation of chorus controlled by the geomagnetic field inhomogeneity, (2) origination of plasmaspheric hiss from chorus, and (3) leakage of plasmaspheric hiss into exohiss. Following the reduction of the solar wind dynamic pressure, the dayside geomagnetic field configuration with the enhanced inhomogeneity became unfavorable for the generation of chorus, and the quenching of chorus directly caused the disappearances of plasmaspheric hiss and then exohiss.
Gas Kinematics on GMC scales in M51 with PAWS: cloud stabilization through dynamical pressure
Meidt, Sharon E; Garcia-Burillo, Santiago; Hughes, Annie; Colombo, Dario; Pety, Jerome; Dobbs, Clare L; Schuster, Karl F; Kramer, Carsten; Leroy, Adam K; Dumas, Gaelle; Thompson, Todd A
2013-01-01
We use the high spatial and spectral resolution of the PAWS CO(1-0) survey of the inner 9 kpc of the iconic spiral galaxy M51 to examine the effect of gas streaming motions on the star-forming properties of individual GMCs. We compare our view of gas flows in M51 -- which arise due to departures from axi-symmetry in the gravitational potential (i.e. the nuclear bar and spiral arms) -- with the global pattern of star formation as traced by Halpha and 24\\mu m emission. We find that the dynamical environment of GMCs strongly affects their ability to form stars, in the sense that GMCs situated in regions with large streaming motions can be stabilized, while similarly massive GMCs in regions without streaming go on to efficiently form stars. We argue that this is the result of reduced surface pressure felt by clouds embedded in an ambient medium undergoing large streaming motions, which prevents collapse. Indeed, the variation in gas depletion time expected based on the observed streaming motions throughout the di...
Shen, X. C.; Shi, Q. Q.; Zong, Q.-G.; Tian, A. M.; Nowada, M.; Sun, W. J.; Zhao, H. Y.; Hudson, M. K.; Wang, H. Z.; Fu, S. Y.; Pu, Z. Y.
2017-02-01
Ultralow frequency (ULF) waves play an important role in the transport of the solar wind energy to the magnetosphere. In this paper, we present a ULF wave event in the dayside magnetosphere which shows a sudden decrease in frequency from 3.1 to 2.3 mHz around 0756 UT on 11 January 2010, when a solar wind dynamic pressure drop (from ˜5 to ˜2 nPa) was observed simultaneously. The wave exits globally. The phase differences between electric and magnetic fields indicate that the compressional mode wave is standing before and after the wave frequency decrease. This result suggests that the ULF wave should be associated with a cavity mode and the frequency decrease might be induced by the change of the cavity size. A theoretical calculation was made to estimate the cavity mode frequency. The calculated wave frequency before/after the negative impulse is 3.8/2.6 mHz, which is consistent with the observations.
Berg, Ronan M G; Plovsing, Ronni R; Bailey, Damian M
2016-01-01
(Pvolunteers at baseline; Pvolunteers after LPS). The corresponding RoR values increased from 0·46 (0·31-0·49) s(-1) at baseline to 0·58 (0·36-0·74) s(-1) after LPS (Pvolunteers, whereas they were similar to values observed in patients [0·43 (0·36-0·52) s...... shock. In this study, we hypothesized that this pattern of response would be identical during induced changes in blood pressure. Dynamic cerebral autoregulation was assessed in nine healthy volunteers and six septic patients. The healthy volunteers underwent a 4-h intravenous infusion of LPS (total dose......R). This was performed before and after LPS infusion in healthy volunteers, and within 72 h following clinical diagnosis of sepsis in patients. In healthy volunteers, thigh-cuff deflation caused a MAP reduction of 16 (13-20) % at baseline and 18 (16-20) % after LPS, while the MAP reduction was 12 (11-13) % in patients...
T. R. Sun
2012-08-01
Full Text Available We performed global MHD simulations of the geosynchronous magnetic field in response to fast solar wind dynamic pressure (P_{d} enhancements. Taking three P_{d} enhancement events in 2000 as examples, we found that the main features of the total field B and the dominant component B_{z} can be efficiently predicted by the MHD model. The predicted B and B_{z} varies with local time, with the highest level near noon and a slightly lower level around mid-night. However, it is more challenging to accurately predict the responses of the smaller component at the geosynchronous orbit (i.e., B_{x} and B_{y}. In contrast, the limitations of T01 model in predicting responses to fast P_{d} enhancements are presented.
Array of surface-confined glow discharges in atmospheric pressure helium: Modes and dynamics
Li, D.; Liu, D. X., E-mail: liudingxin@gmail.com, E-mail: mglin5g@gmail.com [Center for Plasma Biomedicine, State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Shaanxi (China); Nie, Q. Y.; Li, H. P. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Chen, H. L. [Frank Reidy Center for Bioelectrics, Old Dominion University, Norfolk, Virginia 23508 (United States); Kong, M. G., E-mail: liudingxin@gmail.com, E-mail: mglin5g@gmail.com [Center for Plasma Biomedicine, State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Shaanxi (China); Frank Reidy Center for Bioelectrics, Old Dominion University, Norfolk, Virginia 23508 (United States); Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States)
2014-05-19
Array of atmospheric pressure surface discharges confined by a two-dimensional hexagon electrode mesh is studied for its discharge modes and temporal evolution so as to a theoretical underpinning to their growing applications in medicine, aerodynamic control, and environmental remediation. Helium plasma surface-confined by one hexagon-shaped rim electrode is shown to evolve from a Townsend mode to a normal and abnormal glow mode, and its evolution develops from the rim electrodes as six individual microdischarges merging in the middle of the hexagon mesh element. Within one hexagon element, microdischarges remain largely static with the mesh electrode being the instantaneous cathode, but move towards the hexagon center when the electrode is the instantaneous anode. On the entire array electrode surface, plasma ignition is found to beat an unspecific hexagon element and then spreads to ignite surrounding hexagon elements. The spreading of microdischarges is in the form of an expanding circle at a speed of about 3 × 10{sup 4} m/s, and their quenching starts in the location of the initial plasma ignition. Plasma modes influence how input electrical power is used to generate and accelerate electrons and as such the reaction chemistry, whereas plasma dynamics are central to understand and control plasma instabilities. The present study provides an important aspect of plasma physics of the atmospheric surface-confined discharge array and a theoretical underpinning to its future technological innovation.
Pressure and temperature dependence of the laser-induced plasma plume dynamics
Ojeda-G-P, Alejandro; Schneider, Christof W.; Lippert, Thomas; Wokaun, Alexander
2016-12-01
The influence of different background gases and substrate heating on the plasma plume dynamics from silver ablation is investigated by species selected time and space resolved imaging. The results provide a time-resolved understanding on how those process parameters affect the expansion: from a free expansion in vacuum with velocities exceeding 20 000 m/s to a very slow expansion in Ar at 1 × 10-1 mbar with arrival velocities of 280 m/s. In addition, we observe a rebound of the ablated material on the substrate holder leading to a re-coating of the ablated target. At 1 × 10-1 mbar, it seems that the expansion of the plasma plume displaces a considerable portion of the background gas and traps it against the frontal area of the substrate holder. This leads to a transient high local pressure just above the substrate. In the case of Ar, the rebound is enhanced due to inelastic scattering, whereas for an O2 background, an area of high reactivity/emission in addition to the rebound is created. Imaging of selected species shows that the light emission in this area is mainly due to excited Ag and metal oxygen species. There is a clear influence of substrate heating on the plasma expansion due to the background gas density gradients, reducing the stopping ability of the background gas and already detectable 2 cm away from the substrate. Both rebound and excitation effects are reduced in intensity due to the substrate heating.
A dynamical point of view of Quantum Information: entropy and pressure
Baraviera, A; Lopes, A O; Cunha, M Terra
2011-01-01
Quantum Information is a new area of research which has been growing rapidly since last decade. This topic is very close to potential applications to the so called Quantum Computer. In our point of view it makes sense to develop a more "dynamical point of view" of this theory. We want to consider the concepts of entropy and pressure for "stationary systems" acting on density matrices which generalize the usual ones in Ergodic Theory (in the sense of the Thermodynamic Formalism of R. Bowen, Y. Sinai and D. Ruelle). We consider the operator $\\mathcal{L}$ acting on density matrices $\\rho\\in \\mathcal{M}_N$ over a finite $N$-dimensional complex Hilbert space $\\mathcal{L}(\\rho):=\\sum_{i=1}^k tr(W_i\\rho W_i^*)V_i\\rho V_i^*,$ where $W_i$ and $V_i$, $i=1,2,...k$ are operators in this Hilbert space. $\\mathcal{L}$ is not a linear operator. In some sense this operator is a version of an Iterated Function System (IFS). Namely, the $V_i\\,(.)\\,V_i^*=:F_i(.)$, $i=1,2,...,k$, play the role of the inverse branches (acting on t...
Yao Qiangling
2015-01-01
Full Text Available The borehole stress-meter was employed in this study to investigate the distribution of the side abutment stress in roadway subjected to dynamic pressure. The results demonstrate that the side abutment stress of the mining roadway reaches a peak value when the distance to the gob is 8 m and the distribution curve of the side abutment stress can be divided into three zones: stress rising zone, stress stabilizing zone, and stress decreasing zone. Further numerical investigation was carried out to study the effect of the coal mass strength, coal seam depth, immediate roof strength, and thickness on the distribution of the side abutment stress. Based on the research results, we determined the reasonable position of the mining roadway and the optimal width of the barrier pillar. The engineering application demonstrates that the retention of the barrier pillar with a width of 5 m along the gob as the haulage roadway for the next panel is feasible, which delivers favorable technological and economic benefits.
