Fundamental characteristics and simplified evaluation method of dynamic earth pressure

International Nuclear Information System (INIS)

Nukui, Y.; Inagaki, Y.; Ohmiya, Y.

1989-01-01

In Japan, a method is commonly used in the evaluation of dynamic earth pressure acting on the underground walls of a deeply embedded nuclear reactor building. However, since this method was developed on the basis of the limit state of soil supported by retaining walls, the behavior of dynamic earth pressure acting on the embedded part of a nuclear reactor building may differ from the estimated by this method. This paper examines the fundamental characteristics of dynamic earth pressure through dynamic soil-structure interaction analysis. A simplified method to evaluate dynamic earth pressure for the design of underground walls of a nuclear reactor building is described. The dynamic earth pressure is fluctuating earth pressure during earthquake

Maximum home blood pressure is a useful indicator of diabetic nephropathy in patients with type 2 diabetes mellitus: KAMOGAWA-HBP study.

Science.gov (United States)

Oyabu, Chikako; Ushigome, Emi; Matsumoto, Shinobu; Tanaka, Toru; Hasegawa, Goji; Nakamura, Naoto; Ohnishi, Masayoshi; Tsunoda, Sei; Ushigome, Hidetaka; Yokota, Isao; Tanaka, Muhei; Asano, Mai; Yamazaki, Masahiro; Fukui, Michiaki

2017-11-01

Maximum home systolic blood pressure has been shown to predict target organ damage. We aimed to clarify the association between maximum home systolic blood pressure and urine albumin to creatinine ratio, an indicator of early-phase diabetic nephropathy in patients with type 2 diabetes. In 1040 patients, we assessed the relationship of mean or maximum home systolic blood pressure and urine albumin to creatinine ratio, and compared the area under the receiver operating characteristic curve of mean or maximum home systolic blood pressure for diabetic nephropathy (urine albumin to creatinine ratio ⩾30 mg/g Cr). Multivariate linear regression analyses indicated that mean morning systolic blood pressure ( β = 0.010, p blood pressure ( β = 0.008, p blood pressure was 0.667 (0.634-0.700; p blood pressure, as well as mean home systolic blood pressure, was significantly associated with diabetic nephropathy in patients with type 2 diabetes.

Pressure dynamic characteristics of pressure controlled ventilation system of a lung simulator.

Science.gov (United States)

Shi, Yan; Ren, Shuai; Cai, Maolin; Xu, Weiqing; Deng, Qiyou

2014-01-01

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.

Perspective: Maximum caliber is a general variational principle for dynamical systems.

Science.gov (United States)

Dixit, Purushottam D; Wagoner, Jason; Weistuch, Corey; Pressé, Steve; Ghosh, Kingshuk; Dill, Ken A

2018-01-07

We review here Maximum Caliber (Max Cal), a general variational principle for inferring distributions of paths in dynamical processes and networks. Max Cal is to dynamical trajectories what the principle of maximum entropy is to equilibrium states or stationary populations. In Max Cal, you maximize a path entropy over all possible pathways, subject to dynamical constraints, in order to predict relative path weights. Many well-known relationships of non-equilibrium statistical physics-such as the Green-Kubo fluctuation-dissipation relations, Onsager's reciprocal relations, and Prigogine's minimum entropy production-are limited to near-equilibrium processes. Max Cal is more general. While it can readily derive these results under those limits, Max Cal is also applicable far from equilibrium. We give examples of Max Cal as a method of inference about trajectory distributions from limited data, finding reaction coordinates in bio-molecular simulations, and modeling the complex dynamics of non-thermal systems such as gene regulatory networks or the collective firing of neurons. We also survey its basis in principle and some limitations.

Perspective: Maximum caliber is a general variational principle for dynamical systems

Science.gov (United States)

Dixit, Purushottam D.; Wagoner, Jason; Weistuch, Corey; Pressé, Steve; Ghosh, Kingshuk; Dill, Ken A.

2018-01-01

We review here Maximum Caliber (Max Cal), a general variational principle for inferring distributions of paths in dynamical processes and networks. Max Cal is to dynamical trajectories what the principle of maximum entropy is to equilibrium states or stationary populations. In Max Cal, you maximize a path entropy over all possible pathways, subject to dynamical constraints, in order to predict relative path weights. Many well-known relationships of non-equilibrium statistical physics—such as the Green-Kubo fluctuation-dissipation relations, Onsager's reciprocal relations, and Prigogine's minimum entropy production—are limited to near-equilibrium processes. Max Cal is more general. While it can readily derive these results under those limits, Max Cal is also applicable far from equilibrium. We give examples of Max Cal as a method of inference about trajectory distributions from limited data, finding reaction coordinates in bio-molecular simulations, and modeling the complex dynamics of non-thermal systems such as gene regulatory networks or the collective firing of neurons. We also survey its basis in principle and some limitations.

Effect of Ovality on Maximum External Pressure of Helically Coiled Steam Generator Tubes with a Rectangular Wear

Energy Technology Data Exchange (ETDEWEB)

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

Pressure Dynamic Characteristics of Pressure Controlled Ventilation System of a Lung Simulator

Directory of Open Access Journals (Sweden)

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.

Pressure Dynamic Characteristics of Pressure Controlled Ventilation System of a Lung Simulator

Science.gov (United States)

Shi, Yan; Ren, Shuai; Cai, Maolin; Xu, Weiqing; Deng, Qiyou

2014-01-01

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. PMID:25197318

Pressure dependence of dynamical heterogeneity in water

International Nuclear Information System (INIS)

Teboul, Victor

2008-01-01

Using molecular dynamics simulations we investigate the effect of pressure on the dynamical heterogeneity in water. We show that the effect of a pressure variation in water is qualitatively different from the effect of a temperature variation on the dynamical heterogeneity in the liquid. We observe a strong decrease of the aggregation of molecules of low mobility together with a decrease of the characteristic time associated with this aggregation. However, the aggregation of the most mobile molecules and the characteristic time of this aggregation are only slightly affected. In accordance with this result, the non-Gaussian parameter shows an important decrease with pressure while the characteristic time t* of the non-Gaussian parameter is only slightly affected. These results highlight then the importance of pressure variation investigations in low temperature liquids on approach to the glass transition

A novel polarization demodulation method using polarization beam splitter (PBS) for dynamic pressure sensor

Science.gov (United States)

Su, Yang; Zhou, Hua; Wang, Yiming; Shen, Huiping

2018-03-01

In this paper we propose a new design to demodulate polarization properties induced by pressure using a PBS (polarization beam splitter), which is different with traditional polarimeter based on the 4-detector polarization measurement approach. The theoretical model is established by Muller matrix method. Experimental results confirm the validity of our analysis. Proportional relationships and linear fit are found between output signal and applied pressure. A maximum sensitivity of 0.092182 mv/mv is experimentally achieved and the frequency response exhibits a <0.14 dB variation across the measurement bandwidth. The sensitivity dependence on incident SOP (state of polarization) is investigated. The simple and all-fiber configuration, low-cost and high speed potential make it promising for fiber-based dynamic pressure sensing.

Dynamic pressure as a measure of gas turbine engine (GTE) performance

International Nuclear Information System (INIS)

Rinaldi, G; Stiharu, I; Packirisamy, M; Nerguizian, V; Landry, R Jr; Raskin, J-P

2010-01-01

Utilizing in situ dynamic pressure measurement is a promising novel approach with applications for both control and condition monitoring of gas turbine-based propulsion systems. The dynamic pressure created by rotating components within the engine presents a unique opportunity for controlling the operation of the engine and for evaluating the condition of a specific component through interpretation of the dynamic pressure signal. Preliminary bench-top experiments are conducted with dc axial fans for measuring fan RPM, blade condition, surge and dynamic temperature variation. Also, a method, based on standing wave physics, is presented for measuring the dynamic temperature simultaneously with the dynamic pressure. These tests are implemented in order to demonstrate the versatility of dynamic pressure-based diagnostics for monitoring several different parameters, and two physical quantities, dynamic pressure and dynamic temperature, with a single sensor. In this work, the development of a dynamic pressure sensor based on micro-electro-mechanical system technology for in situ gas turbine engine condition monitoring is presented. The dynamic pressure sensor performance is evaluated on two different gas turbine engines, one having a fan and the other without

Dynamic pressure sensitivity determination with Mach number method

Science.gov (United States)

Sarraf, Christophe; Damion, Jean-Pierre

2018-05-01

Measurements of pressure in fast transient conditions are often performed even if the dynamic characteristic of the transducer are not traceable to international standards. Moreover, the question of a primary standard in dynamic pressure is still open, especially for gaseous applications. The question is to improve dynamic standards in order to respond to expressed industrial needs. In this paper, the method proposed in the EMRP IND09 ‘Dynamic’ project, which can be called the ‘ideal shock tube method’, is compared with the ‘collective standard method’ currently used in the Laboratoire de Métrologie Dynamique (LNE/ENSAM). The input is a step of pressure generated by a shock tube. The transducer is a piezoelectric pressure sensor. With the ‘ideal shock tube method’ the sensitivity of a pressure sensor is first determined dynamically. This method requires a shock tube implemented with piezoelectric shock wave detectors. The measurement of the Mach number in the tube allows an evaluation of the incident pressure amplitude of a step using a theoretical 1D model of the shock tube. Heat transfer, other actual effects and effects of the shock tube imperfections are not taken into account. The amplitude of the pressure step is then used to determine the sensitivity in dynamic conditions. The second method uses a frequency bandwidth comparison to determine pressure at frequencies from quasi-static conditions, traceable to static pressure standards, to higher frequencies (up to 10 kHz). The measurand is also a step of pressure generated by a supposed ideal shock tube or a fast-opening device. The results are provided as a transfer function with an uncertainty budget assigned to a frequency range, also deliverable frequency by frequency. The largest uncertainty in the bandwidth of comparison is used to trace the final pressure step level measured in dynamic conditions, owing that this pressure is not measurable in a steady state on a shock tube. A reference

Analysis of the dynamic response of a double rupture disc assembly to simulated sodium-water reaction pressure pulses

International Nuclear Information System (INIS)

Leonard, J.R.

1980-03-01

A series of double rupture disc experiments were conducted in 1979 to evaluate the dynamic response characteristics of this pressure relief apparatus. The tests were performed in a facility with water simulating sodium and rising pressure pulses representative of the pressure increase resulting from a water/steam leak from a steam generator into sodium in the intermediate heat transport system of a breeder reactor power plant. Maximum source pressures ranged in magnitude from 50 psi to 800 psi. Dynamic response characteristics of each of the two rupture discs were similar to those observed in larger scale sodium-water experiments conducted in the Series I and Series II Large Leak Test Program at the Energy Technology Engineering Center. The SRI double rupture disc dynamic behavior was found to be consistent and amendable to modelling in the TRANSWRAP II computer code. A series of correlations which represent rupture disc buckling parameters were developed for use in the TRANSWRAP II code. The semi-empirical modeling of the rupture discs in the TRANSWRAP II code showed very good agreement with the experimental results

Magnetosheath dynamic pressure enhancements: occurrence and typical properties

Directory of Open Access Journals (Sweden)

M. O. Archer

2013-02-01

Full Text Available The first comprehensive statistical study of large-amplitude (> 100% transient enhancements of the magnetosheath dynamic pressure reveals events of up to ~ 15 times the ambient dynamic pressure with durations up to 3 min and an average duration of around 30 s, predominantly downstream of the quasi-parallel shock. The dynamic pressure transients are most often dominated by velocity increases along with a small fractional increase in the density, though the velocity is generally only deflected by a few degrees. Superposed wavelet transforms of the magnetic field show that, whilst most enhancements exhibit changes in the magnetosheath magnetic field, the majority are not associated with changes in the Interplanetary Magnetic Field (IMF. However, there is a minority of enhancements that do appear to be associated with solar wind discontinuities which cannot be explained simply by random events. In general, it is found that during periods of magnetosheath dynamic pressure enhancements the IMF is steadier than usual. This suggests that a stable foreshock and hence foreshock structures or processes may be important in the generation of the majority of magnetosheath dynamic pressure enhancements.

Osmosis-Based Pressure Generation: Dynamics and Application

Science.gov (United States)

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. PMID:24614529

Osmosis-based pressure generation: dynamics and application.

Science.gov (United States)

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.

Directory of Open Access Journals (Sweden)

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.

Approximation for maximum pressure calculation in containment of PWR reactors

International Nuclear Information System (INIS)

Souza, A.L. de

1989-01-01

A correlation was developed to estimate the maximum pressure of dry containment of PWR following a Loss-of-Coolant Accident - LOCA. The expression proposed is a function of the total energy released to the containment by the primary circuit, of the free volume of the containment building and of the total surface are of the heat-conducting structures. The results show good agreement with those present in Final Safety Analysis Report - FSAR of several PWR's plants. The errors are in the order of ± 12%. (author) [pt

[Effect of maximum blood pressure fluctuation on prognosis of patients with acute ischemic stroke within 24 hours after hospital admission].

Science.gov (United States)

Wang, H; Tang, Y; Zhang, Y; Xu, K; Zhao, J B

2018-05-10

Objective: To investigate the relationship between the maximum blood pressure fluctuation within 24 hours after admission and the prognosis at discharge. Methods: The patients with ischemic stroke admitted in Department of Neurology of the First Affiliated Hospital of Harbin Medical University within 24 hours after onset were consecutively selected from April 2016 to March 2017. The patients were grouped according to the diagnostic criteria of hypertension. Ambulatory blood pressure of the patients within 24 hours after admission were measured with bedside monitors and baseline data were collected. The patients were scored by NIHSS at discharge. The relationships between the maximum values of systolic blood pressure (SBP) or diastolic blood pressure (DBP) and the prognosis at discharge were analyzed. Results: A total of 521 patients with acute ischemic stroke were enrolled. They were divided into normal blood pressure group (82 cases) and hypertension group(439 cases). In normal blood pressure group, the maximum values of SBP and DBP were all in normal distribution ( P >0.05). The maximum value of SBP fluctuation was set at 146.6 mmHg. After adjustment for potential confounders, the OR for poor prognosis at discharge in patients with SBP fluctuation ≥146.6 mmHg was 2.669 (95 %CI : 0.594-11.992) compared with those with SBP fluctuation blood pressure at admission, the maximum values of SBP and DBP within 24 hours after admission had no relationship with prognosis at discharge. In acute ischemic stroke patients with hypertension at admission, the maximum values of SBP and DBP within 24 hours after admission were associated with poor prognosis at discharge.

Using pressure square-like wave to measure the dynamic characteristics of piezoelectric pressure sensor

International Nuclear Information System (INIS)

Han, L-L; Tsung, T-T; Chen, L-C; Chang Ho; Jwo, C-S

2005-01-01

Piezoelectric pressure sensors are commonly used to measuring the dynamic characteristics in a hydraulic system. The dynamic measurements require a pressure sensor which has a high response rate. In this paper, we proposed use of a pressure square wave to excite the piezoelectric pressure sensor. Experimental frequencies are 0.5, 1.0, 1.5, and 2.0 kHz at 10, 15, 20 bar, respectively. Results show that the waveform of time-domain and frequencydomain response are quite different under above testing conditions. The higher the frequencies tested, the faster the pressure-rise speeds obtained. Similarly, the higher the testing pressure, the shorter the rise time attained

Measurement of Dynamic Urethral Pressures with a High Resolution Manometry System in Continent and Incontinent Women

Science.gov (United States)

Kirby, Anna C; Tan-Kim, Jasmine; Nager, Charles W.

2015-01-01

Objectives Female stress urinary incontinence (SUI) is caused by urethral dysfunction during dynamic conditions, but current technology has limitations in measuring urethral pressures under dynamic conditions. An 8-French high resolution manometry catheter (HRM) currently in clinical use in gastroenterology may accurately measure urethral pressures under dynamic conditions because it has a 25ms response rate and circumferential pressure sensors along the length of the catheter (ManoScan® ESO, Given Imaging). We evaluated the concordance, repeatability, and tolerability of this catheter. Methods We measured resting, cough, and strain maximum urethral closure pressures (MUCPs) using HRM and measured resting MUCPs with water perfusion side-hole catheter urethral pressure profilometry (UPP) in 37 continent and 28 stress incontinent subjects. Maneuvers were repeated after moving the HRM catheter along the urethral length to evaluate whether results depend on catheter positioning. Visual analog pain scores evaluated the comfort of HRM compared to UPP. Results The correlation coefficient for resting MUCPs measured by HRM vs. UPP was high (r = 0.79, prest, cough, and strain with HRM: r= 0.92, 0.89, and 0.89. Mean MUCPs (rest, cough, strain) were higher in continent than incontinent subjects (all p continent subjects during cough and strain maneuvers compared to rest. Conclusions This preliminary study shows that HRM is concordant with standard technology, repeatable, and well tolerated in the urethra. Incontinent women have more impairment of their urethral closure pressures during cough and strain than continent women. PMID:25185595

Fluid Dynamics of Pressurized, Entrained Coal Gasifiers

International Nuclear Information System (INIS)

1997-01-01

Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we are conducting a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea is to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employ a unique entrained gas-solid flow facility with the flexibility to recycle--rather than discard--gases other than air. By matching five dimensionless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-upon the fluid dynamics of PECGs. Because it operates under cold, atmospheric conditions, the laboratory facility is ideal for detailed measurements

An investigation on effects of amputee's physiological parameters on maximum pressure developed at the prosthetic socket interface using artificial neural network.

Science.gov (United States)

Nayak, Chitresh; Singh, Amit; Chaudhary, Himanshu; Unune, Deepak Rajendra

2017-10-23

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.

Roller pressure algometry as a new tool for assessing dynamic pressure sensitivity in migraine

DEFF Research Database (Denmark)

Guerrero-Peral, Ángel L.; Ruíz, Marina; Barón, Johanna

2018-01-01

from 500 to 5300 g. Each roller was moved at a speed of 0.5 cm/sec over a 60 mm horizontal line covering the temporalis muscle. The dynamic pain threshold (the pressure level of the first painful roller) and pain elicited during the pain threshold (roller evoked pain) were determined. Static pressure...... pain thresholds were assessed over the temporalis muscle, C5/C6 joint, second metacarpal, and tibialis anterior. Results Side-to-side consistency between dynamic pain threshold (rs = 0.769, p ... was slightly stronger in chronic migraine. Pain during dynamic pain threshold was negatively associated with widespread pressure pain thresholds (-0.336 

Assessment of deep dynamic mechanical sensitivity in individuals with tension-type headache: The dynamic pressure algometry.

Science.gov (United States)

Palacios-Ceña, M; Wang, K; Castaldo, M; Guerrero-Peral, Á; Caminero, A B; Fernández-de-Las-Peñas, C; Arendt-Nielsen, L

2017-09-01

To explore the validity of dynamic pressure algometry for evaluating deep dynamic mechanical sensitivity by assessing its association with headache features and widespread pressure sensitivity in tension-type headache (TTH). One hundred and eighty-eight subjects with TTH (70% women) participated. Deep dynamic sensitivity was assessed with a dynamic pressure algometry set (Aalborg University, Denmark © ) consisting of 11 different rollers including fixed levels from 500 g to 5300 g. Each roller was moved at a speed of 0.5 cm/s over a 60-mm horizontal line covering the temporalis muscle. Dynamic pain threshold (DPT-level of the first painful roller) was determined and pain intensity during DPT was rated on a numerical pain rate scale (NPRS, 0-10). Headache clinical features were collected on a headache diary. As gold standard, static pressure pain thresholds (PPT) were assessed over temporalis, C5/C6 joint, second metacarpal, and tibialis anterior muscle. Side-to-side consistency between DPT (r = 0.843, p  r > 0.656, all p headaches supporting that deep dynamic pressure sensitivity within the trigeminal area is consistent with widespread pressure sensitivity. Assessing deep static and dynamic somatic tissue pain sensitivity may provide new opportunities for differentiated diagnostics and possibly a new tool for assessing treatment effects. The current study found that dynamic pressure algometry in the temporalis muscle was associated with widespread pressure pain sensitivity in individuals with tension-type headache. The association was independent of the frequency of headaches. Assessing deep static and dynamic somatic tissue pain sensitivity may provide new opportunities for differentiated diagnostics and possibly a tool for assessing treatment effects. © 2017 European Pain Federation - EFIC®.

A total pressure-saturation formulation of two-phase flow incorporating dynamic effects in the capillary-pressure-saturation relationship

Energy Technology Data Exchange (ETDEWEB)

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 preliminary

Induced topological pressure for topological dynamical systems

International Nuclear Information System (INIS)

Xing, Zhitao; Chen, Ercai

2015-01-01

In this paper, inspired by the article [J. Jaerisch et al., Stochastics Dyn. 14, 1350016, pp. 1-30 (2014)], we introduce the induced topological pressure for a topological dynamical system. In particular, we prove a variational principle for the induced topological pressure

Rate maximum calculation of Dpa in CNA-II pressure vessel

International Nuclear Information System (INIS)

Mascitti, J. A

2012-01-01

The maximum dpa rate was calculated for the reactor in the following state: fresh fuel, no Xenon, a Boron concentration of 15.3 ppm, critical state, its control rods in the criticality position, hot, at full power (2160 MW). It was determined that the maximum dpa rate under such conditions is 3.54(2)x10 12 s -1 and it is located in the positions corresponding to θ=210 o in the azimuthal direction, and z=20 cm and -60 cm respectively in the axial direction, considering the calculation mesh centered at half height of the fuel element (FE) active length. The dpa rate spectrum was determined as well as the contribution to it for 4 energy groups: a thermal group, two epithermal groups and a fast one. The maximum dpa rate considering the photo-neutrons production from (γ, n) reaction in the heavy water of coolant and moderator was 3.93(4)x10 12 s -1 that is 11% greater than the obtained without photo-neutrons. This verified significant difference between both cases, suggest that photo-neutrons in large heavy water reactors such as CNA-II should not be ignored. The maximum DPA rate in the first mm of the reactor pressure vessel was calculated too and it was obtained a value of 4.22(6)x10 12 s -1 . It should be added that the calculation was carried out with the reactor complete accurate model, with no approximations in spatial or energy variables. Each value has, between parentheses, a percentage relative error representing the statistical uncertainty due to the probabilistic Monte Carlo method used to estimate it. More representative values may be obtained with this method if equilibrium burn-up distribution is used (author)

Molecular Dynamics Simulations of Liquid Phosphorus at High Temperature and Pressure

International Nuclear Information System (INIS)

Wu Yanning; Zhao Gang; Liu Changsong; Zhu Zhengang

2008-01-01

By performing ab initio molecular dynamics simulations, we have investigated the microstructure, dynamical 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/cm 3 . Under compression, liquid P shows the first-order liquid-liquid phase transition from the molecular liquid composed of the tetrahedral P 4 molecules to complex polymeric form with three-dimensional network structure, accompanied by the nonmetal to metal transition of the electronic structure. The order parameters Q 6 and Q 4 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 phenomena 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

Pressurizer /Auxiliary Spray Piping Stress Analysis For Determination Of Lead Shielding Maximum Allow Able Load

International Nuclear Information System (INIS)

Setjo, Renaningsih

2000-01-01

Piping stress analysis for PZR/Auxiliary Spray Lines Nuclear Power Plant AV Unit I(PWR Type) has been carried out. The purpose of this analysis is to establish a maximum allowable load that is permitted at the time of need by placing lead shielding on the piping system on class 1 pipe, Pressurizer/Auxiliary Spray Lines (PZR/Aux.) Reactor Coolant Loop 1 and 4 for NPP AV Unit one in the mode 5 and 6 during outage. This analysis is intended to reduce the maximum amount of radiation dose for the operator during ISI ( In service Inspection) period.The result shown that the maximum allowable loads for 4 inches lines for PZR/Auxiliary Spray Lines is 123 lbs/feet

[Annual blood pressure dynamics and weather sensitivity in women].

Science.gov (United States)

Varlamova, N G; Zenchenko, T A; Boyko, E R

To study the annual cycle of blood pressure (BP) and weather sensitivity in normotensive women aged 20-59 years. The same group of 25 non-smoking women who had been living in the European North of Russia (62° N, 51° E) almost since their birth and were engaged in moderate-intensity mental labor was daily examined. During a year, there were 11823 blood pressure measurements using the Korotkoff technique; heart rate was calculated by palpation. These meteorological parameters were taken at the websites: http://meteo.infospace.ru and ftp://ftp.ngdc.noaa.gov/stp/geomagnetic_data/indices/kp_ap. The statistical significance of differences in the indicators was determined using the Fisher's test and the Newman-Keuls test. The study used a correlation analysis with the calculation of the Spearman's rank correlation coefficient. The maximum systolic and diastolic BP values were revealed in February and January, respectively. The minimum values of systolic BP were detected in July; those of diastolic BP were in August. An individual-based analysis of sensitivity to environmental variations showed that about 88% of the women responded to atmospheric temperature; nearly 44% did to geomagnetic activity; almost 24% were sensitive to relative air humidity, and about 16% of the women were to atmospheric pressure. The dynamics of systolic and diastolic BP in the annual cycle of women depends on meteorological factors and suggests that there is a change in the priorities of its control in different periods of a year.

Damage of plates due to impact, dynamic pressure and explosive loads

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Norman Jones

Full Text Available It is the purpose of this article to present design equations which can be used to predict the damage of ductile plating when subjected to mass impact, dynamic pressure or impulsive loadings. The external loadings are sufficiently severe to produce inelastic material behaviour and produce finite transverse displacement, or geometry change, effects. The damage is characterised as the final or permanent transverse displacement of a plate. The theoretical method predicts values for the maximum permanent transverse displacements which agree reasonably well with the corresponding experimental results generated on aluminium alloy circular, square and rectangular plates. Thus, the equations presented in this article are valuable for preliminary design purposes and for forensic studies, while the experimental data can be used for validating numerical schemes.

Measurement of dynamic urethral pressures with a high-resolution manometry system in continent and incontinent women.

Science.gov (United States)

Kirby, Anna C; Tan-Kim, Jasmine; Nager, Charles W

2015-01-01

Female stress urinary incontinence is caused by urethral dysfunction during dynamic conditions, but current technology has limitations in measuring urethral pressures under these conditions. An 8-French high-resolution manometry (HRM) catheter currently in clinical use in gastroenterology may accurately measure urethral pressures under dynamic conditions because it has a 25-millisecond response rate and circumferential pressure sensors along the length of the catheter (ManoScan ESO; Given Imaging, Yoqneam, Israel). We evaluated the concordance, repeatability, and tolerability of this catheter. We measured resting, cough, and strain maximum urethral closure pressures (MUCPs) using HRM and measured resting MUCPs with water-perfusion side-hole catheter urethral pressure profilometry (UPP) in 37 continent and 28 stress-incontinent subjects. Maneuvers were repeated after moving the HRM catheter along the urethral length to evaluate whether results depend on catheter positioning. Visual analog pain scores evaluated the comfort of HRM compared to UPP. The correlation coefficient for resting MUCPs measured by HRM versus UPP was high (r = 0.79, P rest, cough, and strain with HRM: r = 0.92, 0.89, and 0.89. Mean MUCPs (rest, cough, and strain) were higher in continent than in incontinent subjects (all P continent subjects during cough and strain maneuvers compared to rest. This preliminary study shows that HRM is concordant with standard technology, repeatable, and well tolerated in the urethra. Incontinent women have more impairment of their urethral closure pressures during cough and strain than continent women.

Dynamic performance of maximum power point tracking circuits using sinusoidal extremum seeking control for photovoltaic generation

Science.gov (United States)

Leyva, R.; Artillan, P.; Cabal, C.; Estibals, B.; Alonso, C.

2011-04-01

The article studies the dynamic performance of a family of maximum power point tracking circuits used for photovoltaic generation. It revisits the sinusoidal extremum seeking control (ESC) technique which can be considered as a particular subgroup of the Perturb and Observe algorithms. The sinusoidal ESC technique consists of adding a small sinusoidal disturbance to the input and processing the perturbed output to drive the operating point at its maximum. The output processing involves a synchronous multiplication and a filtering stage. The filter instance determines the dynamic performance of the MPPT based on sinusoidal ESC principle. The approach uses the well-known root-locus method to give insight about damping degree and settlement time of maximum-seeking waveforms. This article shows the transient waveforms in three different filter instances to illustrate the approach. Finally, an experimental prototype corroborates the dynamic analysis.

Porous media fracturing dynamics: stepwise crack advancement and fluid pressure oscillations

Science.gov (United States)

Cao, Toan D.; Hussain, Fazle; Schrefler, Bernhard A.

2018-02-01

We present new results explaining why fracturing in saturated porous media is not smooth and continuous but is a distinct stepwise process concomitant with fluid pressure oscillations. All exact solutions and almost all numerical models yield smooth fracture advancement and fluid pressure evolution, while recent experimental results, mainly from the oil industry, observation from geophysics and a very few numerical results for the quasi-static case indeed reveal the stepwise phenomenon. We summarize first these new experiments and these few numerical solutions for the quasi-static case. Both mechanical loading and pressure driven fractures are considered because their behaviours differ in the direction of the pressure jumps. Then we explore stepwise crack tip advancement and pressure fluctuations in dynamic fracturing with a hydro-mechanical model of porous media based on the Hybrid Mixture Theory. Full dynamic analyses of examples dealing with both hydraulic fracturing and mechanical loading are presented. The stepwise fracture advancement is confirmed in the dynamic setting as well as in the pressure fluctuations, but there are substantial differences in the frequency contents of the pressure waves in the two loading cases. Comparison between the quasi-static and fully dynamic solutions reveals that the dynamic response gives much more information such as the type of pressure oscillations and related frequencies and should be applied whenever there is a doubt about inertia forces playing a role - the case in most fracturing events. In the absence of direct relevant dynamic tests on saturated media some experimental results on dynamic fracture in dry materials, a fast hydraulic fracturing test and observations from geophysics confirm qualitatively the obtained results such as the type of pressure oscillations and the substantial difference in the behaviour under the two loading cases.

Study on Droplet Size and Velocity Distributions of a Pressure Swirl Atomizer Based on the Maximum Entropy Formalism

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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.

Relationship between maximum dynamic force of inferior members and body balance in strength training apprentices

Directory of Open Access Journals (Sweden)

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.

Quasi-dynamic pressure and temperature

International Nuclear Information System (INIS)

Zaug, J M.; Farber, D L; Blosch, L L; Craig, I M; Hansen, D W; Aracne-Ruddle, C M; Shuh, D K

1998-01-01

The phase transformation of(beta)-HMX ( and lt; 0.5% RDX) to the(delta) phase has been studied for over twenty years and more recently with an optically sensitive second harmonic generation technique. Shock studies of the plastic binder composites of HMX have indicated that the transition is perhaps irreversible, a result that concurs with the static pressure results published by F. Goetz et al.[l] in 1978. However the stability field favors the(beta) polymorph over(delta) as pressure is increased (up to 5.4 GPa) along any sensible isotherm. In this experiment strict control of pressure and temperature is maintained while x-ray and optical diagnostics are applied to monitor the conformational dynamics of HMX. Unlike the temperature induced(beta) - and gt;(delta) transition, the pressure induced is heterogeneous in nature. The room pressure and temperature(delta) - and gt;(beta) transition is not immediate although it seems to occur over tens of hours. Transition points and kinetics are path dependent and so this paper describes our work in progress

Patellofemoral Pressure Changes After Static and Dynamic Medial Patellofemoral Ligament Reconstructions.

Science.gov (United States)

Rood, Akkie; Hannink, Gerjon; Lenting, Anke; Groenen, Karlijn; Koëter, Sander; Verdonschot, Nico; van Kampen, Albert

2015-10-01

Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue fixation. Static MPFL reconstruction is most commonly used. However, dynamic reconstruction deforms more easily and presumably functions more like the native MPFL. The aim of the study was to evaluate the effect of the different MPFL fixation techniques on patellofemoral pressures compared with the native situation. The hypothesis was that dynamic reconstruction would result in patellofemoral pressures closer to those generated in an intact knee. Controlled laboratory study. Seven fresh-frozen knee specimens were tested in an in vitro knee joint loading apparatus. Tekscan pressure-sensitive films fixed to the retropatellar cartilage measured mean patellofemoral and peak pressures, contact area, and location of the center of force (COF) at fixed flexion angles from 0° to 110°. Four different conditions were tested: intact, dynamic, partial dynamic, and static MPFL reconstruction. Data were analyzed using linear mixed models. Static MPFL reconstruction resulted in higher peak and mean pressures from 60° to 110° of flexion (P .05). The COF in the static reconstruction group moved more medially on the patella from 50° to 110° of flexion compared with the other conditions. The contact area showed no significant differences between the test conditions. After static MPFL reconstruction, the patellofemoral pressures in flexion angles from 60° to 110° were 3 to 5 times higher than those in the intact situation. The pressures after dynamic MPFL reconstruction were similar as compared with those in the intact situation, and therefore, dynamic MPFL reconstruction could be a safer option than static reconstruction for stabilizing the patella. This study showed that static MPFL reconstruction

An overview of the dynamic calibration of piezoelectric pressure transducers

Science.gov (United States)

Theodoro, F. R. F.; Reis, M. L. C. C.; d’ Souto, C.

2018-03-01

Dynamic calibration is a research area that is still under development and is of great interest to aerospace and automotive industries. This study discusses some concepts regarding dynamic measurements of pressure quantities and presents an overview of dynamic calibration of pressure transducers. Studies conducted by the Institute of Aeronautics and Space focusing on research regarding piezoelectric pressure transducer calibration in shock tube are presented. We employed the Guide to the Expression of Uncertainty and a Monte Carlo Method in the methodology. The results show that both device and methodology employed are adequate to calibrate the piezoelectric sensor.

Dynamic tire pressure sensor for measuring ground vibration.

Science.gov (United States)

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.

The Influence of Pressure Distribution on the Maximum Values of Stress in FEM Analysis of Plain Bearings

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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.

Radiation pressure acceleration: The factors limiting maximum attainable ion energy

Energy Technology Data Exchange (ETDEWEB)

Bulanov, S. S.; Esarey, E.; Schroeder, C. B. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Bulanov, S. V. [KPSI, National Institutes for Quantum and Radiological Science and Technology, Kizugawa, Kyoto 619-0215 (Japan); A. M. Prokhorov Institute of General Physics RAS, Moscow 119991 (Russian Federation); Esirkepov, T. Zh.; Kando, M. [KPSI, National Institutes for Quantum and Radiological Science and Technology, Kizugawa, Kyoto 619-0215 (Japan); Pegoraro, F. [Physics Department, University of Pisa and Istituto Nazionale di Ottica, CNR, Pisa 56127 (Italy); Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Physics Department, University of California, Berkeley, California 94720 (United States)

2016-05-15

Radiation pressure acceleration (RPA) is a highly efficient mechanism of laser-driven ion acceleration, 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 transparent for radiation and effectively terminating the acceleration. The off-normal incidence of the laser on the target, due either to the experimental setup, or to the deformation of the target, will also lead to establishing a limit on maximum ion energy.

Pressure-modulation dynamic attenuated-total-reflectance (ATR) FT-IR spectroscopy

Science.gov (United States)

Marcott, C.; Story, G. M.; Noda, I.; Bibby, A.; Manning, C. J.

1998-06-01

A single-reflectance attenuated-total-reflectance (ATR) accessory with a diamond internal-reflection element was modified by the addition of a piezoelectric transducer. Initial dynamic pressure-modulation experiments have been performed in the sample compartment of a step-scanning FT-IR spectrometer. A sinusoidal pressure modulation applied to samples of isotactic polypropylene and linear low density polyethylene resulted in dynamic responses which appear to be similar to those observed in previous dynamic 2D IR experiments. Preliminary pressure-modulation dynamic ATR results are also reported for a styrene-butadiene-styrene triblock copolymer. The new method has the advantages that a much wider variety of sample types and geometries can be studied and less sample preparation is required. Dynamic 2D IR experiments carried out by ATR no longer require thin films of large area and sufficient strength to withstand the dynamic strain applied by a rheometer. The ability to obtain dynamic IR spectroscopic information from a wider variety of sample types and thicknesses would greatly expand the amount of useful information that could be extracted from normally complicated, highly overlapped IR spectra.

Critical Assessment of the Surface Tension determined by the Maximum Pressure Bubble Method

OpenAIRE

Benedetto, Franco Emmanuel; Zolotucho, Hector; Prado, Miguel Oscar

2015-01-01

The main factors that influence the value of surface tension of a liquid measured with the Maximum Pressure Bubble Method are critically evaluated. We present experimental results showing the effect of capillary diameter, capillary depth, bubble spheroidicity and liquid density at room temperature. We show that the decrease of bubble spheroidicity due to increase of capillary immersion depth is not sufficient to explain the deviations found in the measured surface tension values. Thus, we pro...

Ultrafast Dynamic Pressure Sensors Based on Graphene Hybrid Structure.

Science.gov (United States)

Liu, Shanbiao; Wu, Xing; Zhang, Dongdong; Guo, Congwei; Wang, Peng; Hu, Weida; Li, Xinming; Zhou, Xiaofeng; Xu, Hejun; Luo, Chen; Zhang, Jian; Chu, Junhao

2017-07-19

Mechanical flexible electronic skin has been focused on sensing various physical parameters, such as pressure and temperature. The studies of material design and array-accessible devices are the building blocks of strain sensors for subtle pressure sensing. Here, we report a new and facile preparation of a graphene hybrid structure with an ultrafast dynamic pressure response. Graphene oxide nanosheets are used as a surfactant to prevent graphene restacking in aqueous solution. This graphene hybrid structure exhibits a frequency-independent pressure resistive sensing property. Exceeding natural skin, such pressure sensors, can provide transient responses from static up to 10 000 Hz dynamic frequencies. Integrated by the controlling system, the array-accessible sensors can manipulate a robot arm and self-rectify the temperature of a heating blanket. This may pave a path toward the future application of graphene-based wearable electronics.

Temperature-insensitive fiber Bragg grating dynamic pressure sensing system.

Science.gov (United States)

Guo, Tuan; Zhao, Qida; Zhang, Hao; Zhang, Chunshu; Huang, Guiling; Xue, Lifang; Dong, Xiaoyi

2006-08-01

Temperature-insensitive dynamic pressure measurement using a single fiber Bragg grating (FBG) based on reflection spectrum bandwidth modulation and optical power detection is proposed. A specifically designed double-hole cantilever beam is used to provide a pressure-induced axial strain gradient along the sensing FBG and is also used to modulate the reflection bandwidth of the grating. The bandwidth modulation is immune to spatially uniform temperature effects, and the pressure can be unambiguously determined by measuring the reflected optical power, avoiding the complex wavelength interrogation system. The system acquisition time is up to 85 Hz for dynamic pressure measurement, and the thermal fluctuation is kept less than 1.2% full-scale for a temperature range of -10 degrees C to 80 degrees C.

Error Propagation Dynamics of PIV-based Pressure Field Calculations: How well does the pressure Poisson solver perform inherently?

Science.gov (United States)

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.

Error propagation dynamics of PIV-based pressure field calculations: How well does the pressure Poisson solver perform inherently?

International Nuclear Information System (INIS)

Pan, Zhao; Thomson, Scott; Whitehead, Jared; 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. (paper)

Error Propagation Dynamics of PIV-based Pressure Field Calculations: How well does the pressure Poisson solver perform inherently?

Science.gov (United States)

Pan, Zhao; Whitehead, Jared; 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. PMID:27499587

Dynamic fracture characterization of a pressure vessel steel

International Nuclear Information System (INIS)

Schmitt, W.; Boehme, W.; Klemm, W.; Memhard, D.; Winkler, S.

1991-01-01

Dynamic events are characterized by time and space-dependent stress and strain fields caused by wave or inertia effect. The dynamic effect at cracks may be originated from the rapid loading rate or impact loading of a structure containing a stationary crack or the time-dependent stress and strain fields of a propagating or arresting crack itself. Dynamic effects complicate the analysis of crack tip stress and strain fields, and usually considerable experimental effort and numerical technique are required. High loading rate influences the deformation and yield behavior and also the fracture toughness of materials. In order to know the propagation and arrest behavior of cracks, a heat of a German reactor pressure vessel steel was investigated, and the dynamic J-resistance curves were evaluated with large three-point bending specimens by impact loading, moreover, the crack propagation energy at large crack extension was determined with wide tension plates. The material tested was a ferritic pressure vessel steel, ASTM A 508 Cl 2. The dynamic J-resistance curves and numerical simulation and fractographic examination, and crack propagation energy are reported. (K.I.)

Pressure dependence of excited-state charge-carrier dynamics in organolead tribromide perovskites

Science.gov (United States)

Liu, X. C.; Han, J. H.; Zhao, H. F.; Yan, H. C.; Shi, Y.; Jin, M. X.; Liu, C. L.; Ding, D. J.

2018-05-01

Excited-state charge-carrier dynamics governs the performance of organometal trihalide perovskites (OTPs) and is strongly influenced by the crystal structure. Characterizing the excited-state charge-carrier dynamics in OTPs under high pressure is imperative for providing crucial insights into structure-property relations. Here, we conduct in situ high-pressure femtosecond transient absorption spectroscopy experiments to study the excited-state carrier dynamics of CH3NH3PbBr3 (MAPbBr3) under hydrostatic pressure. The results indicate that compression is an effective approach to modulate the carrier dynamics of MAPbBr3. Across each pressure-induced phase, carrier relaxation, phonon scattering, and Auger recombination present different pressure-dependent properties under compression. Responsiveness is attributed to the pressure-induced variation in the lattice structure, which also changes the electronic band structure. Specifically, simultaneous prolongation of carrier relaxation and Auger recombination is achieved in the ambient phase, which is very valuable for excess energy harvesting. Our discussion provides clues for optimizing the photovoltaic performance of OTPs.

Maximum Likelihood Dynamic Factor Modeling for Arbitrary "N" and "T" Using SEM

Science.gov (United States)

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…

Dynamics of explosively imploded pressurized tubes

Science.gov (United States)

Szirti, Daniel; Loiseau, Jason; Higgins, Andrew; Tanguay, Vincent

2011-04-01

The detonation of an explosive layer surrounding a pressurized thin-walled tube causes the formation of a virtual piston that drives a precursor shock wave ahead of the detonation, generating very high temperatures and pressures in the gas contained within the tube. Such a device can be used as the driver for a high energy density shock tube or hypervelocity gas gun. The dynamics of the precursor shock wave were investigated for different tube sizes and initial fill pressures. Shock velocity and standoff distance were found to decrease with increasing fill pressure, mainly due to radial expansion of the tube. Adding a tamper can reduce this effect, but may increase jetting. A simple analytical model based on acoustic wave interactions was developed to calculate pump tube expansion and the resulting effect on the shock velocity and standoff distance. Results from this model agree quite well with experimental data.

Influence of Dynamic Neuromuscular Stabilization Approach on Maximum Kayak Paddling Force

Directory of Open Access Journals (Sweden)

Davidek Pavel

2018-03-01

Full Text Available The purpose of this study was to examine the effect of Dynamic Neuromuscular Stabilization (DNS exercise on maximum paddling force (PF and self-reported pain perception in the shoulder girdle area in flatwater kayakers. Twenty male flatwater kayakers from a local club (age = 21.9 ± 2.4 years, body height = 185.1 ± 7.9 cm, body mass = 83.9 ± 9.1 kg were randomly assigned to the intervention or control groups. During the 6-week study, subjects from both groups performed standard off-season training. Additionally, the intervention group engaged in a DNS-based core stabilization exercise program (quadruped exercise, side sitting exercise, sitting exercise and squat exercise after each standard training session. Using a kayak ergometer, the maximum PF stroke was measured four times during the six weeks. All subjects completed the Disabilities of the Arm, Shoulder and Hand (DASH questionnaire before and after the 6-week interval to evaluate subjective pain perception in the shoulder girdle area. Initially, no significant differences in maximum PF and the DASH questionnaire were identified between the two groups. Repeated measures analysis of variance indicated that the experimental group improved significantly compared to the control group on maximum PF (p = .004; Cohen’s d = .85, but not on the DASH questionnaire score (p = .731 during the study. Integration of DNS with traditional flatwater kayak training may significantly increase maximum PF, but may not affect pain perception to the same extent.

Numerical estimates of the maximum sustainable pore pressure in anticline formations using the tensor based concept of pore pressure-stress coupling

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Andreas Eckert

2015-02-01

Full Text Available The advanced tensor based concept of pore pressure-stress coupling is used to provide pre-injection analytical estimates of the maximum sustainable pore pressure change, ΔPc, for fluid injection scenarios into generic anticline geometries. The heterogeneous stress distribution for different prevailing stress regimes in combination with the Young's modulus (E contrast between the injection layer and the cap rock and the interbedding friction coefficient, μ, may result in large spatial and directional differences of ΔPc. A single value characterizing the cap rock as for horizontal layered injection scenarios is not obtained. It is observed that a higher Young's modulus in the cap rock and/or a weak mechanical coupling between layers amplifies the maximum and minimum ΔPc values in the valley and limb, respectively. These differences in ΔPc imposed by E and μ are further amplified by different stress regimes. The more compressional the stress regime is, the larger the differences between the maximum and minimum ΔPc values become. The results of this study show that, in general compressional stress regimes yield the largest magnitudes of ΔPc and extensional stress regimes provide the lowest values of ΔPc for anticline formations. Yet this conclusion has to be considered with care when folded anticline layers are characterized by flexural slip and the friction coefficient between layers is low, i.e. μ = 0.1. For such cases of weak mechanical coupling, ΔPc magnitudes may range from 0 MPa to 27 MPa, indicating imminent risk of fault reactivation in the cap rock.

Vortex, ULF wave and Aurora Observation after Solar Wind Dynamic Pressure Change

Science.gov (United States)

Shi, Q.

2017-12-01

Here we will summarize our recent study and show some new results on the Magnetosphere and Ionosphere Response to Dynamic Pressure Change/disturbances in the Solar Wind and foreshock regions. We study the step function type solar wind dynamic pressure change (increase/decrease) interaction with the magnetosphere using THEMIS satellites at both dayside and nightside in different geocentric distances. Vortices generated by the dynamic pressure change passing along the magnetopause are found and compared with model predictions. ULF waves and vortices are excited in the dayside and nightside plasma sheet when dynamic pressure change hit the magnetotail. The related ionospheric responses, such as aurora and TCVs, are also investigated. We compare Global MHD simulations with the observations. We will also show some new results that dayside magnetospheric FLRs might be caused by foreshock structures.Shi, Q. Q. et al. (2013), THEMIS observations of ULF wave excitation in the nightside plasma sheet during sudden impulse events, J. Geophys. Res. Space Physics, 118, doi:10.1029/2012JA017984. Shi, Q. Q. et al. (2014), Solar wind pressure pulse-driven magnetospheric vortices and their global consequences, J. Geophys. Res. Space Physics, 119, doi:10.1002/2013JA019551. Tian, A.M. et al.(2016), Dayside magnetospheric and ionospheric responses to solar wind pressure increase: Multispacecraft and ground observations, J. Geophys. Res., 121, doi:10.1002/2016JA022459. Shen, X.C. et al.(2015), Magnetospheric ULF waves with increasing amplitude related to solar wind dynamic pressure changes: THEMIS observations, J. Geophys. Res., 120, doi:10.1002/2014JA020913Zhao, H. Y. et al. (2016), Magnetospheric vortices and their global effect after a solar wind dynamic pressure decrease, J. Geophys. Res. Space Physics, 121, doi:10.1002/2015JA021646. Shen, X. C., et al. (2017), Dayside magnetospheric ULF wave frequency modulated by a solar wind dynamic pressure negative impulse, J. Geophys. Res

Measurement of in-bore side loads and comparison to first maximum yaw

Directory of Open Access Journals (Sweden)

Donald E. Carlucci

2016-04-01

Full Text Available In-bore yaw of a projectile in a gun tube has been shown to result in range loss if the yaw is significant. An attempt was made to determine if relationships between in-bore yaw and projectile First Maximum Yaw (FMY were observable. Experiments were conducted in which pressure transducers were mounted near the muzzle of a 155 mm cannon in three sets of four. Each set formed a cruciform pattern to obtain a differential pressure across the projectile. These data were then integrated to form a picture of what the overall pressure distribution was along the side of the projectile. The pressure distribution was used to determine a magnitude and direction of the overturning moment acting on the projectile. This moment and its resulting angular acceleration were then compared to the actual first maximum yaw observed in the test. The degree of correlation was examined using various statistical techniques. Overall uncertainty in the projectile dynamics was between 20% and 40% of the mean values of FMY.

PPOOLEX experiments on dynamic loading with pressure feedback

International Nuclear Information System (INIS)

Puustinen, M.; Laine, J.; Raesaenen, A.

2011-01-01

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

Energy Technology Data Exchange (ETDEWEB)

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

Maximum magnitude of injection-induced earthquakes: A criterion to assess the influence of pressure migration along faults

Science.gov (United States)

Norbeck, Jack H.; Horne, Roland N.

2018-05-01

The maximum expected earthquake magnitude is an important parameter in seismic hazard and risk analysis because of its strong influence on ground motion. In the context of injection-induced seismicity, the processes that control how large an earthquake will grow may be influenced by operational factors under engineering control as well as natural tectonic factors. Determining the relative influence of these effects on maximum magnitude will impact the design and implementation of induced seismicity management strategies. In this work, we apply a numerical model that considers the coupled interactions of fluid flow in faulted porous media and quasidynamic elasticity to investigate the earthquake nucleation, rupture, and arrest processes for cases of induced seismicity. We find that under certain conditions, earthquake ruptures are confined to a pressurized region along the fault with a length-scale that is set by injection operations. However, earthquakes are sometimes able to propagate as sustained ruptures outside of the zone that experienced a pressure perturbation. We propose a faulting criterion that depends primarily on the state of stress and the earthquake stress drop to characterize the transition between pressure-constrained and runaway rupture behavior.

Dynamics of inner ear pressure change caused by intracranial pressure manipulation in the guinea pig

NARCIS (Netherlands)

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

AUTOMATIC DETECTION ALGORITHM OF DYNAMIC PRESSURE PULSES IN THE SOLAR WIND

International Nuclear Information System (INIS)

Zuo, Pingbing; Feng, Xueshang; Wang, Yi; Xie, Yanqiong; Li, Huijun; Xu, Xiaojun

2015-01-01

Dynamic pressure pulses (DPPs) in the solar wind are a significant phenomenon closely related to the solar-terrestrial connection and physical processes of solar wind dynamics. In order to automatically identify DPPs from solar wind measurements, we develop a procedure with a three-step detection algorithm that is able to rapidly select DPPs from the plasma data stream and simultaneously define the transition region where large dynamic pressure variations occur and demarcate the upstream and downstream region by selecting the relatively quiet status before and after the abrupt change in dynamic pressure. To demonstrate the usefulness, efficiency, and accuracy of this procedure, we have applied it to the Wind observations from 1996 to 2008 by successfully obtaining the DPPs. The procedure can also be applied to other solar wind spacecraft observation data sets with different time resolutions

Pressure-based high-order TVD methodology for dynamic stall control

Science.gov (United States)

Yang, H. Q.; Przekwas, A. J.

1992-01-01

The quantitative prediction of the dynamics of separating unsteady flows, such as dynamic stall, is of crucial importance. This six-month SBIR Phase 1 study has developed several new pressure-based methodologies for solving 3D Navier-Stokes equations in both stationary and moving (body-comforting) coordinates. The present pressure-based algorithm is equally efficient for low speed incompressible flows and high speed compressible flows. The discretization of convective terms by the presently developed high-order TVD schemes requires no artificial dissipation and can properly resolve the concentrated vortices in the wing-body with minimum numerical diffusion. It is demonstrated that the proposed Newton's iteration technique not only increases the convergence rate but also strongly couples the iteration between pressure and velocities. The proposed hyperbolization of the pressure correction equation is shown to increase the solver's efficiency. The above proposed methodologies were implemented in an existing CFD code, REFLEQS. The modified code was used to simulate both static and dynamic stalls on two- and three-dimensional wing-body configurations. Three-dimensional effect and flow physics are discussed.

Experimental research on dynamic mechanical properties of PZT ceramic under hydrostatic pressure

International Nuclear Information System (INIS)

Wang, S.; Liu, K.X.

2011-01-01

Highlights: → We developed an experimental device to examine dynamic mechanical properties of PZT. → Ductile behavior of PZT was seen when hydrostatic pressure was involved. → Compressive strength was shown sensitive to hydrostatic pressure and strain-rate. → A failure criterion was suggested to explain the failure behavior of PZT. - Abstract: An experimental technique for initially applied hydrostatic pressure in specimens subjected to axial impact has been developed to study the dynamic mechanical properties of materials. The technique was employed for the purpose of examining the dynamic mechanical properties of lead zirconate titanate (PZT) at zero to 15 MPa hydrostatic pressures. Experimental results unambiguously exhibit the ductile behavior of PZT when hydrostatic pressure is involved. The compressive strength is demonstrated sensitive to the initial hydrostatic pressure and the strain-rate. The fracture modes are analyzed by means of scanning electron microscopy (SEM). Moreover, a failure criterion based on Mohr-Coulomb failure theory is suggested to explain the brittle and ductile failure of PZT.

Variation of Pore Water Pressure in Tailing Sand under Dynamic Loading

Directory of Open Access Journals (Sweden)

Jia-xu Jin

2018-01-01

Full Text Available Intense vibration affects the pore water pressure in a tailing dam, with the tendency to induce dam liquefaction. In this study, experiments were performed wherein model tailing dams were completely liquefied by sustained horizontal dynamic loading to determine the effects of the vibration frequency, vibration amplitude, and tailing density on the pore water pressure. The results revealed four stages in the increase of the tailing pore water pressure under dynamic loading, namely, a slow increase, a rapid increase, inducement of structural failure, and inducement of complete liquefaction. A lower frequency and smaller amplitude of the vibration were found to increase the time required to achieve a given pore water pressure in dense tailings. Under the effect of these three factors—vibration frequency and amplitude and tailing density—the tailing liquefaction time varied nonlinearly with the height from the base of the tailing dam, with an initial decrease followed by an increase. The pore pressure that induced structural failure also gradually decreased with increasing height. The increase in the tailing pore pressure could be described by an S-shaped model. A complementary multivariate nonlinear equation was also derived for predicting the tailing pore water pressure under dynamic loading.

Dynamic Programming and Error Estimates for Stochastic Control Problems with Maximum Cost

International Nuclear Information System (INIS)

Bokanowski, Olivier; Picarelli, Athena; Zidani, Hasnaa

2015-01-01

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

Dynamic Programming and Error Estimates for Stochastic Control Problems with Maximum Cost

Energy Technology Data Exchange (ETDEWEB)

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.

Transient electromagnetic and dynamic structural analyses of a blanket structure with coupling effects

Energy Technology Data Exchange (ETDEWEB)

Koganezawa, K. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Kushiyama, M. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Niikura, S. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Kudough, F. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Onozuka, M. [Mitsubishi Heavy Industries Ltd., Yokohama (Japan); Koizumi, K. [Japan Atomic Energy Research Inst., Ibaraki (Japan)

1995-12-31

Transient electromagnetic and dynamic structural analyses of a blanket structure in the fusion experimental reactor (FER) under a plasma disruption event and a vertical displacement event (VDE) have been performed to investigate the dynamic structural characteristics and the feasibility of the structure. Coupling effects between eddy currents and dynamic deflections have also been taken into account in these analyses. In this study, the inboard blanket was employed because of our computer memory limitation. A 1/192 segment model of a full torus was analyzed using the analytical code, EDDYCUFF. In the plasma disruption event, the maximum magnetic pressure caused by eddy currents and poloidal fields was 1.2MPa. The maximum stress intensity by this magnetic pressure was 114MPa. In the VDE, the maximum magnetic pressure was 2.4MPa and the maximum stress intensity was 253MPa. This stress was somewhat beyond the allowable stress limit. Therefore, the blanket structure and support design should be reviewed to reduce the stress to a suitable value. In summary, the dynamic structural characteristics and design issues of the blanket structure have been identified. (orig.).

High Temperature Dynamic Pressure Measurements Using Silicon Carbide Pressure Sensors

Science.gov (United States)

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.

Communication: Dynamical and structural analyses of solid hydrogen under vapor pressure

Energy Technology Data Exchange (ETDEWEB)

Hyeon-Deuk, Kim, E-mail: kim@kuchem.kyoto-u.ac.jp [Department of Chemistry, Kyoto University, Kyoto 606-8502 (Japan); Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Ando, Koji [Department of Chemistry, Kyoto University, Kyoto 606-8502 (Japan)

2015-11-07

Nuclear quantum effects play a dominant role in determining the phase diagram of H{sub 2}. With a recently developed quantum molecular dynamics simulation method, we examine dynamical and structural characters of solid H{sub 2} under vapor pressure, demonstrating the difference from liquid and high-pressure solid H{sub 2}. While stable hexagonal close-packed lattice structures are reproduced with reasonable lattice phonon frequencies, the most stable adjacent configuration exhibits a zigzag structure, in contrast with the T-shape liquid configuration. The periodic angular distributions of H{sub 2} molecules indicate that molecules are not a completely free rotor in the vapor-pressure solid reflecting asymmetric potentials from surrounding molecules on adjacent lattice sites. Discrete jumps of librational and H–H vibrational frequencies as well as H–H bond length caused by structural rearrangements under vapor pressure effectively discriminate the liquid and solid phases. The obtained dynamical and structural information of the vapor-pressure H{sub 2} solid will be useful in monitoring thermodynamic states of condensed hydrogens.

Dynamic analysis of solid propellant grains subjected to ignition pressurization loading

Science.gov (United States)

Chyuan, Shiang-Woei

2003-11-01

Traditionally, the transient analysis of solid propellant grains subjected to ignition pressurization loading was not considered, and quasi-elastic-static analysis was widely adopted for structural integrity because the analytical task gets simplified. But it does not mean that the dynamic effect is not useful and could be neglected arbitrarily, and this effect usually plays a very important role for some critical design. In order to simulate the dynamic response for solid rocket motor, a transient finite element model, accompanied by concepts of time-temperature shift principle, reduced integration and thermorheologically simple material assumption, was used. For studying the dynamic response, diverse ignition pressurization loading cases were used and investigated in the present paper. Results show that the dynamic effect is important for structural integrity of solid propellant grains under ignition pressurization loading. Comparing the effective stress of transient analysis and of quasi-elastic-static analysis, one can see that there is an obvious difference between them because of the dynamic effect. From the work of quasi-elastic-static and transient analyses, the dynamic analysis highlighted several areas of interest and a more accurate and reasonable result could be obtained for the engineer.

Dynamic stall characterization using modal analysis of phase-averaged pressure distributions

Science.gov (United States)

Harms, Tanner; Nikoueeyan, Pourya; Naughton, Jonathan

2017-11-01

Dynamic stall characterization by means of surface pressure measurements can simplify the time and cost associated with experimental investigation of unsteady airfoil aerodynamics. A unique test capability has been developed at University of Wyoming over the past few years that allows for time and cost efficient measurement of dynamic stall. A variety of rotorcraft and wind turbine airfoils have been tested under a variety of pitch oscillation conditions resulting in a range of dynamic stall behavior. Formation, development and separation of different flow structures are responsible for the complex aerodynamic loading behavior experienced during dynamic stall. These structures have unique signatures on the pressure distribution over the airfoil. This work investigates the statistical behavior of phase-averaged pressure distribution for different types of dynamic stall by means of modal analysis. The use of different modes to identify specific flow structures is being investigated. The use of these modes for different types of dynamic stall can provide a new approach for understanding and categorizing these flows. This work uses airfoil data acquired under Army contract W911W60160C-0021, DOE Grant DE-SC0001261, and a gift from BP Alternative Energy North America, Inc.

Determination of the optimum pressure for neutron yield with d2, in the PF facility dena

International Nuclear Information System (INIS)

Siahpoush, V.; Khorram, C.; Sobhanian, S.; Hamzeh Fafreshi, M. A.

2003-01-01

Using physical model, which describes the dynamics of plasma in the Filipov type plasma focus, we have simulated the pinch current for different voltages and pressures. The results show that for a specific voltage, there is an optimum pressure for which the pinch current has maximum value. A comparison between the simulated and the experimental data from dena shows that the maximum values of pinch current are obtained at the same pressure for which the maximum neutron yield is observed

Computational Fluid Dynamics Analysis of High Injection Pressure Blended Biodiesel

Science.gov (United States)

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.

The dynamic pressure measurements of the nuclear reactor coolant for condition-based maintenance of the reactor

International Nuclear Information System (INIS)

Es-Saheb, M.H.H.

1990-01-01

The condition-based maintenance of the nuclear reactor, by monitoring and measuring the instantaneous dynamic pressure distribution of the coolant (water) impact on the solid surfaces of the reactor during operation is presented. The behaviour of water domes (jets) produced by underwater explosions of small changes of P.E.T.N. at various depths in two different size cylindrical containers, which simulate the nuclear reactor, is investigated. Water surface domes (jets) from the underwater explosions are photographed. Depending on the depth of the charge, curved and flat top jets of up to 455 mm diameter and impact speeds of up to 70 m/sec. are observed. The instabilities in the dome surfaces are observed and the instantaneous profiles are analysed. It is found that, in all cases tested, the maximum pressure takes place at the center of the jet and could reach up to 3.0 times the on-dimensional impact pressure value. The use of their measurements, as online monitoring for condition-based maintenance and design-out maintenance is discussed. 18 refs

Maximum Entropy Approach in Dynamic Contrast-Enhanced Magnetic Resonance Imaging.

Science.gov (United States)

Farsani, Zahra Amini; Schmid, Volker J

2017-01-01

In the estimation of physiological kinetic parameters from Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) data, the determination of the arterial input function (AIF) plays a key role. This paper proposes a Bayesian method to estimate the physiological parameters of DCE-MRI along with the AIF in situations, where no measurement of the AIF is available. In the proposed algorithm, the maximum entropy method (MEM) is combined with the maximum a posterior approach (MAP). To this end, MEM is used to specify a prior probability distribution of the unknown AIF. The ability of this method to estimate the AIF is validated using the Kullback-Leibler divergence. Subsequently, the kinetic parameters can be estimated with MAP. The proposed algorithm is evaluated with a data set from a breast cancer MRI study. The application shows that the AIF can reliably be determined from the DCE-MRI data using MEM. Kinetic parameters can be estimated subsequently. The maximum entropy method is a powerful tool to reconstructing images from many types of data. This method is useful for generating the probability distribution based on given information. The proposed method gives an alternative way to assess the input function from the existing data. The proposed method allows a good fit of the data and therefore a better estimation of the kinetic parameters. In the end, this allows for a more reliable use of DCE-MRI. Schattauer GmbH.

Design Considerations for Remote High-Speed Pressure Measurements of Dynamic Combustion Phenomena

Energy Technology Data Exchange (ETDEWEB)

Straub, D.L.; Ferguson, D.H.; Rohrssen, Robert (West Virginia University, Morgantown, WV); Perez, Eduardo (West Virginia University, Morgantown, WV)

2007-01-01

As gas turbine combustion systems evolve to achieve ultra-low emission targets, monitoring and controlling dynamic combustion processes becomes increasingly important. These dynamic processes may include flame extinction, combustion-driven instabilities, or other dynamic combustion phenomena. Pressure sensors can be incorporated into the combustor liner design, but this approach is complicated by the harsh operating environment. One practical solution involves locating the sensor in a more remote location, such as outside the pressure casing. The sensor can be connected to the measurement point by small diameter tubing. Although this is a practical approach, the dynamics of the tubing can introduce significant errors into the pressure measurement. This paper addresses measurement errors associated with semi-infinite coil remote sensing setups and proposes an approach to improve the accuracy of these types of measurements.

Solar wind dynamic pressure variations and transient magnetospheric signatures

International Nuclear Information System (INIS)

Sibeck, D.G.; Baumjohann, W.

1989-01-01

Contrary to the prevailing popular view, we find some transient ground events with bipolar north-south signatures are related to variations in solar wind dynamic pressure and not necessarily to magnetic merging. We present simultaneous solar wind plasma observations for two previously reported transient ground events observed at dayside auroral latitudes. During the first event, originally reported by Lanzerotti et al. [1987], conjugate ground magnetometers recorded north-south magetic field deflections in the east-west and vertical directions. The second event was reported by Todd et al. [1986], we noted ground rader observations indicating strong northward then southward ionospheric flows. The events were associated with the postulated signatures of patchy, sporadic, merging of magnetosheath and magnetospheric magnetic field lines at the dayside magnetospause, known as flux transfer events. Conversely, we demonstrate that the event reported by Lanzerotti et al. was accompanied by a sharp increase in solar wind dynamic pressure, a magnetospheric compression, and a consequent ringing of the magnetospheric magnetic field. The event reported by Todd et al. was associated with a brief but sharp increase in the solar wind dynamic pressure. copyright American Geophysical Union 1989

Dynamic pressure sensor calibration techniques offering expanded bandwidth with increased resolution

Science.gov (United States)

Wisniewiski, David

2015-03-01

Advancements in the aerospace, defense and energy markets are being made possible by increasingly more sophisticated systems and sub-systems which rely upon critical information to be conveyed from the physical environment being monitored through ever more specialized, extreme environment sensing components. One sensing parameter of particular interest is dynamic pressure measurement. Crossing the boundary of all three markets (i.e. aerospace, defense and energy) is dynamic pressure sensing which is used in research and development of gas turbine technology, and subsequently embedded into a control loop used for long-term monitoring. Applications include quantifying the effects of aircraft boundary layer ingestion into the engine inlet to provide a reliable and robust design. Another application includes optimization of combustor dynamics by "listening" to the acoustic signature so that fuel-to-air mixture can be adjusted in real-time to provide cost operating efficiencies and reduced NOx emissions. With the vast majority of pressure sensors supplied today being calibrated either statically or "quasi" statically, the dynamic response characterization of the frequency dependent sensitivity (i.e. transfer function) of the pressure sensor is noticeably absent. The shock tube has been shown to be an efficient vehicle to provide frequency response of pressure sensors from extremely high frequencies down to 500 Hz. Recent development activity has lowered this starting frequency; thereby augmenting the calibration bandwidth with increased frequency resolution so that as the pressure sensor is used in an actual test application, more understanding of the physical measurement can be ascertained by the end-user.

Dynamic analysis of an axially moving beam subject to inner pressure using finite element method

Energy Technology Data Exchange (ETDEWEB)

Hua, Hongliang; Qiu, Ming; Liao, Zhenqiang [Nanjing University of Science and Technology, Nanjing (China)

2017-06-15

A dynamic model of an axially moving flexible beam subject to an inner pressure is present. The coupling principle between a flexible beam and inner pressure is analyzed first, and the potential energy of the inner pressure due to the beam bending is derived using the principle of virtual work. A 1D hollow beam element contain inner pressure is established. The finite element method and Lagrange’s equation are used to derive the motion equations of the axially moving system. The dynamic responses are analyzed by Newmark-β time integration method. Based on the computed dynamic responses, the effects of inner pressure on beam dynamics are discussed. Some interesting phenomenon is observed.

Aortic and peripheral blood pressure during isometric and dynamic exercise

NARCIS (Netherlands)

Blum, V.; Carrière, E.G.J.; Kolsters, W.; Mosterd, W.L.; Schiereck, P.; Wesseling, K.H.

1997-01-01

The purpose of this study was to compare aortic blood pressure (AOR) to peripheral measurements by the Riva-Rocci/Korotkov (RRK) and Finapres continuous finger pressure (FIN) methods during dynamic and static exercise. A tip manometer was introduced in the ascending aorta after coronary angiography

Statistical Characteristics of Solar Wind Dynamic Pressure Enhancements During Geomagnetic Storms

Directory of Open Access Journals (Sweden)

C.-R. Choi

2008-06-01

Full Text Available Solar wind dynamic pressure enhancements are known to cause various types of disturbances to the magnetosphere. In particular, dynamic pressure enhancements may affect the evolution of magnetic storms when they occur during storm times. In this paper, we have investigated the statistical significance and features of dynamic pressure enhancements during magnetic storm times. For the investigation, we have used a total of 91 geomagnetic storms for 2001-2003, for which the Dst minimum (Dst_min is below -50 nT. Also, we have imposed a set of selection criteria for a pressure enhancement to be considered an event: The main selection criterion is that the pressure increases by ≥50% or ≥3nPa within 30 min and remains to be elevated for 10 min or longer. For our statistical analysis, we define the storm time to be the interval from the main Dst decrease, through Dst_min, to the point where the Dst index recovers by 50%. Our main results are summarized as follows. (i ~81% of the studied storms indicate at least one event of pressure enhancements. When averaged over all the 91 storms, the occurrence rate is 4.5 pressure enhancement events per storm and 0.15 pressure enhancement events per hour. (ii The occurrence rate of the pressure enhancements is about three times higher for CME-driven storm times than for CIR-driven storm times. (iii Only 21.1% of the pressure enhancements show a clear association with an interplanetary shock. (iv A large number of the pressure enhancement events are accompanied with a simultaneous change of IMF By and/or Bz: For example, 73.5% of the pressure enhancement events are associated with an IMF change of either |∆Bz|>2nT or |∆By|>2nT. This last finding suggests that one should consider possible interplay effects between the simultaneous pressure and IMF changes in many situations.

Maximum Expected Wall Heat Flux and Maximum Pressure After Sudden Loss of Vacuum Insulation on the Stratospheric Observatory for Infrared Astronomy (SOFIA) Liquid Helium (LHe) Dewars

Science.gov (United States)

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.

Integration of piezo-capacitive and piezo-electric nanoweb based pressure sensors for imaging of static and dynamic pressure distribution.

Science.gov (United States)

Jeong, Y J; Oh, T I; Woo, E J; Kim, K J

2017-07-01

Recently, highly flexible and soft pressure distribution imaging sensor is in great demand for tactile sensing, gait analysis, ubiquitous life-care based on activity recognition, and therapeutics. In this study, we integrate the piezo-capacitive and piezo-electric nanowebs with the conductive fabric sheets for detecting static and dynamic pressure distributions on a large sensing area. Electrical impedance tomography (EIT) and electric source imaging are applied for reconstructing pressure distribution images from measured current-voltage data on the boundary of the hybrid fabric sensor. We evaluated the piezo-capacitive nanoweb sensor, piezo-electric nanoweb sensor, and hybrid fabric sensor. The results show the feasibility of static and dynamic pressure distribution imaging from the boundary measurements of the fabric sensors.

Dynamic analysis of crack growth and arrest in a pressure vessel subjected to thermal and pressure loading

International Nuclear Information System (INIS)

Brickstad, B.

1984-01-01

Predictions of crack arrest behaviour are performed for a cracked reactor pressure vessel under both thermal and pressure loading. The object is to compare static and dynamic calculations. The dynamic calculations are made using an explicit finite element technique where crack growth is simulated by gradual nodal release. Three different load cases and the effect of different velocity dependence on the crack propagation toughness are studied. It is found that for the analysed cases the static analysis is slightly conservative, thus justifying its use for these problems. (orig.)

Combustion characteristics and kinetic analysis of pulverized coal under different pressure grades

Directory of Open Access Journals (Sweden)

Qiwei ZUO

2016-02-01

Full Text Available By using thermo gravimetric balance, experimental research on combustion characteristics and dynamics parameters of the typical coal injection from some domestic steelworks are conducted with non-isothermal method. The combustion characteristic parameters of the sample pulverized coal such as ignition temperature, peak temperature at maximum weight loss rate, burnout temperature, general burn exponent(S, and maximum combustion rate are studied under pressure grades of 0.1, 1.1, 2.1, 3.1 and 4.1 MPa, the activation energy (E and pre-exponential factor in the combustion process are calculated. The results show that when the pressure increases from 0.1 to 4.1 MPa, ignition temperature decreases by 85.7 K at most, peak temperature at maximum weight loss rate decreases by 249.3 K at most, burnout temperature decreases by 375 K at most, maximum weight loss rate increases by 10 times, and S increases by 33.6 times at most. It is also shown that there exists a kinetic complementation between E and ln A from the view point of dynamics, and the critical pressure of pulverized coal reaction control requirement and combustion mode transform is 3.1 MPa for the pulverized coal.

Structure and dynamics of water confined in a graphene nanochannel under gigapascal high pressure: dependence of friction on pressure and confinement.

Science.gov (United States)

Yang, Lei; Guo, Yanjie; Diao, Dongfeng

2017-05-31

Recently, water flow confined in nanochannels has become an interesting topic due to its unique properties and potential applications in nanofluidic devices. The trapped water is predicted to experience high pressure in the gigapascal regime. Theoretical and experimental studies have reported various novel structures of the confined water under high pressure. However, the role of this high pressure on the dynamic properties of water has not been elucidated to date. In the present study, the structure evolution and interfacial friction behavior of water constrained in a graphene nanochannel were investigated via molecular dynamics simulations. Transitions of the confined water to different ice phases at room temperature were observed in the presence of lateral pressure at the gigapascal level. The friction coefficient at the water/graphene interface was found to be dependent on the lateral pressure and nanochannel height. Further theoretical analyses indicate that the pressure dependence of friction is related to the pressure-induced change in the structure of water and the confinement dependence results from the variation in the water/graphene interaction energy barrier. These findings provide a basic understanding of the dynamics of the nanoconfined water, which is crucial in both fundamental and applied science.

Effects of Abrupt Variations of Solar Wind Dynamic Pressure on the High-Latitude Ionosphere

Directory of Open Access Journals (Sweden)

Igino Coco

2011-01-01

Full Text Available We show the results of a statistical study on the effects in the high-latitude ionosphere of abrupt variations of solar wind dynamic pressure, using Super Dual Auroral Radar Network (SuperDARN data in both hemispheres. We find that, during periods of quiet ionospheric conditions, the amount of radar backscatter increases when a variation in the dynamic pressure occurs, both positive (increase of the pressure and negative (decrease of the pressure. We also investigate the behaviour of the Cross-Polar Cap Potential (CPCP during pressure variations and show preliminary results.

Fracture dynamics of a propagating crack in a pressurized ductile cylinder

International Nuclear Information System (INIS)

Emery, A.F.; Love, W.J.; Kobayashi, A.S.

1977-01-01

A suddenly-introduced axial through-crack in the wall of a pipe pressurized by hot water is allowed to propagate according to Weiss' notch-strength theory of ductile static fracture. For this somewhat ductile material of A533B steel, Weiss' criterion was extended of dynamic fracture without modification. This dynamic-fracture criterion enabled a unique comparison to be obtained for the results of ductile-fracture with those of brittle-fracture in a fracturing A533B steel pipe. Since the pipe cross-sectional area is likely to increase with large flap motions under ductile tearing, a large deformation-shell-finite-difference-dynamic-code which includes rotary inertia was used in this analysis. The uniaxial-stress-strain curve of A533B steel was approximated by a bilinear stress-strain where Von-Misses yield criterion and associated flow rule were used in the elastic-plastic analysis. The fluid pressure was assumed constant and thus pipe flaps are only lightly loaded by pressure in this analysis. In previous publications, the authors have compared their preliminary results for the shell motion obtained through their model for a fracturing pipe with those of Kanninen, et al., and Freund, et al., to evaluate the effects of pressure loading on the crack flaps and the differences between small and large deflection results. In this paper, the differences in crack-propagation behavior of a fracturing pipe composed of the same A533B but subjected to a brittle or a ductile-fracture criterion are discussed. An important conclusion in fracture dynamics derived from analyses is that a smoothly-varying crack velocity will require a non-unique crack-velocity-versus-dynamic-fracture-parameter-relation while a unique and smoothly-varying crack-velocity-versus-dynamic-fracture-parameter-relation will demand an intermittently-propagating crack

High protein flexibility and reduced hydration water dynamics are key pressure adaptive strategies in prokaryotes

KAUST Repository

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.

High protein flexibility and reduced hydration water dynamics are key pressure adaptive strategies in prokaryotes

KAUST Repository

Martinez, N.; Michoud, Gregoire; Cario, A.; Ollivier, J.; Franzetti, B.; Jebbar, M.; Oger, P.; Peters, J.

2016-01-01

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.

Optimization study of pressure-swing distillation for the separation process of a maximum-boiling azeotropic system of water-ethylenediamine

Energy Technology Data Exchange (ETDEWEB)

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.

Optimization study of pressure-swing distillation for the separation process of a maximum-boiling azeotropic system of water-ethylenediamine

International Nuclear Information System (INIS)

Fulgueras, Alyssa Marie; Poudel, Jeeban; Kim, Dong Sun; Cho, Jungho

2016-01-01

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.

In-shoe plantar tri-axial stress profiles during maximum-effort cutting maneuvers.

Science.gov (United States)

Cong, Yan; Lam, Wing Kai; Cheung, Jason Tak-Man; Zhang, Ming

2014-12-18

Soft tissue injuries, such as anterior cruciate ligament rupture, ankle sprain and foot skin problems, frequently occur during cutting maneuvers. These injuries are often regarded as associated with abnormal joint torque and interfacial friction caused by excessive external and in-shoe shear forces. This study simultaneously investigated the dynamic in-shoe localized plantar pressure and shear stress during lateral shuffling and 45° sidestep cutting maneuvers. Tri-axial force transducers were affixed at the first and second metatarsal heads, lateral forefoot, and heel regions in the midsole of a basketball shoe. Seventeen basketball players executed both cutting maneuvers with maximum efforts. Lateral shuffling cutting had a larger mediolateral braking force than 45° sidestep cutting. This large braking force was concentrated at the first metatarsal head, as indicated by its maximum medial shear stress (312.2 ± 157.0 kPa). During propulsion phase, peak shear stress occurred at the second metatarsal head (271.3 ± 124.3 kPa). Compared with lateral shuffling cutting, 45° sidestep cutting produced larger peak propulsion shear stress (463.0 ± 272.6 kPa) but smaller peak braking shear stress (184.8 ± 181.7 kPa), of which both were found at the first metatarsal head. During both cutting maneuvers, maximum medial and posterior shear stress occurred at the first metatarsal head, whereas maximum pressure occurred at the second metatarsal head. The first and second metatarsal heads sustained relatively high pressure and shear stress and were expected to be susceptible to plantar tissue discomfort or injury. Due to different stress distribution, distinct pressure and shear cushioning mechanisms in basketball footwear might be considered over different foot regions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Chaotic dynamic characteristics of pressure fluctuation signals in hydro-turbine

Energy Technology Data Exchange (ETDEWEB)

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.

High-frequency dynamics of the glass former dibutylphthalate under pressure

International Nuclear Information System (INIS)

Mermet, A.; Krisch, M.; Duval, E.; Polian, A.

2002-01-01

The high-frequency dynamics of a fragile molecular glass former (dibutylphthalate) was studied through inelastic x-ray scattering (IXS), as a function of pressure and temperature. The mesoscopic structural arrest associated with the glass transition process was tracked by following upon cooling the inelastic excitations at fixed Q points in the dispersion curves, at ambient pressure and 2 kbar. The application of pressure to this system induces an offset between the macroscopic glass transition temperature T g and the mesoscopic glass transition temperature, as determined from IXS. The concomitant fragility decrease of dibutylphthalate under pressure unveils that the stronger the glass former is, the more its mesoscopic dynamics differ from the macroscopic regime. This trend is interpreted as the signature of a nanoscopic inhomogeneous elastic network. Further aspects of this system are obtained when studying the temperature dependence of its nonergodicity factor f Q (T). The chemical specificity of the molecule is suggested to be responsible for the nonobservation of a critical temperature T c in dibutylphthalate up to ∼300 K

Implications of Dynamic Pressure Transducer Mounting Variations on Measurements in Pyrotechnic Test Apparatus

Science.gov (United States)

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.

Fluid-structure interaction dynamic simulation of spring-loaded pressure relief valves under seismic wave

Science.gov (United States)

Lv, Dongwei; Zhang, Jian; Yu, Xinhai

2018-05-01

In this paper, a fluid-structure interaction dynamic simulation method of spring-loaded pressure relief valve was established. The dynamic performances of the fluid regions and the stress and strain of the structure regions were calculated at the same time by accurately setting up the contact pairs between the solid parts and the coupling surfaces between the fluid regions and the structure regions. A two way fluid-structure interaction dynamic simulation of a simplified pressure relief valve model was carried out. The influence of vertical sinusoidal seismic waves on the performance of the pressure relief valve was preliminarily investigated by loading sine waves. Under vertical seismic waves, the pressure relief valve will flutter, and the reseating pressure was affected by the amplitude and frequency of the seismic waves. This simulation method of the pressure relief valve under vertical seismic waves can provide effective means for investigating the seismic performances of the valves, and make up for the shortcomings of the experiment.

Nonstationary pressure build up in full-pressure containments after a loss-of-coolant accident

International Nuclear Information System (INIS)

Mansfeld, G.

1977-01-01

The time histories of pressure, temperature and pressure difference during the pressure build up phase of a loss-of-coolant accident (LOCA) in the primary system in full-pressure containments of water cooled nuclear power reactors are treated. These are important for the design of such containments. The experiments within the German research program RS 50 ''Druckverteilung im Containment'' offered, for the first time, the opportunity to observe experimentally fluid-dynamic processes in a multiple divided full-pressure containment, and to test at the same time, computer codes which serve to describe the physical processes during the LOCA. The comparison of the results calculated by the computer codes ZOCO VI and DDIFF with the experimental results showed apparent deviations by special arrangements of the compartments and the vent flow paths of a model containment for the calculation of time dependent pressure-, temperature- and pressure difference-histories. The deviations lead to the development of the analytical model and computer code COFLOW. This new model was primarily designed to deal with the fluid-dynamic processes in the beginning phase of the blowdown as maximal pressure differences appear. Furthermore, it can be used to determine the maximum containment pressure, as well as for long term calculations. The analytical model and computer code COFLOW shows a better correlation between theory and experiment than previous codes

Dynamic modeling method of the bolted joint with uneven distribution of joint surface pressure

Science.gov (United States)

Li, Shichao; Gao, Hongli; Liu, Qi; Liu, Bokai

2018-03-01

The dynamic characteristics of the bolted joints have a significant influence on the dynamic characteristics of the machine tool. Therefore, establishing a reasonable bolted joint dynamics model is helpful to improve the accuracy of machine tool dynamics model. Because the pressure distribution on the joint surface is uneven under the concentrated force of bolts, a dynamic modeling method based on the uneven pressure distribution of the joint surface is presented in this paper to improve the dynamic modeling accuracy of the machine tool. The analytic formulas between the normal, tangential stiffness per unit area and the surface pressure on the joint surface can be deduced based on the Hertz contact theory, and the pressure distribution on the joint surface can be obtained by the finite element software. Futhermore, the normal and tangential stiffness distribution on the joint surface can be obtained by the analytic formula and the pressure distribution on the joint surface, and assigning it into the finite element model of the joint. Qualitatively compared the theoretical mode shapes and the experimental mode shapes, as well as quantitatively compared the theoretical modal frequencies and the experimental modal frequencies. The comparison results show that the relative error between the first four-order theoretical modal frequencies and the first four-order experimental modal frequencies is 0.2% to 4.2%. Besides, the first four-order theoretical mode shapes and the first four-order experimental mode shapes are similar and one-to-one correspondence. Therefore, the validity of the theoretical model is verified. The dynamic modeling method proposed in this paper can provide a theoretical basis for the accurate dynamic modeling of the bolted joint in machine tools.

Simplified Methodology to Estimate the Maximum Liquid Helium (LHe) Cryostat Pressure from a Vacuum Jacket Failure

Science.gov (United States)

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

Analytical solution for dynamic pressurization of viscoelastic fluids

International Nuclear Information System (INIS)

Hashemabadi, S.H.; Etemad, S.Gh.; Thibault, J.; Golkar Naranji, M.R.

2003-01-01

The flow of simplified Phan-Thien-Tanner model fluid between parallel plates is studied analytically for the case where the upper plate moves at constant velocity. Two forms of the stress coefficient, linear and exponential, are used in the constitutive equation. For the linear stress coefficient, the dimensionless pressure gradient, the velocity profile and the product of friction factor and Reynolds number are obtained for a wide range of flow rate, Deborah number and elongational parameter. The results indicate the strong effects of the viscoelastic parameter on the velocity profile, the extremum of the velocity, and the friction factor. A correlation for the maximum pressure rise in single screw extruders is proposed. For the exponential stress coefficient, only velocity profiles were obtained and compared with velocity profiles obtained with the linear stress coefficient

Dynamics of non-stationary processes that follow the maximum of the Rényi entropy principle.

Science.gov (United States)

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.

Social networks, leisure activities and maximum tongue pressure: cross-sectional associations in the Nagasaki Islands Study.

Science.gov (United States)

Nagayoshi, Mako; Higashi, Miho; Takamura, Noboru; Tamai, Mami; Koyamatsu, Jun; Yamanashi, Hirotomo; Kadota, Koichiro; Sato, Shimpei; Kawashiri, Shin-Ya; Koyama, Zenya; Saito, Toshiyuki; Maeda, Takahiro

2017-12-06

Social environment is often associated with health outcomes, but epidemiological evidence for its effect on oral frailty, a potential risk factor for aspiration, is sparse. This study aimed to assess the association between social environment and tongue pressure, as an important measure of oral function. The study focused on family structure, social networks both with and beyond neighbours, and participation in leisure activities. A population-based cross-sectional study. Annual health check-ups in a rural community in Japan. A total of 1982 participants, all over 40 years old. Anyone with missing data for the main outcome (n=14) was excluded. Tongue pressure was measured three times, and the maximum tongue pressure was used for analysis. A multivariable adjusted regression model was used to calculate parameter estimates (B) for tongue pressure. Having a social network involving neighbours (B=2.43, P=0.0001) and taking part in leisure activities (B=1.58, P=0.005) were independently associated with higher tongue pressure, but there was no link with social networks beyond neighbours (B=0.23, P=0.77). Sex-specific analyses showed that for men, having a partner was associated with higher tongue pressure, independent of the number of people in the household (B=2.26, P=0.01), but there was no association among women (B=-0.24, P=0.72; P-interaction=0.059). Having a social network involving neighbours and taking part in leisure activities were independently associated with higher tongue pressure. Marital status may be an important factor in higher tongue pressure in men. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Dynamic calibration of piezoelectric transducers for ballistic high-pressure measurement

Directory of Open Access Journals (Sweden)

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.

On the transient pressure build-up in the full pressure safety shell of watercooled nuclear reactors after a loss of coolant accident

International Nuclear Information System (INIS)

Mansfeld, G.

1979-08-01

The thermo-and fluid-dynamic processes in a multichamber full pressure safety containment during a loss of coolant accident have been investigated. Comparison of the calculations carried out with the computer programs, in which ZOCO VI was used as being representative of similar programs, with the experimental results pointed out discrepancies in the determination of time dependent pressure, pressure difference and temperature curves. This led to the development of a new theoretical model and a program COFLOW which pays particular attention to the fluid dynamic processes in the initial phase of a loss of coolant accident. It can also be used to determine the maximum containment pressure towards the end of a loss of coolant accident. Comparison of the COFLOW results with experiments has shown that COFLOW provides a model and a procedure by which the physical processes in a multichamber full pressure safety containment can be simulated satisfactorily

3-D subduction dynamics in the western Pacific: Mantle pressure, plate kinematics, and dynamic topography.

Science.gov (United States)

Holt, A. F.; Royden, L.; Becker, T. W.; Faccenna, C.

2017-12-01

While it is well established that the slab pull of negatively buoyant oceanic plates is the primary driving force of plate tectonics, the dynamic "details" of subduction have proved difficult to pin down. We use the Philippine Sea Plate region of the western Pacific as a site to explore links between kinematic observables (e.g. topography and plate motions) and the dynamics of the subduction system (e.g. mantle flow, mantle pressure). To first order, the Philippine Sea Plate can be considered to be the central plate of a double slab system containing two slabs that dip in the same direction, to the west. This subduction configuration presents the opportunity to explore subduction dynamics in a setting where two closely spaced slabs interact via subduction-induced mantle flow and stresses transmitted through the intervening plate. We use a 3-D numerical approach (e.g. Holt et al., 2017), augmented by semi-analytical models (e.g. Jagoutz et al., 2017), to develop relationships between dynamic processes and kinematic properties, including plate velocities, lithospheric stress state, slab dip angles, and topography. When combined with subduction zone observables, this allows us to isolate the first order dynamic processes that are in operation in the Philippine Sea Plate region. Our results suggest that positive pressure build-up occurs in the asthenosphere between the two slabs (Izu-Bonin-Mariana and Ryukyu-Nankai), and that this is responsible for producing much of the observed kinematic variability in the region, including the steep dip of the Pacific slab at the Izu-Bonin-Mariana trench, as compared to the flat dip of the Pacific slab north of Japan. We then extend our understanding of the role of asthenospheric pressure to examine the forces responsible for the plate kinematics and dynamic topography of the entire Western Pacific subduction margin(s). References:Holt, A. F., Royden, L. H., Becker, T. W., 2017. Geophys. J. Int., 209, 250-265Jagoutz, O., Royden, L

High-resolution dynamic pressure sensor array based on piezo-phototronic effect tuned photoluminescence imaging.