S. Saha
2016-04-01
Full Text Available Combustion instability in solid propellant rocket motor is numerically simulated by implementing propellant response function with quasi steady homogeneous one dimensional formulation. The convolution integral of propellant response with pressure history is implemented through a user defined function in commercial computational fluid dynamics software. The methodology is validated against literature reported motor test and other simulation results. Computed amplitude of pressure fluctuations compare closely with the literarture data. The growth rate of pressure oscillations of a cylindrical grain solid rocket motor is determined for different response functions at the fundamental longitudinal frequency. It is observed that for response function more than a critical value, the motor exhibits exponential growth rate of pressure oscillations.
Maximum Autocorrelation Factorial Kriging
Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.
2000-01-01
This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from...
Osaka, Noboru; Shibayama, Mitsuhiro; Kikuchi, Tatsuya; Yamamuro, Osamu
2009-10-01
Dynamics of water and poly(N-isopropylacrylamide) (PNIPA) in concentrated aqueous solutions, where the majority of water molecules are attached to polymer chains, has been investigated with use of incoherent quasi-elastic neutron scattering (QENS) and dynamic light scattering (DLS) measurements as functions of temperature, T, and hydrostatic pressure, P. It was observed by QENS that the self-diffusion coefficient, D(water), of water in PNIPA/H(2)O solutions increased by P at temperatures below the lower critical solution temperature (LCST) of PNIPA aqueous solutions. However, above the LCST, D(water) decreased by P, as is often reported in non-hydrogen bonding solutions. In isobaric heating runs, therefore, the jump in D(water) at LCST decreased with increasing pressure. On the other hand, the mean-square displacement, , of the local vibrational motion of PNIPA in PNIPA/D(2)O solutions, where the incoherent scattering signal of PNIPA was predominantly observed, was reduced due to the aggregation behavior of PNIPA by pressurizing, which was also confirmed by using DLS. The jump in at the LCST became gradual by pressurizing, which was consistent with the changes of the dynamics of water obtained in PNIPA/H(2)O solutions.
Ferroni, Marco; Giusti, Serena; Nascimento, Diana; Silva, Ana; Boschetti, Federica; Ahluwalia, Arti
2016-08-01
The architecture and dynamic physical environment of tissues can be recreated in-vitro by combining 3D porous scaffolds and bioreactors able to apply controlled mechanical stimuli on cells. In such systems, the entity of the stimuli and the distribution of nutrients within the engineered construct depend on the micro-structure of the scaffolds. In this work, we present a new approach for optimizing computational fluid-dynamics (CFD) models for the investigation of fluid-induced forces generated by cyclic squeeze pressure within a porous construct, coupled with oxygen consumption of cardiomyocytes. A 2D axial symmetric macro-scaled model of a squeeze pressure bioreactor chamber was used as starting point for generating time dependent pressure profiles. Subsequently the fluid movement generated by the pressure fields was coupled with a complete 3D micro-scaled model of a porous protein cryogel. Oxygen transport and consumption inside the scaffold was evaluated considering a homogeneous distribution of cardiomyocytes throughout the structure, as confirmed by preliminary cell culture experiments. The results show that a 3D description of the system, coupling a porous geometry and time dependent pressure driven flow with fluid-structure-interaction provides an accurate and meaningful description of the microenvironment in terms of shear stress and oxygen distribution than simple stationary 2D models.
Jinnai, Takahiro; Nagao, Seigo [Kagawa Medical Univ., Miki (Japan); Kuyama, Hideyuki
2000-03-01
Normal pressure hydrocephalus (NPH) is one of the diseases that causes a neuro-surgically treatable form of dementia. Although patients with NPH can be treated with shunt operation, reliable indications for the surgery are not yet established. In this study, 20 NPH patients diagnosed by clinical symptoms were subjected to combined assessment by infusion test and dynamic CT scan, a useful diagnostic tool to select a shunt responsive cases. Patients were evaluated by measuring sequential changes in the density of the periventricular lucency (PVL) using dynamic CT scan and continuous lumbar subdural pressure monitoring during an infusion manometric test at a rate of 0.8 ml/min for 30 min. The average lumbar subdural pressure during infusion manometric test in the shunt responsive group was 18.4{+-}5.8 mmHg, which was significantly higher than that in the shunt non-responsive group which was 10.0{+-}4.0 mmHg (p<0.01). The relative changes in PVL density in the dynamic CT was also significantly higher in the shunt responsive group (0.99{+-}0.61 HU) compared to the shunt non-responsive group (0.15{+-}0.32) (p<0.01). Dynamic CT scan with infusion manometric test is useful in the selection of patients with NPH who are likely to respond to shunt surgery. (author)
Li, Xiying; Mao, Liqun; Ma, Xuehu
2013-01-29
Textured silicon surfaces decorated by square arrays of pillars with adjustable pitch were fabricated. The wetting behavior, especially for direction-dependent water contact angles on textured silicon surfaces after silanization, was investigated by incorporating the contact line fraction into a modified Wenzel model. Also, the effect of geometrical parameters on the anisotropic wetting behavior of water was examined with respect to water droplet impact on the textured surface. Moreover, the maximum spreading factor was studied theoretically in terms of energy conservation, allowing for surface topography and viscous friction of the liquid flowing among the arrays of the posts. Theoretical models were found to be in good agreement with experimental data.
2016-01-01
Abstract Normal pulmonary artery pressure and pulmonary hypertension assessment of newborns is rarely reported. The aim of the study is to explore dynamic changes of pulmonary arterial pressure and ductus arteriosus in human newborns from birth to 72 h of age with echocardiography. A total of 76 cases of normal newborns were prospectively detected by echocardiography after birth of 2 h, 6 h, 12 h, 24 h, 48 h, and 72 h, respectively. Ductus arteriosus diameter, blood shunt direction, blood flo...
Dave, Jaydev K; Halldorsdottir, Valgerdur G; Eisenbrey, John R; Liu, Ji-Bin; McDonald, Maureen E; Dickie, Kris; Leung, Corina; Forsberg, Flemming
2011-10-01
The purpose of this study was to develop and validate a noninvasive pressure estimation technique based on subharmonic emissions from a commercially available ultrasound contrast agent and scanner, unlike other studies that have either adopted a single-element transducer approach and/ or use of in-house contrast agents. Ambient pressures were varied in a closed-loop flow system between 0 and 120 mmHg and were recorded by a solid-state pressure catheter as the reference standard. Simultaneously, the ultrasound scanner was operated in pulse inversion mode transmitting at 2.5 MHz, and the unprocessed RF data were captured at different incident acoustic pressures (from 76 to 897 kPa). The subharmonic data for each pulse were extracted using band-pass filtering with averaging, and subsequently processed to eliminate noise. The incident acoustic pressure most sensitive to ambient pressure fluctuations was determined, and then the ambient pressure was tracked over 20 s. In vivo validation of this technique was performed in the left ventricle (LV) of 2 canines. In vitro, the subharmonic signal could track ambient pressure values with r(2) = 0.922 (p subharmonic signal tracked the LV pressures with r(2) > 0.790 (p subharmonic ultrasound-based pressure estimation technique, which can accurately track left ventricular pressures, has been established.
Parviz Ghadimi
2013-01-01
Full Text Available A mathematical model is utilized in order to calculate three-dimensional pressure distributions on planing hulls. This type of modeling is able to determine the hydrodynamic and hydrostatic pressures acting on the bottom of these hulls. As a result, the total 3-dimensional pressure exerted on the planing hull as a sum of hydrostatic and hydrodynamic pressures can be evaluated. Empirical equations introduced in previous works have been used as the fundamentals for the present mathematical modeling method. The obtained results are compared against available experimental results and results of empirical equations in order to validate the proposed method. The outcome of the -squared tests conducted on these comparisons shows favorable accuracy of the results. After evaluation of hydrodynamic pressure, the effects of trim and deadrise angles and wetted length on the 3-dimensional pressure distribution are analyzed. Finally, the total pressure on planing hull and the effect of velocity coefficients are studied.
Herkenhoff F.L.
2001-01-01
Full Text Available Borderline hypertension (BH has been associated with an exaggerated blood pressure (BP response during laboratory stressors. However, the incidence of target organ damage in this condition and its relation to BP hyperreactivity is an unsettled issue. Thus, we assessed the Doppler echocardiographic profile of a group of BH men (N = 36 according to office BP measurements with exaggerated BP in the cycloergometric test. A group of normotensive men (NT, N = 36 with a normal BP response during the cycloergometric test was used as control. To assess vascular function and reactivity, all subjects were submitted to the cold pressor test. Before Doppler echocardiography, the BP profile of all subjects was evaluated by 24-h ambulatory BP monitoring. All subjects from the NT group presented normal monitored levels of BP. In contrast, 19 subjects from the original BH group presented normal monitored BP levels and 17 presented elevated monitored BP levels. In the NT group all Doppler echocardiographic indexes were normal. All subjects from the original BH group presented normal left ventricular mass and geometrical pattern. However, in the subjects with elevated monitored BP levels, fractional shortening was greater, isovolumetric relaxation time longer, and early to late flow velocity ratio was reduced in relation to subjects from the original BH group with normal monitored BP levels (P<0.05. These subjects also presented an exaggerated BP response during the cold pressor test. These results support the notion of an integrated pattern of cardiac and vascular adaptation during the development of hypertension.
Semi-supervised detection of intracranial pressure alarms using waveform dynamics.