Science.gov (United States)

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.

Dynamic modelling of check valves in shipping terminals; Modelagem dinamica de valvulas de retencao em terminais maritimos

Energy Technology Data Exchange (ETDEWEB)

Pires, Luis F.G.; Barreto, Claudio V.; Sarmento, Renata C. [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Mecanica. Nucleo de Simulacao Termohidraulica de Dutos (SIMDUT)

2005-07-01

As usual a shipping terminal contains a header and its diameter is smaller than the main pipeline diameter. This diameter reduction amplifies the effects caused by hydraulic transients. It was noticed during simulations that check valves without dynamic modeling may introduce some error in the maximum pressure results without a dynamic model approach. The current paper uses commercial pipeline simulation software to model the dynamic behavior of the check valves. It was studied the header diameter influence and how the check valve model type may change the maximum pressure in the pipeline. It was proved that even a pipeline that works with low pressure and small elevation drop needs a detailed valve modeling to prevent the calculation of unreal pressure values in the region with diameter reduction. (author)

The role of the dynamic pressure in stationary heat conduction of a rarefied polyatomic gas

Energy Technology Data Exchange (ETDEWEB)

Arima, Takashi, E-mail: arima@kanagawa-u.ac.jp [Department of Mechanical Engineering, Faculty of Engineering, Kanagawa University, Yokohama 221-8686 (Japan); Barbera, Elvira, E-mail: ebarbera@unime.it [Department of Mathematics and Computer Science, University of Messina, V.le F. D' Alcontres 31, 98166 Messina (Italy); Brini, Francesca, E-mail: francesca.brini@unibo.it [Department of Mathematics, University of Bologna, via Saragozza 8, 40123 Bologna (Italy); Sugiyama, Masaru, E-mail: sugiyama@nitech.ac.jp [Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2014-07-18

The effect of the dynamic pressure (non-equilibrium pressure) on stationary heat conduction in a rarefied polyatomic gas at rest is elucidated by the theory of extended thermodynamics. It is shown that this effect is observable in a non-polytropic gas. Numerical studies are presented for a para-hydrogen gas as a typical example. - Highlights: • Heat transfer problem in polyatomic rarefied gases is studied in different domains. • Non-zero dynamic pressure is predicted in non-polytropic gases. • The effect of dynamic pressure can be observed indirectly in an experiment. • The case of para-hydrogen is analyzed as an example. • Navier–Stokes, Fourier, and Extended Thermodynamics predictions are compared.

Handling and feeding of biomass to pressurized reactors: safety engineering

Energy Technology Data Exchange (ETDEWEB)

Wilen, Carl; Rautalin, Aimo (Valtion Teknillinen Tutkimuskeskus, Espoo (Finland). Lab. of Fuel and Process Technology)

1993-01-01

There are rather few literature references to or experience of the feed of biomass into a pressurized space. Alternatives given in the literature usually concern handling and feeding technology for coal. Some screw- or piston-operated plug feeders and coal and concrete pump equipment have, however, also been tested with biomasses. Explosion characteristics of fuels and their susceptibility to spontaneous ignition have been studied at both atmospheric and elevated pressures. The maximum explosion pressure and maximum rate of pressure rise, being critical factors in the process design and in the choice of safety equipment, have been determined under these conditions. In pressurized processes, the maintenance of sufficient inertization in fuel-feed systems is an especially critical factor. Peat, bark, and forest residues were used as biofuels, and lignite was used as reference fuel. The results obtained with a dynamic method for spontaneous ignition were compared with experience obtained from the operation of a commercial pressurized peat gasifier of 140 MW. (author)

High-pressure microscopy for tracking dynamic properties of molecular machines.

Science.gov (United States)

Nishiyama, Masayoshi

2017-12-01

High-pressure microscopy is one of the powerful techniques to visualize the effects of hydrostatic pressures on research targets. It could be used for monitoring the pressure-induced changes in the structure and function of molecular machines in vitro and in vivo. This review focuses on the dynamic properties of the assemblies and machines, analyzed by means of high-pressure microscopy measurement. We developed a high-pressure microscope that is optimized both for the best image formation and for the stability to hydrostatic pressure up to 150 MPa. Application of pressure could change polymerization and depolymerization processes of the microtubule cytoskeleton, suggesting a modulation of the intermolecular interaction between tubulin molecules. A novel motility assay demonstrated that high hydrostatic pressure induces counterclockwise (CCW) to clockwise (CW) reversals of the Escherichia coli flagellar motor. The present techniques could be extended to study how molecular machines in complicated systems respond to mechanical stimuli. Copyright © 2017 Elsevier B.V. All rights reserved.

Modeling and simulation of pressurizer dynamic process in PWR nuclear power plant

International Nuclear Information System (INIS)

Ma Jin; Liu Changliang; Li Shu'na

2010-01-01

By analysis of the actual operating characteristics of pressurizer in pressurized water reactor (PWR) nuclear power plant and based on some reasonable simplification and basic assumptions, the quality and energy conservation equations about pressurizer' s steam zone and the liquid zone are set up. The purpose of this paper is to build a pressurizer model of two imbalance districts. Water level and pressure control system of pressurizer is formed though model encapsulation. Dynamic simulation curves of main parameters are also shown. At last, comparisons between the theoretical analysis and simulation results show that the pressurizer model of two imbalance districts is reasonable. (authors)

Modeling beam-front dynamics at low gas pressures

International Nuclear Information System (INIS)

Briggs, R.J.; Yu, S.

1982-01-01

The dynamics of space charge neutralization at the front of an intense self-focused electron beam pulse exhibits important differences in different gas pressure regimes. At very low pressures, the beam front is in the so-called ion-focused regime (IFR) where all secondary electrons are expelled from the beam region by the radial electric field without causing significant additional ionization. We estimate the upper pressure boundary of this regime by considering the distance scale length for cascade (avalanche) ionization. Data from the FX-25 diode experiments indicate a critical transition pressure (P/sub c/) that agrees with this estimate and with its scaling among various gas types. Normal mobility-limited treatments (local conductivity models) of the secondary electrons at the beam front are not justified until the gas pressure is 10 to 50 times higher than P/sub c/, due to runaway of these secondary electrons in the strong space-charge electric field at the lower pressures. The main conclusion of this study is that a non-local phase space (Boltzmann) treatment of the secondary electrons is required to accurately describe these different beam front regimes and the transitions between them; such a code model is currently under development

The maximum and minimum values of the heat Q transmitted from metal to boiling water under atmospheric pressure

International Nuclear Information System (INIS)

Nukiyama, S.

1991-01-01

The quantity of heat transmitted from a metal surface to boiling water increases as the temperature difference ΔT is increased, but after the ΔT has reached a certain limit, quantity Q decreases with further increase in ΔT. This turning point is the maximum value of heat transmitted. The existence of this point was actually observed in the experiment. Under atmospheric pressure, ΔT corresponding to the maximum value of heat transfer for water at 100 degrees C falls between 20-40 degrees C, and Q is between 1,080,000 and 1,800,000 kcal/m 2 h (i.e. between 2,000 and 3,000 kg/m 2 h, if expressed in constant evaporation rate at 100 degrees C); this figure is larger than the maximum value of heat transfer as was previously considered. In this paper the minimum value of heat transfer was obtained, and in the Q-ΔT curve for the high temperature region, the burn-out effect is discussed

Short-time maximum entropy method analysis of molecular dynamics simulation: Unimolecular decomposition of formic acid

Science.gov (United States)

Takahashi, Osamu; Nomura, Tetsuo; Tabayashi, Kiyohiko; Yamasaki, Katsuyoshi

2008-07-01

We performed spectral analysis by using the maximum entropy method instead of the traditional Fourier transform technique to investigate the short-time behavior in molecular systems, such as the energy transfer between vibrational modes and chemical reactions. This procedure was applied to direct ab initio molecular dynamics calculations for the decomposition of formic acid. More reactive trajectories of dehydrolation than those of decarboxylation were obtained for Z-formic acid, which was consistent with the prediction of previous theoretical and experimental studies. Short-time maximum entropy method analyses were performed for typical reactive and non-reactive trajectories. Spectrograms of a reactive trajectory were obtained; these clearly showed the reactant, transient, and product regions, especially for the dehydrolation path.

Physical Limits on Hmax, the Maximum Height of Glaciers and Ice Sheets

Science.gov (United States)

Lipovsky, B. P.

2017-12-01

The longest glaciers and ice sheets on Earth never achieve a topographic relief, or height, greater than about Hmax = 4 km. What laws govern this apparent maximum height to which a glacier or ice sheet may rise? Two types of answer appear possible: one relating to geological process and the other to ice dynamics. In the first type of answer, one might suppose that if Earth had 100 km tall mountains then there would be many 20 km tall glaciers. The counterpoint to this argument is that recent evidence suggests that glaciers themselves limit the maximum height of mountain ranges. We turn, then, to ice dynamical explanations for Hmax. The classical ice dynamical theory of Nye (1951), however, does not predict any break in scaling to give rise to a maximum height, Hmax. I present a simple model for the height of glaciers and ice sheets. The expression is derived from a simplified representation of a thermomechanically coupled ice sheet that experiences a basal shear stress governed by Coulomb friction (i.e., a stress proportional to the overburden pressure minus the water pressure). I compare this model to satellite-derived digital elevation map measurements of glacier surface height profiles for the 200,000 glaciers in the Randolph Glacier Inventory (Pfeffer et al., 2014) as well as flowlines from the Greenland and Antarctic Ice Sheets. The simplified model provides a surprisingly good fit to these global observations. Small glaciers less than 1 km in length are characterized by having negligible influence of basal melt water, cold ( -15C) beds, and high surface slopes ( 30 deg). Glaciers longer than a critical distance 30km are characterized by having an ice-bed interface that is weakened by the presence of meltwater and is therefore not capable of supporting steep surface slopes. The simplified model makes predictions of ice volume change as a function of surface temperature, accumulation rate, and geothermal heat flux. For this reason, it provides insights into

Progress report: qualitative differences between first and second order fit of pressure data - 1/5 scale Mk I BWR pressure suppression experiment and analysis program

International Nuclear Information System (INIS)

Carr, E.; Lai, W.; McCauley, E.

1979-01-01

Results are presented for the 1/5-scale Mark I boiling water reactor pressure suppression experiment. The objective of this study is to calculate the hydrodynamic vertical load function (HVLF) and the maximum download and maximum upload ratios for the 90 0 sector to 7.5 0 section (i.e., the 3D to 2D ratios) together with their associated error bounds. Special graphs are presented of the pressure data that are useful in diagnostic studies of the HVLF. These graphs are three dimensional plots which depict the spatially dependent pressure as a function of time. These plots are qualitative but present an overview, not available by other means, which permits grasp of the subtle complex pattern of transient spatial changes in pressure excited by the dynamics in the pool. Sufficient text is included to describe the general feature of each plot

Dynamic characteristics of laser Doppler flowmetry signals obtained in response to a local and progressive pressure applied on diabetic and healthy subjects

Science.gov (United States)

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.

On the dynamics of a subnanosecond breakdown in nitrogen below atmospheric pressures

Energy Technology Data Exchange (ETDEWEB)

Shklyaev, V. A., E-mail: shklyaev@to.hcei.tsc.ru, E-mail: beh@loi.hcei.tsc.ru [Laboratory of Theoretical Physics, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Institute of High Technology Physics, National Research Tomsk Polytechnic University, 30 Lenin Avenue, 634050 Tomsk (Russian Federation); Baksht, E. Kh., E-mail: shklyaev@to.hcei.tsc.ru, E-mail: beh@loi.hcei.tsc.ru; Tarasenko, V. F. [Laboratory of Optical Radiations, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Belomyttsev, S. Ya.; Grishkov, A. A. [Laboratory of Theoretical Physics, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Burachenko, A. G. [Laboratory of Optical Radiations, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Laboratory of Low Temperature Plasma, Tomsk State University, 36 Lenin Ave., 634050 Tomsk (Russian Federation)

2015-12-07

The dynamics of a breakdown in a gas-filled diode with a highly inhomogeneous electric field was studied in experiments at a time resolution of ∼100 ps and in numerical simulation by the 2D axisymmetric particle-in-cell (PIC) code XOOPIC. The diode was filled with nitrogen at pressures of up to 100 Torr. The dynamics of the electric field distribution in the diode during the breakdown was analyzed, and the factors that limit the pulse duration of the runaway electron beam current at different pressures were determined.

Dynamics of intrarenal pressures and glomerular filtration rate after acetazolamide

DEFF Research Database (Denmark)

Leyssac, P P; Karlsen, F M; Skøtt, O

1991-01-01

-EDTA and lithium. Proximal tubular pressure (Pprox) increased initially by 1.7 +/- 0.1 mmHg after ACZ, causing a decrease in the hydrostatic pressure difference across the glomerular membrane (delta P). EDC increased, and then RBF, glomerular capillary pressure (Pgc), Pprox, and star vessel pressures (Psv) dropped......The dynamics of intrarenal pressures, early distal tubular fluid conductivity (EDC), and renal flood flow (RBF) were studied in rats given acetazolamide (ACZ), an inhibitor of proximal reabsorption. Glomerular filtration rate (GFR) and end-proximal flow were estimated by clearances of 51Cr...... as a result of afferent vasoconstriction. Pprox decreased less than Pgc, resulting in a further decrease in delta P, which after 25-30 s reached a constant level 3-4 mmHg below control. After a transient increase the pressures declined to a new steady state, in which Pprox was equal to control, Pgc...

Large dynamic range pressure sensor based on two semicircle-holes microstructured fiber.

Science.gov (United States)

Liu, Zhengyong; Htein, Lin; Lee, Kang-Kuen; Lau, Kin-Tak; Tam, Hwa-Yaw

2018-01-08

This paper presents a sensitive and large dynamic range pressure sensor based on a novel birefringence microstructured optical fiber (MOF) deployed in a Sagnac interferometer configuration. The MOF has two large semicircle holes in the cladding and a rectangular strut with germanium-doped core in the center. The fiber structure permits surrounding pressure to induce large effective index difference between the two polarized modes. The calculated and measured group birefringence of the fiber are 1.49 × 10 -4 , 1.23 × 10 -4 , respectively, at the wavelength of 1550 nm. Experimental results shown that the pressure sensitivity of the sensor varied from 45,000 pm/MPa to 50,000 pm/MPa, and minimum detectable pressure of 80 Pa and dynamic range of better than 116 dB could be achieved with the novel fiber sensor. The proposed sensor could be used in harsh environment and is an ideal candidate for downhole applications where high pressure measurement at elevated temperature up to 250 °C is needed.

Fracture dynamics of a propagating crack in a pressurized ductile cylinder

International Nuclear Information System (INIS)

Emery, A.F.; Love, W.J.; Kobayashi, A.S.

1977-01-01

A suddenly-introduced axial through-crack in the wall of a pipe pressurized by hot water is allowed to propagate according to Weiss' notch-strength theory of ductile static fracture. The dynamic-fracture criterion used enabled the authors to obtain a unique comparison of the results of ductile-fracture with those of brittle-fracture in a fracturing A533B steel pipe. Since the pipe cross-sectional area is likely to increase with large flap motions under ductile tearing, a large deformation shell-finite-difference-dynamic-code which includes rotary inertia was used in this analysis. The uniaxial-stress-strain curve of A533B steel was approximated by a bilinear-stress-strain where Von-Mises yield criterion and associated flow rule were used in the elastic-plastic analysis. The fluid pressure was assumed constant and thus pipe flaps are only lightly loaded by pressure in this analysis. (Auth.)

Relationship between Maximum Principle and Dynamic Programming for Stochastic Recursive Optimal Control Problems and Applications

Directory of Open Access Journals (Sweden)

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.

A study of dynamic foot pressure measurement in diabetic patients

Directory of Open Access Journals (Sweden)

Milka D Madhale

2017-01-01

Full Text Available Introduction: Diabetic foot ulcer is a major source of morbidity and a leading cause of hospitalization. It is estimated that approximately 20% of hospital admissions among patients with diabetes mellitus are due to diabetic foot ulcer. It can lead to infection, gangrene, amputation, and even death if appropriate care is not provided. Overall, the lower limb amputation in diabetic patients is 15 times higher than in non-diabetics. In the majority of cases, the cause for the foot ulcer is the altered architecture of the foot due to neuropathy resulting in abnormal pressure points on the soles. Purpose: The aim of this study is to develop low cost, lightweight foot pressure scanner and check its reliability and validity which can help to prevent foot ulceration. Design/Methodology/Approach: In the present study, a low cost, lightweight foot pressure scanner is developed, and dynamic plantar pressures in a group of 110 Indian patients with diabetes with or without neuropathy and foot ulcers are measured. Practical Implications: If these pressure points can be detected, ulcers can be prevented by providing offloading footwear. Originality/Value: Differences are found in dynamic foot pressures in different study groups, namely, diabetic patients, patients with diabetic peripheral neuropathy, patients with foot ulcers, and nondiabetics. The differences are significant (P < 0.01, which showed the validity of the tool. Reliability and consistency of the tool was checked by test–retest method. Paper Type: Original Research work. Conclusion: Based on the results of the present study, it is concluded that the scanner is successfully developed and it can measure foot pressures. It is a novel device to proactively monitor foot health in diabetics in an effort to prevent and reduce diabetic foot complications.

A study on compliant layers and its influence on dynamic response of a hydrodynamic journal bearing

DEFF Research Database (Denmark)

Thomsen, Kim; Klit, Peder

2011-01-01

For some hydrodynamic bearing applications polymer-lined bearings are chosen over traditional metal alloy bearings due to their better wear and friction properties when operating at very thin films, e.g. in the mixed lubrication region. The introduction of a compliant layer also affects the dynamic...... used to evaluate hydrodynamic bearing designs: dynamic response, maximum pressure, minimum film thickness, wear, power loss and temperature response. The primary findings are that the maximum pressures are reduced significantly and this comes at the expense of slightly higher eccentricity ratios during...

Energy harvesting from hydraulic pressure fluctuations

International Nuclear Information System (INIS)

Cunefare, K A; Skow, E A; Erturk, A; Savor, J; Verma, N; Cacan, M R

2013-01-01

State-of-the-art hydraulic hose and piping systems employ integral sensor nodes for structural health monitoring to avoid catastrophic failures. Energy harvesting in hydraulic systems could enable self-powered wireless sensor nodes for applications such as energy-autonomous structural health monitoring and prognosis. Hydraulic systems inherently have a high energy intensity associated with the mean pressure and flow. Accompanying the mean pressure is the dynamic pressure ripple, which is caused by the action of pumps and actuators. Pressure ripple is a deterministic source with a periodic time-domain behavior conducive to energy harvesting. An energy harvester prototype was designed for generating low-power electricity from pressure ripples. The prototype employed an axially-poled off-the-shelf piezoelectric stack. A housing isolated the stack from the hydraulic fluid while maintaining a mechanical coupling allowing for dynamic-pressure-induced deflection of the stack. The prototype exhibited an off-resonance energy harvesting problem since the fundamental resonance of the piezoelectric stack was much higher than the frequency content of the pressure ripple. The prototype was designed to provide a suitable power output for powering sensors with a maximum output of 1.2 mW. This work also presents electromechanical model simulations and experimental characterization of the piezoelectric power output from the pressure ripple in terms of the force transmitted into the harvester. (paper)

The Influence of Shaping Air Pressure of Pneumatic Spray Gun

Science.gov (United States)

Chen, Wenzhuo; Chen, Yan; Pan, Haiwei; Zhang, Weiming; Li, Bo

2018-02-01

The shaping air pressure is a very important parameter in the application of pneumatic spray gun, and studying its influence on spray flow field and film thickness distribution has practical values. In this paper, Euler-Lagrangian method is adopted to describe the two-phase spray flow of pneumatic painting process, and the air flow fields, spray patterns and dynamic film thickness distributions were obtained with the help of the computational fluid dynamics code—ANSYS Fluent. Results show that with the increase of the shaping air pressure, the air phase flow field spreads in the plane perpendicular to the shaping air hole plane, the spray pattern becomes narrower and flatter, and the width of the dynamic film increases with the reduced maximum value of the film thickness. But the film thickness distribution seems to change little with the shaping air pressure decreasing from 0.6bar to 0.9bar.

Full-scale Mark II CRT program: dynamic response evaluation test of pressure transducers

International Nuclear Information System (INIS)

Kukita, Yutaka; Namatame, Ken; Takeshita, Isao; Shiba, Masayoshi

1982-12-01

A dynamic response evaluation test of pressure transducers was conducted in support of the JAERI Full-Scale Mark II CRT (Containment Response Test) Program. The test results indicated that certain of the cavity-type transducers used in the early blowdown test had undesirable response characteristics. The transducer mounting scheme was modified to avoid trapping of air bubbles in the pressure transmission tubing attached to the transducers. The dynamic response of the modified transducers was acceptable within the frequency range of 200 Hz. (author)

Dynamic Pressure Gradient Model of Axial Piston Pump and Parameters Optimization

Directory of Open Access Journals (Sweden)

Shi Jian

2014-01-01

Full Text Available The unsteady pressure gradient can cause flow noise in prepressure rising of piston pump, and the fluid shock comes up due to the large pressure difference of the piston chamber and discharge port in valve plate. The flow fluctuation control is the optimization objective in previous study, which cannot ensure the steady pressure gradient. Our study is to stabilize the pressure gradient in prepressure rising and control the pressure of piston chamber approaching to the pressure in discharge port after prepressure rising. The models for nonoil shock and dynamic pressure of piston chamber in prepressure rising are established. The parameters of prepressure rising angle, cross angle, wrap angle of V-groove, vertex angle of V-groove, and opening angle of V-groove were optimized, based on which the pressure of the piston chamber approached the pressure in discharge port after prepressure rising, and the pressure gradient is more steady compared to the original parameters. The max pressure gradient decreased by 70.8% and the flow fluctuation declined by 21.4%, which showed the effectivness of optimization.

Aspherical bubble dynamics and oscillation times

Energy Technology Data Exchange (ETDEWEB)

Godwin, R.P.; Chapyak, E.J. [Los Alamos National Lab., NM (United States); Noack, J.; Vogel, A. [Medizinisches Laserzentrum Luebeck (Germany)

1999-03-01

The cavitation bubbles common in laser medicine are rarely perfectly spherical and are often located near tissue boundaries, in vessels, etc., which introduce aspherical dynamics. Here, novel features of aspherical bubble dynamics are explored. Time-resolved experimental photographs and simulations of large aspect ratio (length:diameter {approximately}20) cylindrical bubble dynamics are presented. The experiments and calculations exhibit similar dynamics. A small high-pressure cylindrical bubble initially expands radially with hardly any axial motion. Then, after reaching its maximum volume, a cylindrical bubble collapses along its long axis with relatively little radial motion. The growth-collapse period of these very aspherical bubbles differs only sightly from twice the Rayleigh collapse time for a spherical bubble with an equivalent maximum volume. This fact justifies using the temporal interval between the acoustic signals emitted upon bubble creation and collapse to estimate the maximum bubble volume. As a result, hydrophone measurements can provide an estimate of the bubble energy even for aspherical bubbles. The prolongation of the oscillation period of bubbles near solid boundaries relative to that of isolated spherical bubbles is also discussed.

Self-pressurization analysis of the natural circulation integral nuclear reactor using a new dynamic model

Directory of Open Access Journals (Sweden)

Ali Farsoon Pilehvar

2018-06-01

Full Text Available Self-pressurization analysis of the natural circulation integral nuclear reactor through a new dynamic model is studied. Unlike conventional pressurized water reactors, this reactor type controls the system pressure using saturated coolant water in the steam dome at the top of the pressure vessel. Self-pressurization model is developed based on conservation of mass, volume, and energy by predicting the condensation that occurs in the steam dome and the flashing inside the chimney using the partial differential equation. A simple but functional model is adopted for the steam generator. The obtained results indicate that the variable measurement is consistent with design data and that this new model is able to predict the dynamics of the reactor in different situations. It is revealed that flashing and condensation power are in direct relation with the stability of the system pressure, without which pressure convergence cannot be established. Keywords: Condensation Power, Flashing Phenomenon, Natural Circulation, Self-Pressurization, Small Modular Reactor

MAXIMUM PRINCIPLE FOR SUBSONIC FLOW WITH VARIABLE ENTROPY

Directory of Open Access Journals (Sweden)

B. Sizykh Grigory

2017-01-01

Full Text Available Maximum principle for subsonic flow is fair for stationary irrotational subsonic gas flows. According to this prin- ciple, if the value of the velocity is not constant everywhere, then its maximum is achieved on the boundary and only on the boundary of the considered domain. This property is used when designing form of an aircraft with a maximum critical val- ue of the Mach number: it is believed that if the local Mach number is less than unit in the incoming flow and on the body surface, then the Mach number is less then unit in all points of flow. The known proof of maximum principle for subsonic flow is based on the assumption that in the whole considered area of the flow the pressure is a function of density. For the ideal and perfect gas (the role of diffusion is negligible, and the Mendeleev-Clapeyron law is fulfilled, the pressure is a function of density if entropy is constant in the entire considered area of the flow. Shows an example of a stationary sub- sonic irrotational flow, in which the entropy has different values on different stream lines, and the pressure is not a function of density. The application of the maximum principle for subsonic flow with respect to such a flow would be unreasonable. This example shows the relevance of the question about the place of the points of maximum value of the velocity, if the entropy is not a constant. To clarify the regularities of the location of these points, was performed the analysis of the com- plete Euler equations (without any simplifying assumptions in 3-D case. The new proof of the maximum principle for sub- sonic flow was proposed. This proof does not rely on the assumption that the pressure is a function of density. Thus, it is shown that the maximum principle for subsonic flow is true for stationary subsonic irrotational flows of ideal perfect gas with variable entropy.

On the pressure evolution of dynamic properties of supercooled liquids

Energy Technology Data Exchange (ETDEWEB)

Drozd-Rzoska, Aleksandra; Rzoska, Sylwester J [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland); Roland, C Michael [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States); Imre, Attila R [KFKI Atomic Energy Research Institute, 1525 Budapest, POB 49 (Hungary)

2008-06-18

A pressure counterpart of the Vogel-Fulcher-Tammann (VFT) equation for representing the evolution of dielectric relaxation times or related dynamic properties is discussed: {tau}(P) = {tau}{sub 0}{sup P}exp[D{sub P}{delta}P(P{sub 0}-{delta}P)], where {delta}P = P-P{sub SL}, P{sub 0} is the ideal glass pressure estimation, D{sub P} is the pressure fragility strength coefficient, and the prefactor {tau}{sub 0}{sup P} is related to the relaxation time at the stability limit (P{sub SL}) in the negative pressure domain. The discussion is extended to the Avramov model (AvM) relation {tau}(T,P) = {tau}{sub 0}exp[{epsilon}(T{sub g}(P)/T){sup D}], supplemented with a modified Simon-Glatzel-type equation for the pressure dependence of the glass temperature (T{sub g}(P)), enabling an insight into the negative pressure region. A recently postulated (Dyre 2006 Rev. Mod. Phys. 78 953) comparison between the VFT and the AvM-type descriptions is examined, for both the temperature and the pressure paths. Finally, we address the question 'Does fragility depend on pressure?' from the title of Paluch M et al (2001 J. Chem. Phys. 114 8048) and propose a pressure counterpart for the 'Angell plot'.

Dynamic behaviour of high-pressure natural-gas flow in pipelines

International Nuclear Information System (INIS)

Gato, L.M.C.; Henriques, J.C.C.

2005-01-01

The aim of the present study is the numerical modelling of the dynamic behaviour of high-pressure natural-gas flow in pipelines. The numerical simulation was performed by solving the conservation equations, for one-dimensional compressible flow, using the Runge-Kutta discontinuous Galerkin method, with third-order approximation in space and time. The boundary conditions were imposed using a new weak formulation based on the characteristic variables. The occurrence of pressure oscillations in natural-gas pipelines was studied as a result of the compression wave originated by the rapid closure of downstream shut-off valves. The effect of the partial reflection of pressure waves was also analyzed in the transition between pipes of different cross-sectional areas

Dynamic behaviour of high-pressure natural-gas flow in pipelines

Energy Technology Data Exchange (ETDEWEB)

Gato, L.M.C. [Department of Mechanical Engineering, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)]. E-mail: lgato@mail.ist.utl.pt; Henriques, J.C.C. [Department of Mechanical Engineering, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)]. E-mail: jcch@mail.ist.utl.pt

2005-10-01

The aim of the present study is the numerical modelling of the dynamic behaviour of high-pressure natural-gas flow in pipelines. The numerical simulation was performed by solving the conservation equations, for one-dimensional compressible flow, using the Runge-Kutta discontinuous Galerkin method, with third-order approximation in space and time. The boundary conditions were imposed using a new weak formulation based on the characteristic variables. The occurrence of pressure oscillations in natural-gas pipelines was studied as a result of the compression wave originated by the rapid closure of downstream shut-off valves. The effect of the partial reflection of pressure waves was also analyzed in the transition between pipes of different cross-sectional areas.

Effect of pressure on the transfer functions of premixed methane and propane swirl flames

KAUST Repository

Di Sabatino, Francesco

2018-04-24

This paper reports on the effect of pressure on the response of methane–air and propane–air swirl flames to acoustic excitation of the flow. These effects are analyzed on the basis of the flame transfer function (FTF) formalism, experimentally determined from velocity and global OH* chemiluminescence measurements at pressures up to 5 bar. In parallel, phase-locked images of OH* chemiluminescence are collected and analyzed in order to determine the associated flame dynamics. Flame transfer functions and visual flame dynamics at atmospheric pressure are found to be similar to previous studies with comparable experimental conditions. Regardless of pressure, propane flames exhibit a much larger FTF gain than methane flames. For both fuels, the effect of pressure primarily is to modify the gain response at the local maximum of the FTF, at a Strouhal number around 0.5 (176 Hz). For methane flames, this gain maximum increases monotonically with pressure, while for propane flames it increases from 1 to 3 bar and decreases from 3 to 5 bar. At this frequency and regardless of pressure, the flame motion is driven by flame vortex roll-up, suggesting that pressure affects the FTF by modifying the interaction of the flame with the vortex detached from the injector rim during a forcing period. The complex heat transfer, fluid dynamics, and combustion coupling in this configuration does not allow keeping the vortex properties constant when pressure is increased. However, the different trends of the FTF gain observed for methane and propane fuels with increasing pressure imply that intrinsic flame properties and fuel chemistry, and their variation with pressure, play an important role in controlling the response of these flames to acoustic forcing.

Tracking a Solar Wind Dynamic Pressure Pulses' Impact Through the Magnetosphere Using the Heliophysics System Observatory

Science.gov (United States)

Vidal-Luengo, S.; Moldwin, M.

2017-12-01

During northward Interplanetary Magnetic Field (IMF) Bz conditions, the magnetosphere acts as a closed "cavity" and reacts to solar wind dynamic pressure pulses more simply than during southward IMF conditions. Effects of solar wind dynamic pressure have been observed as geomagnetic lobe compressions depending on the characteristics of the pressure pulse and the spacecraft location. One of the most important aspects of this study is the incorporation of simultaneous observations by different missions, such as WIND, CLUSTER, THEMIS, MMS, Van Allen Probes and GOES as well as magnetometer ground stations that allow us to map the magnetosphere response at different locations during the propagation of a pressure pulse. In this study we used the SYM-H as an indicator of dynamic pressure pulses occurrence from 2007 to 2016. The selection criteria for events are: (1) the increase in the index must be bigger than 10 [nT] and (2) the rise time must be in less than 5 minutes. Additionally, the events must occur under northward IMF and at the same time at least one spacecraft has to be located in the magnetosphere nightside. Using this methodology we found 66 pressure pulse events for analysis. Most of them can be classified as step function pressure pulses or as sudden impulses (increase followed immediately by a decrease of the dynamic pressure). Under these two categories the results show some systematic signatures depending of the location of the spacecraft. For both kind of pressure pulse signatures, compressions are observed on the dayside. However, on the nightside compressions and/or South-then-North magnetic signatures can be observed for step function like pressure pulses, meanwhile for the sudden impulse kind of pressure pulses the magnetospheric response seems to be less global and more dependent on the local conditions.

On discharge from poppet valves: effects of pressure and system dynamics

Science.gov (United States)

Winroth, P. M.; Ford, C. L.; Alfredsson, P. H.

2018-02-01

Simplified flow models are commonly used to design and optimize internal combustion engine systems. The exhaust valves and ports are modelled as straight pipe flows with a corresponding discharge coefficient. The discharge coefficient is usually determined from steady-flow experiments at low pressure ratios and at fixed valve lifts. The inherent assumptions are that the flow through the valve is insensitive to the pressure ratio and may be considered as quasi-steady. The present study challenges these two assumptions through experiments at varying pressure ratios and by comparing measurements of the discharge coefficient obtained under steady and dynamic conditions. Steady flow experiments were performed in a flow bench, whereas the dynamic measurements were performed on a pressurized, 2 l, fixed volume cylinder with one or two moving valves. In the latter experiments an initial pressure (in the range 300-500 kPa) was established whereafter the valve(s) was opened with a lift profile corresponding to different equivalent engine speeds (in the range 800-1350 rpm). The experiments were only concerned with the blowdown phase, i.e. the initial part of the exhaustion process since no piston was simulated. The results show that the process is neither pressure-ratio independent nor quasi-steady. A measure of the "steadiness" has been defined, relating the relative change in the open flow area of the valve to the relative change of flow conditions in the cylinder, a measure that indicates if the process can be regarded as quasi-steady or not.

Pilot study assessment of dynamic vascular changes in breast cancer with near-infrared tomography from prospectively targeted manipulations of inspired end-tidal partial pressure of oxygen and carbon dioxide.

Science.gov (United States)

Jiang, Shudong; Pogue, Brian W; Michaelsen, Kelly E; Jermyn, Michael; Mastanduno, Michael A; Frazee, Tracy E; Kaufman, Peter A; Paulsen, Keith D

2013-07-01

The dynamic vascular changes in the breast resulting from manipulation of both inspired end-tidal partial pressure of oxygen and carbon dioxide were imaged using a 30 s per frame frequency-domain near-infrared spectral (NIRS) tomography system. By analyzing the images from five subjects with asymptomatic mammography under different inspired gas stimulation sequences, the mixture that maximized tissue vascular and oxygenation changes was established. These results indicate maximum changes in deoxy-hemoglobin, oxygen saturation, and total hemoglobin of 21, 9, and 3%, respectively. Using this inspired gas manipulation sequence, an individual case study of a subject with locally advanced breast cancer undergoing neoadjuvant chemotherapy (NAC) was analyzed. Dynamic NIRS imaging was performed at different time points during treatment. The maximum tumor dynamic changes in deoxy-hemoglobin increased from less than 7% at cycle 1, day 5 (C1, D5) to 17% at (C1, D28), which indicated a complete response to NAC early during treatment and was subsequently confirmed pathologically at the time of surgery.

Error Propagation dynamics: from PIV-based pressure reconstruction to vorticity field calculation

Science.gov (United States)

Pan, Zhao; Whitehead, Jared; Richards, Geordie; Truscott, Tadd; USU Team; BYU Team

2017-11-01

Noninvasive data from velocimetry experiments (e.g., PIV) have been used to calculate vorticity and pressure fields. However, the noise, error, or uncertainties in the PIV measurements would eventually propagate to the calculated pressure or vorticity field through reconstruction schemes. Despite the vast applications of pressure and/or vorticity field calculated from PIV measurements, studies on the error propagation from the velocity field to the reconstructed fields (PIV-pressure and PIV-vorticity are few. In the current study, we break down the inherent connections between PIV-based pressure reconstruction and PIV-based vorticity calculation. The similar error propagation dynamics, which involve competition between physical properties of the flow and numerical errors from reconstruction schemes, are found in both PIV-pressure and PIV-vorticity reconstructions.

Maximum a posteriori reconstruction of the Patlak parametric image from sinograms in dynamic PET

International Nuclear Information System (INIS)

Wang Guobao; Fu Lin; Qi Jinyi

2008-01-01

Parametric imaging using the Patlak graphical method has been widely used to analyze dynamic PET data. Conventionally a Patlak parametric image is generated by reconstructing a sequence of dynamic images first and then performing Patlak graphical analysis on the time-activity curves pixel-by-pixel. However, because it is rather difficult to model the noise distribution in reconstructed images, the spatially variant noise correlation is simply ignored in the Patlak analysis, which leads to sub-optimal results. In this paper we present a Bayesian method for reconstructing Patlak parametric images directly from raw sinogram data by incorporating the Patlak plot model into the image reconstruction procedure. A preconditioned conjugate gradient algorithm is used to find the maximum a posteriori solution. The proposed direct method is statistically more efficient than the conventional indirect approach because the Poisson noise distribution in PET data can be accurately modeled in the direct reconstruction. The computation cost of the direct method is similar to reconstruction time of two dynamic frames. Therefore, when more than two dynamic frames are used in the Patlak analysis, the direct method is faster than the conventional indirect approach. We conduct computer simulations to validate the proposed direct method. Comparisons with the conventional indirect approach show that the proposed method results in a more accurate estimate of the parametric image. The proposed method has been applied to dynamic fully 3D PET data from a microPET scanner

Predicting the Maximum Dynamic Strength in Bench Press: The High Precision of the Bar Velocity Approach.

Science.gov (United States)

Loturco, Irineu; Kobal, Ronaldo; Moraes, José E; Kitamura, Katia; Cal Abad, César C; Pereira, Lucas A; Nakamura, Fábio Y

2017-04-01

Loturco, I, Kobal, R, Moraes, JE, Kitamura, K, Cal Abad, CC, Pereira, LA, and Nakamura, FY. Predicting the maximum dynamic strength in bench press: the high precision of the bar velocity approach. J Strength Cond Res 31(4): 1127-1131, 2017-The aim of this study was to determine the force-velocity relationship and test the possibility of determining the 1 repetition maximum (1RM) in "free weight" and Smith machine bench presses. Thirty-six male top-level athletes from 3 different sports were submitted to a standardized 1RM bench press assessment (free weight or Smith machine, in randomized order), following standard procedures encompassing lifts performed at 40-100% of 1RM. The mean propulsive velocity (MPV) was measured in all attempts. A linear regression was performed to establish the relationships between bar velocities and 1RM percentages. The actual and predicted 1RM for each exercise were compared using a paired t-test. Although the Smith machine 1RM was higher (10% difference) than the free weight 1RM, in both cases the actual and predicted values did not differ. In addition, the linear relationship between MPV and percentage of 1RM (coefficient of determination ≥95%) allow determination of training intensity based on the bar velocity. The linear relationships between the MPVs and the relative percentages of 1RM throughout the entire range of loads enable coaches to use the MPV to accurately monitor their athletes on a daily basis and accurately determine their actual 1RM without the need to perform standard maximum dynamic strength assessments.

Lattice dynamics, elasticity and magnetic abnormality in ordered crystalline alloys Fe3Pt at high pressures

Science.gov (United States)

Cheng, Tai-min; Yu, Guo-Liang; Su, Yong; Ge, Chong-Yuan; Zhang, Xin-Xin; Zhu, Lin; Li, Lin

2018-05-01

The ordered crystalline Invar alloy Fe3Pt is in a special magnetic critical state, under which the lattice dynamic stability of the system is extremely sensitive to external pressures. We studied the pressure dependence of enthalpy and magnetism of Fe3Pt in different crystalline alloys by using the first-principles projector augmented-wave method based on the density functional theory. Results show that the P4/mbm structure is the ground state structure and is more stable relative to other structures at pressures below 18.54 GPa. The total magnetic moments of L12, I4/mmm and DO22 structures decrease rapidly with pressure and oscillate near the ferromagnetic collapse critical pressure. At the pressure of 43 GPa, the ferrimagnetic property in DO22 structure becomes apparently strengthened and its volume increases rapidly. The lattice dynamics calculation for L12 structures at high pressures shows that the spontaneous magnetization of the system in ferromagnetic states induces the softening of the transverse acoustic phonon TA1 (M), and there exists a strong spontaneous volume magnetostriction at pressures below 26.95 GPa. Especially, the lattice dynamics stability is sensitive to pressure, in the pressure range between the ferromagnetic collapse critical pressure (41.9 GPa) and the magnetism completely disappearing pressure (57.25 GPa), and near the pressure of phase transition from L12 to P4/mbm structure (27.27 GPa). Moreover, the instability of magnetic structure leads to a prominent elastic modulus oscillation, and the spin polarizability of electrons near the Fermi level is very sensitive to pressures in that the pressure range. The pressure induces the stability of the phonon spectra of the system at pressures above 57.25 GPa.

Normalized Dynamic Blood Pressure Parameters - Additional Marker of Hypertension Risk

Czech Academy of Sciences Publication Activity Database

Jurák, Pavel; Halámek, Josef; Vondra, Vlastimil; Leinveber, P.; Fráňa, P.; Plachý, M.; Souček, M.; Kára, T.

2008-01-01

Roč. 6, č. 1 (2008), s. 103 ISSN 1556-7451. [World Congress on Heart Disease /14./. 26.07.2008-29.07.2008, Toronto] Institutional research plan: CEZ:AV0Z20650511 Keywords : hypertension * vessel compliance * blood pressure * dynamic parameters Subject RIV: FA - Cardiovascular Disease s incl. Cardiotharic Surgery

Development of plant dynamic analysis code for integrated self-pressurized water reactor (ISPDYN), and comparative study of pressure control methods

International Nuclear Information System (INIS)

Kusunoki, Tsuyoshi; Yokomura, Takeyoshi; Nabeshima, Kunihiko; Shimazaki, Junya; Shinohara, Yoshikuni.

1988-01-01

This report describes the development of plant dynamic analysis code (ISPDYN) for integrated self-pressurized water reactor, and comparative study of pressure control methods with this code. ISPDYN is developed for integrated self-pressurized water reactor, one of the trial design by JAERI. In the transient responses, the calculated results by ISPDYN are in good agreement with the DRUCK calculations. In addition, this report presents some sensitivity studies for selected cases. Computing time of this code is very short so as about one fifth of real time. The comparative study of self-pressurized system with forced-pressurized system by this code, for rapid load decrease and increase cases, has provided useful informations. (author)

Studies of the pressure dependence of the charge density distribution in cerium phosphide by the maximum-entropy method

CERN Document Server

Ishimatsu, N; Takata, M; Nishibori, E; Sakata, M; Hayashi, J; Shirotani, I; Shimomura, O

2002-01-01

The physical properties relating to 4f electrons in cerium phosphide, especially the temperature dependence and the isomorphous transition that occurs at around 10 GPa, were studied by means of x-ray powder diffraction and charge density distribution maps derived by the maximum-entropy method. The compressibility of CeP was exactly determined using a helium pressure medium and the anomaly that indicated the isomorphous transition was observed in the compressibility. We also discuss the anisotropic charge density distribution of Ce ions and its temperature dependence.

Modeling the dynamic response of pressures in a distributed helium refrigeration system

International Nuclear Information System (INIS)

Brubaker, J.C.

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

Modeling the dynamic response of pressures in a distributed helium refrigeration system

Energy Technology Data Exchange (ETDEWEB)

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.

Dynamics of ZnO laser produced plasma in high pressure argon

International Nuclear Information System (INIS)

Kaydashev, V.E.; Lunney, J.G.

2011-01-01

Pulsed laser deposition of ZnO in high pressure gas offers a route for the catalyst-free preparation of ZnO nanorods less than 10 nm in diameter. This paper describes the results of some experiments to investigate the laser plume dynamics in the high gas pressure (5 x 10 3 -10 4 Pa) regime used for PLD of ZnO nanorods. In this regime the ablation plume is strongly coupled to the gas and the plume expansion is brought to a halt within about 1 cm from the target. A 248 nm excimer laser was used to ablate a ceramic ZnO target in various pressures of argon. Time- and space-resolved UV/vis emission spectroscopy and Langmuir probe measurements were used to diagnose the plasma and follow the plume dynamics. By measuring the spatial profiles of Zn I and Zn II spectral lines it was possible to follow the propagation of the external and internal shock waves associated with the interaction of the ablation plume with the gas. The Langmuir probe measurements showed that the electron density was 10 9 -10 10 cm -3 and the electron temperature was several eV. At these conditions the ionization equilibrium is described by the collisional-radiative model. The plume dynamics was also studied for ZnO targets doped with elements which are lighter (Mg), comparable to (Ga), and heavier (Er) than Zn, to see if there is any elemental segregation in the plume.

Constant pressure and temperature discrete-time Langevin molecular dynamics

Energy Technology Data Exchange (ETDEWEB)

Grønbech-Jensen, Niels [Department of Mechanical and Aerospace Engineering, University of California, Davis, California 95616 (United States); Department of Mathematics, University of California, Davis, California 95616 (United States); Farago, Oded [Department of Biomedical Engineering, Ben Gurion University of the Negev, Be' er Sheva 84105 (Israel); Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Be' er Sheva 84105 (Israel)

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.

Pressure-area isotherm of a lipid monolayer from molecular dynamics simulations

NARCIS (Netherlands)

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

Dynamic knock detection and quantification in a spark ignition engine by means of a pressure based method

International Nuclear Information System (INIS)

Galloni, Enzo

2012-01-01

Highlights: ► Experimental data have been analyzed by a pressure based method. ► Knock intensity level depends on a threshold varying with the engine operating point. ► A dynamic method is proposed to overcome the definition of a predetermined threshold. ► The knock intensity of each operating point is quantified by a dimensionless index. ► The knock limited spark advance can be detected by means of this index. - Abstract: In spark ignition engines, knock onset limits the maximum spark advance. An inaccurate identification of this limit penalises the fuel conversion efficiency. Thus it is very important to define a knock detection method able to assess the knock intensity of an engine operating point. Usually, in engine development, knock event is evaluated by analysing the in-cylinder pressure trace. Data are filtered and processed in order to obtain some indices correlated to the knock intensity, then the calculated value is compared to a predetermined threshold. The calibration of this threshold is complex and difficult; statistical approach should be used, but often empirical values are considered. In this paper a method that dynamically calculates the knock threshold necessary to determine the knock event is proposed. The purpose is to resolve cycle by cycle the knock intensity related to an individual engine cycle without setting a predetermined threshold. The method has been applied to an extensive set of experimental data relative to a gasoline spark-ignition engine. Results are correlated to those obtained considering a traditional method, where a statistical approach has been used to detect knock.

The effectiveness of combining inspiratory muscle training with manual therapy and a therapeutic exercise program on maximum inspiratory pressure in adults with asthma: a randomized clinical trial.

Science.gov (United States)

López-de-Uralde-Villanueva, Ibai; Candelas-Fernández, Pablo; de-Diego-Cano, Beatriz; Mínguez-Calzada, Orcález; Del Corral, Tamara

2018-06-01

The objective of this study was to evaluate whether the addition of manual therapy and therapeutic exercise protocol to inspiratory muscle training was more effective in improving maximum inspiratory pressure than inspiratory muscle training in isolation. This is a single-blinded, randomized controlled trial. In total, 43 patients with asthma were included in this study. The patients were allocated into one of the two groups: (1) inspiratory muscle training ( n = 21; 20-minute session) or (2) inspiratory muscle training (20-minute session) combined with a program of manual therapy (15-minute session) and therapeutic exercise (15-minute session; n = 22). All participants received 12 sessions, two days/week, for six weeks and performed the domiciliary exercises protocol. The main measures such as maximum inspiratory pressure, spirometric measures, forward head posture, and thoracic kyphosis were recorded at baseline and after the treatment. For the per-protocol analysis, between-group differences at post-intervention were observed in maximum inspiratory pressure (19.77 cmH 2 O (11.49-28.04), P < .05; F = 22.436; P < .001; η 2 p  = 0.371) and forward head posture (-1.25 cm (-2.32 to -0.19), P < .05; F = 5.662; P = .022; η 2 p  = 0.13). The intention-to-treat analysis showed the same pattern of findings. The inspiratory muscle training combined with a manual therapy and therapeutic exercise program is more effective than its application in isolation for producing short-term maximum inspiratory pressure and forward head posture improvements in patients with asthma.

Effect of dynamic high pressure homogenization on the aggregation state of soy protein.

Science.gov (United States)

Keerati-U-Rai, Maneephan; Corredig, Milena

2009-05-13

Although soy proteins are often employed as functional ingredients in oil-water emulsions, very little is known about the aggregation state of the proteins in solution and whether any changes occur to soy protein dispersions during homogenization. The effect of dynamic high pressure homogenization on the aggregation state of the proteins was investigated using microdifferential scanning calorimetry and high performance size exclusion chromatography coupled with multiangle laser light scattering. Soy protein isolates as well as glycinin and beta-conglycinin fractions were prepared from defatted soy flakes and redispersed in 50 mM sodium phosphate buffer at pH 7.4. The dispersions were then subjected to homogenization at two different pressures, 26 and 65 MPa. The results demonstrated that dynamic high pressure homogenization causes changes in the supramolecular structure of the soy proteins. Both beta-conglycinin and glycinin samples had an increased temperature of denaturation after homogenization. The chromatographic elution profile showed a reduction in the aggregate concentration with homogenization pressure for beta-conglycinin and an increase in the size of the soluble aggregates for glycinin and soy protein isolate.

Weakest solar wind of the space age and the current 'MINI' solar maximum

International Nuclear Information System (INIS)

McComas, D. J.; Angold, N.; Elliott, H. A.; Livadiotis, G.; Schwadron, N. A.; Smith, C. W.; Skoug, R. M.

2013-01-01

The last solar minimum, which extended into 2009, was especially deep and prolonged. Since then, sunspot activity has gone through a very small peak while the heliospheric current sheet achieved large tilt angles similar to prior solar maxima. The solar wind fluid properties and interplanetary magnetic field (IMF) have declined through the prolonged solar minimum and continued to be low through the current mini solar maximum. Compared to values typically observed from the mid-1970s through the mid-1990s, the following proton parameters are lower on average from 2009 through day 79 of 2013: solar wind speed and beta (∼11%), temperature (∼40%), thermal pressure (∼55%), mass flux (∼34%), momentum flux or dynamic pressure (∼41%), energy flux (∼48%), IMF magnitude (∼31%), and radial component of the IMF (∼38%). These results have important implications for the solar wind's interaction with planetary magnetospheres and the heliosphere's interaction with the local interstellar medium, with the proton dynamic pressure remaining near the lowest values observed in the space age: ∼1.4 nPa, compared to ∼2.4 nPa typically observed from the mid-1970s through the mid-1990s. The combination of lower magnetic flux emergence from the Sun (carried out in the solar wind as the IMF) and associated low power in the solar wind points to the causal relationship between them. Our results indicate that the low solar wind output is driven by an internal trend in the Sun that is longer than the ∼11 yr solar cycle, and they suggest that this current weak solar maximum is driven by the same trend.

Connectivity dynamics since the Last Glacial Maximum in the northern Andes: a pollen-driven framework to assess potential migration

NARCIS (Netherlands)

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

The effect of a dynamic PCL brace on patellofemoral compartment pressures in PCL-and PCL/PLC-deficient knees.

Science.gov (United States)

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.

A whole-body mathematical model for intracranial pressure dynamics.

Science.gov (United States)

Lakin, William D; Stevens, Scott A; Tranmer, Bruce I; Penar, Paul L

2003-04-01

Most attempts to study intracranial pressure using lumped-parameter models have adopted the classical "Kellie-Monro Doctrine," which considers the intracranial space to be a closed system that is confined within the nearly-rigid skull, conserves mass, and has equal inflow and outflow. The present work revokes this Doctrine and develops a mathematical model for the dynamics of intracranial pressures, volumes, and flows that embeds the intracranial system in extensive whole-body physiology. The new model consistently introduces compartments representing the tissues and vasculature of the extradural portions of the body, including both the thoracic region and the lower extremities. In addition to vascular connections, a spinal-subarachnoid cerebrospinal fluid (CSF) compartment bridges intracranial and extracranial physiology allowing explict buffering of intracranial pressure fluctuations by the spinal theca. The model contains cerebrovascular autoregulation, regulation of systemic vascular pressures by the sympathetic nervous system, regulation of CSF production in the choroid plexus, a lymphatic system, colloid osmotic pressure effects, and realistic descriptions of cardiac output. To validate the model in situations involving normal physiology, the model's response to a realistic pulsatile cardiac output is examined. A well-known experimentally-derived intracranial pressure-volume relationship is recovered by using the model to simulate CSF infusion tests, and the effect on cerebral blood flow of a change in body position is also examined. Cardiac arrest and hemorrhagic shock are simulated to demonstrate the predictive capabilities of the model in pathological conditions.

Dynamic High Pressure Study of Chemistry and Physics of Molecular Materials

Science.gov (United States)

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

Method for making a dynamic pressure sensor and a pressure sensor made according to the method

Science.gov (United States)

Zuckerwar, Allan J. (Inventor); Robbins, William E. (Inventor); Robins, Glenn M. (Inventor)

1994-01-01

A method for providing a perfectly flat top with a sharp edge on a dynamic pressure sensor using a cup-shaped stretched membrane as a sensing element is described. First, metal is deposited on the membrane and surrounding areas. Next, the side wall of the pressure sensor with the deposited metal is machined to a predetermined size. Finally, deposited metal is removed from the top of the membrane in small steps, by machining or lapping while the pressure sensor is mounted in a jig or the wall of a test object, until the true top surface of the membrane appears. A thin indicator layer having a color contrasting with the color of the membrane may be applied to the top of the membrane before metal is deposited to facilitate the determination of when to stop metal removal from the top surface of the membrane.

Effect of error in crack length measurement on maximum load fracture toughness of Zr-2.5Nb pressure tube material

International Nuclear Information System (INIS)

Bind, A.K.; Sunil, Saurav; Singh, R.N.; Chakravartty, J.K.

2016-03-01

Recently it was found that maximum load toughness (J max ) for Zr-2.5Nb pressure tube material was practically unaffected by error in Δ a . To check the sensitivity of the J max to error in Δ a measurement, the J max was calculated assuming no crack growth up to the maximum load (P max ) for as received and hydrogen charged Zr-2.5Nb pressure tube material. For load up to the P max , the J values calculated assuming no crack growth (J NC ) were slightly higher than that calculated based on Δ a measured using DCPD technique (JDCPD). In general, error in the J calculation found to be increased exponentially with Δ a . The error in J max calculation was increased with an increase in Δ a and a decrease in J max . Based on deformation theory of J, an analytic criterion was developed to check the insensitivity of the J max to error in Δ a . There was very good linear relation was found between the J max calculated based on Δ a measured using DCPD technique and the J max calculated assuming no crack growth. This relation will be very useful to calculate J max without measuring the crack growth during fracture test especially for irradiated material. (author)

Effect of high pressure on the relaxation dynamics of glass-forming liquids

Energy Technology Data Exchange (ETDEWEB)

Paluch, M; Grzybowska, K; Grzybowski, A [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland)

2007-05-23

A glass is usually formed by cooling a liquid at a rate sufficient to avoid crystallization. In the vicinity of the glass transition the structural relaxation time increases with lowering temperature in a non-Arrhenius fashion and the structural relaxation function reveals a non-Debye behaviour. However, liquid can be also vitrified by keeping it at a constant temperature and increasing the pressure. This pressure-induced transition to the glassy state is also accompanied by dramatic changes in the relaxation dynamics. Herein we discuss the behaviour of the structural relaxation times of glass-forming liquids and polymer melts under high pressure.

Effect of high pressure on the relaxation dynamics of glass-forming liquids

International Nuclear Information System (INIS)

Paluch, M; Grzybowska, K; Grzybowski, A

2007-01-01

A glass is usually formed by cooling a liquid at a rate sufficient to avoid crystallization. In the vicinity of the glass transition the structural relaxation time increases with lowering temperature in a non-Arrhenius fashion and the structural relaxation function reveals a non-Debye behaviour. However, liquid can be also vitrified by keeping it at a constant temperature and increasing the pressure. This pressure-induced transition to the glassy state is also accompanied by dramatic changes in the relaxation dynamics. Herein we discuss the behaviour of the structural relaxation times of glass-forming liquids and polymer melts under high pressure

Magnetosheath waves under very low solar wind dynamic pressure: Wind/Geotail observations

Directory of Open Access Journals (Sweden)

C. J. Farrugia

2005-06-01

Full Text Available The expanded bow shock on and around "the day the solar wind almost disappeared" (11 May 1999 allowed the Geotail spacecraft to make a practically uninterrupted 54-h-long magnetosheath pass near dusk (16:30-21:11 magnetic local time at a radial distance of 24 to 30 RE (Earth radii. During most of this period, interplanetary parameters varied gradually and in such a way as to give rise to two extreme magnetosheath structures, one dominated by magnetohydrodynamic (MHD effects and the other by gas dynamic effects. We focus attention on unusual features of electromagnetic ion wave activity in the former magnetosheath state, and compare these features with those in the latter. Magnetic fluctuations in the gas dynamic magnetosheath were dominated by compressional mirror mode waves, and left- and right-hand polarized electromagnetic ion cyclotron (EIC waves transverse to the background field. In contrast, the MHD magnetosheath, lasting for over one day, was devoid of mirror oscillations and permeated instead by EIC waves of weak intensity. The weak wave intensity is related to the prevailing low solar wind dynamic pressures. Left-hand polarized EIC waves were replaced by bursts of right-hand polarized waves, which remained for many hours the only ion wave activity present. This activity occurred when the magnetosheath proton temperature anisotropy (= became negative. This was because the weakened bow shock exposed the magnetosheath directly to the (negative temperature anisotropy of the solar wind. Unlike the normal case studied in the literature, these right-hand waves were not by-products of left-hand polarized waves but derived their energy source directly from the magnetosheath temperature anisotropy. Brief entries into the low latitude boundary layer (LLBL and duskside magnetosphere occurred under such inflated conditions that the magnetospheric magnetic pressure was insufficient to maintain pressure balance. In these crossings, the inner edge of

Maximum respiratory pressure measuring system : calibration and evaluation of uncertainty

NARCIS (Netherlands)

Ferreira, J.L.; Pereira, N.C.; Oliveira Júnior, M.; Vasconcelos, F.H.; Parreira, V.F.; Tierra-Criollo, C.J.

2010-01-01

The objective of this paper is to present a methodology for the evaluation of uncertainties in the measurements results obtained during the calibration of a digital manovacuometer prototype (DM) with a load cell sensor pressure device incorporated. Calibration curves were obtained for both pressure

Modeling the Effect of Fluid-Structure Interaction on the Impact Dynamics of Pressurized Tank Cars

Science.gov (United States)

2009-11-13

This paper presents a computational framework that : analyzes the effect of fluid-structure interaction (FSI) on the : impact dynamics of pressurized commodity tank cars using the : nonlinear dynamic finite element code ABAQUS/Explicit. : There exist...

Dynamic association between intraocular pressure and spontaneous pulsations of retinal veins.

Science.gov (United States)

Golzan, S Mojtaba; Graham, Stuart L; Leaney, John; Avolio, Alberto

2011-01-01

The amplitude of spontaneous retinal venous pulsations (SRVP) is known to be affected by intraocular pressure (IOP), retinal venous pressure, and intracranial pressure (ICP). This study characterized SRVPs adjacent to the disc and quantified changes in the amplitude of these pulsations during IOP manipulation in normal subjects. The study included 12 subjects (40 ± 15, 4 females, 8 males). Baseline IOP (range 10-25 mmHg) was measured and SRVP recorded using the dynamic retinal vessel analyzer (DVA). IOP was lowered using aproclonidine 0.5% and measured every 15 min, followed by dynamic recording of SRVP. Two subjects were also tested with timolol 0.5%, and three were treated with a placebo drop. Mean amplitude of SRVP was determined within each sample at the same site. Blood pressure and heart rate were tracked continuously. Amplitude of SRVP decreased in all subjects with reduction of IOP with aproclonidine and timolol. Mean SRVP amplitude was 8.5 ± 6 μm at baseline and reduced to 2.5 ± 1.8 μm after 45 min (p blood pressure, and heart rate did not change significantly from the baseline. Analysis of waveforms showed a slight phase shift only (150 ± 78.5 ms, p = 0.93) between disc veins and adjacent retinal vein. SRVPs in the peripapillary retina have similar waveform characteristics to those at the disc. SRVP amplitudes are reduced by manipulation of IOP downwards with pharmacological intervention. The relationship was consistent in all individuals tested for two classes of drugs and was independent of BP or heart rate changes.

Comparison of Iterative Methods for Computing the Pressure Field in a Dynamic Network Model

DEFF Research Database (Denmark)

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...

Ultrafast dynamics in CeTe{sub 3} near the pressure-induced charge-density-wave transition

Energy Technology Data Exchange (ETDEWEB)

Tauch, Jonas; Obergfell, Manuel [Department of Physics and Center for Applied Photonics, University of Konstanz (Germany); Schaefer, Hanjo [Department of Physics and Center for Applied Photonics, University of Konstanz (Germany); Institute of Physics, Ilmenau University of Technology (Germany); Demsar, Jure [Department of Physics and Center for Applied Photonics, University of Konstanz (Germany); Institute of Physics, Ilmenau University of Technology (Germany); Institute of Physics, Johannes Gutenberg-University Mainz (Germany); Giraldo, Paula; Fisher, Ian R. [Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University (United States); Pashkin, Alexej [Department of Physics and Center for Applied Photonics, University of Konstanz (Germany); Helmholtz-Zentrum Dresden-Rossendorf (Germany)

2015-07-01

Femtosecond pump-probe spectroscopy is an efficient tool for studying ultrafast dynamics in strongly correlated electronic systems, in particular, compounds with a charge-density-wave (CDW) order. Application of external pressure often leads to a suppression of a CDW state due to an impairment of the Fermi surface nesting. We combine time-resolved optical spectroscopy and diamond anvil cell technology to study electron and lattice dynamics in tri-telluride compound CeTe{sub 3}. Around pressures of 4 GPa we observe a gradual vanishing of the relaxation process related to the recombination of the photoexcited quasiparticles. The coherent oscillations of the phonon modes coupled to the CDW order parameter demonstrate even more dramatic suppression with increasing pressure. These observations clearly indicate a transition into the metallic state of CeTe{sub 3} induced by the external pressure.

Process Factors Influence on Cavity Pressure Behavior in Microinjection Moulding

DEFF Research Database (Denmark)

Griffiths, C. A.; Dimov, S. S.; Scholz, S.

2011-01-01

about the filling behavior of different polymer melts. In this paper, a pressure sensor mounted inside a tool cavity was employed to analyse maximum cavity pressure, pressure increase rate during filling and pressure work. The influence of four mu IM parameters, melt temperature, mould temperature......Process monitoring of microinjection moulding (mu IM) is of crucial importance when analysing the effect of different parameter settings on the process and then in assessing its quality. Quality factors related to cavity pressure can provide valuable information about the process dynamics and also......, injection speed, and packing pressure on these three pressure-related process parameters was investigated. A design of experiment study was conducted by moulding a test part, a microfluidic component, in three different polymer materials, PP, ABS, and PC. The results show a similar process behavior for all...

Bifurcation and Nonlinear Dynamic Analysis of Externally Pressurized Double Air Films Bearing System

Directory of Open Access Journals (Sweden)

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.

Effect of high hydrostatic pressure and high dynamic pressure on stability and rheological properties of model oil-in-water emulsions

Science.gov (United States)

Bigikocin, Erman; Mert, Behic; Alpas, Hami

2011-09-01

Both static and dynamic high pressure applications provide interesting modifications in food structures which lead to new product formulations. In this study, the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP), on oil-in-water emulsions were identified and compared. Microfluidization was selected from among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared with the coarse emulsions. The stability of the emulsions was determined comparatively by using an analytical photo-centrifuge device employing novel analysis technology. Whey protein isolate (WPI) in combination with a food polysaccharide (xanthan gum, guar gum or locust bean gum) were used as emulsifying and stabilizing ingredients. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities, leading to distinctive improvements in emulsion stability. On the other hand, improvements in stability obtained with HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations containing higher oil content. Apart from these, HHP treatment was found to be relatively more contributive to the enhancements in viscoelastic properties.

Influence of cerebrovascular resistance on the dynamic relationship between blood pressure and cerebral blood flow in humans.

Science.gov (United States)

Smirl, J D; Tzeng, Y C; Monteleone, B J; Ainslie, P N

2014-06-15

We examined the hypothesis that changes in the cerebrovascular resistance index (CVRi), independent of blood pressure (BP), will influence the dynamic relationship between BP and cerebral blood flow in humans. We altered CVRi with (via controlled hyperventilation) and without [via indomethacin (INDO, 1.2 mg/kg)] changes in PaCO2. Sixteen subjects (12 men, 27 ± 7 yr) were tested on two occasions (INDO and hypocapnia) separated by >48 h. Each test incorporated seated rest (5 min), followed by squat-stand maneuvers to increase BP variability and improve assessment of the pressure-flow dynamics using linear transfer function analysis (TFA). Beat-to-beat BP, middle cerebral artery velocity (MCAv), posterior cerebral artery velocity (PCAv), and end-tidal Pco2 were monitored. Dynamic pressure-flow relations were quantified using TFA between BP and MCAv/PCAv in the very low and low frequencies through the driven squat-stand maneuvers at 0.05 and 0.10 Hz. MCAv and PCAv reductions by INDO and hypocapnia were well matched, and CVRi was comparably elevated (P flow dynamics. These findings are consistent with the concept of CVRi being a key factor that should be considered in the correct interpretation of cerebral pressure-flow dynamics as indexed using TFA metrics. Copyright © 2014 the American Physiological Society.

High pressure phase transition in Zr–Ni binary system: A first principle study

Energy Technology Data Exchange (ETDEWEB)

Mukherjee, Debojyoti, E-mail: debojyoti@barc.gov.in; Sahoo, B.D.; Joshi, K.D.; Gupta, Satish C.

2015-11-05

Total energy calculations have been performed on zirconium–nickel (with 50% nickel by atom) binary system to examine its structural stability under high pressure. The evolutionary structure search method in conjunction with density functional theory based projector augmented wave (PAW) method suggested that at zero pressure an orthorhombic phase with space group symmetry Cmcm is the lowest enthalpy structure, in agreement with the experiments. Further, it has been predicted that upon compression at ∼10 GPa, this structure will transform to a lower symmetry triclinic phase (space group P-1) which will remain stable up to ∼50 GPa, the maximum pressure of the present calculations. To support the results of our static lattice calculations, we performed lattice dynamic calculations also on Cmcm and P-1 structures. Lattice dynamic calculations correctly showed that at ambient condition the Cmcm phase is dynamically stable. Further, these calculations carried around the Cmcm to P-1 transition pressure predicted that the Cmcm phase will become unstable dynamically due to failure of acoustic zone boundary phonons, suggesting that the Cmcm to P-1 transition is phonon driven. For P-1 phase our calculations showed that this structure is dynamically stable not only at high pressures but also at ambient condition, indicating that at pressure lower than 10 GPa this phase could be a metastable structure. Further, we have calculated the elastic constants for both the phase at various pressures. - Highlights: • Pressure induced phonon driven orthorhombic to triclinic phase transformations in Zr–Ni binary system at ∼10 GPa. • Elastic and lattice dynamic stability of orthorhombic and triclinic phase. • Exploitation of evolutionary structure searching method to explore high pressure phase of Zr–Ni material.

Leak detection method for long pipeline based on dynamic pressure and wavelet analysis

Energy Technology Data Exchange (ETDEWEB)

Xu, Bin; Wang, Likun; Wang, Hongchao; Xiong, Min; Yu, Dongliang; Tan, Dongjie [RnD center of PetroChina Pipeline Company, Langfang, Hebei, (China)

2010-07-01

Leaks appear frequently in pipelines, raising the possibility of safety issues. The detection of pipeline leakage is very important for the pipeline industry. This paper investigated a leak detection method on a long pipeline using a dynamic pressure sensor. A new leakage system is proposed based on the measurements obtained from this dynamic pressure sensor. The data were analyzed using the wavelet transformation method. First, the signal provided by the pressure sensor its denoised and then leaks are detected from the presence of singularities in the signal. Field tests were carried out on a product oil pipeline of 94 km length. The in-field test results showed that the minimum ratio of detectable leakage is 0.6 % of throughput and the location error is below 300 m. The response time is less than 120 seconds. This new system has been applied in 5000 km pipelines in China and is proving its efficiency in detecting leak points.

Comprehensive performance analyses and optimization of the irreversible thermodynamic cycle engines (TCE) under maximum power (MP) and maximum power density (MPD) conditions

International Nuclear Information System (INIS)

Gonca, Guven; Sahin, Bahri; Ust, Yasin; Parlak, Adnan

2015-01-01

This paper presents comprehensive performance analyses and comparisons for air-standard irreversible thermodynamic cycle engines (TCE) based on the power output, power density, thermal efficiency, maximum dimensionless power output (MP), maximum dimensionless power density (MPD) and maximum thermal efficiency (MEF) criteria. Internal irreversibility of the cycles occurred during the irreversible-adiabatic processes is considered by using isentropic efficiencies of compression and expansion processes. The performances of the cycles are obtained by using engine design parameters such as isentropic temperature ratio of the compression process, pressure ratio, stroke ratio, cut-off ratio, Miller cycle ratio, exhaust temperature ratio, cycle temperature ratio and cycle pressure ratio. The effects of engine design parameters on the maximum and optimal performances are investigated. - Highlights: • Performance analyses are conducted for irreversible thermodynamic cycle engines. • Comprehensive computations are performed. • Maximum and optimum performances of the engines are shown. • The effects of design parameters on performance and power density are examined. • The results obtained may be guidelines to the engine designers

Prosthetics socket that incorporates an air splint system focusing on dynamic interface pressure.

Science.gov (United States)

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.

Competitive Pressure: Competitive Dynamics as Reactions to Multiple Rivals

OpenAIRE

Zucchini, Leon; Kretschmer, Tobias

2011-01-01

Competitive dynamics research has focused primarily on interactions between dyads of firms. Drawing on the awareness-motivation-capability framework and strategic group theory we extend this by proposing that firms’ actions are influenced by perceived competitive pressure resulting from actions by several rivals. We predict that firms’ action magnitude is influenced by the total number of rival actions accumulating in the market, and that this effect is moderated by strategic group membership...

Self adaptive internal combustion engine control for hydrogen mixtures based on piezoelectric dynamic cylinder pressure transducers

International Nuclear Information System (INIS)

Courteau, R.; Bose, T.K.

2004-01-01

Piezoelectric transducers offer an effective, non-intrusive way to monitor dynamic cylinder pressure in internal combustion engines. Devices dedicated to this purpose are appearing on the market, often in the form of spark plugs with embedded piezo elements. Dynamic cylinder pressure is typically used to provide diagnostic functions, or to help map an engine after it is designed. With the advent of powerful signal processor chips, it is now possible to embed enough computing power in the engine controller to perform auto tuning based on the signals provided by such transducers. Such functionality is very useful if the fuel characteristics vary between fill ups, as is often the case with alternative fuels. We propose here an algorithm for self-adaptive tuning based on a Kalman filter operating on a few selected metrics of the dynamic pressure curve. (author)

Effect of temperature and density fluctuations on the spatially heterogeneous dynamics of glass-forming Van der Waals liquids under high pressure.

Science.gov (United States)

Koperwas, K; Grzybowski, A; Grzybowska, K; Wojnarowska, Z; Sokolov, A P; Paluch, M

2013-09-20

In this Letter, we show how temperature and density fluctuations affect the spatially heterogeneous dynamics at ambient and elevated pressures. By using high-pressure experimental data for van der Waals liquids, we examine contributions of the temperature and density fluctuations to the dynamics heterogeneity. We show that the dynamic heterogeneity decreases significantly with increasing pressure at a constant structural relaxation time (isochronal condition), while the broadening of the relaxation spectrum remains constant. This observation questions the relationship between spectral broadening and dynamic heterogeneity.

The collapsing of multigroup cross sections in optimization problems solved by means of the Pontryagin maximum principle in nuclear reactor dynamics

International Nuclear Information System (INIS)

Anton, V.

1979-12-01

The collapsing formulae for the optimization problems solved by means of the Pontryagin maximum principle in nuclear reactor dynamics are presented. A comparison with the corresponding formulae of the static case is given too. (author)

Identification of Random Dynamic Force Using an Improved Maximum Entropy Regularization Combined with a Novel Conjugate Gradient

Directory of Open Access Journals (Sweden)

ChunPing Ren

2017-01-01

Full Text Available We propose a novel mathematical algorithm to offer a solution for the inverse random dynamic force identification in practical engineering. Dealing with the random dynamic force identification problem using the proposed algorithm, an improved maximum entropy (IME regularization technique is transformed into an unconstrained optimization problem, and a novel conjugate gradient (NCG method was applied to solve the objective function, which was abbreviated as IME-NCG algorithm. The result of IME-NCG algorithm is compared with that of ME, ME-CG, ME-NCG, and IME-CG algorithm; it is found that IME-NCG algorithm is available for identifying the random dynamic force due to smaller root mean-square-error (RMSE, lower restoration time, and fewer iterative steps. Example of engineering application shows that L-curve method is introduced which is better than Generalized Cross Validation (GCV method and is applied to select regularization parameter; thus the proposed algorithm can be helpful to alleviate the ill-conditioned problem in identification of dynamic force and to acquire an optimal solution of inverse problem in practical engineering.

Dynamic osseous scintigraphy in the knee hyper-pressure syndromes

International Nuclear Information System (INIS)

Laurin, J.; Jau, P.; Ferro, L.; Fouque, M.

1997-01-01

This retrospective study of 49 patients, carrying an internal mono-compartmental algic syndrome of the knee, determines the place of the dynamical osseous scintigraphy in three times: in comparison with the pan-goniometry (for 42 of them), in the diagnosis of the hyper-pressure syndrome and in the evaluation of its severity. The vascularization is augmented in 10 patients and the sanguinary pool in 14. Forty eight internal compartments exhibit a tracer hyper-fixation at late times. These anomalies have been classified according to their tibial or condylar localization and intensity, than compared with the pan-goniometric values of the deviation, which in case of a varus, entail an over-pressure risk. These comparisons show a good correlation between the hyper-fixation in the sub-chondral band of the internal tibial plateau and a syndrome of hyper-pressure by deviation in varus, whether this hyper-fixation was moderated and isolated or severe or associated to a condylar image; the intensity of the fixation indicates the severity. The tibial fixation intensity is always superior to that of the rest of compartment, what is essential for the differential diagnosis in case of a simple, without hyper-pressure, arthritis, or other pathology. From this exploration stem 8 osteotomies and 1 prosthesis

Effects of bruxism on the maximum bite force

Directory of Open Access Journals (Sweden)

Todić Jelena T.

2017-01-01

Full Text Available Background/Aim. Bruxism is a parafunctional activity of the masticatory system, which is characterized by clenching or grinding of teeth. The purpose of this study was to determine whether the presence of bruxism has impact on maximum bite force, with particular reference to the potential impact of gender on bite force values. Methods. This study included two groups of subjects: without and with bruxism. The presence of bruxism in the subjects was registered using a specific clinical questionnaire on bruxism and physical examination. The subjects from both groups were submitted to the procedure of measuring the maximum bite pressure and occlusal contact area using a single-sheet pressure-sensitive films (Fuji Prescale MS and HS Film. Maximal bite force was obtained by multiplying maximal bite pressure and occlusal contact area values. Results. The average values of maximal bite force were significantly higher in the subjects with bruxism compared to those without bruxism (p 0.01. Maximal bite force was significantly higher in the males compared to the females in all segments of the research. Conclusion. The presence of bruxism influences the increase in the maximum bite force as shown in this study. Gender is a significant determinant of bite force. Registration of maximum bite force can be used in diagnosing and analysing pathophysiological events during bruxism.

Well posedness and maximum entropy approximation for the dynamics of quantitative traits

KAUST Repository

Boďová , Katarí na; Haskovec, Jan; Markowich, Peter A.

2017-01-01

We study the Fokker–Planck equation derived in the large system limit of the Markovian process describing the dynamics of quantitative traits. The Fokker–Planck equation is posed on a bounded domain and its transport and diffusion coefficients vanish on the domain’s boundary. We first argue that, despite this degeneracy, the standard no-flux boundary condition is valid. We derive the weak formulation of the problem and prove the existence and uniqueness of its solutions by constructing the corresponding contraction semigroup on a suitable function space. Then, we prove that for the parameter regime with high enough mutation rate the problem exhibits a positive spectral gap, which implies exponential convergence to equilibrium.Next, we provide a simple derivation of the so-called Dynamic Maximum Entropy (DynMaxEnt) method for approximation of observables (moments) of the Fokker–Planck solution, which can be interpreted as a nonlinear Galerkin approximation. The limited applicability of the DynMaxEnt method inspires us to introduce its modified version that is valid for the whole range of admissible parameters. Finally, we present several numerical experiments to demonstrate the performance of both the original and modified DynMaxEnt methods. We observe that in the parameter regimes where both methods are valid, the modified one exhibits slightly better approximation properties compared to the original one.

Well posedness and maximum entropy approximation for the dynamics of quantitative traits

KAUST Repository

Boďová, Katarína

2017-11-06

We study the Fokker–Planck equation derived in the large system limit of the Markovian process describing the dynamics of quantitative traits. The Fokker–Planck equation is posed on a bounded domain and its transport and diffusion coefficients vanish on the domain’s boundary. We first argue that, despite this degeneracy, the standard no-flux boundary condition is valid. We derive the weak formulation of the problem and prove the existence and uniqueness of its solutions by constructing the corresponding contraction semigroup on a suitable function space. Then, we prove that for the parameter regime with high enough mutation rate the problem exhibits a positive spectral gap, which implies exponential convergence to equilibrium.Next, we provide a simple derivation of the so-called Dynamic Maximum Entropy (DynMaxEnt) method for approximation of observables (moments) of the Fokker–Planck solution, which can be interpreted as a nonlinear Galerkin approximation. The limited applicability of the DynMaxEnt method inspires us to introduce its modified version that is valid for the whole range of admissible parameters. Finally, we present several numerical experiments to demonstrate the performance of both the original and modified DynMaxEnt methods. We observe that in the parameter regimes where both methods are valid, the modified one exhibits slightly better approximation properties compared to the original one.

Pressure effects on dynamics behavior of multiwall boron nitride nanotubes

Energy Technology Data Exchange (ETDEWEB)

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.

Validation of the dynamic model for a pressurized water reactor

International Nuclear Information System (INIS)

Zwingelstein, Gilles.

1979-01-01

Dynamic model validation is a necessary procedure to assure that the developed empirical or physical models are satisfactorily representing the dynamic behavior of the actual plant during normal or abnormal transients. For small transients, physical models which represent isolated core, isolated steam generator and the overall pressurized water reactor are described. Using data collected during the step power changes that occured during the startup procedures, comparisons of experimental and actual transients are given at 30% and 100% of full power. The agreement between the transients derived from the model and those recorded on the plant indicates that the developed models are well suited for use for functional or control studies

Implications for anomalous mantle pressure and dynamic topography from lithospheric stress patterns in the North Atlantic Realm

Science.gov (United States)

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 <150 m along the coast of south-western Norway and 250-350 m along the coast of East 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 a Pipeline under the Action of Internal Shock Pressure

Science.gov (United States)

Il'gamov, M. A.

2017-11-01

The static and dynamic bending of a pipeline in the vertical plane under the action of its own weight is considered with regard to the interaction of the internal pressure with the curvature of the axial line and the axisymmetric deformation. The pressure consists of a constant and timevarying parts and is assumed to be uniformly distributed over the entire span between the supports. The pipeline reaction to the stepwise increase in the pressure is analyzed in the case where it is possible to determine the exact solution of the problem. The initial stage of bending determined by the smallness of elastic forces as compared to the inertial forces is introduced into the consideration. At this stage, the solution is sought in the form of power series and the law of pressure variation can be arbitrary. This solution provides initial conditions for determining the further process. The duration of the inertial stage is compared with the times of sharp changes of the pressure and the shock waves in fluids. The structure parameters are determined in the case where the shock pressure is accepted only by the inertial forces in the pipeline.

Changes in Land Surface Water Dynamics since the 1990s and Relation to Population Pressure

Science.gov (United States)

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.

A novel method for calculating the dynamic capillary force and correcting the pressure error in micro-tube experiment.

Science.gov (United States)

Wang, Shuoliang; Liu, Pengcheng; Zhao, Hui; Zhang, Yuan

2017-11-29

Micro-tube experiment has been implemented to understand the mechanisms of governing microcosmic fluid percolation and is extensively used in both fields of micro electromechanical engineering and petroleum engineering. The measured pressure difference across the microtube is not equal to the actual pressure difference across the microtube. Taking into account the additional pressure losses between the outlet of the micro tube and the outlet of the entire setup, we propose a new method for predicting the dynamic capillary pressure using the Level-set method. We first demonstrate it is a reliable method for describing microscopic flow by comparing the micro-model flow-test results against the predicted results using the Level-set method. In the proposed approach, Level-set method is applied to predict the pressure distribution along the microtube when the fluids flow along the microtube at a given flow rate; the microtube used in the calculation has the same size as the one used in the experiment. From the simulation results, the pressure difference across a curved interface (i.e., dynamic capillary pressure) can be directly obtained. We also show that dynamic capillary force should be properly evaluated in the micro-tube experiment in order to obtain the actual pressure difference across the microtube.

Studying pressure denaturation of a protein by molecular dynamics simulations.

Science.gov (United States)

Sarupria, Sapna; Ghosh, Tuhin; García, Angel E; Garde, Shekhar

2010-05-15

Many globular proteins unfold when subjected to several kilobars of hydrostatic pressure. This "unfolding-up-on-squeezing" is counter-intuitive in that one expects mechanical compression of proteins with increasing pressure. Molecular simulations have the potential to provide fundamental understanding of pressure effects on proteins. However, the slow kinetics of unfolding, especially at high pressures, eliminates the possibility of its direct observation by molecular dynamics (MD) simulations. Motivated by experimental results-that pressure denatured states are water-swollen, and theoretical results-that water transfer into hydrophobic contacts becomes favorable with increasing pressure, we employ a water insertion method to generate unfolded states of the protein Staphylococcal Nuclease (Snase). Structural characteristics of these unfolded states-their water-swollen nature, retention of secondary structure, and overall compactness-mimic those observed in experiments. Using conformations of folded and unfolded states, we calculate their partial molar volumes in MD simulations and estimate the pressure-dependent free energy of unfolding. The volume of unfolding of Snase is negative (approximately -60 mL/mol at 1 bar) and is relatively insensitive to pressure, leading to its unfolding in the pressure range of 1500-2000 bars. Interestingly, once the protein is sufficiently water swollen, the partial molar volume of the protein appears to be insensitive to further conformational expansion or unfolding. Specifically, water-swollen structures with relatively low radii of gyration have partial molar volume that are similar to that of significantly more unfolded states. We find that the compressibility change on unfolding is negligible, consistent with experiments. We also analyze hydration shell fluctuations to comment on the hydration contributions to protein compressibility. Our study demonstrates the utility of molecular simulations in estimating volumetric properties

46 CFR 197.462 - Pressure vessels and pressure piping.

Science.gov (United States)

2010-10-01

... that each pressure vessel, including each volume tank, cylinder and PVHO, and each pressure piping... tests conducted in accordance with this section shall be either hydrostatic tests or pneumatic tests. (1... times the maximum allowable working pressure. (2) When a pneumatic test is conducted on a pressure...

Molecular-dynamic simulations of the thermophysical properties of hexanitrohexaazaisowurtzitane single crystal at high pressures and temperatures

Science.gov (United States)

Kozlova, S. A.; Gubin, S. A.; Maklashova, I. V.; Selezenev, A. A.

2017-11-01

Molecular dynamic simulations of isothermal compression parameters are performed for a hexanitrohexaazaisowurtzitane single crystal (C6H6O12N12) using a modified ReaxFF-log reactive force field. It is shown that the pressure-compression ratio curve for a single C6H6O12N12 crystal at constant temperature T = 300 K in pressure range P = 0.05-40 GPa is in satisfactory agreement with experimental compression isotherms obtained for a single C6H6O12N12 crystal. Hugoniot molecular-dynamic simulations of the shock-wave hydrostatic compression of a single C6H6O12N12 crystal are performed. Along with Hugoniot temperature-pressure curves, calculated shock-wave pressure-compression ratios for a single C6H6O12N12 crystal are obtained for a wide pressure range of P = 1-40 GPa. It is established that the percussive adiabat obtained for a single C6H6O12N12 crystal is in a good agreement with the experimental data. All calculations are performed using a LAMMPS molecular dynamics simulation software package that provides a ReaxFF-lg reactive force field to support the approach.

High hydrostatic pressure specifically affects molecular dynamics and shape of low-density lipoprotein particles

Science.gov (United States)

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 loads on reactor vessel components by low pressure waves

International Nuclear Information System (INIS)

Benkert, J.; Mika, C.; Stegemann, D.; Valero, M.

1978-01-01

Starting from the conservation theorems for mass and impulses the code DRUWE has been developed enabling the calculation of dynamic loads of the reactor shell on the basis of simplified assumptions for the first period shortly after rupture. According to the RSK-guidelines it can be assumed that the whole weld size is opened within 15 msec. This time-dependent opening of the fractured plane can be taken into account in the computer program. The calculation is composed in a way that for a reactor shell devided into cross and angle sections the local, chronological pressure and strength curves, the total dynamic load as well as the moments acting on the fastenings of the reactor shell can be calculated. As input data only geometrical details concerning the concept of the pressure vessel and its components as well as the effective subcooling of the fluid are needed. By means of several parameters the program can be operated in a way that the results are available in form of listings or diagrams, respectively, but also as card pile for further examinations, e.g. strength analysis. (orig./RW) [de

Separation of Stochastic and Deterministic Information from Seismological Time Series with Nonlinear Dynamics and Maximum Entropy Methods

International Nuclear Information System (INIS)

Gutierrez, Rafael M.; Useche, Gina M.; Buitrago, Elias

2007-01-01

We present a procedure developed to detect stochastic and deterministic information contained in empirical time series, useful to characterize and make models of different aspects of complex phenomena represented by such data. This procedure is applied to a seismological time series to obtain new information to study and understand geological phenomena. We use concepts and methods from nonlinear dynamics and maximum entropy. The mentioned method allows an optimal analysis of the available information

Ultrasonographic assessment of the swelling of the human masseter muscle after static and dynamic activity

DEFF Research Database (Denmark)

Bakke, M; Thomsen, C E; Vilmann, A

1996-01-01

min at maximum (median endurance time 7.1 min). For dynamic activity, the same individuals chewed gum unilaterally until exhaustion or 40 min at maximum (all endured 40 min) with a cycle time of 725 ms, an average load of 9.3% of maximal electromyographic activity (maxEMG) and a peak mean voltage...... analogue scales (VAS) revealed the concomitant occurrence of pain (static 11.9 VAS%; dynamic 5.9 VAS%), and discomfort (static 8.1 VAS%; dynamic 5.9 VAS%), and both sensations decreased to pre-exercise values after 20-min recovery. Systolic blood pressure increased significantly, more during static (12...