Scalzo, Fabien; Hu, Xiao
2013-04-01
Patient monitoring systems in intensive care units (ICU) are usually set to trigger alarms when abnormal values are detected. Alarms are generated by threshold-crossing rules that lead to high false alarm rates. This is a recognized issue that causes alarm fatigue, waste of human resources, and increased patient risks. Recently developed smart alarm models require alarms to be validated by experts during the training phase. The manual annotation process involved is time-consuming and virtually impossible to achieve for the thousands of alarms recorded in the ICU every week. To tackle this problem, we investigate in this study if the use of semi-supervised learning methods, that can naturally integrate unlabeled data samples in the model, can be used to improve the accuracy of the alarm detection. As a proof of concept, the detection system is evaluated on intracranial pressure (ICP) signal alarms. Specific morphological and trending features are extracted from the ICP signal waveform to capture the dynamic of the signal prior to alarms. This study is based on a comprehensive dataset of 4791 manually labeled alarms recorded from 108 neurosurgical patients. A comparative analysis is provided between kernel spectral regression (SR-KDA) and support vector machine (SVM) both modified for the semi-supervised setting. Results obtained during the experimental evaluations indicate that the two models can significantly reduce false alarms using unlabeled samples; especially in the presence of a restrained number of labeled examples. At a true alarm recognition rate of 99%, the false alarm reduction rates improved from 9% (supervised) to 27% (semi-supervised) for SR-KDA, and from 3% (supervised) to 16% (semi-supervised) for SVM.
Ning, Wenjun; Wang, Lijun; Wu, Chen; Jia, Shenli
2014-08-01
Effects of voltage magnitude on the development of a stable helium atmospheric pressure plasma jet are investigated by current measurements and high temporal-resolution streak images. Generated by a coaxial dielectric barrier discharge structure, the entire discharge can be classified into three regions: discharges in the tube gap, downstream jet, and up-streamer. The discharge morphologies of each region are analyzed. In the positive discharge phase, there are two discharges in the tube gap between the electrodes; the first one is ignited as corona and then developed into streamer corona, and the second one is similar with positive glow. The downstream jet is ignited independently from the discharge in the tube gap. Referred as "plasma bullet," the dynamic behavior of the jet can be well described as a positive streamer. Under specific applied voltage, the jet is found to be composed by double bullets in which case the jet length decreases since that less charge is carried by the first bullet. The up-streamer can be captured as long as the discharge in the tube gap is activated. Propagating with velocity of ˜4 km/s, the up-streamer can be regarded as the extension of the first discharge in the tube gap. In the negative discharge phase, the discharge is confined in the tube gap with nearly symmetrical morphology with the positive one. Besides, with the rising of voltage, the negative discharge is initially intensified and then turns weaker after surpassing certain voltage, which may provide suitable condition for the occurrence of double-bullet phenomenon.
Pittoni, Paola G.; Lin, Ya-Chi; Lin, Shi-Yow
2014-05-01
Droplet impingement experiments at low Weber numbers were conducted by digitizing silhouettes of impacting water drops onto unlike graphite substrates, typified by different advancing water contact angles (θa): 140 and 160°. The relaxation of wetting diameter, dynamic contact angle, and drop shapes were measured. The purpose was to carefully investigate the phenomenology and possible causes of the failure of the superhydrophobicity. During impact and spreading phases, all the drops impinging onto both graphite substrates showed a similar behavior. Then, after an initial free recoil, drops impinging at lower impact velocities onto graphite substrates characterized by θa = 140° clearly exhibited time intervals in which the wetting diameter appeared to be almost constant. The duration of this pinned phase was observed decreasing with increasing the impact height and almost completely disappearing for drops impinging at higher impact velocities. This behavior has never been reported before, and, contrariwise, water droplets impinging at lower impact velocities onto hydrophobic and superhydrophobic surfaces have been generally observed more freely retracting, and ultimately rebounding, compared to drops impacting at higher velocities. In the present study, this latter behavior was recorded just for drops impinging onto graphite surfaces characterized by θa = 160°. A theoretical description of the experimental results was proposed, specifically investigating the role of dynamic pressure, hammer pressure and liquid penetration time during the impact, spreading and recoil stages.
Turgman-Cohen, Salomon
2013-10-08
We consider an atomistic model to investigate the flux of water through thin Linde type A (LTA) zeolite membranes with differing surface chemistries. Using molecular dynamics, we have studied the flow of water under hydrostatic pressure through a fully hydrated LTA zeolite film (∼2.5 nm thick) capped with hydrophilic and hydrophobic moieties. Pressure drops in the 50-400 MPa range were applied across the membrane, and the flux of water was monitored for at least 15 ns of simulation time. For hydrophilic membranes, water molecules adsorb at the zeolite surface, creating a highly structured fluid layer. For hydrophobic membranes, a depletion of water molecules occurs near the water/zeolite interface. For both types of membranes, the water structure is independent of the pressure drop established in the system and the flux through the membranes is lower than that observed for the bulk zeolitic material; the latter allows an estimation of surface barrier effects to pressure-driven water transport. Mechanistically, it is observed that (i) bottlenecks form at the windows of the zeolite structure, preventing the free flow of water through the porous membrane, (ii) water molecules do not move through a cage in a single-file fashion but rather exhibit a broad range of residence times and pronounced mixing, and (iii) a periodic buildup of a pressure difference between inlet and outlet cages takes place which leads to the preferential flow of water molecules toward the low-pressure cages. © 2013 American Chemical Society.
Burke, Ariane; Kageyama, Masa; Latombe, Guilllaume; Fasel, Marc; Vrac, Mathieu; Ramstein, Gilles; James, Patrick M. A.
2017-05-01
The extent to which climate change has affected the course of human evolution is an enduring question. The ability to maintain spatially extensive social networks and a fluid social structure allows human foragers to ;map onto; the landscape, mitigating the impact of ecological risk and conferring resilience. But what are the limits of resilience and to which environmental variables are foraging populations sensitive? We address this question by testing the impact of a suite of environmental variables, including climate variability, on the distribution of human populations in Western Europe during the Last Glacial Maximum (LGM). Climate variability affects the distribution of plant and animal resources unpredictably, creating an element of risk for foragers for whom mobility comes at a cost. We produce a model of habitat suitability that allows us to generate predictions about the probable distribution of human populations and discuss the implications of these predictions for the structure of human populations and their social and cultural evolution during the LGM.
Liu, Zhe; Lin, Lei; Xie, Lian; Gao, Huiwang
2016-10-01
To improve the efficiency of the terrain-following σ-coordinate non-hydrostatic ocean model, a partially implicit finite difference (PIFD) scheme is proposed. By using explicit terms instead of implicit terms to discretize the parts of the vertical dynamic pressure gradient derived from the σ-coordinate transformation, the coefficient matrix of the discrete Poisson equation that the dynamic pressure satisfies can be simplified from 15 diagonals to 7 diagonals. The PIFD scheme is shown to run stably when it is applied to simulate five benchmark cases, namely, a standing wave in a basin, a surface solitary wave, a lock-exchange problem, a periodic wave over a bar and a tidally induced internal wave. Compared with the conventional fully implicit finite difference (FIFD) scheme, the PIFD scheme produces simulation results of equivalent accuracy at only 40-60% of the computational cost. The PIFD scheme demonstrates strong applicability and can be easily implemented in σ-coordinate ocean models.
Johansen, Per; Rømer, Daniel; Andersen, Torben Ole
2014-01-01
is a multibody dynamics model of a radial piston fluid power motor, which connects the rigid bodies through models of the transient hydrodynamic lubrication pressure in the joint clearance. A finite volume approach is used to model the pressure dynamics of the fluid film lubrication. The model structure......The increasing interest in hydraulic transmissions in wind and wave energy applications has created an incentive for the development of high efficiency fluid power machinery. Modeling and analysis of fluid power machinery loss mechanisms are necessary in order to accommodate this demand. At present...... fully coupled thermo-elastic models has been used to simulate and study loss mechanisms in various tribological interfaces. Consequently, a reasonable focus of further development is to couple the interface models and the rigid body mechanics of fluid power machinery. The focus of the current paper...
Kishimoto, Miori, E-mail: miori@mx6.et.tiki.ne.jp [Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-11 Inada-cho, Obihiro 080-8555 (Japan); Tsuji, Yoshihisa, E-mail: y.tsuji@extra.ocn.ne.jp [Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Shogoinkawara-cho 54, Sakyo-ku 606-8507 (Japan); Katabami, Nana; Shimizu, Junichiro; Lee, Ki-Ja [Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-11 Inada-cho, Obihiro 080-8555 (Japan); Iwasaki, Toshiroh [Department of Veterinary Internal Medicine, Tokyo University of Agriculture and Technology, Saiwai-cho, 3-5-8, Fuchu 183-8509 (Japan); Miyake, Yoh-Ichi [Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-11 Inada-cho, Obihiro 080-8555 (Japan); Yazumi, Shujiro [Digestive Disease Center, Kitano Hospital, 2-4-20 Ougi-machi, Kita-ku, Osaka 530-8480 (Japan); Chiba, Tsutomu [Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Shogoinkawara-cho 54, Sakyo-ku 606-8507 (Japan); Yamada, Kazutaka, E-mail: kyamada@obihiro.ac.jp [Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-11 Inada-cho, Obihiro 080-8555 (Japan)
2011-01-15
Objective: We investigated whether the prerequisite of the maximum slope and deconvolution methods are satisfied in pancreatic perfusion CT and whether the measured parameters between these algorithms are correlated. Methods: We examined nine beagles injected with iohexol (200 mgI kg{sup -1}) at 5.0 ml s{sup -1}. The abdominal aorta and splenic and celiac arteries were selected as the input arteries and the splenic vein, the output veins. For the maximum slope method, we determined the arterial contrast volume of each artery by measuring the area under the curve (AUC) and compared the peak enhancement time in the pancreas with the contrast appearance time in the splenic vein. For the deconvolution method, the artery-to-vein collection rate of contrast medium was calculated. We calculated the pancreatic tissue blood flow (TBF), tissue blood volume (TBV), and mean transit time (MTT) using both algorithms and investigated their correlation based on vessel selection. Results: The artery AUC significantly decreased as it neared the pancreas (P < 0.01). In all cases, the peak time of the pancreas (11.5 {+-} 1.6) was shorter than the appearance time (14.1 {+-} 1.6) in the splenic vein. The splenic artery-vein combination exhibited the highest collection rate (91.1%) and was the only combination that was significantly correlated between TBF, TBV, and MTT in both algorithms. Conclusion: Selection of a vessel nearest to the pancreas is considered as a more appropriate prerequisite. Therefore, vessel selection is important in comparison of the semi-quantitative parameters obtained by different algorithms.
Gardner, J. E.; Andrews, B. J.
2016-12-01
Pyroclastic density currents (flows and surges) are one of the most deadly hazards associated with volcanic eruptions. Understanding what controls how far such currents will travel, and how their dynamic pressure evolves, could help mitigate their hazards. The distance a ground hugging, pyroclastic density current travels is partly limited by when it reverses buoyancy and lifts off into the atmosphere. The 1980 blast surge of Mount St. Helens offers an example of a current seen to lift off. Before lofting, it had traveled up to 20 km and leveled more than 600 km3 of thick forest (the blowdown zone). The outer edge of the devastated area - where burned trees that were left standing (the singe zone) - is where the surge is thought to have lifted off. We recently examined deposits in the outer parts of the blowdown and in the singe zone at 32 sites. The important finding is that the laterally moving surge travelled into the singe zone, and hence the change in tree damage does not mark the run out distance of the ground hugging surge. Eyewitness accounts and impacts on trees and vehicles reveal that the surge consisted of a fast, dilute "overcurrent" and a slower "undercurrent", where most of the mass (and heat) was retained. Reasonable estimates for flow density and velocity show that dynamic pressure of the surge (i.e., its ability to topple trees) peaked near the base of the overcurrent. We propose that when the overcurrent began to lift off, the height of peak dynamic pressure rose above the trees and stopped toppling them. The slower undercurrent continued forward, burning trees but it lacked the dynamic pressure needed to topple them. Grain-size variations argue that it slowed from 30 m/s when it entered the singe zone to 3 m/s at the far end. Buoyancy reversal and liftoff are thus not preserved in the deposits where the surge lofted upwards.
Svahn, Ola; Björklund, Erland
2015-01-01
Thermal degradation of antibiotics has been studied for decades in a broad range of disciplines including food production, agriculture and analytical chemistry. Yet, there is a lack of thermal stability data for many antibiotics. Here we systematically investigated the thermal stability of ten commonly prescribed antibiotics applying a laborsaving automated inhouse pressurized dynamic flow-through system. The design of the system allowed a fast access to a large number of data at medium to su...
Wang, Qin; Xie, Hui; Chen, Yongshi; Liu, Chao
2017-04-01
The nucleation and growth of silver nanoparticles in the supersaturated system are investigated by molecular dynamics simulation at different temperatures and pressures. The variety of the atoms in the biggest cluster and the size of average clusters in the system versus the time are estimated to reveal the relationship between the nucleation as well as cluster growth. The nucleation rates in different situations are calculated with the threshold method. The effect of temperature and pressure on the nucleation rate is identified as obeying a linear function. Finally, the development of basal elements, such as monomers, dimers and trimmers, is revealed how the temperature and pressure affect the nucleation and growth of the silver cluster.
Wohlert, Jakob
2014-05-22
In this paper, we report the calculation of the enthalpy of sublimation, Δ(sub)H, as a function of temperature of crystalline β-cellobiose from molecular dynamics (MD) simulations, using two popular carbohydrate force fields. Together with the entropy difference between the solid and the vapor, ΔS, evaluated at atmospheric pressure, Δ(sub)H gives the vapor pressure of cellobiose over the solid phase as a function of T. It is found that when quantum mechanical corrections to the enthalpy calculated from the distribution of normal modes is applied both force fields give Δ(sub)H close to experiments. The entropy change, ΔS, which is calculated within a harmonic approximation becomes too small, leading to vapor pressures that are too low. These findings are relevant to MD simulations of crystalline carbohydrates in general, e.g., native cellulose.
Frank, Jonathan H. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Reacting Flows Dept.; Pickett, Lyle M. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Engine Combustion Dept.; Bisson, Scott E. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Remote Sensing and Energetic Materials Dept.; Patterson, Brian D. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). combustion Chemistry Dept.; Ruggles, Adam J. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Reacting Flows Dept.; Skeen, Scott A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Engine Combustion Dept.; Manin, Julien Luc [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Engine Combustion Dept.; Huang, Erxiong [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Reacting Flows Dept.; Cicone, Dave J. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Engine Combustion Dept.; Sphicas, Panos [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Engine Combustion Dept.
2015-09-01
In this LDRD project, we developed a capability for quantitative high - speed imaging measurements of high - pressure fuel injection dynamics to advance understanding of turbulent mixing in transcritical flows, ignition, and flame stabilization mechanisms, and to provide e ssential validation data for developing predictive tools for engine combustion simulations. Advanced, fuel - efficient engine technologies rely on fuel injection into a high - pressure, high - temperature environment for mixture preparation and com bustion. Howe ver, the dynamics of fuel injection are not well understood and pose significant experimental and modeling challenges. To address the need for quantitative high - speed measurements, we developed a Nd:YAG laser that provides a 5ms burst of pulses at 100 kHz o n a robust mobile platform . Using this laser, we demonstrated s patially and temporally resolved Rayleigh scattering imaging and particle image velocimetry measurements of turbulent mixing in high - pressure gas - phase flows and vaporizing sprays . Quantitativ e interpretation of high - pressure measurements was advanced by reducing and correcting interferences and imaging artifacts.
A. M. Makarieva
2010-10-01
Full Text Available Phase transitions of atmospheric water play a ubiquitous role in the Earth's climate system, but their direct impact on atmospheric dynamics has escaped wide attention. Here we examine and advance a theory as to how condensation influences atmospheric pressure through the mass removal of water from the gas phase with a simultaneous account of the latent heat release. Building from fundamental physical principles we show that condensation is associated with a decline in air pressure in the lower atmosphere. This decline occurs up to a certain height, which ranges from 3 to 4 km for surface temperatures from 10 to 30 °C. We then estimate the horizontal pressure differences associated with water vapor condensation and find that these are comparable in magnitude with the pressure differences driving observed circulation patterns. The water vapor delivered to the atmosphere via evaporation represents a store of potential energy available to accelerate air and thus drive winds. Our estimates suggest that the global mean power at which this potential energy is released by condensation is around one per cent of the global solar power – this is similar to the known stationary dissipative power of general atmospheric circulation. We conclude that condensation and evaporation merit attention as major, if previously overlooked, factors in driving atmospheric dynamics.
Ekrami, Yasamin; Cook, Joseph S.
2011-01-01
In order to mitigate catastrophic failures on future generation space vehicles, engineers at the National Aeronautics and Space Administration have begun to integrate a novel crew abort systems that could pull a crew module away in case of an emergency at the launch pad or during ascent. The Max Launch Abort System (MLAS) is a recent test vehicle that was designed as an alternative to the baseline Orion Launch Abort System (LAS) to demonstrate the performance of a "tower-less" LAS configuration under abort conditions. The MLAS II test vehicle will execute a propulsive coast stabilization maneuver during abort to control the vehicles trajectory and thrust. To accomplish this, the spacecraft will integrate an Attitude Control System (ACS) with eight hypergolic monomethyl hydrazine liquid propulsion engines that are capable of operating in a quick pulsing mode. Two main elements of the ACS include a propellant distribution subsystem and a pressurization subsystem to regulate the flow of pressurized gas to the propellant tanks and the engines. The CAD assembly of the Attitude Control System (ACS) was configured and integrated into the Launch Abort Vehicle (LAV) design. A dynamic random vibration analysis was conducted on the Main Propulsion System (MPS) helium pressurization panels to assess the response of the panel and its components under increased gravitational acceleration loads during flight. The results indicated that the panels fundamental and natural frequencies were farther from the maximum Acceleration Spectral Density (ASD) vibrations which were in the range of 150-300 Hz. These values will direct how the components will be packaged in the vehicle to reduce the effects high gravitational loads.