Magnetosheath waves under very low solar wind dynamic pressure: Wind/Geotail observations

Directory of Open Access Journals (Sweden)

C. J. Farrugia

2005-06-01

Full Text Available The expanded bow shock on and around "the day the solar wind almost disappeared" (11 May 1999 allowed the Geotail spacecraft to make a practically uninterrupted 54-h-long magnetosheath pass near dusk (16:30-21:11 magnetic local time at a radial distance of 24 to 30 R_E (Earth radii. During most of this period, interplanetary parameters varied gradually and in such a way as to give rise to two extreme magnetosheath structures, one dominated by magnetohydrodynamic (MHD effects and the other by gas dynamic effects. We focus attention on unusual features of electromagnetic ion wave activity in the former magnetosheath state, and compare these features with those in the latter. Magnetic fluctuations in the gas dynamic magnetosheath were dominated by compressional mirror mode waves, and left- and right-hand polarized electromagnetic ion cyclotron (EIC waves transverse to the background field. In contrast, the MHD magnetosheath, lasting for over one day, was devoid of mirror oscillations and permeated instead by EIC waves of weak intensity. The weak wave intensity is related to the prevailing low solar wind dynamic pressures. Left-hand polarized EIC waves were replaced by bursts of right-hand polarized waves, which remained for many hours the only ion wave activity present. This activity occurred when the magnetosheath proton temperature anisotropy (= became negative. This was because the weakened bow shock exposed the magnetosheath directly to the (negative temperature anisotropy of the solar wind. Unlike the normal case studied in the literature, these right-hand waves were not by-products of left-hand polarized waves but derived their energy source directly from the magnetosheath temperature anisotropy. Brief entries into the

The dynamic behavior of pressure during purge process in the anode of a PEM fuel cell

Energy Technology Data Exchange (ETDEWEB)

Gou, Jun; Pei, Pucheng; Wang, Ying [State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084 (China)

2006-11-22

A one-dimensional mathematic computational fluid dynamics model of a proton exchange membrane (PEM) fuel cell is presented in this paper to simulate the transient behavior of hydrogen pressure in the flow field during a typical dynamic process-the purge process. This model accounts for the mechanism of pressure wave transmission in the channels by employing the characteristic line method. A unique parameter-pressure swing, which represents the top value of pressure variation at certain point in the channel during the purge process, is brought up and studied as well as the pressure drop. The pressure distribution along the channel and the pressure drop during the purge process for different operating pressures, lengths of purge time, stoichiometric ratios and current densities are studied. The results indicate that the distributed pressure, pressure drop and pressure swing all increase with the increment of operating pressure. With a high operating pressure a second-falling stage can be seen in the pressure drop profile while with a relatively low operating pressure, a homogeneous distribution of pressure swing can be attained. A long purge time will provide enough time to show the whole part of the pressure drop curve, while only a part of the curve can be attained if a short purge time is adopted, but a relatively uniform distribution of pressure swing will show up at the moment. Compared with the condition of stoichiometric ratio 1, the pressure drop curve decreases more sharply after the top value and the pressure swing displays a more uniform distribution when the ratio is set beyond 1. Different current densities have no apparent influence on the pressure drop and the pressure swing during this transient process. All the distribution rules of related parameters deducted from this study will be helpful for optimizing the purging strategies on vehicles. (author)

CFD modeling of the IRIS pressurizer dynamic

International Nuclear Information System (INIS)

Sanz, Ronny R.; Montesinos, Maria E.; Garcia, Carlos; Bueno, Elizabeth D.; Mazaira, Leorlen R.; Bezerra, Jair L.; Lira, Carlos A.B. Oliveira

2015-01-01

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)

CFD modeling of the IRIS pressurizer dynamic

Energy Technology Data Exchange (ETDEWEB)

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)

MXLKID: a maximum likelihood parameter identifier

International Nuclear Information System (INIS)

Gavel, D.T.

1980-07-01

MXLKID (MaXimum LiKelihood IDentifier) is a computer program designed to identify unknown parameters in a nonlinear dynamic system. Using noisy measurement data from the system, the maximum likelihood identifier computes a likelihood function (LF). Identification of system parameters is accomplished by maximizing the LF with respect to the parameters. The main body of this report briefly summarizes the maximum likelihood technique and gives instructions and examples for running the MXLKID program. MXLKID is implemented LRLTRAN on the CDC7600 computer at LLNL. A detailed mathematical description of the algorithm is given in the appendices. 24 figures, 6 tables

Thermodynamics, maximum power, and the dynamics of preferential river flow structures at the continental scale

Directory of Open Access Journals (Sweden)

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.

Unsteady pressures on a blunt trailing edge measured with an embedded pressure scanner

Science.gov (United States)

Naughton, Jonathan; Nikoueeyan, Pourya; Hind, Michael; Strike, John; Dahland, Matz; Keeter, Steven

2017-11-01

Development of direct-mount pressure scanners can decrease the pneumatic tubing length required to connect the measurement ports to the scanner manifold resulting in improved dynamic range for unsteady pressure measurements. In this work, the performance of a direct-mount pressure scanner for time-resolved pressure measurement is demonstrated in a well-established flow; the pressure fluctuations near the base of flat plate is considered. The additive manufactured model is instrumented with a pressure scanner and flush-mounted high-speed pressure transducers. The configuration of the ports on the model allows for side-by-side comparison of the pressures measured via embedded pneumatic tubing routed to a pressure scanner with that measured by high-speed transducers. Prior to testing, the dynamic response of each embedded pressure port is dynamically calibrated via an in-situ calibration technique. Pressure data is then acquired for fixed angle-of-attack and different dynamic pitching conditions. The dynamic range of the measurements acquired via direct-mount scanner will be compared to those acquired by the high speed transducers for both static and dynamic pitching configurations. The uncertainties associated with Weiner deconvolution are also quantified for the measurements.

The unsaturated flow in porous media with dynamic capillary pressure

Science.gov (United States)

Milišić, Josipa-Pina

2018-05-01

In this paper we consider a degenerate pseudoparabolic equation for the wetting saturation of an unsaturated two-phase flow in porous media with dynamic capillary pressure-saturation relationship where the relaxation parameter depends on the saturation. Following the approach given in [13] the existence of a weak solution is proved using Galerkin approximation and regularization techniques. A priori estimates needed for passing to the limit when the regularization parameter goes to zero are obtained by using appropriate test-functions, motivated by the fact that considered PDE allows a natural generalization of the classical Kullback entropy. Finally, a special care was given in obtaining an estimate of the mixed-derivative term by combining the information from the capillary pressure with the obtained a priori estimates on the saturation.

Study of the high-pressure helium phase diagram using molecular dynamics

International Nuclear Information System (INIS)

Koci, L; Ahuja, R; Belonoshko, A B; Johansson, B

2007-01-01

The rich occurrence of helium and hydrogen in space makes their properties highly interesting. By means of molecular dynamics (MD), we have examined two interatomic potentials for 4 He. Both potentials are demonstrated to reproduce high-pressure solid and liquid equation of state (EOS) data. The EOS, solid-solid transitions and melting at high pressures (P) were studied using a two-phase method. The Buckingham potential shows a good agreement with theoretical and experimental EOS, but does not reproduce experimental melting data. The Aziz potential shows a perfect match with theoretical melting data. We conclude that there is a stable body-centred-cubic (bcc) phase for 4 He at temperatures (T) above 340 K and pressures above 22 GPa for the Buckingham potential, whereas no bcc phase is found for the Aziz potential in the applied PT range

High-Pressure Polymorphism in Orthoamphiboles

Science.gov (United States)

Finkelstein, G. J.; Zhang, D.; Shelton, H.; Dera, P.

2017-12-01

Amphiboles are double-chain silicate minerals that are the structurally hydrated counterpart to single-chain, anhydrous pyroxenes. They may play an important role in the earth as a carrier for volatiles in subduction zones, as well as a generator for seismic anisotropy in the upper mantle. Recent work has described previously unrecognized high-pressure polymorphism at low temperatures in a variety of pyroxene minerals, which may be relevant for the structure and dynamics of thick, cold, subducted slabs. However, high-pressure polymorphism in amphiboles above a few GPa in pressure has not been well explored, and if similar polymorphism to pyroxenes exists in this mineral family, it may affect the extent and depth of volatile transport in amphiboles, as well as their rheological properties. At low temperatures and high pressures, orthopyroxenes undergo crystal structure transitions at lower pressures than clinopyroxenes (10-30 GPa vs. > 50 GPa), so for this study we have investigated polymorphism in the anthophyllite-gedrite (Al-free and Al rich) orthoamphibole solid solution series. Using neon gas-loaded diamond anvil cells, we compressed both phases to a maximum pressure of 31 GPa, and observed transitions to new monoclinic structures in both endmembers. In this presentation, we will discuss the details of these transitions and implications for the earth's interior.

Experimental study on dynamic pipe fracture in consideration of hydropower plant model

Directory of Open Access Journals (Sweden)

Kazumi Ishikawa

2009-12-01

Full Text Available In the case of sudden valve closure, water hammer creates the most powerful pressure and damage to pipeline systems. The best way to protect the pipeline system is to eliminate water hammer. The main reasons for water hammer occurrence are valve closure, high initial velocity, and static pressure. However, it is difficult to eliminate water hammer. Water hammer tends to occur when the valve is being closed. In this study, the pipe fracture caused by static water pressure, gradually increasing pressure, and suddenly increasing pressure were compared experimentally in a breaking PVC test pipe. The quasi-static zone, the dynamic zone, and the transition zone are defined through the results of those experiments, with consideration of the fracture patterns of test pipes and impulses. The maximum pressure results were used to design the pipeline even though it is in the dynamic zone.

Pressure Transient Model of Water-Hydraulic Pipelines with Cavitation

Directory of Open Access Journals (Sweden)

Dan Jiang

2018-03-01

Full Text Available Transient pressure investigation of water-hydraulic pipelines is a challenge in the fluid transmission field, since the flow continuity equation and momentum equation are partial differential, and the vaporous cavitation has high dynamics; the frictional force caused by fluid viscosity is especially uncertain. In this study, due to the different transient pressure dynamics in upstream and downstream pipelines, the finite difference method (FDM is adopted to handle pressure transients with and without cavitation, as well as steady friction and frequency-dependent unsteady friction. Different from the traditional method of characteristics (MOC, the FDM is advantageous in terms of the simple and convenient computation. Furthermore, the mechanism of cavitation growth and collapse are captured both upstream and downstream of the water-hydraulic pipeline, i.e., the cavitation start time, the end time, the duration, the maximum volume, and the corresponding time points. By referring to the experimental results of two previous works, the comparative simulation results of two computation methods are verified in experimental water-hydraulic pipelines, which indicates that the finite difference method shows better data consistency than the MOC.

Dynamic compressive properties obtained from a split Hopkinson pressure bar test of Boryeong shale

Science.gov (United States)

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.

Pressure Regulators as Valves for Saving Compressed Air and their Influence on System Dynamics

Directory of Open Access Journals (Sweden)

Dvořák Lukáš

2015-01-01

Full Text Available Pressure regulators in the field of pneumatic mechanisms can be used as valves for saving compressed air. For example it can be used to reduce the pressure when the piston rod is retracting unloaded and thus it is possible to save some energy. However the problem is that saving valve can significantly affect the dynamics of the pneumatic system. The lower pressure in the piston rod chamber causes extension of time for retraction of the piston rod. This article compare the air consumption experimentally determined and calculated, measured curves of pressure in cylinder chambers and piston speed when saving valve is set up differently.

Pressure Regulators as Valves for Saving Compressed Air and their Influence on System Dynamics

Science.gov (United States)

Dvořák, Lukáš; Fojtášek, Kamil

2015-05-01

Pressure regulators in the field of pneumatic mechanisms can be used as valves for saving compressed air. For example it can be used to reduce the pressure when the piston rod is retracting unloaded and thus it is possible to save some energy. However the problem is that saving valve can significantly affect the dynamics of the pneumatic system. The lower pressure in the piston rod chamber causes extension of time for retraction of the piston rod. This article compare the air consumption experimentally determined and calculated, measured curves of pressure in cylinder chambers and piston speed when saving valve is set up differently.

Novel threshold pressure sensors based on nonlinear dynamics of MEMS resonators

Science.gov (United States)

Hasan, Mohammad H.; Alsaleem, Fadi M.; Ouakad, Hassen M.

2018-06-01

Triggering an alarm in a car for low air-pressure in the tire or tripping an HVAC compressor if the refrigerant pressure is lower than a threshold value are examples for applications where measuring the amount of pressure is not as important as determining if the pressure has exceeded a threshold value for an action to occur. Unfortunately, current technology still relies on analog pressure sensors to perform this functionality by adding a complex interface (extra circuitry, controllers, and/or decision units). In this paper, we demonstrate two new smart tunable-threshold pressure switch concepts that can reduce the complexity of a threshold pressure sensor. The first concept is based on the nonlinear subharmonic resonance of a straight double cantilever microbeam with a proof mass and the other concept is based on the snap-through bi-stability of a clamped-clamped MEMS shallow arch. In both designs, the sensor operation concept is simple. Any actuation performed at a certain pressure lower than a threshold value will activate a nonlinear dynamic behavior (subharmonic resonance or snap-through bi-stability) yielding a large output that would be interpreted as a logic value of ONE, or ON. Once the pressure exceeds the threshold value, the nonlinear response ceases to exist, yielding a small output that would be interpreted as a logic value of ZERO, or OFF. A lumped, single degree of freedom model for the double cantilever beam, that is validated using experimental data, and a continuous beam model for the arch beam, are used to simulate the operation range of the proposed sensors by identifying the relationship between the excitation signal and the critical cut-off pressure.

DYNAMIC TIME HISTORY ANALYSIS OF BLAST RESISTANT DOOR USING BLAST LOAD MODELED AS IMPACT LOAD

Directory of Open Access Journals (Sweden)

Y. A. Pranata

2012-06-01

Full Text Available A blast resistant single door was designed to withstand a 0.91 bar blast pressure and 44 ms blast duration. The analysis was done using Dynamic Time History Analysis using Blast Load modeled as Impact Load for given duration. The material properties used have been modified to accommodate dynamic effects. The analysis was done using dynamic finite element method (fem for time of the blast duration, and the maximum/minimum internal forces and displacement were taken from the time history output, in order to know the behavior under blast load and estimate the safety margin of the door. Results obtained from this research indicated that the maximum z-displacement is 1.709 mm, while in the term of serviceability, the permitted is 25 mm. The maximum reaction force is 73,960 N, while the maximum anchor capacity is 82,069 N. On blast condition, the maximum frame stress is 71.71 MPa, the maximum hinge shear stress is 45.28 MPa. While on rebound condition, the maximum frame stress is 172.11 MPa, the maximum hinge shear stress is 29.46 MPa. The maximum door edge rotation is 0.44 degree, which is not exceed the permitted boundary (1.2 degree. Keywords: Dynamic time history, blast resistant door, single door, finite element method.

Molecular dynamics simulations of the melting curve of NiAl alloy under pressure

OpenAIRE

Wenjin Zhang; Yufeng Peng; Zhongli Liu

2014-01-01

The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fit...

An understanding of human dynamics in urban subway traffic from the Maximum Entropy Principle

Science.gov (United States)

Yong, Nuo; Ni, Shunjiang; Shen, Shifei; Ji, Xuewei

2016-08-01

We studied the distribution of entry time interval in Beijing subway traffic by analyzing the smart card transaction data, and then deduced the probability distribution function of entry time interval based on the Maximum Entropy Principle. Both theoretical derivation and data statistics indicated that the entry time interval obeys power-law distribution with an exponential cutoff. In addition, we pointed out the constraint conditions for the distribution form and discussed how the constraints affect the distribution function. It is speculated that for bursts and heavy tails in human dynamics, when the fitted power exponent is less than 1.0, it cannot be a pure power-law distribution, but with an exponential cutoff, which may be ignored in the previous studies.

Self adaptive internal combustion engine control for hydrogen mixtures based on piezoelectric dynamic cylinder pressure transducers

Energy Technology Data Exchange (ETDEWEB)

Courteau, R.; Bose, T. K. [Universite du Quebec a Trois-Rivieres, Hydrogen Research Institute, Trois-Rivieres, PQ (Canada)

2004-07-01

An algorithm for self-adaptive tuning of an internal combustion engine is proposed, based on a Kalman filter operating on a few selected metrics of the dynamic pressure curve. Piezoelectric transducers are devices to monitor dynamic cylinder pressure; spark plugs with embedded piezo elements are now available to provide diagnostic engine functions. Such transducers are also capable of providing signals to the engine controller to perform auto tuning, a function that is considered very useful particularly in vehicles using alternative fuels whose characteristics frequently show variations between fill-ups. 2 refs., 2 figs.

Dynamic isolation technologies in negative pressure isolation wards

CERN Document Server

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.

Supercooled dynamics of glass-forming liquids and polymers under hydrostatic pressure

Energy Technology Data Exchange (ETDEWEB)

Roland, C M [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States); Hensel-Bielowka, S [Institute of Physics, Silesian University, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Paluch, M [Institute of Physics, Silesian University, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Casalini, R [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States); Chemistry Department, George Mason University, Fairfax, VA 22030 (United States)

2005-06-01

An intriguing problem in condensed matter physics is understanding the glass transition, in particular the dynamics in the equilibrium liquid close to vitrification. Recent advances have been made by using hydrostatic pressure as an experimental variable. These results are reviewed, with an emphasis in the insight provided into the mechanisms underlying the relaxation properties of glass-forming liquids and polymers.

Application of the maximum entropy method to dynamical fermion simulations

Science.gov (United States)

Clowser, Jonathan

This thesis presents results for spectral functions extracted from imaginary-time correlation functions obtained from Monte Carlo simulations using the Maximum Entropy Method (MEM). The advantages this method are (i) no a priori assumptions or parametrisations of the spectral function are needed, (ii) a unique solution exists and (iii) the statistical significance of the resulting image can be quantitatively analysed. The Gross Neveu model in d = 3 spacetime dimensions (GNM3) is a particularly interesting model to study with the MEM because at T = 0 it has a broken phase with a rich spectrum of mesonic bound states and a symmetric phase where there are resonances. Results for the elementary fermion, the Goldstone boson (pion), the sigma, the massive pseudoscalar meson and the symmetric phase resonances are presented. UKQCD Nf = 2 dynamical QCD data is also studied with MEM. Results are compared to those found from the quenched approximation, where the effects of quark loops in the QCD vacuum are neglected, to search for sea-quark effects in the extracted spectral functions. Information has been extract from the difficult axial spatial and scalar as well as the pseudoscalar, vector and axial temporal channels. An estimate for the non-singlet scalar mass in the chiral limit is given which is in agreement with the experimental value of Mao = 985 MeV.

Numerical simulation of the pressure pulses produced by a pressure screen foil rotor

International Nuclear Information System (INIS)

Feng, M.; Ollivier-Gooch, C.; Gooding, R.W.; Olson, J.A.

2003-01-01

Pressure screening is the most industrially efficient and effective means of removing contaminants that degrade the appearance and strength of paper and fractionating fibres for selective treatments and specialty products. A critical design component of a screen is the rotor which produces pressure pulses on the screen cylinder surface to keep the screening apertures clear. To understand the effect of the key design and operating variables for a NACA 0012 foil rotor, a computational fluid dynamic (CFD) simulation tool was developed with FLUENT software, and the numerical results were compared with experimental measurements. The computational results of pressure pulses were shown to be in good agreement with experimental pressure measurements over a wide range of foil tip-speeds, clearances and angles of attack. In addition, it was shown that the magnitude of the pressure pulse peak increases as the rotating speed increases linearly with the square of tip-speed for all the angles of attack studied. The maximum negative pressure pulse occurred for the foil at 5 degrees angle of attack. Flow began to separate from foil surface near the screen plate beyond 10 degrees angle of attack. The positive pressure peak near the leading edge of the foil is completely eliminated for foils operating at a positive angle of attack. The magnitude of the negative pressure peak increased as clearance decreased. In addition to, and more important than, these specific results, we have shown that CFD is a viable tool for the optimal design and operation of rotors in industrial pressure screens. (author)

Direct Numerical Simulations of Dynamic Drainage and Imbibition to Investigate Capillary Pressure-Saturation-Interfacial Area Relation

Science.gov (United States)

Konangi, S.; Palakurthi, N. K.; Karadimitriou, N.; Comer, K.; Ghia, U.

2017-12-01

We present results of pore-scale direct numerical simulations (DNS) of drainage and imbibition in a quasi-two-dimensional (40µm thickness) porous medium with a randomly distributed packing of cylindrical obstructions. The Navier-Stokes (NS) equations are solved in the pore space on an Eulerian mesh using the open-source finite-volume computational fluid dynamics (CFD) code, OpenFOAM. The Volume-of-Fluid (VOF) method is employed to track the evolution of the fluid-fluid interface; a static contact angle is used to account for wall adhesion. From the DNS data, we focus on the macroscopic capillary pressure-saturation (Pc-Sw) relation, which is known to be hysteretic, i.e., this relation is flow process (such as drainage, imbibition and scanning curves) and history dependent. In order to overcome the problem of hysteresis, extended theories of multiphase flow hypothesized that the inclusion of specific interfacial area as a state variable will result in a unique relation between capillary pressure, saturation and interfacial area (Pc-Sw-awn). We study the role of specific interfacial area on hysteresis in the macroscopic Pc-Sw relation under non-equilibrium (dynamic) conditions. Under dynamic conditions, capillary pressure depends on the rate of change of the wetting phase saturation, and the dynamic Pc-Sw relation includes the changes caused by viscous effects. Simulations of drainage and imbibition are performed for two capillary numbers by controlling the flow rate of the non-wetting (polydimenthlysiloxane oil) and wetting (water) fluids. From these simulations, the Pc-Sw curves will be estimated; the Pc-S-awn surface will be constructed to determine whether the data points from drainage and imbibition processes fall on a unique surface under transient conditions. Different macroscopic capillary pressure definitions based on phase-averaged pressures and interfacial area will be evaluated. Understanding macroscopic capillary pressure definitions and the uniqueness

[Spasticity and dynamic plantar pressure distribution measurements in hemiplegic spastic children].

Science.gov (United States)

Femery, V; Moretto, P; Renaut, H; Thévenon, A

2001-02-01

The aim of this study was to analyse the plantar pressure distribution in nine hemiplegic spastic children to illustrate the dynamic alteration during stance phase linked spasticity grade. The graduation of the lower limbs muscle tone related to the Aschworth spasticity scale enabled us to identify two groups of hemiplegics subjects. The groups Asch 1 and Asch 3 have respectively presented a low and a strong spasticity. The peak pressures during consecutive gait cycles were determined under the feet of 30 healthy subjects and two cerebral palsy groups using a wearable footprint analysis system. A statistical study showed a similarity between the two disabled groups. Peak pressures under the midfoot were significantly higher compared to the control group. While the plantar pressure distribution profile was specific for each group under all other anatomical structures. The significant alterations were observed under the forefoot and hallux. Spasticity modifies the foot contact to ground and leads to a specific plantar pressure distribution profile linked to the spasticity grade. The equinovarus with clawed toes deformity due to higher spasticity seems to be an important factor in terminal stance phase perturbations. However spastic hemiplegic subjects seem to adopt a gait pattern in agreement with stability optimization criteria.

High performance monolithic power management system with dynamic maximum power point tracking for microbial fuel cells.

Science.gov (United States)

Erbay, Celal; Carreon-Bautista, Salvador; Sanchez-Sinencio, Edgar; Han, Arum

2014-12-02

Microbial fuel cell (MFC) that can directly generate electricity from organic waste or biomass is a promising renewable and clean technology. However, low power and low voltage output of MFCs typically do not allow directly operating most electrical applications, whether it is supplementing electricity to wastewater treatment plants or for powering autonomous wireless sensor networks. Power management systems (PMSs) can overcome this limitation by boosting the MFC output voltage and managing the power for maximum efficiency. We present a monolithic low-power-consuming PMS integrated circuit (IC) chip capable of dynamic maximum power point tracking (MPPT) to maximize the extracted power from MFCs, regardless of the power and voltage fluctuations from MFCs over time. The proposed PMS continuously detects the maximum power point (MPP) of the MFC and matches the load impedance of the PMS for maximum efficiency. The system also operates autonomously by directly drawing power from the MFC itself without any external power. The overall system efficiency, defined as the ratio between input energy from the MFC and output energy stored into the supercapacitor of the PMS, was 30%. As a demonstration, the PMS connected to a 240 mL two-chamber MFC (generating 0.4 V and 512 μW at MPP) successfully powered a wireless temperature sensor that requires a voltage of 2.5 V and consumes power of 85 mW each time it transmit the sensor data, and successfully transmitted a sensor reading every 7.5 min. The PMS also efficiently managed the power output of a lower-power producing MFC, demonstrating that the PMS works efficiently at various MFC power output level.

Determination of Secondary Encasement Pipe Design Pressure

Energy Technology Data Exchange (ETDEWEB)

TEDESCHI, A.R.

2000-10-26

This document published results of iterative calculations for maximum tank farm transfer secondary pipe (encasement) pressure upon failure of the primary pipe. The maximum pressure was calculated from a primary pipe guillotine break. Results show encasement pipeline design or testing pressures can be significantly lower than primary pipe pressure criteria.

Maximum phytoplankton concentrations in the sea

DEFF Research Database (Denmark)

Jackson, G.A.; Kiørboe, Thomas

2008-01-01

A simplification of plankton dynamics using coagulation theory provides predictions of the maximum algal concentration sustainable in aquatic systems. These predictions have previously been tested successfully against results from iron fertilization experiments. We extend the test to data collect...

Dynamical reconstruction of the global ocean state during the Last Glacial Maximum

Science.gov (United States)

Kurahashi-Nakamura, Takasumi; Paul, André; Losch, Martin

2017-04-01

The global ocean state for the modern age and for the Last Glacial Maximum (LGM) was dynamically reconstructed with a sophisticated data assimilation technique. A substantial amount of data including global seawater temperature, salinity (only for the modern estimate), and the isotopic composition of oxygen and carbon (only in the Atlantic for the LGM) were integrated into an ocean general circulation model with the help of the adjoint method, thereby the model was optimized to reconstruct plausible continuous fields of tracers, overturning circulation and water mass distribution. The adjoint-based LGM state estimation of this study represents the state of the art in terms of the length of forward model runs, the number of observations assimilated, and the model domain. Compared to the modern state, the reconstructed continuous sea-surface temperature field for the LGM shows a global-mean cooling of 2.2 K, and the reconstructed LGM ocean has a more vigorous Atlantic meridional overturning circulation, shallower North Atlantic Deep Water (NADW) equivalent, stronger stratification, and more saline deep water.

The Maximum Flux of Star-Forming Galaxies

Science.gov (United States)

Crocker, Roland M.; Krumholz, Mark R.; Thompson, Todd A.; Clutterbuck, Julie

2018-04-01

The importance of radiation pressure feedback in galaxy formation has been extensively debated over the last decade. The regime of greatest uncertainty is in the most actively star-forming galaxies, where large dust columns can potentially produce a dust-reprocessed infrared radiation field with enough pressure to drive turbulence or eject material. Here we derive the conditions under which a self-gravitating, mixed gas-star disc can remain hydrostatic despite trapped radiation pressure. Consistently taking into account the self-gravity of the medium, the star- and dust-to-gas ratios, and the effects of turbulent motions not driven by radiation, we show that galaxies can achieve a maximum Eddington-limited star formation rate per unit area \\dot{Σ }_*,crit ˜ 10^3 M_{⊙} pc-2 Myr-1, corresponding to a critical flux of F*, crit ˜ 1013L⊙ kpc-2 similar to previous estimates; higher fluxes eject mass in bulk, halting further star formation. Conversely, we show that in galaxies below this limit, our one-dimensional models imply simple vertical hydrostatic equilibrium and that radiation pressure is ineffective at driving turbulence or ejecting matter. Because the vast majority of star-forming galaxies lie below the maximum limit for typical dust-to-gas ratios, we conclude that infrared radiation pressure is likely unimportant for all but the most extreme systems on galaxy-wide scales. Thus, while radiation pressure does not explain the Kennicutt-Schmidt relation, it does impose an upper truncation on it. Our predicted truncation is in good agreement with the highest observed gas and star formation rate surface densities found both locally and at high redshift.

Dynamic elastic moduli of rocks under pressure

Energy Technology Data Exchange (ETDEWEB)

Schock, R N [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

1970-05-01

Elastic moduli are determined as a function of confining pressure to 10 kb on rocks in which Plowshare shots are to be fired. Numerical simulation codes require accurate information on the mechanical response of the rock medium to various stress levels in order to predict cavity dimensions. The theoretical treatment of small strains in an elastic medium relates the propagation velocity of compressional and shear waves to the elastic moduli. Velocity measurements can provide, as unique code input data, the rigidity modulus, Poisson' ratio and the shear wave velocity, as well as providing checks on independent determinations of the other moduli. Velocities are determined using pulsed electro-mechanical transducers and measuring the time-of-flight in the rock specimen. A resonant frequency of 1 MHz is used to insure that the wavelength exceeds the average grain dimension and is subject to bulk rock properties. Data obtained on a variety of rock types are presented and analyzed. These data are discussed in terms of their relationship to moduli measured by static methods as well as the effect of anisotropy, porosity, and fractures. In general, fractured rocks with incipient cracks show large increases in velocity and moduli in the first 1 to 2 kb of compression as a result of the closing of these voids. After this, the velocities increase much more slowly. Dynamic moduli for these rocks are often 10% higher than corresponding static moduli at low pressure, but this difference decreases as the voids are closed until the moduli agree within experimental error. The discrepancy at low pressure is a result of the elastic energy in the wave pulse being propagated around cracks, with little effect on propagation velocity averaged over the entire specimen. (author)

Dynamic elastic moduli of rocks under pressure

International Nuclear Information System (INIS)

Schock, R.N.

1970-01-01

Elastic moduli are determined as a function of confining pressure to 10 kb on rocks in which Plowshare shots are to be fired. Numerical simulation codes require accurate information on the mechanical response of the rock medium to various stress levels in order to predict cavity dimensions. The theoretical treatment of small strains in an elastic medium relates the propagation velocity of compressional and shear waves to the elastic moduli. Velocity measurements can provide, as unique code input data, the rigidity modulus, Poisson' ratio and the shear wave velocity, as well as providing checks on independent determinations of the other moduli. Velocities are determined using pulsed electro-mechanical transducers and measuring the time-of-flight in the rock specimen. A resonant frequency of 1 MHz is used to insure that the wavelength exceeds the average grain dimension and is subject to bulk rock properties. Data obtained on a variety of rock types are presented and analyzed. These data are discussed in terms of their relationship to moduli measured by static methods as well as the effect of anisotropy, porosity, and fractures. In general, fractured rocks with incipient cracks show large increases in velocity and moduli in the first 1 to 2 kb of compression as a result of the closing of these voids. After this, the velocities increase much more slowly. Dynamic moduli for these rocks are often 10% higher than corresponding static moduli at low pressure, but this difference decreases as the voids are closed until the moduli agree within experimental error. The discrepancy at low pressure is a result of the elastic energy in the wave pulse being propagated around cracks, with little effect on propagation velocity averaged over the entire specimen. (author)

Dynamic Increase Factors for High Performance Concrete in Compression using Split Hopkinson Pressure Bar

DEFF Research Database (Denmark)

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....

Optimal Control as a method for Diesel engine efficiency assessment including pressure and NO_x constraints

International Nuclear Information System (INIS)

Guardiola, Carlos; Climent, Héctor; Pla, Benjamín; Reig, Alberto

2017-01-01

Highlights: • Optimal Control is applied for heat release shaping in internal combustion engines. • Optimal Control allows to assess the engine performance with a realistic reference. • The proposed method gives a target heat release law to define control strategies. - Abstract: The present paper studies the optimal heat release law in a Diesel engine to maximise the indicated efficiency subject to different constraints, namely: maximum cylinder pressure, maximum cylinder pressure derivative, and NO_x emission restrictions. With this objective, a simple but also representative model of the combustion process has been implemented. The model consists of a 0D energy balance model aimed to provide the pressure and temperature evolutions in the high pressure loop of the engine thermodynamic cycle from the gas conditions at the intake valve closing and the heat release law. The gas pressure and temperature evolutions allow to compute the engine efficiency and NO_x emissions. The comparison between model and experimental results shows that despite the model simplicity, it is able to reproduce the engine efficiency and NO_x emissions. After the model identification and validation, the optimal control problem is posed and solved by means of Dynamic Programming (DP). Also, if only pressure constraints are considered, the paper proposes a solution that reduces the computation cost of the DP strategy in two orders of magnitude for the case being analysed. The solution provides a target heat release law to define injection strategies but also a more realistic maximum efficiency boundary than the ideal thermodynamic cycles usually employed to estimate the maximum engine efficiency.

Experimental investigation of dynamic compression and spallation of Cerium at pressures up to 6 GPa

Science.gov (United States)

Zubareva, A. N.; Kolesnikov, S. A.; Utkin, A. V.

2014-05-01

In this study the experiments on one-dimensional dynamic compression of Cerium (Ce) samples to pressures of 0.5 to 6 GPa using various types of explosively driven generators were conducted. VISAR laser velocimeter was used to obtain Ce free surface velocity profiles. The isentropic compression wave was registered for γ-phase of Ce at pressures lower than 0.76 GPa that corresponds to γ-α phase transition pressure in Ce. Shock rarefaction waves were also registered in several experiments. Both observations were the result of the anomalous compressibility of γ-phase of Ce. On the basis of our experimental results the compression isentrope of Ce γ-phase was constructed. Its comparison with volumetric compression curves allowed to estimate the magnitude of shear stress at dynamic compression conditions for Ce. Spall strength measurements were also conducted for several samples. They showed a strong dependence of the spall strength of Ce on the strain rate.

Experimental investigation of dynamic compression and spallation of cerium at pressures up to 6 GPa

International Nuclear Information System (INIS)

Zubareva, A N; Kolesnikov, S A; Utkin, A V

2014-01-01

In this study the experiments on one-dimensional dynamic compression of Cerium (Ce) samples to pressures of 0.5 to 6 GPa using various types of explosively driven generators were conducted. VISAR laser velocimeter was used to obtain Ce free surface velocity profiles. The isentropic compression wave was registered for γ-phase of Ce at pressures lower than 0.76 GPa that corresponds to γ-α phase transition pressure in Ce. Shock rarefaction waves were also registered in several experiments. Both observations were the result of the anomalous compressibility of γ-phase of Ce. On the basis of our experimental results the compression isentrope of Ce γ-phase was constructed. Its comparison with volumetric compression curves allowed to estimate the magnitude of shear stress at dynamic compression conditions for Ce. Spall strength measurements were also conducted for several samples. They showed a strong dependence of the spall strength of Ce on the strain rate.

Effects of the van der Waals Force on the Dynamics Performance for a Micro Resonant Pressure Sensor

Directory of Open Access Journals (Sweden)

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.

Study of the effect of composition and construction of material on sub-bandage pressure during dynamic loading of a limb in vitro.

Science.gov (United States)

Kumar, Bipin; Das, Apurba; Alagirusamy, R

2013-01-01

Internal stress in a compression bandage wrapped over a limb in vitro is expected to reduce over time because of fatigue which may occur due to repetitive and prolonged variations in the extension of the bandage during posture change and exercise. This phenomenon may cause significant variation in the sub-bandage pressure over time. To examine the effect of composition and construction of material on the sub-bandage pressure variation over time in the dynamic state of a limb in the laboratory. Yarns comprising fibers of polyester, viscose, cotton and elastomeric yarn were used to prepare different knitted bandage samples having varying thread densities in the structure. A leg-segment prototype was used for the measurement of the interface pressure over a mannequin limb to analyse different bandages under similar dynamic conditions. The pressure drop in the dynamic state of the mannequin limb was greater than that in the static state. The mean pressure drop in 2 h in the dynamic state was greater by >30% for bandages made of pure cotton or viscose yarns than for bandages having elastomeric yarns in their structure. At the same applied tension, increasing the number of yarns per unit length in the bandage structure resulted in a smaller drop in pressure in the dynamic mode. Elastomeric yarn improves the elasticity and fatigue resistance of the bandage. Therefore, these yarns should be used in bandages to obtain sustained compression effects under dynamic conditions.

On the dynamic response of pressure transmission lines in the research of helium-charged free piston Stirling engines

Science.gov (United States)

Miller, Eric L.; Dudenhoefer, James E.

1989-01-01

The signal distortion inherent to pressure transmission lines in free-piston Stirling engine research is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving the helium-charged free-piston Stirling engines. The underdamped flow regime is described, the primary resonance frequency is derived, and the pressure phase and amplitude distortion are discussed. The scope and limitation of the dynamic response analysis are considered.

Introduction of the bubble rise dynamic model into the ALMOD 3 code pressurizer

International Nuclear Information System (INIS)

Madeira, A.A.; Camargo, C.T.M.

1985-01-01

A new evaporation model for the ALMOD 3 code pressurizer is implemented in order to estimate more accurately the water level behaviour and its influence in the pressure transient for very fast depressurization cases. For the inclusion of the bubble rise dynamic model it was necessary to consider a two-phase mixture in the water volume. The modifications don't require additional input data and virtually had not modified the processing time. The results and processing time for the original and the new models are presented. (F.E.) [pt

The dynamic relaxation method in the structural analysis of concrete pressure vessels

International Nuclear Information System (INIS)

Davidson, I.; Assis Bastos, M.R. de; Camargo, P.B. de.

1977-01-01

The dynamic relaxation method, applied to 3 dimensional concrete structures, especially pressure vessels, is demonstrated. It utilizes the finite difference method and allows the growth of cracks to be followed up to the point of vessel rupture. A FORTRAN IV program is developed, which can also be utilized, with the necessary modifications, for other structure calculations [pt

Peer pressure is a double-edged sword in vaccination dynamics

Science.gov (United States)

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.

Burst pressure investigation of filament wound type IV composite pressure vessel

Science.gov (United States)

Farhood, Naseer H.; Karuppanan, Saravanan; Ya, H. H.; Baharom, Mohamad Ariff

2017-12-01

Currently, composite pressure vessels (PVs) are employed in many industries such as aerospace, transportations, medical etc. Basically, the use of PVs in automotive application as a compressed natural gas (CNG) storage cylinder has been growing rapidly. Burst failure due to the laminate failure is the most critical failure mechanism for composite pressure vessels. It is predominantly caused by excessive internal pressure due to an overfilling or an overheating. In order to reduce fabrication difficulties and increase the structural efficiency, researches and studies are conducted continuously towards the proper selection of vessel design parameters. Hence, this paper is focused on the prediction of first ply failure pressure for such vessels utilizing finite element simulation based on Tsai-Wu and maximum stress failure criterions. The effects of laminate stacking sequence and orientation angle on the burst pressure were investigated in this work for a constant layered thickness PV. Two types of winding design, A [90°2/∓θ16/90°2] and B [90°2/∓θ]ns with different orientations of helical winding reinforcement were analyzed for carbon/epoxy composite material. It was found that laminate A sustained a maximum burst pressure of 55 MPa for a sequence of [90°2/∓15°16/90°2] while the laminate B returned a maximum burst pressure of 45 MPa corresponding to a stacking sequence of [90°2/±15°/90°2/±15°/90°2/±15° ....] up to 20 layers for a constant vessel thickness. For verification, a comparison was done with the literature under similar conditions of analysis and good agreement was achieved with a maximum difference of 4% and 10% for symmetrical and unsymmetrical layout, respectively.

Neutral particle dynamics in the Alcator C-Mod tokamak

Energy Technology Data Exchange (ETDEWEB)

Niemczewski, Artur P. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

1995-08-01

This thesis presents an experimental study of neutral particle dynamics in the Alcator C-Mod tokamak. The primary diagnostic used is a set of six neutral pressure gauges, including special-purpose gauges built for in situ tokamak operation. While a low main chamber neutral pressure coincides with high plasma confinement regimes, high divertor pressure is required for heat and particle flux dispersion in future devices such as ITER. Thus we examine conditions that optimize divertor compression, defined here as a divertor-to-midplane pressure ratio. We find both pressures depend primarily on the edge plasma regimes defined by the scrape-off-layer heat transport. While the maximum divertor pressure is achieved at high core plasma densities corresponding to the detached divertor state, the maximum compression is achieved in the high-recycling regime. Variations in the divertor geometry have a weaker effect on the neutral pressures. For otherwise similar plasmas the divertor pressure and compression are maximum when the strike point is at the bottom of the vertical target plate. We introduce a simple flux balance model, which allows us to explain the divertor neutral pressure across a wide range of plasma densities. In particular, high pressure sustained in the detached divertor (despite a considerable drop in the recycling source) can be explained by scattering of neutrals off the cold plasma plugging the divertor throat. Because neutrals are confined in the divertor through scattering and ionization processes (provided the mean-free-paths are much shorter than a typical escape distance) tight mechanical baffling is unnecessary. The analysis suggests that two simple structural modifications may increase the divertor compression in Alcator C-Mod by a factor of about 5. Widening the divertor throat would increase the divertor recycling source, while closing leaks in the divertor structure would eliminate a significant neutral loss mechanism.

Neutral particle dynamics in the Alcator C-Mod tokamak

International Nuclear Information System (INIS)

Niemczewski, A.P.

1995-08-01

This thesis presents an experimental study of neutral particle dynamics in the Alcator C-Mod tokamak. The primary diagnostic used is a set of six neutral pressure gauges, including special-purpose gauges built for in situ tokamak operation. While a low main chamber neutral pressure coincides with high plasma confinement regimes, high divertor pressure is required for heat and particle flux dispersion in future devices such as ITER. Thus we examine conditions that optimize divertor compression, defined here as a divertor-to-midplane pressure ratio. We find both pressures depend primarily on the edge plasma regimes defined by the scrape-off-layer heat transport. While the maximum divertor pressure is achieved at high core plasma densities corresponding to the detached divertor state, the maximum compression is achieved in the high-recycling regime. Variations in the divertor geometry have a weaker effect on the neutral pressures. For otherwise similar plasmas the divertor pressure and compression are maximum when the strike point is at the bottom of the vertical target plate. We introduce a simple flux balance model, which allows us to explain the divertor neutral pressure across a wide range of plasma densities. In particular, high pressure sustained in the detached divertor (despite a considerable drop in the recycling source) can be explained by scattering of neutrals off the cold plasma plugging the divertor throat. Because neutrals are confined in the divertor through scattering and ionization processes (provided the mean-free-paths are much shorter than a typical escape distance) tight mechanical baffling is unnecessary. The analysis suggests that two simple structural modifications may increase the divertor compression in Alcator C-Mod by a factor of about 5. Widening the divertor throat would increase the divertor recycling source, while closing leaks in the divertor structure would eliminate a significant neutral loss mechanism. 146 refs., 82 figs., 14 tabs

Nonlinear Dynamic Response of Compliant Journal Bearings

Directory of Open Access Journals (Sweden)

Glavatskih S.

2012-07-01

Full Text Available This paper investigates the dynamic response of the compliant tilting pad journal bearings subjected to synchronous excitation. Bearing compliance is affected by the properties of pad liner and pad support geometry. Different unbalance eccentricities are considered. It is shown that bearing dynamic response is non-linear. Journal orbit complexity increases with pad compliance though the orbit amplitudes are marginally affected at low loads. At high loads, the journal is forced to operate outside the bearing clearance. The polymer liner reduces the maximum oil film pressure by a factor of 2 when compared to the white metal liner. The nonlinear dynamic response of compliant tilting pad journal bearings is thoroughly discussed.

Equations of states for an ionic liquid under high pressure: A molecular dynamics simulation study

International Nuclear Information System (INIS)

Ribeiro, Mauro C.C.; Pádua, Agílio A.H.; Gomes, Margarida F.C.

2014-01-01

Highlights: • We compare different equation of states, EoS, for an ionic liquid under high pressure. • Molecular dynamics, MD, simulations have been used to evaluate the best EoS. • MD simulations show that a group contribution model can be extrapolated to P ∼ 1.0 GPa. • A perturbed hard-sphere EoS also fits the densities calculated by MD simulations. - Abstract: The high-pressure dependence of density given by empirical equation of states (EoS) for the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate (or triflate), [C 4 C 1 im][TfO], is compared with results obtained by molecular dynamics (MD) simulations. Two EoS proposed for [C 4 C 1 im][TfO] in the pressure range of tens of MPa, which give very different densities when extrapolated to pressures beyond the original experiments, are compared with a group contribution model (GCM). The MD simulations provide support that one of the empirical EoS and the GCM is valid in the pressure range of hundreds of MPa. As an alternative to these EoS that are based on modified Tait equations, it is shown that a perturbed hard-sphere EoS based on the Carnahan–Starling–van der Waals equation also fits the densities calculated by MD simulations of [C 4 C 1 im][TfO] up to ∼1.0 GPa

Probabilistic modelling of the high-pressure arc cathode spot displacement dynamic

CERN Document Server

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...

Safety of 5 MW district heating reactor (DHR) and hydraulic dynamic pressure drive control rods

International Nuclear Information System (INIS)

Wu Yuanqiang; Wang Dazhong

1991-11-01

The principles and movement characteristic of the hydraulic dynamic pressure drive for control rods in 5 MW district heating reactor are described with stress on analysis of its effects on reactor safety features. The drive is different from electric-magnetic drive for PWR or hydraulic drive for BWR. The drive cylinder is driven by dynamic pressure. In the new drive system, the reactor coolant (water) used as actuating medium is pressed by pump, then injected into a step cylinder which is set in the reactor core. The cylinder will move step by step by controlling flow, then the cylinder drives the neutron absorber and controls nuclear reaction. The drive is characterized by simplicity in structure, high reliability, inherent safety, reduction in reactor height, economy, etc

Effect of the dynamic pressure on the shock wave structure in a rarefied polyatomic gas

Energy Technology Data Exchange (ETDEWEB)

Taniguchi, Shigeru, E-mail: taniguchi@stat.nitech.ac.jp; Sugiyama, Masaru, E-mail: sugiyama@nitech.ac.jp [Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Arima, Takashi, E-mail: tks@stat.nitech.ac.jp [Center for Social Contribution and Collaboration, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Ruggeri, Tommaso, E-mail: tommaso.ruggeri@unibo.it [Department of Mathematics and Research Center of Applied Mathematics (CIRAM), University of Bologna, Bologna (Italy)

2014-01-15

We study the shock wave structure in a rarefied polyatomic gas based on a simplified model of extended thermodynamics in which the dissipation is due only to the dynamic pressure. In this case the differential system is very simple because it is a variant of Euler system with a new scalar equation for the dynamic pressure [T. Arima, S. Taniguchi, T. Ruggeri, and M. Sugiyama, Phys. Lett. A 376, 2799–2803 (2012)]. It is shown that this theory is able to describe the three types of the shock wave structure observed in experiments: the nearly symmetric shock wave structure (Type A, small Mach number), the asymmetric structure (Type B, moderate Mach number), and the structure composed of thin and thick layers (Type C, large Mach number)

Automated processing of dynamic properties of intraventricular pressure by computer program and electronic circuit.

Science.gov (United States)

Adler, D; Mahler, Y

1980-04-01

A procedure for automatic detection and digital processing of the maximum first derivative of the intraventricular pressure (dp/dtmax), time to dp/dtmax(t - dp/dt) and beat-to-beat intervals have been developed. The procedure integrates simple electronic circuits with a short program using a simple algorithm for the detection of the points of interest. The tasks of differentiating the pressure signal and detecting the onset of contraction were done by electronics, while the tasks of finding the values of dp/dtmax, t - dp/dt, beat-to-beat intervals and all computations needed were done by software. Software/hardware 'trade off' considerations and the accuracy and reliability of the system are discussed.

Dynamics of Passive Lateral Pressure in Granular Mass during Discontinual Movement of Retaining Structure

Czech Academy of Sciences Publication Activity Database

Koudelka, Petr; Valach, Jaroslav

2006-01-01

Roč. 10, I (2006), s. 271-276 ISSN 1335-2393. [ICE Experimental stress analysis 2006. Červený Kláštor, xx.06.2006] R&D Projects: GA ČR(CZ) GA103/05/2130; GA AV ČR(CZ) IAA2071302 Institutional research plan: CEZ:AV0Z2071913; CEZ:AV0Z20710524 Keywords : dynamics of passive lateral (earth) pressure * rotation about the top * retaining structure * history of both pressure component Subject RIV: JM - Building Engineering

Numerical modeling of dynamics of heart rate and arterial pressure during passive orthostatic test

Science.gov (United States)

Ishbulatov, Yu. M.; Kiselev, A. R.; Karavaev, A. S.

2018-04-01

A model of human cardiovascular system is proposed to describe the main heart rhythm, influence of autonomous regulation on frequency and strength of heart contractions and resistance of arterial vessels; process of formation of arterial pressure during systolic and diastolic phases; influence of respiration; synchronization between loops of autonomous regulation. The proposed model is used to simulate the dynamics of heart rate and arterial pressure during passive transition from supine to upright position. Results of mathematical modeling are compared to original experimental data.

Elasto-dynamic analysis of a gear pump-Part IV: Improvement in the pressure distribution modelling

Science.gov (United States)

Mucchi, E.; Dalpiaz, G.; Fernàndez del Rincòn, A.

2015-01-01

This work concerns external gear pumps for automotive applications, which operate at high speed and low pressure. In previous works of the authors (Part I and II, [1,2]), a non-linear lumped-parameter kineto-elastodynamic model for the prediction of the dynamic behaviour of external gear pumps was presented. It takes into account the most important phenomena involved in the operation of this kind of machine. The two main sources of noise and vibration are considered: pressure pulsation and gear meshing. The model has been used in order to foresee the influence of working conditions and design modifications on vibration generation. The model experimental validation is a difficult task. Thus, Part III proposes a novel methodology for the validation carried out by the comparison of simulations and experimental results concerning forces and moments: it deals with the external and inertial components acting on the gears, estimated by the model, and the reactions and inertial components on the pump casing and the test plate, obtained by measurements. The validation is carried out by comparing the level of the time synchronous average in the time domain and the waterfall maps in the frequency domain, with particular attention to identify system resonances. The validation results are satisfactory global, but discrepancies are still present. Moreover, the assessed model has been properly modified for the application to a new virtual pump prototype with helical gears in order to foresee gear accelerations and dynamic forces. Part IV is focused on improvements in the modelling and analysis of the phenomena bound to the pressure distribution around the gears in order to achieve results closer to the measured values. As a matter of fact, the simulation results have shown that a variable meshing stiffness has a notable contribution on the dynamic behaviour of the pump but this is not as important as the pressure phenomena. As a consequence, the original model was modified with

Evaluating CO2 and CH4 dynamics of Alaskan ecosystems during the Holocene Thermal Maximum

Science.gov (United States)

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.

Theoretical Analysis of Penalized Maximum-Likelihood Patlak Parametric Image Reconstruction in Dynamic PET for Lesion Detection.

Science.gov (United States)

Yang, Li; Wang, Guobao; Qi, Jinyi

2016-04-01

Detecting cancerous lesions is a major clinical application of emission tomography. In a previous work, we studied penalized maximum-likelihood (PML) image reconstruction for lesion detection in static PET. Here we extend our theoretical analysis of static PET reconstruction to dynamic PET. We study both the conventional indirect reconstruction and direct reconstruction for Patlak parametric image estimation. In indirect reconstruction, Patlak parametric images are generated by first reconstructing a sequence of dynamic PET images, and then performing Patlak analysis on the time activity curves (TACs) pixel-by-pixel. In direct reconstruction, Patlak parametric images are estimated directly from raw sinogram data by incorporating the Patlak model into the image reconstruction procedure. PML reconstruction is used in both the indirect and direct reconstruction methods. We use a channelized Hotelling observer (CHO) to assess lesion detectability in Patlak parametric images. Simplified expressions for evaluating the lesion detectability have been derived and applied to the selection of the regularization parameter value to maximize detection performance. The proposed method is validated using computer-based Monte Carlo simulations. Good agreements between the theoretical predictions and the Monte Carlo results are observed. Both theoretical predictions and Monte Carlo simulation results show the benefit of the indirect and direct methods under optimized regularization parameters in dynamic PET reconstruction for lesion detection, when compared with the conventional static PET reconstruction.

Maximum Water Hammer Sensitivity Analysis

OpenAIRE

Jalil Emadi; Abbas Solemani

2011-01-01

Pressure waves and Water Hammer occur in a pumping system when valves are closed or opened suddenly or in the case of sudden failure of pumps. Determination of maximum water hammer is considered one of the most important technical and economical items of which engineers and designers of pumping stations and conveyance pipelines should take care. Hammer Software is a recent application used to simulate water hammer. The present study focuses on determining significance of ...

Quasi-dynamic pressure and temperature initiated βδ solid phase transitions in HMX

Science.gov (United States)

Zaug, Joseph M.; Farber, Daniel L.; Craig, Ian M.; Blosch, Laura L.; Shuh, David K.; Hansen, Donald W.; Aracne-Ruddle, Chantel M.

2000-04-01

The phase transformation of β-HMX (>0.5% RDX) to δ phase has been studied for over twenty years and more recently with an high-contrast optical second harmonic generation technique. Shock studies of the plastic binder composites of HMX have indicated that the transition is perhaps irreversible, a result that concurs with the static pressure results published by F. Goetz et al. [1] in 1978. However, the stability field favors the β polymorph over δ as pressure is increased (up to 5.4 GPa) along any thermodynamically reasonable isotherm. In this experiment, strict control of pressure and temperature is maintained while x-ray and optical diagnostics are applied to monitor the conformational dynamics of HMX. Unlike the temperature induced β→δ transition, the pressure induced is heterogeneous in nature. The 1 bar 25 °C δ→β transition is not immediate, occuring over tens of hours. Transition points and kinetics are path dependent and consequently this paper describes our work in progress.

Generalization of the Bogoliubov-Zubarev Theorem for Dynamic Pressure to the Case of Compressibility

Science.gov (United States)

Rudoi, Yu. G.

2018-01-01

We present the motivation, formulation, and modified proof of the Bogoliubov-Zubarev theorem connecting the pressure of a dynamical object with its energy within the framework of a classical description and obtain a generalization of this theorem to the case of dynamical compressibility. In both cases, we introduce the volume of the object into consideration using a singular addition to the Hamiltonian function of the physical object, which allows using the concept of the Bogoliubov quasiaverage explicitly already on a dynamical level of description. We also discuss the relation to the same result known as the Hellmann-Feynman theorem in the framework of the quantum description of a physical object.

Influence of the rotor-stator interaction on the dynamic stresses of Francis runners

International Nuclear Information System (INIS)

Guillaume, R; Scolaro, D; Deniau, J L; Colombet, C

2012-01-01

Thanks to advances in computing capabilities and Computational Fluid Dynamics (CFD) techniques, it is now possible to calculate realistic unsteady pressure fields in Francis turbines. This paper will explain methods to calculate the structural loads and the dynamic behaviour in order to optimize the turbine design and maximize its reliability and lifetime. Depending on the operating conditions of a Francis turbine, different hydraulic phenomena may impact the mechanical behaviour of the structure. According to their nature, these highly variable phenomena should be treated differently and specifically in order to estimate the potential risks arising on submerged structures, in particular the runner. The operating condition studied thereafter is the point at maximum power with the maximum head. Under this condition, the runner is excited by only one dynamic phenomenon named the Rotor-Stator Interaction (RSI). The origin of the phenomenon is located on the radial gap of the turbine and is the source of pressure fluctuations. A fluid-structure analysis is performed to observe the influence of that dynamic pressure field on the runner behaviour. The first part of the paper deals with the unsteady fluid computation. The RSI phenomenon is totally unsteady so the fluid simulation must take into account the entire machine and its rotation movement, in order to obtain a dynamic pressure field. In the second part of the paper, a method suitable for the RSI study is developed. It is known that the fluctuating pressure in this gap can be described as a sum of spatial components. By evaluating these components in the CFD results and on the scale model, it is possible to assess the relevance of the numerical results on the whole runner. After this step, the numerical pressure field can be used as the dynamic load of the structure. The final part of the paper presentsthe mechanical finite element calculations. A modal analysis of the runner in water and a harmonic analysis of its

Dynamic Performance of Maximum Power Point Trackers in TEG Systems Under Rapidly Changing Temperature Conditions

Science.gov (United States)

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 production rate optimization for sulphuric acid decomposition process in tubular plug-flow reactor

International Nuclear Information System (INIS)

Wang, Chao; Chen, Lingen; Xia, Shaojun; Sun, Fengrui

2016-01-01

A sulphuric acid decomposition process in a tubular plug-flow reactor with fixed inlet flow rate and completely controllable exterior wall temperature profile and reactants pressure profile is studied in this paper by using finite-time thermodynamics. The maximum production rate of the aimed product SO 2 and the optimal exterior wall temperature profile and reactants pressure profile are obtained by using nonlinear programming method. Then the optimal reactor with the maximum production rate is compared with the reference reactor with linear exterior wall temperature profile and the optimal reactor with minimum entropy generation rate. The result shows that the production rate of SO 2 of optimal reactor with the maximum production rate has an increase of more than 7%. The optimization of temperature profile has little influence on the production rate while the optimization of reactants pressure profile can significantly increase the production rate. The results obtained may provide some guidelines for the design of real tubular reactors. - Highlights: • Sulphuric acid decomposition process in tubular plug-flow reactor is studied. • Fixed inlet flow rate and controllable temperature and pressure profiles are set. • Maximum production rate of aimed product SO 2 is obtained. • Corresponding optimal temperature and pressure profiles are derived. • Production rate of SO 2 of optimal reactor increases by 7%.

The dynamic pressure response to rapid dilatation of the resting urethra in healthy women

DEFF Research Database (Denmark)

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......The urethral pressure response to a sudden forced dilatation was studied at the bladder neck, in the high-pressure zone and in the distal urethra in ten healthy female volunteers. The pressure response was fitted with a double exponential function of the form Pt = Pequ + P alpha e-t/tau alpha + P...... a detailed assessment of static and dynamic urethral responses to dilatation which can be applied as an experimental simulation of urine ingression, and is therefore presumed to be of value in the evaluation of normal and pathological urethral sphincter function....

A data base and analysis program for shuttle main engine dynamic pressure measurements. Appendix B: Data base plots for SSME tests 901-290 through 901-414

Science.gov (United States)

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.

A data base and analysis program for shuttle main engine dynamic pressure measurements. Appendix C: Data base plots for SSME tests 902-214 through 902-314

Science.gov (United States)

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.

The dynamics crossover region in phenol- and cresol-phthalein-dimethylethers under different conditions of pressure and temperature

Energy Technology Data Exchange (ETDEWEB)

Casalini, Riccardo [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States); Paluch, Marian [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States); Roland, C Michael [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States)

2003-03-26

Dielectric relaxation times over a broad range of temperature and pressure for the glass former phenolphthalein-dimethylether (PDE) reveal a change of dynamics at a characteristic relaxation time {tau}{sub B}. The value of {tau}{sub B} was found to be largely insensitive to the particular combination of pressure and temperature of the measurement. Data for a second glass former, cresol-phthalein-dimethylether, having a molecular structure very close to that of PDE, were also analysed. In this case, {tau}{sub B} is much smaller, so the change of dynamics could not be observed in the elevated pressure experiments. The PDE data were in good agreement with the Adam-Gibbs model near T{sub g} ({tau} > {tau}{sub B}), while deviating for {tau} < {tau}{sub B}. Finally, a possible connection between the observed T{sub B} and theoretical models is presented.

Air clearing pressure oscillation produced in a quenching tank by a prototype unit cell sparger of the APR1400

International Nuclear Information System (INIS)

Cho, Seok; Song, Chul-Hwa; Park, Choon-Kyong; Kim, Hwan-Yeol; Baek, Won-Pil

2008-01-01

KAERI has performed a series of experiments to investigate the performance of a prototype sparger for the APR1400 in view of a dynamic load oscillation with a variation of the test conditions such as a discharged air mass, a submergence of the sparger, the valve opening time, and the pool temperature during an air clearing phase. The air mass and pool temperature are in the range of 0.8-1.5 kg and 20-90 o C, respectively. The valve opening time can be adjusted within the range of 0.6-1.8 s. The maximum positive pressure amplitude, which is observed at the bottom of the quenching tank, is increased with the maximum header pressure of the sparger. The valve opening time has a considerable effect on the maximum amplitude. As the opening time decreases, the maximum amplitude at the tank wall is increased. Air mass and pool temperature, however, have a weak effect on the maximum amplitude. Oscillation frequency is decreased with an increase of the air mass in the range of 2.5-4.5 Hz

Water-Pressure Distribution on Seaplane Float

Science.gov (United States)

Thompson, F L

1929-01-01

The investigation presented in this report was conducted for the purpose of determining the distribution and magnitude of water pressures likely to be experienced on seaplane hulls in service. It consisted of the development and construction of apparatus for recording water pressures lasting one one-hundredth second or longer and of flight tests to determine the water pressures on a UO-1 seaplane float under various conditions of taxiing, taking off, and landing. The apparatus developed was found to operate with satisfactory accuracy and is suitable for flight tests on other seaplanes. The tests on the UO-1 showed that maximum pressures of about 6.5 pounds per square inch occur at the step for the full width of the float bottom. Proceeding forward from the step the maximum pressures decrease in magnitude uniformly toward the bow, and the region of highest pressures narrows toward the keel. Immediately abaft the step the maximum pressures are very small, but increase in magnitude toward the stern and there once reached a value of about 5 pounds per square inch. (author)

Accurate and efficient integration for molecular dynamics simulations at constant temperature and pressure

Science.gov (United States)

Lippert, Ross A.; Predescu, Cristian; Ierardi, Douglas J.; Mackenzie, Kenneth M.; Eastwood, Michael P.; Dror, Ron O.; Shaw, David E.

2013-10-01

In molecular dynamics simulations, control over temperature and pressure is typically achieved by augmenting the original system with additional dynamical variables to create a thermostat and a barostat, respectively. These variables generally evolve on timescales much longer than those of particle motion, but typical integrator implementations update the additional variables along with the particle positions and momenta at each time step. We present a framework that replaces the traditional integration procedure with separate barostat, thermostat, and Newtonian particle motion updates, allowing thermostat and barostat updates to be applied infrequently. Such infrequent updates provide a particularly substantial performance advantage for simulations parallelized across many computer processors, because thermostat and barostat updates typically require communication among all processors. Infrequent updates can also improve accuracy by alleviating certain sources of error associated with limited-precision arithmetic. In addition, separating the barostat, thermostat, and particle motion update steps reduces certain truncation errors, bringing the time-average pressure closer to its target value. Finally, this framework, which we have implemented on both general-purpose and special-purpose hardware, reduces software complexity and improves software modularity.

Gas and heat dynamics of a micro-scaled atmospheric pressure plasma reference jet

International Nuclear Information System (INIS)

Kelly, Seán; Golda, Judith; Schulz-von der Gathen, Volker; Turner, Miles M

2015-01-01

Gas and heat dynamics of the ‘Cooperation on Science and Technology (COST) Reference Microplasma Jet’ (COST-jet), a European lead reference device for low temperature atmospheric pressure plasma application, are investigated. Of particular interest to many biomedical application scenarios, the temperature characteristics of a surface impacted by the jet are revealed. Schlieren imaging, thermocouple measurements, infrared thermal imaging and numerical modelling are employed. Temperature spatial profiles in the gas domain reveal heating primarily of the helium fraction of the gas mixture. Thermocouple and model temporal data show a bounded exponential temperature growth described by a single characteristic time parameter to reach  ∼63% or (1-1/e) fraction of the temperature increase. Peak temperatures occurred in the gas domain where the carrier jet exits the COST-jet, with values ranging from ambient temperatures to in excess of 100 °C in ‘α-mode’ operation. In a horizontal orientation of the COST-jet a curved trajectory of the helium effluent at low gas flows results from buoyant forces. Gas mixture profiles reveal significant containment of the helium concentrations for a surface placed in close proximity to the COST-jet. Surface heating of a quartz plate follows a similar bounded exponential temporal temperature growth as device heating. Spatial profiles of surface heating are found to correlate strongly to the impacting effluent where peak temperatures occur in regions of maximum surface helium concentration. (paper)

Gas and heat dynamics of a micro-scaled atmospheric pressure plasma reference jet

Science.gov (United States)

Kelly, Seán; Golda, Judith; Turner, Miles M.; Schulz-von der Gathen, Volker

2015-11-01

Gas and heat dynamics of the ‘Cooperation on Science and Technology (COST) Reference Microplasma Jet’ (COST-jet), a European lead reference device for low temperature atmospheric pressure plasma application, are investigated. Of particular interest to many biomedical application scenarios, the temperature characteristics of a surface impacted by the jet are revealed. Schlieren imaging, thermocouple measurements, infrared thermal imaging and numerical modelling are employed. Temperature spatial profiles in the gas domain reveal heating primarily of the helium fraction of the gas mixture. Thermocouple and model temporal data show a bounded exponential temperature growth described by a single characteristic time parameter to reach  ∼63% or (1-1/e) fraction of the temperature increase. Peak temperatures occurred in the gas domain where the carrier jet exits the COST-jet, with values ranging from ambient temperatures to in excess of 100 °C in ‘α-mode’ operation. In a horizontal orientation of the COST-jet a curved trajectory of the helium effluent at low gas flows results from buoyant forces. Gas mixture profiles reveal significant containment of the helium concentrations for a surface placed in close proximity to the COST-jet. Surface heating of a quartz plate follows a similar bounded exponential temporal temperature growth as device heating. Spatial profiles of surface heating are found to correlate strongly to the impacting effluent where peak temperatures occur in regions of maximum surface helium concentration.

Probabilistic maximum-value wind prediction for offshore environments

DEFF Research Database (Denmark)

Staid, Andrea; Pinson, Pierre; Guikema, Seth D.

2015-01-01

statistical models to predict the full distribution of the maximum-value wind speeds in a 3 h interval. We take a detailed look at the performance of linear models, generalized additive models and multivariate adaptive regression splines models using meteorological covariates such as gust speed, wind speed......, convective available potential energy, Charnock, mean sea-level pressure and temperature, as given by the European Center for Medium-Range Weather Forecasts forecasts. The models are trained to predict the mean value of maximum wind speed, and the residuals from training the models are used to develop...... the full probabilistic distribution of maximum wind speed. Knowledge of the maximum wind speed for an offshore location within a given period can inform decision-making regarding turbine operations, planned maintenance operations and power grid scheduling in order to improve safety and reliability...

Experimental evidence of high pressure decoupling between charge transport and structural dynamics in a protic ionic glass-former.

Science.gov (United States)

Wojnarowska, Z; Rams-Baron, M; Knapik-Kowalczuk, J; Połatyńska, A; Pochylski, M; Gapinski, J; Patkowski, A; Wlodarczyk, P; Paluch, M

2017-08-01

In this paper the relaxation dynamics of ionic glass-former acebutolol hydrochloride (ACB-HCl) is studied as a function of temperature and pressure by using dynamic light scattering and broadband dielectric spectroscopy. These unique experimental data provide the first direct evidence that the decoupling between the charge transport and structural relaxation exists in proton conductors over a wide T-P thermodynamic space, with the time scale of structural relaxation being constant at the liquid-glass transition (τ α  = 1000 s). We demonstrate that the enhanced proton transport, being a combination of intermolecular H + hopping between cation and anion as well as tautomerization process within amide moiety of ACB molecule, results in a breakdown of the Stokes-Einstein relation at ambient and elevated pressure with the fractional exponent k being pressure dependent. The dT g /dP coefficient, stretching exponent β KWW and dynamic modulus E a /ΔV # were found to be the same regardless of the relaxation processes studied. This is in contrast to the apparent activation volume parameter that is different when charge transport and structural dynamics are considered. These experimental results together with theoretical considerations create new ideas to design efficient proton conductors for potential electrochemical applications.

Achieving maximum sustainable yield in mixed fisheries

NARCIS (Netherlands)

Ulrich, Clara; Vermard, Youen; Dolder, Paul J.; Brunel, Thomas; Jardim, Ernesto; Holmes, Steven J.; Kempf, Alexander; Mortensen, Lars O.; Poos, Jan Jaap; Rindorf, Anna

2017-01-01

Achieving single species maximum sustainable yield (MSY) in complex and dynamic fisheries targeting multiple species (mixed fisheries) is challenging because achieving the objective for one species may mean missing the objective for another. The North Sea mixed fisheries are a representative example

A technique for measuring dynamic friction coefficient under impact loading.

Science.gov (United States)

Lin, Y L; Qin, J G; Chen, R; Zhao, P D; Lu, F Y

2014-09-01

We develop a novel setup based on the split Hopkinson pressure bar technique to test the dynamic friction coefficient under impact loading. In the setup, the major improvement is that the end of the incident bar near the specimen is wedge-shaped, which results in a combined compressive and shear loading applied to the specimen. In fact, the shear loading is caused by the interfacial friction between specimen and bars. Therefore, when the two loading force histories are measured, the friction coefficient histories can be calculated without any assumptions and theoretical derivations. The geometry of the friction pairs is simple, and can be either cuboid or cylindrical. Regarding the measurements, two quartz transducers are used to directly record the force histories, and an optical apparatus is designed to test the interfacial slip movement. By using the setup, the dynamic friction coefficient of PTFE/aluminum 7075 friction pairs was tested. The time resolved dynamic friction coefficient and slip movement histories were achieved. The results show that the friction coefficient changes during the loading process, the average data of the relatively stable flat plateau section of the friction coefficient curves is 0.137, the maximum normal pressure is 52 MPa, the maximum relative slip velocity is 1.5 m/s, and the acceleration is 8400 m(2)/s. Furthermore, the friction test was simulated using an explicit FEM code LS-DYNA. The simulation results showed that the constant pressure and slip velocity can both be obtained with a wide flat plateau incident pulse. For some special friction pairs, normal pressure up to a few hundred MPa, interfacial slip velocities up to 10 m/s, and slip movement up to centimeter-level can be expected.

Verification of experimental dynamic strength methods with atomistic ramp-release simulations

Science.gov (United States)

Moore, Alexander P.; Brown, Justin L.; Lim, Hojun; Lane, J. Matthew D.

2018-05-01

Material strength and moduli can be determined from dynamic high-pressure ramp-release experiments using an indirect method of Lagrangian wave profile analysis of surface velocities. This method, termed self-consistent Lagrangian analysis (SCLA), has been difficult to calibrate and corroborate with other experimental methods. Using nonequilibrium molecular dynamics, we validate the SCLA technique by demonstrating that it accurately predicts the same bulk modulus, shear modulus, and strength as those calculated from the full stress tensor data, especially where strain rate induced relaxation effects and wave attenuation are small. We show here that introducing a hold in the loading profile at peak pressure gives improved accuracy in the shear moduli and relaxation-adjusted strength by reducing the effect of wave attenuation. When rate-dependent effects coupled with wave attenuation are large, we find that Lagrangian analysis overpredicts the maximum unload wavespeed, leading to increased error in the measured dynamic shear modulus. These simulations provide insight into the definition of dynamic strength, as well as a plausible explanation for experimental disagreement in reported dynamic strength values.

Estimation of maximum pressure in small containments of PWR reactors due to loss of coolant accident in primary circuit; Estimativa da pressao maxima em contencoes de reatores PWR de pequeno porte devido a um acidente de perda de refrigerante no circuito primario

Energy Technology Data Exchange (ETDEWEB)

Mendes Neto, Teofilo [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil); Moreira, Joao Manoel Losada [Centro Tecnologico da Marinha em Sao Paulo (CTMSP), SP (Brazil)

2000-07-01

This work studies the problem of containment pressurization after a LOCA in reactors with small containment free volumes. The relationship between the reactor power and the containment free volume is described with the ratio between the volumes of the primary circuit and of the containment. The maximum pressure in a containment, following a LOCA, obtained after a correlation based on large containment PWR, is around 185 psia for a primary circuit and containment volumes ratio of 0.025. For the same problem, calculations with the CONTEMPT-LT code produced a maximum pressure of 162 psia. The behavior of the temperature after a LOCA to the containment, as a function of the ratio between the primary circuit and containment volume, is such that it increases reaching asymptotically to a maximum; differently, the pressure increases almost linearly with the ratio of volumes. (author)

Dynamics of coarse particulate matter in the turbidity maximum zone of the Gironde Estuary

Science.gov (United States)

Fuentes-Cid, Ana; Etcheber, Henri; Schmidt, Sabine; Abril, Gwenaël; De-Oliveira, Eric; Lepage, Mario; Sottolichio, Aldo

2014-01-01

There is a lack of studies devoted to coarse particulate matter (CPM) in estuaries, although this fraction can disturb activities that filter large volumes of water, such as industrial or fishery activities. In the macrotidal and highly-turbid Gironde Estuary, a monthly sampling of CPM was performed in 2011 and 2013 at two stations in the Turbidity Maximum Zone (TMZ) to understand its seasonal, tidal and hydrological dynamics. Regardless of the season and station, low quantities of CPM (few g m-3) were observed in comparison with suspended particulate matter (several 103 g m-3). The highest concentrations were consistently recorded in bottom waters and at the upstream station. Whereas there is no clear link between the CPM present in the column water and spring or neap tides, an increase in the CPM size has been identified at the two stations after a flood event, fact potentially critical regarding filtering functioning of estuarine activities.

In situ pore-pressure evolution during dynamic CPT measurements in soft sediments of the western Baltic Sea

Science.gov (United States)

Seifert, Annedore; Stegmann, Sylvia; Mörz, Tobias; Lange, Matthias; Wever, Thomas; Kopf, Achim

2008-08-01

We present in situ strength and pore-pressure measurements from 57 dynamic cone penetration tests in sediments of Mecklenburg ( n = 51), Eckernförde ( n = 2) and Gelting ( n = 4) bays, western Baltic Sea, characterised by thick mud layers and partially free microbial gas resulting from the degradation of organic material. In Mecklenburg and Eckernförde bays, sediment sampling by nine gravity cores served sedimentological characterisation, analyses of geotechnical properties, and laboratory shear tests. At selected localities, high-resolution echo-sounder profiles were acquired. Our aim was to deploy a dynamic cone penetrometer (CPT) to infer sediment shear strength and cohesion of the sea bottom as a function of fluid saturation. The results show very variable changes in pore pressure and sediment strength during the CPT deployments. The majority of the CPT measurements ( n = 54) show initially negative pore-pressure values during penetration, and a delayed response towards positive pressures thereafter. This so-called type B pore-pressure signal was recorded in all three bays, and is typically found in soft muds with high water contents and undrained shear strengths of 1.6-6.4 kPa. The type B signal is further affected by displacement of sediment and fluid upon penetration of the lance, skin effects during dynamic profiling, enhanced consolidation and strength of individual horizons, the presence of free gas, and a dilatory response of the sediment. In Mecklenburg Bay, the remaining small number of CPT measurements ( n = 3) show a well-defined peak in both pore pressure and cone resistance during penetration, i.e. an initial marked increase which is followed by exponential pore-pressure decay during dissipation. This so-called type A pore-pressure signal is associated with normally consolidated mud, with indurated clay layers showing significantly higher undrained shear strength (up to 19 kPa). In Eckernförde and Gelting bays pore-pressure response type B is

A data base and analysis program for shuttle main engine dynamic pressure measurements. Appendix F: Data base plots for SSME tests 750-120 through 750-200

Science.gov (United States)

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.

High pressure experimental water loop

International Nuclear Information System (INIS)

Grenon, M.

1958-01-01

A high pressure experimental water loop has been made for studying the detection and evolution of cladding failure in a pressurized reactor. The loop has been designed for a maximum temperature of 360 deg. C, a maximum of 160 kg/cm 2 and flow rates up to 5 m 3 /h. The entire loop consists of several parts: a main circuit with a canned rotor circulation pump, steam pressurizer, heating tubes, two hydro-cyclones (one de-gasser and one decanter) and one tubular heat exchanger; a continuous purification loop, connected in parallel, comprising pressure reducing valves and resin pots which also allow studies of the stability of resins under pressure, temperature and radiation; following the gas separator is a gas loop for studying the recombination of the radiolytic gases in the steam phase. The preceding circuits, as well as others, return to a low pressure storage circuit. The cold water of the low pressure storage flask is continuously reintroduced into the high pressure main circuit by means of a return pump at a maximum head of 160 kg /cm 2 , and adjusted to the pressurizer level. This loop is also a testing bench for the tight high pressure apparatus. The circulating pump and the connecting flanges (Oak Ridge type) are water-tight. The feed pump and the pressure reducing valves are not; the un-tight ones have a system of leak recovery. To permanently check the tightness the circuit has been fitted with a leak detection system (similar to the HRT one). (author) [fr

A Maximum Radius for Habitable Planets.

Science.gov (United States)

Alibert, Yann

2015-09-01

We compute the maximum radius a planet can have in order to fulfill two constraints that are likely necessary conditions for habitability: 1- surface temperature and pressure compatible with the existence of liquid water, and 2- no ice layer at the bottom of a putative global ocean, that would prevent the operation of the geologic carbon cycle to operate. We demonstrate that, above a given radius, these two constraints cannot be met: in the Super-Earth mass range (1-12 Mearth), the overall maximum that a planet can have varies between 1.8 and 2.3 Rearth. This radius is reduced when considering planets with higher Fe/Si ratios, and taking into account irradiation effects on the structure of the gas envelope.

Computational Fluid Dynamics Simulation of Combustion Instability in Solid Rocket Motor : Implementation of Pressure Coupled Response Function

OpenAIRE

S. Saha; D. Chakraborty

2016-01-01

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 ...

Comparison of ionospheric convection and the transpolar potential before and after solar wind dynamic pressure fronts: implications for magnetospheric reconnection

Science.gov (United States)

Boudouridis, A.; Zesta, E.; Lyons, L. R.; Kim, H.-J.; Lummerzheim, D.; Wiltberger, M.; Weygand, J. M.; Ruohoniemi, J. M.; Ridley, A. J.

2012-04-01

The solar wind dynamic pressure, both through its steady state value and through its variations, plays an important role in the determination of the state of the terrestrial magnetosphere and ionosphere, its effects being only secondary to those of the Interplanetary Magnetic Field (IMF). Recent studies have demonstrated the significant effect solar wind dynamic pressure enhancements have on ionospheric convection and the transpolar potential. Further studies have shown a strong response of the polar cap boundary and thus the open flux content of the magnetosphere. These studies clearly illustrate the strong coupling of solar wind dynamic pressure fronts to the terrestrial magnetosphere-ionosphere system. We present statistical studies of the response of Super Dual Auroral Radar Network (SuperDARN) flows, and Assimilative Mapping of Ionospheric Electrodynamics (AMIE) transpolar potentials to sudden enhancements in solar wind dynamic pressure. The SuperDARN results show that the convection is enhanced within both the dayside and nightside ionosphere. The dayside response is more clear and immediate, while the response on the nightside is slower and more evident for low IMF By values. AMIE results show that the overall convection, represented by the transpolar potential, has a strong response immediately after an increase in pressure, with magnitude and duration modulated by the background IMF Bz conditions. We compare the location of the SuperDARN convection enhancements with the location and motion of the polar cap boundary, as determined by POLAR Ultra-Violet Imager (UVI) images and runs of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic model for specific events. We find that the boundary exhibits a poleward motion after the increase in dynamic pressure. The enhanced ionospheric flows and the poleward motion of the boundary on the nightside are both signatures of enhanced tail reconnection, a conclusion that is reinforced by the observation of the

Pressure dependence of elastic and dynamical properties of zinc-blende ZnS and ZnSe from first principle calculation

Directory of Open Access Journals (Sweden)

H.Y. Wang

2012-03-01

Full Text Available The density-functional theory (DFT and density-functional perturbation theory (DFPT are employed to study the pressure dependence of elastic and dynamical properties of zinc-blende ZnS and ZnSe. The calculated elastic constants and phonon spectra from 0 GPa to 15 GPa are compared with the available experimental data. Generally, our calculated values are overestimated with experimental data, but agree well with recent other theoretical values. The discrepancies with experimental data are due to the use of local density approximation (LDA and effect of temperature. In this work, in order to compare with experimental data, we calculated and discussed the pressure derivatives of elastic constants, the pressure dependence of dynamical effect charge, and mode Grüneisen parameter at Γ.

Characteristics of Plantar Loads in Maximum Forward Lunge Tasks in Badminton.

Science.gov (United States)

Hu, Xiaoyue; Li, Jing Xian; Hong, Youlian; Wang, Lin

2015-01-01

Badminton players often perform powerful and long-distance lunges during such competitive matches. The objective of this study is to compare the plantar loads of three one-step maximum forward lunges in badminton. Fifteen right-handed male badminton players participated in the study. Each participant performed five successful maximum lunges at three directions. For each direction, the participant wore three different shoe brands. Plantar loading, including peak pressure, maximum force, and contact area, was measured by using an insole pressure measurement system. Two-way ANOVA with repeated measures was employed to determine the effects of the different lunge directions and different shoes, as well as the interaction of these two variables, on the measurements. The maximum force (MF) on the lateral midfoot was lower when performing left-forward lunges than when performing front-forward lunges (p = 0.006, 95% CI = -2.88 to -0.04%BW). The MF and peak pressures (PP) on the great toe region were lower for the front-forward lunge than for the right-forward lunge (MF, p = 0.047, 95% CI = -3.62 to -0.02%BW; PP, p = 0.048, 95% CI = -37.63 to -0.16 KPa) and left-forward lunge (MF, p = 0.015, 95% CI = -4.39 to -0.38%BW; PP, p = 0.008, 95% CI = -47.76 to -5.91 KPa). These findings indicate that compared with the front-forward lunge, left and right maximum forward lunges induce greater plantar loads on the great toe region of the dominant leg of badminton players. The differences in the plantar loads of the different lunge directions may be potential risks for injuries to the lower extremities of badminton players.

On the Pontryagin maximum principle for systems with delays. Economic applications

Science.gov (United States)

Kim, A. V.; Kormyshev, V. M.; Kwon, O. B.; Mukhametshin, E. R.

2017-11-01

The Pontryagin maximum principle [6] is the key stone of finite-dimensional optimal control theory [1, 2, 5]. So beginning with opening the maximum principle it was important to extend the maximum principle on various classes of dynamical systems. In t he paper we consider some aspects of application of i-smooth analysis [3, 4] in the theory of the Pontryagin maximum principle [6] for systems with delays, obtained results can be applied by elaborating optimal program controls in economic models with delays.

Thermal hydraulic behavior of SCWR sliding pressure startup

International Nuclear Information System (INIS)

Fu Shengwei; Zhou Chong; Xu Zhihong; Yang Yanhua

2011-01-01

The modification to ATHLET-SC code is introduced in this paper, which realizes the simulation of trans-critical transients using two-phase model. With the modified code, the thermal-hydraulic dynamic behavior of the mixed SCWR core during the startup process is simulated. The startup process is similar to the design of SCLWR-H sliding pressure startup. The results show that maximum temperature of cladding-surface does not exceed 650℃ in the whole startup process, and the sudden change of water properties in the trans-critical transients will not cause harmful influence to the heat transfer of the fuel cladding. (authors)

A model to simulate the dynamic of a PWR pressurizer using the CSMP program

International Nuclear Information System (INIS)

Woiski, E.R.

1981-01-01

A mathematical model has been developed to simulate the dynamic behavior of a PWR pressurizer using the CSMP program. A two-control-volume formulation non-equilibrium model has been used for this purpose. Thermodynamic states are obtained after each integration cycle. The code was tested against experimental results of Shippingport and NPD (Nuclear Power Demonstration Plant) pressurizers. It was also tested against available data from Angra I and Angra II/III safety analysis report. Despite the model simplicity, the lack of important data and the low reliability or the experimental curves, the calculated and experimental results compared well. (Author) [pt

Miniaturized Dynamic Pressure Sensor Arrays with Sub-Millimeter (mm) Spacing for Cross-Flow Transition Measurements, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The Interdisciplinary Consulting Corporation (IC2) and in partnership with the University of Florida (UF) propose a microfabricated, dynamic piezoelectric pressure...

Miniaturized Dynamic Pressure Sensor Arrays with Sub-Millimeter (mm) Spacing for Cross-Flow Transition Measurements, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — The Interdisciplinary Consulting Corporation (IC2) and in partnership with the University of Florida (UF) propose a microfabricated, dynamic piezoelectric pressure...

Prediction of B1 to B10 phase transition in LuN under pressure: An ab-initio investigation

Energy Technology Data Exchange (ETDEWEB)

Sahoo, B. D., E-mail: bdsahoo@barc.gov.in; Mukherjee, D.; Joshi, K. D.; Kaushik, T. C.; Gupta, Satish C. [Applied Physics Division, Bhabha Atomic Research Centre, Mumbai, India 400085 (India)

2016-05-23

Ab-initio total energy calculations have been performed in lutetium nitride (LuN) as a function of hydrostatic compression to understand the high pressure behavior of this compound. Our calculations predict a phase transition from ambient rocksalt type structure (B1 phase) to a tetragonal structure (B10 phase) at ~ 240 GPa. The phase transition has been identified as first order in nature with volume discontinuity of ~ 6%. The predicted high pressure phase has been found to be stable up to at least 400 GPa, the maximum pressure up to which calculations have been performed.Further, to substantiate the results of static lattice calculations analysis of lattice dynamic stability of B1 and B10 phase has been carried out at different pressures. Apart from this, we have analyzed the lattice dynamic stability CsCl type (B2) phase around the 240 GPa, the pressure reported for B1 to B2 transition in previous all-electron calculations by Gupta et al. 2013. We find that the B2 structure is lattice dynamically unstable at this pressure and remains unstable up to ~ 400 GPa, ruling out the possibility of B1 to B2 phase transition at least up to ~ 400 GPa. Further, the theoretically determined equation of state has been utilized to derive various physical quantities such as zero pressure equilibrium volume, bulk modulus, and pressure derivative of bulk modulus of B1 phase at ambient conditions.

Molecular dynamics simulations of the melting curve of NiAl alloy under pressure

International Nuclear Information System (INIS)

Zhang, Wenjin; Peng, Yufeng; Liu, Zhongli

2014-01-01

The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fitting the well-known Simon equation to our melting data, we yielded the melting curves for NiAl: 1783(1 + P/9.801) 0.298 (one-phase approach), 1850(1 + P/12.806) 0.357 (two-phase approach). The good agreement of the resulting equation of states and the zero-pressure melting point (calc., 1850 ± 25 K, exp., 1911 K) with experiment proved the correctness of these results. These melting data complemented the absence of experimental high-pressure melting of NiAl. To check the transferability of this EAM potential, we have also predicted the melting curves of pure nickel and pure aluminum. Results show the calculated melting point of Nickel agrees well with experiment at zero pressure, while the melting point of aluminum is slightly higher than experiment

Maximum allowable load on wheeled mobile manipulators

International Nuclear Information System (INIS)

Habibnejad Korayem, M.; Ghariblu, H.

2003-01-01

This paper develops a computational technique for finding the maximum allowable load of mobile manipulator during a given trajectory. The maximum allowable loads which can be achieved by a mobile manipulator during a given trajectory are limited by the number of factors; probably the dynamic properties of mobile base and mounted manipulator, their actuator limitations and additional constraints applied to resolving the redundancy are the most important factors. To resolve extra D.O.F introduced by the base mobility, additional constraint functions are proposed directly in the task space of mobile manipulator. Finally, in two numerical examples involving a two-link planar manipulator mounted on a differentially driven mobile base, application of the method to determining maximum allowable load is verified. The simulation results demonstrates the maximum allowable load on a desired trajectory has not a unique value and directly depends on the additional constraint functions which applies to resolve the motion redundancy

Quantitative Imaging of Turbulent Mixing Dynamics in High-Pressure Fuel Injection to Enable Predictive Simulations of Engine Combustion

Energy Technology Data Exchange (ETDEWEB)

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.

Lattice Dynamics Study of Phonon Instability and Thermal Properties of Type-I Clathrate K₈Si46 under High Pressure.

Science.gov (United States)

Zhang, Wei; Zeng, Zhao Yi; Ge, Ni Na; Li, Zhi Guo

2016-07-25

For a further understanding of the phase transitions mechanism in type-I silicon clathrates K₈Si 46 , ab initio self-consistent electronic calculations combined with linear-response method have been performed to investigate the vibrational properties of alkali metal K atoms encapsulated type-I silicon-clathrate under pressure within the framework of density functional perturbation theory. Our lattice dynamics simulation results showed that the pressure induced phase transition of K₈Si 46 was believed to be driven by the phonon instability of the calthrate lattice. Analysis of the evolution of the partial phonon density of state with pressure, a legible dynamic picture for both guest K atoms and host lattice, was given. In addition, based on phonon calculations and combined with quasi-harmonic approximation, the specific heat of K₈Si 46 was derived, which agreed very well with experimental results. Also, other important thermal properties including the thermal expansion coefficients and Grüneisen parameters of K₈Si 46 under different temperature and pressure were also predicted.

Molecular dynamics simulations of disjoining pressure effects in ultra-thin water films on a metal surface

Science.gov (United States)

Hu, Han; Sun, Ying

2013-11-01

Disjoining pressure, the excess pressure in an ultra-thin liquid film as a result of van der Waals interactions, is important in lubrication, wetting, flow boiling, and thin film evaporation. The classic theory of disjoining pressure is developed for simple monoatomic liquids. However, real world applications often utilize water, a polar liquid, for which fundamental understanding of disjoining pressure is lacking. In the present study, molecular dynamics (MD) simulations are used to gain insights into the effect of disjoining pressure in a water thin film. Our MD models were firstly validated against Derjaguin's experiments on gold-gold interactions across a water film and then verified against disjoining pressure in an argon thin film using the Lennard-Jones potential. Next, a water thin film adsorbed on a gold surface was simulated to examine the change of vapor pressure with film thickness. The results agree well with the classic theory of disjoining pressure, which implies that the polar nature of water molecules does not play an important role. Finally, the effects of disjoining pressure on thin film evaporation in nanoporous membrane and on bubble nucleation are discussed.