Grus Franz-H
2004-03-01
Full Text Available Abstract Background The new Ocular Dynamic Contour Tonometer (DCT, investigational device supplied by SMT (Swiss Microtechnology AG, Switzerland allows simultaneous recording of intraocular pressure (IOP and ocular pulse amplitude (OPA. It was the aim of this study to compare the IOP results of this new device with Goldmann tonometry. Furthermore, IOP and OPA measured with the new slitlamp-mounted DCT were compared to the IOP and OPA measured with the hand-held SmartLens®, a gonioscopic contact lens tonometer (ODC Ophthalmic Development Company AG, Switzerland. Methods Nineteen healthy subjects were included in this study. IOP was determined by three consecutive measurements with each of the DCT, SmartLens®, and Goldmann tonometer. Furthermore, OPA was measured three times consecutively by DCT and SmartLens®. Results No difference (P = 0.09 was found between the IOP values by means of DCT (mean: 16.6 mm Hg, median: 15.33 mm Hg, SD: +/- 4.04 mm Hg and Goldmann tonometry (mean: 16.17 mm Hg, median: 15.33 mm Hg, SD: +/- 4.03 mm Hg. The IOP values of SmartLens® (mean: 20.25 mm Hg, median: 19.00 mm Hg, SD: +/- 4.96 mm Hg were significantly higher (P = 0.0008 both from Goldmann tonometry and DCT. The OPA values of the DCT (mean: 3.08 mm Hg, SD: +/- 0.92 mm Hg were significantly lower (P = 0.0003 than those obtained by SmartLens® (mean: 3.92 mm Hg, SD: +/- 0.83 mm Hg. Conclusions DCT was equivalent to Goldmann applanation tonometry in measurement of IOP in a small group of normal subjects. In contrast, SmartLens® (contact lens tonometry gave IOP readings that were significantly higher compared with Goldmann applanation tonometer readings. Both devices, DCT and SmartLens® provide the measurement of OPA which could be helpful e.g. for the management of glaucoma.
2012-01-01
Background Acute pressure on the sciatic nerve has recently been reported to provide rapid short-term relief of pain in patients with various pathologies. Wide dynamic range (WDR) neurons transmit nociceptive information from the dorsal horn to higher brain centers. In the present study, we examined the effect of a 2-min application of sciatic nerve pressure on WDR neuronal activity in anesthetized male Sprague–Dawley rats. Results Experiments were carried out on 41 male Sprague–Dawley albino rats weighing 160–280 grams. Dorsal horn WDR neurons were identified on the basis of characteristic responses to mechanical stimuli applied to the cutaneous receptive field. Acute pressure was applied for 2 min to the sciatic nerve using a small vascular clip. The responses of WDR neurons to three mechanical stimuli applied to the cutaneous receptive field were recorded before, and 2, 5 and 20 min after cessation of the 2-min pressure application on the sciatic nerve. Two-min pressure applied to the sciatic nerve caused rapid attenuation of the WDR response to pinching, pressure and brushing stimuli applied to the cutaneous receptive field. Maximal attenuation of the WDR response to pinching and pressure was noted 5 min after release of the 2-min pressure on the sciatic nerve. The mean firing rate decreased from 31.7±1.7 Hz to 13±1.4 Hz upon pinching (p < 0.001), from 31.2±2.3 Hz to 10.9±1.4 Hz (p < 0.001) when pressure was applied, and from 18.9±1.2 Hz to 7.6±1.1 Hz (p < 0.001) upon brushing. Thereafter, the mean firing rates gradually recovered. Conclusions Our results indicate that acute pressure applied to the sciatic nerve exerts a rapid inhibitory effect on the WDR response to both noxious and innocuous stimuli. Our results may partially explain the rapid analgesic effect of acute sciatic nerve pressure noted in clinical studies, and also suggest a new model for the study of pain. PMID:23211003
Quantifying dynamic changes in plantar pressure gradient in diabetics with peripheral neuropathy
Chi-Wen Lung
2016-07-01
Full Text Available Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP and peak pressure gradient (PPG during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking, and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG and PGA were calculated for four foot regions - 1st toe (T1, 1st metatarsal head (M1, 2nd metatarsal head (M2, and heel (HL. Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared to non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P=0.02 and PPG was 214% (P<0.001 larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P=0.04, suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers.
Quantifying Dynamic Changes in Plantar Pressure Gradient in Diabetics with Peripheral Neuropathy
Lung, Chi-Wen; Hsiao-Wecksler, Elizabeth T.; Burns, Stephanie; Lin, Fang; Jan, Yih-Kuen
2016-01-01
Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP) and peak pressure gradient (PPG) during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA) has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG, and PGA were calculated for four foot regions – first toe (T1), first metatarsal head (M1), second metatarsal head (M2), and heel (HL). Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared with non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P = 0.02) and PPG was 214% (P < 0.001) larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P = 0.04), suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers. PMID:27486576
Dongkai Shen
2016-01-01
Full Text Available In recent studies on the dynamic characteristics of ventilation system, it was considered that human had only one lung, and the coupling effect of double lungs on the air flow can not be illustrated, which has been in regard to be vital to life support of patients. In this article, to illustrate coupling effect of double lungs on flow dynamics of mechanical ventilation system, a mathematical model of a mechanical ventilation system, which consists of double lungs and a bi-level positive airway pressure (BIPAP controlled ventilator, was proposed. To verify the mathematical model, a prototype of BIPAP system with a double-lung simulators and a BIPAP ventilator was set up for experimental study. Lastly, the study on the influences of key parameters of BIPAP system on dynamic characteristics was carried out. The study can be referred to in the development of research on BIPAP ventilation treatment and real respiratory diagnostics.
Stern, Jonathan; Zakamska, Nadia L; Hennawi, Joseph F
2015-01-01
Quasar feedback models often predict an expanding hot gas bubble which drives a galaxy-scale outflow. In many circumstances the hot gas is predicted to radiate inefficiently, making the hot bubble hard to observe directly. We present an indirect method to detect the presence of a hot bubble using hydrostatic photoionization models of the cold (10^4 K) line-emitting gas. These models assume that the cold gas is in pressure equilibrium with either the hot gas pressure or with the radiation pressure, whichever is larger. We compare our models with observations of the broad line region (BLR), the inner face of the dusty torus, the narrow line region (NLR), and the extended NLR, and thus constrain the hot gas pressure over a dynamical range of 10^5 in radius, from 0.1 pc to 10 kpc. We find that the emission line ratios observed in the average quasar spectrum are consistent with radiation-pressure-dominated models on all scales. On scales > L_AGN/c inferred for galaxy-scale outflows in luminous quasars. This appare...
QIONG WU; DONG XIANG; GUOLIN XIONG; WEIHUA ZHU; HEMING XIAO
2016-05-01
Ab initio molecular dynamics simulations were performed to study the initiation of decompositionand formation of first products of two molecular crystals pentaerythritol tetranitrate (PETN) and 5-nitro-2,4-dihydro-1,2,4-triazole-3-one (NTO) under thermal decomposition temperature (475 K for PETN and 531 Kfor NTO) coupled with different pressures (1-5 GPa). The pressure effects on the initial decomposition stepsand initially generated products on PETN and NTO were very different. PETN was triggered by C-H... O intermolecular hydrogen transfer. The initial decomposition mechanism was independent of the pressure. ForNTO, two different initial decomposition mechanisms were found. At 1, 2, and 3 GPa, it was triggered by NH....O intermolecular hydrogen transfer, while at 4 and 5 GPa, it was triggered by N-H.....N intermolecularhydrogen transfer. This indicates that the initial decomposition mechanism was dependent on the pressure.Our study may provide new insights into initial mechanisms and decomposition reactions of molecular crystalexplosives under thermal decomposition temperature coupled with different pressures with details at atomiclevel.
Zieher, Thomas; Markart, Gerhard; Ottowitz, David; Römer, Alexander; Rutzinger, Martin; Meißl, Gertraud; Geitner, Clemens
2017-01-01
Physically-based dynamic modelling of shallow landslide susceptibility rests on several assumptions and simplifications. However, the applicability of physically-based models is only rarely tested in the field at the appropriate scale. This paper presents results of a spray irrigation experiment conducted on a plot of 100 m2 on an Alpine slope susceptible to shallow landsliding. Infiltrating precipitation applied at a constant rate (27.5 mm/h for 5.3 h) was monitored by means of 2D time-lapse electrical resistivity tomography, combined with time-domain reflectometry sensors installed at various depths. In addition, regolith characteristics were assessed by dynamic cone penetration tests using a light-weight cone penetrometer. The spray irrigation experiment resulted in a vertically progressing wetting front to a depth of 80-100 cm. Below that, the unconsolidated material was already saturated by rainfall in the previous days. The observed mean resistivity reduction attributed to infiltrating water during irrigation was scaled to pressure head. Mean variations in pore pressure were reproduced by a linear diffusion model also used in physically-based dynamic landslide susceptibility modelling. Sensitive parameters (hydraulic conductivity and specific storage) were tested over selected value ranges and calibrated. Calibrated parameter values are within published and experimentally derived ranges. The results of the comparison of observations and model results suggest that the model is capable of reproducing mean changes of pore pressure at a suitable scale for physically-based modelling of shallow landslide susceptibility. However, small-scale variations in pore pressure that may facilitate the triggering of shallow landslides are not captured by the model.
Synchrotron infrared spectroscopy at megabar pressures - Vibrational dynamics of hydrogen to 180 GPa
Hanfland, M.; Hemley, R. J.; Mao, H. K.; Williams, G. P.
1992-01-01
New techniques for measuring infrared spectra at megabar pressures using synchrotron radiation have been developed and applied to study the Q1(1), Qi(1) + Si(0), and QR(J) vibrational transitions of solid hydrogen to 180 GPa. The frequency difference between the Q1(1) infrared and Raman vibrons increases from 3/cm (zero pressure) to 510/cm (180 GPa), indicating a dramatic increase in intermolecular coupling with pressure. A negative frequency shift is observed for the infrared vibron above 140 GPa. A significant increase in frequency and LO-TO splitting of the lattice phonon is also documented.