Performance analysis and comparison of an Atkinson cycle coupled to variable temperature heat reservoirs under maximum power and maximum power density conditions

International Nuclear Information System (INIS)

Wang, P.-Y.; Hou, S.-S.

2005-01-01

In this paper, performance analysis and comparison based on the maximum power and maximum power density conditions have been conducted for an Atkinson cycle coupled to variable temperature heat reservoirs. The Atkinson cycle is internally reversible but externally irreversible, since there is external irreversibility of heat transfer during the processes of constant volume heat addition and constant pressure heat rejection. This study is based purely on classical thermodynamic analysis methodology. It should be especially emphasized that all the results and conclusions are based on classical thermodynamics. The power density, defined as the ratio of power output to maximum specific volume in the cycle, is taken as the optimization objective because it considers the effects of engine size as related to investment cost. The results show that an engine design based on maximum power density with constant effectiveness of the hot and cold side heat exchangers or constant inlet temperature ratio of the heat reservoirs will have smaller size but higher efficiency, compression ratio, expansion ratio and maximum temperature than one based on maximum power. From the view points of engine size and thermal efficiency, an engine design based on maximum power density is better than one based on maximum power conditions. However, due to the higher compression ratio and maximum temperature in the cycle, an engine design based on maximum power density conditions requires tougher materials for engine construction than one based on maximum power conditions

Final Report DE-FG02-00ER54583: 'Physics of Atmospheric Pressure Glow Discharges' and 'Nanoparticle Nucleation and Dynamics in Low-Pressure Plasmas'

International Nuclear Information System (INIS)

Kortshagen, Uwe; Heberlein, Joachim; Girshick, Steven L.

2009-01-01

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.

Measurement of Vehicle-Bridge-Interaction force using dynamic tire pressure monitoring

Science.gov (United States)

Chen, Zhao; Xie, Zhipeng; Zhang, Jian

2018-05-01

The Vehicle-Bridge-Interaction (VBI) force, i.e., the normal contact force of a tire, is a key component in the VBI mechanism. The VBI force measurement can facilitate experimental studies of the VBI as well as input-output bridge structural identification. This paper introduces an innovative method for calculating the interaction force by using dynamic tire pressure monitoring. The core idea of the proposed method combines the ideal gas law and a basic force model to build a relationship between the tire pressure and the VBI force. Then, unknown model parameters are identified by the Extended Kalman Filter using calibration data. A signal filter based on the wavelet analysis is applied to preprocess the effect that the tire rotation has on the pressure data. Two laboratory tests were conducted to check the proposed method's validity. The effects of different road irregularities, loads and forward velocities were studied. Under the current experiment setting, the proposed method was robust to different road irregularities, and the increase in load and velocity benefited the performance of the proposed method. A high-speed test further supported the use of this method in rapid bridge tests. Limitations of the derived theories and experiment were also discussed.

Dynamic Pressure Microphones

Science.gov (United States)

Werner, E.

In 1876, Alexander Graham Bell described his first telephone with a microphone using magnetic induction to convert the voice input into an electric output signal. The basic principle led to a variety of designs optimized for different needs, from hearing impaired users to singers or broadcast announcers. From the various sound pressure versions, only the moving coil design is still in mass production for speech and music application.

Characteristics of Plantar Loads in Maximum Forward Lunge Tasks in Badminton.

Directory of Open Access Journals (Sweden)

Xiaoyue Hu

Full Text Available Badminton players often perform powerful and long-distance lunges during such competitive matches. The objective of this study is to compare the plantar loads of three one-step maximum forward lunges in badminton.Fifteen right-handed male badminton players participated in the study. Each participant performed five successful maximum lunges at three directions. For each direction, the participant wore three different shoe brands. Plantar loading, including peak pressure, maximum force, and contact area, was measured by using an insole pressure measurement system. Two-way ANOVA with repeated measures was employed to determine the effects of the different lunge directions and different shoes, as well as the interaction of these two variables, on the measurements.The maximum force (MF on the lateral midfoot was lower when performing left-forward lunges than when performing front-forward lunges (p = 0.006, 95% CI = -2.88 to -0.04%BW. The MF and peak pressures (PP on the great toe region were lower for the front-forward lunge than for the right-forward lunge (MF, p = 0.047, 95% CI = -3.62 to -0.02%BW; PP, p = 0.048, 95% CI = -37.63 to -0.16 KPa and left-forward lunge (MF, p = 0.015, 95% CI = -4.39 to -0.38%BW; PP, p = 0.008, 95% CI = -47.76 to -5.91 KPa.These findings indicate that compared with the front-forward lunge, left and right maximum forward lunges induce greater plantar loads on the great toe region of the dominant leg of badminton players. The differences in the plantar loads of the different lunge directions may be potential risks for injuries to the lower extremities of badminton players.

Fluid Pressures at the Shoe-Floor-Contaminant Interface During Slips: Effects of Tread & Implications on Slip Severity

Science.gov (United States)

Beschorner, Kurt E.; Albert, Devon L.; Chambers, April J.; Redfern, Mark S.

2018-01-01

Previous research on slip and fall accidents has suggested that pressurized fluid between the shoe and floor is responsible for initiating slips yet this effect has not been verified experimentally. This study aimed to 1) measure hydrodynamic pressures during slipping for treaded and untreaded conditions; 2) determine the effects of fluid pressure on slip severity; and 3) quantify how fluid pressures vary with instantaneous resultant slipping speed, position on the shoe surface, and throughout the progression of the slip. Eighteen subjects walked on known dry and unexpected slippery floors, while wearing treaded and untreaded shoes. Fluid pressure sensors, embedded in the floor, recorded hydrodynamic pressures during slipping. The maximum fluid pressures (mean+/−standard deviation) were significantly higher for the untreaded conditions (124 +/−75 kPa) than the treaded conditions (1.1 +/−0.29 kPa). Maximum fluid pressures were positively correlated with peak slipping speed (r = 0.87), suggesting that higher fluid pressures, which are associated with untreaded conditions, resulted in more severe slips. Instantaneous resultant slipping speed and position of sensor relative to the shoe sole and walking direction explained 41% of the fluid pressure variability. Fluid pressures were primarily observed for untreaded conditions. This study confirms that fluid pressures are relevant to slipping events, consistent with fluid dynamics theory (i.e. the Reynolds equation), and can be modified with shoe tread design. The results suggest that the occurrence and severity of unexpected slips can be reduced by designing shoes/floors that reduce underfoot fluid pressures. PMID:24267270

Hydrodynamic Relaxation of an Electron Plasma to a Near-Maximum Entropy State

International Nuclear Information System (INIS)

Rodgers, D. J.; Servidio, S.; Matthaeus, W. H.; Mitchell, T. B.; Aziz, T.; Montgomery, D. C.

2009-01-01

Dynamical relaxation of a pure electron plasma in a Malmberg-Penning trap is studied, comparing experiments, numerical simulations and statistical theories of weakly dissipative two-dimensional (2D) turbulence. Simulations confirm that the dynamics are approximated well by a 2D hydrodynamic model. Statistical analysis favors a theoretical picture of relaxation to a near-maximum entropy state with constrained energy, circulation, and angular momentum. This provides evidence that 2D electron fluid relaxation in a turbulent regime is governed by principles of maximum entropy.

Influence of hydrostatic pressure on dynamics and spatial distribution of protein partial molar volume: time-resolved surficial Kirkwood-Buff approach.

Science.gov (United States)

Yu, Isseki; Tasaki, Tomohiro; Nakada, Kyoko; Nagaoka, Masataka

2010-09-30

The influence of hydrostatic pressure on the partial molar volume (PMV) of the protein apomyoglobin (AMb) was investigated by all-atom molecular dynamics (MD) simulations. Using the time-resolved Kirkwood-Buff (KB) approach, the dynamic behavior of the PMV was identified. The simulated time average value of the PMV and its reduction by 3000 bar pressurization correlated with experimental data. In addition, with the aid of the surficial KB integral method, we obtained the spatial distributions of the components of PMV to elucidate the detailed mechanism of the PMV reduction. New R-dependent PMV profiles identified the regions that increase or decrease the PMV under the high pressure condition. The results indicate that besides the hydration in the vicinity of the protein surface, the outer space of the first hydration layer also significantly influences the total PMV change. These results provide a direct and detailed picture of pressure induced PMV reduction.

Magnetization at high pressure in CeP

Science.gov (United States)

Naka, T.; Matsumoto, T.; Okayama, Y.; Môri, N.; Haga, Y.; Suzuki, T.

1995-02-01

We have investigated the pressure dependence of magnetization below 60 K up to 1.6 GPa in the low-carrier concentration system CeP showing two step transitions at T = TL and TH under high pressure. At high pressure, M( P, T) exhibits a maximum at around the lower transition temperature TL. This behavior implies that the magnetic state changes at TL. The pressure dependence of isothermal magnetization M( P) is different above and below TL. In fact, M( P) below TL exhibits a maximum at around 1.4 GPa, whereas M( P) above TL increases steeply with pressure up to 1.6 GPa.

Dynamic performance of power generation systems for off-shore oil and gas platforms

DEFF Research Database (Denmark)

Pierobon, Leonardo; Breuhaus, Peter; Haglind, Fredrik

2014-01-01

%) arises on the prediction of the rotational speed of the high pressure shaft, while the largest deviation (average relative error ~20%) occurs in the evaluation of the pressure at the outlet of the low pressure turbine. As waste heat recovery units (e.g. organic Rankine cycles) are likely...... to be implemented in future off-shore platforms, the proposed model may serve in the design phase for a preliminary assessment of the dynamic response of the power generation system and to evaluate if requirements such as minimum and maximum frequency during transient operation and the recovery time are satisfied......On off-shore oil and gas platforms two or more gas turbines typically support the electrical demand on site by operating as a stand-alone (island) power system. As reliability and availability are major concerns during operation, the dynamic performance of the power generation system becomes...

Molecular Structural Transformation of 2:1 Clay Minerals by a Constant-Pressure Molecular Dynamics Simulation Method

International Nuclear Information System (INIS)

Wang, J.; Gutierre, M.S.

2010-01-01

This paper presents results of a molecular dynamics simulation study of dehydrated 2:1 clay minerals using the Parrinello-Rahman constant-pressure molecular dynamics method. The method is capable of simulating a system under the most general applied stress conditions by considering the changes of MD cell size and shape. Given the advantage of the method, it is the major goal of the paper to investigate the influence of imposed cell boundary conditions on the molecular structural transformation of 2:1 clay minerals under different normal pressures. Simulation results show that the degrees of freedom of the simulation cell (i.e., whether the cell size or shape change is allowed) determines the final equilibrated crystal structure of clay minerals. Both the MD method and the static method have successfully revealed unforeseen structural transformations of clay minerals upon relaxation under different normal pressures. It is found that large shear distortions of clay minerals occur when full allowance is given to the cell size and shape change. A complete elimination of the interlayer spacing is observed in a static simulation. However, when only the cell size change is allowed, interlayer spacing is retained, but large internal shear stresses also exist.

Dynamic airway pressure-time curve profile (Stress Index): a systematic review.

Science.gov (United States)

Terragni, Pierpaolo; Bussone, Guido; Mascia, Luciana

2016-01-01

The assessment of respiratory mechanics at the bedside is necessary in order to identify the most protective ventilatory strategy. Indeed in the last 20 years, adverse effects of positive ventilation to the lung structures have led to a reappraisal of the objectives of mechanical ventilation. The ventilator setting requires repeated readjustment over the period of mechanical ventilation dependency and careful respiratory monitoring to minimize the risks, preventing further injury and permitting the lung and airways healing. Among the different methods that have been proposed and validated, the analysis of dynamic P-t curve (named Stress Index, SI) represents an adequate tool available at the bedside, repeatable and, therefore, able to identify the amount of overdistension occurring in the daily clinical practice, when modifying positive end-expiratory pressure. In this review we will analyze the evidence that supports respiratory mechanics assessment at the bedside and the application of the dynamic P/t curve profile (SI) to optimize protective ventilation in patients with acute respiratory failure.

Assessment of wheel propeller contact pressure upon soil with use of tire universal performance

Directory of Open Access Journals (Sweden)

Z. A. Godzhaev

2016-01-01

Full Text Available A maximum contact pressure is a key parameter characterizing a level of ecological impact of tractor propellers on the soil. The maximum pressure upon the soil varies with internal pressure in tires and vertical load of a wheel. An universal tire performance can be used at an assessment of change of contact pressure of a wheel propeller upon the soil. The authors offered a technique of definition and regulation of the maximum contact pressure of the wheel propeller upon the basic basis. This technique allows to set parameters for monitoring systems and regulation of the maximum pressure upon the soil by measurement of a tire deflection and change of pressure in tires. At statistical tests for determination of the maximum contact pressure it is necessary to consider the universal performance of the tire nomographically. This nomogram allows to consider visually influence of loading and internal pressure in the tire on a size of the maximum contact pressure. An internal pressure decrease in the tire makes it possible to reduce the maximum pressure upon the soil at constant loading. The authors investigated universal performances of the tires in the range of change of internal air pressure from 160 to 90 kPas. Change of internal pressure from 150 to 100 kPas reduce for the tire 15,5R38 the maximum contact pressure upon 13 kPas (9,6 percent: from 135 to 122 kPas. That corresponds to the admissible level of pressure upon the soil at its humidity in a layer of 0-30 cm: 0,5-0,6 minimum moisture-holding capacity during the spring period and 0,6-0,7 minimum moisture-holding capacity during the autumn period. In case of use of the tire 16,9R38 the maximum pressure upon the soil decreases from 84 to 75 kPas, that is by 10,4 percent.

Minimal length, Friedmann equations and maximum density

Energy Technology Data Exchange (ETDEWEB)

Awad, Adel [Center for Theoretical Physics, British University of Egypt,Sherouk City 11837, P.O. Box 43 (Egypt); Department of Physics, Faculty of Science, Ain Shams University,Cairo, 11566 (Egypt); Ali, Ahmed Farag [Centre for Fundamental Physics, Zewail City of Science and Technology,Sheikh Zayed, 12588, Giza (Egypt); Department of Physics, Faculty of Science, Benha University,Benha, 13518 (Egypt)

2014-06-16

Inspired by Jacobson’s thermodynamic approach, Cai et al. have shown the emergence of Friedmann equations from the first law of thermodynamics. We extend Akbar-Cai derivation http://dx.doi.org/10.1103/PhysRevD.75.084003 of Friedmann equations to accommodate a general entropy-area law. Studying the resulted Friedmann equations using a specific entropy-area law, which is motivated by the generalized uncertainty principle (GUP), reveals the existence of a maximum energy density closed to Planck density. Allowing for a general continuous pressure p(ρ,a) leads to bounded curvature invariants and a general nonsingular evolution. In this case, the maximum energy density is reached in a finite time and there is no cosmological evolution beyond this point which leaves the big bang singularity inaccessible from a spacetime prospective. The existence of maximum energy density and a general nonsingular evolution is independent of the equation of state and the spacial curvature k. As an example we study the evolution of the equation of state p=ωρ through its phase-space diagram to show the existence of a maximum energy which is reachable in a finite time.

Pneumatic pressure wave generator provides economical, simple testing of pressure transducers

Science.gov (United States)

Gaal, A. E.; Weldon, T. P.

1967-01-01

Testing device utilizes the change in pressure about a bias or reference pressure level produced by displacement of a center-driven piston in a closed cylinder. Closely controlled pneumatic pressure waves allow testing under dynamic conditions.

New system for measuring and controlling the maximum pressing pressure in the holes of the mould: ISOPRESS; Nuevo sistema para la medida y control de la presion maxima de prensado en los alveolos del molde: ISOPRESS

Energy Technology Data Exchange (ETDEWEB)

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)

Interactions of Delta Shock Waves for Zero-Pressure Gas Dynamics with Energy Conservation Law

OpenAIRE

Wei Cai; Yanyan Zhang

2016-01-01

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.

Modelling Hermetic Compressors Using Different Constraint Equations to Accommodate Multibody Dynamics and Hydrodynamic Lubrication

DEFF Research Database (Denmark)

Estupinan, Edgar Alberto; Santos, Ilmar

2009-01-01

elements are supported by fluid film bearings, where the hydrodynamic interaction forces are described by the Reynolds equation. The system of nonlinear equations is numerically solved for three different restrictive conditions of the motion of the crank, where the third case takes into account lateral...... and tilting oscillations of the extremity of the crankshaft. The numerical results of the behaviour of the journal bearings for each case are presented giving some insights into design parameters such as, maximum oil film pressure, minimum oil film thickness, maximum vibration levels and dynamic reaction...

Separation Dynamics of Controlled Internal Flow in an Adverse Pressure Gradient

Science.gov (United States)

Peterson, C. J.; Vukasinovic, B.; Glezer, A.

2017-11-01

The effects of fluidic actuation on the dynamic evolution of aggressive internal flow separation is investigated at speeds up to M = 0.4 within a constant-width diffuser branching off of a primary flow duct. It is shown that a spanwise array of fluidic actuators upstream of the separation actively controls the flow constriction (and losses) within the diffuser and consequently the local pressure gradient at its entrance. The effectiveness of the actuation, as may be measured by the increased flow rate that is diverted through the diffuser, scales with its flow rate coefficient. In the presence of actuation (0.7% mass fraction), the mass flow rate in the primary duct increases by 10% while the fraction of the diverted mass flow rate in the diffuser increases by more than 45%. The flow dynamics near separation in the absence and presence of actuation are characterized using high speed particle image velocimetry and analyzed using proper orthogonal and spectral decompositions. In particular, the spectral contents of the incipient boundary layer separation are compared in the absence and presence of actuation with emphasis on the changes in local dynamics near separation as the characteristic cross stream scale of the boundary layer increases with separation delay.

High temperature piezoresistive {beta}-SiC-on-SOI pressure sensor for combustion engines

Energy Technology Data Exchange (ETDEWEB)

Berg, J. von; Ziermann, R.; Reichert, W.; Obermeier, E. [Tech. Univ. Berlin (Germany). Microsensor and Actuator Technol. Center; Eickhoff, M.; Kroetz, G. [Daimler Benz AG, Munich (Germany); Thoma, U.; Boltshauser, T.; Cavalloni, C. [Kistler Instrumente AG, Winterthur (Switzerland); Nendza, J.P. [TRW Deutschland GmbH, Barsinghausen (Germany)

1998-08-01

For measuring the cylinder pressure in combustion engines of automobiles a high temperature pressure sensor has been developed. The sensor is made of a membrane based piezoresistive {beta}-SiC-on-SOI (SiCOI) sensor chip and a specially designed housing. The SiCOI sensor was characterized under static pressures of up to 200 bar in the temperature range between room temperature and 300 C. The sensitivity of the sensor at room temperature is approximately 0.19 mV/bar and decreases to about 0.12 mV/bar at 300 C. For monitoring the dynamic cylinder pressure the sensor was placed into the combustion chamber of a gasoline engine. The measurements were performed at 1500 rpm under different loads, and for comparison a quartz pressure transducer from Kistler AG was used as a reference. The maximum pressure at partial load operation amounts to about 15 bar. The difference between the calibrated SiCOI sensor and the reference sensor is significantly less than 1 bar during the whole operation. (orig.) 8 refs.

Mass Transport Properties of LiD-U Mixtures from Orbital FreeMolecular Dynamics Simulations and a Pressure-Matching Mixing Rule

International Nuclear Information System (INIS)

Burakovsky, Leonid; Kress, Joel D.; Collins, Lee A.

2012-01-01

Mass transport properties for LiD-U mixtures were calculated using a pressure matching mixture rule for the mixing of LiD and of U properties simulated with Orbital Free Molecular Dynamics (OFMD). The mixing rule was checked against benchmark OFMD simulations for the fully interacting three-component (Li, D, U) system. To obtain transport coefficients for LiD-U mixtures of different (LiD) x U (1-x) compositions as functions of temperature and mixture density is a tedious task. Quantum molecular dynamics (MD) simulations can be employed, as in the case LiD or U. However, due to the presence of the heavy constituent U, such simulations proceed so slowly that only a limited number of numerical data points in the (x, ρ, T) phase space can be obtained. To finesse this difficulty, transport coefficients for a mixture can be obtained using a pressure-matching mixing rule discussed. For both LiD and U, the corresponding transport coefficients were obtained earlier from quantum molecular dynamics simulations. In these simulations, the quantum behavior of the electrons was represented using an orbital free (OF) version of density functional theory, and ions were advanced in time using classical molecular dynamics. The total pressure of the system, P = nk B T/V + P e , is the sum of the ideal gas pressure of the ions plus the electron pressure. The mass self-diffusion coefficient for species α, D α , the mutual diffusion coefficient for species α and β, Dαβ, and the shear viscosity, η, are computed from the appropriate autocorrelation function. The details of similar QMD calculations on LiH are described in Ref. [1] for 0.5 eV < T < 3 eV, and in Ref. [2] for 2 eV < T < 6 eV.

Electron dynamics and plasma jet formation in a helium atmospheric pressure dielectric barrier discharge jet

Energy Technology Data Exchange (ETDEWEB)

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.

Linearized semiclassical initial value time correlation functions with maximum entropy analytic continuation.

Science.gov (United States)

Liu, Jian; Miller, William H

2008-09-28

The maximum entropy analytic continuation (MEAC) method is used to extend the range of accuracy of the linearized semiclassical initial value representation (LSC-IVR)/classical Wigner approximation for real time correlation functions. LSC-IVR provides a very effective "prior" for the MEAC procedure since it is very good for short times, exact for all time and temperature for harmonic potentials (even for correlation functions of nonlinear operators), and becomes exact in the classical high temperature limit. This combined MEAC+LSC/IVR approach is applied here to two highly nonlinear dynamical systems, a pure quartic potential in one dimensional and liquid para-hydrogen at two thermal state points (25 and 14 K under nearly zero external pressure). The former example shows the MEAC procedure to be a very significant enhancement of the LSC-IVR for correlation functions of both linear and nonlinear operators, and especially at low temperature where semiclassical approximations are least accurate. For liquid para-hydrogen, the LSC-IVR is seen already to be excellent at T=25 K, but the MEAC procedure produces a significant correction at the lower temperature (T=14 K). Comparisons are also made as to how the MEAC procedure is able to provide corrections for other trajectory-based dynamical approximations when used as priors.

Maximum mass of magnetic white dwarfs

International Nuclear Information System (INIS)

Paret, Daryel Manreza; Horvath, Jorge Ernesto; Martínez, Aurora Perez

2015-01-01

We revisit the problem of the maximum masses of magnetized white dwarfs (WDs). The impact of a strong magnetic field on the structure equations is addressed. The pressures become anisotropic due to the presence of the magnetic field and split into parallel and perpendicular components. We first construct stable solutions of the Tolman-Oppenheimer-Volkoff equations for parallel pressures and find that physical solutions vanish for the perpendicular pressure when B ≳ 10 13 G. This fact establishes an upper bound for a magnetic field and the stability of the configurations in the (quasi) spherical approximation. Our findings also indicate that it is not possible to obtain stable magnetized WDs with super-Chandrasekhar masses because the values of the magnetic field needed for them are higher than this bound. To proceed into the anisotropic regime, we can apply results for structure equations appropriate for a cylindrical metric with anisotropic pressures that were derived in our previous work. From the solutions of the structure equations in cylindrical symmetry we have confirmed the same bound for B ∼ 10 13 G, since beyond this value no physical solutions are possible. Our tentative conclusion is that massive WDs with masses well beyond the Chandrasekhar limit do not constitute stable solutions and should not exist. (paper)

The Effects of Solar Wind Dynamic Pressure Changes on the Substorm Auroras and Energetic Electron Injections on 24 August 2005

Science.gov (United States)

Li, L. Y.; Wang, Z. Q.

2018-01-01

After the passage of an interplanetary (IP) shock at 06:13 UT on 24 August 2005, the enhancement (>6 nPa) of solar wind dynamic pressure and the southward turning of interplanetary magnetic field (IMF) cause the earthward movement of dayside magnetopause and the drift loss of energetic particles near geosynchronous orbit. The persistent electron drift loss makes the geosynchronous satellites cannot observe the substorm electron injection phenomenon during the two substorm expansion phases (06:57-07:39 UT) on that day. Behind the IP shock, the fluctuations ( 0.5-3 nPa) of solar wind dynamic pressure not only alter the dayside auroral brightness but also cause the entire auroral oval to swing in the day-night direction. However, there is no Pi2 pulsation in the nightside auroral oval during the substorm growth phase from 06:13 to 06:57 UT. During the subsequent two substorm expansion phases, the substorm expansion activities cause the nightside aurora oval brightening from substorm onset site to higher latitudes, and meanwhile, the enhancement (decline) of solar wind dynamic pressure makes the nightside auroral oval move toward the magnetic equator (the magnetic pole). These observations demonstrate that solar wind dynamic pressure changes and substorm expansion activities can jointly control the luminosity and location of the nightside auroral oval when the internal and external disturbances occur simultaneously. During the impact of a strong IP shock, the earthward movement of dayside magnetopause probably causes the disappearance of the substorm electron injections near geosynchronous orbit.

Molecular dynamics simulations of tension–compression asymmetry in nanocrystalline copper

Energy Technology Data Exchange (ETDEWEB)

Zhou, Kai, E-mail: kaizhou@aliyun.com; Liu, Bin; Shao, Shaofeng; Yao, Yijun

2017-04-04

Molecular dynamics simulations are used to investigate uniaxial tension and compression of nanocrystalline copper with mean grain sizes of 3.8–11.9 nm. The simulation results show an apparent asymmetry in the flow stress, with nanocrystalline copper stronger in compression than in tension. The asymmetry exhibits a maximum at the mean grain size of about 10 nm. The dominant mechanism of the asymmetry depends on the mean grain size. At small grain sizes, grain-boundary based plasticity dominates the asymmetry, while for large grain sizes the asymmetry mainly arises from the pressure dependent dislocation emission from grain boundaries. - Highlights: • The tension–compression asymmetry in strength exhibits a maximum at the mean grain size of about 10 nm. • The main mechanisms govern the asymmetry are grain-boundary mediated plasticity and dislocation based plasticity. • The above-mentioned mechanisms are both grain size and pressure dependent. • The transition of the asymmetry with the mean grain size is not influenced by strain rate.

Sloshing of water in annular pressure-suppression pool of boiling water reactors under earthquake ground motions

International Nuclear Information System (INIS)

Aslam, M.; Godden, W.G.; Scalise, D.T.

1979-10-01

This report presents an analytical investigation of the sloshing response of water in annular-circular as well as simple-circular tanks under horizontal earthquake ground motions, and the results are verified with tests. This study was motivated because of the use of annular tanks for pressure-suppression pools in Boiling Water Reactors. Such a pressure-suppression pool would typically have 80 ft and 120 ft inside and outside diameters and a water depth of 20 ft. The analysis was based upon potential flow theory and a computer program was written to obtain time-history plots of sloshing displacements of water and the dynamic pressures. Tests were carried out on 1/80th and 1/15th scale models under sinusoidal as well as simulated earthquake ground motions. Tests and analytical results regarding the natural frequencies, surface water displacements, and dynamic pressures were compared and a good agreement was found for relatively small displacements. The computer program gave satisfactory results as long as the maximum water surface displacements were less than 30 in., which is roughly the value obtained under full intensity of El Centro earthquake

Interactions of Delta Shock Waves for Zero-Pressure Gas Dynamics with Energy Conservation Law

Directory of Open Access Journals (Sweden)

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.

Modelling the Dynamic Interaction Power System Lamp - Application to High Pressure Mercury Gas Discharge Lamps

Directory of Open Access Journals (Sweden)

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.

Observation of a New High-Pressure Solid Phase in Dynamically Compressed Aluminum

Science.gov (United States)

Polsin, D. N.

2017-10-01

Aluminum is ideal for testing theoretical first-principles calculations because of the relative simplicity of its atomic structure. Density functional theory (DFT) calculations predict that Al transforms from an ambient-pressure, face-centered-cubic (fcc) crystal to the hexagonal close-packed (hcp) and body-centered-cubic (bcc) structures as it is compressed. Laser-driven experiments performed at the University of Rochester's Laboratory for Laser Energetics and the National Ignition Facility (NIF) ramp compressed Al samples to pressures up to 540 GPa without melting. Nanosecond in-situ x-ray diffraction was used to directly measure the crystal structure at pressures where the solid-solid phase transformations of Al are predicted to occur. Laser velocimetry provided the pressure in the Al. Our results show clear evidence of the fcc-hcp and hpc-bcc transformations at 216 +/- 9 GPa and 321 +/- 12 GPa, respectively. This is the first experimental in-situ observation of the bcc phase in compressed Al and a confirmation of the fcc-hcp transition previously observed under static compression at 217 GPa. The observations indicate these solid-solid phase transitions occur on the order of tens of nanoseconds time scales. In the fcc-hcp transition we find the original texture of the sample is preserved; however, the hcp-bcc transition diminishes that texture producing a structure that is more polycrystalline. The importance of this dynamic is discussed. The NIF results are the first demonstration of x-ray diffraction measurements at two different pressures in a single laser shot. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Pressure test method for reactor pressure vessel in construction field

International Nuclear Information System (INIS)

Takeda, Masakado; Ushiroda, Koichi; Miyahara, Ryohei; Takano, Hiroshi; Matsuura, Tadashi; Sato, Keiya.

1998-01-01

Plant constitutional parts as targets of both of a primary pressure test and a secondary pressure test are disposed in communication with a reactor pressure vessel, and a pressure of the primary pressure test is applied to the targets of both tests, so that the primary pressure test and the second pressure test are conducted together. Since the number of pressure tests can be reduced to promote construction, and the number of workers can also be reduced. A pressure exceeding the maximum pressure upon use is applied to the pressure vessel after disposing the incore structures, to continuously conduct the primary pressure test and the secondary pressure test joined together and an incore flowing test while closing the upper lid of the pressure vessel as it is in the construction field. The number of opening/closing of the upper lid upon conducting every test can be reduced, and since the pressure resistance test is conducted after arranging circumference conditions for the incore flowing test, the tests can be conducted collectively also in view of time. (N.H.)

Latitudinal distribution of the solar wind properties in the low- and high-pressure regimes: Wind observations

Directory of Open Access Journals (Sweden)

C. Lacombe

Full Text Available The solar wind properties depend on λ, the heliomagnetic latitude with respect to the heliospheric current sheet (HCS, more than on the heliographic latitude. We analyse the wind properties observed by Wind at 1 AU during about 2.5 solar rotations in 1995, a period close to the last minimum of solar activity. To determine λ, we use a model of the HCS which we fit to the magnetic sector boundary crossings observed by Wind. We find that the solar wind properties mainly depend on the modulus |λ|. But they also depend on a local parameter, the total pressure (magnetic pressure plus electron and proton thermal pressure. Furthermore, whatever the total pressure, we observe that the plasma properties also depend on the time: the latitudinal gradients of the wind speed and of the proton temperature are not the same before and after the closest HCS crossing. This is a consequence of the dynamical stream interactions. In the low pressure wind, at low |λ|, we find a clear maximum of the density, a clear minimum of the wind speed and of the proton temperature, a weak minimum of the average magnetic field strength, a weak maximum of the average thermal pressure, and a weak maximum of the average β factor. This overdense sheet is embedded in a density halo. The latitudinal thickness is about 5^° for the overdense sheet, and 20^° for the density halo. The HCS is thus wrapped in an overdense sheet surrounded by a halo, even in the non-compressed solar wind. In the high-pressure wind, the plasma properties are less well ordered as functions of the latitude than in the low-pressure wind; the minimum of the average speed is seen before the HCS crossing. The latitudinal thickness of the high-pressure region is about 20^°. Our observations are qualitatively consistent with the numerical model of Pizzo for the deformation of the heliospheric current sheet and plasma sheet.

Key words: Interplanetary physics (solar wind

Froude number fractions to increase walking pattern dynamic similarities: application to plantar pressure study in healthy subjects.

Science.gov (United States)

Moretto, P; Bisiaux, M; Lafortune, M A

2007-01-01

The purpose of this study was to determine if using similar walking velocities obtained from fractions of the Froude number (N(Fr)) and leg length can lead to kinematic and kinetic similarities and lower variability. Fifteen male subjects walked on a treadmill at 0.83 (VS(1)) and 1.16ms(-1) (VS(2)) and then at two similar velocities (V(Sim27) and V(Sim37)) determined from two fractions of the N(Fr) (0.27 and 0.37) so that the average group velocity remained unchanged in both conditions (VS(1)=V (Sim27)andVS(2)=V (Sim37)). N(Fr) can theoretically be used to determine walking velocities proportional to leg lengths and to establish dynamic similarities between subjects. This study represents the first attempt at using this approach to examine plantar pressure. The ankle and knee joint angles were studied in the sagittal plane and the plantar pressure distribution was assessed with an in-shoe measurement device. The similarity ratios were computed from anthropometric parameters and plantar pressure peaks. Dynamically similar conditions caused a 25% reduction in leg joint angles variation and a 10% significant decrease in dimensionless pressure peak variability on average of five footprint locations. It also lead to heel and under-midfoot pressure peaks proportional to body mass and to an increase in the number of under-forefoot plantar pressure peaks proportional to body mass and/or leg length. The use of walking velocities derived from N(Fr) allows kinematic and plantar pressure similarities between subjects to be observed and leads to a lower inter-subject variability. In-shoe pressure measurements have proven to be valuable for the understanding of lower extremity function. Set walking velocities used for clinical assessment mask the effects of body size and individual gait mechanics. The anthropometric scaling of walking velocities (fraction of N(Fr)) should improve identification of unique walking strategies and pathological foot functions.

Prediction of fluctuating pressure environments associated with plume-induced separated flow fields

Science.gov (United States)

Plotkin, K. J.

1973-01-01

The separated flow environment induced by underexpanded rocket plumes during boost phase of rocket vehicles has been investigated. A simple semi-empirical model for predicting the extent of separation was developed. This model offers considerable computational economy as compared to other schemes reported in the literature, and has been shown to be in good agreement with limited flight data. The unsteady pressure field in plume-induced separated regions was investigated. It was found that fluctuations differed from those for a rigid flare only at low frequencies. The major difference between plume-induced separation and flare-induced separation was shown to be an increase in shock oscillation distance for the plume case. The prediction schemes were applied to PRR shuttle launch configuration. It was found that fluctuating pressures from plume-induced separation are not as severe as for other fluctuating environments at the critical flight condition of maximum dynamic pressure.

Potential hydrogen and oxygen partial pressures in legacy plutonium oxide packages at Oak Ridge

Energy Technology Data Exchange (ETDEWEB)

Veirs, Douglas K. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-07-07

An approach to estimate the maximum hydrogen and oxygen partial pressures within sealed containers is described and applied to a set of packages containing high-purity plutonium dioxide. The approach uses experimentally determined maximum hydrogen and oxygen partial pressures and scales the experimentally determined pressures to the relevant packaged material properties. The important material properties are the specific wattage and specific surface area (SSA). Important results from the experimental determination of maximum partial pressures are (1) the ratio of hydrogen to oxygen is stoichiometric, and (2) the maximum pressures increase with increasing initial rates of production. The material properties that influence the rates are the material specific wattage and the SSA. The unusual properties of these materials, high specific wattage and high SSA, result in higher predicted maximum pressures than typical plutonium dioxide in storage. The pressures are well within the deflagration range for mixtures of hydrogen and oxygen.

Probabilistic modelling of the high-pressure arc cathode spot displacement dynamic

International Nuclear Information System (INIS)

Coulombe, Sylvain

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 -tilde1 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. oxide-contaminated cathode surface). Through an appropriate choice of the local probabilistic displacement rules, the model is able to correctly represent the dynamic behaviours of the type-A cathode spot, including the FPS for the arc elongation (i.e. voltage) and the arc erosion trace formation. The model illustrates that the cathode spot displacements between re-strikes can be seen as a diffusion process with a diffusion constant which depends on the surface structure. A physical interpretation for the jumping probability associated with the re-strike event is given in terms of the electron emission processes across dielectric contaminants present on the cathode surface

[Intracranial pressure monitoring and CSF dynamics in patients with neurological disorders: indications and practical considerations].

Science.gov (United States)

Poca, M; Sahuquillo, J

2001-01-01

The study of cerebrospinal fluid (CSF) dynamics is central to the diagnosis of adult chronic hydrocephalus (ACH). At present, many neurology and neurosurgery departments use one or more tests to guide diagnosis of this syndrome and to predict patient response to shunting. In specialised centres, the study of CSF dynamics is combined with continuous intracranial pressure (ICP) monitoring. Determination of several variables of CSF dynamics and definitions of qualitative and quantitative characteristics of ICP can be used to establish whether the hydrocephalus is active, compensated or arrested. CSF dynamics and ICP monitoring can also be used to check the correct functioning of the shunt and can be of use in the clinical management of patients with pseudotumor cerebri. Moreover, ICP monitoring is used to guide the treatment of several acute neurological processes. The aim of this review is to describe the fundamentals of CSF dynamics studies and the bases of continuous ICP monitoring. The advantages and disadvantages of several hydrodynamic tests that can be performed by lumbar puncture, as well as the normal and abnormal characteristics of an ICP recording, are discussed.

Where do winds come from? A new theory on how water vapor condensation influences atmospheric pressure and dynamics

Science.gov (United States)

Makarieva, A. M.; Gorshkov, V. G.; Sheil, D.; Nobre, A. D.; Li, B.-L.

2013-01-01

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.

Design and Computational Fluid Dynamics Optimization of the Tube End Effector for Reactor Pressure Vessel Head Type VVER-1000

International Nuclear Information System (INIS)

Novosel, D.

2006-01-01

In this paper is presented development and optimization of the tube end effector design which should consist of 4 ultrasonic transducers, 4 Eddy Current's transducers and Radiation Proof Dot Camera. Basically, designing was conducted by main input requests, such as: inner diameter of a tested reactor pressure vessel head penetration tube, dimensions of a transducers and maximum allowable vertical movement of a manipulator connection rod in order to cover all inner tube surface. As is obvious, for ultrasonic testing should be provided the thin layer of liquid material (in our case water was chosen) which is necessary to make physical contact between transducer surface and investigated inner tube surface. By help of Computational Fluid Dynamics, determined were parameters of geometry, as the most important factor of transducer housing, hydraulically parameters for water supply and primary drain together implemented into this housing, movement of the end effectors (vertical and cylindrical) and finally, necessary equipment which has to provide all hydraulically and pneumatic requirements. As the cylindrical surface of the inner tube diameter was liquefied and contact between transducer housing and tested tube wasn't ideally covered, water leakage could occur in downstream direction. To reduce water leakage, which is highly contaminated, developed was second water drain by diffuser assembly which is driven by Venturi pipe, commercially called vacuum generator. Using the Computational Fluid Dynamic, obtained was optimized geometry of diffuser control volume with the highest efficiency, in other words, unobstructed fluid flux. Afterwards, the end effectors system was synchronized to the existing operable system for NDT methods all invented and designed by INETEC. (author)

Porphyry-Copper Ore Shells Form at Stable Pressure-Temperature Fronts Within Dynamic Fluid Plumes

Science.gov (United States)

Weis, P.; Driesner, T.; Heinrich, C. A.

2012-12-01

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.

Solvation pressure as real pressure: I. Ethanol and starch under negative pressure

CERN Document Server

Uden, N W A V; Faux, D A; Tanczos, A C; Howlin, B; Dunstan, D J

2003-01-01

The reality of the solvation pressure generated by the cohesive energy density of liquids is demonstrated by three methods. Firstly, the Raman spectrum of ethanol as a function of cohesive energy density (solvation pressure) in ethanol-water and ethanol-chloroform mixtures is compared with the Raman spectrum of pure ethanol under external hydrostatic pressure and the solvation pressure and hydrostatic pressure are found to be equivalent for some transitions. Secondly, the bond lengths of ethanol are calculated by molecular dynamics modelling for liquid ethanol under pressure and for ethanol vapour. The difference in bond lengths between vapour and liquid are found to be equivalent to the solvation pressure for the C-H sub 3 , C-H sub 2 and O-H bond lengths, with discrepancies for the C-C and C-O bond lengths. Thirdly, the pressure-induced gelation of potato starch is measured in pure water and in mixtures of water and ethanol. The phase transition pressure varies in accordance with the change in solvation pre...

Lattice Dynamics Study of Phonon Instability and Thermal Properties of Type-I Clathrate K8Si46 under High Pressure

Directory of Open Access Journals (Sweden)

Wei Zhang

2016-07-01

Full Text Available For a further understanding of the phase transitions mechanism in type-I silicon clathrates K8Si46, ab initio self-consistent electronic calculations combined with linear-response method have been performed to investigate the vibrational properties of alkali metal K atoms encapsulated type-I silicon-clathrate under pressure within the framework of density functional perturbation theory. Our lattice dynamics simulation results showed that the pressure induced phase transition of K8Si46 was believed to be driven by the phonon instability of the calthrate lattice. Analysis of the evolution of the partial phonon density of state with pressure, a legible dynamic picture for both guest K atoms and host lattice, was given. In addition, based on phonon calculations and combined with quasi-harmonic approximation, the specific heat of K8Si46 was derived, which agreed very well with experimental results. Also, other important thermal properties including the thermal expansion coefficients and Grüneisen parameters of K8Si46 under different temperature and pressure were also predicted.

Neutron scattering studies of the dynamics of biological systems as a function of hydration, temperature and pressure

International Nuclear Information System (INIS)

Trapp, Marcus

2010-01-01

Incoherent elastic and quasi-elastic neutron scattering were used to measure membrane and protein dynamics in the nano- to picosecond time and Angstrom length scale. The hydration dependent dynamics of DMPC model membranes was studied using elastic and quasi-elastic neutron scattering. The elastic experiments showed a clear shift of the temperature of the main phase transition to higher temperatures with decreasing hydration level. The performed quasi-elastic measurements demonstrated nicely the influence, hydration has on the diffusive motions of the head lipid groups. Different models are necessary to fit the Q-dependence of the elastic incoherent structure factor and show therefore the reduced mobility as a result of reduced water content. In addition to temperature, pressure as a second thermodynamic variable was used to explore dynamics of DMPC membranes. The ordering introduced by applying pressure has similar effect to decreased hydration, therefore both approaches are complementary. Covering three orders of magnitude in observation time, the dynamics of native AChE and its complexed counterpart in presence of Huperzin A was investigated in the range from 1 ns to 100 ps. The mean square displacements obtained from the elastic data allowed the determination of activation energies and gave evidence that a hierarchy of motions contributes to the enzymatic activity. Diffusion constants and residence times were extracted from the quasi-elastic broadening. (author) [fr

Solar radiation pressure resonances in Low Earth Orbits

Science.gov (United States)

Alessi, Elisa Maria; Schettino, Giulia; Rossi, Alessandro; Valsecchi, Giovanni B.

2018-01-01

The aim of this work is to highlight the crucial role that orbital resonances associated with solar radiation pressure can have in Low Earth Orbit. We review the corresponding literature, and provide an analytical tool to estimate the maximum eccentricity which can be achieved for well-defined initial conditions. We then compare the results obtained with the simplified model with the results obtained with a more comprehensive dynamical model. The analysis has important implications both from a theoretical point of view, because it shows that the role of some resonances was underestimated in the past, and also from a practical point of view in the perspective of passive deorbiting solutions for satellites at the end-of-life.

Thermodynamic and Dynamic Causes of Pluvial Conditions During the Last Glacial Maximum in Western North America

Science.gov (United States)

Morrill, Carrie; Lowry, Daniel P.; Hoell, Andrew

2018-01-01

During the last glacial period, precipitation minus evaporation increased across the currently arid western United States. These pluvial conditions have been commonly explained for decades by a southward deflection of the jet stream by the Laurentide Ice Sheet. Here analysis of state-of-the-art coupled climate models shows that effects of the Laurentide Ice Sheet on the mean circulation were more important than storm track changes in generating wet conditions. Namely, strong cooling by the ice sheet significantly reduced humidity over land, increasing moisture advection in the westerlies due to steepened humidity gradients. Additionally, the removal of moisture from the atmosphere by mass divergence associated with the subtropical high was diminished at the Last Glacial Maximum compared to present. These same dynamic and thermodynamic factors, working in the opposite direction, are projected to cause regional drying in western North America under increased greenhouse gas concentrations, indicating continuity from past to future in the mechanisms altering hydroclimate.