Zelveian, P A; Buniatian, M S; Oshchepkova, E V; Lazareva, N V; Rogoza, A N
2011-01-01
Aim of this study was to evaluate possible relationship between parameters of blood pressure (BP) profile and glomerular filtration rate in patients (pts) with I-II stage essential hypertension (EH). Material and methods. We studied 120 pts (97 men), aged 23-65 (50,2+/-0,6) years with I (n=98) and II (n=22) stage EH. In BP profile (SL-90207) we calculated 24-hour, daytime, nighttime values of systolic, diastolic, pulse pressures (SBP, DBP, PP), time load (TL), variability and nocturnal fall (NF) of BP. The state of renal function was assessed by measurement of glomerular filtration rate (GFR) calculated by the Cockcroft formula. Results. After nonlinear statistical analysis by Gauss-Newton all patients were divided into three groups according to GFR tertiles. Significant differences were found between these groups by 24-hour, nighttime and daytime values of SBP and DBP. Values of SBP were the lowest in group II. In group II lowest values of PP were also observed, but statistically significant differences were found only in nocturnal PP values between groups II and III. There were no significant differences between groups by TL and NF of BP. In group Ill (high GFR) variability of daytime values of SBP and DBF were significantly higher. Univariate correlation analysis showed statistically significant negative relationship between GFR and nocturnal PP in patients with lowest level of GFR. Positive correlations between nocturnal values of PP and GFR in groups II and III were also observed. Conclusion. These results indicated the presence of strong relationship between high values of nocturnal PP and decreasing of glomerular filtration rate in patients with EH and thus confirmed significance of "constant" and "dynamic" components of pressure load as a marker of impairment of renal function.
Alemela, Panduranga Reddy; Roman Casado, Juan; Tarband Veeraraghavan, Santos Kumar; Kok, Jim
2013-01-01
In this work comprehensive experimental and numerical studies incorporating the most relevant physical mechanisms causing limit cycle pressure and combustion rate oscillations (LCO) in a laboratory scale combustor will be discussed. The strong interaction between the aerodynamics-combustion-acoustic
C.J.J. Avezaat (Cees); J.H.M. van Eijndhoven (Johannes Hubertus Marcellianus)
1984-01-01
textabstractSince the introduction of continuous recording of intracranial pressure (ICP) in neurosurgical practice (Guillaume and Janny, 1951; Lundberg, 1960) this method has greatly contributed to clinical research in the field of intracranial hypertension. Numerous publications have enriched the
Prosthetics socket that incorporates an air splint system focusing on dynamic interface pressure
Razak, Nasrul Anuar Abd; Osman, Noor Azuan Abu; Gholizadeh, Hossein; Ali, Sadeeq
2014-01-01
Background The interface pressure between the residual limb and prosthetic socket has a significant effect on an amputee’s satisfaction and comfort. This paper presents the design and performance of a new prosthetic socket that uses an air splint system. Methods The air splint prosthetic socket system was implemented by combining the air splint with a pressure sensor that the transhumeral user controls through the use of a microcontroller. The modular construction of the system developed allo...
Probing of Fast Chemical Dynamics at High Pressures and Temperatures using Pulsed Laser Techniques
2014-12-17
Goncharov. Hydrogen (deuterium) vibron frequency as a pressure comparison gauge at multi-Mbar pressures, Journal of Applied Physics, (08 2013): 73505...V. Struzhkin, Innokenty Kantor, Mark L. Rivers , D. Allen Dalton. X-ray diffraction in the pulsed laser heated diamond anvil cell, Review of...few-layered two-dimensional MoS2 in collaboration with Avinash Nayak and Professor Jung-Fu Lin at the University of Texas at Austin
Helm, Emma; Babyn, Paul [Hospital for Sick Children, Department of Diagnostic Imaging, Toronto (Canada); Talakoub, Omid; Alirezaie, Javad [Ryerson University, Department of Electrical and Computer Engineering, Toronto, ON (Canada); Grasso, Francesco; Engelberts, Doreen; Kavanagh, Brian P. [Hospital for Sick Children and the University of Toronto, Departments of Anesthesia and Critical Care Medicine and the Program in Pulmonary and Experimental Medicine, Toronto (Canada)
2009-01-15
Negative pressure ventilation via an external device ('iron lung') has the potential to provide better oxygenation with reduced barotrauma in patients with ARDS. This study was designed to see if oxygenation differences between positive and negative ventilation could be explained by CT. Six anaesthetized rabbits had ARDS induced by repeated saline lavage. Rabbits were ventilated with positive pressure ventilation (PPV) and negative pressure ventilation (NPV) in turn. Dynamic CT images were acquired over the respiratory cycle. A computer-aided method was used to segment the lung and calculate the range of CT densities within each slice. Volumes of ventilated lung and atelectatic lung were measured over the respiratory cycle. NPV was associated with an increased percentage of ventilated lung and decreased percentage of atelectatic lung. The most significant differences in ventilation and atelectasis were seen at mid-inspiration and mid-expiration (ventilated lung NPV=61%, ventilated lung PPV=47%, p<0.001; atelectatic lung NPV=10%, atelectatic lung PPV 19%, p<0.001). Aeration differences were not significant at end-inspiration. Dynamic CT can show differences in lung aeration between positive and negative ventilation in ARDS. These differences would not be appreciated if only static breath-hold CT was used. (orig.)
Maximum Autocorrelation Factorial Kriging
Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.; Steenfelt, Agnete
2000-01-01
This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from an ordinary non-spatial factor analysis, and they are interpreted in a geological context. It is demonstrated that MAF analysis contrary to ordinary non-spatial factor analysis gives an objective discrimina...
Venkataraman, Pranav; Browd, Samuel R; Lutz, Barry R
2016-09-01
OBJECTIVE The surgical placement of a shunt designed to resolve the brain's impaired ability to drain excess CSF is one of the most common treatments for hydrocephalus. The use of a dynamic testing platform is an important part of shunt testing that can faithfully reproduce the physiological environment of the implanted shunts. METHODS A simulation-based framework that serves as a proof of concept for enabling the application of virtual intracranial pressure (ICP) and CSF models to a physical shunt-testing system was engineered. This was achieved by designing hardware and software that enabled the application of dynamic model-driven inlet and outlet pressures to a shunt and the subsequent measurement of the resulting drainage rate. RESULTS A set of common physiological scenarios was simulated, including oscillations in ICP due to respiratory and cardiac cycles, changes in baseline ICP due to changes in patient posture, and transient ICP spikes caused by activities such as exercise, coughing, sneezing, and the Valsalva maneuver. The behavior of the Strata valve under a few of these physiological conditions is also demonstrated. CONCLUSIONS Testing shunts with dynamic ICP and CSF simulations can facilitate the optimization of shunts to be more failure resistant and better suited to patient physiology.
Xiangwei Kong
2015-01-01
Full Text Available A dynamic pressure wave velocity model is presented based on momentum equation, mass-balance equation, equation of state, and small perturbation theory. Simultaneously, the drift model was used to analyze the flow characteristics of oil, gas, water, and drilling fluid multiphase flow. In addition, the dynamic model considers the gas dissolution, virtual mass force, drag force, and relative motion of the interphase as well. Finite difference and Newton-Raphson iterative are introduced to the numerical simulation of the dynamic model. The calculation results indicate that the wave velocity is more sensitive to the increase of gas influx rate than the increase of oil/water influx rate. Wave velocity decreases significantly with the increase of gas influx. Influenced by the pressure drop of four-phase fluid flowing along the annulus, wave velocity tends to increase with respect to well depth, contrary to the gradual reduction of gas void fraction at different depths with the increase of backpressure (BP. Analysis also found that the growth of angular frequency will lead to an increase of wave velocity at low range. Comparison with the calculation results without considering virtual mass force demonstrates that the calculated wave velocity is relatively bigger by using the presented model.
Hsun-Wen Chang
Full Text Available OBJECTIVES: The purpose of this study was to examine the correlation between the foot arch volume measured from static positions and the plantar pressure distribution during walking. METHODS: A total of 27 children, two to six years of age, were included in this study. Measurements of static foot posture were obtained, including navicular height and foot arch volume in sitting and standing positions. Plantar pressure, force and contact areas under ten different regions of the foot were obtained during walking. RESULTS: The foot arch index was correlated (r = 0.32 with the pressure difference under the midfoot during the foot flat phase. The navicular heights and foot arch volumes in sitting and standing positions were correlated with the mean forces and pressures under the first (r = -0.296∼-0.355 and second metatarsals (r = -0.335∼-0.504 and midfoot (r = -0.331∼-0.496 during the stance phase of walking. The contact areas under the foot were correlated with the foot arch parameters, except for the area under the midfoot. CONCLUSIONS: The foot arch index measured in a static position could be a functional index to predict the dynamic foot functions when walking. The foot arch is a factor which will influence the pressure distribution under the foot. Children with a lower foot arch demonstrated higher mean pressure and force under the medial forefoot and midfoot, and lower contact areas under the foot, except for the midfoot region. Therefore, children with flatfoot may shift their body weight to a more medial foot position when walking, and could be at a higher risk of soft tissue injury in this area.