Radiation Belt Transport Driven by Solar Wind Dynamic Pressure Fluctuations

Science.gov (United States)

Kress, B. T.; Hudson, M. K.; Ukhorskiy, A. Y.; Mueller, H.

2012-12-01

The creation of the Earth's outer zone radiation belts is attributed to earthward transport and adiabatic acceleration of electrons by drift-resonant interactions with electromagnetic fluctuations in the magnetosphere. Three types of radial transport driven by solar wind dynamic pressure fluctuations that have been identified are: (1) radial diffusion [Falthammer, 1965], (2) significant changes in the phase space density radial profile due to a single or few ULF drift-resonant interactions [Ukhorskiy et al., 2006; Degeling et al., 2008], and (3) shock associated injections of radiation belt electrons occurring in less than a drift period [Li et al., 1993]. A progress report will be given on work to fully characterize different forms of radial transport and their effect on the Earth's radiation belts. The work is being carried out by computing test-particle trajectories in electric and magnetic fields from a simple analytic ULF field model and from global MHD simulations of the magnetosphere. Degeling, A. W., L. G. Ozeke, R. Rankin, I. R. Mann, and K. Kabin (2008), Drift resonant generation of peaked relativistic electron distributions by Pc 5 ULF waves, textit{J. Geophys. Res., 113}, A02208, doi:10.1029/2007JA012411. Fälthammar, C.-G. (1965), Effects of Time-Dependent Electric Fields on Geomagnetically Trapped Radiation, J. Geophys. Res., 70(11), 2503-2516, doi:10.1029/JZ070i011p02503. Li, X., I. Roth, M. Temerin, J. R. Wygant, M. K. Hudson, and J. B. Blake (1993), Simulation of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC, textit{Geophys. Res. Lett., 20}(22), 2423-2426, doi:10.1029/93GL02701. Ukhorskiy, A. Y., B. J. Anderson, K. Takahashi, and N. A. Tsyganenko (2006), Impact of ULF oscillations in solar wind dynamic pressure on the outer radiation belt electrons, textit{Geophys. Res. Lett., 33}(6), L06111, doi:10.1029/2005GL024380.

Heat Convection at the Density Maximum Point of Water

Science.gov (United States)

Balta, Nuri; Korganci, Nuri

2018-01-01

Water exhibits a maximum in density at normal pressure at around 4° degree temperature. This paper demonstrates that during cooling, at around 4 °C, the temperature remains constant for a while because of heat exchange associated with convective currents inside the water. Superficial approach implies it as a new anomaly of water, but actually it…

Plastic Deformation of Pressured Metallic Glass

Directory of Open Access Journals (Sweden)

Yun Cheng

2017-11-01

Full Text Available Although pressured metallic glass (MG has been reported in the literature; there are few studies focusing on pressure effects on the structure; dynamics and its plastic deformation. In this paper; we report on and characterize; via molecular dynamics simulation, the structure and dynamics heterogeneity of pressured MGs, and explore a causal link between local structures and plastic deformation mechanism of pressured glass. The results exhibit that the dynamical heterogeneity of metallic liquid is more pronounced at high pressure, while the MGs were less fragile after the release of external pressure, reflected by the non-Gaussian parameter (NGP. High pressure glass shows better plastic deformation; and the local strain zone distributed more uniformly than of in normal glass. Further research indicates that although the number of icosahedrons in pressured glass was much larger than that in normal glass, while the interpenetrating connections of icosahedra (ICOI exhibited spatial correlations were rather poor; In addition, the number of ‘fast’ atoms indexed by the atoms’ moving distance is larger than that in normal glass; leading to the sharp decreasing in number of icosahedrons during deformation. An uniform distribution of ‘fast’ atoms also contributed to better plastic deformation ability in the pressured glass. These findings may suggest a link between the deformation and destruction of icosahedra with short-range order.

Computational Fluid Dynamic Pressure Drop Estimation of Flow between Parallel Plates

Energy Technology Data Exchange (ETDEWEB)

Son, Hyung Min; Yang, Soo Hyung; Park, Jong Hark [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-10-15

Many pool type reactors have forced downward flows inside the core during normal operation; there is a chance of flow inversion when transients occur. During this phase, the flow undergo transition between turbulent and laminar regions where drastic changes take place in terms of momentum and heat transfer, and the decrease in safety margin is usually observed. Additionally, for high Prandtl number fluids such as water, an effect of the velocity profile inside the channel on the temperature distribution is more pronounced over the low Prandtl number ones. This makes the checking of its pressure drop estimation accuracy less important, assuming the code verification is complete. With an advent of powerful computer hardware, engineering applications of computational fluid dynamics (CFD) methods have become quite common these days. Especially for a fully-turbulent and single phase convective heat transfer, the predictability of the commercial codes has matured enough so that many well-known companies adopt those to accelerate a product development cycle and to realize an increased profitability. In contrast to the above, the transition models for the CFD code are still under development, and the most of the models show limited generality and prediction accuracy. Unlike the system codes, the CFD codes estimate the pressure drop from the velocity profile which is obtained by solving momentum conservation equations, and the resulting friction factor can be a representative parameter for a constant cross section channel flow. In addition, the flow inside a rectangular channel with a high span to gap ratio can be approximated by flow inside parallel plates. The computational fluid dynamics simulation on the flow between parallel plates showed reasonable prediction capability for the laminar and the turbulent regime.

Effect of fuel assembly mechanical design changes on dynamic response of reactor pressure vessel system under extreme loadings

International Nuclear Information System (INIS)

Bhandari, D.R.; Hankinson, M.F.

1993-01-01

This paper presents the results of a study to assess the effect of fuel assembly mechanical design changes on the dynamic response of a pressurized water reactor vessel and reactor internals under Loss-Of-Coolant Accident (LOCA) conditions. The results of this study show that the dynamic response of the reactor vessel internals and the core under extreme loadings, such as LOCA, is very sensitive to fuel assembly mechanical design changes. (author)

Analysis of blood pressure dynamics in male and female rats using the continuous wavelet transform

International Nuclear Information System (INIS)

Pavlov, A N; Anisimov, A A; Matasova, E G; Semyachkina-Glushkovskaya, O V; Kurths, J

2009-01-01

We study gender-related particularities in cardiovascular responses to stress and nitric oxide (NO) deficiency in rats using HR, mean arterial pressure (MAP) and a proposed wavelet-based approach. Blood pressure dynamics is analyzed: (1) under control conditions, (2) during immobilization stress and recovery and (3) during nitric oxide blockade by N G -nitro-L-arginine-methyl ester (L-NAME). We show that cardiovascular sensitivity to stress and NO deficiency depends upon gender. Actually, in females the chronotropic effect of stress is more pronounced, while the pressor effect is weakened compared with males. We conclude that females demonstrate more favorable patterns of cardiovascular responses to stress and more effective NO control of cardiovascular activity than males

Effect of pressure on transport properties of CeIrIn5

International Nuclear Information System (INIS)

Takaesu, Y; Aso, N; Tamaki, Y; Hedo, M; Nakama, T; Uchima, K; Ishikawa, Y; Deguchi, K; Sato, N K

2011-01-01

Electrical resistivity ρ and thermoelectric power S of a heavy-fermion superconductor CeIrIn 5 have been measured at temperatures from 2.0 K to 300 K under hydrostatic pressures up to 2.2 GPa. The thermoelectric power S exhibits a large positive value up to 90 μV/K, which is characteristic of heavy-fermion systems. S also shows a sharp maximum in its temperature dependence and its maximum temperature T s,max increases with pressure, while its maximum value is constant independent of pressure. These experimental results strongly indicate that the Kondo temperature of CeIrIn 5 increases by applying the pressure.

Hemodynamic mechanisms of the attenuated blood pressure response to mental stress after a single bout of maximal dynamic exercise in healthy subjects

Directory of Open Access Journals (Sweden)

F.J. Neves

2012-07-01

Full Text Available To determine the hemodynamic mechanisms responsible for the attenuated blood pressure response to mental stress after exercise, 26 healthy sedentary individuals (age 29 ± 8 years underwent the Stroop color-word test before and 60 min after a bout of maximal dynamic exercise on a treadmill. A subgroup (N = 11 underwent a time-control experiment without exercise. Blood pressure was continuously and noninvasively recorded by infrared finger photoplethysmography. Stroke volume was derived from pressure signals, and cardiac output and peripheral vascular resistance were calculated. Perceived mental stress scores were comparable between mental stress tests both in the exercise (P = 0.96 and control (P = 0.24 experiments. After exercise, the blood pressure response to mental stress was attenuated (pre: 10 ± 13 vs post: 6 ± 7 mmHg; P 0.05. In conclusion, a single bout of maximal dynamic exercise attenuates the blood pressure response to mental stress in healthy subjects, along with lower stroke volume and cardiac output, denoting an acute modulatory action of exercise on the central hemodynamic response to mental stress.

Atmospheric pressure plasma jets : properties of plasma bullets and the dynamics of the interaction with dielectric surfaces

NARCIS (Netherlands)

Sobota, A.; Slikboer, E.; Guaitella, O.Y.N.

2015-01-01

Cold atmospheric pressure plasma jets, although mostly researched for applications in surface treatment, are rarely investigated in the presence of a surface. This paper presents the properties of plasma bullets formed in the capillary as well as the dynamics of the propagation of the plasma on

Synthesis of microparticles with complex compositions in a xenon high-pressure chamber (550 bar) under irradiation by braking radiation with a maximum energy of 10 MeV

International Nuclear Information System (INIS)

Didyk, A.Yu.; Gul'bekyan, G.G.; Myshinskiy, G.V.; Sabel'nikov, A.V.

2016-01-01

Natural xenon at a pressure of 550 bar in a high pressure chamber (XeHPC) was irradiated during 2,59 · 10 5 s by bremsstrahlung with a maximum energy of 10 MeV at the electron accelerator MT-25 microtron with an electron beam intensity of 20–22μA. The final electron fluence was 4.74 · 10 19 electrons. The growth of pressure versus temperature during the stationary exposure mode grew at first up to 620 bar and then dropped to 550 bar. After opening of the XeHPC both of the internal chambers with all the structures, but without gas, were measured using a γ-germanium detector (Canberra) during 15 h each for measurement of the background and short-lived isotopes. During a visual inspection of the interior surfaces of the XeHPC inner assembly, a visible coating of substantial thickness and greenish-yellowish color was observed. The research carried out by scanning electron microscopy (SEM) and X-ray micro-probe analysis (XMPA) allowed us to determine the elemental composition of synthesized particles. [ru

Nonlinear response of a post-tensioned concrete structure to static and dynamic internal-pressure loads

International Nuclear Information System (INIS)

Butler, T.A.; Bennett, J.G.

1981-01-01

A nonlinear finite element model of a nuclear power plant containment building was developed to determine its ultimate pressure capability under quasistatic and impulsive dynamic loads. The ADINA finite element computer code was used to develop the model because of its capability to handle concrete cracking and crushing. Results indicate that, even though excessive concrete cracking occurs, failure is ultimately caused by rupture of post-tensioning tendons

An implementation of the maximum-caliber principle by replica-averaged time-resolved restrained simulations.

Science.gov (United States)

Capelli, Riccardo; Tiana, Guido; Camilloni, Carlo

2018-05-14

Inferential methods can be used to integrate experimental informations and molecular simulations. The maximum entropy principle provides a framework for using equilibrium experimental data, and it has been shown that replica-averaged simulations, restrained using a static potential, are a practical and powerful implementation of such a principle. Here we show that replica-averaged simulations restrained using a time-dependent potential are equivalent to the principle of maximum caliber, the dynamic version of the principle of maximum entropy, and thus may allow us to integrate time-resolved data in molecular dynamics simulations. We provide an analytical proof of the equivalence as well as a computational validation making use of simple models and synthetic data. Some limitations and possible solutions are also discussed.

Dynamics of particle loading in deep-bed filter. Transport, deposition and reentrainment

Directory of Open Access Journals (Sweden)

Przekop Rafał

2016-09-01

Full Text Available Deep bed filtration is an effective method of submicron and micron particle removal from the fluid stream. There is an extensive body of literature regarding particle deposition in filters, often using the classical continuum approach. However, the approach is not convenient for studying the influence of particle deposition on filter performance (filtration efficiency, pressure drop when non-steady state boundary conditions have to be introduced. For the purposes of this work the lattice-Boltzmann model describes fluid dynamics, while the solid particle motion is modeled by the Brownian dynamics. For aggregates the effect of their structure on displacement is taken into account. The possibility of particles rebound from the surface of collector or reentrainment of deposits to fluid stream is calculated by energy balanced oscillatory model derived from adhesion theory. The results show the evolution of filtration efficiency and pressure drop of filters with different internal structure described by the size of pores. The size of resuspended aggregates and volume distribution of deposits in filter were also analyzed. The model enables prediction of dynamic filter behavior. It can be a very useful tool for designing filter structures which optimize maximum lifetime with the acceptable values of filtration efficiency and pressure drop.

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

Directory of Open Access Journals (Sweden)

D. K. Sengupta

2013-01-01

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

On the Validity of Continuum Computational Fluid Dynamics Approach Under Very Low-Pressure Plasma Spray Conditions

Science.gov (United States)

Ivchenko, Dmitrii; Zhang, Tao; Mariaux, Gilles; Vardelle, Armelle; Goutier, Simon; Itina, Tatiana E.

2018-01-01

Plasma spray physical vapor deposition aims to substantially evaporate powders in order to produce coatings with various microstructures. This is achieved by powder vapor condensation onto the substrate and/or by deposition of fine melted powder particles and nanoclusters. The deposition process typically operates at pressures ranging between 10 and 200 Pa. In addition to the experimental works, numerical simulations are performed to better understand the process and optimize the experimental conditions. However, the combination of high temperatures and low pressure with shock waves initiated by supersonic expansion of the hot gas in the low-pressure medium makes doubtful the applicability of the continuum approach for the simulation of such a process. This work investigates (1) effects of the pressure dependence of thermodynamic and transport properties on computational fluid dynamics (CFD) predictions and (2) the validity of the continuum approach for thermal plasma flow simulation under very low-pressure conditions. The study compares the flow fields predicted with a continuum approach using CFD software with those obtained by a kinetic-based approach using a direct simulation Monte Carlo method (DSMC). It also shows how the presence of high gradients can contribute to prediction errors for typical PS-PVD conditions.

Sloshing of water in torus pressure-suppression pool of boiling water reactors under earthquake ground motions

International Nuclear Information System (INIS)

Aslam, M.; Godden, W.G.; Scalise, D.T.

1978-08-01

This report presents an analytical and experimental investigation into the sloshing of water in torus tanks under horizontal earthquake ground motions. This study was motivated because of the use of torus tanks for pressure-suppression pools in Boiling Water Reactors. Such a pressure-suppression pool would typically have 80 ft and 140 ft inside and outside diameters, a 30 ft diameter section, and a water depth of 15 ft. A general finite element analysis was developed for all axisymmetric tanks and a computer program was written to obtain time-history plots of sloshing displacements of water and dynamic pressures. Tests were carried out on a 1/60th scale model under sinusoidal as well as simulated earthquake ground motions. Tests and analytical results regarding natural frequencies, surface water displacements, and dynamic pressures were compared and a good agreement was found within the range of displacements studied. The computer program gave satisfactory results within a maximum range of sloshing displacements in the full-size prototype of 30 in. which is greater than the value obtained under the full intensity of the El Centro earthquake (N-S component 1940). The range of linear behavior was studied experimentally by subjecting the torus model to increasing intensities of the El Centro earthquake

Max Launch Abort System (MLAS) Pad Abort Test Vehicle (PATV) II Attitude Control System (ACS) Integration and Pressurization Subsystem Dynamic Random Vibration Analysis

Science.gov (United States)

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.

Research on axial total pressure distributions of sonic steam jet in subcooled water

International Nuclear Information System (INIS)

Wu Xinzhuang; Li Wenjun; Yan Junjie

2012-01-01

The axial total pressure distributions of sonic steam jet in subcooled water were experimentally investigated for three different nozzle diameters (6.0 mm, 8.0 mm and 10.0 mm). The inlet steam pressure, and pool subcooling subcooled water temperature were in the range of 0.2-0.6 MPa and 420-860 ℃, respectively. The effect of steam pressure, subcooling water temperature and nozzle size on the axial pressure distributions were obtained, and also the characteristics of the maximum pressure and its position were studied. The results indicated that the characteristics of the maximum pressure were influenced by the nozzle size for low steam pressure, but the influence could be ignored for high steam pressure. Moreover, a correlation was given to correlate the position of the maximum pressure based on steam pressure and subcooling water temperature, and the discrepancies of predictions and experiments are within ±15%. (authors)

Dynamic target high pressure control of a VRF system for heating energy savings

International Nuclear Information System (INIS)

Yun, Geun Young; Lee, Je Hyeon; Kim, Inhan

2017-01-01

Highlights: • We developed the dynamic target high pressure control of a VRF system. • We created the VRF control model using the EnergyPlus runtime language. • Multicalorimeter experimental results indicate that the energy efficiency improved by 21%. • EnergyPlus simulations demonstrate that the annual heating energy consumption was lowered by 22%. - Abstract: Variable refrigerant flow (VRF) systems are widely used because of their ability to provide individualized comfort control with energy-saving potential. This study develops load responsive high pressure control of a VRF system with the aim of reducing the heating energy consumption of a VRF system under part load conditions. The developed control consists of two parts: one part that determines the level of heating load, and the other that assigns a target high pressure based on the level of heating load. In this way, the compressor speed can be accurately matched to heating load, which improves the energy performance of the VRF system. A series of multicalorimeter experiments revealed that the heating capacity of the VRF system varied by 45% by modulating the target high pressure and that its efficiency was enhanced by 21% by changing the high pressure from 30 kgf/cm"2 to 25 kgf/cm"2. To evaluate the annual heating energy performance of the VRF system with the developed control, a custom computer code was developed to implement the developed control using a programming language called EnergyPlus Runtime Language. Simulation outcomes showed that the annual heating energy consumption of a medium-size office building was reduced by 22% when the developed control was applied.

Maximum overpressure in gastight containers of the storage and transport of dangerous liquids

International Nuclear Information System (INIS)

Steen, H.

1977-11-01

For a design of containers suitable under safety aspects for the transport and storage of dangerous liquids the maximum overpressure to be expected is an important value. The fundamentals for the determination of the internal pressure are pointed out for the simplified model of a rigid (i.e. not elastically or plastically deforming) and gastight container. By assuming of extreme storage and transport conditions (e.g. for the maximum liquid temperatures due to sun radiation) the figures of the maximum overpressure are calculated for about hundred liquids being of practical interest. The results show a significant influence of the compression of air in the ullage space caused by liquid expansion due to temperature rise (compression effect), particularly for liquids with a higher boiling point. The influence of the solubility of air in the liquid on the internal pressure can be neglected under the assumed transport conditions. The estimation of the volume increase of the container due to the effect of the internal pressure leads to the limitation, that the assumption of a rigid container is only justified for cylindrical and spherical steel tanks. The enlargement of the container volume due to a heating of the container shell does play no significant roll for all metal containers under the assumed conditions of storage and transport. The results obtained bear out essentially the stipulations for the test pressure and the filling limits laid down in the older German regulations for the transport of dangerous liquids in rail tank waggons and road tank vehicles without pressure relief valves. For the recently fixed and internationally harmonized regulations for tankcontainers the considerations and the results pointed out in this paper give rise to a review. (orig.) [de

Spectral calculations for pressure-velocity and pressure-strain correlations in homogeneous shear turbulence

Science.gov (United States)

Dutta, Kishore

2018-02-01

Theoretical analyses of pressure related turbulent statistics are vital for a reliable and accurate modeling of turbulence. In the inertial subrange of turbulent shear flow, pressure-velocity and pressure-strain correlations are affected by anisotropy imposed at large scales. Recently, Tsuji and Kaneda (2012 J. Fluid Mech. 694 50) performed a set of experiments on homogeneous shear flow, and estimated various one-dimensional pressure related spectra and the associated non-dimensional universal numbers. Here, starting from the governing Navier-Stokes dynamics for the fluctuating velocity field and assuming the anisotropy at inertial scales as a weak perturbation of an otherwise isotropic dynamics, we analytically derive the form of the pressure-velocity and pressure-strain correlations. The associated universal numbers are calculated using the well-known renormalization-group results, and are compared with the experimental estimates of Tsuji and Kaneda. Approximations involved in the perturbative calculations are discussed.

Appropriateness of dynamical systems for the comparison of different embedding methods via calculation of the maximum Lyapunov exponent

International Nuclear Information System (INIS)

Franchi, M; Ricci, L

2014-01-01

The embedding of time series provides a valuable, and sometimes indispensable, tool in order to analyze the dynamical properties of a chaotic system. To this purpose, the choice of the embedding dimension and lag is decisive. The scientific literature describes several methods for selecting the most appropriate parameter pairs. Unfortunately, no conclusive criterion to decide which method – and thus which embedding pair – is the best has been so far devised. A widely employed quantity to compare different methods is the maximum Lyapunov exponent (MLE) because, for chaotic systems that have explicit analytic representations, MLE can be numerically evaluated independently of the embedding dimension and lag. Within this framework, we investigated the dependence on the calculated MLE on the embedding dimension and lag in the case of three dynamical systems that are also widespreadly used as reference systems, namely the Lorenz, Rössler and Mackey-Glass attractors. By also taking into account the statistical fluctuations of the calculated MLE, we propose a new method to assess which systems provide suitable test benches for the comparison of different embedding methods via MLE calculation. For example we found that, despite of its popularity in this scientific context, the Rössler attractor is not a reliable workbench to test the validity of an embedding method

Pressure effects on martensitic transformation under quenching process in a molecular dynamics model of NiAl alloy

International Nuclear Information System (INIS)

Kazanc, S.; Ozgen, S.; Adiguzel, O.

2003-01-01

The solid-solid phase transitions in NiAl alloys occur by the temperature changes and application of a pressure on the system. Both types of transitions are called martensitic transformation and have displacive and thermoelastic characters. Pressure effects on thermoelastic transformation in Ni 62.5 Al 37.5 alloy model have been studied by means of molecular dynamics method proposed by Parrinello-Rahman. Interaction forces between atoms in the model system were calculated by Lennard-Jones potential energy function. Thermodynamics and structural analysis of the martensitic transformations under hydrostatic pressure during the quenching processes have been performed. The simulation runs have been carried out in different hydrostatic pressures changing from zero to 40.65 GPa during the quenching process of the model alloy. At the zero and nonzero pressures, the system with B2-type ordered structure undergoes the product phase with L1 0 -type ordered structure by Bain distortion in the first step of martensitic transformation under the quenching process. The increase in hydrostatic pressure causes decrease in the formation time of the product phase, and twin-like lattice distortion is observed in low temperature L1 0 phase

Molecular Dynamics of Equilibrium and Pressure-Driven Transport Properties of Water through LTA-Type Zeolites

KAUST Repository

Turgman-Cohen, Salomon; Araque, Juan C.; Hoek, Eric M. V.; Escobedo, Fernando A.

2013-01-01

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.

Molecular Dynamics of Equilibrium and Pressure-Driven Transport Properties of Water through LTA-Type Zeolites

KAUST Repository

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.

Cardiac supporting device using artificial rubber muscle: preliminary study to active dynamic cardiomyoplasty.

Science.gov (United States)

Saito, Yoshiaki; Suzuki, Yasuyuki; Goto, Takeshi; Daitoku, Kazuyuki; Minakawa, Masahito; Fukuda, Ikuo

2015-12-01

Dynamic cardiomyoplasty is a surgical treatment that utilizes the patient's skeletal muscle to support circulation. To overcome the limitations of autologous skeletal muscles in dynamic cardiomyoplasty, we studied the use of a wrapped-type cardiac supporting device using pneumatic muscles. Four straight rubber muscles (Fluidic Muscle, FESTO, Esslingen, Germany) were used and connected to pressure sensors, solenoid valves, a controller and an air compressor. The driving force was compressed air. A proportional-integral-derivative system was employed to control the device movement. An overflow-type mock circulation system was used to analyze the power and the controllability of this new device. The device worked powerfully with pumped flow against afterload of 88 mmHg, and the beating rate and contraction/dilatation time were properly controlled using simple software. Maximum pressure inside the ventricle and maximum output were 187 mmHg and 546.5 ml/min, respectively, in the setting of 50 beats per minute, a contraction/dilatation ratio of 1:2, a preload of 18 mmHg, and an afterload of 88 mmHg. By changing proportional gain, contraction speed could be modulated. This study showed the efficacy and feasibility of a pneumatic muscle for use in a cardiac supporting device.

Measurement correction method for force sensor used in dynamic pressure calibration based on artificial neural network optimized by genetic algorithm

Science.gov (United States)

Gu, Tingwei; Kong, Deren; Shang, Fei; Chen, Jing

2017-12-01

We present an optimization algorithm to obtain low-uncertainty dynamic pressure measurements from a force-transducer-based device. In this paper, the advantages and disadvantages of the methods that are commonly used to measure the propellant powder gas pressure, the applicable scope of dynamic pressure calibration devices, and the shortcomings of the traditional comparison calibration method based on the drop-weight device are firstly analysed in detail. Then, a dynamic calibration method for measuring pressure using a force sensor based on a drop-weight device is introduced. This method can effectively save time when many pressure sensors are calibrated simultaneously and extend the life of expensive reference sensors. However, the force sensor is installed between the drop-weight and the hammerhead by transition pieces through the connection mode of bolt fastening, which causes adverse effects such as additional pretightening and inertia forces. To solve these effects, the influence mechanisms of the pretightening force, the inertia force and other influence factors on the force measurement are theoretically analysed. Then a measurement correction method for the force measurement is proposed based on an artificial neural network optimized by a genetic algorithm. The training and testing data sets are obtained from calibration tests, and the selection criteria for the key parameters of the correction model is discussed. The evaluation results for the test data show that the correction model can effectively improve the force measurement accuracy of the force sensor. Compared with the traditional high-accuracy comparison calibration method, the percentage difference of the impact-force-based measurement is less than 0.6% and the relative uncertainty of the corrected force value is 1.95%, which can meet the requirements of engineering applications.

Power converter with maximum power point tracking MPPT for small wind-electric pumping systems

International Nuclear Information System (INIS)

Lara, David; Merino, Gabriel; Salazar, Lautaro

2015-01-01

Highlights: • We implement a wind electric pumping system of small power. • The power converter allowed to change the operating point of the electro pump. • Two control techniques were implemented in the power converter. • The control V/f variable allowed to increase the power generated by the permanent magnet generator. - Abstract: In this work, an AC–DC–AC direct-drive power converter was implemented for a wind electric pumping system consisting of a permanent magnet generator (PMG) of 1.3 kW and a peripheral single phase pump of 0.74 kW. In addition, the inverter linear V/f control scheme and the maximum power point tracking (MPPT) algorithm with variable V/f were developed. MPPT algorithm seeks to extract water in a wide range of power input using the maximum amount of wind power available. Experimental trials at different pump pressures were conducted. With a MPPT tracking system with variable V/f, a power value of 1.3 kW was obtained at a speed of 350 rpm and a maximum operating hydraulic head of 50 m. At lower operating heads pressures (between 10 and 40 m), variable V/f control increases the power generated by the PMG compared to the linear V/f control. This increase ranged between 4% and 23% depending on the operating pressure, with an average of 13%, getting close to the maximum electrical power curve of the PMG. The pump was driven at variable frequency reaching a minimum speed of 0.5 times the rated speed. Efficiency of the power converter ranges between 70% and 95% with a power factor between 0.4 and 0.85, depending on the operating pressure

Polarization and Segregation through Conformity Pressure and Voluntary Migration: Simulation Analysis of Co-Evolutionary Dynamics

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Dai Zusai

2017-11-01

Full Text Available While conformity pressures people to assimilate in a community, an individual occasionally migrates among communities when the individual feels discomfort. These two factors cause segregation and cultural diversity within communities in the society. By embedding a migration dynamic into Kuran and Sandholm’s model (2008 of preference evolution, we build an agent-based model to see how the variance of preferences in the entire society quantitatively changes over time. We find from the Monte-Carlo simulations that, while preferences assimilate within a community, self-selected migrations enlarge the diversity of preferences over communities in the society. We further study how the arrival rate of migration opportunities and the degree of conformity pressures affect the variance of preferences.

Mechanically induced strong red emission in samarium ions doped piezoelectric semiconductor CaZnOS for dynamic pressure sensing and imaging

Science.gov (United States)

Wang, Wei; Peng, Dengfeng; Zhang, Hanlu; Yang, Xiaohong; Pan, Caofeng

2017-07-01

Piezoelectric semiconductor with optical, electrical and mechanical multifunctions has great potential applications in future optoelectronic devices. The rich properties and applications mainly encompass the intrinsic structures and their coupling effects. Here, we report that lanthanide ions doped piezoelectric semiconductor CaZnOS:Sm3+ showing strong red emission induced by dynamic mechanical stress. Under moderate mechanical load, the doped piezoelectric semiconductor exhibits strong visible red emission to the naked eyes even under the day light. A flexible dynamic pressure sensor device is fabricated based on the prepared CaZnOS:Sm3+ powders. The mechanical-induced emission properties of the device are investigated by the optical fiber spectrometer. The linear characteristic emissions are attributed to the 4G5/2→6H5/2 (566 nm), 4G5/2→6H7/2 (580-632 nm), 4G5/2→6H9/2 (653-673 nm) and 4G5/2→6H11/2 (712-735 nm) f-f transitions of Sm3+ ions. The integral emission intensity is proportional to the value of applied pressure. By using the linear relationship between integrated emission intensity and the dynamic pressure, the real-time pressure distribution is visualized and recorded. Our results highlight that the incorporation of lanthanide luminescent ions into piezoelectric semiconductors as smart materials could be applied into the flexible mechanical-optical sensor device without additional auxiliary power, which has great potential for promising applications such as mapping of personalized handwriting, smart display, and human machine interface.

[Dynamic changes of the relationships between economic growth and environmental pressure in Gansu Province: a structural decomposition analysis].

Science.gov (United States)

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.

On wall pressure fluctuations and their coupling with vortex dynamics in a separated–reattached turbulent flow over a blunt flat plate

International Nuclear Information System (INIS)

Tenaud, C.; Podvin, B.; Fraigneau, Y.; Daru, V.

2016-01-01

Highlights: • Study devoted to the compressible LES of the separated/reattached turbulent flow over a blunt flat plate with a right-angled leading edge. • Original contribution using a compressible approach to analyze main coherent structure features and their relation to the unsteady pressure field in the separated/reattached turbulent flow. • The present study provides a well resolved LES reference data-basis that is compared to incompressible results for validation. • It contributes to a better understanding of the coupling between the vortex dynamics and the wall pressure fluctuations, especially in connection with either the vortex shedding or the low frequency shear-layer flapping. - Abstract: This study deals with the numerical predictions through Large-Eddy Simulation (LES) of the separated–reattached turbulent flow over a blunt flat plate for analyzing main coherent structure features and their relation to the unsteady pressure field. A compressible approach that inherently includes acoustic propagation is here followed to describe the relationship between pressure fluctuations and vortex dynamics around the separation bubble. The objective of the present work is then to contribute to a better understanding of the coupling between the vortex dynamics and the wall pressure fluctuations. The filtered compressible Navier–Stokes equations are then solved with a numerical method that follows a Lax–Wendroff approach to recover a high accuracy in both time and space. For validations, the present numerical results are compared to experimental measurements, coming from both the Pprime laboratory (Sicot el al., 2012) and the literature (Cherry et al., 1984; Kiya and Sasaki, 1985; Tafti and Vanka,1991; Sicot et al., 2012). Our numerical results very well predict mean and fluctuating pressure and velocity fields. Flapping, shedding as well as Kelvin–Helmholtz characteristic frequencies educed by present simulations are in very good agreement with the

Giant Overlap between the Magnetic and Superconducting Phases of CeAu_{2}Si_{2} under Pressure

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Z. Ren

2014-09-01

Full Text Available High pressure provides a powerful means for exploring unconventional superconductivity which appears mostly on the border of magnetism. Here, we report the discovery of pressure-induced heavy-fermion superconductivity up to 2.5 K in the antiferromanget CeAu_{2}Si_{2} (T_{N}≈10  K. Remarkably, the magnetic and superconducting phases are found to overlap across an unprecedentedly wide pressure interval from 11.8 to 22.3 GPa. Moreover, both the bulk T_{c} and T_{M} are strongly enhanced when increasing the pressure from 16.7 to 20.2 GPa. T_{c} reaches a maximum at a pressure slightly below p_{c}≈22.5  GPa, at which magnetic order disappears. Furthermore, the scaling behavior of the resistivity provides evidence for a continuous delocalization of the Ce 4f electrons associated with a critical end point lying just above p_{c}. We show that the maximum T_{c} of CeAu_{2}Si_{2} actually occurs at almost the same unit-cell volume as that of CeCu_{2}Si_{2} and CeCu_{2}Ge_{2}, and when the Kondo and crystal-field splitting energies become comparable. Dynamical mean-filed theory calculations suggest that the peculiar behavior in pressurized CeAu_{2}Si_{2} might be related to its Ce-4f orbital occupancy. Our results not only provide a unique example of the interplay between superconductivity and magnetism, but also underline the role of orbital physics in understanding Ce-based heavy-fermion systems.

The numerical simulation of the WWER-440/V-213 reactor pressure vessel internals response to maximum hypothetical large break loss of coolant accident

International Nuclear Information System (INIS)

Hermansky, P.; Krajcovic, M.

2012-01-01

The reactor internals are designed to ensure cooling of the fuel, to ensure the movement of emergency control assemblies under all operating conditions including accidents and facilitate removal of the fuel and of the internals following an accident This paper presents results of the numerical simulation of the WWER-440/V213 reactor vessel internals dynamic response to maximum hypothetical Large-Break Loss of Coolant Accident. The purpose of this analysis is to determine the reactor vessel internals response due to rapid depressurization and to prove no such deformations occur in the reactor vessel internals which would prevent timely and proper activation of the emergency control assemblies. (Authors)

Coherent pulse interrogation system for fiber Bragg grating sensing of strain and pressure in dynamic extremes of materials.

Science.gov (United States)

Rodriguez, George; Jaime, Marcelo; Balakirev, Fedor; Mielke, Chuck H; Azad, Abul; Marshall, Bruce; La Lone, Brandon M; Henson, Bryan; Smilowitz, Laura

2015-06-01

A 100 MHz fiber Bragg grating (FBG) interrogation system is described and applied to strain and pressure sensing. The approach relies on coherent pulse illumination of the FBG sensor with a broadband short pulse from a femtosecond modelocked erbium fiber laser. After interrogation of the FBG sensor, a long multi-kilometer run of single mode fiber is used for chromatic dispersion to temporally stretch the spectral components of the reflected pulse from the FBG sensor. Dynamic strain or pressure induced spectral shifts in the FBG sensor are detected as a pulsed time domain waveform shift after encoding by the chromatic dispersive line. Signals are recorded using a single 35 GHz photodetector and a 50 G Samples per second, 25 GHz bandwidth, digitizing oscilloscope. Application of this approach to high-speed strain sensing in magnetic materials in pulsed magnetic fields to ~150 T is demonstrated. The FBG wavelength shifts are used to study magnetic field driven magnetostriction effects in LaCoO3. A sub-microsecond temporal shift in the FBG sensor wavelength attached to the sample under first order phase change appears as a fractional length change (strain: ΔL/L-4) in the material. A second application used FBG sensing of pressure dynamics to nearly 2 GPa in the thermal ignition of the high explosive PBX-9501 is also demonstrated. Both applications demonstrate the use of this FBG interrogation system in dynamical extreme conditions that would otherwise not be possible using traditional FBG interrogation approaches that are deemed too slow to resolve such events.

Identification of dynamic basins in boiling fluxes

International Nuclear Information System (INIS)

Juanico, L.E.

1997-01-01

A theoretical and experimental study of the dynamic behavior of a boiling channel is presented. In particular, the existence of different basins of attraction during instabilities was established. A fully analytical treatment of boiling channel dynamics were performed using a algebraic delay model. Subcritical and supercritical Hopf bifurcations could be identified and analyzed using perturbation methods. The derivation of a fully analytical criterion for Hopf bifurcation transcription was applied to determine the amplitude of the limit cycles and the maximum allowed perturbations necessary to break the system stability. A lumped parameters model which allows the representation of flow reversal is presented. The dynamic of very large amplitude oscillations, out of the Hopf bifurcation domain, was studied. The analysis revealed the existence of new dynamical basins of attraction, where the system may evolve to and return from with hysteresis. Finally, an experimental study was conducted, in a water loop at atmospheric pressure, designed to reproduce the operating conditions analyzed in the theory. Different dynamic phase previously predicted in the theory were found and their nonlinear characteristics were studied. In particular, subcritical and supercritical Hopf bifurcations and very large amplitude oscillations with flow reversal were identified. (author). 53 refs., figs

Flashing evaporation under different pressure levels

International Nuclear Information System (INIS)

Liao, Yixiang; Lucas, Dirk; Krepper, Eckhard; Rzehak, Roland

2013-01-01

Highlights: • CFD simulation based on two-fluid model for flashing boiling inside a vertical pipe. • Effect of pressure level on the maximum thermal energy available for evaporation. • Effect of presumed bubble size on the onset of flashing as well as evaporation rate. • Effect of pressure level on the critical bubble size that can start stable flashing. • Effect of pressure level on nucleation rate and mechanism. - Abstract: Flashing evaporation of water inside a vertical pipe under four pressure levels is investigated both experimentally and numerically. In the experiment depressurization is realized through a blow-off valve, and the evaporation rate is controlled by the opening rate and degree of the valve. In the CFD simulation phase change is assumed to be caused by thermal heat transfer between steam–water interface and the surrounding water. Consequently, the evaporation rate is determined by heat transfer coefficient, interfacial area density as well as liquid superheat degree. The simulated temporal course of cross-section averaged steam volume fraction is compared with the measured one. It is found that the increasing rate and maximum value of steam volume fraction is over-predicted under low-pressure conditions, which is mainly caused by the neglect of bubble growth in the mono-dispersed simulation. The agreement is notably improved by performing poly-dispersed simulations with the inhomogeneous MUSIG approach (IMUSIG). On the other hand an underestimation of the maximum steam volume fraction is observed in high-pressure cases, since the contribution of nucleation to the total steam generation rate becomes large as the system pressure increases. Reliable models for nucleation rate as well as bubble detachment size are indispensable for reliable predictions. An effect of the system pressure level on the nucleation mechanism is observed in the experiment

Effect of water phase transition on dynamic ruptures with thermal pressurization: Numerical simulations with changes in physical properties of water

Science.gov (United States)

Urata, Yumi; Kuge, Keiko; Kase, Yuko

2015-02-01

Phase transitions of pore water have never been considered in dynamic rupture simulations with thermal pressurization (TP), although they may control TP. From numerical simulations of dynamic rupture propagation including TP, in the absence of any water phase transition process, we predict that frictional heating and TP are likely to change liquid pore water into supercritical water for a strike-slip fault under depth-dependent stress. This phase transition causes changes of a few orders of magnitude in viscosity, compressibility, and thermal expansion among physical properties of water, thus affecting the diffusion of pore pressure. Accordingly, we perform numerical simulations of dynamic ruptures with TP, considering physical properties that vary with the pressure and temperature of pore water on a fault. To observe the effects of the phase transition, we assume uniform initial stress and no fault-normal variations in fluid density and viscosity. The results suggest that the varying physical properties decrease the total slip in cases with high stress at depth and small shear zone thickness. When fault-normal variations in fluid density and viscosity are included in the diffusion equation, they activate TP much earlier than the phase transition. As a consequence, the total slip becomes greater than that in the case with constant physical properties, eradicating the phase transition effect. Varying physical properties do not affect the rupture velocity, irrespective of the fault-normal variations. Thus, the phase transition of pore water has little effect on dynamic ruptures. Fault-normal variations in fluid density and viscosity may play a more significant role.

Prediction of blood pressure and blood flow in stenosed renal arteries using CFD

Science.gov (United States)

Jhunjhunwala, Pooja; Padole, P. M.; Thombre, S. B.; Sane, Atul

2018-04-01

In the present work an attempt is made to develop a diagnostive tool for renal artery stenosis (RAS) which is inexpensive and in-vitro. To analyse the effects of increase in the degree of severity of stenosis on hypertension and blood flow, haemodynamic parameters are studied by performing numerical simulations. A total of 16 stenosed models with varying degree of stenosis severity from 0-97.11% are assessed numerically. Blood is modelled as a shear-thinning, non-Newtonian fluid using the Carreau model. Computational Fluid Dynamics (CFD) analysis is carried out to compute the values of flow parameters like maximum velocity and maximum pressure attained by blood due to stenosis under pulsatile flow. These values are further used to compute the increase in blood pressure and decrease in available blood flow to kidney. The computed available blood flow and secondary hypertension for varying extent of stenosis are mapped by curve fitting technique using MATLAB and a mathematical model is developed. Based on these mathematical models, a quantification tool is developed for tentative prediction of probable availability of blood flow to the kidney and severity of stenosis if secondary hypertension is known.

Prediction of flow- induced dynamic stress in an axial pump impeller using FEM

International Nuclear Information System (INIS)

Gao, J Y; Hou, Y S; Xi, S Z; Cai, Z H; Yao, P P; Shi, H L

2013-01-01

Axial pumps play an important role in water supply and flood control projects. Along with growing requirements for high reliability and large capacity, the dynamic stress of axial pumps has become a key problem. Unsteady flow is a significant reason which results structural dynamic stress of a pump. This paper reports on a flow-induced dynamic stress simulation in an axial pump impeller at three flow conditions by using FEM code. The pressure pulsation obtained from flow simulation using CFD code was set as the force boundary condition. The results show that the maximum stress of impeller appeared at joint between blade and root flange near trailing edge or joint between blade and root flange near leading edge. The dynamic stress of the two zones was investigated under three flow conditions (0.8Q d , 1.0Q d , 1.1Q d ) in time domain and frequency domain. The frequencies of stress at zones of maximum stress are 22.9Hz and 37.5Hz as the fundamental frequency and its harmonics. The fundamental frequencies are nearly equal to vane passing frequency (22.9 Hz) and 3 times blade passing frequency (37.5Hz). The first dominant frequency at zones of maximum stress is equal to the vane passing frequency due to rotor-stator interaction between the vane and the blade. This study would be helpful for axial pumps in reducing stress, improving structure design and fatigue life

Dynamic Cerebral Autoregulation Changes during Sub-Maximal Handgrip Maneuver

Science.gov (United States)

Nogueira, Ricardo C.; Bor-Seng-Shu, Edson; Santos, Marcelo R.; Negrão, Carlos E.; Teixeira, Manoel J.; Panerai, Ronney B.

2013-01-01

Purpose We investigated the effect of handgrip (HG) maneuver on time-varying estimates of dynamic cerebral autoregulation (CA) using the autoregressive moving average technique. Methods Twelve healthy subjects were recruited to perform HG maneuver during 3 minutes with 30% of maximum contraction force. Cerebral blood flow velocity, end-tidal CO2 pressure (PETCO2), and noninvasive arterial blood pressure (ABP) were continuously recorded during baseline, HG and recovery. Critical closing pressure (CrCP), resistance area-product (RAP), and time-varying autoregulation index (ARI) were obtained. Results PETCO2 did not show significant changes during HG maneuver. Whilst ABP increased continuously during the maneuver, to 27% above its baseline value, CBFV raised to a plateau approximately 15% above baseline. This was sustained by a parallel increase in RAP, suggestive of myogenic vasoconstriction, and a reduction in CrCP that could be associated with metabolic vasodilation. The time-varying ARI index dropped at the beginning and end of the maneuver (p<0.005), which could be related to corresponding alert reactions or to different time constants of the myogenic, metabolic and/or neurogenic mechanisms. Conclusion Changes in dynamic CA during HG suggest a complex interplay of regulatory mechanisms during static exercise that should be considered when assessing the determinants of cerebral blood flow and metabolism. PMID:23967113

Dynamic cerebral autoregulation changes during sub-maximal handgrip maneuver.

Directory of Open Access Journals (Sweden)

Ricardo C Nogueira