Chouet, Bernard A.; Dawson, Phillip B.; Nakano, Masaru
2006-01-01
We present a model of gas exsolution and bubble expansion in a melt supersaturated in response to a sudden pressure drop. In our model, the melt contains a suspension of gas bubbles of identical sizes and is encased in a penny-shaped crack embedded in an elastic solid. The suspension is modeled as a three-dimensional lattice of spherical cells with slight overlap, where each elementary cell consists of a gas bubble surrounded by a shell of volatile-rich melt. The melt is then subjected to a step drop in pressure, which induces gas exsolution and bubble expansion, resulting in the compression of the melt and volumetric expansion of the crack. The dynamics of diffusion-driven bubble growth and volumetric crack expansion span 9 decades in time. The model demonstrates that the speed of the crack response depends strongly on volatile diffusivity in the melt and bubble number density and is markedly sensitive to the ratio of crack thickness to crack radius and initial bubble radius but is relatively insensitive to melt viscosity. The net drop in gas concentration in the melt after pressure recovery represents only a small fraction of the initial concentration prior to the drop, suggesting the melt may undergo numerous pressure transients before becoming significantly depleted of gases. The magnitude of pressure and volume recovery in the crack depends sensitively on the size of the input-pressure transient, becoming relatively larger for smaller-size transients in a melt containing bubbles with initial radii less than 10-5 m. Amplification of the input transient may be large enough to disrupt the crack wall and induce brittle failure in the rock matrix surrounding the crack. Our results provide additional basis for the interpretation of volume changes in the magma conduit under Popocatépetl Volcano during Vulcanian degassing bursts in its eruptive activity in April–May 2000.
Hodder, K.J.; Izadi, H. [Department of Chemical and Materials Engineering, University of Alberta, 7th Floor, Electrical and Computer Engineering Research Facility, Edmonton, Alberta, Canada T6G 2V4 (Canada); McDonald, A.G. [Department of Mechanical Engineering, University of Alberta, 4-9 Mechanical Engineering Building, Edmonton, Alberta, Canada T6G 2G8 (Canada); Gerlich, A.P., E-mail: agerlich@uwaterloo.ca [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1 (Canada)
2012-10-30
Cold gas dynamic spraying at low pressure (1 MPa gage or 150 psig) was used to fabricate Al-Al{sub 2}O{sub 3} metal matrix composite (MMC) coatings onto 6061 Al alloy. The powder contained Al powder admixed with -10 {mu}m Al{sub 2}O{sub 3} in fractions up to 90 wt.%. Scanning electron microscopy (SEM), Vickers microhardness testing, and image analysis were conducted to determine the microstructure, properties, and volume fraction of reinforcing particles in the coatings. The coatings were then friction-stir processed (FSP) at tool rotation speeds of 894 or 1723 RPM using a flat cylindrical tool. The Al{sub 2}O{sub 3} content and hardness of the final MMC coatings increased with increasing fractions of Al{sub 2}O{sub 3} particles in the feedstock powder, resulting in a maximum Al{sub 2}O{sub 3} content of 48 wt.% and a hardness of 85 HV of the as-sprayed coating when 90 wt.% Al{sub 2}O{sub 3} was used in the feed powder blend. After FSP, the hardness of the MMC increased to a maximum of 137 HV. The as-sprayed coatings contained Al{sub 2}O{sub 3} particles that were segregated between the Al particles, and FSP was effective in dispersing these Al{sub 2}O{sub 3} particles and decreasing their mean free path. It was suggested that this re-distribution and Al{sub 2}O{sub 3} particle size refinement during FSP improved the hardness of the MMC coatings.
Mehlhorn, Alexander T; Walther, Markus; Yilmaz, Tayfun
2017-01-01
of life. 17 consecutive patients suffering from a Lisfranc fracture dislocation were registered, underwent open reduction and internal fixation and were followed-up for 50.5±25.7months (Mean±SDM). Biomechanical analysis of muscle strength capacities, postural control and plantar pressure distribution...... correlated well with clinical outcome. Altered postural control was evident by a significant reduction in unilateral stance time, from which we calculated a strong correlation between stance time and the isokinetic strength measurement. Plantar pressure measurements revealed a significant reduction in peak...... pressure under the midfoot and of Force-Time Integral beneath the second metatarsal. Sufficient rehabilitation is crucial to the clinical outcome following anatomical open reduction of Lisfranc fracture-dislocation. The present study supports a rehabilitation approach focussing on restoring proprioception...
Clarke, Elizabeth C; Fletcher, David F; Stoodley, Marcus A; Bilston, Lynne E
2013-07-26
The pathogenesis of syringomyelia in association with Chiari malformation (CM) is unclear. Studies of patients with CM have shown alterations in the CSF velocity profile and these could contribute to syrinx development or enlargement. Few studies have considered the fluid mechanics of CM patients with and without syringomyelia separately. Three subject-specific CFD models were developed for a normal participant, a CM patient with syringomyelia and a CM patient without syringomyelia. Model geometries, CSF flow rate data and CSF velocity validation data were collected from MRI scans of the 3 subjects. The predicted peak CSF pressure was compared for the 3 models. An extension of the study performed geometry and flow substitution to investigate the relative effects of anatomy and CSF flow profile on resulting spinal CSF pressure. Based on 50 monitoring locations for each of the models, the CM models had significantly higher magnitude (psyringomyelia mechanisms and relative effects of CSF velocity profile and spinal geometry on CSF pressure.
无
2009-01-01
The sources of ultra low frequency (ULF) waves in the magnetosphere are generally believed to be either the external solar wind perturbations or the internal plasma instabilities. When a sudden impulse of the solar wind dynamic pressure impinges on the magnetopause, ULF waves might be excited and thus the solar wind energy is transported into the earth’s magnetosphere. In this paper, we study the ULF waves excited by different kinds of sudden solar wind pressure impulses through an MHD simulation. We primarily focus on the responses of the earth’s magnetosphere to positive/negative impulses of solar wind dynamic pressure, and positive-negative impulse pairs. The simulation results show that the ULF waves excited by positive and negative impulse have the same amplitude and frequency, with 180° difference in phase, if the amplitude and durations of the input impulses are the same. In addition, it is found that field line resonances (FLRs) occur at certain L-shell regions of the earth’s magneto-sphere after the impact of different positive-negative impulse pairs, which appear to be related to the duration of the impulses and the time interval between the sequential impulses. Another result is that the energy from the solar wind could be transported deeper into the inner magnetosphere by an impulse pair than by a single pulse impact. The results presented in this paper could help us to better understand how energy is transported from solar wind to the earth’s magnetosphere via ULF waves. Also, these results provide some new clues to understanding of how energetic particles in the inner magnetosphere response to different kinds of solar wind pressure impulse impacts including inter-planetary shocks.
Xiao, Hai [Clemson Univ., SC (United States); Tsai, Hai-Lung [Missouri Univ. of Science and Technology, Rolla, MO (United States); Dong, Junhang [Univ. of Cincinnati, OH (United States)
2014-09-30
This is the final report for the program “Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High Temperature and Dynamic Gas Pressure in Harsh Environments”, funded by NETL, and performed by Missouri University of Science and Technology, Clemson University and University of Cincinnati from October 1, 2009 to September 30, 2014. Securing a sustainable energy economy by developing affordable and clean energy from coal and other fossil fuels is a central element to the mission of The U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). To further this mission, NETL funds research and development of novel sensor technologies that can function under the extreme operating conditions often found in advanced power systems. The main objective of this research program is to conduct fundamental and applied research that will lead to successful development and demonstration of robust, multiplexed, microstructured silica and single-crystal sapphire fiber sensors to be deployed into the hot zones of advanced power and fuel systems for simultaneous measurements of high temperature and gas pressure. The specific objectives of this research program include: 1) Design, fabrication and demonstration of multiplexed, robust silica and sapphire fiber temperature and dynamic gas pressure sensors that can survive and maintain fully operational in high-temperature harsh environments. 2) Development and demonstration of a novel method to demodulate the multiplexed interferograms for simultaneous measurements of temperature and gas pressure in harsh environments. 3) Development and demonstration of novel sapphire fiber cladding and low numerical aperture (NA) excitation techniques to assure high signal integrity and sensor robustness.
Dynamics of epidemic spreading with vaccination: Impact of social pressure and engagement
Pires, Marcelo A.; Crokidakis, Nuno
2017-02-01
In this work we consider a model of epidemic spreading coupled with an opinion dynamics in a fully-connected population. Regarding the opinion dynamics, the individuals may be in two distinct states, namely in favor or against a vaccination campaign. Individuals against the vaccination follow a standard SIS model, whereas the pro-vaccine individuals can also be in a third compartment, namely Vaccinated. In addition, the opinions change according to the majority-rule dynamics in groups with three individuals. We also consider that the vaccine can give permanent or temporary immunization to the individuals. By means of analytical calculations and computer simulations, we show that the opinion dynamics can drastically affect the disease propagation, and that the engagement of the pro-vaccine individuals can be crucial for stopping the epidemic spreading. The full numerical code for simulating the model is available from the authors' webpage.
Dynamics of epidemic spreading with vaccination: impact of social pressure and engagement
Pires, Marcelo A
2016-01-01
In this work we consider a model of epidemic spreading coupled with an opinion dynamics in a fully-connected population. Regarding the opinion dynamics, the individuals may be in two distinct states, namely in favor or against a vaccination campaign. Individuals against the vaccination follow a standard SIS model, whereas the pro-vaccine individuals can also be in a third compartment, namely Vaccinated. In addition, the opinions change according to the majority-rule dynamics in groups with three individuals. We also consider that the vaccine can give permanent or temporary immunization to the individuals. By means of analytical calculations and computer simulations, we show that the opinion dynamics can drastically affect the disease propagation, and that the engagement of the pro-vaccine individuals can be crucial for stopping the epidemic spreading.
Lim, Sangwook; Zhang, Hua; Wu, Pingkeng; Nikolov, Alex; Wasan, Darsh
2016-05-15
Nanofluids comprising nanoparticle suspensions in liquids have significant industrial applications. Prior work performed in our laboratory on the spreading of an aqueous film containing nanoparticles displacing an oil droplet has clearly revealed that the structural disjoining pressure arises due to the layering of the nanoparticles normal to the confining plane of the film with the wedge profile. The pressure drives the nanofluid in the wedge film and the nanofluid spreads. We observed two distinct contact lines: the inner contact line, where the structural disjoining pressure dominates the Laplace capillary pressure, and the outer contact line, given by the Laplace equation prediction extrapolated to the solid substrate where the structural disjoining pressure contribution is negligible. We report here our results of the effects of several parameters, such as the nanoparticle concentration, liquid salinity, temperature, and the substrate contact angle, on the motion of the two contact lines and their effects on the detachment of the oil droplet. We also studied the equilibrated and non-equilibrated oil/nanofluid phases, the time of adhesion of the oil droplet on the solid substrate and the drying time of the substrate. We employed the frictional model to predict the outer contact line velocity and our previous theoretical model (based on the structural disjoining pressure) to predict the inner contact line velocity. The theoretical predictions agreed quite well with the experimentally measured values of the velocities. Our experimental results showed that the motion of the inner contact line was accelerated by the increase in the nanoparticle concentration, temperature, and hydrophilicity of the substrate for the pre-equilibrated oil/nanofluid phases, which resulted in the faster detachment of the oil droplet. The speed of the two contact lines decreased upon the increase in the drying time of the substrate and the oil adhesion time on the substrate. The present
Decreasing deer browsing pressure influenced understory vegetation dynamics over 30 years
Boulanger, Vincent; Baltzinger, Christophe; Saïd, Sonia; Ballon, Philippe; Picard, Jean-Francois; Dupouey, Jean-Luc
2015-01-01
Key message Thanks to the concomitant recordings of vegetation and deer browsing sampled first in 1976, then resurveyed in 2006, we show that forest plant communities shifted in response to deer population dynamics, stand management and eutrophication. Context and aims High deer populations alter forest under-story dynamics worldwide. However, no study ever attempted to rank the importance of deer herbivory relatively to other environmental drivers. In the Arc-en-Barrois National Forest (...
Mechanical properties of reactor pressure vessel steels studied by static and dynamic torsion tests
Munier, A.; Maamouri, M.; Schaller, R.; Mercier, O.
1993-06-01
Internal friction measurements and torsional plastic deformation tests have been performed in reactor pressure vessel steels (unirradiated, irradiated and irradiated/annealed specimens). The results of these experiments have been interpreted with help of transmission electron microscopy observations (conventional and in situ). It is shown how the interactions between screw dislocations and obstacles (Peierls valleys, impurities and precipitates) could explain the low temperature hardening and the irradiation embrittlement of ferritic steels. In addition, it appears that the nondestructive internal friction technique could be used advantageously to follow the evolution of the material properties under irradiation, as for instance the irradiation embrittlement of the reactor pressure vessel steels.
Dynamic characteristics research of the pressure reducing valve based on AMESim
Wang, Weihui; Zhang, Peiyi
2017-05-01
Through the analysis of the structure and working principle of pressure reducing valve, using AMESim software to model, simulate and analyze its working conditions On the basis of the analysis of the structural parameters of the valve: damping hole diameter D, analog load damping hole diameter D1, spring stiffness K and initial opening S 0f analog load, such as which has the impact of hydraulic pressure reducing valve Finally, the influence of the above parameters on the accuracy of the valve is analyzed, which provides a reference for the design of the valve.
Tsatsanidi, K N; Pugaev, A V; Gordeev, P S; Sandrikov, V A; Mukha, A V; Gambarian, A R
1991-02-01
Intraoperative cholangio-manometry with a miniature tensor sensor and graphic recording of the results were conducted to study the function of the major duodenal papilla in 53 patients. A periodical activity of the ampulla of the papilla was revealed, which was characterized by certain values of the peak and basal pressure, and duration of contraction and relaxation periods. The numerical values and the pattern of the pressure curve differed in patients with obstructive cholecystitis, biliary pancreatitis, and a concrement incarcerated in the ampulla of the papilla. The informativeness of the study increases with the use of the glucagon test.
Numerical investigation of vibration and dynamic pressure of a vertical axis wind turbine
F Erchiqui
2016-10-01
Full Text Available In the environmental field, the problems of noise reduction have become a major preoccupation, particularly on the noise generated by the acoustic radiation pressure produced by wind turbines. This paper is aimed at presenting the investigation on the application of variational indirect boundary element method for study the acoustic radiation pressure produced by vertical-axis wind turbine. For this initiative, we considered Neumann boundary condition. The formulation has two advantages: the first one is to avoid the meshing of the fluid domain; the second advantage is to treat the singular integral of the Green's function, solution of fundamental solution of the wave equation in frequency domain.
The Grüneisen Parameter of NaCl at High Pressures and Temperatures: a Molecular Dynamics Study
CAI Ling-Cang; CHEN Qi-Feng; CUI Shou-Xin; JING Fu-Qian
2005-01-01
@@ The isotherms and Griineisen parameters are calculated by using the molecular dynamics (MD) method with an improved Tosi-Fumi pair potential. The results show that the approximate power law dependence of the Griineisen parameter on compression γ = γo( V/Vo )q, with q ≈ 1.078, holds in the temperature range from 298 to 1073K and pressure range from 0 to 60 GPa, and that the Griineisen parameter for a given density of 2.16g/cm3varies with temperature in a wind range from 300 to 10000K, expressed by γ = 1.052 + 0.582exp(-T/4878.56).
Zhang, Hong
2016-01-01
Motivated by observations of saturation overshoot, this paper investigates numerical modeling of two-phase flow incorporating dynamic capillary pressure. The effects of the dynamic capillary coefficient, the infiltrating flux rate and the initial and boundary values are systematically studied using a travelling wave ansatz and efficient numerical methods. The travelling wave solutions may exhibit monotonic, non-monotonic or plateau-shaped behaviour. Special attention is paid to the non-monotonic profiles. The travelling wave results are confirmed by numerically solving the partial differential equation using an accurate adaptive moving mesh solver. Comparisons between the computed solutions using the Brooks-Corey model and the laboratory measurements of saturation overshoot verify the effectiveness of our approach.
A pipe network simulation model with dynamic transition between free surface and pressurized flow
J. Fernández-Pato
2014-01-01
Full Text Available Water flow numerical simulation in urban pipe systems is one of the topics that shows the need for surface flows and pressurized flows in steady and transient situations. The governing equations for both flow types are different and this must be taken into account in order to get a complete numerical model for solving transients. A numerical simulation model is developed in this work, capable of solving pipe networks mainly unpressurized, with isolated peaks of pressurization. For this purpose, a reformulation of the mathematical model through the Preissmann slot method is proposed. By means of this technique, a reasonable estimation of the water pressure is calculated in cases of pressurization. The numerical model is based on the first order Roe's scheme, in the frame of finite volume methods. It is adapted to abrupt transient situations, with subcritial and supercritical flows. The validation has been done by means of several cases with analytic solutions or empirical laboratory data. It has also been applied to some more complex and realistic cases, like junctions or pipe networks.
The Dynamics of Divorce: Marital Quality, Alternative Attractions and External Pressures.
Green, Robert G.; Sporakowski, Michael J.
1983-01-01
Tested Lewis and Spanier's theory of marital quality and marital stability using a sample of 131 married and 166 divorced social survey respondents. Examined the relationship between the quality and stability of their marriages and assessed the influence of alternative attractions and external pressures to remain married. (JAC)
Dynamic Testing and Evaluation of Pressure Transducer-Catheter Systems: A Student Project.
Barquest, James M.; Schmalzel, John L.
Described are four demonstration/participation laboratories in which students analytically and experimentally evaluated various catheter-transducer blood pressure measurement systems. The activities were included in a graduate level course entitled "Theory and Techniques of Bioinstrumentation," taught by the Department of Electrical Engineering…
Experimental Studies of Dynamic Fault Weakening Due to Thermal Pressurization of Pore Fluids
Goldsby, David; Tullis, Terry; Platt, John; Okazaki, Keishi
2016-04-01
High-velocity friction experiments and geophysical observations suggest that mature faults weaken dramatically during seismic slip. However, while many coseismic weakening mechanisms have been proposed, it is still unclear which mechanisms are most important or how the efficiency of weakening varies within the seismogenic zone. Thermal pressurization is one possible coseismic weakening mechanism driven by the thermal expansion of native pore fluids, which leads to elevated pore pressures and significant coseismic weakening. While thermal pressurization has been studied theoretically for many decades, and invoked in recent earthquake simulations, its activation in laboratory experiments has remained elusive. Several high-speed friction studies have yielded indirect evidence for thermal pressurization, yet none has directly linked with existing theoretical models or the relevant physical parameters, such as permeability, slip, and slip rate, that control the weakening rate. To fill this gap, we are conducting thermal pressurization experiments on fluid-saturated, low-permeability rocks (Frederick diabase) at slip rates up to ~5 mm/s, at constant confining pressures in the range 21-149 MPa and initial imposed pore pressures in the range 10-25 MPa. The impractically low permeability of the as-is diabase, ~10-23 m2, is increased prior to the test by thermal cracking, yielding measured permeabilities in the range 1.3*10-18 to 6.1*10-19 m2. These values of permeability are high enough to allow sample saturation over one to several days, but low enough to confine the elevated pore pressures generated by frictional heating during rapid sliding. Our experiments reveal a rapid decay of shear stress following a step-change in velocity from 10 μm/s to 4.8 mm/s. In one test, the decrease in shear stress of ~25% over the first 28 mm of slip at 4.8 mm/s agrees closely with the theoretical solution for slip on a plane (Rice [2006]), with an inferred slip-weakening distance of ~500